Dopant-Dependent Structure–Property Relationships in Functionalized Graphene and MWCNTs for Sustainable Energy Applications

Dopant-Dependent Structure–Property Relationships in Functionalized Graphene and MWCNTs for Sustainable Energy Applications | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Dopant-Dependent Structure–Property Relationships in Functionalized Graphene and MWCNTs for Sustainable Energy Applications Abdalrahman G. Al-Gamal, Walaa S. Gado, Muhammad A. Abo El-Khair, and 3 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-9182061/v1 This work is licensed under a CC BY 4.0 License Status: Under Revision Version 1 posted 9 You are reading this latest preprint version Abstract Tailoring the electronic and electrochemical properties of carbon nanomaterials through controlled chemical functionalization is critical for advancing next-generation energy and optoelectronic technologies. Herein, we present a systematic nanoscale engineering strategy based on halogen-functionalized graphene (fluorinated and brominated) integrated with lithium-modified multi-walled carbon nanotubes (MWCNTs). Graphene oxide (GO) was chemically modified using hydrofluoric acid (HF) and tetrabutylammonium bromide (TBAB) to produce fluorinated graphene (FG) and brominated graphene (G-TBAB), respectively, while MWCNTs were functionalized with lithium fluoride (LiF) to obtain Li-MWCNTs. This comparative platform establishes a unified dopant-dependent framework correlating electronegativity, bonding configuration, and interfacial nanoarchitecture with optoelectronic and electrochemical performance across distinct carbon allotropes. Comprehensive structural and chemical characterization (FTIR, XRD, XPS, SEM, TEM, AFM, UV–Vis, photoluminescence spectroscopy, and electrochemical impedance spectroscopy) reveals that covalent C–F bonding enhances charge transport and suppresses carrier recombination, yielding FG with the lowest charge-transfer resistance (2.54 Ω·cm⁻²) and improved conductivity. In contrast, bromine-mediated noncovalent functionalization via TBAB induces steric and electrostatic modulation of the graphene surface, enabling tunable photoluminescence while preserving the structural integrity of the carbon framework. Furthermore, lithium functionalization of MWCNTs promotes efficient ion diffusion and interfacial charge storage, thereby enhancing capacitance and exhibiting pronounced Warburg behavior characteristic of diffusion-controlled electrochemical processes. By directly linking dopant chemistry to nanoscale interfacial phenomena and functional performance, this work introduces a dopant-selective materials design strategy for tailoring carbon nanomaterials toward photovoltaic, optoelectronic, and energy storage applications. Physical sciences/Chemistry Physical sciences/Energy science and technology Physical sciences/Materials science Physical sciences/Nanoscience and technology Graphene Halogen doping Lithium-functionalized MWCNTs Optical properties Electrochemical impedance spectroscopy Photoluminescence Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 1. Introduction Graphene, a two-dimensional monolayer of sp²-hybridized carbon atoms arranged in a honeycomb lattice, has revolutionized materials science since its isolation 1 , 2 . Its extraordinary properties-including ultra-high electron mobility (> 200,000 cm² V⁻¹ s⁻¹), exceptional thermal conductivity, superior mechanical strength, and vast specific surface area-have positioned it as a cornerstone material for next-generation technologies in electronics, photonics, sensing, and energy conversion 3 . However, the absence of an intrinsic bandgap in pristine, defect-free graphene fundamentally limits its direct application in logic devices and certain optoelectronic systems that require a well-defined on/off switching behavior 4 . To address this limitation, extensive research efforts have focused on engineering graphene's electronic structure. Among the various approaches, chemical doping has emerged as a highly effective and versatile strategy to precisely modulate graphene's electrical conductivity, optical absorption, and surface reactivity 5 . The introduction of heteroatoms or functional groups enables Fermi level tuning, bandgap opening, and improves interfacial compatibility, thereby tailoring graphene for specific applications. Halogen doping, leveraging the high electronegativity and distinct bonding characteristics of elements such as fluorine and bromine, has attracted significant attention for inducing controllable electronic and optical modifications in graphene 6 . Fluorine, owing to its small atomic radius and extreme electronegativity, induces strong electron-withdrawing effects upon covalent bonding with carbon. This interaction locally transforms sp² to sp³ hybridization, resulting in lattice distortion, bandgap opening, and, in many cases, enhanced photoluminescence (PL) 7 . In contrast, bromine doping predominantly introduces p -type behavior through charge-transfer interactions, while largely preserving the metallic nature of the graphene basal plane due to bromine’s lower electronegativity and larger van der Waals radius 8 . This fundamental contrast provides a powerful framework for rationally designing graphene derivatives with tunable electronic and optical properties via selective halogen functionalization. In parallel with graphene research, carbon nanotubes (CNTs), particularly multi-walled carbon nanotubes (MWCNTs), have been extensively studied for their outstanding one-dimensional electrical conductivity, mechanical robustness, and high aspect ratio 9 . Moreover, functionalization of MWCNTs with alkali metals, particularly lithium, markedly augments their electrochemical performance by introducing additional charge carriers and modifying surface energetics. Lithium-functionalized MWCNTs (Li-MWCNTs) have demonstrated significant promise as high-capacity anode materials for lithium-ion batteries and as conductive additives in supercapacitors, owing to improved ion intercalation kinetics and charge storage capacity 10 , 11 . Recent advances in composite solid electrolytes, such as dynamic crosslinked metal-organic framework/poly(ionic liquid) networks, highlight the critical importance of engineered interfaces and optimized ionic transport pathways in next-generation battery technologies 12 . This principle is equally applicable to the design of functionalized carbon electrodes. Despite notable progress in halogen-doped graphene and Li-functionalized CNTs individually, systematic studies exploring their combined effects within an integrated hybrid framework remain limited. The rational design of such multifunctional heterostructures offers the potential to overcome the intrinsic limitations of individual components, yielding composite materials with tunable conductivity, engineered band gaps, enhanced interfacial interactions, and superior mechanical and thermal performance. The broader field of carbon-based hybrid materials has demonstrated the transformative impact of strategic material integration. For instance, heterostructures such as FeWO₄/g-C₃N₄ 13 and Z-scheme BiVO₄/g-C₃N₄/rGO 14 have achieved exceptional solar-driven photocatalytic activity through optimized interfacial charge transfer. Similarly, nanocomposites such as AgFeO₂/g-C₃N₄/RGO 15 and CuFe₂O₄/g-C₃N₄/rGO 16 combine photocatalytic activity with magnetic separability and antibacterial functionality for wastewater treatment. Multifunctional architectures such as rGO/g-C₃N₄/FeTiO₃ 17 and ZnFe₂O₄/g-C₃N₄/rGO 18 further illustrate how carbon-based platforms can deliver synergistic optoelectronic, catalytic, and biological performance. Collectively, these studies emphasize that the performance enhancement of carbon nanomaterials arises not only from doping but also from the deliberate creation of synergistic interfacial architectures. Motivated by these considerations, the present work aims to systematically elucidate the fundamental structure–property relationships in advanced carbon-based hybrids. We report a comprehensive study on the synthesis and characterization of halogen (F, Br)-doped graphene and lithium-decorated MWCNTs. A broad range of complementary spectroscopic, microscopic, and electrochemical techniques, including FTIR, XRD, XPS, SEM, TEM, AFM, UV-Vis, PL, and EIS, is employed to elucidate how specific chemical functionalization strategies influence the structural, morphological, optical, and electrical properties of the carbon framework. We hypothesize that controlled chemical doping enables precise tuning of material properties towards distinct sustainable and technological applications. Our results demonstrate that fluorinated graphene (FG) exhibits superior electrical conductivity, making it highly suitable for photovoltaic and electronic devices, while brominated graphene (G-TBAB) displays enhanced and tunable photoluminescence, favoring optoelectronics and sensing applications. In parallel, Li-MWCNTs exhibit optimized ion-storage capacity and diffusion kinetics, underscoring their potential for electrochemical energy storage systems. This study not only bridges an important knowledge gap regarding the combined effects of halogen and alkali metal functionalization in carbon nanostructures but also provides a rational materials design framework. The insights gained contribute to the development of high-performance, sustainable carbon-based materials for next-generation energy conversion and storage technologies, in alignment with the global clean energy objectives. 2. Experimental Section 2.1. Materials Graphite powder (Sigma-Aldrich, 99.99%), Tetrabutylammonium bromide (TBAB, Alfa Aesar, 99%), Hydrofluoric Acid (HF, 48%, Merck), Lithium Fluoride (LiF, Sigma-Aldrich, 99.99%). MWCNTs were supplied from the Egyptian Petroleum Research Institute (EPRI), these nanotubes have diameters ranging from 10 to 40 nm, lengths between 10 and 100 µm, and consist of approximately 40 to 50 walls. Ammonium hydroxide (NH 4 OH, 30%), sulfuric acid (H 2 SO 4 , 97%), Hydrochloric acid (HCl, 37%), Nitric acid (HNO 3 , 37%), hydrogen peroxide (H 2 O 2 , 10%), Ethanol, and Methanol were supplied from Honeywell Co. (USA). Indium tin oxide (ITO) (Sigma-Aldrich). Deionized water (18.2 MΩ·cm). All chemicals were used as received. 2.2. Synthesis of Graphene Oxide (GO) GO was synthesized from graphite powder using an improved Hummers' method [16]. Briefly, graphite (1 g) and NaNO 3 (0.5 g) were dispersed in 23 ml of concentrated H₂SO₄ under continuous stirring in an ice bath to maintain a temperature below 5°C. Subsequently, KMnO 4 (3 g) was added gradually to prevent overheating. The mixture was stirred at 35°C for 2 hours, during which the suspension turned a dark brown color. Afterward, 46 ml of deionized water was slowly added, followed by 10 ml of H₂O₂ to terminate the reaction. The resulting solution was filtered and washed sequentially with 5% HCl and deionized water until a neutral pH was achieved. The final graphene oxide was freeze-dried (lyophilized) to prevent aggregation and stored in a desiccator 10 . 2.3. Functionalization of Carbon Materials 2.3.1. Synthesis of Brominated Graphene (G-TBAB) A similar procedure involving the functionalization of graphene oxide (GO) with TBAB was employed to obtain noncovalently functionalized G-TBAB particles 2 . Briefly, (1 g) of GO was dispersed in 100 ml of distilled water (DI) and sonicated, followed by the gradual addition of (1 g) of TBAB. After 2 h of sonication, the resulting mixture was transferred to a Teflon-lined autoclave and heated at 200°C for 12 h. The suspension was then allowed to settle for 24 h and subsequently centrifuged to collect the G-TBAB. The collected product was thoroughly washed with deionized water until the filtrate became clear, ensuring the removal of residual impurities, and finally dried at 80°C. 2.3.2. Synthesis of Fluorinated Graphene (FG) The fluorinated graphene (FG) was synthesized via a hydrothermal approach. Briefly, (1 g) of GO was suspended in a mixed solution of HF (40 wt%) and deionized water at a volume ratio of 10:90, followed by ultrasonication for 1 min to ensure homogeneous dispersion. The resulting mixture was transferred to a Teflon-lined autoclave and heated at 180°C for 24 h. After naturally cooling to room temperature, the product was collected by filtration using a microporous membrane, thoroughly washed with ultrapure water to remove residual reactants, and freeze-dried to obtain FG 11 . 2.3.3. Synthesis of Lithium-Functionalized MWCNTs (Li-MWCNTs) Lithium-functionalized multi-walled carbon nanotubes (MWCNTs) were synthesized via a solvent-mediated method in a Teflon-lined reactor. Briefly, (0.5 g) of MWCNTs was dispersed in 100 ml of a 1 M LiF aqueous solution and magnetically stirred for 24 h to enable lithium incorporation. The resulting solid product was collected by vacuum filtration, repeatedly washed with deionized water to remove unreacted species and residual salts, and subsequently dried under vacuum at 100°C for 24 h 19 . 2.3.4. Fabrication of Thin Films for Electrical Measurements Thin films of each material (FG, G-TBAB, and Li-MWCNTs) were prepared by dispersing the powders in ethanol at a concentration of 1.0 mg/ml, followed by ultrasonication for 30 min to ensure homogeneous suspensions. Aliquots of 100 µl were drop-cast onto pre-cleaned ITO substrates (1×2 cm 2 ) and dried at 60°C to form uniform films. A gold counter electrode with a thickness of 50 nm was subsequently deposited by thermal evaporation through a shadow mask, yielding a two-electrode device configuration. 2.4. Electrochemical Impedance Spectroscopy (EIS) EIS measurements were performed using an Origalys (OrigaFlex 01A, potentiostat) in a two-electrode configuration, with the deposited film on ITO serving as working electrode and a gold (Au) as counter electrode. The impedance spectra were recorded over a frequency range of 100 kHz to 250 mHz with a 150 mV AC amplitude. The experimental data were fitted to an equivalent circuit model using Origalyx software to extract key electrochemical parameters, including film resistance (R f ), charge transfer resistance (R ct ), constant phase element (CPE), Warburg impedance (W), and the CPE exponent (n). All measurements were performed in triplicate (n = 3), and the reported values represent the mean ± standard deviation. The CPE exponent (n) provides insight into the electrochemical behavior of the system, with (n = 0) resistive behavior, (n = 1) inductive behavior, (n = -1) capacitive behavior, and (n = 0.5) Warburg impedance. 2.5. Material Characterization The synthesized materials were characterized using a comprehensive suite of analytical techniques. Fourier-transform infrared (FTIR) spectroscopy (PerkinElmer Spectrum One) was used to identify functional groups over the wavenumber range of 400–4000 cm − 1 . Crystal structures and phase composition were analyzed by X-ray diffraction (XRD, PANalytical X'Pert PRO) using Cu Kα radiation (λ = 1.5406 Å). Surface morphology and elemental composition were examined by Field-emission scanning electron microscopy (FESEM, JEOL JSM-6360), coupled with energy-dispersive X-ray spectroscopy (EDX). High-resolution transmission electron microscopy (HR-TEM, JEOL JEM-2100F) was used to examine particle size, morphology and internal structure. Surface topology was further analyzed by atomic force microscopy (AFM, Bruker Dimension Icon) in tapping mode. Optical properties were assessed using UV-Vis diffuse reflectance spectroscopy (JASCO V-770) to determine optical band gaps, while photoluminescence (PL) spectra were recorded using a JASCO FP-6500 spectrofluorometer with an excitation at 320 nm. X-ray photoelectron spectroscopy (XPS, Thermo Scientific K-Alpha) equipped with Al Kα source was utilized to analyze surface elemental composition and oxidation states. 3. Results and Discussion 3.1. Structural and Chemical Characterization 3.1.1. FTIR Analysis The FTIR spectrum of graphene functionalized with TBAB exhibits distinct characteristic peaks, confirming successful noncovalent functionalization. The main absorption bands associated with graphene oxide (GO) appear at 3734.20, 1699.78, and 1035.56 cm − 1 , corresponding to O–H stretching, C = O stretching, and C–O stretching vibrations, respectively. However, the intensities of these bands are markedly reduced compared to pristine GO, as shown in Fig. 1a and 1b 20 , indicating partial modification or masking of oxygen-containing functional groups upon TBAB incorporation. A broad absorption band at 3422.53 cm⁻¹ is assigned to N–H stretching vibrations, characteristic of amine functionalities, suggesting the presence of TBAB or related surface interactions 21 . The peak at 2966.68 cm⁻¹ represents C–H stretching vibrations, typical of aliphatic bonds and likely arising from the alkyl chains introduced by TBAB 22 . The band at 1551.67 cm − 1 is attributed to N–H bending vibrations, further supporting the presence of amine groups associated with TBAB 23 . In addition, the absorption band at 1175.11 cm − 1 is assigned to C–N stretching vibrations. The positively charged ammonium ion (R 4 N⁺) in TBAB can engage in electrostatic interactions with negatively charged oxygen-containing groups on GO, which likely contributes to the observed reduction in the intensities of epoxy, carboxyl, and hydroxyl-related peaks in the FTIR spectrum of the G-TBAB composite 24 . Collectively, these spectral features substantiate the successful attachment of TBAB onto the graphene surface through noncovalent interactions, as evidenced by the emergence of amine (N–H and C–N) vibrational modes and the attenuation of GO oxygenated functional-group signals. Figure 1 c presents the FTIR spectrum of FG, which exhibits characteristic absorption bands corresponding to C–O, C–F, C = C, C = O, and OH at 1035.56, 1209.01, 1541.74, 1705.95, and 3434.53 cm − 1 , respectively. The C–F stretching vibration, appearing in the range of 1200 and 1220 cm − 1 , is indicative of covalent bonding between fluorine atoms and sp³ -hybridized carbon sites 25 . Notably, the intensities of the C–O and C = O stretching vibrations in FG are stronger than those typically observed in graphite fluoride, with a particularly pronounced enhancement of the C–O band relative to C = O. This observation suggests that oxygen-containing functional groups in FG are predominantly incorporated in the form of C–O linkages 26 . The FTIR spectrum for Li-MWCNTs is shown in Fig. 1 d, displaying absorption bands at approximately 2973.76 and 2890.41 cm − 1 , which are attributed to C–H stretching vibrations. The bands observed near 1640.01 and 1540.07 cm − 1 correspond to the C = O and C = C stretching vibrations, respectively. A distinct absorption peak at around 642.89 cm − 1 is assigned to Li–O vibrations, indicating the formation of lithium-oxygen bonds following the doping process 27 . The relatively strong intensity of this band suggests substantial Li incorporation within the MWCNTs structure 19 . Additional absorption bands at 1401.70, 1134.62, and 3402.97 cm − 1 are attributed to C–O stretching, hydroxyl bending, and OH stretching vibrations of adsorbed water molecules, respectively, further confirming the successful functionalization of the material 28 . 3.1.2. X-ray Diffraction (XRD) Analysis XRD was employed to evaluate the crystallographic modifications induced by functionalization. Following the oxidation and exfoliation of graphite via sonication, GO was formed, exhibiting a characteristic diffraction peak to a low reflection angle of 10.78º, which is associated with the presence of oxygen-rich functional groups, as shown in Fig. 2 a. The XRD pattern of TBAB-functionalized GO (Fig. 2 b ) shows a pronounced structural transformation, evidenced by the disappearance of the characteristic peak at ~ 10°, corresponding to oxygenated functional groups (e.g., OH, C–O–C, and COOH). In contrast, a new diffraction peak appears at 24.8°, indexed to the (311) plane, indicating significant structural reorganization induced by TBAB functionalization 29 . As shown in Fig. 2 c, hydrothermal treatment of the GO dispersion with HF at 180°C for 30 h results in the disappearance of the GO peak at 10.8° and the emergence of a broad diffraction peak centered at approximately 24.7°, corresponding to an interlayer spacing of 0.52 nm. This shift indicates effective removal of oxygen-containing functional groups and the partial restoration of the graphene framework. Upon further addition of HF, the resulting fluorinated graphene exhibits an additional diffraction peak at approximately 15.1°, with an interlayer spacing of 0.72 nm. This peak, assigned to the (001) plane of a hexagonal lattice, reflects a high degree of fluorine incorporation within the graphene structure 11 , 30 . The XRD pattern of Li-functionalized MWCNTs (Fig. 2 d ) displays a prominent diffraction peak at 25.58°, corresponding to the (002) plane of MWCNTs, which is characteristic of the graphitic structure. Following LiF functionalization, additional diffraction peaks are observed at 17.1°, 36.2°, 43.2°, and 69.3°, which can be indexed to the characteristic reflections of LiF. The appearance of these peaks confirms the successful incorporation of LiF into the MWCNT framework and indicates enhanced crystallinity of the functionalized material 31 , 32 . 3.1.3. XPS Analysis XPS was conducted to investigate the surface composition and chemical states of Li-MWCNTs, G-TBAB, and FG. For Li-MWCNTs (Fig. 3 a ) , the survey spectrum confirms the presence of Li, C, and O. The high-resolution Li 1s spectrum exhibits two distinct peaks at approximately 52.5 eV and 55.0 eV, which are attributed to Li + species associated with Li–O bonding and more highly oxidized lithium environments, respectively. The O 1s spectrum displays three components at 530.5 eV (C = O), 531.4 eV (C–O), and 532.8 eV (O–C = O), indicating the presence of multiple oxygen-containing functional groups that facilitate lithium anchoring on the MWCNT surface 33 . The C 1s spectrum reveals characteristic peaks at 284.5 eV ( sp 2 C = C), 285.5 eV ( sp 3 C–C/C–H), 286.3 eV (C–O), and 290.5 eV (O–C = O), confirming preservation of the graphitic framework alongside surface functionalization 34 . For G-TBAB (Fig. 3 b ) , the survey spectrum confirms the presence of C, O, N, and Br, indicating successful incorporation of TBAB. The high-resolution C 1s spectrum shows peaks at 284.6 eV (C = C), 285.2 eV (C–N), 286.5 eV (C = O), and 288.3 eV (O–C = O), consistent with nitrogen-containing functional groups introduced during functionalization. The O 1s region exhibits components at 531.0 eV (C = O), 532.6 eV (C–O), and 536.4 eV (O–OH) 35 . The N 1s spectrum reveals contributions from pyrolytic, graphitic, and oxidized nitrogen species at binding energies of 399.8, 401.9, and 405.4 eV, respectively 36 . In addition, the Br 3d spectrum confirms bromine incorporation, displaying characteristic doublet peaks at 61.2 eV (3d 5/2 ) and 68.9 eV (3d 3/2 ), along with higher binding energy features. For FG (Fig. 3 c ) , the survey spectrum confirms the presence of C, O, N, and F. The O 1s spectrum exhibits peaks at 531.3 eV (C = O), 533.1 eV (C–O), and 535.6 eV (O–C = O). The N 1s spectrum shows four components at 395.5 eV (pyrrolic N), 398.6 eV (pyridinic N), 399.9 eV (aminic N), and 401.2 eV (graphitic N), indicating nitrogen incorporated in multiple chemical environments 22 . The high-resolution C 1s spectrum displays peaks at 284.4 eV ( sp 2 C = C), 284.9 eV ( sp 3 C–C), 285.8 eV (C–N/C–O), and 288.0 eV (C = O), confirming the structural integrity of the graphene lattice alongside the presence of oxygen- and nitrogen-containing functional groups 33 . 3.2. Morphological and Structural Analysis 3.2.1. Scanning electron microscopy (SEM) Scanning electron microscopy (SEM) revealed distinct morphological differences among the functionalized materials, as shown in Fig. 4 . The G-TBAB sample exhibits a flake-like morphology with reduced aggregation, which can be attributed to steric hindrance induced by tetrabutylammonium groups. In contrast, fluorinated graphene (FG) displays a more compact layered structure, consistent with increased structural rigidity resulting from fluorine incorporation. Li-MWCNTs retain their characteristic tubular morphology, with LiF crystallites uniformly distributed on the outer surfaces of the nanotubes. As shown in Fig. 4 a, G-TBAB exhibits a layered architecture interspersed with flake-like features, suggesting partial exfoliation and separation of graphene sheets. The presence of bulky tetrabutylammonium moieties likely inhibits restacking by introducing steric barriers between adjacent layers. EDX mapping further confirms successful functionalization through the detection of both nitrogen and bromine. The partially retained layered morphology may promote efficient electron transport pathways, enhancing the suitability of G-TBAB for electrochemical applications. The SEM images of Li-MWCNTs (Fig. 4 b ) reveal an interconnected network of entangled nanotubes with smooth surfaces, characteristic of MWCNT assemblies. The nanotubes appear as dense bundles, and no noticeable structural damage or fragmentation is observed, indicating that the functionalization process preserves the structural integrity of the MWCNTs. EDX mapping confirms the presence of carbon, oxygen, and fluorine. However, lithium is not detected due to its low atomic number and the inherent limitations of EDX in detecting light elements such as lithium. SEM analysis of FG (Fig. 4 c ) reveals a sheet-like morphology with well-defined flake characteristics, indicative of exfoliated graphene layers. EDX spectra confirm the presence of fluorine, providing direct evidence of successful fluorine doping within the graphene framework. 3.2.2. Transmission electron microscopy (TEM) TEM analysis reveals distinct structural features of graphene oxide (GO) and its functionalized derivatives. GO exhibit disordered, wrinkled, and folded sheet-like morphologies with an expanded interlayer spacing of approximately 0.84 nm, arising from the introduction of oxygen-containing functional groups that disrupt the planner sp 2 carbon lattice. In contrast, FG displays comparatively flatter and more rigid sheets with localized lattice distortion and a reduced interlayer spacing of approximately 0.36 nm, confirming partial fluorination without extensive structural damage. Similarly, G-TBAB presents well-dispersed flake-like structures with an interlayer spacing of ~ 0.36 nm, indicative of reduced aggregation and partial restoration of graphene stacking. Li-MWCNTs retain their characteristic tubular morphology, with localized surface roughness attributed to LiF incorporation, while preserving the integrity of the nanotube core structure without disrupting the core structure. Figure 5 presents high-resolution TEM (HR-TEM) images of GO and the functionalized carbon-based derivatives. As shown in Fig. 5 a and b , GO exhibits wrinkling and folding, accompanied by an amorphous region, resulting from the presence of hydroxyl, epoxy, and carboxyl groups. These oxygen functionalities expand the interlayer spacing to approximately 0.84 nm, compared to ~ 0.34 nm in pristine graphene, and introduce a high density of structural defects that disrupt the long-range sp² ordering. In Comparison, the HR-TEM images of FG (Fig. 5 c and d ), reveal a more ordered and layered morphology, reflecting enhanced structure rigidity induced by fluorine incorporation. The strong electronegativity of fluorine stabilizes the graphene layers and suppresses excessive curling. The observed lattice spacing of ~ 0.35–0.37 nm indicates low-to-moderate fluorine doping, accompanied by minor, localized defects, while largely preserving the graphene lattice. This controlled functionalization enhances thermal stability, chemical resistance, and surface energy, rendering FG attractive for applications such as supercapacitors and solid lubrication. The G-TBAB sample (Fig. 5 e and f ) exhibits a dispersed, flake-like morphology with significantly reduced aggregation. The interlayer spacing ~ 0.36 nm suggests partial recovery of the graphene framework following functionalization. The relatively uniform attachments of TBAB molecules contribute to improved dispersion and fewer large-scale defects. However, the noncovalent nature of TBAB-graphene interactions may result in weaker interfacial stability, potentially limiting long-term durability under harsh operating conditions. Finally, Li-MWCNTs (Fig. 5 g and h ) display a well-defined tubular morphology with concentric graphitic layers. The interlayer spacing remains approximately 0.34 nm, while the outer walls exhibit slight expansion due to LiF intercalation and surface interactions. Localized structural disorder appears near the doped region; however, the nanotube cores remain largely intact, preserving their intrinsic mechanical strength and electrical conductivity. This combination of structural integrity and localized lithium functionalization highlights the potential of Li-MWCNTs for advanced electrochemical energy storage and electronic applications. A comparative summary of the structural characteristics of GO and its functionalization derivatives, including surface morphology, interlayer spacing, defect density, and associated electronic properties, is provided in Table 1 . Table 1 HR-TEM features of GO, FG, G-TBAB, and Li-MWCNTs Feature GO FG G-TBAB Li-MWCNTs Morphology Wrinkled, disordered Rigid, layered Dispersed, flake-like Tubular, concentric Lattice Spacing (nm) ~ 0.84 ~ 0.35–0.37 ~ 0.36 ~ 0.34 (inner), ~ 0.36 (outer) Defects High (oxidation defects) Scattered (fluorine) Few-layered, fewer defects Localized (outer walls) Structural Integrity Disrupted Well-maintained Stable and well-dispersed Strong core, local defects Functional Impact Insulating Improved thermal stability Improved solubility Enhanced electrochemical properties 3.2.3. AFM characterizations Atomic force microscopy (AFM) images acquired over a scan area of 313 nm × 313 nm provide detailed insight into the surface morphology of GO and its chemically modified derivatives: FG, G-TBAB, and Li-MWCNTs. As shown in Fig. 6 a, GO exhibits a relatively smooth and homogeneous surface, with a narrow height distribution ranging from approximately − 1.02 nm to 1.6 nm. This low roughness is characteristic of GO and reflects its layered morphology, decorated with oxygen-containing functional groups that promote a relatively flat surface profile 37 . In contrast, FG (Fig. 6 b ) exhibits a pronounced increase in surface roughness, with height variations spanning from − 28.8 nm to 37.6 nm over the same scan area. This pronounced roughness indicates that fluorine functionalization introduces surface defects and enhances vertical irregularity, likely due to lattice distortion and local disruption of the graphene sheets. Such features may also arise from partial exfoliation and wrinkling induced during the fluorination process 37 , 38 . The AFM image of G-TBAB (Fig. 6 c) reveals a heterogeneous and irregular surface characterized by distinct protrusions and depressions, with height variation ranging from − 11.2 nm to 8.61 nm. This morphology can be attributed to the attachment of bulky tetrabutylammonium bromide moieties, which hinder graphene restacking and lead to uneven layer aggregation. The observed surface heterogeneity is consistent with previous reports on graphene functionalized with large organic cations 39 . Li-MWCNTs (Fig. 6 d) exhibit the most pronounced surface roughness among the investigated samples, with height variations ranging from − 53.2 nm to 52.8 nm. This extreme roughness reflects the inherent tubular morphology of MWCNTs combined with the effect of lithium fluoride incorporation, which introduces significant surface corrugation and structural deformation. The large vertical variations suggest strong interfacial interactions between LiF species and the carbon framework, resulting in a complex and highly textured surface topology 40 . Overall, AFM analysis confirms that chemical functionalization markedly alters the surface morphology of GO-derived materials. GO exhibits the smoothest and most uniform surface, whereas FG displays enhanced roughness due to fluorine-induced lattice disruption. G-TBAB shows moderate roughness associated with bulky organic functional groups, while Li-MWCNTs demonstrate the highest surface roughness owing to the combined effect of nanotube architecture and LiF doping. A quantitative summary of AFM-derived surface roughness parameters and morphological characteristics is provided in Table 2 . Table 2 AFM features for GO, FG, G-TBAB, and Li-MWCNTs. Parameter GO FG G-TBAB Li-MWCNTs Surface morphology Smooth and homogeneous Rough with increased irregularities Moderately rough with protrusions Highly irregular with prominent surface features Height range (nm) -1.02 to 1.6 -28.8 to 37.6 -11.2 to 8.61 -53.2 to 52.8 Surface roughness Low High Moderate Very High Structural characteristics A layered structure with oxygen groups Disrupted surface due to fluorine attachment Irregular surface due to bulky organic groups Tubular structures causing large corrugations Surface texture Flat and uniform Wrinkled with sharp peaks and valleys Rough with small bumps Complex topology with deep pits and peaks Notable features Smoothest surface Sharp peaks and more profound valleys Distinct protrusions and irregularity Most dramatic roughness and tubular patterns 3.3. Optical Properties 3.3.1. UV-Vis Spectroscopy The UV-Vis diffuse reflectance spectra (Fig. 7 a) exhibit a characteristic π–π* electronic transition for all samples in the wavelength range of 236–239 nm, indicative of the conjugated carbon framework. Corresponding Tauc plots (Fig. 7 b) were constructed to estimate the optical band gaps (Eg), yielding values of 2.83 eV for GO, 3.30 eV for Li-MWCNTs, 3.51 eV for FG, and 3.72 eV for G-TBAB. The systematic increase in Eg following functionalization, particularly upon halogen incorporation, confirms effective modulation of the electronic structure through chemical doping. Such band gap widening is expected to influence charge-carrier dynamics and enables tunability of light-harvesting behavior, which is advantageous for optoelectronic and photocatalytic applications 41 . Comparable trends in band-gap enlargement have been reported for other doped carbon-based composite materials engineered for enhanced photocatalytic performance 12 – 15 . 3.3.2. Photoluminescence (PL) Spectroscopy The photoluminescence (PL) spectra (Fig. 8 ) exhibit a prominent emission band centered at approximately 498 nm for GO, Li-MWCNTs, and FG, which is commonly attributed to the charge recombination process associated with C–C and C–O electronic states. In contrast, G-TBAB displays a slight red shift to ~ 499 nm, accompanied by the highest PL intensity among the samples, indicating enhanced radiative recombination efficiency. This behavior suggests increased defect- or functional-group-mediated emission pathways, rendering G-TBAB potentially attractive for light-emitting and optoelectronic applications. Conversely, Li-MWCNTs showed the lowest PL intensity, implying effective suppression of charge carrier recombination and prolonged carrier lifetimes. Such characteristics are advantageous for applications requiring efficient charge separation, including photovoltaic systems and energy storage materials 42 . Although these PL trends provide valuable insights into the electronic and recombination behavior of the materials, further device-level investigations are necessary to fully assess their practical performance. 3.6. Electrochemical Impedance Spectroscopy (EIS) Analysis EIS Nyquist plots and their corresponding fitted equivalent electrical circuit (EEC) models (Fig. 9 a and 9 b) provide detailed insight into the charge transport and interfacial processes within the fabricated films. The employed circuit model is shown as an inset, and the extracted electrochemical parameters are summarized in Table 3 . Among the investigated materials, FG exhibits the lowest series sheet resistance (RSS = 1.19 Ω.cm²) and charge transfer resistance (RCT = 2.54 Ω.cm²), indicating highly efficient charge transport across the electrode-electrolyte interface. This superior performance can be attributed to fluorine-induced electronic modulation, where the high electronegativity of fluorine promotes charge delocalization, suppresses recombination losses, and enhances electrical conductivity 43 , 44 . In Addition, FG displays the lowest interfacial capacitance (Qc), suggesting reduced charge accumulation and rapid carrier extraction. Collectively, these characteristics make FG particularly suitable as a charge-transport layer or counter-electrode material for photovoltaic and electrocatalytic devices. In contrast, G-TBAB exhibits a higher RCT value (12.91 Ω.cm − ²), reflecting increased resistance to interfacial charge transfer. The incorporation of bulky TBAB groups likely introduces steric hindrance, which limits charge mobility across the graphene surface. Nevertheless, the moderate values of QC and RSS indicate a reasonable balance between charge transport and charge storage, consistent with other quaternary ammonium salt (QAS)- modified carbon systems reported for hybrid energy-harvesting and storage devices 45 . Li-MWCNTs exhibited the highest resistance values among all samples, with RSS = 1.70 Ω cm² and RCT = 17.73 Ω cm², implying limited electrical conductivity and sluggish charge transfer. The incorporation of LiF may introduce structural defects or charge trapping sites that impede electronic transport. However, Li-MWCNTs exhibit the highest interfacial capacitance value (QC = 7.83 × 10 − 4 F. cm − 2 ) along with a pronounced Warburg impedance (W = 3.97 × 10 − 2 Ω.cm 2 ), indicative of enhanced ion diffusion and adsorption/insertion process. This electrochemical signature is characteristic of materials optimized for energy storage applications, particularly supercapacitors and battery electrodes 19 , 31 , 46 . Table 3 Electrochemical parameters from EIS fitting for thin films. Parameters R SS (Ω.cm − 2 ) Q C (F.cm − 2 ) n R CT (Ω.cm − 2 ) W (Ω.cm − 2 ) RSE (%) G-TBAB 1.51 1.76E-04 0.49 12.91 5.17E-02 7.935 FG 1.19 1.10E-04 0.53 2.54 3.25E-02 3.841 Li-MWNCTs 1.70 7.83E-04 0.48 17.73 3.97E-02 7.369 Overall, the EIS analysis clearly differentiates the functional roles of the synthesized materials. FG demonstrates the outstanding charge transfer properties (Rct = 2.54 Ω·cm²), making it the most promising candidate for photovoltaic and electrocatalytic applications. G-TBAB exhibits intermediate behavior, suitable for hybrid optoelectronic systems that require a balance between transport and storage. Li-MWCNTs despite their higher resistances, show strong ion diffusion and capacitive characteristics, highlighting their potential for energy storage technologies such as supercapacitors and batteries 44 , 46 . 4. Conclusions This work presents a systematic and comparative investigation of halogen-functionalized graphene (F and Br) and lithium-doped MWCNTs, elucidating how targeted chemical modification governs the structural, optical, and electrochemical properties of carbon nanomaterials. Comprehensive spectroscopic, microscopic, and electrochemical analyses unequivocally confirm successful doping and reveal pronounced modification in crystallinity, surface chemistry, morphology, and electronic behavior. Fluorinated graphene (FG) exhibits the most favorable charge transport characteristics, including the lowest charge transfer resistance and suppressed charge recombination, highlighting its strong potential as a charge transport or counter-electrode material in photovoltaic and high-frequency optoelectronic devices. Brominated graphene (G-TBAB) demonstrates enhanced and tunable photoluminescence combined with moderate electrochemical performance and hybrid optoelectronic applications. In contrast, Lithium-functionalized MWCNTs (Li-MWCNTs) show markedly increased interfacial capacitance and enhanced ion diffusion behavior, indicating their suitability as electrode materials for energy storage technologies, particularly supercapacitors and lithium-ion batteries. Importantly, this study establishes clear structure-property-application relationships, providing a rational framework for tailoring carbon nanomaterials toward specific energy conversion and storage functions. While the present work focuses on fundamental materials characterization, the results lay a solid foundation for future device-level investigations. Subsequent studies should address practical performance metrics, including photovoltaic efficiency, long-term electrochemical cycling stability, and rate capability, to fully assess technological viability. Furthermore, incorporation of life-cycle assessment and scalability analyses of the synthesis routes will be essential to align these advanced materials with the principles of sustainable and environmentally responsible technologies. Declarations Author Contribution ContributionsA. G. A.: Conceptualization, Formal analysis, Materials characterization, Methodology, Software, Validation, Electrochemical assessment, Writing – original draft, review & editing. W. S. G.: Methodology, Software, Materials characterization, Writing – original draft. M. A. E.: Methodology, Software, Investigation, Materials characterization. A. S. M.: Investigation, Software, Validation. A. M. E.: Writing – review & editing. K. I. K.: Conceptualization, Project administration, Resources, Supervision, Validation, Writing – review & editing. *Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Acknowledgements This work was supported by the Science, Technology & Innovation Funding Authority (STDF) (47434), Egypt. Data Availability All data supporting the findings of this study are available within the paper and its Supplementary Information. References Novoselov, K. S.; Geim, A. K.; Morozov, S. V.; Jiang, D.-e.; Zhang, Y.; Dubonos, S. V.; Grigorieva, I. V.; Firsov, A. A. Electric field effect in atomically thin carbon films. science 2004 , 306 (5696), 666-669. Schwierz, F. Graphene transistors. Nature nanotechnology 2010 , 5 (7), 487-496. Das, A.; Pisana, S.; Chakraborty, B.; Piscanec, S.; Saha, S. K.; Waghmare, U. V.; Novoselov, K. S.; Krishnamurthy, H. R.; Geim, A. K.; Ferrari, A. C. Monitoring dopants by Raman scattering in an electrochemically top-gated graphene transistor. Nature nanotechnology 2008 , 3 (4), 210-215. Rani, P.; Jindal, V. Designing band gap of graphene by B and N dopant atoms. RSC advances 2013 , 3 (3), 802-812. Sun, X.; Zhang, Y.; Song, P.; Pan, J.; Zhuang, L.; Xu, W.; Xing, W. Fluorine-doped carbon blacks: highly efficient metal-free electrocatalysts for oxygen reduction reaction. ACS catalysis 2013 , 3 (8), 1726-1729. Zhao, J.; Cabrera, C. R.; Xia, Z.; Chen, Z. Single− sided fluorine–functionalized graphene: A metal–free electrocatalyst with high efficiency for oxygen reduction reaction. Carbon 2016 , 104 , 56-63. Xue, Y.; Qi, Y.; Tong, T.; Xu, H.; Liu, Z.; Ji, C.; Zhang, J.; Gao, J.; Ma, C.; Jiang, Y. Photoluminescence and transport properties of fluorinated graphene via a weak fluorination strategy. Applied Physics Letters 2024 , 124 (18). Que, L.; Ai, J.; Shao, T.; Han, R.; Su, J.; Guo, Y.; Liu, Y.; Li, J.; Jian, X.; Zhou, Z. Fluorinated graphene films for Ultra-High sensitivity of Surface-Enhanced Raman scattering. Applied Surface Science 2023 , 616 , 156496. Prado, D. M. S.; Li, G.; del Rosario, J. A. D.; Ocon, J. D.; Abel Chuang, P. Y. Improved Oxygen Reduction Reaction Activity of Graphene via Mechanochemical Activation and Halogen‐Doping. ChemElectroChem 2025 , 12 (1), e202400494. Rabeel, M.; Kim, H.; Khan, M. A.; Abubakr, M.; Ahmad, I.; Ahmad, M.; Rehman, S.; Lee, M.-J.; Khan, M. F.; Kim, D.-k. Broadband and flexible photodiode of a bromine-doped lateral MoTe2 homojunction. ACS Photonics 2023 , 10 (12), 4425-4436. Iijima, S. Helical microtubules of graphitic carbon. nature 1991 , 354 (6348), 56-58. Lee, S. W.; Yabuuchi, N.; Gallant, B. M.; Chen, S.; Kim, B.-S.; Hammond, P. T.; Shao-Horn, Y. High-power lithium batteries from functionalized carbon-nanotube electrodes. Nature nanotechnology 2010 , 5 (7), 531-537. Kong, L.; Zhu, Y.; Williams, P. J.; Kabbani, M.; Brushett, F. R.; Rupp, J. L. Insights into Li+ storage mechanisms, kinetics, and reversibility of defect-engineered and functionalized multi-walled carbon nanotubes for enhanced energy storage. Journal of Materials Chemistry A 2024 , 12 (7), 4299-4311. Narayan, J.; Bezborah, K. Recent advances in the functionalization, substitutional doping and applications of graphene/graphene composite nanomaterials. RSC Advances 2024 , 14 (19), 13413-13444, 10.1039/D3RA07072G. DOI: 10.1039/D3RA07072G. Kabel, K. I.; Farag, A. A.; Elnaggar, E.; Al-Gamal, A. Improvement of graphene oxide characteristics depending on base washing. Journal of Superhard Materials 2015 , 37 (5), 327-334. Wang, Z.; Wang, J.; Li, Z.; Gong, P.; Liu, X.; Zhang, L.; Ren, J.; Wang, H.; Yang, S. Synthesis of fluorinated graphene with tunable degree of fluorination. Carbon 2012 , 50 (15), 5403-5410. Kuang, H.; Liao, H.; Zhang, Z.; Huang, S.; Mao, B.; Shan, W.; Duan, X.; Feng, X.; Li, T. Dynamic diels-alder reaction crosslinked metal-organic framework/poly (ionic liquid) composite solid electrolyte for lithium-metal batteries. Journal of Colloid and Interface Science 2025 , 139638. Thangavelu, K.; Rajendran, R.; Palanisamy, S.; Arumugam, P.; Thammasak, R. Powerful combination of FeWO4/g-C3N4 heterostructures for solar light driven photocatalytic degradation of tetracycline and its antibacterial activity. Materials Today Sustainability 2023 , 24 , 100562. Akechatree, N.; Rajendran, R.; Rojviroon, T.; Arumugam, P.; Vasudevan, V.; Sirivithayapakorn, S.; Dhayalan, A.; Wongpipun, P.; Phetyim, N.; Rojviroon, O. Development of Z-scheme BiVO4/g-C3N4/rGO heterojunction nanocomposite for enhanced photocatalytic degradation and antibacterial activity. Materials Research Bulletin 2025 , 181 , 113119. Thankulkit, P.; Rojviroon, O.; Rajendran, R.; Alsawalha, M.; Arumugam, P.; Rojviroon, T.; Sirivithayapakorn, S. Development of AgFeO2/g-C3N4/RGO nanocomposites with superior photocatalytic activity and antibacterial properties for wastewater treatment. Journal of Water Process Engineering 2025 , 69 , 106650. Rajendran, R.; Rojviroon, O.; Vasudevan, V.; Arumugam, P.; Handayani, M.; Akechatree, N.; Leelert, Y.; Rojviroon, T. Magnetically separable ternary heterostructure photocatalyst CuFe2O4/g-C3N4/rGO: Enhancing photocatalytic degradation and bacterial inactivation. Journal of Water Process Engineering 2024 , 63 , 105443. Priyadharsan, A.; Kamaraj, C.; Ranjith, R.; Sivakumar, S.; Dewiani, R. Y.; Thammasak, R.; Periyasami, G.; Murni, H. Synthesis of multifunctional rGO/g-C3N4/FeTiO3 ternary nanocomposites for photocatalyst, antibacterial, and ecotoxicity assessment of zebrafish embryo model. Journal of Alloys and Compounds 2024 , 1007 , 176256. Wongwichian, S.; Rajendran, R.; Rojviroon, O.; Arumugam, P.; Sirivithayapakorn, S.; Rojviroon, T. Micro-nanobubble assisted photocatalytic and antibacterial activity of ZnFe2O4/g-C3N4/rGO nanocomposite. Environmental Nanotechnology, Monitoring & Management 2025 , 23 , 101065. Yalcinkaya, F. N.; Doğan, M.; Bicil, Z.; Kizilduman, B. K. Effect of functionalization and Li-doping methods to hydrogen storage capacities of MWCNTs. Fuel 2024 , 372 , 132274. Hocker, S.; Hudson-Smith, N.; Schniepp, H. C.; Kranbuehl, D. E. Enhancing polyimide's water barrier properties through addition of functionalized graphene oxide. Polymer 2016 , 93 , 23-29. Ferreira, F. V.; Cividanes, L. D. S.; Brito, F. S.; de Menezes, B. R. C.; Franceschi, W.; Simonetti, E. A. N.; Thim, G. P. Functionalization of graphene and applications. In Functionalizing graphene and carbon nanotubes: a review , Springer, 2016; pp 1-29. Guo, H.; Liu, F.; Zhao, J.; Yao, H.; Jin, R.; Kang, C.; Bian, Z.; Qiu, X.; Gao, L. In situ iodoalkane-reduction of graphene oxide in a polymer matrix: An easy and effective approach for the fabrication of conductive composites. Journal of Materials Chemistry C 2015 , 3 (43), 11531-11539. Mokgohloa, M.; Ogunlaja, A. S. Synthesis and characterization of ethylenediamine functionalized graphene oxide-modified UiO-66-NH2 for quinoline removal. Carbon Letters 2022 , 32 (7), 1689-1702. Zhang, K.; Mao, L.; Zhang, L. L.; Chan, H. S. O.; Zhao, X. S.; Wu, J. Surfactant-intercalated, chemically reduced graphene oxide for high performance supercapacitor electrodes. Journal of Materials Chemistry 2011 , 21 (20), 7302-7307. Nebogatikova, N.; Antonova, I.; Prinz, V. Y.; Kurkina, I.; Vdovin, V.; Aleksandrov, G.; Timofeev, V.; Smagulova, S.; Zakirov, E.; Kesler, V. Fluorinated graphene dielectric films obtained from functionalized graphene suspension: preparation and properties. Physical Chemistry Chemical Physics 2015 , 17 (20), 13257-13266. Kang, W.; Li, S. Preparation of fluorinated graphene to study its gas sensitivity. RSC advances 2018 , 8 (41), 23459-23467. Konni, M.; Kumar Karnena, M.; Babu Mukkamala, S. Enhanced Room‐Temperature Synthesis of Li@ f‐MWCNTs for Hydrogen Storage Application. ChemistrySelect 2020 , 5 (14), 4292-4296. Tiwari, A.; Singh, V. Synthesis and characterization of electrical conducting chitosan-graft-polyaniline. Express Polymer Letters 2007 , 1 (5), 308-317. Gomez, N. A. G.; Maruyama, S. A.; Leuteritz, A.; Wypych, F. Composites of polyethylene and layered cobalt hydroxide salts as potential ultraviolet radiation absorbers. Polymer Bulletin 2020 , 77 (1), 255-273. Ibrahim, A. I.; Onaizi, S. A.; Vohra, M. S. Novel CTAB functionalized graphene oxide for selenium removal: adsorption results and ANN & RSM modeling. Emergent Materials 2024 , 7 (2), 547-564. Guérin, K.; Pinheiro, J.; Dubois, M.; Fawal, Z.; Masin, F.; Yazami, R.; Hamwi, A. Synthesis and characterization of highly fluorinated graphite containing sp2 and sp3 carbon. Chemistry of materials 2004 , 16 (9), 1786-1792. Liang, G.; Sun, X.; Lai, J.; Wei, C.; Huang, Y.; Hu, H. Adding lithium fluoride to improve the electrochemical properties SnO2@ C/MWCNTs composite anode for lithium-ion batteries. Journal of Electroanalytical Chemistry 2019 , 853 , 113401. Zhao, J.; Zhai, X.; Tao, X.; Liu, H.; Liu, W.; Jiang, D.; Gao, S. Effect of MWCNTs and lithium modified MWCNTs on electrochemical hydrogen storage properties of Co0. 9Cu0. 1Si alloy. International Journal of Hydrogen Energy 2018 , 43 (29), 13383-13392. El-Khair, M. A. A.; Al-Gamal, A. G.; Kabel, K. I.; Gado, W. S.; Morshedy, A. S. Harvesting the synergistic effect of CuFe2O4@Ni-MOF nanomagnetic photocatalyst for enhanced visible light-driven green hydrogen production. International Journal of Hydrogen Energy 2025 , 101 , 280-294. DOI: https://doi.org/10.1016/j.ijhydene.2024.12.449. El-Khair, M. A. A.; Hanafi, S. A.; Abd El-Moghny, M. G.; El Saied, M.; Elmelawy, M. S.; El-Deab, M. S. Boosted Bio-Jet production: Unveiling the potential of a one-stage concurrent process of deoxygenation/upgrading versus two-stage sequential processes using Pt/Cl-Al2O3@ Ni/ZSM-5 catalysts. Chemical Engineering Journal 2024 , 490 , 151716. Jankovský, O.; Šimek, P.; Klimova, K.; Sedmidubský, D.; Matějková, S.; Pumera, M.; Sofer, Z. Towards graphene bromide: bromination of graphite oxide. Nanoscale 2014 , 6 (11), 6065-6074. Pace, G.; Serri, M.; del Rio Castillo, A. E.; Ansaldo, A.; Lauciello, S.; Prato, M.; Pasquale, L.; Luxa, J.; Mazánek, V.; Sofer, Z. Nitrogen-doped graphene based triboelectric nanogenerators. Nano Energy 2021 , 87 , 106173. Teklu, A.; Barry, C.; Palumbo, M.; Weiwadel, C.; Kuthirummal, N.; Flagg, J. Mechanical characterization of reduced graphene oxide using AFM. Advances in Condensed Matter Physics 2019 , 2019 (1), 8713965. Zeng, X.; Peng, Y.; Yu, M.; Lang, H.; Cao, X. a.; Zou, K. Dynamic sliding enhancement on the friction and adhesion of graphene, graphene oxide, and fluorinated graphene. ACS applied materials & interfaces 2018 , 10 (9), 8214-8224. Gorji, Z. E.; Khodadadi, A. A.; Riahi, S.; Repo, T.; Mortazavi, Y.; Kemell, M. Functionalization of nitrogen-doped graphene quantum dot: A sustainable carbon-based catalyst for the production of cyclic carbonate from epoxide and CO2. Journal of Environmental Sciences 2023 , 126 , 408-422. DOI: https://doi.org/10.1016/j.jes.2022.04.046. Heydari, P.; Hafizi, A.; Rahimpour, M.; Khalifeh, R. Experimental investigation of improved graphene oxide as an efficient catalyst for the sustainable chemical fixation of CO2 with epoxides. Journal of Environmental Chemical Engineering 2020 , 8 (6), 104568. Liu, W.; Deng, N.; Wang, G.; Yu, R.; Wang, X.; Cheng, B.; Ju, J.; Kang, W. Fluoridation routes, function mechanism and application of fluorinated/fluorine-doped nanocarbon-based materials for various batteries: A review. Journal of Energy Chemistry 2023 , 85 , 363-393. DOI: https://doi.org/10.1016/j.jechem.2023.06.020. Al-khattib, M.; Samir, A.; Morgan, N. N.; Hassablla, S. Synthesis, Structure Parameters and Optical Properties of Graphite and Graphene Oxide Sheet. Hunt, A.; Kurmaev, E.; Moewes, A. Band gap engineering of graphene oxide by chemical modification. Carbon 2014 , 75 , 366-371. Njema, G. G.; Kibet, J. K. A review of chalcogenide-based perovskites as the next novel materials: Solar cell and optoelectronic applications, catalysis and future perspectives. Next Nanotechnology 2025 , 7 , 100102. Villarreal, C. C.; Sandoval, J. I.; Ramnani, P.; Terse-Thakoor, T.; Vi, D.; Mulchandani, A. Graphene compared to fluorine-doped tin oxide as transparent conductor in ZnO dye-sensitized solar cells. Journal of Environmental Chemical Engineering 2022 , 10 (3), 107551. Kim, S.-H.; Lee, C.-H.; Yun, J.-M.; Noh, Y.-J.; Kim, S.-S.; Lee, S.; Jo, S. M.; Joh, H.-I.; Na, S.-I. Fluorine-functionalized and simultaneously reduced graphene oxide as a novel hole transporting layer for highly efficient and stable organic photovoltaic cells. Nanoscale 2014 , 6 (13), 7183-7187, 10.1039/C4NR01038H. DOI: 10.1039/C4NR01038H. Yu, X.; Yang, L.; Lv, Q.; Xu, M.; Chen, H.; Yang, D. The enhanced efficiency of graphene–silicon solar cells by electric field doping. Nanoscale 2015 , 7 (16), 7072-7077, 10.1039/C4NR06677D. DOI: 10.1039/C4NR06677D. Sim, Y.; Surendran, S.; Cha, H.; Choi, H.; Je, M.; Yoo, S.; Seok, D. C.; Jung, Y. H.; Jeon, C.; Kim, D. J. Fluorine-doped graphene oxide prepared by direct plasma treatment for supercapacitor application. Chemical Engineering Journal 2022 , 428 , 132086. Roy-Mayhew, J. D.; Aksay, I. A. Graphene materials and their use in dye-sensitized solar cells. Chemical reviews 2014 , 114 (12), 6323-6348. Kuppu, S. V.; Senthilkumaran, M.; Sethuraman, V.; Balaji, M.; Saravanan, C.; Ahmed, N.; Mohandoss, S.; Lee, Y. R.; Anandharaj, J.; Stalin, T. The surfactants mediated electropolymerized poly (aniline)(PANI)-reduced graphene oxide (rGO) composite counter electrode for dye-sensitized solar cell. Journal of Physics and Chemistry of Solids 2023 , 173 , 111121. Mohamed, N. B.; El‐Kady, M. F.; Kaner, R. B. Macroporous graphene frameworks for sensing and supercapacitor applications. Advanced Functional Materials 2022 , 32 (42), 2203101. Nurdin, I.; Fitri, H.; Widiatmoko, P.; Devianto, H.; Prakoso, T. The effect of cationic CTAB surfactants on the performance of graphene electrode for supercapacitor. In IOP Conference Series: Materials Science and Engineering , 2020; IOP Publishing: Vol. 823, p 012038. Basa, A.; Tatko, D.; Lapinska, K.; Wilczewska, A. Z.; Goclon, J.; Winkler, K.; Kuhn, A.; García-Alvarado, F. Li3FeF6/Fe2O3, LiF anchored oxidized multi-wall carbon nanotubes as high power cathode in lithium ion batteries. Journal of Power Sources 2025 , 630 , 236103. Additional Declarations No competing interests reported. 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Kabel","email":"","orcid":"","institution":"Egyptian Petroleum Research Institute","correspondingAuthor":false,"prefix":"","firstName":"Khalid","middleName":"I.","lastName":"Kabel","suffix":""}],"badges":[],"createdAt":"2026-03-20 21:38:27","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-9182061/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-9182061/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":107092192,"identity":"d6b84bb5-b762-4980-a2bc-dd0fa5be8796","added_by":"auto","created_at":"2026-04-16 16:10:57","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":223152,"visible":true,"origin":"","legend":"\u003cp\u003eFTIR spectra of a) GO, b) G-TBAB, c) FG, and d) Li-MWCNTs\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-9182061/v1/76fda1a0a854d1482a890b62.png"},{"id":107481562,"identity":"7eacf14d-0131-48cc-b15c-d6a22a8ef98a","added_by":"auto","created_at":"2026-04-22 02:19:06","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":218101,"visible":true,"origin":"","legend":"\u003cp\u003eXRD patterns of a) GO, b) G-TBAB, c) FG, and d) LI-MWCNTs\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-9182061/v1/0427ce31705665760e2f177b.png"},{"id":107092186,"identity":"f6867568-426d-4398-b2f3-0f17fcb838b1","added_by":"auto","created_at":"2026-04-16 16:10:57","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":343545,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003ea:\u003c/strong\u003e XPS of Li-MWCNT\u003c/p\u003e\n\u003cp\u003e\u003cbr\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eb:\u003c/strong\u003e XPS analysis of G-TBAB.\u003c/p\u003e\n\u003cp\u003e\u003cbr\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ec:\u003c/strong\u003e XPS analysis of FG material.\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-9182061/v1/d85f4be1a672fb1c783ea689.png"},{"id":107480964,"identity":"fc4e476b-0800-40e3-8b33-953634bdc4f2","added_by":"auto","created_at":"2026-04-22 02:14:47","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":938611,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003ea. \u003c/strong\u003eSEM, EDX, and mapping of G-TBAB\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eb\u003c/strong\u003e: SEM image, Mapping, and EDX of Li-MWCNTs material.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ec\u003c/strong\u003e: SEM, EDX, and mapping of FG\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-9182061/v1/7fbdf38af75c46c5649e9431.png"},{"id":107092185,"identity":"81d1ea00-5a93-4bb1-9330-a81b6044db6e","added_by":"auto","created_at":"2026-04-16 16:10:57","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":682619,"visible":true,"origin":"","legend":"\u003cp\u003eHR-TEM of GO (a and b), FG (c and d), G-TBAB (e and f), and Li-MWCNTs (g\u003c/p\u003e\n\u003cp\u003eand h) at two different magnifications.\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-9182061/v1/3193603734d5149799b46927.png"},{"id":107483245,"identity":"90a2d685-d8e6-41a8-a615-eedf16657d86","added_by":"auto","created_at":"2026-04-22 02:27:01","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":679186,"visible":true,"origin":"","legend":"\u003cp\u003e3D\u003cstrong\u003e \u003c/strong\u003etopographic\u003cstrong\u003e \u003c/strong\u003eAFM of GO, FG, G-TBAB, and Li-MWCNTs\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-9182061/v1/7ab488ea1d99a18fcc66ab11.png"},{"id":107092188,"identity":"abc83ea1-a9f0-4665-91f0-ccc393fe3da0","added_by":"auto","created_at":"2026-04-16 16:10:57","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":152060,"visible":true,"origin":"","legend":"\u003cp\u003e(a) UV-Vis spectra of GO, Li-MWCNTs, FG, and G-TBAB, (b) Band gap of GO, Li-MWCNTs, FG, and G-TBAB.\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-9182061/v1/c4a1b803ccb4fab2fad7036b.png"},{"id":107092215,"identity":"13b7ba14-cd0d-4419-adbb-ceec5aab5044","added_by":"auto","created_at":"2026-04-16 16:11:02","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":81907,"visible":true,"origin":"","legend":"\u003cp\u003ePL of GO, Li-MWCNTs, FG, and G-TBAB\u003c/p\u003e","description":"","filename":"8.png","url":"https://assets-eu.researchsquare.com/files/rs-9182061/v1/3c035425b2ae68307dbb51cd.png"},{"id":107092193,"identity":"61efb3af-033b-414e-939f-742e998ea035","added_by":"auto","created_at":"2026-04-16 16:10:57","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":100661,"visible":true,"origin":"","legend":"\u003cp\u003eResistance detection of G-TBAB, FG, and Li-MWNCTs films between ITO and Au as transparent conductive electrode (TCE) and counter electrode (CE) using EIS (a) and its integrated EEC (b).\u003c/p\u003e","description":"","filename":"9.png","url":"https://assets-eu.researchsquare.com/files/rs-9182061/v1/c626342c644ec71470b3da8f.png"},{"id":107868806,"identity":"6af29b7d-78c2-41bb-8ee8-eaa6775381cb","added_by":"auto","created_at":"2026-04-27 07:34:09","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":3951800,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-9182061/v1/25b2ef53-5004-493f-aa52-550f624fdf2b.pdf"},{"id":107092190,"identity":"9f114ae8-6273-482b-92d3-61eead709442","added_by":"auto","created_at":"2026-04-16 16:10:57","extension":"docx","order_by":0,"title":"","display":"","copyAsset":false,"role":"supplement","size":17357,"visible":true,"origin":"","legend":"","description":"","filename":"SI.docx","url":"https://assets-eu.researchsquare.com/files/rs-9182061/v1/35832a99a676d05d32abb943.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Dopant-Dependent Structure–Property Relationships in Functionalized Graphene and MWCNTs for Sustainable Energy Applications","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eGraphene, a two-dimensional monolayer of sp\u0026sup2;-hybridized carbon atoms arranged in a honeycomb lattice, has revolutionized materials science since its isolation \u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e. Its extraordinary properties-including ultra-high electron mobility (\u0026gt;\u0026thinsp;200,000 cm\u0026sup2; V⁻\u0026sup1; s⁻\u0026sup1;), exceptional thermal conductivity, superior mechanical strength, and vast specific surface area-have positioned it as a cornerstone material for next-generation technologies in electronics, photonics, sensing, and energy conversion \u003csup\u003e\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u003c/sup\u003e. However, the absence of an intrinsic bandgap in pristine, defect-free graphene fundamentally limits its direct application in logic devices and certain optoelectronic systems that require a well-defined on/off switching behavior \u003csup\u003e\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u003c/sup\u003e. To address this limitation, extensive research efforts have focused on engineering graphene's electronic structure. Among the various approaches, chemical doping has emerged as a highly effective and versatile strategy to precisely modulate graphene's electrical conductivity, optical absorption, and surface reactivity \u003csup\u003e\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eThe introduction of heteroatoms or functional groups enables Fermi level tuning, bandgap opening, and improves interfacial compatibility, thereby tailoring graphene for specific applications. Halogen doping, leveraging the high electronegativity and distinct bonding characteristics of elements such as fluorine and bromine, has attracted significant attention for inducing controllable electronic and optical modifications in graphene \u003csup\u003e\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u003c/sup\u003e. Fluorine, owing to its small atomic radius and extreme electronegativity, induces strong electron-withdrawing effects upon covalent bonding with carbon. This interaction locally transforms sp\u0026sup2; to sp\u0026sup3; hybridization, resulting in lattice distortion, bandgap opening, and, in many cases, enhanced photoluminescence (PL) \u003csup\u003e\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u003c/sup\u003e. In contrast, bromine doping predominantly introduces \u003cem\u003ep\u003c/em\u003e-type behavior through charge-transfer interactions, while largely preserving the metallic nature of the graphene basal plane due to bromine\u0026rsquo;s lower electronegativity and larger van der Waals radius \u003csup\u003e\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u003c/sup\u003e. This fundamental contrast provides a powerful framework for rationally designing graphene derivatives with tunable electronic and optical properties via selective halogen functionalization.\u003c/p\u003e \u003cp\u003eIn parallel with graphene research, carbon nanotubes (CNTs), particularly multi-walled carbon nanotubes (MWCNTs), have been extensively studied for their outstanding one-dimensional electrical conductivity, mechanical robustness, and high aspect ratio \u003csup\u003e\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u003c/sup\u003e. Moreover, functionalization of MWCNTs with alkali metals, particularly lithium, markedly augments their electrochemical performance by introducing additional charge carriers and modifying surface energetics. Lithium-functionalized MWCNTs (Li-MWCNTs) have demonstrated significant promise as high-capacity anode materials for lithium-ion batteries and as conductive additives in supercapacitors, owing to improved ion intercalation kinetics and charge storage capacity \u003csup\u003e\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eRecent advances in composite solid electrolytes, such as dynamic crosslinked metal-organic framework/poly(ionic liquid) networks, highlight the critical importance of engineered interfaces and optimized ionic transport pathways in next-generation battery technologies \u003csup\u003e\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u003c/sup\u003e. This principle is equally applicable to the design of functionalized carbon electrodes. Despite notable progress in halogen-doped graphene and Li-functionalized CNTs individually, systematic studies exploring their combined effects within an integrated hybrid framework remain limited. The rational design of such multifunctional heterostructures offers the potential to overcome the intrinsic limitations of individual components, yielding composite materials with tunable conductivity, engineered band gaps, enhanced interfacial interactions, and superior mechanical and thermal performance.\u003c/p\u003e \u003cp\u003eThe broader field of carbon-based hybrid materials has demonstrated the transformative impact of strategic material integration. For instance, heterostructures such as FeWO₄/g-C₃N₄ \u003csup\u003e13\u003c/sup\u003e and Z-scheme BiVO₄/g-C₃N₄/rGO \u003csup\u003e\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u003c/sup\u003e have achieved exceptional solar-driven photocatalytic activity through optimized interfacial charge transfer. Similarly, nanocomposites such as AgFeO₂/g-C₃N₄/RGO \u003csup\u003e\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u003c/sup\u003e and CuFe₂O₄/g-C₃N₄/rGO \u003csup\u003e\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u003c/sup\u003e combine photocatalytic activity with magnetic separability and antibacterial functionality for wastewater treatment. Multifunctional architectures such as rGO/g-C₃N₄/FeTiO₃ \u003csup\u003e17\u003c/sup\u003e and ZnFe₂O₄/g-C₃N₄/rGO \u003csup\u003e\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u003c/sup\u003e further illustrate how carbon-based platforms can deliver synergistic optoelectronic, catalytic, and biological performance. Collectively, these studies emphasize that the performance enhancement of carbon nanomaterials arises not only from doping but also from the deliberate creation of synergistic interfacial architectures.\u003c/p\u003e \u003cp\u003eMotivated by these considerations, the present work aims to systematically elucidate the fundamental structure\u0026ndash;property relationships in advanced carbon-based hybrids. We report a comprehensive study on the synthesis and characterization of halogen (F, Br)-doped graphene and lithium-decorated MWCNTs. A broad range of complementary spectroscopic, microscopic, and electrochemical techniques, including FTIR, XRD, XPS, SEM, TEM, AFM, UV-Vis, PL, and EIS, is employed to elucidate how specific chemical functionalization strategies influence the structural, morphological, optical, and electrical properties of the carbon framework.\u003c/p\u003e \u003cp\u003eWe hypothesize that controlled chemical doping enables precise tuning of material properties towards distinct sustainable and technological applications. Our results demonstrate that fluorinated graphene (FG) exhibits superior electrical conductivity, making it highly suitable for photovoltaic and electronic devices, while brominated graphene (G-TBAB) displays enhanced and tunable photoluminescence, favoring optoelectronics and sensing applications. In parallel, Li-MWCNTs exhibit optimized ion-storage capacity and diffusion kinetics, underscoring their potential for electrochemical energy storage systems. This study not only bridges an important knowledge gap regarding the combined effects of halogen and alkali metal functionalization in carbon nanostructures but also provides a rational materials design framework. The insights gained contribute to the development of high-performance, sustainable carbon-based materials for next-generation energy conversion and storage technologies, in alignment with the global clean energy objectives.\u003c/p\u003e"},{"header":"2. Experimental Section","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1. Materials\u003c/h2\u003e \u003cp\u003eGraphite powder (Sigma-Aldrich, 99.99%), Tetrabutylammonium bromide (TBAB, Alfa Aesar, 99%), Hydrofluoric Acid (HF, 48%, Merck), Lithium Fluoride (LiF, Sigma-Aldrich, 99.99%). MWCNTs were supplied from the Egyptian Petroleum Research Institute (EPRI), these nanotubes have diameters ranging from 10 to 40 nm, lengths between 10 and 100 \u0026micro;m, and consist of approximately 40 to 50 walls. Ammonium hydroxide (NH\u003csub\u003e4\u003c/sub\u003eOH, 30%), sulfuric acid (H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e, 97%), Hydrochloric acid (HCl, 37%), Nitric acid (HNO\u003csub\u003e3\u003c/sub\u003e, 37%), hydrogen peroxide (H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e, 10%), Ethanol, and Methanol were supplied from Honeywell Co. (USA). Indium tin oxide (ITO) (Sigma-Aldrich). Deionized water (18.2 MΩ\u0026middot;cm). All chemicals were used as received.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2. Synthesis of Graphene Oxide (GO)\u003c/h2\u003e \u003cp\u003eGO was synthesized from graphite powder using an improved Hummers' method [16]. Briefly, graphite (1 g) and NaNO\u003csub\u003e3\u003c/sub\u003e (0.5 g) were dispersed in 23 ml of concentrated H₂SO₄ under continuous stirring in an ice bath to maintain a temperature below 5\u0026deg;C. Subsequently, KMnO\u003csub\u003e4\u003c/sub\u003e (3 g) was added gradually to prevent overheating. The mixture was stirred at 35\u0026deg;C for 2 hours, during which the suspension turned a dark brown color. Afterward, 46 ml of deionized water was slowly added, followed by 10 ml of H₂O₂ to terminate the reaction. The resulting solution was filtered and washed sequentially with 5% HCl and deionized water until a neutral pH was achieved. The final graphene oxide was freeze-dried (lyophilized) to prevent aggregation and stored in a desiccator \u003csup\u003e\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.3. Functionalization of Carbon Materials\u003c/h2\u003e \u003cdiv id=\"Sec6\" class=\"Section3\"\u003e \u003ch2\u003e2.3.1. Synthesis of Brominated Graphene (G-TBAB)\u003c/h2\u003e \u003cp\u003eA similar procedure involving the functionalization of graphene oxide (GO) with TBAB was employed to obtain noncovalently functionalized G-TBAB particles \u003csup\u003e\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e. Briefly, (1 g) of GO was dispersed in 100 ml of distilled water (DI) and sonicated, followed by the gradual addition of (1 g) of TBAB. After 2 h of sonication, the resulting mixture was transferred to a Teflon-lined autoclave and heated at 200\u0026deg;C for 12 h. The suspension was then allowed to settle for 24 h and subsequently centrifuged to collect the G-TBAB. The collected product was thoroughly washed with deionized water until the filtrate became clear, ensuring the removal of residual impurities, and finally dried at 80\u0026deg;C.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section3\"\u003e \u003ch2\u003e2.3.2. Synthesis of Fluorinated Graphene (FG)\u003c/h2\u003e \u003cp\u003eThe fluorinated graphene (FG) was synthesized via a hydrothermal approach. Briefly, (1 g) of GO was suspended in a mixed solution of HF (40 wt%) and deionized water at a volume ratio of 10:90, followed by ultrasonication for 1 min to ensure homogeneous dispersion. The resulting mixture was transferred to a Teflon-lined autoclave and heated at 180\u0026deg;C for 24 h. After naturally cooling to room temperature, the product was collected by filtration using a microporous membrane, thoroughly washed with ultrapure water to remove residual reactants, and freeze-dried to obtain FG \u003csup\u003e11\u003c/sup\u003e.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section3\"\u003e \u003ch2\u003e2.3.3. Synthesis of Lithium-Functionalized MWCNTs (Li-MWCNTs)\u003c/h2\u003e \u003cp\u003eLithium-functionalized multi-walled carbon nanotubes (MWCNTs) were synthesized via a solvent-mediated method in a Teflon-lined reactor. Briefly, (0.5 g) of MWCNTs was dispersed in 100 ml of a 1 M LiF aqueous solution and magnetically stirred for 24 h to enable lithium incorporation. The resulting solid product was collected by vacuum filtration, repeatedly washed with deionized water to remove unreacted species and residual salts, and subsequently dried under vacuum at 100\u0026deg;C for 24 h \u003csup\u003e19\u003c/sup\u003e.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec9\" class=\"Section3\"\u003e \u003ch2\u003e2.3.4. Fabrication of Thin Films for Electrical Measurements\u003c/h2\u003e \u003cp\u003eThin films of each material (FG, G-TBAB, and Li-MWCNTs) were prepared by dispersing the powders in ethanol at a concentration of 1.0 mg/ml, followed by ultrasonication for 30 min to ensure homogeneous suspensions. Aliquots of 100 \u0026micro;l were drop-cast onto pre-cleaned ITO substrates (1\u0026times;2 cm\u003csup\u003e2\u003c/sup\u003e) and dried at 60\u0026deg;C to form uniform films. A gold counter electrode with a thickness of 50 nm was subsequently deposited by thermal evaporation through a shadow mask, yielding a two-electrode device configuration.\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003e2.4. Electrochemical Impedance Spectroscopy (EIS)\u003c/h2\u003e \u003cp\u003eEIS measurements were performed using an Origalys (OrigaFlex 01A, potentiostat) in a two-electrode configuration, with the deposited film on ITO serving as working electrode and a gold (Au) as counter electrode. The impedance spectra were recorded over a frequency range of 100 kHz to 250 mHz with a 150 mV AC amplitude. The experimental data were fitted to an equivalent circuit model using Origalyx software to extract key electrochemical parameters, including film resistance (R\u003csub\u003ef\u003c/sub\u003e), charge transfer resistance (R\u003csub\u003ect\u003c/sub\u003e), constant phase element (CPE), Warburg impedance (W), and the CPE exponent (n). All measurements were performed in triplicate (n\u0026thinsp;=\u0026thinsp;3), and the reported values represent the mean\u0026thinsp;\u0026plusmn;\u0026thinsp;standard deviation. The CPE exponent (n) provides insight into the electrochemical behavior of the system, with (n\u0026thinsp;=\u0026thinsp;0) resistive behavior, (n\u0026thinsp;=\u0026thinsp;1) inductive behavior, (n = -1) capacitive behavior, and (n\u0026thinsp;=\u0026thinsp;0.5) Warburg impedance.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003e2.5. Material Characterization\u003c/h2\u003e \u003cp\u003eThe synthesized materials were characterized using a comprehensive suite of analytical techniques. Fourier-transform infrared (FTIR) spectroscopy (PerkinElmer Spectrum One) was used to identify functional groups over the wavenumber range of 400\u0026ndash;4000 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. Crystal structures and phase composition were analyzed by X-ray diffraction (XRD, PANalytical X'Pert PRO) using Cu Kα radiation (λ\u0026thinsp;=\u0026thinsp;1.5406 \u0026Aring;). Surface morphology and elemental composition were examined by Field-emission scanning electron microscopy (FESEM, JEOL JSM-6360), coupled with energy-dispersive X-ray spectroscopy (EDX). High-resolution transmission electron microscopy (HR-TEM, JEOL JEM-2100F) was used to examine particle size, morphology and internal structure. Surface topology was further analyzed by atomic force microscopy (AFM, Bruker Dimension Icon) in tapping mode. Optical properties were assessed using UV-Vis diffuse reflectance spectroscopy (JASCO V-770) to determine optical band gaps, while photoluminescence (PL) spectra were recorded using a JASCO FP-6500 spectrofluorometer with an excitation at 320 nm. X-ray photoelectron spectroscopy (XPS, Thermo Scientific K-Alpha) equipped with Al Kα source was utilized to analyze surface elemental composition and oxidation states.\u003c/p\u003e \u003c/div\u003e"},{"header":"3. Results and Discussion","content":"\u003cdiv id=\"Sec13\" class=\"Section2\"\u003e\n \u003ch2\u003e3.1. Structural and Chemical Characterization\u003c/h2\u003e\n \u003cdiv id=\"Sec14\" class=\"Section3\"\u003e\n \u003ch2\u003e3.1.1. FTIR Analysis\u003c/h2\u003e\n \u003cp\u003eThe FTIR spectrum of graphene functionalized with TBAB exhibits distinct characteristic peaks, confirming successful noncovalent functionalization. The main absorption bands associated with graphene oxide (GO) appear at 3734.20, 1699.78, and 1035.56 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, corresponding to O\u0026ndash;H stretching, C\u0026thinsp;=\u0026thinsp;O stretching, and C\u0026ndash;O stretching vibrations, respectively. However, the intensities of these bands are markedly reduced compared to pristine GO, as shown in \u003cstrong\u003eFig.\u0026nbsp;1a and 1b\u003c/strong\u003e \u003csup\u003e20\u003c/sup\u003e, indicating partial modification or masking of oxygen-containing functional groups upon TBAB incorporation. A broad absorption band at 3422.53 cm⁻\u0026sup1; is assigned to N\u0026ndash;H stretching vibrations, characteristic of amine functionalities, suggesting the presence of TBAB or related surface interactions \u003csup\u003e\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\n \u003cp\u003eThe peak at 2966.68 cm⁻\u0026sup1; represents C\u0026ndash;H stretching vibrations, typical of aliphatic bonds and likely arising from the alkyl chains introduced by TBAB \u003csup\u003e\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e\u003c/sup\u003e. The band at 1551.67 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e is attributed to N\u0026ndash;H bending vibrations, further supporting the presence of amine groups associated with TBAB \u003csup\u003e\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u003c/sup\u003e. In addition, the absorption band at 1175.11 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e is assigned to C\u0026ndash;N stretching vibrations. The positively charged ammonium ion (R\u003csub\u003e4\u003c/sub\u003eN⁺) in TBAB can engage in electrostatic interactions with negatively charged oxygen-containing groups on GO, which likely contributes to the observed reduction in the intensities of epoxy, carboxyl, and hydroxyl-related peaks in the FTIR spectrum of the G-TBAB composite \u003csup\u003e\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e\u003c/sup\u003e. Collectively, these spectral features substantiate the successful attachment of TBAB onto the graphene surface through noncovalent interactions, as evidenced by the emergence of amine (N\u0026ndash;H and C\u0026ndash;N) vibrational modes and the attenuation of GO oxygenated functional-group signals.\u003c/p\u003e\n \u003cp\u003eFigure \u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ec presents the FTIR spectrum of FG, which exhibits characteristic absorption bands corresponding to C\u0026ndash;O, C\u0026ndash;F, C\u0026thinsp;=\u0026thinsp;C, C\u0026thinsp;=\u0026thinsp;O, and OH at 1035.56, 1209.01, 1541.74, 1705.95, and 3434.53 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, respectively. The C\u0026ndash;F stretching vibration, appearing in the range of 1200 and 1220 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, is indicative of covalent bonding between fluorine atoms and \u003cem\u003esp\u0026sup3;\u003c/em\u003e-hybridized carbon sites \u003csup\u003e\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e\u003c/sup\u003e. Notably, the intensities of the C\u0026ndash;O and C\u0026thinsp;=\u0026thinsp;O stretching vibrations in FG are stronger than those typically observed in graphite fluoride, with a particularly pronounced enhancement of the C\u0026ndash;O band relative to C\u0026thinsp;=\u0026thinsp;O. This observation suggests that oxygen-containing functional groups in FG are predominantly incorporated in the form of C\u0026ndash;O linkages \u003csup\u003e\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\n \u003cp\u003eThe FTIR spectrum for Li-MWCNTs is shown in Fig. \u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ed, displaying absorption bands at approximately 2973.76 and 2890.41 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, which are attributed to C\u0026ndash;H stretching vibrations. The bands observed near 1640.01 and 1540.07 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e correspond to the C\u0026thinsp;=\u0026thinsp;O and C\u0026thinsp;=\u0026thinsp;C stretching vibrations, respectively. A distinct absorption peak at around 642.89 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e is assigned to Li\u0026ndash;O vibrations, indicating the formation of lithium-oxygen bonds following the doping process \u003csup\u003e\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e\u003c/sup\u003e. The relatively strong intensity of this band suggests substantial Li incorporation within the MWCNTs structure \u003csup\u003e\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e\u003c/sup\u003e. Additional absorption bands at 1401.70, 1134.62, and 3402.97 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e are attributed to C\u0026ndash;O stretching, hydroxyl bending, and OH stretching vibrations of adsorbed water molecules, respectively, further confirming the successful functionalization of the material \u003csup\u003e\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Sec15\" class=\"Section3\"\u003e\n \u003ch2\u003e3.1.2. X-ray Diffraction (XRD) Analysis\u003c/h2\u003e\n \u003cp\u003eXRD was employed to evaluate the crystallographic modifications induced by functionalization. Following the oxidation and exfoliation of graphite via sonication, GO was formed, exhibiting a characteristic diffraction peak to a low reflection angle of 10.78\u0026ordm;, which is associated with the presence of oxygen-rich functional groups, as shown in Fig. \u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea. The XRD pattern of TBAB-functionalized GO (Fig. \u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eb\u003cstrong\u003e)\u003c/strong\u003e shows a pronounced structural transformation, evidenced by the disappearance of the characteristic peak at ~\u0026thinsp;10\u0026deg;, corresponding to oxygenated functional groups (e.g., OH, C\u0026ndash;O\u0026ndash;C, and COOH). In contrast, a new diffraction peak appears at 24.8\u0026deg;, indexed to the (311) plane, indicating significant structural reorganization induced by TBAB functionalization \u003csup\u003e\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\n \u003cp\u003eAs shown in Fig. \u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ec, hydrothermal treatment of the GO dispersion with HF at 180\u0026deg;C for 30 h results in the disappearance of the GO peak at 10.8\u0026deg; and the emergence of a broad diffraction peak centered at approximately 24.7\u0026deg;, corresponding to an interlayer spacing of 0.52 nm. This shift indicates effective removal of oxygen-containing functional groups and the partial restoration of the graphene framework. Upon further addition of HF, the resulting fluorinated graphene exhibits an additional diffraction peak at approximately 15.1\u0026deg;, with an interlayer spacing of 0.72 nm. This peak, assigned to the (001) plane of a hexagonal lattice, reflects a high degree of fluorine incorporation within the graphene structure \u003csup\u003e\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e, \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\n \u003cp\u003eThe XRD pattern of Li-functionalized MWCNTs (Fig. \u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ed\u003cstrong\u003e)\u003c/strong\u003e displays a prominent diffraction peak at 25.58\u0026deg;, corresponding to the (002) plane of MWCNTs, which is characteristic of the graphitic structure. Following LiF functionalization, additional diffraction peaks are observed at 17.1\u0026deg;, 36.2\u0026deg;, 43.2\u0026deg;, and 69.3\u0026deg;, which can be indexed to the characteristic reflections of LiF. The appearance of these peaks confirms the successful incorporation of LiF into the MWCNT framework and indicates enhanced crystallinity of the functionalized material \u003csup\u003e\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e, \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Sec16\" class=\"Section3\"\u003e\n \u003ch2\u003e3.1.3. XPS Analysis\u003c/h2\u003e\n \u003cp\u003eXPS was conducted to investigate the surface composition and chemical states of Li-MWCNTs, G-TBAB, and FG. For Li-MWCNTs (Fig. \u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e3\u003c/span\u003ea\u003cstrong\u003e)\u003c/strong\u003e, the survey spectrum confirms the presence of Li, C, and O. The high-resolution Li 1s spectrum exhibits two distinct peaks at approximately 52.5 eV and 55.0 eV, which are attributed to Li\u003csup\u003e+\u003c/sup\u003e species associated with Li\u0026ndash;O bonding and more highly oxidized lithium environments, respectively. The O 1s spectrum displays three components at 530.5 eV (C\u0026thinsp;=\u0026thinsp;O), 531.4 eV (C\u0026ndash;O), and 532.8 eV (O\u0026ndash;C\u0026thinsp;=\u0026thinsp;O), indicating the presence of multiple oxygen-containing functional groups that facilitate lithium anchoring on the MWCNT surface \u003csup\u003e\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e\u003c/sup\u003e. The C 1s spectrum reveals characteristic peaks at 284.5 eV (\u003cem\u003esp\u003c/em\u003e\u003csup\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sup\u003e C\u0026thinsp;=\u0026thinsp;C), 285.5 eV (\u003cem\u003esp\u003c/em\u003e\u003csup\u003e\u003cem\u003e3\u003c/em\u003e\u003c/sup\u003e C\u0026ndash;C/C\u0026ndash;H), 286.3 eV (C\u0026ndash;O), and 290.5 eV (O\u0026ndash;C\u0026thinsp;=\u0026thinsp;O), confirming preservation of the graphitic framework alongside surface functionalization \u003csup\u003e\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\n \u003cp\u003eFor G-TBAB (Fig. \u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e3\u003c/span\u003eb\u003cstrong\u003e)\u003c/strong\u003e, the survey spectrum confirms the presence of C, O, N, and Br, indicating successful incorporation of TBAB. The high-resolution C 1s spectrum shows peaks at 284.6 eV (C\u0026thinsp;=\u0026thinsp;C), 285.2 eV (C\u0026ndash;N), 286.5 eV (C\u0026thinsp;=\u0026thinsp;O), and 288.3 eV (O\u0026ndash;C\u0026thinsp;=\u0026thinsp;O), consistent with nitrogen-containing functional groups introduced during functionalization. The O 1s region exhibits components at 531.0 eV (C\u0026thinsp;=\u0026thinsp;O), 532.6 eV (C\u0026ndash;O), and 536.4 eV (O\u0026ndash;OH) \u003csup\u003e\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e\u003c/sup\u003e. The N 1s spectrum reveals contributions from pyrolytic, graphitic, and oxidized nitrogen species at binding energies of 399.8, 401.9, and 405.4 eV, respectively \u003csup\u003e\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e\u003c/sup\u003e. In addition, the Br 3d spectrum confirms bromine incorporation, displaying characteristic doublet peaks at 61.2 eV (3d\u003csub\u003e5/2\u003c/sub\u003e) and 68.9 eV (3d\u003csub\u003e3/2\u003c/sub\u003e), along with higher binding energy features.\u003c/p\u003e\n \u003cp\u003eFor FG (Fig. \u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e3\u003c/span\u003ec\u003cstrong\u003e)\u003c/strong\u003e, the survey spectrum confirms the presence of C, O, N, and F. The O 1s spectrum exhibits peaks at 531.3 eV (C\u0026thinsp;=\u0026thinsp;O), 533.1 eV (C\u0026ndash;O), and 535.6 eV (O\u0026ndash;C\u0026thinsp;=\u0026thinsp;O). The N 1s spectrum shows four components at 395.5 eV (pyrrolic N), 398.6 eV (pyridinic N), 399.9 eV (aminic N), and 401.2 eV (graphitic N), indicating nitrogen incorporated in multiple chemical environments \u003csup\u003e\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e\u003c/sup\u003e. The high-resolution C 1s spectrum displays peaks at 284.4 eV (\u003cem\u003esp\u003c/em\u003e\u003csup\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sup\u003e C\u0026thinsp;=\u0026thinsp;C), 284.9 eV (\u003cem\u003esp\u003c/em\u003e\u003csup\u003e\u003cem\u003e3\u003c/em\u003e\u003c/sup\u003e C\u0026ndash;C), 285.8 eV (C\u0026ndash;N/C\u0026ndash;O), and 288.0 eV (C\u0026thinsp;=\u0026thinsp;O), confirming the structural integrity of the graphene lattice alongside the presence of oxygen- and nitrogen-containing functional groups \u003csup\u003e\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\n \u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec17\" class=\"Section2\"\u003e\n \u003ch2\u003e3.2. Morphological and Structural Analysis\u003c/h2\u003e\n \u003cdiv id=\"Sec18\" class=\"Section3\"\u003e\n \u003ch2\u003e3.2.1. Scanning electron microscopy (SEM)\u003c/h2\u003e\n \u003cp\u003eScanning electron microscopy (SEM) revealed distinct morphological differences among the functionalized materials, as shown in Fig. \u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e4\u003c/span\u003e. The G-TBAB sample exhibits a flake-like morphology with reduced aggregation, which can be attributed to steric hindrance induced by tetrabutylammonium groups. In contrast, fluorinated graphene (FG) displays a more compact layered structure, consistent with increased structural rigidity resulting from fluorine incorporation. Li-MWCNTs retain their characteristic tubular morphology, with LiF crystallites uniformly distributed on the outer surfaces of the nanotubes.\u003c/p\u003e\n \u003cp\u003eAs shown in Fig. \u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e4\u003c/span\u003ea, G-TBAB exhibits a layered architecture interspersed with flake-like features, suggesting partial exfoliation and separation of graphene sheets. The presence of bulky tetrabutylammonium moieties likely inhibits restacking by introducing steric barriers between adjacent layers. EDX mapping further confirms successful functionalization through the detection of both nitrogen and bromine. The partially retained layered morphology may promote efficient electron transport pathways, enhancing the suitability of G-TBAB for electrochemical applications.\u003c/p\u003e\n \u003cp\u003eThe SEM images of Li-MWCNTs (Fig. \u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e4\u003c/span\u003eb\u003cstrong\u003e)\u003c/strong\u003e reveal an interconnected network of entangled nanotubes with smooth surfaces, characteristic of MWCNT assemblies. The nanotubes appear as dense bundles, and no noticeable structural damage or fragmentation is observed, indicating that the functionalization process preserves the structural integrity of the MWCNTs. EDX mapping confirms the presence of carbon, oxygen, and fluorine. However, lithium is not detected due to its low atomic number and the inherent limitations of EDX in detecting light elements such as lithium.\u003c/p\u003e\n \u003cp\u003eSEM analysis of FG (Fig. \u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e4\u003c/span\u003ec\u003cstrong\u003e)\u003c/strong\u003e reveals a sheet-like morphology with well-defined flake characteristics, indicative of exfoliated graphene layers. EDX spectra confirm the presence of fluorine, providing direct evidence of successful fluorine doping within the graphene framework.\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Sec19\" class=\"Section3\"\u003e\n \u003ch2\u003e3.2.2. Transmission electron microscopy (TEM)\u003c/h2\u003e\n \u003cp\u003eTEM analysis reveals distinct structural features of graphene oxide (GO) and its functionalized derivatives. GO exhibit disordered, wrinkled, and folded sheet-like morphologies with an expanded interlayer spacing of approximately 0.84 nm, arising from the introduction of oxygen-containing functional groups that disrupt the planner \u003cem\u003esp\u003c/em\u003e\u003csup\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sup\u003e carbon lattice. In contrast, FG displays comparatively flatter and more rigid sheets with localized lattice distortion and a reduced interlayer spacing of approximately 0.36 nm, confirming partial fluorination without extensive structural damage. Similarly, G-TBAB presents well-dispersed flake-like structures with an interlayer spacing of ~\u0026thinsp;0.36 nm, indicative of reduced aggregation and partial restoration of graphene stacking. Li-MWCNTs retain their characteristic tubular morphology, with localized surface roughness attributed to LiF incorporation, while preserving the integrity of the nanotube core structure without disrupting the core structure.\u003c/p\u003e\n \u003cp\u003eFigure \u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e5\u003c/span\u003e presents high-resolution TEM (HR-TEM) images of GO and the functionalized carbon-based derivatives. As shown in Fig. \u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e5\u003c/span\u003ea \u003cstrong\u003eand b\u003c/strong\u003e, GO exhibits wrinkling and folding, accompanied by an amorphous region, resulting from the presence of hydroxyl, epoxy, and carboxyl groups. These oxygen functionalities expand the interlayer spacing to approximately 0.84 nm, compared to ~\u0026thinsp;0.34 nm in pristine graphene, and introduce a high density of structural defects that disrupt the long-range \u003cem\u003esp\u0026sup2;\u003c/em\u003e ordering. In Comparison, the HR-TEM images of FG (Fig. \u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e5\u003c/span\u003ec \u003cstrong\u003eand d\u003c/strong\u003e), reveal a more ordered and layered morphology, reflecting enhanced structure rigidity induced by fluorine incorporation. The strong electronegativity of fluorine stabilizes the graphene layers and suppresses excessive curling. The observed lattice spacing of ~\u0026thinsp;0.35\u0026ndash;0.37 nm indicates low-to-moderate fluorine doping, accompanied by minor, localized defects, while largely preserving the graphene lattice. This controlled functionalization enhances thermal stability, chemical resistance, and surface energy, rendering FG attractive for applications such as supercapacitors and solid lubrication.\u003c/p\u003e\n \u003cp\u003eThe G-TBAB sample (Fig. \u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e5\u003c/span\u003ee \u003cstrong\u003eand f\u003c/strong\u003e) exhibits a dispersed, flake-like morphology with significantly reduced aggregation. The interlayer spacing\u0026thinsp;~\u0026thinsp;0.36 nm suggests partial recovery of the graphene framework following functionalization. The relatively uniform attachments of TBAB molecules contribute to improved dispersion and fewer large-scale defects. However, the noncovalent nature of TBAB-graphene interactions may result in weaker interfacial stability, potentially limiting long-term durability under harsh operating conditions.\u003c/p\u003e\n \u003cp\u003eFinally, Li-MWCNTs (Fig. \u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e5\u003c/span\u003eg \u003cstrong\u003eand h\u003c/strong\u003e) display a well-defined tubular morphology with concentric graphitic layers. The interlayer spacing remains approximately 0.34 nm, while the outer walls exhibit slight expansion due to LiF intercalation and surface interactions.\u003c/p\u003e\n \u003cp\u003eLocalized structural disorder appears near the doped region; however, the nanotube cores remain largely intact, preserving their intrinsic mechanical strength and electrical conductivity. This combination of structural integrity and localized lithium functionalization highlights the potential of Li-MWCNTs for advanced electrochemical energy storage and electronic applications.\u003c/p\u003e\n \u003cp\u003eA comparative summary of the structural characteristics of GO and its functionalization derivatives, including surface morphology, interlayer spacing, defect density, and associated electronic properties, is provided in Table \u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e.\u003c/p\u003e\n \u003cp\u003e\u003c/p\u003e\u0026nbsp;\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eHR-TEM features of GO, FG, G-TBAB, and Li-MWCNTs\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\" colname=\"c1\"\u003e\n \u003cp\u003eFeature\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colname=\"c2\"\u003e\n \u003cp\u003eGO\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003eFG\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colname=\"c4\"\u003e\n \u003cp\u003eG-TBAB\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colname=\"c5\"\u003e\n \u003cp\u003eLi-MWCNTs\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c1\"\u003e\n \u003cp\u003e\u003cstrong\u003eMorphology\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c2\"\u003e\n \u003cp\u003eWrinkled, disordered\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003eRigid, layered\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c4\"\u003e\n \u003cp\u003eDispersed, flake-like\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c5\"\u003e\n \u003cp\u003eTubular, concentric\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c1\"\u003e\n \u003cp\u003e\u003cstrong\u003eLattice Spacing (nm)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c2\"\u003e\n \u003cp\u003e~\u0026thinsp;0.84\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003e~\u0026thinsp;0.35\u0026ndash;0.37\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c4\"\u003e\n \u003cp\u003e~\u0026thinsp;0.36\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c5\"\u003e\n \u003cp\u003e~\u0026thinsp;0.34 (inner), ~\u0026thinsp;0.36 (outer)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c1\"\u003e\n \u003cp\u003e\u003cstrong\u003eDefects\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c2\"\u003e\n \u003cp\u003eHigh (oxidation defects)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003eScattered (fluorine)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c4\"\u003e\n \u003cp\u003eFew-layered, fewer defects\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c5\"\u003e\n \u003cp\u003eLocalized (outer walls)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c1\"\u003e\n \u003cp\u003e\u003cstrong\u003eStructural Integrity\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c2\"\u003e\n \u003cp\u003eDisrupted\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003eWell-maintained\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c4\"\u003e\n \u003cp\u003eStable and well-dispersed\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c5\"\u003e\n \u003cp\u003eStrong core, local defects\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c1\"\u003e\n \u003cp\u003e\u003cstrong\u003eFunctional Impact\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c2\"\u003e\n \u003cp\u003eInsulating\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003eImproved thermal stability\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c4\"\u003e\n \u003cp\u003eImproved solubility\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c5\"\u003e\n \u003cp\u003eEnhanced electrochemical properties\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003cp\u003e\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Sec20\" class=\"Section3\"\u003e\n \u003ch2\u003e3.2.3. AFM characterizations\u003c/h2\u003e\n \u003cp\u003eAtomic force microscopy (AFM) images acquired over a scan area of 313 nm \u0026times; 313 nm provide detailed insight into the surface morphology of GO and its chemically modified derivatives: FG, G-TBAB, and Li-MWCNTs. As shown in Fig. \u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e6\u003c/span\u003ea, GO exhibits a relatively smooth and homogeneous surface, with a narrow height distribution ranging from approximately\u0026thinsp;\u0026minus;\u0026thinsp;1.02 nm to 1.6 nm. This low roughness is characteristic of GO and reflects its layered morphology, decorated with oxygen-containing functional groups that promote a relatively flat surface profile \u003csup\u003e\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\n \u003cp\u003eIn contrast, FG (Fig. \u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e6\u003c/span\u003eb\u003cstrong\u003e)\u003c/strong\u003e exhibits a pronounced increase in surface roughness, with height variations spanning from \u0026minus;\u0026thinsp;28.8 nm to 37.6 nm over the same scan area. This pronounced roughness indicates that fluorine functionalization introduces surface defects and enhances vertical irregularity, likely due to lattice distortion and local disruption of the graphene sheets. Such features may also arise from partial exfoliation and wrinkling induced during the fluorination process \u003csup\u003e\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e, \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\n \u003cp\u003eThe AFM image of G-TBAB (Fig. \u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e6\u003c/span\u003ec) reveals a heterogeneous and irregular surface characterized by distinct protrusions and depressions, with height variation ranging from \u0026minus;\u0026thinsp;11.2 nm to 8.61 nm. This morphology can be attributed to the attachment of bulky tetrabutylammonium bromide moieties, which hinder graphene restacking and lead to uneven layer aggregation. The observed surface heterogeneity is consistent with previous reports on graphene functionalized with large organic cations \u003csup\u003e\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\n \u003cp\u003eLi-MWCNTs (Fig. \u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e6\u003c/span\u003ed) exhibit the most pronounced surface roughness among the investigated samples, with height variations ranging from \u0026minus;\u0026thinsp;53.2 nm to 52.8 nm. This extreme roughness reflects the inherent tubular morphology of MWCNTs combined with the effect of lithium fluoride incorporation, which introduces significant surface corrugation and structural deformation. The large vertical variations suggest strong interfacial interactions between LiF species and the carbon framework, resulting in a complex and highly textured surface topology \u003csup\u003e\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\n \u003cp\u003eOverall, AFM analysis confirms that chemical functionalization markedly alters the surface morphology of GO-derived materials. GO exhibits the smoothest and most uniform surface, whereas FG displays enhanced roughness due to fluorine-induced lattice disruption. G-TBAB shows moderate roughness associated with bulky organic functional groups, while Li-MWCNTs demonstrate the highest surface roughness owing to the combined effect of nanotube architecture and LiF doping. A quantitative summary of AFM-derived surface roughness parameters and morphological characteristics is provided in Table \u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e.\u003c/p\u003e\n \u003cp\u003e\u003c/p\u003e\u0026nbsp;\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eAFM features for GO, FG, G-TBAB, and Li-MWCNTs.\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\" colname=\"c1\"\u003e\n \u003cp\u003eParameter\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colname=\"c2\"\u003e\n \u003cp\u003eGO\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003eFG\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colname=\"c4\"\u003e\n \u003cp\u003eG-TBAB\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colname=\"c5\"\u003e\n \u003cp\u003eLi-MWCNTs\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c1\"\u003e\n \u003cp\u003e\u003cstrong\u003eSurface morphology\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c2\"\u003e\n \u003cp\u003eSmooth and homogeneous\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003eRough with increased irregularities\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c4\"\u003e\n \u003cp\u003eModerately rough with protrusions\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c5\"\u003e\n \u003cp\u003eHighly irregular with prominent surface features\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c1\"\u003e\n \u003cp\u003e\u003cstrong\u003eHeight range (nm)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c2\"\u003e\n \u003cp\u003e-1.02 to 1.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003e-28.8 to 37.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c4\"\u003e\n \u003cp\u003e-11.2 to 8.61\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c5\"\u003e\n \u003cp\u003e-53.2 to 52.8\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c1\"\u003e\n \u003cp\u003e\u003cstrong\u003eSurface roughness\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c2\"\u003e\n \u003cp\u003eLow\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003eHigh\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c4\"\u003e\n \u003cp\u003eModerate\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c5\"\u003e\n \u003cp\u003eVery High\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c1\"\u003e\n \u003cp\u003e\u003cstrong\u003eStructural characteristics\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c2\"\u003e\n \u003cp\u003eA layered structure with oxygen groups\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003eDisrupted surface due to fluorine attachment\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c4\"\u003e\n \u003cp\u003eIrregular surface due to bulky organic groups\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c5\"\u003e\n \u003cp\u003eTubular structures causing large corrugations\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c1\"\u003e\n \u003cp\u003e\u003cstrong\u003eSurface texture\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c2\"\u003e\n \u003cp\u003eFlat and uniform\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003eWrinkled with sharp peaks and valleys\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c4\"\u003e\n \u003cp\u003eRough with small bumps\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c5\"\u003e\n \u003cp\u003eComplex topology with deep pits and peaks\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c1\"\u003e\n \u003cp\u003e\u003cstrong\u003eNotable features\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c2\"\u003e\n \u003cp\u003eSmoothest surface\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003eSharp peaks and more profound valleys\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c4\"\u003e\n \u003cp\u003eDistinct protrusions and irregularity\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c5\"\u003e\n \u003cp\u003eMost dramatic roughness and tubular patterns\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003cp\u003e\u003c/p\u003e\n \u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec21\" class=\"Section2\"\u003e\n \u003ch2\u003e3.3. Optical Properties\u003c/h2\u003e\n \u003cdiv id=\"Sec22\" class=\"Section3\"\u003e\n \u003ch2\u003e3.3.1. UV-Vis Spectroscopy\u003c/h2\u003e\n \u003cp\u003eThe UV-Vis diffuse reflectance spectra (Fig. \u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e7\u003c/span\u003ea) exhibit a characteristic \u0026pi;\u0026ndash;\u0026pi;* electronic transition for all samples in the wavelength range of 236\u0026ndash;239 nm, indicative of the conjugated carbon framework. Corresponding Tauc plots (Fig. \u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e7\u003c/span\u003eb) were constructed to estimate the optical band gaps (Eg), yielding values of 2.83 eV for GO, 3.30 eV for Li-MWCNTs, 3.51 eV for FG, and 3.72 eV for G-TBAB. The systematic increase in Eg following functionalization, particularly upon halogen incorporation, confirms effective modulation of the electronic structure through chemical doping. Such band gap widening is expected to influence charge-carrier dynamics and enables tunability of light-harvesting behavior, which is advantageous for optoelectronic and photocatalytic applications \u003csup\u003e\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e\u003c/sup\u003e. Comparable trends in band-gap enlargement have been reported for other doped carbon-based composite materials engineered for enhanced photocatalytic performance \u003csup\u003e\u003cspan additionalcitationids=\"CR13 CR14\" citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Sec23\" class=\"Section3\"\u003e\n \u003ch2\u003e3.3.2. Photoluminescence (PL) Spectroscopy\u003c/h2\u003e\n \u003cp\u003eThe photoluminescence (PL) spectra (Fig. \u003cspan refid=\"Fig11\" class=\"InternalRef\"\u003e8\u003c/span\u003e) exhibit a prominent emission band centered at approximately 498 nm for GO, Li-MWCNTs, and FG, which is commonly attributed to the charge recombination process associated with C\u0026ndash;C and C\u0026ndash;O electronic states. In contrast, G-TBAB displays a slight red shift to ~\u0026thinsp;499 nm, accompanied by the highest PL intensity among the samples, indicating enhanced radiative recombination efficiency. This behavior suggests increased defect- or functional-group-mediated emission pathways, rendering G-TBAB potentially attractive for light-emitting and optoelectronic applications.\u003c/p\u003e\n \u003cp\u003eConversely, Li-MWCNTs showed the lowest PL intensity, implying effective suppression of charge carrier recombination and prolonged carrier lifetimes. Such characteristics are advantageous for applications requiring efficient charge separation, including photovoltaic systems and energy storage materials \u003csup\u003e\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e\u003c/sup\u003e. Although these PL trends provide valuable insights into the electronic and recombination behavior of the materials, further device-level investigations are necessary to fully assess their practical performance.\u003c/p\u003e\n \u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec24\" class=\"Section2\"\u003e\n \u003ch2\u003e3.6. Electrochemical Impedance Spectroscopy (EIS) Analysis\u003c/h2\u003e\n \u003cp\u003eEIS Nyquist plots and their corresponding fitted equivalent electrical circuit (EEC) models (Fig. \u003cspan refid=\"Fig12\" class=\"InternalRef\"\u003e9\u003c/span\u003ea and \u003cspan refid=\"Fig12\" class=\"InternalRef\"\u003e9\u003c/span\u003eb) provide detailed insight into the charge transport and interfacial processes within the fabricated films. The employed circuit model is shown as an inset, and the extracted electrochemical parameters are summarized in Table \u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e. Among the investigated materials, FG exhibits the lowest series sheet resistance (RSS\u0026thinsp;=\u0026thinsp;1.19 Ω.cm\u0026sup2;) and charge transfer resistance (RCT\u0026thinsp;=\u0026thinsp;2.54 Ω.cm\u0026sup2;), indicating highly efficient charge transport across the electrode-electrolyte interface. This superior performance can be attributed to fluorine-induced electronic modulation, where the high electronegativity of fluorine promotes charge delocalization, suppresses recombination losses, and enhances electrical conductivity \u003csup\u003e\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e, \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e\u003c/sup\u003e. In Addition, FG displays the lowest interfacial capacitance (Qc), suggesting reduced charge accumulation and rapid carrier extraction. Collectively, these characteristics make FG particularly suitable as a charge-transport layer or counter-electrode material for photovoltaic and electrocatalytic devices. In contrast, G-TBAB exhibits a higher RCT value (12.91 Ω.cm\u003csup\u003e\u0026minus;\u003c/sup\u003e\u0026sup2;), reflecting increased resistance to interfacial charge transfer. The incorporation of bulky TBAB groups likely introduces steric hindrance, which limits charge mobility across the graphene surface. Nevertheless, the moderate values of QC and RSS indicate a reasonable balance between charge transport and charge storage, consistent with other quaternary ammonium salt (QAS)- modified carbon systems reported for hybrid energy-harvesting and storage devices \u003csup\u003e\u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e45\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\n \u003cp\u003eLi-MWCNTs exhibited the highest resistance values among all samples, with RSS\u0026thinsp;=\u0026thinsp;1.70 Ω cm\u0026sup2; and RCT\u0026thinsp;=\u0026thinsp;17.73 Ω cm\u0026sup2;, implying limited electrical conductivity and sluggish charge transfer. The incorporation of LiF may introduce structural defects or charge trapping sites that impede electronic transport. However, Li-MWCNTs exhibit the highest interfacial capacitance value (QC\u0026thinsp;=\u0026thinsp;7.83 \u0026times; 10\u003csup\u003e\u0026minus;\u0026thinsp;4\u003c/sup\u003e F. cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e) along with a pronounced Warburg impedance (W\u0026thinsp;=\u0026thinsp;3.97 \u0026times; 10\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e Ω.cm\u003csup\u003e2\u003c/sup\u003e), indicative of enhanced ion diffusion and adsorption/insertion process. This electrochemical signature is characteristic of materials optimized for energy storage applications, particularly supercapacitors and battery electrodes \u003csup\u003e\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e, \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e, \u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e46\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\n \u003cp\u003e\u003c/p\u003e\u0026nbsp;\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eElectrochemical parameters from EIS fitting for thin films.\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\" colname=\"c1\"\u003e\n \u003cp\u003eParameters\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colname=\"c2\"\u003e\n \u003cp\u003eR\u003csub\u003eSS\u003c/sub\u003e\u003c/p\u003e\n \u003cp\u003e(Ω.cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003eQ\u003csub\u003eC\u003c/sub\u003e\u003c/p\u003e\n \u003cp\u003e(F.cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colname=\"c4\"\u003e\n \u003cp\u003en\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colname=\"c5\"\u003e\n \u003cp\u003eR\u003csub\u003eCT\u003c/sub\u003e\u003c/p\u003e\n \u003cp\u003e(Ω.cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colname=\"c6\"\u003e\n \u003cp\u003eW\u003c/p\u003e\n \u003cp\u003e(Ω.cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colname=\"c7\"\u003e\n \u003cp\u003eRSE\u003c/p\u003e\n \u003cp\u003e(%)\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c1\"\u003e\n \u003cp\u003e\u003cstrong\u003eG-TBAB\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\n \u003cp\u003e1.51\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003e1.76E-04\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\n \u003cp\u003e0.49\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\n \u003cp\u003e12.91\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c6\"\u003e\n \u003cp\u003e5.17E-02\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\n \u003cp\u003e7.935\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c1\"\u003e\n \u003cp\u003e\u003cstrong\u003eFG\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\n \u003cp\u003e1.19\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003e1.10E-04\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\n \u003cp\u003e0.53\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\n \u003cp\u003e2.54\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c6\"\u003e\n \u003cp\u003e3.25E-02\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\n \u003cp\u003e3.841\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c1\"\u003e\n \u003cp\u003e\u003cstrong\u003eLi-MWNCTs\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\n \u003cp\u003e1.70\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003e7.83E-04\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\n \u003cp\u003e0.48\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\n \u003cp\u003e17.73\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c6\"\u003e\n \u003cp\u003e3.97E-02\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\n \u003cp\u003e7.369\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003cp\u003e\u003c/p\u003e\n \u003cp\u003eOverall, the EIS analysis clearly differentiates the functional roles of the synthesized materials. FG demonstrates the outstanding charge transfer properties (Rct\u0026thinsp;=\u0026thinsp;2.54 Ω\u0026middot;cm\u0026sup2;), making it the most promising candidate for photovoltaic and electrocatalytic applications. G-TBAB exhibits intermediate behavior, suitable for hybrid optoelectronic systems that require a balance between transport and storage. Li-MWCNTs despite their higher resistances, show strong ion diffusion and capacitive characteristics, highlighting their potential for energy storage technologies such as supercapacitors and batteries \u003csup\u003e\u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e, \u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e46\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\n\u003c/div\u003e"},{"header":"4. Conclusions","content":"\u003cp\u003eThis work presents a systematic and comparative investigation of halogen-functionalized graphene (F and Br) and lithium-doped MWCNTs, elucidating how targeted chemical modification governs the structural, optical, and electrochemical properties of carbon nanomaterials. Comprehensive spectroscopic, microscopic, and electrochemical analyses unequivocally confirm successful doping and reveal pronounced modification in crystallinity, surface chemistry, morphology, and electronic behavior. Fluorinated graphene (FG) exhibits the most favorable charge transport characteristics, including the lowest charge transfer resistance and suppressed charge recombination, highlighting its strong potential as a charge transport or counter-electrode material in photovoltaic and high-frequency optoelectronic devices. Brominated graphene (G-TBAB) demonstrates enhanced and tunable photoluminescence combined with moderate electrochemical performance and hybrid optoelectronic applications. In contrast, Lithium-functionalized MWCNTs (Li-MWCNTs) show markedly increased interfacial capacitance and enhanced ion diffusion behavior, indicating their suitability as electrode materials for energy storage technologies, particularly supercapacitors and lithium-ion batteries. Importantly, this study establishes clear structure-property-application relationships, providing a rational framework for tailoring carbon nanomaterials toward specific energy conversion and storage functions. While the present work focuses on fundamental materials characterization, the results lay a solid foundation for future device-level investigations. Subsequent studies should address practical performance metrics, including photovoltaic efficiency, long-term electrochemical cycling stability, and rate capability, to fully assess technological viability. Furthermore, incorporation of life-cycle assessment and scalability analyses of the synthesis routes will be essential to align these advanced materials with the principles of sustainable and environmentally responsible technologies.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eContributionsA. G. A.: Conceptualization, Formal analysis, Materials characterization, Methodology, Software, Validation, Electrochemical assessment, Writing \u0026ndash; original draft, review \u0026amp; editing. W. S. G.: Methodology, Software, Materials characterization, Writing \u0026ndash; original draft. M. A. E.: Methodology, Software, Investigation, Materials characterization. A. S. M.: Investigation, Software, Validation. A. M. E.: Writing \u0026ndash; review \u0026amp; editing. K. I. K.: Conceptualization, Project administration, Resources, Supervision, Validation, Writing \u0026ndash; review \u0026amp; editing.\u003c/p\u003e\u003cp\u003e\u003cstrong\u003e*Declaration of competing interest\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis work was supported by the Science, Technology \u0026amp; Innovation Funding Authority (STDF) (47434), Egypt. \u0026nbsp;\u003c/p\u003e\u003ch2\u003eData Availability\u003c/h2\u003e\u003cp\u003eAll data supporting the findings of this study are available within the paper and its Supplementary Information.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eNovoselov, K. S.; Geim, A. K.; Morozov, S. V.; Jiang, D.-e.; Zhang, Y.; Dubonos, S. V.; Grigorieva, I. V.; Firsov, A. A. Electric field effect in atomically thin carbon films. \u003cem\u003escience \u003c/em\u003e\u003cstrong\u003e2004\u003c/strong\u003e, \u003cem\u003e306\u003c/em\u003e (5696), 666-669.\u003c/li\u003e\n\u003cli\u003eSchwierz, F. Graphene transistors. \u003cem\u003eNature nanotechnology \u003c/em\u003e\u003cstrong\u003e2010\u003c/strong\u003e, \u003cem\u003e5\u003c/em\u003e (7), 487-496.\u003c/li\u003e\n\u003cli\u003eDas, A.; Pisana, S.; Chakraborty, B.; Piscanec, S.; Saha, S. K.; Waghmare, U. V.; Novoselov, K. S.; Krishnamurthy, H. R.; Geim, A. K.; Ferrari, A. C. Monitoring dopants by Raman scattering in an electrochemically top-gated graphene transistor. \u003cem\u003eNature nanotechnology \u003c/em\u003e\u003cstrong\u003e2008\u003c/strong\u003e, \u003cem\u003e3\u003c/em\u003e (4), 210-215.\u003c/li\u003e\n\u003cli\u003eRani, P.; Jindal, V. Designing band gap of graphene by B and N dopant atoms. \u003cem\u003eRSC advances \u003c/em\u003e\u003cstrong\u003e2013\u003c/strong\u003e, \u003cem\u003e3\u003c/em\u003e (3), 802-812.\u003c/li\u003e\n\u003cli\u003eSun, X.; Zhang, Y.; Song, P.; Pan, J.; Zhuang, L.; Xu, W.; Xing, W. Fluorine-doped carbon blacks: highly efficient metal-free electrocatalysts for oxygen reduction reaction. \u003cem\u003eACS catalysis \u003c/em\u003e\u003cstrong\u003e2013\u003c/strong\u003e, \u003cem\u003e3\u003c/em\u003e (8), 1726-1729. Zhao, J.; Cabrera, C. R.; Xia, Z.; Chen, Z. Single\u0026minus; sided fluorine\u0026ndash;functionalized graphene: A metal\u0026ndash;free electrocatalyst with high efficiency for oxygen reduction reaction. \u003cem\u003eCarbon \u003c/em\u003e\u003cstrong\u003e2016\u003c/strong\u003e, \u003cem\u003e104\u003c/em\u003e, 56-63.\u003c/li\u003e\n\u003cli\u003eXue, Y.; Qi, Y.; Tong, T.; Xu, H.; Liu, Z.; Ji, C.; Zhang, J.; Gao, J.; Ma, C.; Jiang, Y. Photoluminescence and transport properties of fluorinated graphene via a weak fluorination strategy. \u003cem\u003eApplied Physics Letters \u003c/em\u003e\u003cstrong\u003e2024\u003c/strong\u003e, \u003cem\u003e124\u003c/em\u003e (18). Que, L.; Ai, J.; Shao, T.; Han, R.; Su, J.; Guo, Y.; Liu, Y.; Li, J.; Jian, X.; Zhou, Z. Fluorinated graphene films for Ultra-High sensitivity of Surface-Enhanced Raman scattering. \u003cem\u003eApplied Surface Science \u003c/em\u003e\u003cstrong\u003e2023\u003c/strong\u003e, \u003cem\u003e616\u003c/em\u003e, 156496.\u003c/li\u003e\n\u003cli\u003ePrado, D. M. S.; Li, G.; del Rosario, J. A. D.; Ocon, J. D.; Abel Chuang, P. Y. Improved Oxygen Reduction Reaction Activity of Graphene via Mechanochemical Activation and Halogen‐Doping. \u003cem\u003eChemElectroChem \u003c/em\u003e\u003cstrong\u003e2025\u003c/strong\u003e, \u003cem\u003e12\u003c/em\u003e (1), e202400494. Rabeel, M.; Kim, H.; Khan, M. A.; Abubakr, M.; Ahmad, I.; Ahmad, M.; Rehman, S.; Lee, M.-J.; Khan, M. F.; Kim, D.-k. Broadband and flexible photodiode of a bromine-doped lateral MoTe2 homojunction. \u003cem\u003eACS Photonics \u003c/em\u003e\u003cstrong\u003e2023\u003c/strong\u003e, \u003cem\u003e10\u003c/em\u003e (12), 4425-4436.\u003c/li\u003e\n\u003cli\u003eIijima, S. Helical microtubules of graphitic carbon. \u003cem\u003enature \u003c/em\u003e\u003cstrong\u003e1991\u003c/strong\u003e, \u003cem\u003e354\u003c/em\u003e (6348), 56-58. Lee, S. W.; Yabuuchi, N.; Gallant, B. M.; Chen, S.; Kim, B.-S.; Hammond, P. T.; Shao-Horn, Y. High-power lithium batteries from functionalized carbon-nanotube electrodes. \u003cem\u003eNature nanotechnology \u003c/em\u003e\u003cstrong\u003e2010\u003c/strong\u003e, \u003cem\u003e5\u003c/em\u003e (7), 531-537.\u003c/li\u003e\n\u003cli\u003eKong, L.; Zhu, Y.; Williams, P. J.; Kabbani, M.; Brushett, F. R.; Rupp, J. L. Insights into Li+ storage mechanisms, kinetics, and reversibility of defect-engineered and functionalized multi-walled carbon nanotubes for enhanced energy storage. \u003cem\u003eJournal of Materials Chemistry A \u003c/em\u003e\u003cstrong\u003e2024\u003c/strong\u003e, \u003cem\u003e12\u003c/em\u003e (7), 4299-4311. Narayan, J.; Bezborah, K. Recent advances in the functionalization, substitutional doping and applications of graphene/graphene composite nanomaterials. \u003cem\u003eRSC Advances \u003c/em\u003e\u003cstrong\u003e2024\u003c/strong\u003e, \u003cem\u003e14\u003c/em\u003e (19), 13413-13444, 10.1039/D3RA07072G. DOI: 10.1039/D3RA07072G.\u003c/li\u003e\n\u003cli\u003eKabel, K. I.; Farag, A. A.; Elnaggar, E.; Al-Gamal, A. Improvement of graphene oxide characteristics depending on base washing. \u003cem\u003eJournal of Superhard Materials \u003c/em\u003e\u003cstrong\u003e2015\u003c/strong\u003e, \u003cem\u003e37\u003c/em\u003e (5), 327-334.\u003c/li\u003e\n\u003cli\u003eWang, Z.; Wang, J.; Li, Z.; Gong, P.; Liu, X.; Zhang, L.; Ren, J.; Wang, H.; Yang, S. Synthesis of fluorinated graphene with tunable degree of fluorination. \u003cem\u003eCarbon \u003c/em\u003e\u003cstrong\u003e2012\u003c/strong\u003e, \u003cem\u003e50\u003c/em\u003e (15), 5403-5410.\u003c/li\u003e\n\u003cli\u003eKuang, H.; Liao, H.; Zhang, Z.; Huang, S.; Mao, B.; Shan, W.; Duan, X.; Feng, X.; Li, T. Dynamic diels-alder reaction crosslinked metal-organic framework/poly (ionic liquid) composite solid electrolyte for lithium-metal batteries. \u003cem\u003eJournal of Colloid and Interface Science \u003c/em\u003e\u003cstrong\u003e2025\u003c/strong\u003e, 139638.\u003c/li\u003e\n\u003cli\u003eThangavelu, K.; Rajendran, R.; Palanisamy, S.; Arumugam, P.; Thammasak, R. Powerful combination of FeWO4/g-C3N4 heterostructures for solar light driven photocatalytic degradation of tetracycline and its antibacterial activity. \u003cem\u003eMaterials Today Sustainability \u003c/em\u003e\u003cstrong\u003e2023\u003c/strong\u003e, \u003cem\u003e24\u003c/em\u003e, 100562.\u003c/li\u003e\n\u003cli\u003eAkechatree, N.; Rajendran, R.; Rojviroon, T.; Arumugam, P.; Vasudevan, V.; Sirivithayapakorn, S.; Dhayalan, A.; Wongpipun, P.; Phetyim, N.; Rojviroon, O. Development of Z-scheme BiVO4/g-C3N4/rGO heterojunction nanocomposite for enhanced photocatalytic degradation and antibacterial activity. \u003cem\u003eMaterials Research Bulletin \u003c/em\u003e\u003cstrong\u003e2025\u003c/strong\u003e, \u003cem\u003e181\u003c/em\u003e, 113119.\u003c/li\u003e\n\u003cli\u003eThankulkit, P.; Rojviroon, O.; Rajendran, R.; Alsawalha, M.; Arumugam, P.; Rojviroon, T.; Sirivithayapakorn, S. Development of AgFeO2/g-C3N4/RGO nanocomposites with superior photocatalytic activity and antibacterial properties for wastewater treatment. \u003cem\u003eJournal of Water Process Engineering \u003c/em\u003e\u003cstrong\u003e2025\u003c/strong\u003e, \u003cem\u003e69\u003c/em\u003e, 106650.\u003c/li\u003e\n\u003cli\u003eRajendran, R.; Rojviroon, O.; Vasudevan, V.; Arumugam, P.; Handayani, M.; Akechatree, N.; Leelert, Y.; Rojviroon, T. Magnetically separable ternary heterostructure photocatalyst CuFe2O4/g-C3N4/rGO: Enhancing photocatalytic degradation and bacterial inactivation. \u003cem\u003eJournal of Water Process Engineering \u003c/em\u003e\u003cstrong\u003e2024\u003c/strong\u003e, \u003cem\u003e63\u003c/em\u003e, 105443.\u003c/li\u003e\n\u003cli\u003ePriyadharsan, A.; Kamaraj, C.; Ranjith, R.; Sivakumar, S.; Dewiani, R. Y.; Thammasak, R.; Periyasami, G.; Murni, H. Synthesis of multifunctional rGO/g-C3N4/FeTiO3 ternary nanocomposites for photocatalyst, antibacterial, and ecotoxicity assessment of zebrafish embryo model. \u003cem\u003eJournal of Alloys and Compounds \u003c/em\u003e\u003cstrong\u003e2024\u003c/strong\u003e, \u003cem\u003e1007\u003c/em\u003e, 176256.\u003c/li\u003e\n\u003cli\u003eWongwichian, S.; Rajendran, R.; Rojviroon, O.; Arumugam, P.; Sirivithayapakorn, S.; Rojviroon, T. Micro-nanobubble assisted photocatalytic and antibacterial activity of ZnFe2O4/g-C3N4/rGO nanocomposite. \u003cem\u003eEnvironmental Nanotechnology, Monitoring \u0026amp; Management \u003c/em\u003e\u003cstrong\u003e2025\u003c/strong\u003e, \u003cem\u003e23\u003c/em\u003e, 101065.\u003c/li\u003e\n\u003cli\u003eYalcinkaya, F. N.; Doğan, M.; Bicil, Z.; Kizilduman, B. K. Effect of functionalization and Li-doping methods to hydrogen storage capacities of MWCNTs. \u003cem\u003eFuel \u003c/em\u003e\u003cstrong\u003e2024\u003c/strong\u003e, \u003cem\u003e372\u003c/em\u003e, 132274.\u003c/li\u003e\n\u003cli\u003eHocker, S.; Hudson-Smith, N.; Schniepp, H. C.; Kranbuehl, D. E. Enhancing polyimide\u0026apos;s water barrier properties through addition of functionalized graphene oxide. \u003cem\u003ePolymer \u003c/em\u003e\u003cstrong\u003e2016\u003c/strong\u003e, \u003cem\u003e93\u003c/em\u003e, 23-29.\u003c/li\u003e\n\u003cli\u003eFerreira, F. V.; Cividanes, L. D. S.; Brito, F. S.; de Menezes, B. R. C.; Franceschi, W.; Simonetti, E. A. N.; Thim, G. P. Functionalization of graphene and applications. In \u003cem\u003eFunctionalizing graphene and carbon nanotubes: a review\u003c/em\u003e, Springer, 2016; pp 1-29.\u003c/li\u003e\n\u003cli\u003eGuo, H.; Liu, F.; Zhao, J.; Yao, H.; Jin, R.; Kang, C.; Bian, Z.; Qiu, X.; Gao, L. In situ iodoalkane-reduction of graphene oxide in a polymer matrix: An easy and effective approach for the fabrication of conductive composites. \u003cem\u003eJournal of Materials Chemistry C \u003c/em\u003e\u003cstrong\u003e2015\u003c/strong\u003e, \u003cem\u003e3\u003c/em\u003e (43), 11531-11539.\u003c/li\u003e\n\u003cli\u003eMokgohloa, M.; Ogunlaja, A. S. Synthesis and characterization of ethylenediamine functionalized graphene oxide-modified UiO-66-NH2 for quinoline removal. \u003cem\u003eCarbon Letters \u003c/em\u003e\u003cstrong\u003e2022\u003c/strong\u003e, \u003cem\u003e32\u003c/em\u003e (7), 1689-1702.\u003c/li\u003e\n\u003cli\u003eZhang, K.; Mao, L.; Zhang, L. L.; Chan, H. S. O.; Zhao, X. S.; Wu, J. Surfactant-intercalated, chemically reduced graphene oxide for high performance supercapacitor electrodes. \u003cem\u003eJournal of Materials Chemistry \u003c/em\u003e\u003cstrong\u003e2011\u003c/strong\u003e, \u003cem\u003e21\u003c/em\u003e (20), 7302-7307.\u003c/li\u003e\n\u003cli\u003eNebogatikova, N.; Antonova, I.; Prinz, V. Y.; Kurkina, I.; Vdovin, V.; Aleksandrov, G.; Timofeev, V.; Smagulova, S.; Zakirov, E.; Kesler, V. Fluorinated graphene dielectric films obtained from functionalized graphene suspension: preparation and properties. \u003cem\u003ePhysical Chemistry Chemical Physics \u003c/em\u003e\u003cstrong\u003e2015\u003c/strong\u003e, \u003cem\u003e17\u003c/em\u003e (20), 13257-13266.\u003c/li\u003e\n\u003cli\u003eKang, W.; Li, S. Preparation of fluorinated graphene to study its gas sensitivity. \u003cem\u003eRSC advances \u003c/em\u003e\u003cstrong\u003e2018\u003c/strong\u003e, \u003cem\u003e8\u003c/em\u003e (41), 23459-23467.\u003c/li\u003e\n\u003cli\u003eKonni, M.; Kumar Karnena, M.; Babu Mukkamala, S. Enhanced Room‐Temperature Synthesis of Li@ f‐MWCNTs for Hydrogen Storage Application. \u003cem\u003eChemistrySelect \u003c/em\u003e\u003cstrong\u003e2020\u003c/strong\u003e, \u003cem\u003e5\u003c/em\u003e (14), 4292-4296.\u003c/li\u003e\n\u003cli\u003eTiwari, A.; Singh, V. Synthesis and characterization of electrical conducting chitosan-graft-polyaniline. \u003cem\u003eExpress Polymer Letters \u003c/em\u003e\u003cstrong\u003e2007\u003c/strong\u003e, \u003cem\u003e1\u003c/em\u003e (5), 308-317. Gomez, N. A. G.; Maruyama, S. A.; Leuteritz, A.; Wypych, F. Composites of polyethylene and layered cobalt hydroxide salts as potential ultraviolet radiation absorbers. \u003cem\u003ePolymer Bulletin \u003c/em\u003e\u003cstrong\u003e2020\u003c/strong\u003e, \u003cem\u003e77\u003c/em\u003e (1), 255-273.\u003c/li\u003e\n\u003cli\u003eIbrahim, A. I.; Onaizi, S. A.; Vohra, M. S. Novel CTAB functionalized graphene oxide for selenium removal: adsorption results and ANN \u0026amp; RSM modeling. \u003cem\u003eEmergent Materials \u003c/em\u003e\u003cstrong\u003e2024\u003c/strong\u003e, \u003cem\u003e7\u003c/em\u003e (2), 547-564.\u003c/li\u003e\n\u003cli\u003eGu\u0026eacute;rin, K.; Pinheiro, J.; Dubois, M.; Fawal, Z.; Masin, F.; Yazami, R.; Hamwi, A. Synthesis and characterization of highly fluorinated graphite containing sp2 and sp3 carbon. \u003cem\u003eChemistry of materials \u003c/em\u003e\u003cstrong\u003e2004\u003c/strong\u003e, \u003cem\u003e16\u003c/em\u003e (9), 1786-1792.\u003c/li\u003e\n\u003cli\u003eLiang, G.; Sun, X.; Lai, J.; Wei, C.; Huang, Y.; Hu, H. Adding lithium fluoride to improve the electrochemical properties SnO2@ C/MWCNTs composite anode for lithium-ion batteries. \u003cem\u003eJournal of Electroanalytical Chemistry \u003c/em\u003e\u003cstrong\u003e2019\u003c/strong\u003e, \u003cem\u003e853\u003c/em\u003e, 113401.\u003c/li\u003e\n\u003cli\u003eZhao, J.; Zhai, X.; Tao, X.; Liu, H.; Liu, W.; Jiang, D.; Gao, S. Effect of MWCNTs and lithium modified MWCNTs on electrochemical hydrogen storage properties of Co0. 9Cu0. 1Si alloy. \u003cem\u003eInternational Journal of Hydrogen Energy \u003c/em\u003e\u003cstrong\u003e2018\u003c/strong\u003e, \u003cem\u003e43\u003c/em\u003e (29), 13383-13392.\u003c/li\u003e\n\u003cli\u003eEl-Khair, M. A. A.; Al-Gamal, A. G.; Kabel, K. I.; Gado, W. S.; Morshedy, A. S. Harvesting the synergistic effect of CuFe2O4@Ni-MOF nanomagnetic photocatalyst for enhanced visible light-driven green hydrogen production. \u003cem\u003eInternational Journal of Hydrogen Energy \u003c/em\u003e\u003cstrong\u003e2025\u003c/strong\u003e, \u003cem\u003e101\u003c/em\u003e, 280-294. DOI: https://doi.org/10.1016/j.ijhydene.2024.12.449.\u003c/li\u003e\n\u003cli\u003eEl-Khair, M. A. A.; Hanafi, S. A.; Abd El-Moghny, M. G.; El Saied, M.; Elmelawy, M. S.; El-Deab, M. S. Boosted Bio-Jet production: Unveiling the potential of a one-stage concurrent process of deoxygenation/upgrading versus two-stage sequential processes using Pt/Cl-Al2O3@ Ni/ZSM-5 catalysts. \u003cem\u003eChemical Engineering Journal \u003c/em\u003e\u003cstrong\u003e2024\u003c/strong\u003e, \u003cem\u003e490\u003c/em\u003e, 151716.\u003c/li\u003e\n\u003cli\u003eJankovsk\u0026yacute;, O.; \u0026Scaron;imek, P.; Klimova, K.; Sedmidubsk\u0026yacute;, D.; Matějkov\u0026aacute;, S.; Pumera, M.; Sofer, Z. Towards graphene bromide: bromination of graphite oxide. \u003cem\u003eNanoscale \u003c/em\u003e\u003cstrong\u003e2014\u003c/strong\u003e, \u003cem\u003e6\u003c/em\u003e (11), 6065-6074.\u003c/li\u003e\n\u003cli\u003ePace, G.; Serri, M.; del Rio Castillo, A. E.; Ansaldo, A.; Lauciello, S.; Prato, M.; Pasquale, L.; Luxa, J.; Maz\u0026aacute;nek, V.; Sofer, Z. Nitrogen-doped graphene based triboelectric nanogenerators. \u003cem\u003eNano Energy \u003c/em\u003e\u003cstrong\u003e2021\u003c/strong\u003e, \u003cem\u003e87\u003c/em\u003e, 106173.\u003c/li\u003e\n\u003cli\u003eTeklu, A.; Barry, C.; Palumbo, M.; Weiwadel, C.; Kuthirummal, N.; Flagg, J. Mechanical characterization of reduced graphene oxide using AFM. \u003cem\u003eAdvances in Condensed Matter Physics \u003c/em\u003e\u003cstrong\u003e2019\u003c/strong\u003e, \u003cem\u003e2019\u003c/em\u003e (1), 8713965.\u003c/li\u003e\n\u003cli\u003eZeng, X.; Peng, Y.; Yu, M.; Lang, H.; Cao, X. a.; Zou, K. Dynamic sliding enhancement on the friction and adhesion of graphene, graphene oxide, and fluorinated graphene. \u003cem\u003eACS applied materials \u0026amp; interfaces \u003c/em\u003e\u003cstrong\u003e2018\u003c/strong\u003e, \u003cem\u003e10\u003c/em\u003e (9), 8214-8224.\u003c/li\u003e\n\u003cli\u003eGorji, Z. E.; Khodadadi, A. A.; Riahi, S.; Repo, T.; Mortazavi, Y.; Kemell, M. Functionalization of nitrogen-doped graphene quantum dot: A sustainable carbon-based catalyst for the production of cyclic carbonate from epoxide and CO2. \u003cem\u003eJournal of Environmental Sciences \u003c/em\u003e\u003cstrong\u003e2023\u003c/strong\u003e, \u003cem\u003e126\u003c/em\u003e, 408-422. DOI: https://doi.org/10.1016/j.jes.2022.04.046. Heydari, P.; Hafizi, A.; Rahimpour, M.; Khalifeh, R. Experimental investigation of improved graphene oxide as an efficient catalyst for the sustainable chemical fixation of CO2 with epoxides. \u003cem\u003eJournal of Environmental Chemical Engineering \u003c/em\u003e\u003cstrong\u003e2020\u003c/strong\u003e, \u003cem\u003e8\u003c/em\u003e (6), 104568.\u003c/li\u003e\n\u003cli\u003eLiu, W.; Deng, N.; Wang, G.; Yu, R.; Wang, X.; Cheng, B.; Ju, J.; Kang, W. Fluoridation routes, function mechanism and application of fluorinated/fluorine-doped nanocarbon-based materials for various batteries: A review. \u003cem\u003eJournal of Energy Chemistry \u003c/em\u003e\u003cstrong\u003e2023\u003c/strong\u003e, \u003cem\u003e85\u003c/em\u003e, 363-393. DOI: https://doi.org/10.1016/j.jechem.2023.06.020.\u003c/li\u003e\n\u003cli\u003eAl-khattib, M.; Samir, A.; Morgan, N. N.; Hassablla, S. Synthesis, Structure Parameters and Optical Properties of Graphite and Graphene Oxide Sheet. Hunt, A.; Kurmaev, E.; Moewes, A. Band gap engineering of graphene oxide by chemical modification. \u003cem\u003eCarbon \u003c/em\u003e\u003cstrong\u003e2014\u003c/strong\u003e, \u003cem\u003e75\u003c/em\u003e, 366-371.\u003c/li\u003e\n\u003cli\u003eNjema, G. G.; Kibet, J. K. A review of chalcogenide-based perovskites as the next novel materials: Solar cell and optoelectronic applications, catalysis and future perspectives. \u003cem\u003eNext Nanotechnology \u003c/em\u003e\u003cstrong\u003e2025\u003c/strong\u003e, \u003cem\u003e7\u003c/em\u003e, 100102.\u003c/li\u003e\n\u003cli\u003eVillarreal, C. C.; Sandoval, J. I.; Ramnani, P.; Terse-Thakoor, T.; Vi, D.; Mulchandani, A. Graphene compared to fluorine-doped tin oxide as transparent conductor in ZnO dye-sensitized solar cells. \u003cem\u003eJournal of Environmental Chemical Engineering \u003c/em\u003e\u003cstrong\u003e2022\u003c/strong\u003e, \u003cem\u003e10\u003c/em\u003e (3), 107551. Kim, S.-H.; Lee, C.-H.; Yun, J.-M.; Noh, Y.-J.; Kim, S.-S.; Lee, S.; Jo, S. M.; Joh, H.-I.; Na, S.-I. Fluorine-functionalized and simultaneously reduced graphene oxide as a novel hole transporting layer for highly efficient and stable organic photovoltaic cells. \u003cem\u003eNanoscale \u003c/em\u003e\u003cstrong\u003e2014\u003c/strong\u003e, \u003cem\u003e6\u003c/em\u003e (13), 7183-7187, 10.1039/C4NR01038H. DOI: 10.1039/C4NR01038H. Yu, X.; Yang, L.; Lv, Q.; Xu, M.; Chen, H.; Yang, D. The enhanced efficiency of graphene\u0026ndash;silicon solar cells by electric field doping. \u003cem\u003eNanoscale \u003c/em\u003e\u003cstrong\u003e2015\u003c/strong\u003e, \u003cem\u003e7\u003c/em\u003e (16), 7072-7077, 10.1039/C4NR06677D. DOI: 10.1039/C4NR06677D.\u003c/li\u003e\n\u003cli\u003eSim, Y.; Surendran, S.; Cha, H.; Choi, H.; Je, M.; Yoo, S.; Seok, D. C.; Jung, Y. H.; Jeon, C.; Kim, D. J. Fluorine-doped graphene oxide prepared by direct plasma treatment for supercapacitor application. \u003cem\u003eChemical Engineering Journal \u003c/em\u003e\u003cstrong\u003e2022\u003c/strong\u003e, \u003cem\u003e428\u003c/em\u003e, 132086.\u003c/li\u003e\n\u003cli\u003eRoy-Mayhew, J. D.; Aksay, I. A. Graphene materials and their use in dye-sensitized solar cells. \u003cem\u003eChemical reviews \u003c/em\u003e\u003cstrong\u003e2014\u003c/strong\u003e, \u003cem\u003e114\u003c/em\u003e (12), 6323-6348. Kuppu, S. V.; Senthilkumaran, M.; Sethuraman, V.; Balaji, M.; Saravanan, C.; Ahmed, N.; Mohandoss, S.; Lee, Y. R.; Anandharaj, J.; Stalin, T. The surfactants mediated electropolymerized poly (aniline)(PANI)-reduced graphene oxide (rGO) composite counter electrode for dye-sensitized solar cell. \u003cem\u003eJournal of Physics and Chemistry of Solids \u003c/em\u003e\u003cstrong\u003e2023\u003c/strong\u003e, \u003cem\u003e173\u003c/em\u003e, 111121. Mohamed, N. B.; El‐Kady, M. F.; Kaner, R. B. Macroporous graphene frameworks for sensing and supercapacitor applications. \u003cem\u003eAdvanced Functional Materials \u003c/em\u003e\u003cstrong\u003e2022\u003c/strong\u003e, \u003cem\u003e32\u003c/em\u003e (42), 2203101. Nurdin, I.; Fitri, H.; Widiatmoko, P.; Devianto, H.; Prakoso, T. The effect of cationic CTAB surfactants on the performance of graphene electrode for supercapacitor. In \u003cem\u003eIOP Conference Series: Materials Science and Engineering\u003c/em\u003e, 2020; IOP Publishing: Vol. 823, p 012038.\u003c/li\u003e\n\u003cli\u003eBasa, A.; Tatko, D.; Lapinska, K.; Wilczewska, A. Z.; Goclon, J.; Winkler, K.; Kuhn, A.; Garc\u0026iacute;a-Alvarado, F. Li3FeF6/Fe2O3, LiF anchored oxidized multi-wall carbon nanotubes as high power cathode in lithium ion batteries. \u003cem\u003eJournal of Power Sources \u003c/em\u003e\u003cstrong\u003e2025\u003c/strong\u003e, \u003cem\u003e630\u003c/em\u003e, 236103.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Graphene Halogen doping, Lithium-functionalized MWCNTs, Optical properties, Electrochemical impedance spectroscopy, Photoluminescence","lastPublishedDoi":"10.21203/rs.3.rs-9182061/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-9182061/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eTailoring the electronic and electrochemical properties of carbon nanomaterials through controlled chemical functionalization is critical for advancing next-generation energy and optoelectronic technologies. Herein, we present a systematic nanoscale engineering strategy based on halogen-functionalized graphene (fluorinated and brominated) integrated with lithium-modified multi-walled carbon nanotubes (MWCNTs). Graphene oxide (GO) was chemically modified using hydrofluoric acid (HF) and tetrabutylammonium bromide (TBAB) to produce fluorinated graphene (FG) and brominated graphene (G-TBAB), respectively, while MWCNTs were functionalized with lithium fluoride (LiF) to obtain Li-MWCNTs. This comparative platform establishes a unified dopant-dependent framework correlating electronegativity, bonding configuration, and interfacial nanoarchitecture with optoelectronic and electrochemical performance across distinct carbon allotropes. Comprehensive structural and chemical characterization (FTIR, XRD, XPS, SEM, TEM, AFM, UV\u0026ndash;Vis, photoluminescence spectroscopy, and electrochemical impedance spectroscopy) reveals that covalent C\u0026ndash;F bonding enhances charge transport and suppresses carrier recombination, yielding FG with the lowest charge-transfer resistance (2.54 Ω\u0026middot;cm⁻\u0026sup2;) and improved conductivity. In contrast, bromine-mediated noncovalent functionalization via TBAB induces steric and electrostatic modulation of the graphene surface, enabling tunable photoluminescence while preserving the structural integrity of the carbon framework. Furthermore, lithium functionalization of MWCNTs promotes efficient ion diffusion and interfacial charge storage, thereby enhancing capacitance and exhibiting pronounced Warburg behavior characteristic of diffusion-controlled electrochemical processes. By directly linking dopant chemistry to nanoscale interfacial phenomena and functional performance, this work introduces a dopant-selective materials design strategy for tailoring carbon nanomaterials toward photovoltaic, optoelectronic, and energy storage applications.\u003c/p\u003e","manuscriptTitle":"Dopant-Dependent Structure–Property Relationships in Functionalized Graphene and MWCNTs for Sustainable Energy Applications","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-04-16 16:10:29","doi":"10.21203/rs.3.rs-9182061/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2026-05-05T06:03:09+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-05-04T20:10:03+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-04-13T02:26:09+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"297358070643078737961616319157608161136","date":"2026-04-10T15:13:18+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"88180512995787168215589066124459606813","date":"2026-04-08T14:15:59+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-04-08T13:29:39+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-04-08T06:56:17+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2026-03-26T10:32:25+00:00","index":"","fulltext":""},{"type":"submitted","content":"Scientific Reports","date":"2026-03-26T10:26:18+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"8fc7c5e5-235b-47d2-84cc-20df9bc9ac1c","owner":[],"postedDate":"April 16th, 2026","published":true,"recentEditorialEvents":[{"type":"decision","content":"Revision requested","date":"2026-05-05T06:03:09+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-05-04T20:10:03+00:00","index":28,"fulltext":""}],"rejectedJournal":[],"revision":"","amendment":"","status":"in-revision","subjectAreas":[{"id":66254015,"name":"Physical sciences/Chemistry"},{"id":66254016,"name":"Physical sciences/Energy science and technology"},{"id":66254017,"name":"Physical sciences/Materials science"},{"id":66254018,"name":"Physical sciences/Nanoscience and technology"}],"tags":[],"updatedAt":"2026-05-05T06:09:34+00:00","versionOfRecord":[],"versionCreatedAt":"2026-04-16 16:10:29","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-9182061","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-9182061","identity":"rs-9182061","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}