Harnessing the Power of S/N Doped NiO Nanoparticles: Bandgap Tuning for Superior Photocatalytic and Antibacterial Performance

Harnessing the Power of S/N Doped NiO Nanoparticles: Bandgap Tuning for Superior Photocatalytic and Antibacterial Performance | 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 Harnessing the Power of S/N Doped NiO Nanoparticles: Bandgap Tuning for Superior Photocatalytic and Antibacterial Performance Tariku Tamesgen, Michael Asfaw Ameya, Getu Sisay, Lu Yuanqi, Zhu Kai, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6493877/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 Nickel oxide (NiO) has gained attention as a promising photocatalyst, thanks to its high efficiency, photochemical stability, cost-effectiveness, and eco-friendly nature. However, a wide band gap and rapid electron-hole recombination hinder its practical application under visible light. This study synthesized pure NiO nanoparticles (NiO-NPs) and sulfur/nitrogen co-doped NiO nanoparticles (S/N-NiO-NPs) via the co-precipitation method. Comprehensive structural and optical analyses using UV-Vis, FT-IR, XRD, and SEM confirmed the successful formation of the desired materials. Notably, doping with 4% sulfur and 6% nitrogen significantly enhanced charge separation, extended light absorption, narrowed the band gap from 3.75 eV to 2.50 eV, and reduced crystalline size from 20.49 nm to 17.89 nm. Under optimal conditions (pH 10),40 mg of S/N-NiO-NPs achieved an impressive 98.9% degradation of 5 ppm methylene blue dye within just 60 min of sunlight irradiation, far outperforming pure NiO-NPs. Additionally, antibacterial evaluations demonstrated superior efficacy, with S/N-NiO-NPs exhibiting inhibition zones of13–17 mm against pathogens such as Bacillus cereus , Escherichia coli , Salmonella typhi , and Staphylococcus aureus , compared to the 5–10 mm zones observed for pure NiO-NPs. These results highlight the remarkable potential of S/N co-doping in transforming NiO into a highly efficient, multifunctional material for environmental remediation and biomedical applications. Antibacterial Energy band gap methylene blue dye degradation nanoparticles S/N co-doping NiO-NPs Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 1. INTRODUCTION Environmental pollution; especially water pollution from industrial dye effluents; has become a pressing global issue. Industries such as textiles, mining, paper production, food processing, pharmaceuticals, and leather manufacturing are major contributors, releasing large volumes of organic dyes that severely contaminate water sources 1 . Due to their non-biodegradable nature, toxicity, carcinogenic potential, and tendency to bioaccumulate, these dyes pose serious threats to both aquatic ecosystems and human health. In response, various treatment methods; such as ion exchange 2 , adsorption 3 , electrochemical treatment, and photocatalytic degradation 4 have been explored. Among the available methods, photocatalysis stands out as the most effective for real-world applications, offering a clean solution that breaks down pollutants without producing harmful byproducts or secondary waste 5 . This process not only degrades complex organic dyes but also offers an environmentally friendly alternative to other methods, thanks to its high efficiency and relatively low costs 6 . The growing threat of multidrug-resistant (MDR) bacteria is another critical global health challenge. Overuse and misuse of traditional antibiotics have fueled the rise of resistant pathogens, leading to a surge in hard-to-treat infections caused by bacteria, viruses, fungi, and parasites 7 . While antibiotics revolutionized medicine in the 20th century 8 , the need for new treatments to combat antibiotic resistance is more urgent than ever. In response, nanotechnology has introduced innovative approaches, such as nanoparticles doped with specific elements, to tackle this growing problem 9 . Nanoparticles, due to their large surface-to-volume ratio and unique physicochemical properties, hold significant promise in fields like antimicrobial therapy and photo catalysis. Metal oxide nanoparticles, particularly those doped with metals or non-metals, have shown enhanced photocatalytic and antibacterial properties 10 . In the case of photocatalysis, metal oxide catalysts like NiO have demonstrated considerable efficacy in degrading organic pollutants. However, their performance is often limited by issues such as high electron-hole recombination rates and large energy band gaps 11 . To address the aforementioned limitations, doping NiO with elements such as sulfur (S) and nitrogen (N) were explored. These dopants reduce the band gap, increase the dissociation of photo-generated electron-hole pairs, and improve the catalyst's absorption in the visible light range, thereby enhancing photo catalytic and antibacterial activities. NiO-NPs, when doped with sulfur and nitrogen, have shown promising results in overcoming the challenges of pure NiO-NPs 12 . The motivation for synthesizing S/N co-doped NiO nanoparticles (S/N co-doped NiO-NPs) for antibacterial activity and photocatalytic degradation stems from the unique properties of NiO, which distinguish it from widely studied materials like S/N co-doped ZnO and carbon quantum dots (CQDots) and the like. NiO, as a p-type semiconductor, demonstrates exceptional stability, resistance to photo corrosion, and robustness under harsh conditions 13 . Doping with sulfur and nitrogen effectively narrows its band gap, enhances light absorption in the visible spectrum, and improves charge carrier separation, significantly boosting its photocatalytic and antibacterial efficiency. Research has shown that doped NiO nanoparticles have achieved high performance in various environmental applications. For instance, nitrogen-doped NiO has demonstrated enhanced photocatalytic CO 2 reduction efficiency and improved electron-hole separation capabilities, confirming its potential for light-driven applications under visible light irradiation 14 . Studies on other doped forms of NiO have also highlighted its superior durability and activity compared to other semiconductors, making it a strong candidate for multifunctional applications such as water treatment and microbial inhibition 14 , 15 . This study investigates the impact of sulfur/nitrogen (S/N) co-doping on the energy band gap, photocatalytic degradation efficiency of methylene blue (MB) dye, and antibacterial activity of nickel oxide nanoparticles (NiO-NPs). The nanoparticles were synthesized using a precipitation method, and their structural and optical characteristics were thoroughly examined using FTIR, UV-Vis spectroscopy, SEM, and XRD analyses. UV-Vis results revealed a redshift in the maximum absorbance wavelength upon S/N incorporation, indicating enhanced light absorption. Notably, S/N co-doping reduced the energy band gap of NiO-NPs from 3.75 eV to 2.50 eV, significantly boosting their photocatalytic efficiency. Under optimal conditions (pH 10, 40 mg catalyst dosage), nearly complete degradation of 5 ppm MB dye (98.9%) was achieved within 60 minutes. Furthermore, S/N co-doped NiO-NPs demonstrated markedly improved antibacterial performance compared to their undoped counterparts. These findings highlight the potential of S/N co-doping in enhancing the photocatalytic and antimicrobial properties of NiO-NPs, making them promising candidates for environmental remediation and biomedical applications. 2. RESULT AND DISCUSSION Detailed descriptions of the materials and experimental procedures used in this study are available in the Supporting Information. A schematic illustration of the synthesis process is presented as Figure S1 (supplementary information). Additionally, the Supporting Information includes the optimization of key parameters such as concentration, pH, reaction time, and temperature. 2.1. Parameters Optimization for the synthesis of S/N co-doped NiO NPs 2.1.1. Parameters Optimization for the synthesis of NiO NPs In this study, an optimization approach for synthesizing NiO NPs with small size and smaller band gap were reported. 2.1.1.1. Effect of metal ion concentrations on NiO-NPs synthesis Nickel nitrate hexahydrate (Ni(NO₃)₂·6H₂O) was used as a precursor at varying concentrations; 0.05 M, 0.1 M, and 0.15 M (see Figure S2a ); while maintaining consistent reaction parameters, including pH, temperature, and duration. To initiate precipitation, 1 M sodium hydroxide (NaOH) was gradually added until the pH reached 10, with continuous stirring at 600 rpm for 3 h at 60°C. This process produced a slow-forming green precipitate. The resulting mixture was filtered through Whatman No. 1 filter paper, thoroughly washed with ethanol, then oven-dried at 120°C and finally annealed at 400°C to obtain a fine green powder of nickel oxide nanoparticles (NiO-NPs). Notably, increasing the concentration of Ni(NO₃)₂·6H₂O to 0.15 M led to a reduction in peak intensity, suggesting enhanced nucleation and aggregation during nanoparticle formation. Based on these observations, 0.1 M Ni(NO₃)₂·6H₂O was identified as the optimal concentration for synthesizing S/N co-doped NiO-NPs 16 . 2.1.1.2. Effect of pH on synthesis of NiO-NPs In this study, the effect of pH on the formation of NiO-NPs was investigated using UV-Vis spectroscopy. The synthesis was carried out at various pH levels: 6, 8, 10, and 12: to assess how the reaction medium affects nanoparticle production (see Figure S2). At lower, acidic pH values (< 7), a broader absorption peak was observed, indicating the formation of relatively larger nanoparticles, with sizes reaching approximately 158 nm. These findings highlight the importance of pH optimization in achieving desired nanoparticle characteristics 17 . As the pH increased from 8 to 12, the UV-Vis absorption peaks became sharper and more intense, with the most pronounced peak observed at pH 10; signifying the formation of smaller, well-defined nanoparticles. In contrast, further increasing the pH to 12 resulted in a broader absorption band, indicative of larger particle formation due to aggregation. The distinct blue shift observed at pH 10 confirms a reduction in particle size, marking it as the optimal condition for synthesizing finely tuned NiO nanoparticles 18 . The result revealed that it was unable to function above pH 12 as illustrated in Figure S2b . 2.1.1.3. Effect of Calcination temperature on Synthesis of NiO-NPs Temperature plays a vital role in determining the shape, size, stability, and overall yield of synthesized nanoparticles. While green synthesis methods typically operate at temperatures below 100°C or room temperature, this study explored the influence of higher temperatures ranging from 300°C to 500°C on the formation of NiO-NPs, with all other parameters held constant ( Figure S2c ). As the temperature increased, the UV-Vis absorption peaks became progressively sharper, indicating improved crystallinity and size uniformity. Notably, at 400°C, a distinct and narrow peak was observed, suggesting the formation of well-defined, smaller nanoparticles. This improvement can be attributed to enhanced reaction kinetics and increased nucleation at elevated temperatures. However, at 500°C, the absorption peak broadened once again, signaling a wider particle size distribution likely caused by aggregation due to excessive growth rates. Based on these observations, 400°C was identified as the optimal temperature for synthesizing high-quality NiO-NPs 19 . 2.1.1.4. Effect of Stirring time on Synthesis of NiO-NPs Reaction time is essential for the synthesis and stability of NPs. The effect of reaction time was studied in the synthesis of NiO-NPs. The effect of reaction time was conducted by analysing the sample through the UV-Vis spectrum at every 1 h difference from 2 h to 4 h for the synthesis of NiO NPs ( Figure S2d ). NiO-NPs UV-Vis spectrum displayed a small intensity peak at 2 h, and the intensity of the peak increased, and the peak became narrower as the time progressed to 3 h. This indicated an enhanced nucleation rate and the formation of small-sized NPs. By further increasing reaction time, the absorbance peak became broader, which might lead to an increase in particle size. This was caused by overgrowth or aggregation of NPs, affecting their size, distribution, and stability 20 . Accordingly, 3 h was the optimum time for synthesized NiO-NPs. 2.2. Optimization for the synthesis of S/N co-doped NiO-NPs The absorption peak of S/N-NiO nanoparticles (NPs) were influenced by the concentration of the dopant. This study examined the effects of different mass ratios of dopants (mg) for sulfur (S), nitrogen (N), and nickel oxide (NiO) in three combinations: 1:1:20, 2:3:50, and 3:7:100, while keeping other parameters constant. It was noted that increasing the dopant concentration resulted in a redshift of the absorption wavelength, as depicted in Figure S3c . The optimal results were achieved with a dopant concentration of 4% sulfur and 6% nitrogen, which produced the most significant redshift in the UV-Vis absorbance spectrum, measured at 329 nm. 2.3. Characterization The NiO-NPs, N-doped NiO-NPs, S-doped NiO-NPs and S/N co-doped NiO-NPs, produced by the precipitation method, and were characterized using UV-Vis, XRD, FTIR, and SEM. The light absorption characteristics of NiO nanoparticles (NiO-NPs), nitrogen-doped NiO-NPs, sulfur-doped NiO-NPs, and nitrogen/sulfur co-doped NiO-NPs were measured using a spectrophotometer. The electronic excitation spectra for pure NiO-NPs, nitrogen-doped NiO-NPs, sulfur-doped NiO-NPs, and co-doped NiO-NPs were recorded in the 280–600 nm wavelength range. The absorbance peaks were observed at 303 nm for pure NiO-NPs, 307 nm for nitrogen-doped NiO-NPs, 305 nm for sulfur-doped NiO-NPs, and 329 nm for nitrogen/sulfur co-doped NiO-NPs. These peaks indicate that doping with nitrogen and sulfur resulted in a red shift in absorbance. Notably, the nitrogen doping caused a slightly more significant red shift compared to sulfur, highlighting its stronger impact on the electronic properties of the material. The absorbance of the co-doped NiO-NPs at 329 nm demonstrates a noticeable shift toward a longer wavelength, signifying that the doping has modified the material's electronic structure 22 , indicating that doping has altered the electronic structure of the material. The optical band gap of the synthesized samples was calculated using the Tauc equation, as illustrated in Eq. 1. ( αhν) = A (hν-Eg) n ………………………………………………………………1 Where Eg is the optical band gap, h is Planck's constant, A is constant, and α is the absorption coefficient. The direct energy band gap was determined as depicted in Fig. 1 (b to e). The optical band gap values for NiO, N-doped NiO, S-doped NiO, and S/N co-doped NiO-NPs were found to be 3.75 eV, 3.2 eV, 3.45 eV, and 2.50 eV, respectively. These results suggest that doping with nitrogen and sulfur reduces the band gap of NiO. Specifically, the S/N co-doped NiO nanoparticles exhibit the smallest band gap (2.50 eV), which can be attributed to lattice contraction and the creation of vacancies and energy states due to the incorporation of nonmetal dopants like S and N 23 . This reduction in the band gap facilitates the absorption of light across a wider range of the spectrum, including visible light, which is a critical factor for enhancing the photo catalytic activity of the material 24 . In summary, doping NiO with sulfur and nitrogen not only reduces the band gap but also improves the material's ability to absorb visible light, making it more effective for applications such as photo catalysis, antibacterial treatment, and dye degradation. The summarized optical properties and calculated band gaps of the materials are given in Table 1 . Table 1 Optical properties of the prepared materials. Types of Nanomaterials Maximum Absorbance(nm) Calculated band gap energy(eV) NiO-NPs 303 3.75 N-doped NiO-NPs 307 3.2 S-doped NiO-NPs S/N co-doped NiO-NPs 305 329 3.45 2.50 To verify the crystallinity of the nanoparticles and to evaluate the effect of C-dot inclusion on their crystalline structure, we measured and presented the X-ray diffraction (XRD) patterns of pure NiO nanoparticles and S/N co-doped NiO nanoparticles, as shown in Fig. 2 a. The XRD analysis revealed diffraction peaks at 2θ values of 37.58°, 43.54°, 63.09°, 75.68°, and 79.64° for NiO nanoparticles, which correspond to the diffraction planes (111), (200), (202), (311), and (222) of the face-centered cubic (FCC) structure of NiO. These peaks align well with the standard JCPDS card (JCPDS #96-101-0096), confirming that NiO adopts the FCC structure. The sharpness of these peaks indicates high crystallinity. Additionally, we observed a weak peak at 39.6° in the XRD pattern of NiO, which is attributed to a minor impurity of metallic nickel. This suggests that some reduction of Ni²⁺ to Ni occurred during the synthesis process; however, this impurity is relatively minor, as it is only visible as a weak peak in the pattern. For the S/N co-doped NiO-NCs, the same diffraction peaks at 37.36°, 43.4°, 63.04°, 75.56°, and 79.58° are observed, which correspond to the same planes (111), (200), (202), (311), and (222), indicating that the overall crystalline structure of NiO remains unchanged even after doping with sulfur and nitrogen. This suggests that the doping process does not induce a major phase change in the material but rather influences its crystallite size and micro strain 25 . The diffraction peaks for S/N co-doped NiO-NPs are broader compared to pure NiO-NPs, this Peak broadening typically indicates a reduction in crystallite size. This could be a result of the incorporation of sulfur and nitrogen ions into the NiO lattice, which disrupts the regular arrangement of NiO, leading to strain within the crystal lattice. The intensity of the diffraction peaks also decreases for the doped samples, further supporting the idea that doping with S and N leads to a less ordered crystalline structure, likely due to the differences in ionic radii between Ni (Ni²⁺, 0.069 nm), S (S 2 - , 0.184 nm), and N (N 3 - , 0.146 nm) ions. The larger ionic radii of sulfur and nitrogen compared to nickel ions likely cause lattice distortion, which can result in reduced crystallinity and peak intensity 21 .The results are consistent with the standard reference (JCPDS Card No: 01-078-0423) 25 . This confirms that the doping process does not alter the overall crystalline structure of NiO but affects its crystallite size and micro strains. To calculate the average crystallite size, the Debye-Scherer equation which is expressed in Eq. 2. The d-spacing values for both the pure NiO-NPs and the S/N co-doped NiO-NPs are very similar, with slight shifts due to the doping process ( Table 2 ) . These shifts are expected, as the introduction of sulfur and nitrogen ions into the NiO lattice could cause some strain and potentially slightly expand the lattice parameters. However, overall, the crystalline structure remains essentially unchanged, confirming that the doping process doesn’t disrupt the fundamental face-centered cubic (FCC) structure of NiO. The particle size of the S/N co-doped NiO-NPs (17.49nm) is smaller than that of the pure NiO-NPs (20.89nm). D= (0.9 λ)/βcosθ…………………………………………………………………2 Here, λ represents the X-ray wavelength, D is the average crystal size, θ is the Bragg diffraction angle, and β is the FWHM in radians. Table 2 Summary of the d-spacing for both NiO NPs and S/N co-doped NiO NPs : Plane 2θ (degree) (NiO) d-spacing (NiO) (Å) 2θ (degree) (S/N co-doped) d-spacing (S/N co-doped) (Å) (111) 37.58 2.39 37.36 2.45 (200) 43.54 2.08 43.40 2.09 (202) 63.09 1.50 63.04 1.58 (311) 75.68 1.24 75.56 1.26 (222) 79.64 1.21 79.58 1.23 The functional groups present in the synthesized nanoparticles were identified using Fourier Transform Infrared spectroscopy, as shown in Fig. 2 b. The FT-IR spectra reveal the unique stretching and bending vibrations associated with various functional groups in both pure NiO and S/N co-doped NiO nanoparticles. Prominent peak observed at 3419–3426 cm − 1 is attributed to the O-H stretching vibrations of water molecules adsorbed on the surface of the nanoparticles. This is a common feature in metal oxide nanoparticles, which tend to absorb moisture from the surrounding environment. The O-H bending vibration of the water molecules results in a strong absorption band at 1633 cm − 1 is, further confirming the presence of adsorbed water on the surface of the nanoparticles. Furthermore, the C = O (for pure NiO-NPs) may be responsible for the absorption bands at 1389 cm − 1 and 1740 cm − 1 . Following calcinations, the presence of hydroxyl and carbonyl groups in the NiO nanoparticles as-prepared suggests that the powder has a strong propensity to physically absorb CO 2 and water 26 . The peaks that formed at 1394 cm − 1 , were created by the C = O stretching vibration of absorbed by the samples. While the peaks seen at 575 cm − 1 and 833 cm − 1 were ascribed to the link between metal and oxygen (Ni-O), the peak that emerged at 2422 cm − 1 was ascribed to the presence of C = C stretching of alkenes molecules. The small peak that emerged at 1038 cm − 1 shows that incorporation of dopants into the NiO crystal lattice 27 was successful. To clarify the external structure of pure NiO-NPs and S/N co-doped NiO-NPs SEM analysis was conducted. The SEM images of pure NiO-NPs and S/N co-doped NiO-NPs are displayed in Figure-2(c-d) . The SEM image of NiO-NPs ( Fig. 2 c ) reveals a rock-like surface morphology formed by the aggregation of nanoparticles. These particles are uniformly dispersed in size but exhibit an agglomerated configuration 28 . In contrast, the SEM image of S/N co-doped NiO-NPs ( Fig. 2 d ) shows spherical, interconnected particles, suggesting a strong interaction between the components that promotes the formation of particle aggregates 17 . 2.4. Photocatalytic activity test In the present study S/N co-doped NiO nanoparticles was used to study the photocatalytic degradations of the methyl blue (MB) dye. S/N co-doped NiO nanoparticles then subjected to sun radiation (@ Jimma) at intervals of 10, 20, 30, 40, 50, and 60 min. A slow change in the dye solution's change from blue to colorless indicated the beginning of the dye degradation, which was followed by the steady decline of the characteristic MB absorption peak strength, which was detected at 666 nm. 2.5. Effect of reaction parameters on photocatalysis Before the actual photocatalytic test, a number of photocatalytic requirements were carefully adjusted. These factors included the impacts of starting dye concentration pH, catalyst dose, and Time of Contact. 2.5.1. Effect of Initial Dye Concentration The initial concentration of MB dye affects the photo catalytic performance. As shown in ( Fig. 3 a ) , the photo catalytic activity is higher at lower dye concentrations (5ppm), with the degradation efficiency decreasing at higher concentrations. At higher dye concentrations, the solution absorbs more light, limiting photon penetration and reducing the generation of hydroxyl radicals. Consequently, the degradation efficiency decreases as the dye concentration increases, with a maximum of 98.9% degradation observed at 5ppm MB dye 29 . 2.5.2. Effect of dye solution pH The rate of dye solution photo degradation in an aqueous medium is highly sensitive to pH value. Changing the dye solution's medium (pH value) effectively modifies the rate of photo degradation. It results from a shift in how the catalyst and dye interact at various pH levels. The pH was adjusted using 0.1 M HCl and NaOH solutions to pH 6, 8, 10, and 12, with 40 mg of S/N co-doped NiO-NPs catalyst dose and 5ppm MB dye for 60 min. The degradation efficiency of MB dye increased as the pH of the solution rose from 6 to 10, reaching a maximum of 98.9% degradation at pH 10 ( Fig. 3 b ) . This enhanced performance at higher pH values can be attributed to the generation of hydroxyl radicals, which are critical for the photo catalytic degradation of MB dye. The surface of the nanoparticles becomes highly positive in the acidic medium at lower pH values, which repels cationic dye molecules. On the other hand, the catalytic surface becomes negatively charged in the basic medium at higher pH values, which considerably attracts more and more positively charged dye molecules. 30 . Consequently, the rate of photo degradation effectively increased as the pH value rose 31 . However, further increase in pH of the solution to the basic medium reduces photodegradationtion efficiency due to the repulsion of hydroxide ions with the negatively charged photocatalyst surface. 2.5.3. Effect of Photocatalyst Dosages In order to determine the ideal amount of catalyst for the effective photocatalytic degradation of MB dye, visible light was used to illuminate doses containing different concentrations of S/N co-doped NiO-NPs catalyst (20 mg, 30 mg, 40 mg, and 50 mg) with MB dye solutions at an optimum pH (pH = 11) Fig. 3 c. The results, shown in Fig. 3 c, indicate that as the catalyst dosage increases, the degradation efficiency rises due to the greater number of active sites available for the generation of hydroxyl radicals. However, at higher dosages (beyond 40 mg), the degradation efficiency levels off, as the increased viscosity of the suspension impedes light penetration, thereby reducing photo catalytic activity. Therefore, 40 mg of catalyst was found to be optimal for 5 ppm MB dye degradation 32 . As the dosage of S/N co-doped NiO-NPs was raised from 20 mg to 40 mg, the degradation rate of MB increased from 82.50–98.90%. Nevertheless after 40 mg, MB degradation did not considerably increase with dosage increases. Consequently, it was found that the photo catalytic degradation of 5ppm MB was best achieved with 40 mg a catalyst dosage. 2.5.4. Effect of Contact Time The effects of contact time on the photodegradation of MB have been studied in the presence of S/N co-doped NiO-NPs under visible light Fig. 3 d. The results showed that the degradation efficiency increased as time increased. This can be explained by the increase in dye molecules interaction with the surface of the photocatalyst. The maximum degradation efficiency was observed at 60 min, showing negligible degradation efficiency afterwards. Hence 60 min was considered in the follow up experiments. The enhancement of the photocatalytic activity for MB degradation could be attributed to the large specific surface area of S/N co-doped NiO-NPs. 2.5.5. Comparisons of degradation efficiency of MB dye with and without Catalyst The photocatalytic properties of the prepared NiO nanoparticles and S/N co-doped NiO-NPs were investigated by decomposing MB. The effect of irradiation time on the degradation of MB dye was examined using UV-Vis absorbance spectra, and the absorbance was used to quantify the degradation percentage. A beaker containing 100 mL of 5 ppm MB dye at pH 10 was filled with 40 mg of each photocatalyst. The mixture was then continuously stirred and subjected to light for 0, 10, 20, 30, 40, 50, and 60 min. Following string, three distinct systems were exposed to light: pure MB, NiO-NPs containing and S/N co-doped NiO-NPs containing MB. Every 10 min, the UV–Vis absorption of each system was recorded. The UV–Vis absorption spectra of the MB degradation kinetics are displayed in Fig. 4 . After being exposed to light, the absorbance peaks for the MB containing pure NiO-NPs gradually dropped ( Fig. 4 b ) . The MB sample containing S/N co-doped NiO-NPs showed a sharp decline in peak intensity from the UV-Vis measurement, reaching nearly zero after 60 min of light irradiation ( Fig. 4 c ) . After 60 min of light irradiation, the solution's color likewise faded and turned colorless following the absorbance peak intensity drop. Within 60 min of contact time, 98.9% of the MB dye was destroyed, indicating that the nanocomposite had reached its maximal degradation efficiency. In contrast, after 60 min of light irradiation, peak intensities were nearly preserved in MB that did not have a catalyst. The lack of noticeable MB degradation in the absence of photocatalysts (blank test) under light irradiation suggests that MB resists photo degradation and that its self-degradation contribution is negligible ( Fig. 4 a ). Because of its high-energy band gap, NiO-NPs exhibit a sluggish photocatalytic behavior in visible light, which was also responsible for the modest degradation of MB in pure NiO-NPs. The Summary of the comparison of the current work and previously published works are summarized in Table-3 .Thus, the photocatalytic degradation efficiency and rate of this work is by far better than most of the published works on the area. The addition of S/N co-doping are crucial steps in enhancing the photocatalytic behavior of NiO-NPs by shifting the energy band gap toward the red 33 , 34 . Table 3 Comparison among the photocatalytic efficiency of various photocatalysts for photo degradation of MB dye Catalyst Source of light Dye Time(min) Degradation (%) References Cu-doped NiO-NPs Visible light MB 60 89.0 35 Mn-doped NiO NPs Uv-light MB 210 92.0 36 Cu-doped NiO-NPs Uv-light MB 103 78.0 35 S/N co-doped NiO-NPs Visible light MB 60 98.9 This Work By analyzing the 3-cycles degradation of MB, the recyclability of S/N co-doped NiO-NPs for dye degradation was established. Every cycle, the photocatalyst was cleaned with ethanol and then utilized again. The number of cycles the S/N co-doped NiO-NPs photocatalyst can be utilized was displayed in Fig. 5 . It was tested for reusability using the same optimal operating parameters as the S/N co-doped NiO-NPs. Degradation efficiency was 98.90%, 93.53%, and 89.92% for the first three cycles, respectively, with an initial dye concentration of 5 ppm, a catalyst dose of 40 mg, a pH of 10, and an irradiation time of 60 min. In the second and third cycles, the photocatalytic degradation efficiency of S/N co-doped NiO-NPs declines, possibly as a result of waste ion accumulation and catalyst dosage that produces contaminants. With a minor reduction in efficiency, our experiment demonstrates that the synthesized S/N co-doped NiO-NPs photocatalyst may be recycled for three more cycles. S/N co-doped NiO-NPs function as a highly effective and stable photocatalyst. 2.6. Antibacterial activity test In order to examine the antibacterial activity of synthesized NiO-NPs and S/N co-doped NiO-NPs, the disk diffusion method was used against Gram-positive and Gram-negative bacterial strains. Gentamicin and DMSO were used as positive and negative controls, respectively. The antibacterial activities of 25, 50, 75 and 100 mg/mL of synthesized NPs were tested against S. aureus, E. coli, B. cereus, and S. typhi 37 . The results of the study showed that gram-positive bacteria, such as S. aureus and B. cereus, were more inhibited by the synthesized S/N co-doped NiO-NCs than gram-negative strains like E. coli and S. typhi. Additionally, the nickel ions released from the NPs could bind to the negatively charged bacterial cell wall, causing it to disrupted, leading to protein denaturation and cell death. Small-sized NPs have high penetration ability and cause rapid cell damage compared to other bulk compounds 38 . The co-doped nanoparticles antibacterial activity was superior to that of pure NiO-NPs, indicating that the introduction of S/N co-doping improved the NPs antimicrobial activity. The inhibition zones of antimicrobial measurements are given in Table 4 . The antibacterial activity increased with concentration of synthesized NPs, with a significant inhibition zone which ascribed the stronger antibacterial activities of synthesized NPs. As shown in Table 4 and Fig. 6 , the S/N co-doped NiO-NPs demonstrated stronger antibacterial activity against S. aureus (17 mm) than against E. coli (14 mm) but NiO-NPs shows insignificant inhibition zone for all bacteria strain when compared to S/N co-doped NiO-NPs. The antibacterial effect is attributed to the increased surface area and smaller crystallite size of the nanoparticles, which facilitate the generation of reactive oxygen species (ROS) that disrupt bacterial cell membranes and inhibit bacterial growth 39 .The antibacterial activity of S/N co-doped NiO-NPs against Gram-positive bacteria (S. aureus and B. cereus) is significantly higher than for Gram-negative bacteria (E. coli and S. typhi). The study highlights that S/N co-doping enhances the antibacterial properties, suggesting that the nanoparticles release reactive oxygen species (ROS), which disrupt bacterial membranes 40 .This finding is in line with previous research showing that the antibacterial properties of NiO can be enhanced through doping, but this study provides comparative data showing the superiority of the S/N co-doping strategy 30 . Table 4 Antibacterial Activity of NiO-NPs and S/N-NiO-NCs Inhibition zones (mm Bacterial strain Controls Target materials (100 mg/mL) Gentamicin (+ ve) DMSO (-ve) NiO-NPs S/N co-doped-NiO-NPs B.cereus 26 0 5 13 E.coli 27 0 6 14 S.typhi 27 0 7 15 S.ureus 29 0 10 17 3. Conclusions The co-precipitation method was successfully employed to synthesize both pure NiO and S/N co-doped NiO-NPs. The optical properties of the nanoparticles were characterized using a UV-Vis spectrometer. The pure NiO nanoparticles exhibited an absorbance peak at 303 nm, indicating a blue shift. In contrast, the S/N co-doped NiO nanoparticles showed an absorbance peak at 329 nm, indicating a red shift. The incorporation of 4% sulfur and 6% nitrogen into the NiO lattice reduced the band gap from 3.75 eV (for pure NiO) to 2.74 eV (for S/N co-doped NiO). XRD analysis confirmed the formation of a crystalline FCC structure for the NiO nanoparticles, with no additional peaks corresponding to the S/N dopants, indicating successful doping. XRD studies showed the purity and crystalline structure of NiO-NPs and S/N-NiO-NPs with crystallite sizes of 20.49 and 17.89 nm respectively. The morphology of the synthesized nanoparticles was analyzed using SEM. The FT-IR spectra revealed the characteristic Ni-O stretching vibration at 825 and 594 cm⁻¹ for pure NiO-NPs and at 825 and 575 cm − ¹ for the S/N co-doped NiO-NPs, confirming the presence of Ni-O bonds. In Photocatalysis degradation tests, methylene blue 5ppm MB dye was almost completely degraded (98.9%) within 60 minutes at an optimal pH of 10 and a catalyst dose of 40 mg of S/N co-doped NiO-NPs. Importantly, the Photocatalysis activity of the material remained stable across at least three consecutive reaction cycles, demonstrating its potential for sustained performance in environmental applications. Antibacterial activity, assessed through inhibition zone measurements, showed significant improvement: NiO-NPs exhibited zones of 5–10 mm, while S/N-NiO-NPs achieved 13–17 mm against Bacillus cereus, Escherichia coli, Salmonella typhi, and Staphylococcus aureus. These suggest that the antibacterial activity of S/N co-doped NiO-NPs against Gram-positive bacteria (S. aureus, B. cereus) is significantly higher than for Gram-negative bacteria (E. coli, S. typhi). Declarations Conflict of Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Author Contribution Tariku Tamesgen, Zhu Kai, and Tamene Tadesse Beyene conception of the idea. Tariku Tamesgen, Michael Asfaw Ameya, Getu Sisay, and Lu Yuanqi underwent the experiment, analysed data, and wrote the draft. Zhu Kai and Tamene Tadesse Beyene supervised the work, revised the drafted manuscript Acknowledgement This work was financially supported by the College of Natural Sciences at Jimma University under the PG student project References Góralczyk-Bińkowska, A.; Długoński, A.; Bernat, P.; Długoński, J.; Jasińska, A. Environmental and Molecular Approach to Dye Industry Waste Degradation by the Ascomycete Fungus Nectriella Pironii. Sci Rep 2021 , 11 (1), 1–13. https://doi.org/10.1038/s41598-021-03446-x. Ishak, S. A.; Murshed, M. F.; Akil, H. M.; Ismail, N.; Md Rasib, S. Z.; Al-Gheethi, A. A. S. The Application of Modified Natural Polymers in Toxicant Dye Compounds Wastewater: A Review. Water (Switzerland) 2020 , 12 (7). https://doi.org/10.3390/w12072032. Liu, T.; Jiang, C.; Zhu, L.; Jiang, L.; Huang, H. Fe3O4@chitosan Microspheres Coating as Cytoprotective Exoskeletons for the Enhanced Production of Butyric Acid With Clostridium Tyrobutyricum Under Acid Stress. Front Bioeng Biotechnol 2020 , 8 (May), 1–13. https://doi.org/10.3389/fbioe.2020.00449. Hasanpour, M.; Hatami, M. Photocatalytic Performance of Aerogels for Organic Dyes Removal from Wastewaters: Review Study ; Elsevier B.V, 2020; Vol. 309. https://doi.org/10.1016/j.molliq.2020.113094. Iyyappan, J.; Gaddala, B.; Gnanasekaran, R.; Gopinath, M.; Yuvaraj, D.; Kumar, V. Critical Review on Wastewater Treatment Using Photo Catalytic Advanced Oxidation Process: Role of Photocatalytic Materials, Reactor Design and Kinetics. Case Stud Chem Environ Eng 2024 , 9 (November 2023), 100599. https://doi.org/10.1016/j.cscee.2023.100599. Ghamarpoor, R.; Fallah, A.; Jamshidi, M. A Review of Synthesis Methods, Modifications, and Mechanisms of ZnO/TiO2-Based Photocatalysts for Photodegradation of Contaminants. ACS Omega 2024 , 9 (24), 25457–25492. https://doi.org/10.1021/acsomega.3c08717. Sanghavi, L.; Sanghavi, L. K.; Shashi, D. R.; Ranga, V. Study of Operating Parameters for Removal of Direct Yellow 12 Dye Using Prosopis Juliflora Bark Wastewater Treatment Using Low Cost Adsorbent View Project Study of Operating Parameters for Removal of Direct Yellow 12 Dye Using Prosopis Juliflora Bark. IJRAR19K2418 Int J Res Anal Rev (IJRAR)wwwijrarorg 2019 , 869 (May). https://doi.org/10.13140/RG.2.2.10937.01122. Tang, K. W. K.; Millar, B. C.; Moore, J. E. Antimicrobial Resistance (AMR). Br J Biomed Sci 2023 , 80 (June), 1–11. https://doi.org/10.3389/bjbs.2023.11387. Ghirardello, M.; Ramos-Soriano, J.; Galan, M. C. Carbon Dots as an Emergent Class of Antimicrobial Agents. Nanomaterials 2021 , 11 (8), 1–24. https://doi.org/10.3390/nano11081877. Li, H.; Huang, J.; Song, Y.; Zhang, M.; Wang, H.; Lu, F.; Huang, H.; Liu, Y.; Dai, X.; Gu, Z.; Yang, Z.; Zhou, R.; Kang, Z. Degradable Carbon Dots with Broad-Spectrum Antibacterial Activity. ACS Appl Mater Interfaces 2018 , 10 (32), 26936–26946. https://doi.org/10.1021/acsami.8b08832. Ijaz, I.; Gilani, E.; Nazir, A.; Bukhari, A. Green Chemistry Letters and Reviews Detail Review on Chemical , Physical and Green Synthesis , Classification , Characterizations and Applications of Nanoparticles. 2020 . https://doi.org/10.1080/17518253.2020.1802517. Haider, A.; Ijaz, M.; Ali, S.; Haider, J.; Imran, M.; Majeed, H.; Shahzadi, I.; Ali, M. M.; Khan, J. A.; Ikram, M. Green Synthesized Phytochemically (Zingiber Officinale and Allium Sativum) Reduced Nickel Oxide Nanoparticles Confirmed Bactericidal and Catalytic Potential. Nanoscale Res Lett 2020 , 15 (1). https://doi.org/10.1186/s11671-020-3283-5. Erjeno, D. J. D.; Asequia, D. M. A.; Osorio, C. K. F.; Omisol, C. J. M.; Etom, A. E.; Hisona, R. M. R.; Tilendo, A. C.; Triana, A. P. G.; Dumancas, G. G.; Zoleta, J. B.; Alguno, A. C.; Malaluan, R. M.; Lubguban, A. A. Facile Synthesis of Band Gap-Tunable Kappa-Carrageenan-Mediated C,S-Doped TiO2 Nanoparticles for Enhanced Dye Degradation. ACS Omega 2024 , 9 (19), 21245–21259. https://doi.org/10.1021/acsomega.4c01370. Al-Shawi, S. G.; Alekhina, N. A.; Aravindhan, S.; Thangavelu, L.; Kartamyshev, N. V.; Zakieva, R. R. Synthesis of NiO Nanoparticles and Sulfur, and Nitrogen Co Doped-Graphene Quantum Dots/ NiO Nanocomposites for Antibacterial Application. J Nanostructures 2021 , 11 (1), 181–188. https://doi.org/10.22052/JNS.2021.01.019. Minisha, S.; Johnson, J.; Mohammad Wabaidur, S.; Gupta, J. K.; Aftab, S.; Siddiqui, M. R.; Lai, W. C. Synthesis and Characterizations of Fe-Doped NiO Nanoparticles and Their Potential Photocatalytic Dye Degradation Activities. Sustain 2023 , 15 (19). https://doi.org/10.3390/su151914552. Sandeep, S.; Koteswara Rao, C.; Vijay Rajesh, A.; Sruthi, T.; Prakash, D. S. Studies on Characterization and Optimization Parameters of Zinc Oxide Nanoparticles Synthesis. Int J Curr Res Rev 2022 , 14 (03), 06–11. https://doi.org/10.31782/ijcrr.2022.14302. Agale, A. A.; Gaikwad, S. T.; Rajbhoj, A. S. Nanosized Synthesis of Nickel Oxide by Electrochemical Reduction Method and Their Antifungal Screening. J Clust Sci 2017 , 28 (4), 2097–2109. https://doi.org/10.1007/s10876-017-1203-3. Morgan, R. N.; Aboshanab, K. M. Green Biologically Synthesized Metal Nanoparticles: Biological Applications, Optimizations and Future Prospects. Futur Sci OA 2024 , 10 (1). https://doi.org/10.2144/fsoa-2023-0196. Nouren, S.; Bibi, I.; Kausar, A.; Sultan, M.; Nawaz Bhatti, H.; Safa, Y.; Sadaf, S.; Alwadai, N.; Iqbal, M. Green Synthesis of CuO Nanoparticles Using Jasmin Sambac Extract: Conditions Optimization and Photocatalytic Degradation of Methylene Blue Dye. J King Saud Univ - Sci 2024 , 36 (3), 103089. https://doi.org/10.1016/j.jksus.2024.103089. Khairunnisa, S.; Wonoputri, V.; Samadhi, T. W. Effective Deagglomeration in Biosynthesized Nanoparticles: A Mini Review. IOP Conf Ser Mater Sci Eng 2021 , 1143 (1), 012006. https://doi.org/10.1088/1757-899x/1143/1/012006. Firisa, S. G.; Muleta, G. G.; Yimer, A. A. Synthesis of Nickel Oxide Nanoparticles and Copper-Doped Nickel Oxide Nanocomposites Using Phytolacca Dodecandra L’Herit Leaf Extract and Evaluation of Its Antioxidant and Photocatalytic Activities. ACS Omega 2022 , 7 (49), 44720–44732. https://doi.org/10.1021/acsomega.2c04042. Venkatachalapathy, M.; Sambathkumar, K.; Kamal, N. R. Synthesis and Characterization of Structural and Magnetic Properties of Fe Doped NiO Nanoparticles. Dig J Nanomater Biostructures 2024 , 19 (1), 451–458. https://doi.org/10.15251/DJNB.2024.191.451. Chattopadhyay, J.; Pathak, T. S.; Pak, D. Heteroatom-Doped Metal-Free Carbon Nanomaterials As. Molecules 2022 , 27 , 670. Chakravorty, A.; Roy, S. A Review of Photocatalysis, Basic Principles, Processes, and Materials. Sustain Chem Environ 2024 , 8 (September), 100155. https://doi.org/10.1016/j.scenv.2024.100155. Ponnusamy, P. M.; Agilan, S.; Muthukumarasamy, N.; Velauthapillai, D. Effect of Chromium and Cobalt Addition on Structural, Optical and Magnetic Properties of NiO Nanoparticles. Zeitschrift fur Phys Chemie 2016 , 230 (8), 1185–1197. https://doi.org/10.1515/zpch-2015-0678. Atul, A. K.; Srivastava, S. K.; Gupta, A. K.; Srivastava, N. Synthesis and Characterization of NiO Nanoparticles by Chemical Co-Precipitation Method: An Easy and Cost-Effective Approach. Brazilian J Phys 2022 , 52 (1), 2–7. https://doi.org/10.1007/s13538-021-01006-2. Alam, M. W.; BaQais, A.; Mir, T. A.; Nahvi, I.; Zaidi, N.; Yasin, A. Effect of Mo Doping in NiO Nanoparticles for Structural Modification and Its Efficiency for Antioxidant, Antibacterial Applications. Sci Rep 2023 , 13 (1), 1–18. https://doi.org/10.1038/s41598-023-28356-y. Ramesh, M. N and Fe Doped NiO Nanoparticles for Enhanced Photocatalytic Degradation of Azo Dye Methylene Blue in the Presence of Visible Light. SN Appl Sci 2021 , 3 (10). https://doi.org/10.1007/s42452-021-04803-1. Khan, S.; Noor, T.; Iqbal, N.; Yaqoob, L. Photocatalytic Dye Degradation from Textile Wastewater: A Review. ACS Omega 2024 , 9 (20), 21751–21767. https://doi.org/10.1021/acsomega.4c00887. Tegenaw, A. B.; Yimer, A. A.; Beyene, T. T. Boosting the Photocatalytic Activity of ZnO-NPs through the Incorporation of C-Dot and Preparation of Nanocomposite Materials. Heliyon 2023 , 9 (10), e20717. https://doi.org/10.1016/j.heliyon.2023.e20717. Kumari, V.; Yadav, S.; Jindal, J.; Sharma, S.; Kumari, K.; Kumar, N. Synthesis and Characterization of Heterogeneous ZnO/CuO Hierarchical Nanostructures for Photocatalytic Degradation of Organic Pollutant. Adv Powder Technol 2020 , 31 (7), 2658–2668. https://doi.org/10.1016/j.apt.2020.04.033. Andrade, P. F.; Nakazato, G.; Durán, N. Additive Interaction of Carbon Dots Extracted from Soluble Coffee and Biogenic Silver Nanoparticles against Bacteria. J Phys Conf Ser 2017 , 838 (1). https://doi.org/10.1088/1742-6596/838/1/012028. Anju Chanu, L.; Joychandra Singh, W.; Jugeshwar Singh, K.; Nomita Devi, K. Effect of Operational Parameters on the Photocatalytic Degradation of Methylene Blue Dye Solution Using Manganese Doped ZnO Nanoparticles. Results Phys 2019 , 12 (December 2018), 1230–1237. https://doi.org/10.1016/j.rinp.2018.12.089. Sahu, K.; Bisht, A.; Kuriakose, S.; Mohapatra, S. Two-Dimensional CuO-ZnO Nanohybrids with Enhanced Photocatalytic Performance for Removal of Pollutants. J Phys Chem Solids 2020 , 137 , 109223. https://doi.org/10.1016/j.jpcs.2019.109223. Padma; Ranju, S.; Yeshas; Kavya, S. L.; Sukrutha, S. K.; Kumar, M. R. A.; Kumar, A. N.; Kumaraswamy, M.; Purushotham, B.; Boppana, S. B. A Comparative Study of Green and Chemically Synthesized Nano Nickel Oxide for Multifunctional Applications. Appl Surf Sci Adv 2022 , 12 (October), 100318. https://doi.org/10.1016/j.apsadv.2022.100318. Islam, R.; Abdur, R.; Alam, M. A.; Munna, N.; Ahmed, A. N.; Hossain, M.; Bashar, M. S.; Islam, D.; Jamal, M. S. Modulating Mn-Doped NiO Nanoparticles: Structural, Optical, and Electrical Property Tailoring for Enhanced Hole Transport Layers. Nanoscale Adv 2024 . https://doi.org/10.1039/d4na00708e. Ilbeigi, G.; Kariminik, A.; Moshafi, M. H. The Antibacterial Activities of NiO Nanoparticles Against Some Gram-Positive and Gram-Negative Bacterial Strains. Int J Basic Sci Med 2019 , 4 (2), 69–74. https://doi.org/10.15171/ijbsm.2019.14. Ozdal, M.; Gurkok, S. Recent Advances in Nanoparticles as Antibacterial Agent. ADMET DMPK 2022 , 10 (2), 115–129. https://doi.org/10.5599/admet.1172. Ali, A. Y.; Alani, A. A. K.; Ahmed, B. O.; Hamid, L. L. Effect of Biosynthesized Silver Nanoparticle Size on Antibacterial and Anti-Biofilm Activity against Pathogenic Multi-Drug Resistant Bacteria. OpenNano 2024 , 20 (July), 100213. https://doi.org/10.1016/j.onano.2024.100213. Mahmoudi Khatir, N.; Khorsand Zak, A. Antibacterial Activity and Structural Properties of Gelatin-Based Sol-Gel Synthesized Cu-Doped ZnO Nanoparticles; Promising Material for Biomedical Applications. Heliyon 2024 , 10 (17), e37022. https://doi.org/10.1016/j.heliyon.2024.e37022. Additional Declarations No competing interests reported. Supplementary Files TarikuSI.docx 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-6493877","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":448832833,"identity":"294b0d52-9e56-4eee-8a1b-a155c0f2e55f","order_by":0,"name":"Tariku Tamesgen","email":"","orcid":"","institution":"Jimma University","correspondingAuthor":false,"prefix":"","firstName":"Tariku","middleName":"","lastName":"Tamesgen","suffix":""},{"id":448832834,"identity":"75f5c25a-c8ec-40bd-b398-ee581d60950c","order_by":1,"name":"Michael Asfaw Ameya","email":"","orcid":"","institution":"Jimma University","correspondingAuthor":false,"prefix":"","firstName":"Michael","middleName":"Asfaw","lastName":"Ameya","suffix":""},{"id":448832835,"identity":"f4ca685f-6ac3-46ab-9151-a8b878c9570d","order_by":2,"name":"Getu Sisay","email":"","orcid":"","institution":"Jimma University","correspondingAuthor":false,"prefix":"","firstName":"Getu","middleName":"","lastName":"Sisay","suffix":""},{"id":448832836,"identity":"2d17b326-3126-4f04-9a34-b4e4633097c5","order_by":3,"name":"Lu Yuanqi","email":"","orcid":"","institution":"Harbin Engineering University","correspondingAuthor":false,"prefix":"","firstName":"Lu","middleName":"","lastName":"Yuanqi","suffix":""},{"id":448832837,"identity":"5f86f403-a2da-473d-a7e3-fb16ea4226ec","order_by":4,"name":"Zhu Kai","email":"","orcid":"","institution":"Harbin Engineering University","correspondingAuthor":false,"prefix":"","firstName":"Zhu","middleName":"","lastName":"Kai","suffix":""},{"id":448832838,"identity":"76655d04-fef9-46d4-9b0f-befa6decf13f","order_by":5,"name":"Tamene Tadesse Beyene","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAABB0lEQVRIiWNgGAWjYHCDBBBhwwwiJfCp44HSElAtaXAtOLWhazkM4+HWYs9+OvFxQQVDHX978uGPPyrOsxscYD54m4fBpg6nLTy5m41nnGGQkDjzLE2a58xtZoMDbMnWPAxpeByWu02atw3ojBs5ZsyMbSAtPGbSPAyHcWvhf7v9N+8/Bgn5G/mfP/78dw6ohf8bUMt/3Fokcrcx8zYwSBjcyGGQ4G04ALKFDajlAG4tN95uluY5JiG58cwzoHuOJTNLHmYztpxjkCzZgEMLe3/uxs88NTb8cseTH3/8UWOXzHe8+eGNNxV2/LhsgQKEK5IZwJFpQEADMrAjQe0oGAWjYBSMEAAAxcRMS7CpP9oAAAAASUVORK5CYII=","orcid":"","institution":"Jimma University","correspondingAuthor":true,"prefix":"","firstName":"Tamene","middleName":"Tadesse","lastName":"Beyene","suffix":""}],"badges":[],"createdAt":"2025-04-21 08:08:22","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6493877/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6493877/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":81645291,"identity":"635bea71-0dbb-42a9-a2b5-3618100a79da","added_by":"auto","created_at":"2025-04-29 14:26:05","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":142264,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003eUV-Vis spectrum of (a) NiO-NPs (Black), S-doped NiO-NPs (Red), N-doped NiO-NPs (Blue) S/N co-doped NiO-NPs (green), and Energy band gaps of (b) NiO-NPs (c) S-doped NiO-NPs, (d) N-doped NiO-NPs and (e) S/N co-doped NiO-NPs\u003c/em\u003e\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-6493877/v1/c3a72bb01f6819587b893db3.png"},{"id":81643466,"identity":"ca554d3a-0da2-4804-ba16-59805d523bb2","added_by":"auto","created_at":"2025-04-29 14:02:05","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":218434,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003eCharacterizations result of (a) XRD patterns (b) FTIR spectrum and (c-d) SEM images of pure NiO-NPs and S/N co-doped NiO-NPs respectively\u003c/em\u003e.\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-6493877/v1/376f3bdd2287feac5018fdcb.png"},{"id":81643465,"identity":"82f1efcc-abc0-4fdc-a9c7-4612c10e3430","added_by":"auto","created_at":"2025-04-29 14:02:05","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":129738,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003eDegradation efficiency of MB on the different parameters (a) Initial concentration of MB dye (b) pH value of solution (c) Catalyst dosage under sunlight and (c) effects of irradiation time\u003c/em\u003e\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-6493877/v1/21d24294d98155397e9cf477.png"},{"id":81644232,"identity":"84e0126c-7902-4f94-a276-1ae1478f1c17","added_by":"auto","created_at":"2025-04-29 14:10:05","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":162096,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003eUV–Visible absorption spectrum for photo degradation kinetics of MB dyes on photocatalysis under sunlight irradiation, (a) photolysis of MB (b) NiO-NPs (c) S/N co-doped NiO-NPs and (d) type of nanoparticles on photo degradation of MB dye\u003c/em\u003e\u003c/p\u003e","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-6493877/v1/d4bcde03c12aa0e6822fcf21.png"},{"id":81643480,"identity":"fe36d840-2a72-4619-abea-23daaf4d320f","added_by":"auto","created_at":"2025-04-29 14:02:05","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":62003,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003eReusability of \u003c/em\u003eS/N co-doped NiO-NPs \u003cem\u003eusing the same optimal operating parameters as I did for the \u003c/em\u003eS/N co-doped NiO-NPs \u003cem\u003ein this experiment, (an initial dye concentration of 5 ppm, a catalyst dose of 40 mg, at a pH of 10, and a 60-min irradiation period)\u003c/em\u003e\u003c/p\u003e","description":"","filename":"floatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-6493877/v1/af13f218540a876acc5ef39e.png"},{"id":81643469,"identity":"ac077fb5-d84d-47aa-9d56-9993d78e1bd5","added_by":"auto","created_at":"2025-04-29 14:02:05","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":153897,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003eAntibacterial activity of NiO-NPs and S/N co-doped NiO-NPs on a) B. cereus (b) E.coli (c) S. Typhi (d) S.aureus.\u003c/em\u003e\u003c/p\u003e","description":"","filename":"floatimage6.png","url":"https://assets-eu.researchsquare.com/files/rs-6493877/v1/91dcab960416ad0c552c50ff.png"},{"id":81744825,"identity":"a0dfcab2-979d-4b23-8a3d-ee3c471ba379","added_by":"auto","created_at":"2025-05-01 03:31:23","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2066712,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6493877/v1/cc46d790-b875-4802-90f5-95f4dae57afc.pdf"},{"id":81644606,"identity":"1ab10ce6-5c42-4562-a5df-9ad01314c7a6","added_by":"auto","created_at":"2025-04-29 14:18:05","extension":"docx","order_by":0,"title":"","display":"","copyAsset":false,"role":"supplement","size":234393,"visible":true,"origin":"","legend":"","description":"","filename":"TarikuSI.docx","url":"https://assets-eu.researchsquare.com/files/rs-6493877/v1/8bfdc54911cd8474d0efbeab.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Harnessing the Power of S/N Doped NiO Nanoparticles: Bandgap Tuning for Superior Photocatalytic and Antibacterial Performance","fulltext":[{"header":"1. INTRODUCTION","content":"\u003cp\u003eEnvironmental pollution; especially water pollution from industrial dye effluents; has become a pressing global issue. Industries such as textiles, mining, paper production, food processing, pharmaceuticals, and leather manufacturing are major contributors, releasing large volumes of organic dyes that severely contaminate water sources \u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e. Due to their non-biodegradable nature, toxicity, carcinogenic potential, and tendency to bioaccumulate, these dyes pose serious threats to both aquatic ecosystems and human health. In response, various treatment methods; such as ion exchange \u003csup\u003e\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e, adsorption \u003csup\u003e\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u003c/sup\u003e, electrochemical treatment, and photocatalytic degradation \u003csup\u003e\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u003c/sup\u003e have been explored. Among the available methods, photocatalysis stands out as the most effective for real-world applications, offering a clean solution that breaks down pollutants without producing harmful byproducts or secondary waste \u003csup\u003e\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u003c/sup\u003e. This process not only degrades complex organic dyes but also offers an environmentally friendly alternative to other methods, thanks to its high efficiency and relatively low costs \u003csup\u003e\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eThe growing threat of multidrug-resistant (MDR) bacteria is another critical global health challenge. Overuse and misuse of traditional antibiotics have fueled the rise of resistant pathogens, leading to a surge in hard-to-treat infections caused by bacteria, viruses, fungi, and parasites \u003csup\u003e\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u003c/sup\u003e. While antibiotics revolutionized medicine in the 20th century \u003csup\u003e\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u003c/sup\u003e, the need for new treatments to combat antibiotic resistance is more urgent than ever. In response, nanotechnology has introduced innovative approaches, such as nanoparticles doped with specific elements, to tackle this growing problem \u003csup\u003e\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u003c/sup\u003e. Nanoparticles, due to their large surface-to-volume ratio and unique physicochemical properties, hold significant promise in fields like antimicrobial therapy and photo catalysis. Metal oxide nanoparticles, particularly those doped with metals or non-metals, have shown enhanced photocatalytic and antibacterial properties \u003csup\u003e\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u003c/sup\u003e. In the case of photocatalysis, metal oxide catalysts like NiO have demonstrated considerable efficacy in degrading organic pollutants. However, their performance is often limited by issues such as high electron-hole recombination rates and large energy band gaps \u003csup\u003e\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eTo address the aforementioned limitations, doping NiO with elements such as sulfur (S) and nitrogen (N) were explored. These dopants reduce the band gap, increase the dissociation of photo-generated electron-hole pairs, and improve the catalyst's absorption in the visible light range, thereby enhancing photo catalytic and antibacterial activities. NiO-NPs, when doped with sulfur and nitrogen, have shown promising results in overcoming the challenges of pure NiO-NPs \u003csup\u003e\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u003c/sup\u003e. The motivation for synthesizing S/N co-doped NiO nanoparticles (S/N co-doped NiO-NPs) for antibacterial activity and photocatalytic degradation stems from the unique properties of NiO, which distinguish it from widely studied materials like S/N co-doped ZnO and carbon quantum dots (CQDots) and the like. NiO, as a p-type semiconductor, demonstrates exceptional stability, resistance to photo corrosion, and robustness under harsh conditions \u003csup\u003e\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eDoping with sulfur and nitrogen effectively narrows its band gap, enhances light absorption in the visible spectrum, and improves charge carrier separation, significantly boosting its photocatalytic and antibacterial efficiency. Research has shown that doped NiO nanoparticles have achieved high performance in various environmental applications. For instance, nitrogen-doped NiO has demonstrated enhanced photocatalytic CO\u003csub\u003e2\u003c/sub\u003e reduction efficiency and improved electron-hole separation capabilities, confirming its potential for light-driven applications under visible light irradiation \u003csup\u003e\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u003c/sup\u003e. Studies on other doped forms of NiO have also highlighted its superior durability and activity compared to other semiconductors, making it a strong candidate for multifunctional applications such as water treatment and microbial inhibition \u003csup\u003e\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e,\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eThis study investigates the impact of sulfur/nitrogen (S/N) co-doping on the energy band gap, photocatalytic degradation efficiency of methylene blue (MB) dye, and antibacterial activity of nickel oxide nanoparticles (NiO-NPs). The nanoparticles were synthesized using a precipitation method, and their structural and optical characteristics were thoroughly examined using FTIR, UV-Vis spectroscopy, SEM, and XRD analyses. UV-Vis results revealed a redshift in the maximum absorbance wavelength upon S/N incorporation, indicating enhanced light absorption. Notably, S/N co-doping reduced the energy band gap of NiO-NPs from 3.75 eV to 2.50 eV, significantly boosting their photocatalytic efficiency. Under optimal conditions (pH 10, 40 mg catalyst dosage), nearly complete degradation of 5 ppm MB dye (98.9%) was achieved within 60 minutes. Furthermore, S/N co-doped NiO-NPs demonstrated markedly improved antibacterial performance compared to their undoped counterparts. These findings highlight the potential of S/N co-doping in enhancing the photocatalytic and antimicrobial properties of NiO-NPs, making them promising candidates for environmental remediation and biomedical applications.\u003c/p\u003e"},{"header":"2. RESULT AND DISCUSSION","content":"\u003cp\u003e \u003cdiv class=\"BlockQuote\"\u003e \u003cp\u003eDetailed descriptions of the materials and experimental procedures used in this study are available in the Supporting Information. A schematic illustration of the synthesis process is presented as \u003cb\u003eFigure \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e\u003c/b\u003e (supplementary information). Additionally, the Supporting Information includes the optimization of key parameters such as concentration, pH, reaction time, and temperature.\u003c/p\u003e \u003c/div\u003e \u003c/p\u003e \u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1. Parameters Optimization for the synthesis of S/N co-doped NiO NPs\u003c/h2\u003e \u003cdiv id=\"Sec4\" class=\"Section3\"\u003e \u003ch2\u003e2.1.1. Parameters Optimization for the synthesis of NiO NPs\u003c/h2\u003e \u003cp\u003eIn this study, an optimization approach for synthesizing NiO NPs with small size and smaller band gap were reported.\u003c/p\u003e \u003cdiv id=\"Sec5\" class=\"Section4\"\u003e \u003ch2\u003e2.1.1.1. Effect of metal ion concentrations on NiO-NPs synthesis\u003c/h2\u003e \u003cp\u003e \u003cdiv class=\"BlockQuote\"\u003e \u003cp\u003eNickel nitrate hexahydrate (Ni(NO₃)₂\u0026middot;6H₂O) was used as a precursor at varying concentrations; 0.05 M, 0.1 M, and 0.15 M (see \u003cb\u003eFigure S2a\u003c/b\u003e); while maintaining consistent reaction parameters, including pH, temperature, and duration. To initiate precipitation, 1 M sodium hydroxide (NaOH) was gradually added until the pH reached 10, with continuous stirring at 600 rpm for 3 h at 60\u0026deg;C. This process produced a slow-forming green precipitate. The resulting mixture was filtered through Whatman No. 1 filter paper, thoroughly washed with ethanol, then oven-dried at 120\u0026deg;C and finally annealed at 400\u0026deg;C to obtain a fine green powder of nickel oxide nanoparticles (NiO-NPs). Notably, increasing the concentration of Ni(NO₃)₂\u0026middot;6H₂O to 0.15 M led to a reduction in peak intensity, suggesting enhanced nucleation and aggregation during nanoparticle formation. Based on these observations, 0.1 M Ni(NO₃)₂\u0026middot;6H₂O was identified as the optimal concentration for synthesizing S/N co-doped NiO-NPs \u003csup\u003e\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section4\"\u003e \u003ch2\u003e2.1.1.2. Effect of pH on synthesis of NiO-NPs\u003c/h2\u003e \u003cp\u003eIn this study, the effect of pH on the formation of NiO-NPs was investigated using UV-Vis spectroscopy. The synthesis was carried out at various pH levels: 6, 8, 10, and 12: to assess how the reaction medium affects nanoparticle production (see Figure S2). At lower, acidic pH values (\u0026lt;\u0026thinsp;7), a broader absorption peak was observed, indicating the formation of relatively larger nanoparticles, with sizes reaching approximately 158 nm. These findings highlight the importance of pH optimization in achieving desired nanoparticle characteristics \u003csup\u003e\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e\u003c/sup\u003e. As the pH increased from 8 to 12, the UV-Vis absorption peaks became sharper and more intense, with the most pronounced peak observed at pH 10; signifying the formation of smaller, well-defined nanoparticles. In contrast, further increasing the pH to 12 resulted in a broader absorption band, indicative of larger particle formation due to aggregation. The distinct blue shift observed at pH 10 confirms a reduction in particle size, marking it as the optimal condition for synthesizing finely tuned NiO nanoparticles \u003csup\u003e\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u003c/sup\u003e. The result revealed that it was unable to function above pH 12 as illustrated in \u003cb\u003eFigure S2b\u003c/b\u003e.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section4\"\u003e \u003ch2\u003e2.1.1.3. Effect of Calcination temperature on Synthesis of NiO-NPs\u003c/h2\u003e \u003cp\u003eTemperature plays a vital role in determining the shape, size, stability, and overall yield of synthesized nanoparticles. While green synthesis methods typically operate at temperatures below 100\u0026deg;C or room temperature, this study explored the influence of higher temperatures ranging from 300\u0026deg;C to 500\u0026deg;C on the formation of NiO-NPs, with all other parameters held constant (\u003cb\u003eFigure S2c\u003c/b\u003e). As the temperature increased, the UV-Vis absorption peaks became progressively sharper, indicating improved crystallinity and size uniformity. Notably, at 400\u0026deg;C, a distinct and narrow peak was observed, suggesting the formation of well-defined, smaller nanoparticles. This improvement can be attributed to enhanced reaction kinetics and increased nucleation at elevated temperatures. However, at 500\u0026deg;C, the absorption peak broadened once again, signaling a wider particle size distribution likely caused by aggregation due to excessive growth rates. Based on these observations, 400\u0026deg;C was identified as the optimal temperature for synthesizing high-quality NiO-NPs \u003csup\u003e\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section4\"\u003e \u003ch2\u003e2.1.1.4. Effect of Stirring time on Synthesis of NiO-NPs\u003c/h2\u003e \u003cp\u003eReaction time is essential for the synthesis and stability of NPs. The effect of reaction time was studied in the synthesis of NiO-NPs. The effect of reaction time was conducted by analysing the sample through the UV-Vis spectrum at every 1 h difference from 2 h to 4 h for the synthesis of NiO NPs (\u003cb\u003eFigure S2d\u003c/b\u003e). NiO-NPs UV-Vis spectrum displayed a small intensity peak at 2 h, and the intensity of the peak increased, and the peak became narrower as the time progressed to 3 h. This indicated an enhanced nucleation rate and the formation of small-sized NPs. By further increasing reaction time, the absorbance peak became broader, which might lead to an increase in particle size. This was caused by overgrowth or aggregation of NPs, affecting their size, distribution, and stability \u003csup\u003e\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u003c/sup\u003e. Accordingly, 3 h was the optimum time for synthesized NiO-NPs.\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003e2.2. Optimization for the synthesis of S/N co-doped NiO-NPs\u003c/h2\u003e \u003cp\u003eThe absorption peak of S/N-NiO nanoparticles (NPs) were influenced by the concentration of the dopant. This study examined the effects of different mass ratios of dopants (mg) for sulfur (S), nitrogen (N), and nickel oxide (NiO) in three combinations: 1:1:20, 2:3:50, and 3:7:100, while keeping other parameters constant. It was noted that increasing the dopant concentration resulted in a redshift of the absorption wavelength, as depicted in \u003cb\u003eFigure S3c\u003c/b\u003e. The optimal results were achieved with a dopant concentration of 4% sulfur and 6% nitrogen, which produced the most significant redshift in the UV-Vis absorbance spectrum, measured at 329 nm.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003e2.3. Characterization\u003c/h2\u003e \u003cp\u003eThe NiO-NPs, N-doped NiO-NPs, S-doped NiO-NPs and S/N co-doped NiO-NPs, produced by the precipitation method, and were characterized using UV-Vis, XRD, FTIR, and SEM.\u003c/p\u003e \u003cp\u003eThe light absorption characteristics of NiO nanoparticles (NiO-NPs), nitrogen-doped NiO-NPs, sulfur-doped NiO-NPs, and nitrogen/sulfur co-doped NiO-NPs were measured using a spectrophotometer. The electronic excitation spectra for pure NiO-NPs, nitrogen-doped NiO-NPs, sulfur-doped NiO-NPs, and co-doped NiO-NPs were recorded in the 280\u0026ndash;600 nm wavelength range. The absorbance peaks were observed at 303 nm for pure NiO-NPs, 307 nm for nitrogen-doped NiO-NPs, 305 nm for sulfur-doped NiO-NPs, and 329 nm for nitrogen/sulfur co-doped NiO-NPs. These peaks indicate that doping with nitrogen and sulfur resulted in a red shift in absorbance. Notably, the nitrogen doping caused a slightly more significant red shift compared to sulfur, highlighting its stronger impact on the electronic properties of the material. The absorbance of the co-doped NiO-NPs at 329 nm demonstrates a noticeable shift toward a longer wavelength, signifying that the doping has modified the material's electronic structure\u003csup\u003e\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e\u003c/sup\u003e, indicating that doping has altered the electronic structure of the material. The optical band gap of the synthesized samples was calculated using the Tauc equation, as illustrated in \u003cb\u003eEq.\u0026nbsp;1.\u003c/b\u003e\u003c/p\u003e \u003cp\u003e(\u003cb\u003eαhν) = A (hν-Eg)\u003c/b\u003e \u003csup\u003e\u003cb\u003en\u003c/b\u003e\u003c/sup\u003e\u003cb\u003e\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;1\u003c/b\u003e\u003c/p\u003e \u003cp\u003eWhere Eg is the optical band gap, h is Planck's constant, A is constant, and α is the absorption coefficient. The direct energy band gap was determined as depicted in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e\u003cb\u003e(b to e).\u003c/b\u003e The optical band gap values for NiO, N-doped NiO, S-doped NiO, and S/N co-doped NiO-NPs were found to be 3.75 eV, 3.2 eV, 3.45 eV, and 2.50 eV, respectively. These results suggest that doping with nitrogen and sulfur reduces the band gap of NiO. Specifically, the S/N co-doped NiO nanoparticles exhibit the smallest band gap (2.50 eV), which can be attributed to lattice contraction and the creation of vacancies and energy states due to the incorporation of nonmetal dopants like S and N \u003csup\u003e\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u003c/sup\u003e. This reduction in the band gap facilitates the absorption of light across a wider range of the spectrum, including visible light, which is a critical factor for enhancing the photo catalytic activity of the material \u003csup\u003e\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e\u003c/sup\u003e. In summary, doping NiO with sulfur and nitrogen not only reduces the band gap but also improves the material's ability to absorb visible light, making it more effective for applications such as photo catalysis, antibacterial treatment, and dye degradation. The summarized optical properties and calculated band gaps of the materials are given in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eOptical properties of the prepared materials.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"3\"\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=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTypes of Nanomaterials\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMaximum Absorbance(nm)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eCalculated band gap energy(eV)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNiO-NPs\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e303\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e3.75\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eN-doped NiO-NPs\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e307\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e3.2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eS-doped NiO-NPs\u003c/p\u003e \u003cp\u003eS/N co-doped NiO-NPs\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e305\u003c/p\u003e \u003cp\u003e329\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e3.45\u003c/p\u003e \u003cp\u003e2.50\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\u003e \u003c/p\u003e \u003cp\u003eTo verify the crystallinity of the nanoparticles and to evaluate the effect of C-dot inclusion on their crystalline structure, we measured and presented the X-ray diffraction (XRD) patterns of pure NiO nanoparticles and S/N co-doped NiO nanoparticles, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea. The XRD analysis revealed diffraction peaks at 2θ values of 37.58\u0026deg;, 43.54\u0026deg;, 63.09\u0026deg;, 75.68\u0026deg;, and 79.64\u0026deg; for NiO nanoparticles, which correspond to the diffraction planes (111), (200), (202), (311), and (222) of the face-centered cubic (FCC) structure of NiO. These peaks align well with the standard JCPDS card (JCPDS #96-101-0096), confirming that NiO adopts the FCC structure. The sharpness of these peaks indicates high crystallinity. Additionally, we observed a weak peak at 39.6\u0026deg; in the XRD pattern of NiO, which is attributed to a minor impurity of metallic nickel. This suggests that some reduction of Ni\u0026sup2;⁺ to Ni occurred during the synthesis process; however, this impurity is relatively minor, as it is only visible as a weak peak in the pattern.\u003c/p\u003e \u003cp\u003eFor the S/N co-doped NiO-NCs, the same diffraction peaks at 37.36\u0026deg;, 43.4\u0026deg;, 63.04\u0026deg;, 75.56\u0026deg;, and 79.58\u0026deg; are observed, which correspond to the same planes (111), (200), (202), (311), and (222), indicating that the overall crystalline structure of NiO remains unchanged even after doping with sulfur and nitrogen. This suggests that the doping process does not induce a major phase change in the material but rather influences its crystallite size and micro strain \u003csup\u003e\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e\u003c/sup\u003e. The diffraction peaks for S/N co-doped NiO-NPs are broader compared to pure NiO-NPs, this Peak broadening typically indicates a reduction in crystallite size. This could be a result of the incorporation of sulfur and nitrogen ions into the NiO lattice, which disrupts the regular arrangement of NiO, leading to strain within the crystal lattice. The intensity of the diffraction peaks also decreases for the doped samples, further supporting the idea that doping with S and N leads to a less ordered crystalline structure, likely due to the differences in ionic radii between Ni (Ni\u0026sup2;⁺, 0.069 nm), S (S\u003csup\u003e\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e-\u003c/sup\u003e, 0.184 nm), and N (N\u003csup\u003e\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e-\u003c/sup\u003e, 0.146 nm) ions. The larger ionic radii of sulfur and nitrogen compared to nickel ions likely cause lattice distortion, which can result in reduced crystallinity and peak intensity \u003csup\u003e\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e\u003c/sup\u003e.The results are consistent with the standard reference (JCPDS Card No: 01-078-0423) \u003csup\u003e\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e\u003c/sup\u003e. This confirms that the doping process does not alter the overall crystalline structure of NiO but affects its crystallite size and micro strains. To calculate the average crystallite size, the Debye-Scherer equation which is expressed in \u003cb\u003eEq.\u0026nbsp;2.\u003c/b\u003e The d-spacing values for both the pure NiO-NPs and the S/N co-doped NiO-NPs are very similar, with slight shifts due to the doping process \u003cb\u003e(\u003c/b\u003eTable\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e\u003cb\u003e)\u003c/b\u003e. These shifts are expected, as the introduction of sulfur and nitrogen ions into the NiO lattice could cause some strain and potentially slightly expand the lattice parameters. However, overall, the crystalline structure remains essentially unchanged, confirming that the doping process doesn\u0026rsquo;t disrupt the fundamental face-centered cubic (FCC) structure of NiO. The particle size of the S/N co-doped NiO-NPs (17.49nm) is smaller than that of the pure NiO-NPs (20.89nm).\u003c/p\u003e \u003cp\u003e \u003cb\u003eD= (0.9 λ)/βcosθ\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;2\u003c/b\u003e \u003c/p\u003e \u003cp\u003eHere, λ represents the X-ray wavelength, D is the average crystal size, θ is the Bragg diffraction angle, and β is the FWHM in radians.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003e\u003cem\u003eSummary of the\u003c/em\u003e \u003cb\u003ed-spacing\u003c/b\u003e \u003cem\u003efor both\u003c/em\u003e \u003cb\u003eNiO NPs\u003c/b\u003e \u003cem\u003eand\u003c/em\u003e \u003cb\u003eS/N co-doped NiO NPs\u003c/b\u003e:\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\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=\"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=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePlane\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2θ (degree) (NiO)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003ed-spacing (NiO) (\u0026Aring;)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2θ (degree) (S/N co-doped)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003ed-spacing (S/N co-doped) (\u0026Aring;)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e(111)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e37.58\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e2.39\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e37.36\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e2.45\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e(200)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e43.54\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e2.08\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e43.40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e2.09\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e(202)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e63.09\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1.50\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e63.04\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.58\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e(311)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e75.68\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1.24\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e75.56\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.26\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e(222)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e79.64\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1.21\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e79.58\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.23\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\u003e \u003c/p\u003e \u003cp\u003eThe functional groups present in the synthesized nanoparticles were identified using Fourier Transform Infrared spectroscopy, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eb. The FT-IR spectra reveal the unique stretching and bending vibrations associated with various functional groups in both pure NiO and S/N co-doped NiO nanoparticles. Prominent peak observed at 3419\u0026ndash;3426 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e is attributed to the O-H stretching vibrations of water molecules adsorbed on the surface of the nanoparticles. This is a common feature in metal oxide nanoparticles, which tend to absorb moisture from the surrounding environment. The O-H bending vibration of the water molecules results in a strong absorption band at 1633 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e is, further confirming the presence of adsorbed water on the surface of the nanoparticles. Furthermore, the C\u0026thinsp;=\u0026thinsp;O (for pure NiO-NPs) may be responsible for the absorption bands at 1389 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and 1740 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. Following calcinations, the presence of hydroxyl and carbonyl groups in the NiO nanoparticles as-prepared suggests that the powder has a strong propensity to physically absorb CO\u003csub\u003e2\u003c/sub\u003e and water \u003csup\u003e\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e\u003c/sup\u003e. The peaks that formed at 1394 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, were created by the C\u0026thinsp;=\u0026thinsp;O stretching vibration of absorbed by the samples. While the peaks seen at 575 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and 833 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e were ascribed to the link between metal and oxygen (Ni-O), the peak that emerged at 2422 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e was ascribed to the presence of C\u0026thinsp;=\u0026thinsp;C stretching of alkenes molecules. The small peak that emerged at 1038 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e shows that incorporation of dopants into the NiO crystal lattice \u003csup\u003e\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e\u003c/sup\u003e was successful.\u003c/p\u003e \u003cp\u003eTo clarify the external structure of pure NiO-NPs and S/N co-doped NiO-NPs SEM analysis was conducted. The SEM images of pure NiO-NPs and S/N co-doped NiO-NPs are displayed in \u003cb\u003eFigure-2(c-d)\u003c/b\u003e. The SEM image of NiO-NPs \u003cb\u003e(\u003c/b\u003eFig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ec\u003cb\u003e)\u003c/b\u003e reveals a rock-like surface morphology formed by the aggregation of nanoparticles. These particles are uniformly dispersed in size but exhibit an agglomerated configuration \u003csup\u003e\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e\u003c/sup\u003e. In contrast, the SEM image of S/N co-doped NiO-NPs \u003cb\u003e(\u003c/b\u003eFig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ed\u003cb\u003e)\u003c/b\u003e shows spherical, interconnected particles, suggesting a strong interaction between the components that promotes the formation of particle aggregates \u003csup\u003e\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003e2.4. Photocatalytic activity test\u003c/h2\u003e \u003cp\u003eIn the present study S/N co-doped NiO nanoparticles was used to study the photocatalytic degradations of the methyl blue (MB) dye. S/N co-doped NiO nanoparticles then subjected to sun radiation (@ Jimma) at intervals of 10, 20, 30, 40, 50, and 60 min. A slow change in the dye solution's change from blue to colorless indicated the beginning of the dye degradation, which was followed by the steady decline of the characteristic MB absorption peak strength, which was detected at 666 nm.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003e2.5. Effect of reaction parameters on photocatalysis\u003c/h2\u003e \u003cp\u003eBefore the actual photocatalytic test, a number of photocatalytic requirements were carefully adjusted. These factors included the impacts of starting dye concentration pH, catalyst dose, and Time of Contact.\u003c/p\u003e \u003cdiv id=\"Sec13\" class=\"Section3\"\u003e \u003ch2\u003e2.5.1. Effect of Initial Dye Concentration\u003c/h2\u003e \u003cp\u003eThe initial concentration of MB dye affects the photo catalytic performance. As shown in \u003cb\u003e(\u003c/b\u003eFig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ea\u003cb\u003e)\u003c/b\u003e, the photo catalytic activity is higher at lower dye concentrations (5ppm), with the degradation efficiency decreasing at higher concentrations. At higher dye concentrations, the solution absorbs more light, limiting photon penetration and reducing the generation of hydroxyl radicals. Consequently, the degradation efficiency decreases as the dye concentration increases, with a maximum of 98.9% degradation observed at 5ppm MB dye \u003csup\u003e\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec14\" class=\"Section3\"\u003e \u003ch2\u003e2.5.2. Effect of dye solution pH\u003c/h2\u003e \u003cp\u003eThe rate of dye solution photo degradation in an aqueous medium is highly sensitive to pH value. Changing the dye solution's medium (pH value) effectively modifies the rate of photo degradation. It results from a shift in how the catalyst and dye interact at various pH levels. The pH was adjusted using 0.1 M HCl and NaOH solutions to pH 6, 8, 10, and 12, with 40 mg of S/N co-doped NiO-NPs catalyst dose and 5ppm MB dye for 60 min. The degradation efficiency of MB dye increased as the pH of the solution rose from 6 to 10, reaching a maximum of 98.9% degradation at pH 10 \u003cb\u003e(\u003c/b\u003eFig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eb\u003cb\u003e)\u003c/b\u003e. This enhanced performance at higher pH values can be attributed to the generation of hydroxyl radicals, which are critical for the photo catalytic degradation of MB dye. The surface of the nanoparticles becomes highly positive in the acidic medium at lower pH values, which repels cationic dye molecules. On the other hand, the catalytic surface becomes negatively charged in the basic medium at higher pH values, which considerably attracts more and more positively charged dye molecules. \u003csup\u003e\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e\u003c/sup\u003e. Consequently, the rate of photo degradation effectively increased as the pH value rose \u003csup\u003e\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e\u003c/sup\u003e. However, further increase in pH of the solution to the basic medium reduces photodegradationtion efficiency due to the repulsion of hydroxide ions with the negatively charged photocatalyst surface.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec15\" class=\"Section3\"\u003e \u003ch2\u003e2.5.3. Effect of Photocatalyst Dosages\u003c/h2\u003e \u003cp\u003eIn order to determine the ideal amount of catalyst for the effective photocatalytic degradation of MB dye, visible light was used to illuminate doses containing different concentrations of S/N co-doped NiO-NPs catalyst (20 mg, 30 mg, 40 mg, and 50 mg) with MB dye solutions at an optimum pH (pH\u0026thinsp;=\u0026thinsp;11) Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ec. The results, shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ec, indicate that as the catalyst dosage increases, the degradation efficiency rises due to the greater number of active sites available for the generation of hydroxyl radicals. However, at higher dosages (beyond 40 mg), the degradation efficiency levels off, as the increased viscosity of the suspension impedes light penetration, thereby reducing photo catalytic activity. Therefore, 40 mg of catalyst was found to be optimal for 5 ppm MB dye degradation \u003csup\u003e\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e\u003c/sup\u003e. As the dosage of S/N co-doped NiO-NPs was raised from 20 mg to 40 mg, the degradation rate of MB increased from 82.50\u0026ndash;98.90%. Nevertheless after 40 mg, MB degradation did not considerably increase with dosage increases. Consequently, it was found that the photo catalytic degradation of 5ppm MB was best achieved with 40 mg a catalyst dosage.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec16\" class=\"Section3\"\u003e \u003ch2\u003e2.5.4. Effect of Contact Time\u003c/h2\u003e \u003cp\u003e \u003cdiv class=\"BlockQuote\"\u003e \u003cp\u003eThe effects of contact time on the photodegradation of MB have been studied in the presence of S/N co-doped NiO-NPs under visible light Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ed. The results showed that the degradation efficiency increased as time increased. This can be explained by the increase in dye molecules interaction with the surface of the photocatalyst. The maximum degradation efficiency was observed at 60 min, showing negligible degradation efficiency afterwards. Hence 60 min was considered in the follow up experiments. The enhancement of the photocatalytic activity for MB degradation could be attributed to the large specific surface area of S/N co-doped NiO-NPs.\u003c/p\u003e \u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec17\" class=\"Section3\"\u003e \u003ch2\u003e2.5.5. Comparisons of degradation efficiency of MB dye with and without Catalyst\u003c/h2\u003e \u003cp\u003eThe photocatalytic properties of the prepared NiO nanoparticles and S/N co-doped NiO-NPs were investigated by decomposing MB. The effect of irradiation time on the degradation of MB dye was examined using UV-Vis absorbance spectra, and the absorbance was used to quantify the degradation percentage. A beaker containing 100 mL of 5 ppm MB dye at pH 10 was filled with 40 mg of each photocatalyst. The mixture was then continuously stirred and subjected to light for 0, 10, 20, 30, 40, 50, and 60 min. Following string, three distinct systems were exposed to light: pure MB, NiO-NPs containing and S/N co-doped NiO-NPs containing MB. Every 10 min, the UV\u0026ndash;Vis absorption of each system was recorded. The UV\u0026ndash;Vis absorption spectra of the MB degradation kinetics are displayed in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e. After being exposed to light, the absorbance peaks for the MB containing pure NiO-NPs gradually dropped \u003cb\u003e(\u003c/b\u003eFig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eb\u003cb\u003e)\u003c/b\u003e. The MB sample containing S/N co-doped NiO-NPs showed a sharp decline in peak intensity from the UV-Vis measurement, reaching nearly zero after 60 min of light irradiation \u003cb\u003e(\u003c/b\u003eFig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ec\u003cb\u003e)\u003c/b\u003e. After 60 min of light irradiation, the solution's color likewise faded and turned colorless following the absorbance peak intensity drop. Within 60 min of contact time, 98.9% of the MB dye was destroyed, indicating that the nanocomposite had reached its maximal degradation efficiency. In contrast, after 60 min of light irradiation, peak intensities were nearly preserved in MB that did not have a catalyst. The lack of noticeable MB degradation in the absence of photocatalysts (blank test) under light irradiation suggests that MB resists photo degradation and that its self-degradation contribution is negligible \u003cb\u003e(\u003c/b\u003eFig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ea\u003cb\u003e).\u003c/b\u003e Because of its high-energy band gap, NiO-NPs exhibit a sluggish photocatalytic behavior in visible light, which was also responsible for the modest degradation of MB in pure NiO-NPs. The Summary of the comparison of the current work and previously published works are summarized in \u003cb\u003eTable-3\u003c/b\u003e.Thus, the photocatalytic degradation efficiency and rate of this work is by far better than most of the published works on the area. The addition of S/N co-doping are crucial steps in enhancing the photocatalytic behavior of NiO-NPs by shifting the energy band gap toward the red \u003csup\u003e\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e,\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003e\u003cem\u003eComparison among the photocatalytic efficiency of various photocatalysts for photo degradation of MB dye\u003c/em\u003e\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"6\"\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=\"left\" 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=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCatalyst\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSource of light\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eDye\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eTime(min)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eDegradation (%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eReferences\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCu-doped NiO-NPs\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eVisible light\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eMB\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e60\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e89.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u003csup\u003e\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMn-doped NiO NPs\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eUv-light\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eMB\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e210\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e92.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u003csup\u003e\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCu-doped NiO-NPs\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eUv-light\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eMB\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e103\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e78.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u003csup\u003e\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eS/N co-doped NiO-NPs\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eVisible light\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eMB\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e60\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e98.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eThis Work\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\u003e \u003c/p\u003e \u003cp\u003eBy analyzing the 3-cycles degradation of MB, the recyclability of S/N co-doped NiO-NPs for dye degradation was established. Every cycle, the photocatalyst was cleaned with ethanol and then utilized again. The number of cycles the S/N co-doped NiO-NPs photocatalyst can be utilized was displayed in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e. It was tested for reusability using the same optimal operating parameters as the S/N co-doped NiO-NPs. Degradation efficiency was 98.90%, 93.53%, and 89.92% for the first three cycles, respectively, with an initial dye concentration of 5 ppm, a catalyst dose of 40 mg, a pH of 10, and an irradiation time of 60 min. In the second and third cycles, the photocatalytic degradation efficiency of S/N co-doped NiO-NPs declines, possibly as a result of waste ion accumulation and catalyst dosage that produces contaminants. With a minor reduction in efficiency, our experiment demonstrates that the synthesized S/N co-doped NiO-NPs photocatalyst may be recycled for three more cycles. S/N co-doped NiO-NPs function as a highly effective and stable photocatalyst.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec18\" class=\"Section2\"\u003e \u003ch2\u003e2.6. Antibacterial activity test\u003c/h2\u003e \u003cp\u003eIn order to examine the antibacterial activity of synthesized NiO-NPs and S/N co-doped NiO-NPs, the disk diffusion method was used against Gram-positive and Gram-negative bacterial strains. Gentamicin and DMSO were used as positive and negative controls, respectively. The antibacterial activities of 25, 50, 75 and 100 mg/mL of synthesized NPs were tested against S. aureus, E. coli, B. cereus, and S. typhi \u003csup\u003e\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e\u003c/sup\u003e. The results of the study showed that gram-positive bacteria, such as S. aureus and B. cereus, were more inhibited by the synthesized S/N co-doped NiO-NCs than gram-negative strains like E. coli and S. typhi. Additionally, the nickel ions released from the NPs could bind to the negatively charged bacterial cell wall, causing it to disrupted, leading to protein denaturation and cell death. Small-sized NPs have high penetration ability and cause rapid cell damage compared to other bulk compounds \u003csup\u003e\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e\u003c/sup\u003e. The co-doped nanoparticles antibacterial activity was superior to that of pure NiO-NPs, indicating that the introduction of S/N co-doping improved the NPs antimicrobial activity. The inhibition zones of antimicrobial measurements are given in Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e.\u003c/p\u003e \u003cp\u003eThe antibacterial activity increased with concentration of synthesized NPs, with a significant inhibition zone which ascribed the stronger antibacterial activities of synthesized NPs. As shown in Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e and Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e, the S/N co-doped NiO-NPs demonstrated stronger antibacterial activity against S. aureus (17 mm) than against E. coli (14 mm) but NiO-NPs shows insignificant inhibition zone for all bacteria strain when compared to S/N co-doped NiO-NPs. The antibacterial effect is attributed to the increased surface area and smaller crystallite size of the nanoparticles, which facilitate the generation of reactive oxygen species (ROS) that disrupt bacterial cell membranes and inhibit bacterial growth \u003csup\u003e\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e\u003c/sup\u003e.The antibacterial activity of S/N co-doped NiO-NPs against Gram-positive bacteria (S. aureus and B. cereus) is significantly higher than for Gram-negative bacteria (E. coli and S. typhi). The study highlights that S/N co-doping enhances the antibacterial properties, suggesting that the nanoparticles release reactive oxygen species (ROS), which disrupt bacterial membranes \u003csup\u003e\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e\u003c/sup\u003e.This finding is in line with previous research showing that the antibacterial properties of NiO can be enhanced through doping, but this study provides comparative data showing the superiority of the S/N co-doping strategy \u003csup\u003e\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab4\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003e\u003cem\u003eAntibacterial Activity of NiO-NPs and S/N-NiO-NCs\u003c/em\u003e\u003c/p\u003e \u003c/div\u003e \u003c/caption\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=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colspan=\"5\" nameend=\"c5\" namest=\"c1\"\u003e \u003cp\u003eInhibition zones (mm\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\u003eBacterial strain\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e \u003cp\u003eControls\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e \u003cp\u003eTarget materials (100 mg/mL)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eGentamicin (+\u0026thinsp;ve)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eDMSO (-ve)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eNiO-NPs\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eS/N co-doped-NiO-NPs\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eB.cereus\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e26\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e13\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eE.coli\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e27\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e14\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eS.typhi\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e27\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e15\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eS.ureus\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e29\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e17\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\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"3. Conclusions","content":"\u003cp\u003eThe co-precipitation method was successfully employed to synthesize both pure NiO and S/N co-doped NiO-NPs. The optical properties of the nanoparticles were characterized using a UV-Vis spectrometer. The pure NiO nanoparticles exhibited an absorbance peak at 303 nm, indicating a blue shift. In contrast, the S/N co-doped NiO nanoparticles showed an absorbance peak at 329 nm, indicating a red shift. The incorporation of 4% sulfur and 6% nitrogen into the NiO lattice reduced the band gap from 3.75 eV (for pure NiO) to 2.74 eV (for S/N co-doped NiO). XRD analysis confirmed the formation of a crystalline FCC structure for the NiO nanoparticles, with no additional peaks corresponding to the S/N dopants, indicating successful doping. XRD studies showed the purity and crystalline structure of NiO-NPs and S/N-NiO-NPs with crystallite sizes of 20.49 and 17.89 nm respectively. The morphology of the synthesized nanoparticles was analyzed using SEM. The FT-IR spectra revealed the characteristic Ni-O stretching vibration at 825 and 594 cm⁻\u0026sup1; for pure NiO-NPs and at 825 and 575 cm\u003csup\u003e\u0026minus;\u003c/sup\u003e\u0026sup1; for the S/N co-doped NiO-NPs, confirming the presence of Ni-O bonds. In Photocatalysis degradation tests, methylene blue 5ppm MB dye was almost completely degraded (98.9%) within 60 minutes at an optimal pH of 10 and a catalyst dose of 40 mg of S/N co-doped NiO-NPs. Importantly, the Photocatalysis activity of the material remained stable across at least three consecutive reaction cycles, demonstrating its potential for sustained performance in environmental applications. Antibacterial activity, assessed through inhibition zone measurements, showed significant improvement: NiO-NPs exhibited zones of 5\u0026ndash;10 mm, while S/N-NiO-NPs achieved 13\u0026ndash;17 mm against Bacillus cereus, Escherichia coli, Salmonella typhi, and Staphylococcus aureus. These suggest that the antibacterial activity of S/N co-doped NiO-NPs against Gram-positive bacteria (S. aureus, B. cereus) is significantly higher than for Gram-negative bacteria (E. coli, S. typhi).\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e \u003ch2\u003eConflict of Interest\u003c/h2\u003e \u003cp\u003eThe authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.\u003c/p\u003e \u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eTariku Tamesgen, Zhu Kai, and Tamene Tadesse Beyene conception of the idea. Tariku Tamesgen, Michael Asfaw Ameya, Getu Sisay, and Lu Yuanqi underwent the experiment, analysed data, and wrote the draft. Zhu Kai and Tamene Tadesse Beyene supervised the work, revised the drafted manuscript\u003c/p\u003e\u003ch2\u003eAcknowledgement\u003c/h2\u003e\u003cp\u003eThis work was financially supported by the College of Natural Sciences at Jimma University under the PG student project\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eG\u0026oacute;ralczyk-Bińkowska, A.; Długoński, A.; Bernat, P.; Długoński, J.; Jasińska, A. Environmental and Molecular Approach to Dye Industry Waste Degradation by the Ascomycete Fungus Nectriella Pironii. \u003cem\u003eSci Rep\u003c/em\u003e \u003cstrong\u003e2021\u003c/strong\u003e, \u003cem\u003e11\u003c/em\u003e (1), 1\u0026ndash;13. https://doi.org/10.1038/s41598-021-03446-x.\u003c/li\u003e\n\u003cli\u003eIshak, S. A.; Murshed, M. F.; Akil, H. M.; Ismail, N.; Md Rasib, S. Z.; Al-Gheethi, A. A. S. The Application of Modified Natural Polymers in Toxicant Dye Compounds Wastewater: A Review. \u003cem\u003eWater (Switzerland)\u003c/em\u003e \u003cstrong\u003e2020\u003c/strong\u003e, \u003cem\u003e12\u003c/em\u003e (7). https://doi.org/10.3390/w12072032.\u003c/li\u003e\n\u003cli\u003eLiu, T.; Jiang, C.; Zhu, L.; Jiang, L.; Huang, H. Fe3O4@chitosan Microspheres Coating as Cytoprotective Exoskeletons for the Enhanced Production of Butyric Acid With Clostridium Tyrobutyricum Under Acid Stress. \u003cem\u003eFront Bioeng Biotechnol\u003c/em\u003e \u003cstrong\u003e2020\u003c/strong\u003e, \u003cem\u003e8\u003c/em\u003e (May), 1\u0026ndash;13. https://doi.org/10.3389/fbioe.2020.00449.\u003c/li\u003e\n\u003cli\u003eHasanpour, M.; Hatami, M. \u003cem\u003ePhotocatalytic Performance of Aerogels for Organic Dyes Removal from Wastewaters: Review Study\u003c/em\u003e; Elsevier B.V, 2020; Vol. 309. https://doi.org/10.1016/j.molliq.2020.113094.\u003c/li\u003e\n\u003cli\u003eIyyappan, J.; Gaddala, B.; Gnanasekaran, R.; Gopinath, M.; Yuvaraj, D.; Kumar, V. Critical Review on Wastewater Treatment Using Photo Catalytic Advanced Oxidation Process: Role of Photocatalytic Materials, Reactor Design and Kinetics. \u003cem\u003eCase Stud Chem Environ Eng\u003c/em\u003e \u003cstrong\u003e2024\u003c/strong\u003e, \u003cem\u003e9\u003c/em\u003e (November 2023), 100599. https://doi.org/10.1016/j.cscee.2023.100599.\u003c/li\u003e\n\u003cli\u003eGhamarpoor, R.; Fallah, A.; Jamshidi, M. A Review of Synthesis Methods, Modifications, and Mechanisms of ZnO/TiO2-Based Photocatalysts for Photodegradation of Contaminants. \u003cem\u003eACS Omega\u003c/em\u003e \u003cstrong\u003e2024\u003c/strong\u003e, \u003cem\u003e9\u003c/em\u003e (24), 25457\u0026ndash;25492. https://doi.org/10.1021/acsomega.3c08717.\u003c/li\u003e\n\u003cli\u003eSanghavi, L.; Sanghavi, L. K.; Shashi, D. R.; Ranga, V. Study of Operating Parameters for Removal of Direct Yellow 12 Dye Using Prosopis Juliflora Bark Wastewater Treatment Using Low Cost Adsorbent View Project Study of Operating Parameters for Removal of Direct Yellow 12 Dye Using Prosopis Juliflora Bark. \u003cem\u003eIJRAR19K2418 Int J Res Anal Rev (IJRAR)wwwijrarorg\u003c/em\u003e \u003cstrong\u003e2019\u003c/strong\u003e, \u003cem\u003e869\u003c/em\u003e (May). https://doi.org/10.13140/RG.2.2.10937.01122.\u003c/li\u003e\n\u003cli\u003eTang, K. W. K.; Millar, B. C.; Moore, J. E. Antimicrobial Resistance (AMR). \u003cem\u003eBr J Biomed Sci\u003c/em\u003e \u003cstrong\u003e2023\u003c/strong\u003e, \u003cem\u003e80\u003c/em\u003e (June), 1\u0026ndash;11. https://doi.org/10.3389/bjbs.2023.11387.\u003c/li\u003e\n\u003cli\u003eGhirardello, M.; Ramos-Soriano, J.; Galan, M. C. Carbon Dots as an Emergent Class of Antimicrobial Agents. \u003cem\u003eNanomaterials\u003c/em\u003e \u003cstrong\u003e2021\u003c/strong\u003e, \u003cem\u003e11\u003c/em\u003e (8), 1\u0026ndash;24. https://doi.org/10.3390/nano11081877.\u003c/li\u003e\n\u003cli\u003eLi, H.; Huang, J.; Song, Y.; Zhang, M.; Wang, H.; Lu, F.; Huang, H.; Liu, Y.; Dai, X.; Gu, Z.; Yang, Z.; Zhou, R.; Kang, Z. Degradable Carbon Dots with Broad-Spectrum Antibacterial Activity. \u003cem\u003eACS Appl Mater Interfaces\u003c/em\u003e \u003cstrong\u003e2018\u003c/strong\u003e, \u003cem\u003e10\u003c/em\u003e (32), 26936\u0026ndash;26946. https://doi.org/10.1021/acsami.8b08832.\u003c/li\u003e\n\u003cli\u003eIjaz, I.; Gilani, E.; Nazir, A.; Bukhari, A. Green Chemistry Letters and Reviews Detail Review on Chemical , Physical and Green Synthesis , Classification , Characterizations and Applications of Nanoparticles. \u003cstrong\u003e2020\u003c/strong\u003e. https://doi.org/10.1080/17518253.2020.1802517.\u003c/li\u003e\n\u003cli\u003eHaider, A.; Ijaz, M.; Ali, S.; Haider, J.; Imran, M.; Majeed, H.; Shahzadi, I.; Ali, M. M.; Khan, J. A.; Ikram, M. Green Synthesized Phytochemically (Zingiber Officinale and Allium Sativum) Reduced Nickel Oxide Nanoparticles Confirmed Bactericidal and Catalytic Potential. \u003cem\u003eNanoscale Res Lett\u003c/em\u003e \u003cstrong\u003e2020\u003c/strong\u003e, \u003cem\u003e15\u003c/em\u003e (1). https://doi.org/10.1186/s11671-020-3283-5.\u003c/li\u003e\n\u003cli\u003eErjeno, D. J. D.; Asequia, D. M. A.; Osorio, C. K. F.; Omisol, C. J. M.; Etom, A. E.; Hisona, R. M. R.; Tilendo, A. C.; Triana, A. P. G.; Dumancas, G. G.; Zoleta, J. B.; Alguno, A. C.; Malaluan, R. M.; Lubguban, A. A. Facile Synthesis of Band Gap-Tunable Kappa-Carrageenan-Mediated C,S-Doped TiO2 Nanoparticles for Enhanced Dye Degradation. \u003cem\u003eACS Omega\u003c/em\u003e \u003cstrong\u003e2024\u003c/strong\u003e, \u003cem\u003e9\u003c/em\u003e (19), 21245\u0026ndash;21259. https://doi.org/10.1021/acsomega.4c01370.\u003c/li\u003e\n\u003cli\u003eAl-Shawi, S. G.; Alekhina, N. A.; Aravindhan, S.; Thangavelu, L.; Kartamyshev, N. V.; Zakieva, R. R. Synthesis of NiO Nanoparticles and Sulfur, and Nitrogen Co Doped-Graphene Quantum Dots/ NiO Nanocomposites for Antibacterial Application. \u003cem\u003eJ Nanostructures\u003c/em\u003e \u003cstrong\u003e2021\u003c/strong\u003e, \u003cem\u003e11\u003c/em\u003e (1), 181\u0026ndash;188. https://doi.org/10.22052/JNS.2021.01.019.\u003c/li\u003e\n\u003cli\u003eMinisha, S.; Johnson, J.; Mohammad Wabaidur, S.; Gupta, J. K.; Aftab, S.; Siddiqui, M. R.; Lai, W. C. Synthesis and Characterizations of Fe-Doped NiO Nanoparticles and Their Potential Photocatalytic Dye Degradation Activities. \u003cem\u003eSustain \u003c/em\u003e \u003cstrong\u003e2023\u003c/strong\u003e, \u003cem\u003e15\u003c/em\u003e (19). https://doi.org/10.3390/su151914552.\u003c/li\u003e\n\u003cli\u003eSandeep, S.; Koteswara Rao, C.; Vijay Rajesh, A.; Sruthi, T.; Prakash, D. S. Studies on Characterization and Optimization Parameters of Zinc Oxide Nanoparticles Synthesis. \u003cem\u003eInt J Curr Res Rev\u003c/em\u003e \u003cstrong\u003e2022\u003c/strong\u003e, \u003cem\u003e14\u003c/em\u003e (03), 06\u0026ndash;11. https://doi.org/10.31782/ijcrr.2022.14302.\u003c/li\u003e\n\u003cli\u003eAgale, A. A.; Gaikwad, S. T.; Rajbhoj, A. S. Nanosized Synthesis of Nickel Oxide by Electrochemical Reduction Method and Their Antifungal Screening. \u003cem\u003eJ Clust Sci\u003c/em\u003e \u003cstrong\u003e2017\u003c/strong\u003e, \u003cem\u003e28\u003c/em\u003e (4), 2097\u0026ndash;2109. https://doi.org/10.1007/s10876-017-1203-3.\u003c/li\u003e\n\u003cli\u003eMorgan, R. N.; Aboshanab, K. M. Green Biologically Synthesized Metal Nanoparticles: Biological Applications, Optimizations and Future Prospects. \u003cem\u003eFutur Sci OA\u003c/em\u003e \u003cstrong\u003e2024\u003c/strong\u003e, \u003cem\u003e10\u003c/em\u003e (1). https://doi.org/10.2144/fsoa-2023-0196.\u003c/li\u003e\n\u003cli\u003eNouren, S.; Bibi, I.; Kausar, A.; Sultan, M.; Nawaz Bhatti, H.; Safa, Y.; Sadaf, S.; Alwadai, N.; Iqbal, M. Green Synthesis of CuO Nanoparticles Using Jasmin Sambac Extract: Conditions Optimization and Photocatalytic Degradation of Methylene Blue Dye. \u003cem\u003eJ King Saud Univ - Sci\u003c/em\u003e \u003cstrong\u003e2024\u003c/strong\u003e, \u003cem\u003e36\u003c/em\u003e (3), 103089. https://doi.org/10.1016/j.jksus.2024.103089.\u003c/li\u003e\n\u003cli\u003eKhairunnisa, S.; Wonoputri, V.; Samadhi, T. W. Effective Deagglomeration in Biosynthesized Nanoparticles: A Mini Review. \u003cem\u003eIOP Conf Ser Mater Sci Eng\u003c/em\u003e \u003cstrong\u003e2021\u003c/strong\u003e, \u003cem\u003e1143\u003c/em\u003e (1), 012006. https://doi.org/10.1088/1757-899x/1143/1/012006.\u003c/li\u003e\n\u003cli\u003eFirisa, S. G.; Muleta, G. G.; Yimer, A. A. Synthesis of Nickel Oxide Nanoparticles and Copper-Doped Nickel Oxide Nanocomposites Using Phytolacca Dodecandra L\u0026rsquo;Herit Leaf Extract and Evaluation of Its Antioxidant and Photocatalytic Activities. \u003cem\u003eACS Omega\u003c/em\u003e \u003cstrong\u003e2022\u003c/strong\u003e, \u003cem\u003e7\u003c/em\u003e (49), 44720\u0026ndash;44732. https://doi.org/10.1021/acsomega.2c04042.\u003c/li\u003e\n\u003cli\u003eVenkatachalapathy, M.; Sambathkumar, K.; Kamal, N. R. Synthesis and Characterization of Structural and Magnetic Properties of Fe Doped NiO Nanoparticles. \u003cem\u003eDig J Nanomater Biostructures\u003c/em\u003e \u003cstrong\u003e2024\u003c/strong\u003e, \u003cem\u003e19\u003c/em\u003e (1), 451\u0026ndash;458. https://doi.org/10.15251/DJNB.2024.191.451.\u003c/li\u003e\n\u003cli\u003eChattopadhyay, J.; Pathak, T. S.; Pak, D. Heteroatom-Doped Metal-Free Carbon Nanomaterials As. \u003cem\u003eMolecules\u003c/em\u003e \u003cstrong\u003e2022\u003c/strong\u003e, \u003cem\u003e27\u003c/em\u003e, 670.\u003c/li\u003e\n\u003cli\u003eChakravorty, A.; Roy, S. A Review of Photocatalysis, Basic Principles, Processes, and Materials. \u003cem\u003eSustain Chem Environ\u003c/em\u003e \u003cstrong\u003e2024\u003c/strong\u003e, \u003cem\u003e8\u003c/em\u003e (September), 100155. https://doi.org/10.1016/j.scenv.2024.100155.\u003c/li\u003e\n\u003cli\u003ePonnusamy, P. M.; Agilan, S.; Muthukumarasamy, N.; Velauthapillai, D. Effect of Chromium and Cobalt Addition on Structural, Optical and Magnetic Properties of NiO Nanoparticles. \u003cem\u003eZeitschrift fur Phys Chemie\u003c/em\u003e \u003cstrong\u003e2016\u003c/strong\u003e, \u003cem\u003e230\u003c/em\u003e (8), 1185\u0026ndash;1197. https://doi.org/10.1515/zpch-2015-0678.\u003c/li\u003e\n\u003cli\u003eAtul, A. K.; Srivastava, S. K.; Gupta, A. K.; Srivastava, N. Synthesis and Characterization of NiO Nanoparticles by Chemical Co-Precipitation Method: An Easy and Cost-Effective Approach. \u003cem\u003eBrazilian J Phys\u003c/em\u003e \u003cstrong\u003e2022\u003c/strong\u003e, \u003cem\u003e52\u003c/em\u003e (1), 2\u0026ndash;7. https://doi.org/10.1007/s13538-021-01006-2.\u003c/li\u003e\n\u003cli\u003eAlam, M. W.; BaQais, A.; Mir, T. A.; Nahvi, I.; Zaidi, N.; Yasin, A. Effect of Mo Doping in NiO Nanoparticles for Structural Modification and Its Efficiency for Antioxidant, Antibacterial Applications. \u003cem\u003eSci Rep\u003c/em\u003e \u003cstrong\u003e2023\u003c/strong\u003e, \u003cem\u003e13\u003c/em\u003e (1), 1\u0026ndash;18. https://doi.org/10.1038/s41598-023-28356-y.\u003c/li\u003e\n\u003cli\u003eRamesh, M. N and Fe Doped NiO Nanoparticles for Enhanced Photocatalytic Degradation of Azo Dye Methylene Blue in the Presence of Visible Light. \u003cem\u003eSN Appl Sci\u003c/em\u003e \u003cstrong\u003e2021\u003c/strong\u003e, \u003cem\u003e3\u003c/em\u003e (10). https://doi.org/10.1007/s42452-021-04803-1.\u003c/li\u003e\n\u003cli\u003eKhan, S.; Noor, T.; Iqbal, N.; Yaqoob, L. Photocatalytic Dye Degradation from Textile Wastewater: A Review. \u003cem\u003eACS Omega\u003c/em\u003e \u003cstrong\u003e2024\u003c/strong\u003e, \u003cem\u003e9\u003c/em\u003e (20), 21751\u0026ndash;21767. https://doi.org/10.1021/acsomega.4c00887.\u003c/li\u003e\n\u003cli\u003eTegenaw, A. B.; Yimer, A. A.; Beyene, T. T. Boosting the Photocatalytic Activity of ZnO-NPs through the Incorporation of C-Dot and Preparation of Nanocomposite Materials. \u003cem\u003eHeliyon\u003c/em\u003e \u003cstrong\u003e2023\u003c/strong\u003e, \u003cem\u003e9\u003c/em\u003e (10), e20717. https://doi.org/10.1016/j.heliyon.2023.e20717.\u003c/li\u003e\n\u003cli\u003eKumari, V.; Yadav, S.; Jindal, J.; Sharma, S.; Kumari, K.; Kumar, N. Synthesis and Characterization of Heterogeneous ZnO/CuO Hierarchical Nanostructures for Photocatalytic Degradation of Organic Pollutant. \u003cem\u003eAdv Powder Technol\u003c/em\u003e \u003cstrong\u003e2020\u003c/strong\u003e, \u003cem\u003e31\u003c/em\u003e (7), 2658\u0026ndash;2668. https://doi.org/10.1016/j.apt.2020.04.033.\u003c/li\u003e\n\u003cli\u003eAndrade, P. F.; Nakazato, G.; Dur\u0026aacute;n, N. Additive Interaction of Carbon Dots Extracted from Soluble Coffee and Biogenic Silver Nanoparticles against Bacteria. \u003cem\u003eJ Phys Conf Ser\u003c/em\u003e \u003cstrong\u003e2017\u003c/strong\u003e, \u003cem\u003e838\u003c/em\u003e (1). https://doi.org/10.1088/1742-6596/838/1/012028.\u003c/li\u003e\n\u003cli\u003eAnju Chanu, L.; Joychandra Singh, W.; Jugeshwar Singh, K.; Nomita Devi, K. Effect of Operational Parameters on the Photocatalytic Degradation of Methylene Blue Dye Solution Using Manganese Doped ZnO Nanoparticles. \u003cem\u003eResults Phys\u003c/em\u003e \u003cstrong\u003e2019\u003c/strong\u003e, \u003cem\u003e12\u003c/em\u003e (December 2018), 1230\u0026ndash;1237. https://doi.org/10.1016/j.rinp.2018.12.089.\u003c/li\u003e\n\u003cli\u003eSahu, K.; Bisht, A.; Kuriakose, S.; Mohapatra, S. Two-Dimensional CuO-ZnO Nanohybrids with Enhanced Photocatalytic Performance for Removal of Pollutants. \u003cem\u003eJ Phys Chem Solids\u003c/em\u003e \u003cstrong\u003e2020\u003c/strong\u003e, \u003cem\u003e137\u003c/em\u003e, 109223. https://doi.org/10.1016/j.jpcs.2019.109223.\u003c/li\u003e\n\u003cli\u003ePadma; Ranju, S.; Yeshas; Kavya, S. L.; Sukrutha, S. K.; Kumar, M. R. A.; Kumar, A. N.; Kumaraswamy, M.; Purushotham, B.; Boppana, S. B. A Comparative Study of Green and Chemically Synthesized Nano Nickel Oxide for Multifunctional Applications. \u003cem\u003eAppl Surf Sci Adv\u003c/em\u003e \u003cstrong\u003e2022\u003c/strong\u003e, \u003cem\u003e12\u003c/em\u003e (October), 100318. https://doi.org/10.1016/j.apsadv.2022.100318.\u003c/li\u003e\n\u003cli\u003eIslam, R.; Abdur, R.; Alam, M. A.; Munna, N.; Ahmed, A. N.; Hossain, M.; Bashar, M. S.; Islam, D.; Jamal, M. S. Modulating Mn-Doped NiO Nanoparticles: Structural, Optical, and Electrical Property Tailoring for Enhanced Hole Transport Layers. \u003cem\u003eNanoscale Adv\u003c/em\u003e \u003cstrong\u003e2024\u003c/strong\u003e. https://doi.org/10.1039/d4na00708e.\u003c/li\u003e\n\u003cli\u003eIlbeigi, G.; Kariminik, A.; Moshafi, M. H. The Antibacterial Activities of NiO Nanoparticles Against Some Gram-Positive and Gram-Negative Bacterial Strains. \u003cem\u003eInt J Basic Sci Med\u003c/em\u003e \u003cstrong\u003e2019\u003c/strong\u003e, \u003cem\u003e4\u003c/em\u003e (2), 69\u0026ndash;74. https://doi.org/10.15171/ijbsm.2019.14.\u003c/li\u003e\n\u003cli\u003eOzdal, M.; Gurkok, S. Recent Advances in Nanoparticles as Antibacterial Agent. \u003cem\u003eADMET DMPK\u003c/em\u003e \u003cstrong\u003e2022\u003c/strong\u003e, \u003cem\u003e10\u003c/em\u003e (2), 115\u0026ndash;129. https://doi.org/10.5599/admet.1172.\u003c/li\u003e\n\u003cli\u003eAli, A. Y.; Alani, A. A. K.; Ahmed, B. O.; Hamid, L. L. Effect of Biosynthesized Silver Nanoparticle Size on Antibacterial and Anti-Biofilm Activity against Pathogenic Multi-Drug Resistant Bacteria. \u003cem\u003eOpenNano\u003c/em\u003e \u003cstrong\u003e2024\u003c/strong\u003e, \u003cem\u003e20\u003c/em\u003e (July), 100213. https://doi.org/10.1016/j.onano.2024.100213.\u003c/li\u003e\n\u003cli\u003eMahmoudi Khatir, N.; Khorsand Zak, A. Antibacterial Activity and Structural Properties of Gelatin-Based Sol-Gel Synthesized Cu-Doped ZnO Nanoparticles; Promising Material for Biomedical Applications. \u003cem\u003eHeliyon\u003c/em\u003e \u003cstrong\u003e2024\u003c/strong\u003e, \u003cem\u003e10\u003c/em\u003e (17), e37022. https://doi.org/10.1016/j.heliyon.2024.e37022.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Antibacterial, Energy band gap, methylene blue dye degradation, nanoparticles, S/N co-doping NiO-NPs","lastPublishedDoi":"10.21203/rs.3.rs-6493877/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6493877/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eNickel oxide (NiO) has gained attention as a promising photocatalyst, thanks to its high efficiency, photochemical stability, cost-effectiveness, and eco-friendly nature. However, a wide band gap and rapid electron-hole recombination hinder its practical application under visible light. This study synthesized pure NiO nanoparticles (NiO-NPs) and sulfur/nitrogen co-doped NiO nanoparticles (S/N-NiO-NPs) via the co-precipitation method. Comprehensive structural and optical analyses using UV-Vis, FT-IR, XRD, and SEM confirmed the successful formation of the desired materials. Notably, doping with 4% sulfur and 6% nitrogen significantly enhanced charge separation, extended light absorption, narrowed the band gap from 3.75 eV to 2.50 eV, and reduced crystalline size from 20.49 nm to 17.89 nm. Under optimal conditions (pH 10),40 mg of S/N-NiO-NPs achieved an impressive 98.9% degradation of 5 ppm methylene blue dye within just 60 min of sunlight irradiation, far outperforming pure NiO-NPs. Additionally, antibacterial evaluations demonstrated superior efficacy, with S/N-NiO-NPs exhibiting inhibition zones of13\u0026ndash;17 mm against pathogens such as \u003cem\u003eBacillus cereus\u003c/em\u003e, \u003cem\u003eEscherichia coli\u003c/em\u003e, \u003cem\u003eSalmonella typhi\u003c/em\u003e, and \u003cem\u003eStaphylococcus aureus\u003c/em\u003e, compared to the 5\u0026ndash;10 mm zones observed for pure NiO-NPs. These results highlight the remarkable potential of S/N co-doping in transforming NiO into a highly efficient, multifunctional material for environmental remediation and biomedical applications.\u003c/p\u003e","manuscriptTitle":"Harnessing the Power of S/N Doped NiO Nanoparticles: Bandgap Tuning for Superior Photocatalytic and Antibacterial Performance","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-04-29 14:02:00","doi":"10.21203/rs.3.rs-6493877/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":"5a944d22-534d-43d4-8e70-63743977413a","owner":[],"postedDate":"April 29th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-05-19T09:53:11+00:00","versionOfRecord":[],"versionCreatedAt":"2025-04-29 14:02:00","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6493877","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6493877","identity":"rs-6493877","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}