Tetragonal MnO₂ Nanoparticles Synthesized via Lagerstroemia speciosa: Structural Characterization and Photocatalytic Potential

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J. Garole, Yogesh R. Toda, Ratnamala S. Bendre This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6715891/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Manganese oxide nanoparticles (MnO₂-NPs) were biosynthesized using an aqueous extract of Lagerstroemia speciosa leaf powder. The plant is rich in phytochemicals such as phenolic compounds, alkaloids, α-amino acids, steroids, organic acids, terpenoids, reducing sugars, glycosides, carbohydrates, saponins, starch, flavonoids, and tannins. The phenolic compounds acted as both reducing and capping agents. The synthesized nanoparticles were characterized using UV–Vis–IR spectroscopy, X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and Fourier-transform infrared spectroscopy (FTIR). The UV–Vis–IR spectrum revealed a distinct absorption peak at 365 nm, confirming the formation of MnO₂-NPs. FESEM images indicated rough, spherical, randomly oriented particles with sizes ranging from 83–400 nm. XRD analysis confirmed a pure tetragonal structure with preferential (110) plane orientation. The photocatalytic performance of the MnO₂-NPs was assessed via the sunlight-driven decolourization of methyl orange (MO) and bromocresol green (BCG) dyes. MnO₂-NPs green synthesis Lagerstroemia speciosa photo catalysis UV–Vis–IR XRD FESEM dye degradation Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 1. Introduction In nanotechnology, particle size plays a crucial role in determining the material’s properties. Nanoparticles exhibit unique structural, magnetic, and optical behaviours, governed by their size, shape, morphology, and composition [ 1 ]. Morphology and dimension are particularly important, as they contribute to the stability and functionality of nanoparticles [ 2 , 3 ]. Due to their high specific surface area and distinct electronic, chemical, and physical properties, metal nanoparticles especially manganese oxide nanoparticles—have broad applications in batteries, catalysts, water treatment, molecular sieves, optoelectronics, and magnetic materials [ 4 , 5 ]. Manganese oxide nanoparticles (MnO₂-NPs) are also being explored for solar cell applications due to their promising electronic and optical properties [ 6 ]. These nanoparticles can be synthesized via several techniques, including femtosecond laser ablation [ 7 ], reflux treatment [ 8 ], redox reaction [ 9 ], green synthesis [ 10 ], co-precipitation [ 11 ], and sol–gel methods [ 12 ]. Among these, green synthesis has gained attention as a sustainable, eco-friendly approach. This method utilizes plant parts leaves, stems, roots, bark, seeds or microbial agents like fungi, yeast, and bacteria. The metal ions are reduced by natural biomolecules such as flavonoids, tannins, saponins, terpenoids, steroids, and alkaloids [ 13 – 15 ]. Manganese oxide nanoparticles are particularly attractive due to their cost-effectiveness, environmental compatibility, and potential in various applications including photo catalysis, biomedicine, sensing, and optoelectronics, owing to their surface reactivity and physicochemical characteristics. Despite significant studies focusing on the electronic properties of MnO₂-NPs, their photocatalytic performance especially under sunlight has been less explored. This work investigates the green synthesis of MnO₂-NPs using Lagerstroemia speciosa leaf extract, with particular emphasis on their ability to decolorize methyl orange and bromocresol green dyes under solar irradiation. 2. Materials and Methods 2.1 Preparation of Plant Extract Fresh, mature leaves of Lagerstroemia speciosa were collected, thoroughly washed with distilled water to remove dirt and impurities, and then air-dried. Five grams of the dried leaves were finely ground into powder and extracted with 100 mL of Milli-Q water by boiling the mixture in a water bath for 30 minutes. The extract was filtered through Whatman No. 1 filter paper to remove solid residues. The resulting aqueous extract was stored at 6°C until further use. 2.2 Synthesis of Manganese Oxide Nanoparticles (MnO₂-NPs) Manganese acetate (Mn(CH₃COO)₂) was used as the precursor salt for nanoparticle synthesis. A 0.1 M solution was prepared by dissolving 1.73 g of manganese acetate in 100 mL of distilled water. The synthesis was carried out by adding 100 mL of Lagerstroemia speciosa leaf extract dropwise to the 100 mL of 0.1 M manganese acetate solution preheated to 60°C under continuous stirring. The mixture was then heated at 80°C for 30 minutes. The gradual colour change from colourless to dark brown or black indicated the formation of MnO₂ nanoparticles. After cooling to room temperature, the solution was centrifuged at 15,000 rpm for 15 minutes. The supernatant was discarded, and the collected nanoparticles were dried in an oven at 60°C for further characterization. 3. Materials Characterization 3.1 Structural Properties: X-ray Diffraction (XRD) Analysis The structural properties of manganese oxide nanoparticles (MnO₂-NPs) were analysed using X-ray diffraction (XRD) on a Bruker D8 Advanced model (Germany) equipped with Cu Kα₁ radiation (λ = 1.54056 Å). Data were collected over a 2θ range of 20°–80° with a scanning speed of 0.5°/min. The detector used was a fast-counting silicon strip (Bruker Lynx Eye). XRD measurements were performed both before and after calcination. The uncalcined manganese oxide sample showed no discernible diffraction peaks. After calcination at 600°C for 2 hours, distinct peaks appeared at 2θ values of 28.74°, 37.46°, 41.28°, 42.30°, 47.35°, 57.60°, and 59.50°, corresponding to the (110), (101), (200), (111), (210), (211), and (220) lattice planes, respectively. The diffraction pattern confirmed a polycrystalline nature of the sample. The XRD pattern was indexed to the tetragonal phase of manganese oxide, consistent with JCPDS card No. 24–0735, with lattice parameters a = b = 9.81 Å and c = 2.84 Å [ 17 ]. No additional peaks from impurities were observed, indicating high purity and crystallinity of the synthesized nanoparticles. The average crystallite size was estimated using the Scherrer formula applied to the main diffraction peaks, yielding a size of approximately 25.3 nm [ 16 ]. 3.2 Field Emission Scanning Electron Microscopy (FESEM) Field emission scanning electron microscopy (FESEM) was employed to investigate the surface morphology and microstructure of the manganese oxide nanoparticles. FESEM images were obtained using a Hitachi S-4800 instrument (Hitachi High Technologies Corporation, Japan). Figure 3 (a–c) presents FESEM images of manganese oxide nanoparticles calcined at 600°C, captured at different magnifications (100×, 20,000×, and 50,000×). The images reveal that the nanoparticles exhibit polymorphic morphology, with predominantly irregular, spherical, and randomly oriented particles formed via the Lagerstroemia speciosa leaf extract-mediated synthesis. Particle aggregation is evident, which can be attributed to high surface energy, electrostatic interactions, and polarity effects [ 18 ]. Such aggregation may enhance adsorption properties, beneficial for dye removal applications, due to the increased surface area and reduced particle size [ 19 ]. Furthermore, the reduction in particle size can be credited to the capping effect of active organic compounds in the plant extract, which inhibit excessive particle growth [ 20 ]. The nanoparticles show a size distribution ranging from approximately 83 nm to 400 nm. The presence of voids among the particles suggests potential sites for doping or further functionalization to enhance structural and functional properties. 3.3 Fourier Transform Infrared Spectroscopy (FTIR) Fourier transform infrared spectroscopy (FTIR) was used to identify the functional groups present in the manganese oxide nanoparticles and to understand the modes of vibration of chemical bonds within the nanocomposites. The FTIR spectrum of the MnO₂ nanoparticles was recorded in the range of 4000 − 400 cm⁻¹, as shown in Fig. 4 . A prominent absorption peak at 579 cm⁻¹ corresponds to the Mn–O bond, indicating the Mn–O stretching vibration characteristic of the O–Mn–O framework in MnO₂ [ 21 – 23 ]. The absorption band at 1032 cm⁻¹ is attributed to O–H bending vibrations coupled with Mn atoms, while the peak at 1416 cm⁻¹ corresponds to the C–N stretching of amine groups. The peak observed near 1557 cm⁻¹ is assigned to nitrate groups [ 24 ]. Additional absorption bands at 2324 cm⁻¹, 2829 cm⁻¹, 2943 cm⁻¹, and 3745 cm⁻¹ correspond to the stretching vibrations of C–OH, C ≡ C, C–H, and –OH groups, respectively [ 25 – 27 ]. These functional groups likely originate from various phytochemicals in the Lagerstroemia speciosa leaf extract, such as flavonoids and alkaloids, which act as both reducing and capping agents during nanoparticle synthesis [ 28 , 29 ]. 3.4 Thermogravimetric Analysis (TGA/DTA) Thermogravimetric analysis (TGA) and differential thermal analysis (DTA) were conducted to evaluate the thermal stability and decomposition behaviour of the synthesized manganese oxide nanoparticles. The TGA/DTA curves are presented in Fig. 5 (a, b). The heating process was initiated at room temperature and increased to 850°C at a rate of 10°C/min under a nitrogen atmosphere. The initial weight loss observed between 20°C and 100°C corresponds to the removal of physically adsorbed water and water of crystallization, indicating dehydration of the manganese oxide surface. A second minor mass loss was observed between 100°C and 260°C, which can be attributed to the release of unreacted organic molecules originating from the Lagerstroemia speciosa leaf extract used during the biosynthesis process. A significant mass loss occurred between 300°C and 320°C, accounting for a total weight reduction of approximately 65–69%. This is likely due to the decomposition of organic compounds and partial crystallization processes. The sustained thermal stability observed beyond 550°C suggests the formation of stable manganese oxide phases, particularly α-MnO₂, characterized by enhanced ionic bonding and lattice ordering. No appreciable weight loss was detected in the temperature range of 550–850°C, indicating that the MnO₂ nanoparticles exhibit high thermal stability and are resistant to further decomposition [ 30 , 31 ]. The DTA curve shows a prominent endothermic peak around 455°C, which is attributed to the melting behavior associated with the nanocrystalline nature of the material. A broader peak at approximately 600°C is ascribed to a phase transition from α-MnO₂ to another polymorphic form of MnO₂. $$\:Mn{\left({CH}_{3}COO\right)}_{2}\:2{H}_{2}O\:⟶\:{Mn}_{3}{O}_{4}+4\:{CO}_{2}+{C}_{8}{H}_{18}+\:6{H}_{2}O\uparrow\:\:$$ $$\:{Mn}_{3}{O}_{4}+4\:{CO}_{2}+{C}_{8}{H}_{18}\:⟶{Mn}_{3}{O}_{4}\:+\:{C}_{8}{H}_{18}+4\:{CO}_{2}+\uparrow\:$$ $$\:{Mn}_{3}{O}_{4}\:+\:{C}_{8}{H}_{18}\:⟶\:{C}_{8}{H}_{18}\uparrow\:$$ $$\:{Mn}_{3}{O}_{4}\:⟶\:3\:MnO\:+{1/2\:\:O}_{2}\uparrow\:$$ 3.5 Optical Properties: UV - Visible Spectroscopy UV-Visible spectroscopy was employed to investigate the optical properties of the biosynthesized manganese oxide (MnO₂) nanostructures. The absorbance behaviour is influenced by several factors, including impurity centers, surface roughness, oxygen vacancies, and band gap energy. Figure 6 illustrates the UV-Vis absorption spectrum of MnO₂ nanoparticles recorded at room temperature. A distinct absorption peak is observed at 365 nm, which corresponds to the electronic transition characteristic of MnO₂ nanostructures. This absorption is indicative of the formation of well-defined nanoscale manganese oxide particles. The optical band gap of the synthesized MnO₂ nanoparticles was estimated using the Tauc plot method and found to be approximately 3.39 eV. This wide band gap suggests that the nanomaterial is semiconducting in nature and possesses strong potential as an efficient photo catalyst in environmental remediation and other photocatalytic applications. 4. Photocatalytic Activity of MnO₂ Nanoparticles The photocatalytic performance of the synthesized MnO₂ nanoparticles was evaluated through the degradation of two organic dyes methyl orange (MO) and bromocresol green (BCG) under natural sunlight irradiation. In each experiment, approximately 10 mg of MnO₂ NPs was added to a solution containing 10 mL of dye (25 mg/L concentration) and 1 mL of NaBH₄ solution (3 × 10⁻ 2 mol/L). The reaction mixtures were placed in screw-cap vials, thoroughly mixed, and then exposed to direct solar radiation. UV–Visible spectra were recorded at regular intervals over a period of 60 minutes to monitor the extent of decolourization. The catalytic efficiency of MnO₂ NPs in degrading MO and BCG is illustrated in Fig. 8 . A noticeable decrease in the absorption intensity of the dyes was observed, indicating significant photocatalytic degradation. The efficiency of degradation was calculated using the equation: $$\:colour\:removal\left(\text{%}\right)=\:\left({C}_{0}-\:\raisebox{1ex}{${C}_{t}$}\!\left/\:\!\raisebox{-1ex}{${C}_{0}$}\right.\right)x\:100$$ where C 0 ​ (mg/L) and C t (mg/L) represent the dye concentrations at time zero and time t , respectively. After 60 minutes of irradiation, the MnO₂ NPs demonstrated a high photocatalytic activity, achieving approximately 90% decolourization of methyl orange and 93% of bromocresol green at neutral pH. These results confirm the efficiency of the biosynthesized MnO₂ nanoparticles as effective photo catalysts. The photocatalytic degradation mechanism involves the excitation of electrons from the valence band (VB) to the conduction band (CB) upon absorption of photons with energy equal to or greater than the band gap energy (E g ). This excitation results in the formation of electron-hole pairs. These charge carriers migrate to the nanoparticle surface, where they interact with molecular oxygen (O₂) and water (H₂O) to generate reactive oxygen species (ROS), including hydroxyl (•OH) and superoxide (O₂⁻•) radicals, which contribute to the degradation of dye molecules. Kinetic analysis of the photocatalytic degradation was carried out by plotting ln(A₀/At) versus time (Figs. 8 and 10 ). The linear relationship indicates that the degradation follows a pseudo-first-order reaction model. The rate constants ( k ) for MO and BCG degradation were calculated to be 0.020 min⁻¹ and 0.026 min⁻¹, respectively. Additionally, the degradation of dyes with NaBH₄ in the absence of MnO₂-NPs was also examined. Although NaBH₄ is a known reducing agent and thermodynamically favourable for breaking azo bonds in MO and BCG to form amino derivatives, the reaction proceeded very slowly due to kinetic limitations. In contrast, the presence of MnO₂ NPs provided an alternative reaction pathway with a lower activation energy, thereby enhancing both the thermodynamic and kinetic feasibility of dye degradation. These findings suggest that biosynthesized MnO₂ nanoparticles possess excellent photocatalytic capabilities and are promising candidates for environmental applications such as wastewater treatment. 4.1 Methyl Orange (MO): 4.2 Bromocresol green (BCG) 5. Conclusions In this study, manganese dioxide (MnO₂) nanoparticles were successfully synthesized via a green synthesis route using Lagerstroemia speciosa leaf extract as a natural reducing and stabilizing agent. The X-ray diffraction (XRD) analysis confirmed that the synthesized nanoparticles exhibit a polycrystalline tetragonal phase with an average crystallite size of 25.3 nm, as calculated using Scherrer’s equation. Field Emission Scanning Electron Microscopy (FESEM) revealed that the MnO₂ nanoparticles possess irregular, aggregated, and roughly spherical morphologies, with particle sizes ranging from 83 nm to 400 nm. The observed aggregation is attributed to the high surface energy and polarity of the nanoparticles, along with electrostatic interactions. These morphological features contribute to an increased surface area, which enhances the adsorption efficiency of the nanoparticles for dye degradation. The UV visible spectroscopy results showed a strong absorption peak at 365 nm, corresponding to the MnO₂ nanostructures, with a calculated optical band gap of 3.39 eV, indicating their potential for visible-light-driven photo catalysis. Photocatalytic degradation experiments demonstrated that the MnO₂ nanoparticles efficiently degraded both methyl orange and bromocresol green dyes within 60 minutes, achieving near-complete decolourization. The reduction in absorbance at 460 nm further confirms the complete degradation of the dye molecules. Overall, the biosynthesized MnO₂ nanoparticles exhibit promising structural, optical, and photocatalytic properties, highlighting their potential for application in environmental remediation, particularly in the treatment of dye-contaminated wastewater. Declarations Competing Interest The authors declare no competing interest. Funding Statement: The authors declare that no funds, grants, or other support were received during the preparation of this manuscript. Author Contribution Jagdish Arekar: Conceptualization, methodology, investigation, data curation, writing original draft preparation.Dipak Garole: Formal analysis, supervision, writing review and editing.R. S. Bendre: Resources, validation, project administration, supervision, funding acquisition.Yogesh R. Toda: Visualization, writing original draft preparation, software support, data curation, writing review and editing.All authors have read and approved the final version of the manuscript. Acknowledgement The authors gratefully acknowledge the lab personnel of thin film laboratory, Pratap College, Amalner, School of Chemical Sciences, K.B.C. North Maharashtra University, Jalgaon and Directorate of Geology and Mining, Government of Maharashtra, Nagpur for their generous support during the research work. References Dr. G. Sakthi, and Dr. P. Saravanakumari, Green Synthesis of Manganese Oxide Nanoparticles using Phyllanthusacidus , International J. of Multidisciplinary Educational Research, Vol. 10 Issue 4 (7) (April 2021) 112–116. Siddique M, Fayaz N, Saeed M, Synthesis, characterization, photocatalytic activity and gas sensing properties of zinc doped manganese oxide nanoparticles. Phys. Rev. B. Condens. Matter 602 (2021) 412504. https://doi.org/10.1016/j. physb. 2020.412504. M. Jayandran, M. MuhamedHaneefa, V. Balasubramanian, Green synthesis and characterization of Manganese nanoparticles using natural plant extracts and its evaluation of antimicrobial activity, Journal of Applied Pharmaceutical Science Vol. 5 (12) (December, 2015) 105–110, DOI: 10.7324/JAPS.2015.501218 . Chen HJ, Tian W, Ding W. Effect of preparation methods of the morphology of active manganese dioxide and 2, 4Dinitrophenol adsorption performance; Adsorption Science And Technology 36 (3–4) (2018) 1100–1111. DOI: 10.4172/2169-0022.1000172 . Sagadevan S. Investigations synthesis, structural, morphological and dielectric properties of manganese oxides nanoparticles; Journal of Material Sciences & Engineering. 4(3) (2015) 1–3. Feng L, Xuan Z, Zhao H, Bai Y, Guo J, Su CW, MnO prepared by hydrothermal method and electrochemical performance as anode for lithium-ion battery. Nanoscale Research Letters, 9 (290) (2014) 1–8. S. Mitra, Y. Pak, N. Alaal, M.N. Hedhili, D.R. Almalawi, N. Alwadai, K. Loganathan, Y. Kumarasan, N. Lim, G.Y. Jung, I.S. Roqan, Novel P-Type Wide Band Gap Manganese Oxide Quantum Dots Operating at Deep UV Range for Optoelectronic Devices, Adv. Opt. Mater. 7 (21) (2019) 1900801 M. M. Najafpour, S. I. Allakhverdiev, Manganese compounds as water oxidizing catalysts for hydrogen production via water splitting: From manganese complexes to nano-sized manganese oxides, Int. J. Hydrogen Energy 37 (2012) 8753–8764, https://doi.org/10.1016/J.IJHYDENE.2012.02.075 . H.T. Zhang, X.H. Chen, J.H. Zhang, G.Y. Wang, S.Y. Zhang, Y.Z. Long, Z.J. Chen, N. L. Wang, Synthesis and characterization of one-dimensional K 0.27 MnO 2 -0.5H 2 O, J. Cryst. Growth 280 (1–2) (2005) 292–299. Q. Shu-yan, F. Jing, Y. Jun, Hydrothermal synthesis and super capacitor properties of urchin sphere and nanowire MnO 2 , Chinese J. Nonferrous Met. 18 (2008) 113–117. Haibin Lu, Xueyang Zhang, Ahmad Khan, Wenqiang Li, Lei Wan, Biogenic Synthesis of MnO2 Nanoparticles with Leaf Extract of Voila betonicifolia for Enhanced Antioxidant, Antimicrobial, Cytotoxic and Biocompatible Applications, Frontiers in Microbiology, 12 (Nov. 2021) 761084; doi: 10.3389/fmicb.2021.761084 K. S. Shaker, A. H. Abdalsalm, Characterization Nano Structure of MnO 2 via Chemical Method, Eng Technol. J. 36 (2018) 946–950.10.30684/etj.36.9A.1 Sanjay S. Majani, SreelakshmiSathyan, MeghaVadakkethil, Manoj, Nimisha Vinod, Sushma Pradeep, Chandan Shivamallu, Venkatachalaiah K. N, Shiva Prasad Kollur, Eco-friendly synthesis of MnO nanoparticles using Saracaasoca leaf extract and evaluation of in vitro anticancer activity, Current Research in Green Sustainable Chemistry, 6 (2023) http://doi.org/10.1016/j.crgsc.2023.100367 A.Cauerhff, G. R. Castro, Bio-nanoparticles, a green nano - chemistry approach, Electronic Journal of Biotechnology, Review 16 (3) (2013) 1–10. Available: www.ejbiotechnology.info DOI: 10.2225. A. G. Ingale, A. N. Chaudhari, Biogenic synthesis of nanoparticles and potential applications: an eco-friendly approach, Journal of Nanomedicene and Nanotechnology, 2 (2013) 1–7. DOI: 10. 4172/2157-7439.1000165. Ibrahim Mohamed Abouzeid Hasan, Hassan M. A. Salman, Olfat M. Hafez, Ficus-mediated green synthesis of manganese oxide nanoparticles for adsorptive removal of malachite green from surface water, Environmental Science and Pollution Research, 30 (2023) 28144–28161, https://doi.org/10.1007/s11356-022-24199-8 AKM Atique Ullah, Md. Mahbubul Haque, MahmudaAkter, AHossain, Md. Mottaleb Hosen, AKM Fazle Kibria, MNI Khan and MKA Khan, Green synthesis of Bryophyllumpinnatum aqueous leaf extract mediated bio-molecule capped dilute ferromagnetic α-MnO 2 nanoparticles, Mater. Res. Express 7 (2020) 015088, DOI: 10.1088/2053-1591/ab6c20 . Madhumitha G, Fowsiya J, Gupta N, Kumar A, Singh M, Green synthesis, characterization and antifungal and photocatalytic activity of Pithecellobium dulce peel mediated ZnO nanoparticles, J Phys. Chem. Solids 127 (2019) 43–51, https://doi.org/10.1016/j.jpcs.2018.12.005 Ibrahim Mohamed Abouzeid Hasan, Hassan M. A. Salman, Olfat M. Hafez, Ficus-mediated green synthesis of manganese oxide nanoparticles for adsorptive removal of malachite green from surface water, Environmental Science and Pollution Research 30 (2023) 28144–2816, https://doi.org/10.1007/s11356-022-24199-8 Y. Dessie, S. Tadesse, R. Eswaramoorthy, Physicochemical parameter influences and their optimization on the biosynthesis of MnO 2 nanoparticles using Vernonia amygdalina leaf extract, Arab J Chem. 13 (2020) 6472–6492. https://doi.org/10. 1016/j. arabjc.2020. 06. 006. S. Karnchanawong and P. Limpiteeprakan, Evaluation of Heavy Metal Leaching from Spent Household Batteries Disposed in Municipal Solid Waste, Waste Management, Vol. 29, No. 2 (2009) 550–558. doi: 10.1016/j.wasman.2008.03.018 . Susana M Xará, Julanda N Delgado, Manuel Almeida, Carlos A. V. Costa, Laboratory study on the leaching potential of spent alkaline batteries, Waste Management 29(7) (April- 2009) 2121–31, DOI: 10.1016/j.wasman.2009.03.010 . M Mylarappa, V Venkata Lakshmi, K R Vishnu Mahesh, H P Nagaswarupa, N Raghavendra; A facile hydrothermal recovery of nano sealed MnO 2 particle from waste batteries: An advanced material for electrochemical and environmental applications, IOP Conf. Series: Materials Science and Engineering 149 (2016) 012178, doi: 10.1088/1757-899X/149/1/012178 . Jannatun Zia, Elham Aazam, Ufana Riaz, Synthesis of nanohybrids of polycarbazole with α-MnO2 derived from Brassica oleracea: a comparison of photocatalytic degradation of an antibiotic drug under microwave and UV irradiation, Environmental Science and Pollution Research 27(19) (July 2020) 24173–24189, https://doi.org/10.1007/s11356-020-08149.w . Vahid Hoseinpour, MahsaSouri, Nasser Ghaemi, Green synthesis, characterisation, and photocatalytic activity of manganese dioxide nanoparticles, Micro & Nano Letters, 13, Iss. 11 (2018) 1560–1563; doi: 10.1049/mnl.2018.5008 Kollur Shiva Prasad and Alakananda Patra, Green synthesis of MnO 2 nanorods using Phyllanthus amarus plant extract and their fluorescence studies, Green Processing and Synthesis, 6 (2017) 549–554; https://doi.org/10.1515/gps-2016-0166 Mamun M A A, Noor M, Ullah A K M A, Hossain M S, Matin M A, Islam F and Hakim M A, Effect of CePO 4 on structural, magnetic and optical properties of ceria nanoparticles, Mater. Res. Express 6 (1) (2018) 016102, DOI 10.1088/2053 – 1591/aae2d0 . A. Bystrom and A. M. Bystrom, The crystal structure of hollandite, the related manganese oxide minerals, and α-MnO2, Acta Cryst. 3 (1950) 146–54, https://doi.org/10.1107/S0365110X5000032X . Mariya Moeen, Shazia Nouren, Maria Zaib, Ismat Bibi, Abida Kausar&Misbah Sultan, Green synthesis, characterization and sorption efficiency of MnO 2 nanoparticles and MnO 2 @waste eggshell nanocomposite, Journal of Taibah University for Science, 16 No. 1 (2022) 1075–1095; https://doi.org/10.1080/16583655.2022.2139483 A. Martin Joseph and R. Thilak Kumar, Formation and investigation of low dimensional super paramagnetic α-manganese dioxide nanostructures, Materials Research Express, Vol. 5 No. 1(Jan. 2018); DOI: http://dx.doi.org/10.1088/2053-1591/aa9e5d YuXin Zhang, Shijin Zhu, Meng Dong, Chuan Pu Liu, Zhong Quan Wen, Hydrothermally Tailoring Low-dimensional MnO x Nanostructure and Their High Electrochemical Performance, International Journal of Electrochemical Science, Vol. 8, Issue 2 (Feb 2013) 2407–2416; https://doi.org/10.1016/S1452-3981(23)14318-5 Additional Declarations No competing interests reported. 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Garole","email":"","orcid":"","institution":"Government of Maharashtra","correspondingAuthor":false,"prefix":"","firstName":"Dipak.","middleName":"J.","lastName":"Garole","suffix":""},{"id":463382575,"identity":"822cbfad-e198-4afa-ade5-de00ec48ecc3","order_by":2,"name":"Yogesh R. Toda","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA4klEQVRIiWNgGAWjYLACxgYgcYD5AJCUkCFWiwFQC1sCSAsPKVp4DEBswloMjrdffPhzxx85vuNnPr+6UWPBw8B++OgGvFrOnCk25j1jYCx5Jnebdc4xoMN40tJu4NVyIydNmrHNIHHDgdxtxjlsQC0SPGaEtKT//AnScv7NM+Ocf0RpST/GwAvSciOH+XFuGxFaJM+cYZbmbTM2lrzxzIw5t0+Ch42QX/iOtz/8+LNNTo7vfPLjzznf6uT42Q8fw6tFARodIMAmASbxKQcB+Qb2BzA28wdCqkfBKBgFo2BkAgB1FU9JkkFHPgAAAABJRU5ErkJggg==","orcid":"","institution":"Government College of Engineering","correspondingAuthor":true,"prefix":"","firstName":"Yogesh","middleName":"R.","lastName":"Toda","suffix":""},{"id":463382576,"identity":"0cee1c1f-913e-4f0a-a22e-9befde4c72e5","order_by":3,"name":"Ratnamala S. Bendre","email":"","orcid":"","institution":"North Maharashtra University","correspondingAuthor":false,"prefix":"","firstName":"Ratnamala","middleName":"S.","lastName":"Bendre","suffix":""}],"badges":[],"createdAt":"2025-05-21 11:08:32","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6715891/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6715891/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":83797858,"identity":"b8eb608c-0d8d-43e0-9f79-75167d7f8dfc","added_by":"auto","created_at":"2025-06-03 01:26:54","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":377926,"visible":true,"origin":"","legend":"\u003cp\u003eFormation of manganese oxide nanoparticles (MnO₂-NPs) during the synthesis process.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-6715891/v1/9ed48d8b8c7cf40d99ee4733.png"},{"id":83797465,"identity":"5689c4c5-b79f-47f6-9fa0-8583df3cd60e","added_by":"auto","created_at":"2025-06-03 01:18:54","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":65074,"visible":true,"origin":"","legend":"\u003cp\u003eXRD- Diffractograms of Manganese Oxide Nanoparticles\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-6715891/v1/b9fe4df84fd16a6a8dfd4bf4.png"},{"id":83798295,"identity":"a67a75bb-c9aa-4d1b-9e8f-d78354737967","added_by":"auto","created_at":"2025-06-03 01:42:54","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":137730,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003e(a to c):\u003c/strong\u003eFE-SEM Images of Manganese Nanoparticles.\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-6715891/v1/066c20aec067b40f98926b38.png"},{"id":83797469,"identity":"6d341636-d04c-4394-b38c-d79d926e7187","added_by":"auto","created_at":"2025-06-03 01:18:54","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":71802,"visible":true,"origin":"","legend":"\u003cp\u003eFTIR spectrum of Manganese oxide Nanoparticles\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-6715891/v1/cfa0822e177b4fe0839af6dd.png"},{"id":83797462,"identity":"66da2812-454c-40ef-8112-345180e721b9","added_by":"auto","created_at":"2025-06-03 01:18:54","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":28115,"visible":true,"origin":"","legend":"\u003cp\u003e(a to b): TGA/DTA curves of the Manganese Oxide Nanoparticles\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-6715891/v1/952cbf86581783f75fc12893.png"},{"id":83798294,"identity":"8889987d-f5a3-437b-a2bd-69f50b341ae9","added_by":"auto","created_at":"2025-06-03 01:42:54","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":57152,"visible":true,"origin":"","legend":"\u003cp\u003eUV-Vis spectra of plant extract, Mn solution, and biosynthesized Mn nanoparticles\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-6715891/v1/6f3a7a51fccbccc8b2a59d2f.png"},{"id":83797869,"identity":"315a3ae2-ece3-4363-9320-24bfad54083b","added_by":"auto","created_at":"2025-06-03 01:26:55","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":62819,"visible":true,"origin":"","legend":"\u003cp\u003eUV-Visible Absorbance Spectrum of Methyl Orange \u0026amp; MnO\u003csub\u003e2\u003c/sub\u003e NPs Reaction Mixture\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-6715891/v1/14362ada9f2c96720e905f2d.png"},{"id":83797888,"identity":"f5eb6385-8496-4b7d-b533-445324a9854e","added_by":"auto","created_at":"2025-06-03 01:34:54","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":19569,"visible":true,"origin":"","legend":"\u003cp\u003eCalibration Curve [Ln (At/Ao) vs. time\u003c/p\u003e","description":"","filename":"8.png","url":"https://assets-eu.researchsquare.com/files/rs-6715891/v1/8b57394c6b13a3730e7d59c5.png"},{"id":83797886,"identity":"9cbb8be0-7364-4260-951b-69871b52257a","added_by":"auto","created_at":"2025-06-03 01:34:54","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":68628,"visible":true,"origin":"","legend":"\u003cp\u003eUV-Visible Absorbance Spectrum of Bromocresol Green \u0026amp; MnO\u003csub\u003e2\u003c/sub\u003e NPs Reaction Mixture\u003c/p\u003e","description":"","filename":"9.png","url":"https://assets-eu.researchsquare.com/files/rs-6715891/v1/b37e3f0175e57ff2df8aa22b.png"},{"id":83797868,"identity":"00a2939e-ff33-48b4-aee7-61a0595f13ca","added_by":"auto","created_at":"2025-06-03 01:26:55","extension":"png","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":29193,"visible":true,"origin":"","legend":"\u003cp\u003eCalibration Curve [Ln (At/Ao) vs. time\u003c/p\u003e","description":"","filename":"10.png","url":"https://assets-eu.researchsquare.com/files/rs-6715891/v1/2194c7a0ffbf8bec1027a425.png"},{"id":85058036,"identity":"f7a5a2a5-cffc-4ad8-a531-6dcacb696021","added_by":"auto","created_at":"2025-06-20 13:16:54","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1723090,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6715891/v1/81fcdf88-c3b2-4262-a61e-61be5e641d42.pdf"},{"id":83797460,"identity":"fdd343d6-fb1a-4664-8d92-4d8ae7045da1","added_by":"auto","created_at":"2025-06-03 01:18:54","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":42903,"visible":true,"origin":"","legend":"","description":"","filename":"TEATGA.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6715891/v1/fc1e705f60db8622efc4da15.pdf"},{"id":83797867,"identity":"8a3333d6-f184-48d4-a761-9dea07c29bfa","added_by":"auto","created_at":"2025-06-03 01:26:54","extension":"png","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":195095,"visible":true,"origin":"","legend":"\u003cp\u003eGA\u003c/p\u003e","description":"","filename":"GA.png","url":"https://assets-eu.researchsquare.com/files/rs-6715891/v1/d29a818c7dc1628b56df0878.png"}],"financialInterests":"No competing interests reported.","formattedTitle":"Tetragonal MnO₂ Nanoparticles Synthesized via Lagerstroemia speciosa: Structural Characterization and Photocatalytic Potential","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eIn nanotechnology, particle size plays a crucial role in determining the material\u0026rsquo;s properties. Nanoparticles exhibit unique structural, magnetic, and optical behaviours, governed by their size, shape, morphology, and composition [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. Morphology and dimension are particularly important, as they contribute to the stability and functionality of nanoparticles [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. Due to their high specific surface area and distinct electronic, chemical, and physical properties, metal nanoparticles especially manganese oxide nanoparticles\u0026mdash;have broad applications in batteries, catalysts, water treatment, molecular sieves, optoelectronics, and magnetic materials [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eManganese oxide nanoparticles (MnO₂-NPs) are also being explored for solar cell applications due to their promising electronic and optical properties [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. These nanoparticles can be synthesized via several techniques, including femtosecond laser ablation [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e], reflux treatment [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e], redox reaction [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e], green synthesis [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e], co-precipitation [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e], and sol\u0026ndash;gel methods [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eAmong these, green synthesis has gained attention as a sustainable, eco-friendly approach. This method utilizes plant parts leaves, stems, roots, bark, seeds or microbial agents like fungi, yeast, and bacteria. The metal ions are reduced by natural biomolecules such as flavonoids, tannins, saponins, terpenoids, steroids, and alkaloids [\u003cspan additionalcitationids=\"CR14\" citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. Manganese oxide nanoparticles are particularly attractive due to their cost-effectiveness, environmental compatibility, and potential in various applications including photo catalysis, biomedicine, sensing, and optoelectronics, owing to their surface reactivity and physicochemical characteristics.\u003c/p\u003e \u003cp\u003eDespite significant studies focusing on the electronic properties of MnO₂-NPs, their photocatalytic performance especially under sunlight has been less explored. This work investigates the green synthesis of MnO₂-NPs using \u003cem\u003eLagerstroemia speciosa\u003c/em\u003e leaf extract, with particular emphasis on their ability to decolorize methyl orange and bromocresol green dyes under solar irradiation.\u003c/p\u003e"},{"header":"2. Materials and Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1 Preparation of Plant Extract\u003c/h2\u003e \u003cp\u003eFresh, mature leaves of \u003cem\u003eLagerstroemia speciosa\u003c/em\u003e were collected, thoroughly washed with distilled water to remove dirt and impurities, and then air-dried. Five grams of the dried leaves were finely ground into powder and extracted with 100 mL of Milli-Q water by boiling the mixture in a water bath for 30 minutes. The extract was filtered through Whatman No. 1 filter paper to remove solid residues. The resulting aqueous extract was stored at 6\u0026deg;C until further use.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2 Synthesis of Manganese Oxide Nanoparticles (MnO₂-NPs)\u003c/h2\u003e \u003cp\u003eManganese acetate (Mn(CH₃COO)₂) was used as the precursor salt for nanoparticle synthesis. A 0.1 M solution was prepared by dissolving 1.73 g of manganese acetate in 100 mL of distilled water. The synthesis was carried out by adding 100 mL of \u003cem\u003eLagerstroemia speciosa\u003c/em\u003e leaf extract dropwise to the 100 mL of 0.1 M manganese acetate solution preheated to 60\u0026deg;C under continuous stirring. The mixture was then heated at 80\u0026deg;C for 30 minutes. The gradual colour change from colourless to dark brown or black indicated the formation of MnO₂ nanoparticles. After cooling to room temperature, the solution was centrifuged at 15,000 rpm for 15 minutes. The supernatant was discarded, and the collected nanoparticles were dried in an oven at 60\u0026deg;C for further characterization.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"3. Materials Characterization","content":"\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e3.1 Structural Properties: X-ray Diffraction (XRD) Analysis\u003c/h2\u003e \u003cp\u003eThe structural properties of manganese oxide nanoparticles (MnO₂-NPs) were analysed using X-ray diffraction (XRD) on a Bruker D8 Advanced model (Germany) equipped with Cu Kα₁ radiation (λ\u0026thinsp;=\u0026thinsp;1.54056 \u0026Aring;). Data were collected over a 2θ range of 20\u0026deg;\u0026ndash;80\u0026deg; with a scanning speed of 0.5\u0026deg;/min. The detector used was a fast-counting silicon strip (Bruker Lynx Eye). XRD measurements were performed both before and after calcination. The uncalcined manganese oxide sample showed no discernible diffraction peaks. After calcination at 600\u0026deg;C for 2 hours, distinct peaks appeared at 2θ values of 28.74\u0026deg;, 37.46\u0026deg;, 41.28\u0026deg;, 42.30\u0026deg;, 47.35\u0026deg;, 57.60\u0026deg;, and 59.50\u0026deg;, corresponding to the (110), (101), (200), (111), (210), (211), and (220) lattice planes, respectively. The diffraction pattern confirmed a polycrystalline nature of the sample.\u003c/p\u003e \u003cp\u003eThe XRD pattern was indexed to the tetragonal phase of manganese oxide, consistent with JCPDS card No. 24\u0026ndash;0735, with lattice parameters a\u0026thinsp;=\u0026thinsp;b\u0026thinsp;=\u0026thinsp;9.81 \u0026Aring; and c\u0026thinsp;=\u0026thinsp;2.84 \u0026Aring; [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. No additional peaks from impurities were observed, indicating high purity and crystallinity of the synthesized nanoparticles.\u003c/p\u003e \u003cp\u003eThe average crystallite size was estimated using the Scherrer formula applied to the main diffraction peaks, yielding a size of approximately 25.3 nm [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e].\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003e3.2 Field Emission Scanning Electron Microscopy (FESEM)\u003c/h2\u003e \u003cp\u003eField emission scanning electron microscopy (FESEM) was employed to investigate the surface morphology and microstructure of the manganese oxide nanoparticles. FESEM images were obtained using a Hitachi S-4800 instrument (Hitachi High Technologies Corporation, Japan).\u003c/p\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e (a\u0026ndash;c) presents FESEM images of manganese oxide nanoparticles calcined at 600\u0026deg;C, captured at different magnifications (100\u0026times;, 20,000\u0026times;, and 50,000\u0026times;). The images reveal that the nanoparticles exhibit polymorphic morphology, with predominantly irregular, spherical, and randomly oriented particles formed via the \u003cem\u003eLagerstroemia speciosa\u003c/em\u003e leaf extract-mediated synthesis.\u003c/p\u003e \u003cp\u003eParticle aggregation is evident, which can be attributed to high surface energy, electrostatic interactions, and polarity effects [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. Such aggregation may enhance adsorption properties, beneficial for dye removal applications, due to the increased surface area and reduced particle size [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. Furthermore, the reduction in particle size can be credited to the capping effect of active organic compounds in the plant extract, which inhibit excessive particle growth [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. The nanoparticles show a size distribution ranging from approximately 83 nm to 400 nm. The presence of voids among the particles suggests potential sites for doping or further functionalization to enhance structural and functional properties.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003e3.3 Fourier Transform Infrared Spectroscopy (FTIR)\u003c/h2\u003e \u003cp\u003eFourier transform infrared spectroscopy (FTIR) was used to identify the functional groups present in the manganese oxide nanoparticles and to understand the modes of vibration of chemical bonds within the nanocomposites. The FTIR spectrum of the MnO₂ nanoparticles was recorded in the range of 4000\u0026thinsp;\u0026minus;\u0026thinsp;400 cm⁻\u0026sup1;, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e.\u003c/p\u003e \u003cp\u003eA prominent absorption peak at 579 cm⁻\u0026sup1; corresponds to the Mn\u0026ndash;O bond, indicating the Mn\u0026ndash;O stretching vibration characteristic of the O\u0026ndash;Mn\u0026ndash;O framework in MnO₂ [\u003cspan additionalcitationids=\"CR22\" citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]. The absorption band at 1032 cm⁻\u0026sup1; is attributed to O\u0026ndash;H bending vibrations coupled with Mn atoms, while the peak at 1416 cm⁻\u0026sup1; corresponds to the C\u0026ndash;N stretching of amine groups. The peak observed near 1557 cm⁻\u0026sup1; is assigned to nitrate groups [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eAdditional absorption bands at 2324 cm⁻\u0026sup1;, 2829 cm⁻\u0026sup1;, 2943 cm⁻\u0026sup1;, and 3745 cm⁻\u0026sup1; correspond to the stretching vibrations of C\u0026ndash;OH, C\u0026thinsp;\u0026equiv;\u0026thinsp;C, C\u0026ndash;H, and \u0026ndash;OH groups, respectively [\u003cspan additionalcitationids=\"CR26\" citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]. These functional groups likely originate from various phytochemicals in the \u003cem\u003eLagerstroemia speciosa\u003c/em\u003e leaf extract, such as flavonoids and alkaloids, which act as both reducing and capping agents during nanoparticle synthesis [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e, \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e].\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003e3.4 Thermogravimetric Analysis (TGA/DTA)\u003c/h2\u003e \u003cp\u003eThermogravimetric analysis (TGA) and differential thermal analysis (DTA) were conducted to evaluate the thermal stability and decomposition behaviour of the synthesized manganese oxide nanoparticles. The TGA/DTA curves are presented in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e (a, b). The heating process was initiated at room temperature and increased to 850\u0026deg;C at a rate of 10\u0026deg;C/min under a nitrogen atmosphere.\u003c/p\u003e \u003cp\u003eThe initial weight loss observed between 20\u0026deg;C and 100\u0026deg;C corresponds to the removal of physically adsorbed water and water of crystallization, indicating dehydration of the manganese oxide surface. A second minor mass loss was observed between 100\u0026deg;C and 260\u0026deg;C, which can be attributed to the release of unreacted organic molecules originating from the \u003cem\u003eLagerstroemia speciosa\u003c/em\u003e leaf extract used during the biosynthesis process.\u003c/p\u003e \u003cp\u003eA significant mass loss occurred between 300\u0026deg;C and 320\u0026deg;C, accounting for a total weight reduction of approximately 65\u0026ndash;69%. This is likely due to the decomposition of organic compounds and partial crystallization processes. The sustained thermal stability observed beyond 550\u0026deg;C suggests the formation of stable manganese oxide phases, particularly α-MnO₂, characterized by enhanced ionic bonding and lattice ordering.\u003c/p\u003e \u003cp\u003eNo appreciable weight loss was detected in the temperature range of 550\u0026ndash;850\u0026deg;C, indicating that the MnO₂ nanoparticles exhibit high thermal stability and are resistant to further decomposition [\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e, \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe DTA curve shows a prominent endothermic peak around 455\u0026deg;C, which is attributed to the melting behavior associated with the nanocrystalline nature of the material. A broader peak at approximately 600\u0026deg;C is ascribed to a phase transition from α-MnO₂ to another polymorphic form of MnO₂.\u003cdiv id=\"Equa\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equa\" name=\"EquationSource\"\u003e\n$$\\:Mn{\\left({CH}_{3}COO\\right)}_{2}\\:2{H}_{2}O\\:⟶\\:{Mn}_{3}{O}_{4}+4\\:{CO}_{2}+{C}_{8}{H}_{18}+\\:6{H}_{2}O\\uparrow\\:\\:$$\u003c/div\u003e\u003c/div\u003e\u003cdiv id=\"Equb\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equb\" name=\"EquationSource\"\u003e\n$$\\:{Mn}_{3}{O}_{4}+4\\:{CO}_{2}+{C}_{8}{H}_{18}\\:⟶{Mn}_{3}{O}_{4}\\:+\\:{C}_{8}{H}_{18}+4\\:{CO}_{2}+\\uparrow\\:$$\u003c/div\u003e\u003c/div\u003e\u003cdiv id=\"Equc\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equc\" name=\"EquationSource\"\u003e\n$$\\:{Mn}_{3}{O}_{4}\\:+\\:{C}_{8}{H}_{18}\\:⟶\\:{C}_{8}{H}_{18}\\uparrow\\:$$\u003c/div\u003e\u003c/div\u003e\u003cdiv id=\"Equd\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equd\" name=\"EquationSource\"\u003e\n$$\\:{Mn}_{3}{O}_{4}\\:⟶\\:3\\:MnO\\:+{1/2\\:\\:O}_{2}\\uparrow\\:$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003e3.5 Optical Properties: UV - Visible Spectroscopy\u003c/h2\u003e \u003cp\u003eUV-Visible spectroscopy was employed to investigate the optical properties of the biosynthesized manganese oxide (MnO₂) nanostructures. The absorbance behaviour is influenced by several factors, including impurity centers, surface roughness, oxygen vacancies, and band gap energy.\u003c/p\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e illustrates the UV-Vis absorption spectrum of MnO₂ nanoparticles recorded at room temperature. A distinct absorption peak is observed at 365 nm, which corresponds to the electronic transition characteristic of MnO₂ nanostructures. This absorption is indicative of the formation of well-defined nanoscale manganese oxide particles.\u003c/p\u003e \u003cp\u003eThe optical band gap of the synthesized MnO₂ nanoparticles was estimated using the Tauc plot method and found to be approximately 3.39 eV. This wide band gap suggests that the nanomaterial is semiconducting in nature and possesses strong potential as an efficient photo catalyst in environmental remediation and other photocatalytic applications.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"4. Photocatalytic Activity of MnO₂ Nanoparticles","content":"\u003cp\u003eThe photocatalytic performance of the synthesized MnO₂ nanoparticles was evaluated through the degradation of two organic dyes methyl orange (MO) and bromocresol green (BCG) under natural sunlight irradiation. In each experiment, approximately 10 mg of MnO₂ NPs was added to a solution containing 10 mL of dye (25 mg/L concentration) and 1 mL of NaBH₄ solution (3 \u0026times; 10⁻\u003csup\u003e2\u003c/sup\u003e mol/L). The reaction mixtures were placed in screw-cap vials, thoroughly mixed, and then exposed to direct solar radiation. UV\u0026ndash;Visible spectra were recorded at regular intervals over a period of 60 minutes to monitor the extent of decolourization.\u003c/p\u003e \u003cp\u003eThe catalytic efficiency of MnO₂ NPs in degrading MO and BCG is illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e. A noticeable decrease in the absorption intensity of the dyes was observed, indicating significant photocatalytic degradation. The efficiency of degradation was calculated using the equation:\u003cdiv id=\"Eque\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Eque\" name=\"EquationSource\"\u003e\n$$\\:colour\\:removal\\left(\\text{%}\\right)=\\:\\left({C}_{0}-\\:\\raisebox{1ex}{${C}_{t}$}\\!\\left/\\:\\!\\raisebox{-1ex}{${C}_{0}$}\\right.\\right)x\\:100$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003ewhere C\u003csub\u003e0\u003c/sub\u003e​ (mg/L) and C\u003csub\u003et\u003c/sub\u003e (mg/L) represent the dye concentrations at time zero and time \u003cem\u003et\u003c/em\u003e, respectively.\u003c/p\u003e \u003cp\u003eAfter 60 minutes of irradiation, the MnO₂ NPs demonstrated a high photocatalytic activity, achieving approximately 90% decolourization of methyl orange and 93% of bromocresol green at neutral pH. These results confirm the efficiency of the biosynthesized MnO₂ nanoparticles as effective photo catalysts.\u003c/p\u003e \u003cp\u003eThe photocatalytic degradation mechanism involves the excitation of electrons from the valence band (VB) to the conduction band (CB) upon absorption of photons with energy equal to or greater than the band gap energy (E\u003csub\u003eg\u003c/sub\u003e). This excitation results in the formation of electron-hole pairs. These charge carriers migrate to the nanoparticle surface, where they interact with molecular oxygen (O₂) and water (H₂O) to generate reactive oxygen species (ROS), including hydroxyl (\u0026bull;OH) and superoxide (O₂⁻\u0026bull;) radicals, which contribute to the degradation of dye molecules.\u003c/p\u003e \u003cp\u003eKinetic analysis of the photocatalytic degradation was carried out by plotting ln(A₀/At) versus time (Figs.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e and \u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e10\u003c/span\u003e). The linear relationship indicates that the degradation follows a pseudo-first-order reaction model. The rate constants (\u003cem\u003ek\u003c/em\u003e) for MO and BCG degradation were calculated to be 0.020 min⁻\u0026sup1; and 0.026 min⁻\u0026sup1;, respectively.\u003c/p\u003e \u003cp\u003eAdditionally, the degradation of dyes with NaBH₄ in the absence of MnO₂-NPs was also examined. Although NaBH₄ is a known reducing agent and thermodynamically favourable for breaking azo bonds in MO and BCG to form amino derivatives, the reaction proceeded very slowly due to kinetic limitations. In contrast, the presence of MnO₂ NPs provided an alternative reaction pathway with a lower activation energy, thereby enhancing both the thermodynamic and kinetic feasibility of dye degradation.\u003c/p\u003e \u003cp\u003eThese findings suggest that biosynthesized MnO₂ nanoparticles possess excellent photocatalytic capabilities and are promising candidates for environmental applications such as wastewater treatment.\u003c/p\u003e \u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003e4.1 Methyl Orange (MO):\u003c/h2\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec13\" class=\"Section2\"\u003e \u003ch2\u003e4.2 Bromocresol green (BCG)\u003c/h2\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"5. Conclusions","content":"\u003cp\u003eIn this study, manganese dioxide (MnO₂) nanoparticles were successfully synthesized via a green synthesis route using \u003cem\u003eLagerstroemia speciosa\u003c/em\u003e leaf extract as a natural reducing and stabilizing agent. The X-ray diffraction (XRD) analysis confirmed that the synthesized nanoparticles exhibit a polycrystalline tetragonal phase with an average crystallite size of 25.3 nm, as calculated using Scherrer\u0026rsquo;s equation. Field Emission Scanning Electron Microscopy (FESEM) revealed that the MnO₂ nanoparticles possess irregular, aggregated, and roughly spherical morphologies, with particle sizes ranging from 83 nm to 400 nm. The observed aggregation is attributed to the high surface energy and polarity of the nanoparticles, along with electrostatic interactions. These morphological features contribute to an increased surface area, which enhances the adsorption efficiency of the nanoparticles for dye degradation.\u003c/p\u003e \u003cp\u003eThe UV visible spectroscopy results showed a strong absorption peak at 365 nm, corresponding to the MnO₂ nanostructures, with a calculated optical band gap of 3.39 eV, indicating their potential for visible-light-driven photo catalysis. Photocatalytic degradation experiments demonstrated that the MnO₂ nanoparticles efficiently degraded both methyl orange and bromocresol green dyes within 60 minutes, achieving near-complete decolourization. The reduction in absorbance at 460 nm further confirms the complete degradation of the dye molecules.\u003c/p\u003e \u003cp\u003eOverall, the biosynthesized MnO₂ nanoparticles exhibit promising structural, optical, and photocatalytic properties, highlighting their potential for application in environmental remediation, particularly in the treatment of dye-contaminated wastewater.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eCompeting Interest\u003c/h2\u003e \u003cp\u003eThe authors declare no competing interest.\u003c/p\u003e\u003ch2\u003eFunding Statement:\u003c/h2\u003e \u003cp\u003eThe authors declare that no funds, grants, or other support were received during the preparation of this manuscript.\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eJagdish Arekar: Conceptualization, methodology, investigation, data curation, writing original draft preparation.Dipak Garole: Formal analysis, supervision, writing review and editing.R. S. Bendre: Resources, validation, project administration, supervision, funding acquisition.Yogesh R. Toda: Visualization, writing original draft preparation, software support, data curation, writing review and editing.All authors have read and approved the final version of the manuscript.\u003c/p\u003e\u003ch2\u003eAcknowledgement\u003c/h2\u003e \u003cp\u003eThe authors gratefully acknowledge the lab personnel of thin film laboratory, Pratap College, Amalner, School of Chemical Sciences, K.B.C. North Maharashtra University, Jalgaon and Directorate of Geology and Mining, Government of Maharashtra, Nagpur for their generous support during the research work.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eDr. G. Sakthi, and Dr. P. Saravanakumari, Green Synthesis of Manganese Oxide Nanoparticles using \u003cem\u003ePhyllanthusacidus\u003c/em\u003e, International J. of Multidisciplinary Educational Research, Vol. 10 Issue 4 (7) (April 2021) 112\u0026ndash;116.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSiddique M, Fayaz N, Saeed M, Synthesis, characterization, photocatalytic activity and gas sensing properties of zinc doped manganese oxide nanoparticles. Phys. Rev. B. Condens. Matter 602 (2021) 412504. https://doi.org/10.1016/j. physb. 2020.412504.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eM. Jayandran, M. MuhamedHaneefa, V. Balasubramanian, Green synthesis and characterization of Manganese nanoparticles using natural plant extracts and its evaluation of antimicrobial activity, Journal of Applied Pharmaceutical Science Vol. 5 (12) (December, 2015) 105\u0026ndash;110, DOI: \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.7324/JAPS.2015.501218\u003c/span\u003e\u003cspan address=\"10.7324/JAPS.2015.501218\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eChen HJ, Tian W, Ding W. Effect of preparation methods of the morphology of active manganese dioxide and 2, 4Dinitrophenol adsorption performance; Adsorption Science And Technology 36 (3\u0026ndash;4) (2018) 1100\u0026ndash;1111. DOI: \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.4172/2169-0022.1000172\u003c/span\u003e\u003cspan address=\"10.4172/2169-0022.1000172\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSagadevan S. Investigations synthesis, structural, morphological and dielectric properties of manganese oxides nanoparticles; Journal of Material Sciences \u0026amp; Engineering. 4(3) (2015) 1\u0026ndash;3.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eFeng L, Xuan Z, Zhao H, Bai Y, Guo J, Su CW, MnO prepared by hydrothermal method and electrochemical performance as anode for lithium-ion battery. Nanoscale Research Letters, 9 (290) (2014) 1\u0026ndash;8.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eS. Mitra, Y. Pak, N. Alaal, M.N. Hedhili, D.R. Almalawi, N. Alwadai, K. Loganathan, Y. Kumarasan, N. Lim, G.Y. Jung, I.S. Roqan, Novel P-Type Wide Band Gap Manganese Oxide Quantum Dots Operating at Deep UV Range for Optoelectronic Devices, Adv. Opt. Mater. 7 (21) (2019) 1900801\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eM. M. Najafpour, S. I. Allakhverdiev, Manganese compounds as water oxidizing catalysts for hydrogen production via water splitting: From manganese complexes to nano-sized manganese oxides, Int. J. Hydrogen Energy 37 (2012) 8753\u0026ndash;8764, \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/J.IJHYDENE.2012.02.075\u003c/span\u003e\u003cspan address=\"10.1016/J.IJHYDENE.2012.02.075\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eH.T. Zhang, X.H. Chen, J.H. Zhang, G.Y. Wang, S.Y. Zhang, Y.Z. Long, Z.J. Chen, N. L. Wang, Synthesis and characterization of one-dimensional K\u003csub\u003e0.27\u003c/sub\u003eMnO\u003csub\u003e2\u003c/sub\u003e-0.5H\u003csub\u003e2\u003c/sub\u003eO, J. Cryst. Growth 280 (1\u0026ndash;2) (2005) 292\u0026ndash;299.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eQ. Shu-yan, F. Jing, Y. Jun, Hydrothermal synthesis and super capacitor properties of urchin sphere and nanowire MnO\u003csub\u003e2\u003c/sub\u003e, Chinese J. Nonferrous Met. 18 (2008) 113\u0026ndash;117.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHaibin Lu, Xueyang Zhang, Ahmad Khan, Wenqiang Li, Lei Wan, Biogenic Synthesis of MnO2 Nanoparticles with Leaf Extract of \u003cem\u003eVoila betonicifolia\u003c/em\u003efor Enhanced Antioxidant, Antimicrobial, Cytotoxic and Biocompatible Applications, Frontiers in Microbiology, 12 (Nov. 2021) 761084; doi: \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.3389/fmicb.2021.761084\u003c/span\u003e\u003cspan address=\"10.3389/fmicb.2021.761084\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eK. S. Shaker, A. H. Abdalsalm, Characterization Nano Structure of MnO\u003csub\u003e2\u003c/sub\u003e via Chemical Method, Eng Technol. J. 36 (2018) 946\u0026ndash;950.10.30684/etj.36.9A.1\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSanjay S. Majani, SreelakshmiSathyan, MeghaVadakkethil, Manoj, Nimisha Vinod, Sushma Pradeep, Chandan Shivamallu, Venkatachalaiah K. N, Shiva Prasad Kollur, Eco-friendly synthesis of MnO nanoparticles using \u003cem\u003eSaracaasoca\u003c/em\u003e leaf extract and evaluation of \u003cem\u003ein vitro\u003c/em\u003e anticancer activity, Current Research in Green Sustainable Chemistry, 6 (2023) \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttp://doi.org/10.1016/j.crgsc.2023.100367\u003c/span\u003e\u003cspan address=\"10.1016/j.crgsc.2023.100367\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eA.Cauerhff, G. R. Castro, Bio-nanoparticles, a green nano - chemistry approach, Electronic Journal of Biotechnology, Review 16 (3) (2013) 1\u0026ndash;10. Available: www.ejbiotechnology.info DOI: 10.2225.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eA. G. Ingale, A. N. Chaudhari, Biogenic synthesis of nanoparticles and potential applications: an eco-friendly approach, Journal of Nanomedicene and Nanotechnology, 2 (2013) 1\u0026ndash;7. DOI: 10. 4172/2157-7439.1000165.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eIbrahim Mohamed Abouzeid Hasan, Hassan M. A. Salman, Olfat M. Hafez, Ficus-mediated green synthesis of manganese oxide nanoparticles for adsorptive removal of malachite green from surface water, Environmental Science and Pollution Research, 30 (2023) 28144\u0026ndash;28161, \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1007/s11356-022-24199-8\u003c/span\u003e\u003cspan address=\"10.1007/s11356-022-24199-8\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAKM Atique Ullah, Md. Mahbubul Haque, MahmudaAkter, AHossain, Md. Mottaleb Hosen, AKM Fazle Kibria, MNI Khan and MKA Khan, Green synthesis of Bryophyllumpinnatum aqueous leaf extract mediated bio-molecule capped dilute ferromagnetic α-MnO\u003csub\u003e2\u003c/sub\u003e nanoparticles, Mater. Res. Express 7 (2020) 015088, DOI: \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1088/2053-1591/ab6c20\u003c/span\u003e\u003cspan address=\"10.1088/2053-1591/ab6c20\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMadhumitha G, Fowsiya J, Gupta N, Kumar A, Singh M, Green synthesis, characterization and antifungal and photocatalytic activity of Pithecellobium dulce peel mediated ZnO nanoparticles, J Phys. Chem. Solids 127 (2019) 43\u0026ndash;51, \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.jpcs.2018.12.005\u003c/span\u003e\u003cspan address=\"10.1016/j.jpcs.2018.12.005\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eIbrahim Mohamed Abouzeid Hasan, Hassan M. A. Salman, Olfat M. Hafez, Ficus-mediated green synthesis of manganese oxide nanoparticles for adsorptive removal of malachite green from surface water, Environmental Science and Pollution Research 30 (2023) 28144\u0026ndash;2816, \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1007/s11356-022-24199-8\u003c/span\u003e\u003cspan address=\"10.1007/s11356-022-24199-8\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eY. Dessie, S. Tadesse, R. Eswaramoorthy, Physicochemical parameter influences and their optimization on the biosynthesis of MnO\u003csub\u003e2\u003c/sub\u003e nanoparticles using Vernonia amygdalina leaf extract, Arab J Chem. 13 (2020) 6472\u0026ndash;6492. https://doi.org/10. 1016/j. arabjc.2020. 06. 006.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eS. Karnchanawong and P. Limpiteeprakan, Evaluation of Heavy Metal Leaching from Spent Household Batteries Disposed in Municipal Solid Waste, Waste Management, Vol. 29, No. 2 (2009) 550\u0026ndash;558. doi:\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.wasman.2008.03.018\u003c/span\u003e\u003cspan address=\"10.1016/j.wasman.2008.03.018\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSusana M Xar\u0026aacute;, Julanda N Delgado, Manuel Almeida, Carlos A. V. Costa, Laboratory study on the leaching potential of spent alkaline batteries, Waste Management 29(7) (April- 2009) 2121\u0026ndash;31, DOI: \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.wasman.2009.03.010\u003c/span\u003e\u003cspan address=\"10.1016/j.wasman.2009.03.010\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eM Mylarappa, V Venkata Lakshmi, K R Vishnu Mahesh, H P Nagaswarupa, N Raghavendra; A facile hydrothermal recovery of nano sealed MnO\u003csub\u003e2\u003c/sub\u003e particle from waste batteries: An advanced material for electrochemical and environmental applications, IOP Conf. Series: Materials Science and Engineering 149 (2016) 012178, doi:\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1088/1757-899X/149/1/012178\u003c/span\u003e\u003cspan address=\"10.1088/1757-899X/149/1/012178\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eJannatun Zia, Elham Aazam, Ufana Riaz, Synthesis of nanohybrids of polycarbazole with α-MnO2 derived from Brassica oleracea: a comparison of photocatalytic degradation of an antibiotic drug under microwave and UV irradiation, Environmental Science and Pollution Research 27(19) (July 2020) 24173\u0026ndash;24189, \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1007/s11356-020-08149.w\u003c/span\u003e\u003cspan address=\"10.1007/s11356-020-08149.w\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eVahid Hoseinpour, MahsaSouri, Nasser Ghaemi, Green synthesis, characterisation, and photocatalytic activity of manganese dioxide nanoparticles, Micro \u0026amp; Nano Letters, 13, Iss. 11 (2018) 1560\u0026ndash;1563; doi:\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1049/mnl.2018.5008\u003c/span\u003e\u003cspan address=\"10.1049/mnl.2018.5008\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKollur Shiva Prasad and Alakananda Patra, Green synthesis of MnO\u003csub\u003e2\u003c/sub\u003e nanorods using Phyllanthus amarus plant extract and their fluorescence studies, Green Processing and Synthesis, 6 (2017) 549\u0026ndash;554; \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1515/gps-2016-0166\u003c/span\u003e\u003cspan address=\"10.1515/gps-2016-0166\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMamun M A A, Noor M, Ullah A K M A, Hossain M S, Matin M A, Islam F and Hakim M A, Effect of CePO\u003csub\u003e4\u003c/sub\u003e on structural, magnetic and optical properties of ceria nanoparticles, Mater. Res. Express 6 (1) (2018) 016102, DOI \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1088/2053\u0026thinsp;\u0026ndash;\u0026thinsp;1591/aae2d0\u003c/span\u003e\u003cspan address=\"10.1088/2053\u0026thinsp;\u0026ndash;\u0026thinsp;1591/aae2d0\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eA. Bystrom and A. M. Bystrom, The crystal structure of hollandite, the related manganese oxide minerals, and α-MnO2, Acta Cryst. 3 (1950) 146\u0026ndash;54, \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1107/S0365110X5000032X\u003c/span\u003e\u003cspan address=\"10.1107/S0365110X5000032X\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMariya Moeen, Shazia Nouren, Maria Zaib, Ismat Bibi, Abida Kausar\u0026amp;Misbah Sultan, Green synthesis, characterization and sorption efficiency of MnO\u003csub\u003e2\u003c/sub\u003e nanoparticles and MnO\u003csub\u003e2\u003c/sub\u003e@waste eggshell nanocomposite, Journal of Taibah University for Science, 16 No. 1 (2022) 1075\u0026ndash;1095; \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1080/16583655.2022.2139483\u003c/span\u003e\u003cspan address=\"10.1080/16583655.2022.2139483\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eA. Martin Joseph and R. Thilak Kumar, Formation and investigation of low dimensional super paramagnetic α-manganese dioxide nanostructures, Materials Research Express, Vol. 5 No. 1(Jan. 2018); DOI: \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttp://dx.doi.org/10.1088/2053-1591/aa9e5d\u003c/span\u003e\u003cspan address=\"10.1088/2053-1591/aa9e5d\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eYuXin Zhang, Shijin Zhu, Meng Dong, Chuan Pu Liu, Zhong Quan Wen, Hydrothermally Tailoring Low-dimensional MnO\u003csub\u003ex\u003c/sub\u003e Nanostructure and Their High Electrochemical Performance, International Journal of Electrochemical Science, Vol. 8, Issue 2 (Feb 2013) 2407\u0026ndash;2416; \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/S1452-3981(23)14318-5\u003c/span\u003e\u003cspan address=\"10.1016/S1452-3981(23)14318-5\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"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":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"MnO₂-NPs, green synthesis, Lagerstroemia speciosa, photo catalysis, UV–Vis–IR, XRD, FESEM, dye degradation","lastPublishedDoi":"10.21203/rs.3.rs-6715891/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6715891/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eManganese oxide nanoparticles (MnO₂-NPs) were biosynthesized using an aqueous extract of \u003cem\u003eLagerstroemia speciosa\u003c/em\u003e leaf powder. The plant is rich in phytochemicals such as phenolic compounds, alkaloids, α-amino acids, steroids, organic acids, terpenoids, reducing sugars, glycosides, carbohydrates, saponins, starch, flavonoids, and tannins. The phenolic compounds acted as both reducing and capping agents. The synthesized nanoparticles were characterized using UV\u0026ndash;Vis\u0026ndash;IR spectroscopy, X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and Fourier-transform infrared spectroscopy (FTIR). The UV\u0026ndash;Vis\u0026ndash;IR spectrum revealed a distinct absorption peak at 365 nm, confirming the formation of MnO₂-NPs. FESEM images indicated rough, spherical, randomly oriented particles with sizes ranging from 83\u0026ndash;400 nm. XRD analysis confirmed a pure tetragonal structure with preferential (110) plane orientation. The photocatalytic performance of the MnO₂-NPs was assessed via the sunlight-driven decolourization of methyl orange (MO) and bromocresol green (BCG) dyes.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e","manuscriptTitle":"Tetragonal MnO₂ Nanoparticles Synthesized via Lagerstroemia speciosa: Structural Characterization and Photocatalytic Potential","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-06-03 01:18:50","doi":"10.21203/rs.3.rs-6715891/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"892723e0-6844-4035-b0ee-82d920f07e9d","owner":[],"postedDate":"June 3rd, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-06-20T13:08:40+00:00","versionOfRecord":[],"versionCreatedAt":"2025-06-03 01:18:50","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6715891","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6715891","identity":"rs-6715891","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}