Effect of Chitosan loading towards structural, optoelectronic and photocatalytic degradation of flakes like CuO-Chitosan nanocomposite

Effect of Chitosan loading towards structural, optoelectronic and photocatalytic degradation of flakes like CuO-Chitosan nanocomposite | 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 Research Article Effect of Chitosan loading towards structural, optoelectronic and photocatalytic degradation of flakes like CuO-Chitosan nanocomposite Laraib Bibi, Saba Afzal, Madina ., Ishrat Fatima, Rabia Naeem, and 2 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7982430/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 The development of a stable and extremely active photocatalyst has attracted substantial consideration in the area of wastewater treatment and photoelectrocatalytic (PEC) water splitting. In recent work, flakes-like CuO–chitosan nanocomposites were effectively synthesized to investigate the impact of chitosan loading on their structural, photocatalytic degradation of Methylene blue (MB) and optoelectronic characteristics. The CuO–chitosan nanocomposites were prepared via a simple co-precipitation route by varying chitosan contents (0.1 g (CCu1), 0.3 g (CCu3), and 0.5 g (CCu5)). FTIR and X-ray diffraction (XRD) confirmed the structural studies like monoclinic phase of CuO, its smaller crystallite size was observed with increased chitosan concentration. SEM/EDX analyses revealed a flakes-like morphology and composition with enhanced surface uniformity and reduced agglomeration upon chitosan incorporation. The optical performance of CuO-Chitosan nanocomposites was assessed with UV by evaluating optical band gaps of CCu1(3.34eV), CCu3(3.32eV), and CCu5 (3.29eV), suggesting CS incorporation effectively reduce band gap of pure CuO (3.36 eV). Photocatalytic degradation investigations revealed that optimized chitosan loading significantly enhanced degradation efficiency of CCu5 which shows 93 % degradation of methylene blue (MB) within 150 min under visible light. The optoelectronic characteristics of all four samples were tested by LSV, EIS and MS plots. Among them CuC5 depicts higher current density, low charge transfer resistance and greater electron Donar density (Nd =8.4×10 12 cm 3 ) as compared to CuC1, CuC3 and CuO respectively. The results highlight that controlled chitosan loading effectively modify the physicochemical, photocatalytic dye degradation and optoelectronic properties of CuO, making them promising candidates for environmental remediation and photocatalytic applications. CuO-Chitosan Nanocomposites Optical band gap Photodegradation Methylene blue optoelectronic properties Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 1. Introduction The growing global energy demand and rapid depletion of fossil fuels have strengthened the search for clean, renewable, and sustainable energy sources[ 1 – 5 ].The rapid progress of the socio-economy and chemical industry give rise to in the release of huge amount of wastewater comprising antibiotics and dyes into water bodies, leading to water pollution[ 6 , 7 ]. This poses a risk to ecology, human health, and the environment, creation of problem that involves consideration[ 5 ]. With the passage of time, numerous techniques for the elimination of poisonous components in wastewater have sustained to be developed, such as membrane separation, adsorption, and photocatalytic technology. Amongst these methods, semiconductor photocatalysis had developed as one of the most vital and auspicious technique due to its easy handling, better reproducibility, simplicity, cost-effective performance, and environment benign [ 6 ]. Previous literature had studied various semiconductors as effective photocatalysts, such as Mn 2 O 3 [ 8 ], CdO, ZnO[ 9 ], TiO 2 , SnO 2 , CuO, Fe 2 O 3 and CoTiO 3 [ 10 , 11 ]. Amongst various semiconductor metal oxide materials, like CuO nanostructure has attracted important attention due to its high reactivity, narrow band gap with monoclinic crystal structure and their large surface volume displays notable applications in catalysis[ 12 , 13 ]. The morphology of CuO NPs rely on numerous factors such as electrolyte concentration, reaction temperature, pH, precursor concentration, and kind of capping agent. A small alteration in reaction parameters can affect the physiochemical properties of CuO NPs. Similarly, the photocatalytic performance of CuO NPs depend upon their charge separation and agglomeration of NPs during photodegradation process. To avoid the agglomeration of NPs and maintain better charge separation the functionalization of NPs by a biopolymer can be taken into consideration[ 14 ]. CS is a natural polymer that is biodegradable, nontoxic, low-cost and environmentally safe [ 15 , 16 ]. CS has also durable affinity toward metal ions due to the presence of very reactive NH 2 and OH groups in its structure, and therefore leading to CS-CuO nanocomposite more active which enhances its adsorption and attractive effects towards treatment of organic pollutants[ 16 , 17 ]. Furthermore, CS proficiently improve the lifetime of photogenerated electrons of CuO, tuning the characteristics of charge separation, later enlightening the photocatalytic activities[ 18 – 20 ]. Combination of transition metal-oxide semiconductors with biopolymers such as chitosan (CS) produces hybrid composite materials that can link the necessities of optical properties, charge transfer, and surface functionality. Transition Metal oxides like SnO 2 . [ 21 ]TiO₂, ZnO, CuO,[ 1 , 8 , 22 ] and numerous doped metal oxides offer necessary electronic band positions and strong light absorption while CS play a role of film making capability, abundant surface functional groups (–NH₂, –OH) and tunable adsorption features [ 1 , 20 ]. This interaction is beneficial for optoelectronic devices where interfacial charge transport, surface morphology and ideal energy gap, are important in photodetectors, Photoelectrochemical (PEC) electrodes, photovoltaics, and sensors[ 23 – 25 ]. Studies regarding ZnO–CS, CuO–CS and TiO₂–CS [ 6 , 22 ] nanocomposites reported that reasonable transition metal oxide loading as photoelectrodes (e.g., CuO–CS) [ 26 ], can modify surface topography under PEC conditions and improve charge separation at the electrode–electrolyte interface. Most of the literature display enhanced photocurrent stability and retard photo corrosion when CS play a role of passivating and hydrophilic interlayer. Previous literature illustrates that CS increases photocatalytic elimination of dyes and pollutants when mutual with TiO₂, ZnO or other metal oxides, improves adsorption of pollutants, reduced charge recombination, and enabled reactive species production[ 7 ]. The present study emphases on the synthesis of CuO NPs are at 30°C, 60°C and 80°C. The CuO prepared at 80°C are considered optimum and these optimize NPs are utilized for coating by CS at various concentrations. The impact of chitosan loading on the physiochemical, optical and photoelectrocatalytic properties of nanocomposite samples is assessed. The phoyodegradation efficacy of CuO-CS nanocomposite is evaluated by using Methylene blue dye (MB). The twining of CuO with CS expected to improve charge separation, increase adsorption of pollutant on catalyst surface, suppress catalyst agglomeration and hence elevate overall photodegradation and optoelectronic performance. 2. Materials and Method 2.1. Materials Copper acetate monohydrate (Cu(C 2 H 3 O 2 ) 2 .H 2 O (99.5%), Sodium hydroxide (NaOH) (99.8%), CS biopolymer (medium, molecular weight, 75–85% deacetylated) and Glacial acetic acid (CH 3 COOH) (100%) were purchased from Sigma Aldrich. Ethanol (99.8%) was purchased from RCI Lab scan, Thailand and MB dye was purchased from MERCK, Germany. Distilled water was used as a solvent throughout the experiment and all the chemicals are used without further purification. 2.2. Synthesis of CuO NPs by Co-precipitation method CuO NPs are synthesized by a straightforward co-precipitation process at room temperature (30°C). 0.02 M solution of Cu(C 2 H 3 O 2 ) 2 .H 2 O is prepared in 300 ml of distilled water. The solution is stirred with a magnetic bar for about 15 to 20 minutes at room temperature with 1 mL of CH 3 COOH. An aqueous solution of 1 M NaOH is prepared which acts as a reducing agent. The solution is added to the mixture dropwise until the pH is adjusted around 9 and 11. The NaOH solution gives OH groups that react with copper salt to produce copper hydroxide Cu(OH) 2 . The pH adjustment changes the solution's color from blue to black. After an hour remove the product from stirring and then washed with ethanol and water to purify the sample. Moreover, dry the sample at 60°C for approximately 5–6 hours to produce the final product. Two more samples of CuO are prepared at 60°C and 80°C using the same method to determine the optimum synthesis temperature for CuO NPs as represented in Figure S1 . 2.3. Synthesizes of CuO-CS nanocomposite. Firstly, the solution of CS is prepared at three different concentrations (0.1, 0.3, and 0.5 g) in 100 ml of 2% (v/v) acetic acid. Secondly, the as prepared CuO NPs (0.5 g) dissolve 250 ml of double-distilled water in a round-bottom flask and sonicate the mixture for approximately half an hour. Now add the solution of CuO NPs to the CS solution (0.1 g) and stir for approximately 45 minutes. The pH of this solution is adjusted to 10–11 by adding 1M of NaOH. The mixture is heated over water bath at 80°C for about 2 hours to get a homogeneous product. The product is then centrifuged at 8000 rpm, washed with excess ethanol and distilled water and dried in an oven at 60°C. the product is labeled as CCu1 in scheme 1 . The same procedure is used to prepare CuO-CS nanocomposites with other CS concentrations (0.3 and 0.5 g) and the products are labeled as CCu3 and CCu5 respectively. 2.4. Characterization techniques The surface morphology of NPs and nanocomposites was determined by SEM. The chemical nature or elemental composition of materials was analyzed by EDX analysis, JSM-IT800. Additionally, the crystal phase, size and crystallinity are determined through XRD (Bruker D2 PHASER XR, 2nd Generation) at 2 theta value between 20–80° range. Functional group identification and chemical bonding within the molecules is carried out by FTIR spectrophotometer (ALPHA-E) in the range of 500–4000 cm − 1 . UV-Vis (Shimadzo-1800 UV) is used to assess the photodegradation process and and identification of compounds within the wavelength ranging from 300–800 nm. 2.5. Photocatalytic activity MB dye is used as a model pollutant to examine the photocatalytic activity of all nanocomposite samples and pure CuO NPs. The photocatalytic process is carried out in a reactor equipped with 200 W halogen lamp as a source of visible light. At first 20 ppm solution of MB dye is prepared in 1 L of distilled water. A 0.30 g of pure CuO NPs are added into 100 ml to as prepared dye solution. The adsorption-desorption equilibrium was determined by stirring the solution in the dark for approximately half an hour before exposing it to visible light. The dye solution is then placed under a halogen bulb with continuous stirring, and a 5 mL sample of dye is taken off every 30 min and analyzed by UV-Vis spectrophotometer at around λmax = 664 nm. The whole photodegradation process is conducted at room temperature at time interval of ranging from 0 to 150 min. The same process is applied to all nanocomposite samples to assess and compare the adsorption-photodegradation. 2.6 Optoelectronic measurements Optoelectronic measurements were conducted in a conventional three-electrode workstation, with a saturated-potassium-chloride, silver/silver chloride electrode (Ag/AgCl-3M KCl) as a reference electrode and a platinum wire as a counter electrode. The CuO, CuC1, CuC3 and CuC3 electrodes used as the working electrodes on FTO substrate by drop casting method. The electrolyte was composed of 0.5M KOH solution. Linear scan voltammetry (LSV) was evaluated by a Princeton Applied Research PAR-VersaSTAT-3 electrochemical workstation. The potential window of -300 mV to + 1000 mV vs. Ag/AgCl at a scan rate of 20 mV s − 1 . The charge transfer resistance and lifetime of photo-generated charge carriers was calculated by Nyquist and Bode phase. A 150 W UV lamp with power density of 100 mW.cm − 2 was employed as a source of light. 3. Results and Discussion 3.1 Structural studies XRD analysis is used to determine the crystal phase, chemical nature, grain size, and degree of crystallinity of CuO NPs and composite samples, X-ray diffraction spectra were taken by using XRD (Bruker D2 PHASER XR, 2nd Generation) at 2θ value between 20–80° range. In the Figure S2 prominent peaks corresponding to the (hkl) values of (110), (111), (202), (020), (202), (113), (311), and (004) respectively, which are the characteristics peaks of CuO NPs. All these peaks showed that CuO NPs are successfully synthesized in mild experimental conditions and match with literature data[ 8 ]. The diffraction peaks were identified as the monoclinic phase of CuO NPs. Using the Scherrer equation (D = K λ / Β COS θ), the average crystallite size of CuO NPs was calculated (Table 1). This indicated that by increasing synthesis temperature, high intensity and narrower diffraction peaks are obtained which corresponds to the smaller crystal size. The estimated crystallite or grain size for pristine CuO NPs and CuO-Chitosan composites are in nanometer range and decreases from 54nm (CuO 80 o C) to 20nm (CCu5) due to increasing content of Chitosan as illustrated in Table 1. Figure 1 indicates the XRD spectra of composite samples prepared on varying CS concentrations. As CS is semi-crystalline, therefore by compositing it with Cu metal the results in broader and less intense diffraction peaks. Therefore, by increasing CS concentration peaks became broader and less intense from CCu1 to CCu5 that confirms the interaction between Cu metal and CS [ 27 ]. It showed the intensity and position of diffraction peaks, which approve the existence of CuO in all the nanocomposites and the particles are of monoclinic crystal system in accordance with literature, (JCPDS, File No 01-080-1916). CuO exhibits the monoclinic CuO phase with reflections at about 2θ = 32.2 o , 35.05 o , 38.07 o , 48.1 o , 52.8 o , 57.5 o , 61.1 o , 65.5 o , 67.6 o , 72.02 o , 74.7 o with the lattice plan of (110), (-111), (111), (-202), (020), (202), (-113), (-311), (220), (311), and (004) respectively[ 1 ]. Sharp well-defined peaks indicate the crystalline nature of the CuO. At temperature 30 o (room temperature) peak at 16 o -17 o show the presence of Cu(OH) 2 at temperature 60 o conversion of Cu(OH) 2 occur [ 2 ]. At 80 o temperature totally converted into monoclinic CuO. In the Fig. 1 a CuO-CS nanocomposites with less intensities have observed. A broad amorphous hump at 2θ = 18 o -22 o confirmed the formation of CuO-CS. Broad hump indicates the semi-crystalline nature of the chitosan. When CuO combine with chitosan, CuO peaks remain visible with low intensities. The CS concentration also impact on particle size which gradually decrease from CCu1 to CCu5. The decrease in particle size can be associated with better optoelectronic, adsorption and phodegradation performance towards dye molecule. Table.1. Band gap and particle size of CuO NPs (30°C, 60°C and 80°C) and nanocomposites (CCu1, CCu3 and CCu5). CuO NPs (°C)/CS-CuO Nanocomposites Wavelength (nm) Particle Size (nm) Band gap (eV) 30°C 360 50 nm 3.44 eV 60°C 364 52 nm 3.40 eV 80°C 368 54 nm 3.36 eV CCu1 377 24 nm 3.34eV CCu3 380 22 nm 3.32 eV CCu5 384 20 nm 3.29eV Two prominent peaks at 34.6° and 37.7° are considered as backbone of nanocomposite that showed the interaction between CS and CuO NPs. The FTIR spectra of CuO NPs are presented in Fig S3. The vibrational bands of CuO NPs synthesized at various temperatures are observed in the range of 606cm − 1 to 863cm − 1 corresponding to the Cu-O bond, indicating the successful formation of metal oxide. The frequency band at 1112 cm − 1 and 1104 cm − 1 shows the C = C stretching bond and the peaks that appeared at 1420 cm − 1 and 1427 cm − 1 correspond to the C-O bonds, respectively. Peaks in the range of 2345–2907cm − 1 are due to C = O stretching. This peak is due to the use of organic reactants during CuO synthesis. These organic molecules typically contain carbonyl groups (C = O), and traces of these molecules can remain adsorbed on the surface NPs leading to the appearance of C = O stretching vibrations. The absorption peaks in the range of 3773–3835 cm − 1 is due to the O-H stretching group of water molecules (Nithya et al., 2014). It is observed some of the IR bands (14000–40000 cm − 1 ) decrease in intensity and by increasing temperature (80°C). Likewise, Fig. 2 depicts the FTIR spectrum of composite samples which indicates the slight shifting and appearance of stretching mode of O-Cu-O in the ranges of 700–839 cm − 1 . This shifting to the higher wavenumber might be due to coating of CuO NPs with CS. The peaks at 1115 − 1110 cm − 1 ) are due to β (1–4) glycosidic bond in polysaccharide units of CS. The IR band located at 1437 − 1424 cm − 1 corresponded to the OH group of CS. While the bands around 1601 cm − 1 , 1566 cm − 1 and 1552 cm − 1 are allocated to the NH 2 stretching of amide groups. The peaks observed around 2899–2922 cm − 1 are responsible for CH 2 and CH 3 bands of CS chains. Furthermore, the peak at 3570–3857 cm − 1 is due to the intermolecular H-bonding and NH 2 stretching bands. The peak intensity decreases gradually with slight shifting is due to increase in CS concentration that is an evidence for the coordination of CuO molecules with the CS functional groups (NH 2 , OH)[ 28 ]. 3.2. Morphological studies SEM image of CuO NPs captured at a magnification of 1 um is presented in Fig. 3 . The surface morphology showed a thick, flakes-like structure might be due to the agglomeration of particles that form clusters at ambient temperature. According to SEM results, room temperature synthesis of CuO NPs is an appropriate condition for achieving homogeneity and uniform dispersion of CuO NPs. Similar outcomes have also been previously reported [ 29 ]. Figure 3 (a, b, c) shows that CCu nanocomposite samples displayed a thin flakes-like morphology, as CS biopolymer acts as a stabilizing agent and prevent particle agglomeration. This indicates that the CS polymer was dispersed uniformly on to the surface of CuO NPs. Elemental composition of CuO NPs is illustraed in the Fig. 4 . The spectra exclusively showed copper (Cu) and oxygen (O) elements without additional elemental impurities confirming their purity. The most intense peak in (CuO NPs) spectra is of Cu, indicating a Cu rich composition in the metal NPs. The Fig. 4 (a, b, c) shows the relative percentages of elements in composite samples. The spectra of CCu1 (a) contain C, O, and Cu components in the range of 21.09%, 22.49%, and 56.42% respectively. The elemental composition of C, O, Cu, and N in CCu3 is 11.61%, 24.15%, 67.11%, and 0.13%. Similarly, the EDX of CCu5 indicate C, O, Cu and N in the range of 11.41%, 19.82%, 67.02%, 1.74% respectively and no other impurities were detected. As CCu1 contained the least amount of CS therefore, no peak was observed for the N element, and only weak signals for oxygen, carbon, and copper were detected. Similarly, CCu5 is with highest CS concentration showed higher nitrogen signal. The developed structure of CuO NPs and the CS-CuO nanocomposite indicated that there are no additional impurities as evident from the elemental composition. 3.3. Optical studies The UV results of CuO NPs are displayed in Fig S4 which showed a maximum wavelength of CuO prepared at 30, 60 and 80°C at 360, 364, and 368 nm respectively[ 13 ]. This red shift by increasing temperature is a clear indication that the temperature has an impact on UV absorption peaks. The characteristic absorbance peaks of composite samples are presented in Fig. 5 . The nanocomposite samples CCu1, CCu3, and CCu5 shows peaks at nanocomposite at the wavelength of 377, 380, and 384 nm respectively[ 30 ]. This indicates a red shift in UV absorption bands by increasing CS concentration. The Band gap energy of all the samples is calculated using Tauc equation as reported in the literature[ 31 ]: As shown in Table 1. The rise in temperature during the preparation of CuO NPs, an absorption peak shift to a larger wavelength thus reduces the band gap. It indicates that thermal energy can promote particle growth, often resulting in larger CuO NPs which shows that temperature influences the band gap. The optical band gap of nanocomposites displayed that the optical band gap energies reduce as the concentration of CS increases as mentioned in Table 1. This indicates that the red shift wavelength accredited to smaller crystallite size, enhances the composite surface area which in turn improves its efficacy toward the photodegradation of organic dyes 3.6. Photocatalytic degradation of Methylene blue ( MB) The photocatalytic performance of synthesized pure CuO NPs and all CuO-CS nanocomposites was examined by decoloring 20 mg/L of MB solutions. Adsorption of MB was performed under darkness to establish adsorption-desorption equilibrium between the catalysts and dye molecules. Figure 7 (a) presented the rate of degradation under visible light exposure. In Fig. 8 (b) Experiments were conducted and the rate of degradation with the presence catalyst reached about 62% respectively. The results show that the maximum adsorption is attained with CCu5 nanocomposite followed by CCu1 and CCu3. The quantity of protonated surface amino groups on the photocatalyst surface that interacted with the MB compounds was correlated with this adsorption pattern. Because the concentration of protonated surface amino groups was lower in CCu1 than in CCu3, MB adsorption was lower in those samples. Furthermore, CCu5 degraded about 93% of the dye within 150 min, which is higher higher as compared to CCu3 and CCu1, due to the modification of catalyst surface by the interaction among CS which increases its active sites and effects the catalytic activity of CuO NPs against dye degradation[ 12 ]. Hence, CCu5 showed effective photocatalytic activities against MB dye as CS provides additional active sites for binding dye molecules. With a higher CS concentration, more dye molecules can interact. It is obvious that the concentration of dye declines with time by increasing the loading of CS [ 30 ]. % Degradation of dye was calculated by using equation: Degradation (%) = (1-( C 0 /C e ) × 100 Where C 0 corresponds to the initial concentration and C e is the final concentration of Methyl Blue dye. This equation displays the percentage of dye degradation. By considering all the characterization results the morphology, and crystalline structure of nanoparticles all play an important role in photocatalytic behavior. According to the report, the size and shape of NPs, the energy transfer process, as well as the production and consumption of photo-generated carriers, significantly influence the catalytic activity of nanocatalysts [ 28 ]. Meanwhile, under visible light irradiation (Fig. 8 ), oxygen molecules absorbed on the surface of catalysts formed superoxide radicals (O 2 ) radicals. These radicals react with a dye or other organic molecule, resulting in their conversion into harmless products, like H 2 O and CO 2 molecules[ 12 ]. 4. Optoelectronic properties: The optoelectronic studies of CuC1, CuC3, CuC5 and CuO photoelectrodes were deposited on FTO was performed using a standard 3-electrode electrochemical cell in 0.5 M KOH as an electrolyte solution[ 32 ]. The photocurrent was calculated in the presence of UV light. Figure 9 describes that the linear scan voltammograms (LSV) of all four electrodes under dark and light conditions. On scanning the potential from − 300mV to + 1000 mV under light, the photocurrent density of 8.4, 3.8, 2.1 and 1.9 mA/cm 2 was found for CuC1, CuC3, CuC5 and CuO against applied potential of 0.8 V vs. Ag/AgCl. This increase in photocurrent density forCuC5, proposes that the charge separation is enhanced in the CuC5 photoanode as compared toCuC3, CuC1 and CuO, respectively. Furthermore, an electrochemical impedance spectrum (EIS), was valuable to find out the indication about increase charge transfer gradient approach at the interface of photoelectrode -electrolyte and separation efficiency of charge[ 33 ]. Figure 10 exhibits the EIS Nyquist plots of the CuC1, CuC3, CuC5 and CuO photoelectrodes in the frequency range of 0.1 Hz to 10 kHz under light. Figure 10 displays that the CuC5 electrode displays the minimum impedance semicircle and has lesser charge transfer resistance (R ct ) value than the other controlled samples CuC3, CuC1 and CuO electrode. Mostly, a smaller semicircle in EIS Nyquist plot agrees the effective charge carrier separation and a rapid interfacial charge transfer mechanism. This recommends CuC5 remarkably enhances the motion of electrons by reducing the recombination of electron–hole pairs and helping to enable the photocatalytic activity. The Mott–Schottky (MS) investigations of CuC1, CuC3, CuC5 and CuO were employed at frequency of 1 kHz in 0.5 M KOH solution in the presence of UV light. MS demonstrate the electron density of ternary CuC5(8.4× 10 12 cm 3 ) is higher as compared to CuC3 (6.2× 10 10 cm 3 ), CuC1 (4.3× 10 10 cm 3 ) and CuO (1.2× 10 10 cm 3 ) are measured by the equation mentioned in literature [ 34 ]. Furthermore, the flat band potential (E fb ) measured from the x-axis intercept of the MS plot showed in Fig. 11 . Table 2 depicts the the flat band potential of the CuC5 (− 0.63) V/Ag/AgCl, is lesser than CuC3(− 0.41 V/Ag/AgCl), CuC1 (− 0.39 V/Ag/AgCl) and CuO (+ 0.31 V/ Ag/AgCl), respectively, which determine the enhanced route of the photogenerated carriers. Table.2. Current density, Charge transfer resistance, Flat and potential and electron donar density of CuO and nanocomposites (CCu1 CCu3 and CCu5) respectively. Electrodes R ct (Ω) Current density (mA/cm 2 ) E fb (e.V) N D (cm 3 ) CuC5 0.40 8.4 -0.63 8.4×10 12 CuC3 300.3 3.8 -0.41 6.2×10 10 CuC1 650 2.1 -0.39 4.3×10 10 CuO 834 1.9 + 0.31 1.2×10 10 4. Conclusion In this work CuO NPs were successfully synthesized by facile co-precipitation method at different temperatures (30°C, 60°C and 80°C). Furthermore, comparative studies of CuO-chitosan nanocomposites by using different CS concentrations (0.1 g, 0.3 g, and 0.5 g) is carried out. Characterization results discovered effective integration of chitosan on CuO surface and the concentrations of CS were detected to significantly affect the morphology, crystallite size and catalytic behavior of nanocomposite. Moreover, optical and photocatalytic degradation studies of CuO-Chitosan nanocomposites were examined via UV Visible spectroscopy, optical band gap tuning (3.36 to 3.29eV) revealed that CuC5 sample show 93% decolorization, higher adsorption properties due to increased surface area, availability of functional groups for binding and better dispersion of CuO NPs. While optoelectronic investigations were also revealed that CuC5 nanocomposite exhibits higher current density, lower charge transfer resistance, and high electron Donar density due to the homogeneous dispersion of CS and improved interaction among CuO NPs and CS polymer. These findings recommends that CCu5 nanocomposite is a promising candidate for photodegradation of MB and photoelectrochemical activity which is an economical and eco-friendly process. Declarations Acknowledgment The authors gratefully acknowledge support from the Department of Chemistry, Sardar Bahadur Khan Women’s University, Quetta, Pakistan and Department of Chemistry, Government College University Lahore, Pakistan; the author also acknowledges HEC (Pakistan), NRPU Research Grant # 20-17618/NRPU/R&D/HEC/2021-2020. Competing Interests The authors have no relevant financial or non-financial interests to disclose. Author Contributions Laraib Bibi Methodology, Investigation, Conceptualization, Writing - Original Draft, Methodology, Investigation, Saba Afzal, Madina: Conceptualization, Supervision, Formal analysis, Investigation Ishrat Fatima, Rabia Naeem, Bibi Sherino, Huma Tareen: Writing - Review & Editing, Investigation, Formal analysis, and Interpretation data Analysis. Data availability The datasets generated during and/or analyzed during the current study are available from the corresponding author on reasonable request. AI tool: The manuscript was entirely human-written and Turnitin tool is used as an AI Detection feature which help to identify the AI-generated content in submitted manuscript References Ehsan, M.A., et al., Facile fabrication of CeO2–TiO2 thin films via solution based CVD and their photoelectrochemical studies. Journal of Materials Science: Materials in Electronics, 2018. 29 (15): p. 13209-13219. Mansoor, M.A., et al., A Tri-Metallic (Mn–Co–Ti) Oxide Photoanode with Improved Photo-Conversion Efficiency. Russian Journal of Inorganic Chemistry, 2021. 66 : p. 806-813. Hassan, F., et al., Composite electrodes with superior catalytic activity in methanol electro-oxidation fabricated using ternary NiO–CuO–ZnO mixed metal oxides. New Journal of Chemistry, 2024. 48 (8): p. 3614-3623. Irfan, M.F., et al., Structural, morphological, and electrocatalytic investigations of Fe 3 O 4-doped Mn 3 O 4 composite supported on carbonaceous materials derived from chitosan for oxygen reduction reaction. New Journal of Chemistry, 2025. 49 (6): p. 2308-2318. ul-Ain, M., et al., Enhancing Cr(VI) remediation efficiency using hemp-derived biochar: insights into RSM optimization and adsorption kinetics using ANN modelling. International Journal of Environmental Science and Technology, 2025. 22 (15): p. 15189-15210. Afzal, S., et al., Impact of chitosan on CS/TiO2 composite system for enhancing its photocatalytic performance towards dye degradation. DESALINATION AND WATER TREATMENT, 2023. 283 : p. 274-279. Mansoor, M.A., et al., Aerosol-assisted facile fabrication of bimetallic Cr2O3–Mn2O3 thin films for photoelectrochemical water splitting. New Journal of Chemistry, 2023. 47 (17): p. 8347-8354. Naeem, R., et al., Photoelectrochemical properties of morphology controlled manganese, iron, nickel and copper oxides nanoball thin films deposited by electric field directed aerosol assisted chemical vapour deposition. Materials Today Communications, 2015. 4 : p. 141-148. Fouda, A., et al., Optimization of green biosynthesized visible light active CuO/ZnO nano-photocatalysts for the degradation of organic methylene blue dye. Heliyon, 2020. 6 (9). Naeem, R., et al., Optical and optoelectronic properties of morphology and structure controlled ZnO, CdO and PbO thin films deposited by electric field directed aerosol assisted CVD. Journal of Materials Science: Materials in Electronics, 2017. 28 (1): p. 868-877. Ehsan, M.A., et al., Fabrication of photoactive CaTiO3–TiO2 composite thin film electrodes via facile single step aerosol assisted chemical vapor deposition route. Journal of Materials Science: Materials in Electronics, 2019. 30 (2): p. 1411-1424. Bassi, A., et al., CuO Nanorods Immobilized Agar-Alginate Biopolymer: A Green Functional Material for Photocatalytic Degradation of Amaranth Dye. Polymers, 2023. 15 (3): p. 553. Chan, Y.B., et al., Effect of Calcination Temperature on Structural, Morphological and Optical Properties of Copper Oxide Nanostructures Derived from Garcinia mangostana L. Leaf Extract. Nanomaterials, 2022. 12 (20): p. 3589. Halfadji, A., et al., Effective investigation of electro-catalytic, photocatalytic, and antimicrobial properties of porous CuO nanoparticles green synthesized using leaves of Cupressocyparis leylandii. Journal of Molecular Structure, 2024. 1301 : p. 137318. Shabbir, S., et al., Optoelectronic and Photocatalytic investigations of chitosan (CS) modified Platinum decorated ceria (Pt-CeO2-CS) composite. Optical Materials, 2024. 157 : p. 116376. Hisham, F., et al., Biopolymer chitosan: Potential sources, extraction methods, and emerging applications. Ain Shams Engineering Journal, 2024. 15 (2): p. 102424. Haldorai, Y. and J.-J. Shim, Multifunctional chitosan‐copper oxide hybrid material: Photocatalytic and antibacterial activities. International Journal of Photoenergy, 2013. 2013 (1): p. 245646. Umoren, P.S., et al., Biogenic Synthesis and Characterization of Chitosan-CuO Nanocomposite and Evaluation of Antibacterial Activity against Gram-Positive and -Negative Bacteria. Polymers, 2022. 14 (9): p. 1832. Wahid, F., et al., Preparation, characterization and antibacterial applications of carboxymethyl chitosan/CuO nanocomposite hydrogels. International journal of biological macromolecules, 2017. 101 : p. 690-695. Dulta, K., et al., Multifunctional CuO nanoparticles with enhanced photocatalytic dye degradation and antibacterial activity. Sustainable Environment Research, 2022. 32 (1): p. 2. Naeem, R., et al., Single step aerosol assisted chemical vapor deposition of p–n Sn(ii) oxide–Ti(iv) oxide nanocomposite thin film electrodes for investigation of photoelectrochemical properties. New Journal of Chemistry, 2018. 42 (7): p. 5256-5266. Naeem, R., et al., Versatile Fabrication of Binary Composite SnO 2-Mn 2 O 3 Thin Films by AACVD for Synergistic Photocatalytic Effect. Journal of Electronic Materials, 2021. 50 : p. 3897-3906. Ehsan, M.A., et al., Fabrication of CoTiO3–TiO2 composite films from a heterobimetallic single source precursor for electrochemical sensing of dopamine. Dalton Transactions, 2016. 45 (25): p. 10222-10232. Sherino, B., et al., An Efficient Electrochemical Sensing of Hydrogen Peroxide on Zn-Based Coordination Polymer Decorated Carbon Paste Electrode. Journal of The Electrochemical Society, 2024. 171 (8): p. 087516. Marriam, F., et al., Synergistic approach of TiO2@ MnZnO3 heterostructure for efficient photoelectrochemical water splitting. Journal of The Electrochemical Society, 2024. 171 (9): p. 096501. El-Atawy, M.A., K.D. Khalil, and A.H. Bashal, Chitosan capped copper oxide nanocomposite: Efficient, recyclable, heterogeneous base catalyst for synthesis of nitroolefins. Catalysts, 2022. 12 (9): p. 964. Paul, S., D. M.K, and S. Peter, Development of Green Synthesized Chitosan-coated Copper Oxide Nanocomposite Gel for Topical Delivery. Journal of Pharmaceutical Innovation, 2023. 18 (3): p. 1010-1019. Dulta, K., et al., Multifunctional CuO nanoparticles with enhanced photocatalytic dye degradation and antibacterial activity. Sustainable Environment Research, 2022. 32 (1): p. 2. Jillani, S., et al., Synthesis, characterization and biological studies of copper oxide nanostructures. Materials Research Express, 2018. 5 (4): p. 045006. Sathiyavimal, S., et al., Eco-biocompatibility of chitosan coated biosynthesized copper oxide nanocomposite for enhanced industrial (Azo) dye removal from aqueous solution and antibacterial properties. Carbohydrate Polymers, 2020. 241 : p. 116243. Naeem, R., et al., The photoelectrochemically enhanced oxygen evolution reaction via thin films of novel (1:2:1) SnO-Mn2O3-TiO2 hybrid nanotubes. Surfaces and Interfaces, 2024. 46 : p. 104034. Munawar, K., et al., Temperature-controlled deposition of NiO-ZnO composite thin films: optical and photoelectrochemical properties. Journal of Applied Electrochemistry, 2025. 55 (9): p. 2481-2496. Munawar, K., et al., Effect of deposition temperature on topography and electrochemical water oxidation of NiO thin films. Thin Solid Films, 2023. 782 : p. 140031. Naeem, R., et al., Fabrication of pristine Mn2O3 and Ag–Mn2O3 composite thin films by AACVD for photoelectrochemical water splitting. Dalton Transactions, 2016. 45 (38): p. 14928-14939. Scheme 1 Scheme 1 is available in the Supplementary Files section. Additional Declarations No competing interests reported. Supplementary Files SupportingInformation.docx floatimage1.png Graphical Abstract Scheme1.png Scheme 1:Synthesizes of CS-CuO nanocomposite (CCu1, CCu3, CCu5). Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-7982430","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":541908875,"identity":"5ff1e2e7-d72b-4e6a-b934-eef9d2a3c6d5","order_by":0,"name":"Laraib Bibi","email":"","orcid":"","institution":"Sardar Bahadur Khan Women's University","correspondingAuthor":false,"prefix":"","firstName":"Laraib","middleName":"","lastName":"Bibi","suffix":""},{"id":541908876,"identity":"2a3b2d12-fe6d-4f17-9c00-0629ff5b2285","order_by":1,"name":"Saba Afzal","email":"","orcid":"","institution":"Sardar Bahadur Khan Women's University","correspondingAuthor":false,"prefix":"","firstName":"Saba","middleName":"","lastName":"Afzal","suffix":""},{"id":541908879,"identity":"d4d7baa7-796d-4179-87af-f07cba769c0d","order_by":2,"name":"Madina .","email":"","orcid":"","institution":"Sardar Bahadur Khan Women's University","correspondingAuthor":false,"prefix":"","firstName":"Madina","middleName":"","lastName":".","suffix":""},{"id":541908880,"identity":"150cbfed-f7ee-445d-8b6e-e2de4f8540c3","order_by":3,"name":"Ishrat Fatima","email":"","orcid":"","institution":"Government College University, Lahore","correspondingAuthor":false,"prefix":"","firstName":"Ishrat","middleName":"","lastName":"Fatima","suffix":""},{"id":541908883,"identity":"383c8d64-289f-4647-9dcf-1a79d620e63d","order_by":4,"name":"Rabia Naeem","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA8UlEQVRIiWNgGAWjYFACHoYDEAYzlAZSjA3EaWFLIF4LjGFAnBbz9rMHD/zcYSfHL3bm84ufbQxyfDcS2B7OwKNF5kxewsHeM8nGkrNzt1n2tjEYS95IYDfcgEeLBEOOwQHeNubEDbdztxkztjEkbgDaIvkAnxb+NwYH/7bV1++/nfMMpKWesBaJHIPDvG2HEwykc5gfA7UkGIC04HWYxLuEw7Jtxw1n3E4zY+w5J2E488zDdkN83pfgzz388W1btTz/7OTHH36U2cjzHU8+9rAHjxZkwCYBCg5grLQRqQGYYj7A9BKtZRSMglEwCkYEAAArh1L5bAYnrgAAAABJRU5ErkJggg==","orcid":"","institution":"Government College University, Lahore","correspondingAuthor":true,"prefix":"","firstName":"Rabia","middleName":"","lastName":"Naeem","suffix":""},{"id":541908887,"identity":"95dcc5eb-332d-4feb-8771-d0bd2ff6f2df","order_by":5,"name":"Bibi Sherino","email":"","orcid":"","institution":"Sardar Bahadur Khan Women's University","correspondingAuthor":false,"prefix":"","firstName":"Bibi","middleName":"","lastName":"Sherino","suffix":""},{"id":541908888,"identity":"4dad6bf7-7d54-437f-ae84-28bcb355cc96","order_by":6,"name":"Huma Tareen","email":"","orcid":"","institution":"Sardar Bahadur Khan Women's University","correspondingAuthor":false,"prefix":"","firstName":"Huma","middleName":"","lastName":"Tareen","suffix":""}],"badges":[],"createdAt":"2025-10-29 17:38:23","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-7982430/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7982430/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":95838341,"identity":"075c434b-c445-4b0e-ab00-48ba383fa5b7","added_by":"auto","created_at":"2025-11-13 13:49:27","extension":"docx","order_by":0,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":2566951,"visible":true,"origin":"","legend":"","description":"","filename":"CuOchitosanmanuscript29thoct2025.docx","url":"https://assets-eu.researchsquare.com/files/rs-7982430/v1/8ef03c192139e11439ebbdac.docx"},{"id":95838320,"identity":"e13403ce-b530-488f-8c9f-cbadfe84fc18","added_by":"auto","created_at":"2025-11-13 13:49:27","extension":"json","order_by":1,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":8581,"visible":true,"origin":"","legend":"","description":"","filename":"5d9b312e3f754a289751a431b9713ce6.json","url":"https://assets-eu.researchsquare.com/files/rs-7982430/v1/583d83defb6a342219b23244.json"},{"id":96240394,"identity":"2d1789be-d5fc-49b0-bba0-3acc60a5bcab","added_by":"auto","created_at":"2025-11-19 07:08:53","extension":"docx","order_by":2,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":309951,"visible":true,"origin":"","legend":"","description":"","filename":"SupportingInformation.docx","url":"https://assets-eu.researchsquare.com/files/rs-7982430/v1/c0c1c2120afa15e004ab8db4.docx"},{"id":96240392,"identity":"266b1b58-0f9d-4d75-bcbf-9062adac5539","added_by":"auto","created_at":"2025-11-19 07:08:52","extension":"xml","order_by":3,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":99900,"visible":true,"origin":"","legend":"","description":"","filename":"5d9b312e3f754a289751a431b9713ce61enriched.xml","url":"https://assets-eu.researchsquare.com/files/rs-7982430/v1/932e0548b121e791d9a737db.xml"},{"id":96240052,"identity":"dbe109db-7dd5-494f-90cc-24864226f6ac","added_by":"auto","created_at":"2025-11-19 07:08:18","extension":"png","order_by":5,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":121876,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage10.png","url":"https://assets-eu.researchsquare.com/files/rs-7982430/v1/5f0d980d384ceac61b5f948d.png"},{"id":96240204,"identity":"25bd8215-c550-4ab6-a2da-6e591a4ec476","added_by":"auto","created_at":"2025-11-19 07:08:33","extension":"png","order_by":6,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":24222,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage11.png","url":"https://assets-eu.researchsquare.com/files/rs-7982430/v1/eb212309b47e9e316a9b05e0.png"},{"id":95838336,"identity":"000a1df7-9e94-4402-b733-8b3afb2c9ea5","added_by":"auto","created_at":"2025-11-13 13:49:27","extension":"png","order_by":7,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":29731,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage12.png","url":"https://assets-eu.researchsquare.com/files/rs-7982430/v1/3c0d0376037873e501468cc5.png"},{"id":95838333,"identity":"b6e4a6aa-70f4-4414-a495-8d50e863e220","added_by":"auto","created_at":"2025-11-13 13:49:27","extension":"png","order_by":8,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":34195,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage13.png","url":"https://assets-eu.researchsquare.com/files/rs-7982430/v1/863cb0601218fdecada23aba.png"},{"id":96240101,"identity":"d259aa9b-b337-427c-b045-04525c10032a","added_by":"auto","created_at":"2025-11-19 07:08:24","extension":"png","order_by":9,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":246654,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-7982430/v1/3631f00b91a6151c01b826bb.png"},{"id":96241308,"identity":"c0a3bc78-61f3-4229-bc36-80b611f22ad0","added_by":"auto","created_at":"2025-11-19 07:10:33","extension":"png","order_by":10,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":75367,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-7982430/v1/166a86243801bc89fb3cec93.png"},{"id":95838351,"identity":"d6cbb0d8-9ae3-4c52-a6bf-5337403653e7","added_by":"auto","created_at":"2025-11-13 13:49:28","extension":"png","order_by":11,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":118298,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-7982430/v1/02d09603d9a1b09506af6531.png"},{"id":95838348,"identity":"d5f5d6d0-a3ad-47d2-9de7-59f9a17ef1ac","added_by":"auto","created_at":"2025-11-13 13:49:28","extension":"png","order_by":12,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":601903,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-7982430/v1/9925c3428d85b32428618d34.png"},{"id":95838346,"identity":"b7643d0e-a9bf-4018-9b9b-6393348d9186","added_by":"auto","created_at":"2025-11-13 13:49:28","extension":"jpeg","order_by":13,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":625460,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage6.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-7982430/v1/72c9a9ebab49e650af5166f8.jpeg"},{"id":96240097,"identity":"89c69761-fa82-4081-a656-a49c4d4a42b5","added_by":"auto","created_at":"2025-11-19 07:08:24","extension":"png","order_by":14,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":53548,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage7.png","url":"https://assets-eu.researchsquare.com/files/rs-7982430/v1/4425fd736b4554cb5af20d1f.png"},{"id":95838352,"identity":"f7e3fc03-6cb8-4c3a-a766-1405343d2522","added_by":"auto","created_at":"2025-11-13 13:49:28","extension":"jpeg","order_by":15,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":451042,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage8.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-7982430/v1/ea5d63244d8d5b98afd58b5b.jpeg"},{"id":95838343,"identity":"138dc436-fc7b-4dc5-b8a3-4178862e169e","added_by":"auto","created_at":"2025-11-13 13:49:28","extension":"png","order_by":16,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":120901,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage9.png","url":"https://assets-eu.researchsquare.com/files/rs-7982430/v1/756cea8f5f1f462eba17dd5b.png"},{"id":96239981,"identity":"73a99e0f-05a6-44e2-b0f7-4e28bbe632ed","added_by":"auto","created_at":"2025-11-19 07:08:05","extension":"png","order_by":17,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":44535,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-7982430/v1/6e00a223600e0616603071d0.png"},{"id":96239968,"identity":"b81b2371-c4c7-4a10-b077-bd45e89eebb0","added_by":"auto","created_at":"2025-11-19 07:08:04","extension":"png","order_by":18,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":20903,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage10.png","url":"https://assets-eu.researchsquare.com/files/rs-7982430/v1/d903bed70458df0c8f1d93eb.png"},{"id":95838356,"identity":"c107ca2e-b0a8-4d0b-980c-e126e89e6153","added_by":"auto","created_at":"2025-11-13 13:49:28","extension":"png","order_by":19,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":9593,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage11.png","url":"https://assets-eu.researchsquare.com/files/rs-7982430/v1/8d018f10ebc32d79c40b16b7.png"},{"id":96241072,"identity":"fbc0bea4-3420-44be-aa3f-2d4d6797861c","added_by":"auto","created_at":"2025-11-19 07:10:00","extension":"png","order_by":20,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":12337,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage12.png","url":"https://assets-eu.researchsquare.com/files/rs-7982430/v1/a2c3a57aad8cd6c4fc1ec5de.png"},{"id":96239792,"identity":"44bb3ac3-53de-4332-9b6d-02a9f92bb7d1","added_by":"auto","created_at":"2025-11-19 07:07:42","extension":"png","order_by":21,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":14880,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage13.png","url":"https://assets-eu.researchsquare.com/files/rs-7982430/v1/1a5db8afaeac7d77cb43d056.png"},{"id":95838353,"identity":"e6b703cd-edf0-49d5-a88f-7b9acc490367","added_by":"auto","created_at":"2025-11-13 13:49:28","extension":"png","order_by":22,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":42035,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-7982430/v1/b0c26b2484c65767d052fee3.png"},{"id":95838358,"identity":"3464b8aa-3e9a-49c9-b3db-7ac7ff0f5384","added_by":"auto","created_at":"2025-11-13 13:49:28","extension":"png","order_by":23,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":20102,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-7982430/v1/c45be761fedd0332503c47ac.png"},{"id":96241117,"identity":"fec1d3f3-403c-4577-a958-49af76bdbb06","added_by":"auto","created_at":"2025-11-19 07:10:15","extension":"png","order_by":24,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":24674,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-7982430/v1/d124159c968bfa09c704c389.png"},{"id":96240393,"identity":"1343b8c5-472a-4c48-854f-0d545e038a78","added_by":"auto","created_at":"2025-11-19 07:08:52","extension":"png","order_by":25,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":128693,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-7982430/v1/f6e2e4ef51605e7457fe2e14.png"},{"id":96239888,"identity":"8bbb030f-66c9-4496-8974-b9897c3fc776","added_by":"auto","created_at":"2025-11-19 07:07:53","extension":"png","order_by":26,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":58867,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage6.png","url":"https://assets-eu.researchsquare.com/files/rs-7982430/v1/0aada224b76c4113a368fd20.png"},{"id":95838354,"identity":"2310c41f-0d08-44b1-b755-21c1dc08d7c8","added_by":"auto","created_at":"2025-11-13 13:49:28","extension":"png","order_by":27,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":11404,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage7.png","url":"https://assets-eu.researchsquare.com/files/rs-7982430/v1/4277c4c9b5d6509bfa6d3280.png"},{"id":95838360,"identity":"22633a30-f8c6-4fa1-aa28-583dd824022c","added_by":"auto","created_at":"2025-11-13 13:49:28","extension":"png","order_by":28,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":105341,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage8.png","url":"https://assets-eu.researchsquare.com/files/rs-7982430/v1/2887e35e7c0f501e1e0835f9.png"},{"id":95838355,"identity":"e4b78853-8376-4e1d-acb6-3ab23bdba670","added_by":"auto","created_at":"2025-11-13 13:49:28","extension":"png","order_by":29,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":26458,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage9.png","url":"https://assets-eu.researchsquare.com/files/rs-7982430/v1/b7f7a193b193a3a0ebc9289d.png"},{"id":96240142,"identity":"95b723f0-9b0c-4bca-bcda-a1c05c478b95","added_by":"auto","created_at":"2025-11-19 07:08:29","extension":"xml","order_by":30,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":96231,"visible":true,"origin":"","legend":"","description":"","filename":"5d9b312e3f754a289751a431b9713ce61structuring.xml","url":"https://assets-eu.researchsquare.com/files/rs-7982430/v1/d7bb6ec0ea59c56beffc1e2a.xml"},{"id":96239923,"identity":"ee4804ae-72d7-4692-b149-3918b50337d6","added_by":"auto","created_at":"2025-11-19 07:07:58","extension":"html","order_by":31,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":107990,"visible":true,"origin":"","legend":"","description":"","filename":"earlyproof.html","url":"https://assets-eu.researchsquare.com/files/rs-7982430/v1/d34d6d24aef3385e5a071b51.html"},{"id":95838319,"identity":"36c7b127-0eaa-4323-9dd2-f0bdd2955bc9","added_by":"auto","created_at":"2025-11-13 13:49:27","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":75367,"visible":true,"origin":"","legend":"\u003cp\u003eXRD diffraction patterns of CuO- CS nanocomposites\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-7982430/v1/d84f04a6341341a25cb6ad7c.png"},{"id":96240036,"identity":"a18aa057-e050-4223-9e0e-d42d360d7cfc","added_by":"auto","created_at":"2025-11-19 07:08:17","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":118298,"visible":true,"origin":"","legend":"\u003cp\u003eFTIR spectra of CS-CuO nanocomposites (CCu5, CCu3, CCu1)\u003c/p\u003e","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-7982430/v1/7491a2032719aa3032f7d9db.png"},{"id":96240183,"identity":"36896fe3-772b-4c40-99e3-e0ae1efe9253","added_by":"auto","created_at":"2025-11-19 07:08:32","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":601903,"visible":true,"origin":"","legend":"\u003cp\u003eSEM images of CuO NPs at room temperature \u003cstrong\u003e(a, b, c) \u003c/strong\u003eSEM images of (a) CCu1 (b) CCu3 (c) CCu5 (CS-CuO) nanocomposite.\u003c/p\u003e","description":"","filename":"floatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-7982430/v1/2202f9b8a6f086faf9a506e0.png"},{"id":96240179,"identity":"089f8f6c-ff09-448c-9945-b7de1aa154c4","added_by":"auto","created_at":"2025-11-19 07:08:32","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":249041,"visible":true,"origin":"","legend":"\u003cp\u003eEDX spectra of pure CuO NPs at room temperature \u003cstrong\u003e(a, b, c) \u003c/strong\u003espectra of nanocomposite (a) CCu1 (b) CCu3 (c) CCu5.\u003c/p\u003e","description":"","filename":"floatimage6.png","url":"https://assets-eu.researchsquare.com/files/rs-7982430/v1/6435da7feaa063616c6282ce.png"},{"id":95838322,"identity":"7f944dde-2b45-4db6-b10a-1f897dd533f0","added_by":"auto","created_at":"2025-11-13 13:49:27","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":53548,"visible":true,"origin":"","legend":"\u003cp\u003eUV-Visible spectra of (CCu1 CCu3 and CCu5) CuO-CS nanocomposite.\u003c/p\u003e","description":"","filename":"floatimage7.png","url":"https://assets-eu.researchsquare.com/files/rs-7982430/v1/200f9a9b0bb5e64a42937952.png"},{"id":96240342,"identity":"40e539ac-39b5-48f9-aae8-d7e7067e67c1","added_by":"auto","created_at":"2025-11-19 07:08:50","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":375179,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003e(a) \u003c/strong\u003eTauc Plot of CuO NPs \u003cstrong\u003e(b) \u003c/strong\u003espectra of (CCu1 CCu3 and CCu5) CuO-CS nanocomposite.\u003c/p\u003e","description":"","filename":"floatimage8.png","url":"https://assets-eu.researchsquare.com/files/rs-7982430/v1/bc8a583d7e3f129e0981a904.png"},{"id":96240811,"identity":"523db7e5-4cbb-4676-8083-b3f6b901b084","added_by":"auto","created_at":"2025-11-19 07:09:36","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":120901,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003e(a).\u003c/strong\u003e%age adsorption of MB by CuO NPS and CS-CuO nanocomposites \u003cstrong\u003e(b) \u003c/strong\u003e%age decolorization of CuO NPs and CS-CuO nanocomposites\u003c/p\u003e","description":"","filename":"floatimage9.png","url":"https://assets-eu.researchsquare.com/files/rs-7982430/v1/7270c35acdef24ee8df26b4d.png"},{"id":96240717,"identity":"9c86e71c-53ff-4203-a98a-585b1f0c408e","added_by":"auto","created_at":"2025-11-19 07:09:25","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":121876,"visible":true,"origin":"","legend":"\u003cp\u003ePlausible Mechanism of degradation of MB.\u003c/p\u003e","description":"","filename":"floatimage10.png","url":"https://assets-eu.researchsquare.com/files/rs-7982430/v1/73937a33d963c103d7470b72.png"},{"id":95838340,"identity":"74a34f25-7039-4ebe-8c65-3fd1651395a0","added_by":"auto","created_at":"2025-11-13 13:49:27","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":24222,"visible":true,"origin":"","legend":"\u003cp\u003eCurrent–voltage (I–V) curve of CuC1, CuC3, CuC5 and CuO photoelectrodes in 0.5 M KOH at a scan rate of 20 mV/s in presence and absence of light.\u003c/p\u003e","description":"","filename":"floatimage11.png","url":"https://assets-eu.researchsquare.com/files/rs-7982430/v1/7f055ce7ba15d4ee92127087.png"},{"id":95838326,"identity":"e15cac6c-3e25-4e0b-8f1f-3f00d6cf0fd6","added_by":"auto","created_at":"2025-11-13 13:49:27","extension":"png","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":29731,"visible":true,"origin":"","legend":"\u003cp\u003eNyquist plot of electrochemical spectroscopy (EIS) investigations recorded at frequencies of 0.01 Hz to 10 KHz under light illumination for CuC1, CuC3, CuC5 and CuO photoelectrode\u003c/p\u003e","description":"","filename":"floatimage12.png","url":"https://assets-eu.researchsquare.com/files/rs-7982430/v1/07b0d59f34056a656635defc.png"},{"id":96240328,"identity":"4a9da05a-52da-4dd8-a92b-663ddd66328a","added_by":"auto","created_at":"2025-11-19 07:08:49","extension":"png","order_by":11,"title":"Figure 11","display":"","copyAsset":false,"role":"figure","size":34195,"visible":true,"origin":"","legend":"\u003cp\u003eMott–Schottky (MS) plots CuO and CuO-Chitosan composites at a frequency of 1 kHz in 0.5 M KOH.\u003c/p\u003e","description":"","filename":"floatimage13.png","url":"https://assets-eu.researchsquare.com/files/rs-7982430/v1/158ac6e827fcf072448cdbee.png"},{"id":96362693,"identity":"a118bf9d-c55d-45cc-9f71-64c20d7da69f","added_by":"auto","created_at":"2025-11-20 09:43:59","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2680261,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7982430/v1/8b03d67d-10a2-46e3-8d46-59a2b182472f.pdf"},{"id":96240105,"identity":"97beca10-e64c-4822-9bc7-58818684081f","added_by":"auto","created_at":"2025-11-19 07:08:24","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":309951,"visible":true,"origin":"","legend":"","description":"","filename":"SupportingInformation.docx","url":"https://assets-eu.researchsquare.com/files/rs-7982430/v1/a9c0732ad47dfc0f3b9795c9.docx"},{"id":96241295,"identity":"5b9613ef-06bd-480b-9dcd-bdabef6ca8d6","added_by":"auto","created_at":"2025-11-19 07:10:33","extension":"png","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":256440,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eGraphical Abstract\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-7982430/v1/c1cc539d7105716e486cc877.png"},{"id":95838323,"identity":"43d45751-7627-4832-bc0e-b1b42eacac2a","added_by":"auto","created_at":"2025-11-13 13:49:27","extension":"png","order_by":3,"title":"","display":"","copyAsset":false,"role":"supplement","size":246654,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eScheme 1:\u003c/strong\u003eSynthesizes of CS-CuO nanocomposite (CCu1, CCu3, CCu5).\u003c/p\u003e","description":"","filename":"Scheme1.png","url":"https://assets-eu.researchsquare.com/files/rs-7982430/v1/9da448139e2bf542919a6307.png"}],"financialInterests":"No competing interests reported.","formattedTitle":"Effect of Chitosan loading towards structural, optoelectronic and photocatalytic degradation of flakes like CuO-Chitosan nanocomposite","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eThe growing global energy demand and rapid depletion of fossil fuels have strengthened the search for clean, renewable, and sustainable energy sources[\u003cspan additionalcitationids=\"CR2 CR3 CR4\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e].The rapid progress of the socio-economy and chemical industry give rise to in the release of huge amount of wastewater comprising antibiotics and dyes into water bodies, leading to water pollution[\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. This poses a risk to ecology, human health, and the environment, creation of problem that involves consideration[\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. With the passage of time, numerous techniques for the elimination of poisonous components in wastewater have sustained to be developed, such as membrane separation, adsorption, and photocatalytic technology. Amongst these methods, semiconductor photocatalysis had developed as one of the most vital and auspicious technique due to its easy handling, better reproducibility, simplicity, cost-effective performance, and environment benign [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. Previous literature had studied various semiconductors as effective photocatalysts, such as Mn\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e[\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e], CdO, ZnO[\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e], TiO\u003csub\u003e2\u003c/sub\u003e, SnO\u003csub\u003e2\u003c/sub\u003e, CuO, Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e and CoTiO\u003csub\u003e3\u003c/sub\u003e[\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. Amongst various semiconductor metal oxide materials, like CuO nanostructure has attracted important attention due to its high reactivity, narrow band gap with monoclinic crystal structure and their large surface volume displays notable applications in catalysis[\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e, \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. The morphology of CuO NPs rely on numerous factors such as electrolyte concentration, reaction temperature, pH, precursor concentration, and kind of capping agent. A small alteration in reaction parameters can affect the physiochemical properties of CuO NPs. Similarly, the photocatalytic performance of CuO NPs depend upon their charge separation and agglomeration of NPs during photodegradation process. To avoid the agglomeration of NPs and maintain better charge separation the functionalization of NPs by a biopolymer can be taken into consideration[\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eCS is a natural polymer that is biodegradable, nontoxic, low-cost and environmentally safe [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. CS has also durable affinity toward metal ions due to the presence of very reactive NH\u003csub\u003e2\u003c/sub\u003e and OH groups in its structure, and therefore leading to CS-CuO nanocomposite more active which enhances its adsorption and attractive effects towards treatment of organic pollutants[\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e, \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. Furthermore, CS proficiently improve the lifetime of photogenerated electrons of CuO, tuning the characteristics of charge separation, later enlightening the photocatalytic activities[\u003cspan additionalcitationids=\"CR19\" citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eCombination of transition metal-oxide semiconductors with biopolymers such as chitosan (CS) produces hybrid composite materials that can link the necessities of optical properties, charge transfer, and surface functionality. Transition Metal oxides like SnO\u003csub\u003e2\u003c/sub\u003e. [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]TiO₂, ZnO, CuO,[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e] and numerous doped metal oxides offer necessary electronic band positions and strong light absorption while CS play a role of film making capability, abundant surface functional groups (\u0026ndash;NH₂, \u0026ndash;OH) and tunable adsorption features [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. This interaction is beneficial for optoelectronic devices where interfacial charge transport, surface morphology and ideal energy gap, are important in photodetectors, Photoelectrochemical (PEC) electrodes, photovoltaics, and sensors[\u003cspan additionalcitationids=\"CR24\" citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]. Studies regarding ZnO\u0026ndash;CS, CuO\u0026ndash;CS and TiO₂\u0026ndash;CS [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e] nanocomposites reported that reasonable transition metal oxide loading as photoelectrodes (e.g., CuO\u0026ndash;CS) [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e], can modify surface topography under PEC conditions and improve charge separation at the electrode\u0026ndash;electrolyte interface. Most of the literature display enhanced photocurrent stability and retard photo corrosion when CS play a role of passivating and hydrophilic interlayer. Previous literature illustrates that CS increases photocatalytic elimination of dyes and pollutants when mutual with TiO₂, ZnO or other metal oxides, improves adsorption of pollutants, reduced charge recombination, and enabled reactive species production[\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eThe present study emphases on the synthesis of CuO NPs are at 30\u0026deg;C, 60\u0026deg;C and 80\u0026deg;C. The CuO prepared at 80\u0026deg;C are considered optimum and these optimize NPs are utilized for coating by CS at various concentrations. The impact of chitosan loading on the physiochemical, optical and photoelectrocatalytic properties of nanocomposite samples is assessed. The phoyodegradation efficacy of CuO-CS nanocomposite is evaluated by using Methylene blue dye (MB). The twining of CuO with CS expected to improve charge separation, increase adsorption of pollutant on catalyst surface, suppress catalyst agglomeration and hence elevate overall photodegradation and optoelectronic performance.\u003c/p\u003e"},{"header":"2. Materials and Method","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003e2.1. Materials\u003c/h2\u003e\u003cp\u003eCopper acetate monohydrate (Cu(C\u003csub\u003e2\u003c/sub\u003eH\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e.H\u003csub\u003e2\u003c/sub\u003eO (99.5%), Sodium hydroxide (NaOH) (99.8%), CS biopolymer (medium, molecular weight, 75\u0026ndash;85% deacetylated) and Glacial acetic acid (CH\u003csub\u003e3\u003c/sub\u003eCOOH) (100%) were purchased from Sigma Aldrich. Ethanol (99.8%) was purchased from RCI Lab scan, Thailand and MB dye was purchased from MERCK, Germany. Distilled water was used as a solvent throughout the experiment and all the chemicals are used without further purification.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\u003ch2\u003e2.2. Synthesis of CuO NPs by Co-precipitation method\u003c/h2\u003e\u003cp\u003eCuO NPs are synthesized by a straightforward co-precipitation process at room temperature (30\u0026deg;C). 0.02 M solution of Cu(C\u003csub\u003e2\u003c/sub\u003eH\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e.H\u003csub\u003e2\u003c/sub\u003eO is prepared in 300 ml of distilled water. The solution is stirred with a magnetic bar for about 15 to 20 minutes at room temperature with 1 mL of CH\u003csub\u003e3\u003c/sub\u003eCOOH. An aqueous solution of 1 M NaOH is prepared which acts as a reducing agent. The solution is added to the mixture dropwise until the pH is adjusted around 9 and 11. The NaOH solution gives OH groups that react with copper salt to produce copper hydroxide Cu(OH)\u003csub\u003e2\u003c/sub\u003e. The pH adjustment changes the solution's color from blue to black. After an hour remove the product from stirring and then washed with ethanol and water to purify the sample. Moreover, dry the sample at 60\u0026deg;C for approximately 5\u0026ndash;6 hours to produce the final product. Two more samples of CuO are prepared at 60\u0026deg;C and 80\u0026deg;C using the same method to determine the optimum synthesis temperature for CuO NPs as represented in Figure \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\u003ch2\u003e2.3. Synthesizes of CuO-CS nanocomposite.\u003c/h2\u003e\u003cp\u003eFirstly, the solution of CS is prepared at three different concentrations (0.1, 0.3, and 0.5 g) in 100 ml of 2% (v/v) acetic acid. Secondly, the as prepared CuO NPs (0.5 g) dissolve 250 ml of double-distilled water in a round-bottom flask and sonicate the mixture for approximately half an hour. Now add the solution of CuO NPs to the CS solution (0.1 g) and stir for approximately 45 minutes. The pH of this solution is adjusted to 10\u0026ndash;11 by adding 1M of NaOH. The mixture is heated over water bath at 80\u0026deg;C for about 2 hours to get a homogeneous product. The product is then centrifuged at 8000 rpm, washed with excess ethanol and distilled water and dried in an oven at 60\u0026deg;C. the product is labeled as CCu1 in scheme \u003cspan refid=\"Sch1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. The same procedure is used to prepare CuO-CS nanocomposites with other CS concentrations (0.3 and 0.5 g) and the products are labeled as CCu3 and CCu5 respectively.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e\u003ch2\u003e2.4. Characterization techniques\u003c/h2\u003e\u003cp\u003eThe surface morphology of NPs and nanocomposites was determined by SEM. The chemical nature or elemental composition of materials was analyzed by EDX analysis, JSM-IT800. Additionally, the crystal phase, size and crystallinity are determined through XRD (Bruker D2 PHASER XR, 2nd Generation) at 2 theta value between 20\u0026ndash;80\u0026deg; range. Functional group identification and chemical bonding within the molecules is carried out by FTIR spectrophotometer (ALPHA-E) in the range of 500\u0026ndash;4000 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. UV-Vis (Shimadzo-1800 UV) is used to assess the photodegradation process and and identification of compounds within the wavelength ranging from 300\u0026ndash;800 nm.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e\u003ch2\u003e2.5. Photocatalytic activity\u003c/h2\u003e\u003cp\u003eMB dye is used as a model pollutant to examine the photocatalytic activity of all nanocomposite samples and pure CuO NPs. The photocatalytic process is carried out in a reactor equipped with 200 W halogen lamp as a source of visible light. At first 20 ppm solution of MB dye is prepared in 1 L of distilled water. A 0.30 g of pure CuO NPs are added into 100 ml to as prepared dye solution. The adsorption-desorption equilibrium was determined by stirring the solution in the dark for approximately half an hour before exposing it to visible light. The dye solution is then placed under a halogen bulb with continuous stirring, and a 5 mL sample of dye is taken off every 30 min and analyzed by UV-Vis spectrophotometer at around λmax\u0026thinsp;=\u0026thinsp;664 nm. The whole photodegradation process is conducted at room temperature at time interval of ranging from 0 to 150 min. The same process is applied to all nanocomposite samples to assess and compare the adsorption-photodegradation.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\u003ch2\u003e2.6 Optoelectronic measurements\u003c/h2\u003e\u003cp\u003eOptoelectronic measurements were conducted in a conventional three-electrode workstation, with a saturated-potassium-chloride, silver/silver chloride electrode (Ag/AgCl-3M KCl) as a reference electrode and a platinum wire as a counter electrode. The CuO, CuC1, CuC3 and CuC3 electrodes used as the working electrodes on FTO substrate by drop casting method. The electrolyte was composed of 0.5M KOH solution. Linear scan voltammetry (LSV) was evaluated by a Princeton Applied Research PAR-VersaSTAT-3 electrochemical workstation. The potential window of -300 mV to +\u0026thinsp;1000 mV vs. Ag/AgCl at a scan rate of 20 mV s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. The charge transfer resistance and lifetime of photo-generated charge carriers was calculated by Nyquist and Bode phase. A 150 W UV lamp with power density of 100 mW.cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e was employed as a source of light.\u003c/p\u003e\u003c/div\u003e"},{"header":"3. Results and Discussion","content":"\u003cdiv id=\"Sec10\" class=\"Section2\"\u003e\u003ch2\u003e3.1 Structural studies\u003c/h2\u003e\u003cp\u003eXRD analysis is used to determine the crystal phase, chemical nature, grain size, and degree of crystallinity of CuO NPs and composite samples, X-ray diffraction spectra were taken by using XRD (Bruker D2 PHASER XR, 2nd Generation) at 2θ value between 20\u0026ndash;80\u0026deg; range. In the Figure S2 prominent peaks corresponding to the (hkl) values of (110), (111), (202), (020), (202), (113), (311), and (004) respectively, which are the characteristics peaks of CuO NPs. All these peaks showed that CuO NPs are successfully synthesized in mild experimental conditions and match with literature data[\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. The diffraction peaks were identified as the monoclinic phase of CuO NPs. Using the Scherrer equation (D\u0026thinsp;=\u0026thinsp;K λ / Β COS θ), the average crystallite size of CuO NPs was calculated (Table\u0026nbsp;1). This indicated that by increasing synthesis temperature, high intensity and narrower diffraction peaks are obtained which corresponds to the smaller crystal size. The estimated crystallite or grain size for pristine CuO NPs and CuO-Chitosan composites are in nanometer range and decreases from 54nm (CuO 80 \u003csup\u003eo\u003c/sup\u003eC) to 20nm (CCu5) due to increasing content of Chitosan as illustrated in Table\u0026nbsp;1. Figure\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e1\u003c/span\u003e indicates the XRD spectra of composite samples prepared on varying CS concentrations. As CS is semi-crystalline, therefore by compositing it with Cu metal the results in broader and less intense diffraction peaks. Therefore, by increasing CS concentration peaks became broader and less intense from CCu1 to CCu5 that confirms the interaction between Cu metal and CS [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]. It showed the intensity and position of diffraction peaks, which approve the existence of CuO in all the nanocomposites and the particles are of monoclinic crystal system in accordance with literature, (JCPDS, File No 01-080-1916). CuO exhibits the monoclinic CuO phase with reflections at about 2θ\u0026thinsp;=\u0026thinsp;32.2\u003csup\u003eo\u003c/sup\u003e, 35.05 \u003csup\u003eo\u003c/sup\u003e, 38.07 \u003csup\u003eo\u003c/sup\u003e, 48.1\u003csup\u003eo\u003c/sup\u003e, 52.8 \u003csup\u003eo\u003c/sup\u003e, 57.5 \u003csup\u003eo\u003c/sup\u003e, 61.1\u003csup\u003eo\u003c/sup\u003e, 65.5\u003csup\u003eo\u003c/sup\u003e, 67.6\u003csup\u003eo\u003c/sup\u003e, 72.02\u003csup\u003eo\u003c/sup\u003e, 74.7\u003csup\u003eo\u003c/sup\u003e with the lattice plan of (110), (-111), (111), (-202), (020), (202), (-113), (-311), (220), (311), and (004) respectively[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. Sharp well-defined peaks indicate the crystalline nature of the CuO. At temperature 30\u003csup\u003eo\u003c/sup\u003e (room temperature) peak at 16\u003csup\u003eo\u003c/sup\u003e-17\u003csup\u003eo\u003c/sup\u003e show the presence of Cu(OH)\u003csub\u003e2\u003c/sub\u003e at temperature 60\u003csup\u003eo\u003c/sup\u003e conversion of Cu(OH)\u003csub\u003e2\u003c/sub\u003e occur [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. At 80\u003csup\u003eo\u003c/sup\u003e temperature totally converted into monoclinic CuO. In the Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e1\u003c/span\u003ea CuO-CS nanocomposites with less intensities have observed. A broad amorphous hump at 2θ\u0026thinsp;=\u0026thinsp;18\u003csup\u003eo\u003c/sup\u003e-22\u003csup\u003eo\u003c/sup\u003e confirmed the formation of CuO-CS. Broad hump indicates the semi-crystalline nature of the chitosan. When CuO combine with chitosan, CuO peaks remain visible with low intensities. The CS concentration also impact on particle size which gradually decrease from CCu1 to CCu5. The decrease in particle size can be associated with better optoelectronic, adsorption and phodegradation performance towards dye molecule.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cb\u003eTable.1.\u003c/b\u003e Band gap and particle size of CuO NPs (30\u0026deg;C, 60\u0026deg;C and 80\u0026deg;C) and nanocomposites (CCu1, CCu3 and CCu5).\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Taba\" border=\"1\"\u003e\u003ccolgroup cols=\"4\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eCuO NPs (\u0026deg;C)/CS-CuO Nanocomposites\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eWavelength (nm)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eParticle Size (nm)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eBand gap (eV)\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e30\u0026deg;C\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e360\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e50 nm\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e3.44 eV\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e60\u0026deg;C\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e364\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e52 nm\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e3.40 eV\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e80\u0026deg;C\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e368\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e54 nm\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e3.36 eV\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eCCu1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e377\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e24 nm\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e3.34eV\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eCCu3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e380\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e22 nm\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e3.32 eV\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eCCu5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e384\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e20 nm\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e3.29eV\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eTwo prominent peaks at 34.6\u0026deg; and 37.7\u0026deg; are considered as backbone of nanocomposite that showed the interaction between CS and CuO NPs.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThe FTIR spectra of CuO NPs are presented in Fig S3. The vibrational bands of CuO NPs synthesized at various temperatures are observed in the range of 606cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e to 863cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e corresponding to the Cu-O bond, indicating the successful formation of metal oxide. The frequency band at 1112 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and 1104 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e shows the C\u0026thinsp;=\u0026thinsp;C stretching bond and the peaks that appeared at 1420 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and 1427 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e correspond to the C-O bonds, respectively. Peaks in the range of 2345\u0026ndash;2907cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e are due to C\u0026thinsp;=\u0026thinsp;O stretching. This peak is due to the use of organic reactants during CuO synthesis. These organic molecules typically contain carbonyl groups (C\u0026thinsp;=\u0026thinsp;O), and traces of these molecules can remain adsorbed on the surface NPs leading to the appearance of C\u0026thinsp;=\u0026thinsp;O stretching vibrations. The absorption peaks in the range of 3773\u0026ndash;3835 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e is due to the O-H stretching group of water molecules (Nithya et al., 2014). It is observed some of the IR bands (14000\u0026ndash;40000 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) decrease in intensity and by increasing temperature (80\u0026deg;C). Likewise, Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e2\u003c/span\u003e depicts the FTIR spectrum of composite samples which indicates the slight shifting and appearance of stretching mode of O-Cu-O in the ranges of 700\u0026ndash;839 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. This shifting to the higher wavenumber might be due to coating of CuO NPs with CS. The peaks at 1115\u0026thinsp;\u0026minus;\u0026thinsp;1110 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) are due to \u003cem\u003eβ\u003c/em\u003e (1\u0026ndash;4) glycosidic bond in polysaccharide units of CS. The IR band located at 1437\u0026thinsp;\u0026minus;\u0026thinsp;1424 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e corresponded to the OH group of CS. While the bands around 1601 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, 1566 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and 1552 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e are allocated to the NH\u003csub\u003e2\u003c/sub\u003e stretching of amide groups. The peaks observed around 2899\u0026ndash;2922 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e are responsible for CH\u003csub\u003e2\u003c/sub\u003e and CH\u003csub\u003e3\u003c/sub\u003e bands of CS chains. Furthermore, the peak at 3570\u0026ndash;3857 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e is due to the intermolecular H-bonding and NH\u003csub\u003e2\u003c/sub\u003e stretching bands. The peak intensity decreases gradually with slight shifting is due to increase in CS concentration that is an evidence for the coordination of CuO molecules with the CS functional groups (NH\u003csub\u003e2\u003c/sub\u003e, OH)[\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e].\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e\u003ch2\u003e3.2. Morphological studies\u003c/h2\u003e\u003cp\u003eSEM image of CuO NPs captured at a magnification of 1 um is presented in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e3\u003c/span\u003e. The surface morphology showed a thick, flakes-like structure might be due to the agglomeration of particles that form clusters at ambient temperature. According to SEM results, room temperature synthesis of CuO NPs is an appropriate condition for achieving homogeneity and uniform dispersion of CuO NPs. Similar outcomes have also been previously reported [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e3\u003c/span\u003e (a, b, c) shows that CCu nanocomposite samples displayed a thin flakes-like morphology, as CS biopolymer acts as a stabilizing agent and prevent particle agglomeration. This indicates that the CS polymer was dispersed uniformly on to the surface of CuO NPs. Elemental composition of CuO NPs is illustraed in the Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e4\u003c/span\u003e. The spectra exclusively showed copper (Cu) and oxygen (O) elements without additional elemental impurities confirming their purity. The most intense peak in (CuO NPs) spectra is of Cu, indicating a Cu rich composition in the metal NPs. The Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e4\u003c/span\u003e (a, b, c) shows the relative percentages of elements in composite samples. The spectra of CCu1 (a) contain C, O, and Cu components in the range of 21.09%, 22.49%, and 56.42% respectively. The elemental composition of C, O, Cu, and N in CCu3 is 11.61%, 24.15%, 67.11%, and 0.13%. Similarly, the EDX of CCu5 indicate C, O, Cu and N in the range of 11.41%, 19.82%, 67.02%, 1.74% respectively and no other impurities were detected.\u003c/p\u003e\u003cp\u003eAs CCu1 contained the least amount of CS therefore, no peak was observed for the N element, and only weak signals for oxygen, carbon, and copper were detected. Similarly, CCu5 is with highest CS concentration showed higher nitrogen signal. The developed structure of CuO NPs and the CS-CuO nanocomposite indicated that there are no additional impurities as evident from the elemental composition.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec12\" class=\"Section2\"\u003e\u003ch2\u003e3.3. Optical studies\u003c/h2\u003e\u003cp\u003eThe UV results of CuO NPs are displayed in Fig S4 which showed a maximum wavelength of CuO prepared at 30, 60 and 80\u0026deg;C at 360, 364, and 368 nm respectively[\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. This red shift by increasing temperature is a clear indication that the temperature has an impact on UV absorption peaks. The characteristic absorbance peaks of composite samples are presented in Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e5\u003c/span\u003e. The nanocomposite samples CCu1, CCu3, and CCu5 shows peaks at nanocomposite at the wavelength of 377, 380, and 384 nm respectively[\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e]. This indicates a red shift in UV absorption bands by increasing CS concentration.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThe Band gap energy of all the samples is calculated using Tauc equation as reported in the literature[\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e]:\u003c/p\u003e\u003cp\u003eAs shown in Table\u0026nbsp;1. The rise in temperature during the preparation of CuO NPs, an absorption peak shift to a larger wavelength thus reduces the band gap. It indicates that thermal energy can promote particle growth, often resulting in larger CuO NPs which shows that temperature influences the band gap. The optical band gap of nanocomposites displayed that the optical band gap energies reduce as the concentration of CS increases as mentioned in Table\u0026nbsp;1. This indicates that the red shift wavelength accredited to smaller crystallite size, enhances the composite surface area which in turn improves its efficacy toward the photodegradation of organic dyes\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec13\" class=\"Section2\"\u003e\u003ch2\u003e\u003cb\u003e3.6. Photocatalytic degradation of Methylene blue\u003c/b\u003e (\u003cb\u003eMB)\u003c/b\u003e\u003c/h2\u003e\u003cp\u003eThe photocatalytic performance of synthesized pure CuO NPs and all CuO-CS nanocomposites was examined by decoloring 20 mg/L of MB solutions. Adsorption of MB was performed under darkness to establish adsorption-desorption equilibrium between the catalysts and dye molecules. Figure\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e7\u003c/span\u003e (a) presented the rate of degradation under visible light exposure. In Fig.\u0026nbsp;\u003cspan refid=\"Fig11\" class=\"InternalRef\"\u003e8\u003c/span\u003e (b) Experiments were conducted and the rate of degradation with the presence catalyst reached about 62% respectively. The results show that the maximum adsorption is attained with CCu5 nanocomposite followed by CCu1 and CCu3. The quantity of protonated surface amino groups on the photocatalyst surface that interacted with the MB compounds was correlated with this adsorption pattern. Because the concentration of protonated surface amino groups was lower in CCu1 than in CCu3, MB adsorption was lower in those samples.\u003c/p\u003e\u003cp\u003eFurthermore, CCu5 degraded about 93% of the dye within 150 min, which is higher higher as compared to CCu3 and CCu1, due to the modification of catalyst surface by the interaction among CS which increases its active sites and effects the catalytic activity of CuO NPs against dye degradation[\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. Hence, CCu5 showed effective photocatalytic activities against MB dye as CS provides additional active sites for binding dye molecules. With a higher CS concentration, more dye molecules can interact. It is obvious that the concentration of dye declines with time by increasing the loading of CS [\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e].\u003c/p\u003e\u003cp\u003e% Degradation of dye was calculated by using equation:\u003c/p\u003e\u003cp\u003e\u003cb\u003eDegradation (%) = (1-(\u003c/b\u003e\u003cem\u003eC\u003c/em\u003e\u003csub\u003e\u003cb\u003e0\u003c/b\u003e\u003c/sub\u003e\u003cb\u003e/C\u003c/b\u003e\u003csub\u003e\u003cb\u003ee\u003c/b\u003e\u003c/sub\u003e\u003cb\u003e) \u0026times; 100\u003c/b\u003e\u003c/p\u003e\u003cp\u003eWhere \u003cb\u003eC\u003c/b\u003e\u003csub\u003e\u003cb\u003e0\u003c/b\u003e\u003c/sub\u003e corresponds to the initial concentration and \u003cb\u003eC\u003c/b\u003e\u003csub\u003e\u003cb\u003ee\u003c/b\u003e\u003c/sub\u003e is the final concentration of Methyl Blue dye. This equation displays the percentage of dye degradation.\u003c/p\u003e\u003cp\u003eBy considering all the characterization results the morphology, and crystalline structure of nanoparticles all play an important role in photocatalytic behavior. According to the report, the size and shape of NPs, the energy transfer process, as well as the production and consumption of photo-generated carriers, significantly influence the catalytic activity of nanocatalysts [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e].\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eMeanwhile, under visible light irradiation (Fig.\u0026nbsp;\u003cspan refid=\"Fig11\" class=\"InternalRef\"\u003e8\u003c/span\u003e), oxygen molecules absorbed on the surface of catalysts formed superoxide radicals (O\u003csub\u003e2\u003c/sub\u003e) radicals. These radicals react with a dye or other organic molecule, resulting in their conversion into harmless products, like H\u003csub\u003e2\u003c/sub\u003eO and CO\u003csub\u003e2\u003c/sub\u003e molecules[\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e].\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e"},{"header":"4. Optoelectronic properties:","content":"\u003cp\u003eThe optoelectronic studies of CuC1, CuC3, CuC5 and CuO photoelectrodes were deposited on FTO was performed using a standard 3-electrode electrochemical cell in 0.5 M KOH as an electrolyte solution[\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e]. The photocurrent was calculated in the presence of UV light. Figure\u0026nbsp;\u003cspan refid=\"Fig12\" class=\"InternalRef\"\u003e9\u003c/span\u003e describes that the linear scan voltammograms (LSV) of all four electrodes under dark and light conditions. On scanning the potential from \u0026minus;\u0026thinsp;300mV to +\u0026thinsp;1000 mV under light, the photocurrent density of 8.4, 3.8, 2.1 and 1.9 mA/cm\u003csup\u003e2\u003c/sup\u003e was found for CuC1, CuC3, CuC5 and CuO against applied potential of 0.8 V vs. Ag/AgCl. This increase in photocurrent density forCuC5, proposes that the charge separation is enhanced in the CuC5 photoanode as compared toCuC3, CuC1 and CuO, respectively.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eFurthermore, an electrochemical impedance spectrum (EIS), was valuable to find out the indication about increase charge transfer gradient approach at the interface of photoelectrode -electrolyte and separation efficiency of charge[\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e]. Figure\u0026nbsp;\u003cspan refid=\"Fig13\" class=\"InternalRef\"\u003e10\u003c/span\u003e exhibits the EIS Nyquist plots of the CuC1, CuC3, CuC5 and CuO photoelectrodes in the frequency range of 0.1 Hz to 10 kHz under light. Figure\u0026nbsp;\u003cspan refid=\"Fig13\" class=\"InternalRef\"\u003e10\u003c/span\u003e displays that the CuC5 electrode displays the minimum impedance semicircle and has lesser charge transfer resistance (R\u003csub\u003ect\u003c/sub\u003e) value than the other controlled samples CuC3, CuC1 and CuO electrode. Mostly, a smaller semicircle in EIS Nyquist plot agrees the effective charge carrier separation and a rapid interfacial charge transfer mechanism. This recommends CuC5 remarkably enhances the motion of electrons by reducing the recombination of electron\u0026ndash;hole pairs and helping to enable the photocatalytic activity.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThe Mott\u0026ndash;Schottky (MS) investigations of CuC1, CuC3, CuC5 and CuO were employed at frequency of 1 kHz in 0.5 M KOH solution in the presence of UV light. MS demonstrate the electron density of ternary CuC5(8.4\u0026times; 10\u003csup\u003e12\u003c/sup\u003e cm\u003csup\u003e3\u003c/sup\u003e) is higher as compared to CuC3 (6.2\u0026times; 10\u003csup\u003e10\u003c/sup\u003e cm\u003csup\u003e3\u003c/sup\u003e), CuC1 (4.3\u0026times; 10\u003csup\u003e10\u003c/sup\u003e cm\u003csup\u003e3\u003c/sup\u003e) and CuO (1.2\u0026times; 10\u003csup\u003e10\u003c/sup\u003e cm\u003csup\u003e3\u003c/sup\u003e) are measured by the equation mentioned in literature [\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e]. Furthermore, the flat band potential (E\u003csub\u003efb\u003c/sub\u003e) measured from the x-axis intercept of the MS plot showed in Fig.\u0026nbsp;\u003cspan refid=\"Fig14\" class=\"InternalRef\"\u003e11\u003c/span\u003e. Table\u0026nbsp;2 depicts the the flat band potential of the CuC5 (\u0026minus;\u0026thinsp;0.63) V/Ag/AgCl, is lesser than CuC3(\u0026minus;\u0026thinsp;0.41 V/Ag/AgCl), CuC1 (\u0026minus;\u0026thinsp;0.39 V/Ag/AgCl) and CuO (+\u0026thinsp;0.31 V/ Ag/AgCl), respectively, which determine the enhanced route of the photogenerated carriers.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cb\u003eTable.2.\u003c/b\u003e Current density, Charge transfer resistance, Flat and potential and electron donar density of CuO and nanocomposites (CCu1 CCu3 and CCu5) respectively.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Tabb\" border=\"1\"\u003e\u003ccolgroup cols=\"5\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\"\u0026times;\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eElectrodes\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eR\u003csub\u003ect\u003c/sub\u003e (Ω)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eCurrent density (mA/cm\u003csup\u003e2\u003c/sup\u003e)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eE\u003csub\u003efb\u003c/sub\u003e (e.V)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eN\u003csub\u003eD\u003c/sub\u003e (cm\u003csup\u003e3\u003c/sup\u003e)\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eCuC5\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.40\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e8.4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e-0.63\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c5\"\u003e\u003cp\u003e8.4\u0026times;10\u003csup\u003e12\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eCuC3\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e300.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e3.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e-0.41\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c5\"\u003e\u003cp\u003e6.2\u0026times;10\u003csup\u003e10\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eCuC1\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e650\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e2.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e-0.39\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c5\"\u003e\u003cp\u003e4.3\u0026times;10\u003csup\u003e10\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eCuO\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e834\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e1.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e+\u0026thinsp;0.31\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c5\"\u003e\u003cp\u003e1.2\u0026times;10\u003csup\u003e10\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e"},{"header":"4. Conclusion","content":"\u003cp\u003eIn this work CuO NPs were successfully synthesized by facile co-precipitation method at different temperatures (30\u0026deg;C, 60\u0026deg;C and 80\u0026deg;C). Furthermore, comparative studies of CuO-chitosan nanocomposites by using different CS concentrations (0.1 g, 0.3 g, and 0.5 g) is carried out. Characterization results discovered effective integration of chitosan on CuO surface and the concentrations of CS were detected to significantly affect the morphology, crystallite size and catalytic behavior of nanocomposite. Moreover, optical and photocatalytic degradation studies of CuO-Chitosan nanocomposites were examined via UV Visible spectroscopy, optical band gap tuning (3.36 to 3.29eV) revealed that CuC5 sample show 93% decolorization, higher adsorption properties due to increased surface area, availability of functional groups for binding and better dispersion of CuO NPs. While optoelectronic investigations were also revealed that CuC5 nanocomposite exhibits higher current density, lower charge transfer resistance, and high electron Donar density due to the homogeneous dispersion of CS and improved interaction among CuO NPs and CS polymer. These findings recommends that CCu5 nanocomposite is a promising candidate for photodegradation of MB and photoelectrochemical activity which is an economical and eco-friendly process.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgment\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors gratefully acknowledge support from the Department of Chemistry, Sardar Bahadur Khan Women\u0026rsquo;s University, Quetta, Pakistan and Department of Chemistry, Government College University Lahore, Pakistan; the author also acknowledges HEC (Pakistan), NRPU Research Grant # 20-17618/NRPU/R\u0026amp;D/HEC/2021-2020.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting Interests\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors have no relevant financial or non-financial interests to disclose.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor Contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eLaraib Bibi Methodology, Investigation, Conceptualization, Writing - Original Draft, Methodology, Investigation, Saba Afzal,\u003csub\u003e\u0026nbsp;\u003c/sub\u003eMadina: Conceptualization, Supervision, Formal analysis, Investigation Ishrat Fatima, Rabia Naeem, Bibi Sherino, Huma Tareen: Writing - Review \u0026amp; Editing, Investigation, Formal analysis, \u0026nbsp;and Interpretation data Analysis.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData availability\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;The datasets generated during and/or analyzed during the current study are available from the corresponding author on reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAI tool:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe manuscript was entirely human-written and Turnitin tool is used as an AI Detection feature which help to identify the AI-generated content in submitted manuscript\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eEhsan, M.A., et al., \u003cem\u003eFacile fabrication of CeO2\u0026ndash;TiO2 thin films via solution based CVD and their photoelectrochemical studies.\u003c/em\u003e Journal of Materials Science: Materials in Electronics, 2018. \u003cstrong\u003e29\u003c/strong\u003e(15): p. 13209-13219.\u003c/li\u003e\n\u003cli\u003eMansoor, M.A., et al., \u003cem\u003eA Tri-Metallic (Mn\u0026ndash;Co\u0026ndash;Ti) Oxide Photoanode with Improved Photo-Conversion Efficiency.\u003c/em\u003e Russian Journal of Inorganic Chemistry, 2021. \u003cstrong\u003e66\u003c/strong\u003e: p. 806-813.\u003c/li\u003e\n\u003cli\u003eHassan, F., et al., \u003cem\u003eComposite electrodes with superior catalytic activity in methanol electro-oxidation fabricated using ternary NiO\u0026ndash;CuO\u0026ndash;ZnO mixed metal oxides.\u003c/em\u003e New Journal of Chemistry, 2024. \u003cstrong\u003e48\u003c/strong\u003e(8): p. 3614-3623.\u003c/li\u003e\n\u003cli\u003eIrfan, M.F., et al., \u003cem\u003eStructural, morphological, and electrocatalytic investigations of Fe 3 O 4-doped Mn 3 O 4 composite supported on carbonaceous materials derived from chitosan for oxygen reduction reaction.\u003c/em\u003e New Journal of Chemistry, 2025. \u003cstrong\u003e49\u003c/strong\u003e(6): p. 2308-2318.\u003c/li\u003e\n\u003cli\u003eul-Ain, M., et al., \u003cem\u003eEnhancing Cr(VI) remediation efficiency using hemp-derived biochar: insights into RSM optimization and adsorption kinetics using ANN modelling.\u003c/em\u003e International Journal of Environmental Science and Technology, 2025. \u003cstrong\u003e22\u003c/strong\u003e(15): p. 15189-15210.\u003c/li\u003e\n\u003cli\u003eAfzal, S., et al., \u003cem\u003eImpact of chitosan on CS/TiO2 composite system for enhancing its photocatalytic performance towards dye degradation.\u003c/em\u003e DESALINATION AND WATER TREATMENT, 2023. \u003cstrong\u003e283\u003c/strong\u003e: p. 274-279.\u003c/li\u003e\n\u003cli\u003eMansoor, M.A., et al., \u003cem\u003eAerosol-assisted facile fabrication of bimetallic Cr2O3\u0026ndash;Mn2O3 thin films for photoelectrochemical water splitting.\u003c/em\u003e New Journal of Chemistry, 2023. \u003cstrong\u003e47\u003c/strong\u003e(17): p. 8347-8354.\u003c/li\u003e\n\u003cli\u003eNaeem, R., et al., \u003cem\u003ePhotoelectrochemical properties of morphology controlled manganese, iron, nickel and copper oxides nanoball thin films deposited by electric field directed aerosol assisted chemical vapour deposition.\u003c/em\u003e Materials Today Communications, 2015. \u003cstrong\u003e4\u003c/strong\u003e: p. 141-148.\u003c/li\u003e\n\u003cli\u003eFouda, A., et al., \u003cem\u003eOptimization of green biosynthesized visible light active CuO/ZnO nano-photocatalysts for the degradation of organic methylene blue dye.\u003c/em\u003e Heliyon, 2020. \u003cstrong\u003e6\u003c/strong\u003e(9).\u003c/li\u003e\n\u003cli\u003eNaeem, R., et al., \u003cem\u003eOptical and optoelectronic properties of morphology and structure controlled ZnO, CdO and PbO thin films deposited by electric field directed aerosol assisted CVD.\u003c/em\u003e Journal of Materials Science: Materials in Electronics, 2017. \u003cstrong\u003e28\u003c/strong\u003e(1): p. 868-877.\u003c/li\u003e\n\u003cli\u003eEhsan, M.A., et al., \u003cem\u003eFabrication of photoactive CaTiO3\u0026ndash;TiO2 composite thin film electrodes via facile single step aerosol assisted chemical vapor deposition route.\u003c/em\u003e Journal of Materials Science: Materials in Electronics, 2019. \u003cstrong\u003e30\u003c/strong\u003e(2): p. 1411-1424.\u003c/li\u003e\n\u003cli\u003eBassi, A., et al., \u003cem\u003eCuO Nanorods Immobilized Agar-Alginate Biopolymer: A Green Functional Material for Photocatalytic Degradation of Amaranth Dye.\u003c/em\u003e Polymers, 2023. \u003cstrong\u003e15\u003c/strong\u003e(3): p. 553.\u003c/li\u003e\n\u003cli\u003eChan, Y.B., et al., \u003cem\u003eEffect of Calcination Temperature on Structural, Morphological and Optical Properties of Copper Oxide Nanostructures Derived from Garcinia mangostana L. Leaf Extract.\u003c/em\u003e Nanomaterials, 2022. \u003cstrong\u003e12\u003c/strong\u003e(20): p. 3589.\u003c/li\u003e\n\u003cli\u003eHalfadji, A., et al., \u003cem\u003eEffective investigation of electro-catalytic, photocatalytic, and antimicrobial properties of porous CuO nanoparticles green synthesized using leaves of Cupressocyparis leylandii.\u003c/em\u003e Journal of Molecular Structure, 2024. \u003cstrong\u003e1301\u003c/strong\u003e: p. 137318.\u003c/li\u003e\n\u003cli\u003eShabbir, S., et al., \u003cem\u003eOptoelectronic and Photocatalytic investigations of chitosan (CS) modified Platinum decorated ceria (Pt-CeO2-CS) composite.\u003c/em\u003e Optical Materials, 2024. \u003cstrong\u003e157\u003c/strong\u003e: p. 116376.\u003c/li\u003e\n\u003cli\u003eHisham, F., et al., \u003cem\u003eBiopolymer chitosan: Potential sources, extraction methods, and emerging applications.\u003c/em\u003e Ain Shams Engineering Journal, 2024. \u003cstrong\u003e15\u003c/strong\u003e(2): p. 102424.\u003c/li\u003e\n\u003cli\u003eHaldorai, Y. and J.-J. Shim, \u003cem\u003eMultifunctional chitosan‐copper oxide hybrid material: Photocatalytic and antibacterial activities.\u003c/em\u003e International Journal of Photoenergy, 2013. \u003cstrong\u003e2013\u003c/strong\u003e(1): p. 245646.\u003c/li\u003e\n\u003cli\u003eUmoren, P.S., et al., \u003cem\u003eBiogenic Synthesis and Characterization of Chitosan-CuO Nanocomposite and Evaluation of Antibacterial Activity against Gram-Positive and -Negative Bacteria.\u003c/em\u003e Polymers, 2022. \u003cstrong\u003e14\u003c/strong\u003e(9): p. 1832.\u003c/li\u003e\n\u003cli\u003eWahid, F., et al., \u003cem\u003ePreparation, characterization and antibacterial applications of carboxymethyl chitosan/CuO nanocomposite hydrogels.\u003c/em\u003e International journal of biological macromolecules, 2017. \u003cstrong\u003e101\u003c/strong\u003e: p. 690-695.\u003c/li\u003e\n\u003cli\u003eDulta, K., et al., \u003cem\u003eMultifunctional CuO nanoparticles with enhanced photocatalytic dye degradation and antibacterial activity.\u003c/em\u003e Sustainable Environment Research, 2022. \u003cstrong\u003e32\u003c/strong\u003e(1): p. 2.\u003c/li\u003e\n\u003cli\u003eNaeem, R., et al., \u003cem\u003eSingle step aerosol assisted chemical vapor deposition of p\u0026ndash;n Sn(ii) oxide\u0026ndash;Ti(iv) oxide nanocomposite thin film electrodes for investigation of photoelectrochemical properties.\u003c/em\u003e New Journal of Chemistry, 2018. \u003cstrong\u003e42\u003c/strong\u003e(7): p. 5256-5266.\u003c/li\u003e\n\u003cli\u003eNaeem, R., et al., \u003cem\u003eVersatile Fabrication of Binary Composite SnO 2-Mn 2 O 3 Thin Films by AACVD for Synergistic Photocatalytic Effect.\u003c/em\u003e Journal of Electronic Materials, 2021. \u003cstrong\u003e50\u003c/strong\u003e: p. 3897-3906.\u003c/li\u003e\n\u003cli\u003eEhsan, M.A., et al., \u003cem\u003eFabrication of CoTiO3\u0026ndash;TiO2 composite films from a heterobimetallic single source precursor for electrochemical sensing of dopamine.\u003c/em\u003e Dalton Transactions, 2016. \u003cstrong\u003e45\u003c/strong\u003e(25): p. 10222-10232.\u003c/li\u003e\n\u003cli\u003eSherino, B., et al., \u003cem\u003eAn Efficient Electrochemical Sensing of Hydrogen Peroxide on Zn-Based Coordination Polymer Decorated Carbon Paste Electrode.\u003c/em\u003e Journal of The Electrochemical Society, 2024. \u003cstrong\u003e171\u003c/strong\u003e(8): p. 087516.\u003c/li\u003e\n\u003cli\u003eMarriam, F., et al., \u003cem\u003eSynergistic approach of TiO2@ MnZnO3 heterostructure for efficient photoelectrochemical water splitting.\u003c/em\u003e Journal of The Electrochemical Society, 2024. \u003cstrong\u003e171\u003c/strong\u003e(9): p. 096501.\u003c/li\u003e\n\u003cli\u003eEl-Atawy, M.A., K.D. Khalil, and A.H. Bashal, \u003cem\u003eChitosan capped copper oxide nanocomposite: Efficient, recyclable, heterogeneous base catalyst for synthesis of nitroolefins.\u003c/em\u003e Catalysts, 2022. \u003cstrong\u003e12\u003c/strong\u003e(9): p. 964.\u003c/li\u003e\n\u003cli\u003ePaul, S., D. M.K, and S. Peter, \u003cem\u003eDevelopment of Green Synthesized Chitosan-coated Copper Oxide Nanocomposite Gel for Topical Delivery.\u003c/em\u003e Journal of Pharmaceutical Innovation, 2023. \u003cstrong\u003e18\u003c/strong\u003e(3): p. 1010-1019.\u003c/li\u003e\n\u003cli\u003eDulta, K., et al., \u003cem\u003eMultifunctional CuO nanoparticles with enhanced photocatalytic dye degradation and antibacterial activity.\u003c/em\u003e Sustainable Environment Research, 2022. \u003cstrong\u003e32\u003c/strong\u003e(1): p. 2.\u003c/li\u003e\n\u003cli\u003eJillani, S., et al., \u003cem\u003eSynthesis, characterization and biological studies of copper oxide nanostructures.\u003c/em\u003e Materials Research Express, 2018. \u003cstrong\u003e5\u003c/strong\u003e(4): p. 045006.\u003c/li\u003e\n\u003cli\u003eSathiyavimal, S., et al., \u003cem\u003eEco-biocompatibility of chitosan coated biosynthesized copper oxide nanocomposite for enhanced industrial (Azo) dye removal from aqueous solution and antibacterial properties.\u003c/em\u003e Carbohydrate Polymers, 2020. \u003cstrong\u003e241\u003c/strong\u003e: p. 116243.\u003c/li\u003e\n\u003cli\u003eNaeem, R., et al., \u003cem\u003eThe photoelectrochemically enhanced oxygen evolution reaction via thin films of novel (1:2:1) SnO-Mn2O3-TiO2 hybrid nanotubes.\u003c/em\u003e Surfaces and Interfaces, 2024. \u003cstrong\u003e46\u003c/strong\u003e: p. 104034.\u003c/li\u003e\n\u003cli\u003eMunawar, K., et al., \u003cem\u003eTemperature-controlled deposition of NiO-ZnO composite thin films: optical and photoelectrochemical properties.\u003c/em\u003e Journal of Applied Electrochemistry, 2025. \u003cstrong\u003e55\u003c/strong\u003e(9): p. 2481-2496.\u003c/li\u003e\n\u003cli\u003eMunawar, K., et al., \u003cem\u003eEffect of deposition temperature on topography and electrochemical water oxidation of NiO thin films.\u003c/em\u003e Thin Solid Films, 2023. \u003cstrong\u003e782\u003c/strong\u003e: p. 140031.\u003c/li\u003e\n\u003cli\u003eNaeem, R., et al., \u003cem\u003eFabrication of pristine Mn2O3 and Ag\u0026ndash;Mn2O3 composite thin films by AACVD for photoelectrochemical water splitting.\u003c/em\u003e Dalton Transactions, 2016. \u003cstrong\u003e45\u003c/strong\u003e(38): p. 14928-14939.\u003c/li\u003e\n\u003c/ol\u003e"},{"header":"Scheme 1","content":"\u003cp\u003eScheme 1 is available in the Supplementary Files section.\u003c/p\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":"CuO-Chitosan, Nanocomposites, Optical band gap, Photodegradation, Methylene blue, optoelectronic properties","lastPublishedDoi":"10.21203/rs.3.rs-7982430/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7982430/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe development of a stable and extremely active photocatalyst has attracted substantial consideration in the area of wastewater treatment and photoelectrocatalytic (PEC) water splitting. In recent work, flakes-like CuO–chitosan nanocomposites were effectively synthesized to investigate the impact of chitosan loading on their structural, photocatalytic degradation of Methylene blue (MB) and optoelectronic characteristics. The CuO–chitosan nanocomposites were prepared via a simple co-precipitation route by varying chitosan contents (0.1 g (CCu1), 0.3 g (CCu3), and 0.5 g (CCu5)).\u0026nbsp; FTIR and X-ray diffraction (XRD) confirmed the structural studies like monoclinic phase of CuO, its smaller crystallite size was observed with increased chitosan concentration. SEM/EDX analyses revealed a flakes-like morphology and composition with enhanced surface uniformity and reduced agglomeration upon chitosan incorporation. The optical performance of CuO-Chitosan nanocomposites was assessed with UV by evaluating optical band gaps of CCu1(3.34eV), CCu3(3.32eV), and CCu5 (3.29eV), suggesting CS incorporation effectively reduce band gap of pure CuO (3.36 eV).\u0026nbsp; Photocatalytic degradation investigations revealed that optimized chitosan loading significantly enhanced degradation efficiency of CCu5 which shows 93 % degradation of methylene blue (MB) within 150 min under visible light. The optoelectronic characteristics of all four samples were tested by LSV, EIS and MS plots. Among them CuC5 depicts higher current density, low charge transfer resistance and greater electron Donar density (Nd =8.4×10\u003csup\u003e12 \u003c/sup\u003ecm\u003csup\u003e3\u003c/sup\u003e) as compared to CuC1, CuC3 and CuO respectively. The results highlight that controlled chitosan loading effectively modify the physicochemical, photocatalytic dye degradation and optoelectronic properties of CuO, making them promising candidates for environmental remediation and photocatalytic applications.\u003c/p\u003e","manuscriptTitle":"Effect of Chitosan loading towards structural, optoelectronic and photocatalytic degradation of flakes like CuO-Chitosan nanocomposite","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-11-13 13:49:22","doi":"10.21203/rs.3.rs-7982430/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":"9db3a05a-bca8-47fa-bb30-6bbfd5ea6f45","owner":[],"postedDate":"November 13th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2026-04-20T15:38:33+00:00","versionOfRecord":[],"versionCreatedAt":"2025-11-13 13:49:22","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7982430","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7982430","identity":"rs-7982430","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}