An investigation of silver-nanoparticle-modified TiO₂ substrates for photocatalytic oxidation in wastewater treatment

The cleanliness of our planet is a critical global concern. Eco-friendly technologies are being actively investigated for sustainable energy production and pollutant elimination. The production of dyes from the chemical industry accounts for a relatively small proportion of the overall production globally, at ∼800 000 tons annually. Globally, the textile industry loses 10%–15% of synthetic dyes during various processes.¹ The expansion of India’s textile industry has significantly impacted both the national and global economies. These industries also produce a huge amount of waste in the form of fibers, sludge, and chemically contaminated waters.² Water pollution in the Cauvery River is a major problem in Tiruchirappalli, Tamil Nadu, India. This river has been selected as a primary river for studying the effects of pollution from various domestic and industrial activities. Approximately 33 stations along the river are used to monitor water quality as part of the Global Environment Monitoring System (GEMS). These stations were chosen based on the locations where municipal domestic sewage, industrial effluents, and other pollutants are discharged. Finding a means of degrading methylene blue dye in wastewater is a major priority. Photocatalysis combines photochemistry and catalysis to provide enhanced degradation mechanisms. Photocatalytic oxidation is employed across the globe to extract synthetic dyes from sewage due to their resistance to traditional elimination tactics. This process was developed as an effective remediation strategy to eliminate detrimental organic materials from water and air in an environmentally friendly and economical way. Photocatalytic oxidation is a feasible and efficient oxidation approach for thousands of organic waste materials, many of which biooxidize quickly and others that do so much more slowly.

There are two types of photocatalytic processes: homogeneous and heterogeneous. Precursors of transition metals such as copper, iron, and chromium are often used as catalysts.³ The formation of hydroxyl radicals is triggered by an increase in the oxidation state of metal ion complexes due to light and thermal conditions during this process. These radicals then interact with organic materials, leading to the destruction of toxic materials, particularly dyes. Heterogeneous photocatalysis, although not technically superior to homogeneous photocatalysis, can degrade a broader range of organic pollutants commonly found in wastewater. A good semiconductor photocatalyst should be photoactive, capable of using visible and/or near-UV light, photostable, affordable, and non-toxic.⁴ An oxide surface layer is applied to the metal component as part of the anodization process. Although anodizing is most frequently performed on aluminum, it can also be performed on titanium and magnesium substrates. Anodizing guarantees that the metal is corrosion-resistant and maintains its aesthetic appearance under all circumstances.⁵ Titanium may be anodized in acidic, neutral, or mildly basic solutions to create a thin, nonporous, transparent oxide layer with aesthetic and practical applications.⁶ Despite the oxide’s transparency, the components’ vibrant rainbow-like colors are caused by interference coloring.⁷ Coatings made of strongly alkaline anodizing solutions can be used to reduce corrosion resistance and prevent galling. The voltage primarily governs the oxide thickness.

Metal nanoparticles have a wide range of applications in numerous industries. Silver nanoparticles (Ag NPs) have been widely used for conductive, photonic, and medicinal purposes.⁸ Unfortunately, however, the utilization of silver-based nanomaterials is limited by their instability due to processes such as oxidation in oxygen-containing liquids. Silver is an abundant, cost-effective natural resource with impressive material properties.⁹ As a result, Ag NPs possess untapped potential and can be tailored to suit specific applications by adjusting their size.¹⁰ Ag NPs can be synthesized using evaporation condensation and laser ablation techniques, which allow for the production of large quantities of high-purity Ag NPs in an environmentally friendly manner that does not involve hazardous chemicals.¹¹ However, agglomeration presents a significant difficulty because capping agents are not used. Both methods also use more power, require complex equipment, and take longer to synthesize, all of which increase the cost of operation. By decreasing their metal salts, metallic NPs have been created chemically as a colloidal dispersion in an aqueous solution or organic solvent. Different metallic salts are utilized to create matching metal nanospheres, such as gold, silver, iron, zinc oxide, copper, palladium, and platinum.^12,13 Moreover, it is simple to alter the reducing and capping agents to obtain the desired Ag NP properties in terms of size distribution, shape, and dispersion rate.¹⁴ 

The Brust–Schiffrin synthesis or Turkevich methods are well-known conventional methods for synthesizing silver nanoparticles. In this work, the chemical reduction method is used to synthesize Ag NPs. The chemical reduction method yields a large number of particles of small size. This is important because the particle size plays an important role in the absorption of visible light. For the photocatalytic oxidation of the plasmonic surface of silver,¹⁵ sodium borohydride (NaBH₄) is used as a reducing agent,¹⁶ and polyvinylpyrrolidone (PVP) is used to protect the silver nanoparticles from growth and agglomeration.

Plasmonic resonance in Ag NPs occurs when the particles are exposed to light at a specific wavelength, which causes the electrons in the metal to oscillate. This oscillation generates an intense electric field near the particles, which can be used to catalyze chemical reactions. Free-oscillating metal electrons are excited by this visual phenomenon. Photons convey energy to bundles of electrons on the metal surface. The optical excitation of plasmons only occurs under light resonance conditions, or more specifically, under attenuated total reflection (ATR) circumstances, in which the energy of the photons precisely matches the quantum energy level of the plasmons. In the context of biological degradation, plasmonic resonance in silver nanoparticles can be used to generate reactive oxygen species (ROS). ROS are highly reactive and can oxidize and degrade a wide range of organic molecules, including pollutants and harmful biological compounds.¹⁷ Plasmonic resonance can be optimized for biological degradation by adjusting the size, shape, and composition of silver nanoparticles.¹⁷ For example, spherical nanoparticles with diameters between 20 and 100 nm are commonly used because of their high plasmonic resonance efficiency.¹⁸ Additionally, the use of core-shell nanoparticles, in which the silver core is coated with a thin layer of a different material,¹⁷ can improve the stability and performance of the particles in biological environments.

The potential applications of plasmonic resonance in silver nanoparticles for biological degradation are diverse and include the treatment of contaminated water and soil, the removal of pollutants from industrial effluent, and the remediation of contaminated air.¹⁹ Additionally, the use of plasmonic resonance in combination with other technologies, such as photocatalysis and bioremediation, can further enhance the effectiveness of biological degradation processes.¹⁹ The photocatalysis process, as demonstrated by the procedures and methods, is effective in breaking down methylene blue (MB) dye. This dye, which is a solid and odorless dark green powder at room temperature, transforms into a blue solution when dissolved in water.^20,21 Typically used in the textile industry, MB poses a health threat to human beings and microbes. It is carcinogenic and destructive to the environment.²¹ Attempts have previously been made to degrade MB dye using synthesized titanium dioxide substrates decorated with silver nanoparticles.²² 

In this study, titanium substrates were oxidized through an anodizing process to produce titanium dioxide, which acts as a photocatalyst for various purposes, such as the degradation of various organic pollutants.²³ Silver nanoparticles were synthesized using the chemical reduction method and coated on the titanium dioxide surface to increase its photocatalytic oxidation in the visible range.²⁴ Commonly, photocatalytic research for degrading dyes focuses on dyes such as methylene blue, rhodamine B, and methyl orange. The oxidative technique can destroy these elements entirely to generate end products that are not only harmless but also ineffective for further photo-oxidative destruction. When a photocatalyst such as titanium dioxide in a facade exposed to light, or the electrons within the valence band of titanium dioxide absorbs a certain amount of energy from radiant exposure, pollutants can be completely broken down into harmless compounds. Under light (usually ultraviolet or visible), an electron in the valence band of a photocatalyst, e.g., titanium dioxide (TiO₂), gains sufficient energy, absorbs photonic quanta, and is promoted to the conduction level, creating holes on top and forming electron–hole pairs. Electrons generated at the surface of a catalyst by light illumination can reduce the number of oxygen molecules adsorbed on its surface to form superoxide anion radicals. These photo‐generated holes might also selectively oxidize water molecules or hydroxide ions on the surface of the catalyst, generating highly reactive [OH]⁻ radicals. These include highly reactive oxygen species (such as hydroxyl radicals and superoxide anions), which can break down organic material. The reactive species produced earlier attack the organic compounds, such as MB dye, in the solution. Among these, hydroxyl radicals stand out as one of the most potent oxidizers, capable of cleaving complex organic compounds into smaller nontoxic byproducts for complete mineralization (conversion into CO₂, H₂O, and inorganic ions). Through these methods, the photocatalytic oxidation of degrading dyes takes place.

A literature survey on surface-enhanced photocatalytic oxidation using TiO₂ substrates decorated with plasmonic nanoparticles revealed that plasmonic nanoparticles can enhance the photocatalytic activity of TiO₂ by enhancing the absorption of visible light and generating electron–hole pairs.²⁵ Importantly, these substrates exist for a long time and can be reused several times.²⁶ Several types of plasmonic nanoparticles, such as gold, silver, copper, and zinc oxide, have been used for surface decoration. Surface-enhanced photocatalytic oxidation using TiO₂ nanoparticle glass substrates decorated with plasmonic nanoparticles has been used for various applications, such as water purification, CO₂ reduction, and organic pollutant degradation, with promising results.

The pure titanium substrate (Ti), electrodes, and polyvinylpyrrolidone (PVP) were purchased from Universal Scientific Appliances (Madurai, Tamil Nadu, India). The precursor [silver nitrate (AgNO₃)], electrolytes [sulfuric acid (H₂SO₄)], and reducing agent [sodium borohydride (NaBH₄)] were purchased from Merck-Sigma. Stainless steel electrodes and alligator clips were purchased from BSL Electronics Stores, Tiruchirappalli, Tamil Nadu. Nitric acid (HNO₃) and acetone were used as cleaning agents throughout the process. Double-distilled water (DDW) was used as the solvent in the chemical reduction process. Boro-silicate glass tubes and beakers were used for all synthesis processes.

To confirm the formation of silver nanoparticles in the colloidal solution, it was tested using DDW with a laser beam.²⁷ The colloidal solution and DDW were collected in two separate beakers. A laser beam was allowed to pass through the colloidal solution, and the reflection of light was analyzed, as the presence of nanoparticles inhibits the reflection of light. Hence, when the laser beam passed through the DDW, there was no light reflection along its path, as shown in Fig. 3. A colloidal suspension always reflects and refracts light; thus, a clear pathway can be observed. This indicates the presence of colloidal nanoparticles in the solution.

The titanium (Ti) sheet was cut into 3 × 1 cm² specimens and degreased with acetone. The specimens were then etched in diluted nitric acid (HNO₃) to form a uniform oxide layer on the titanium substrate. During the anodizing process, diluted sulfuric acid was used as an electrolyte at a concentration of 0.05 M. A stainless-steel plate was used as the cathode. Figures 4(a) and 4(b) show the titanium substrate and the electrolyte setup.

Two 30 V DC regulator power supplies were used for the anodization process. Stainless steel was used for the negative terminal of the regulator, and the positive terminal was connected to a titanium substrate using alligator clips. Extra measures were implemented to prevent any contact between the cathode and anode. Figure 5 shows the anodizing process. Once the anode material was dipped in the electrolyte, the surface color of the titanium changed, indicating the formation of an oxide layer²⁸ on the titanium substrate. The color of the anodized titanium was due to color interference. The anodizing procedure produced a thin layer of titanium oxide,²⁹ in which the white light that hit the oxide was partially reflected, partially transmitted, and partially refracted. The oxide layer reflected most of the light that reached the metal/oxide interface. This mechanism resulted in a phase shift and numerous reflections. The oxide layer’s thickness played a crucial role in determining the amount of light absorbed and reflected. Specifically, the light reflected off the oxide’s surface interfered with the light that had passed through the oxide and was then reflected off the metal surface.³⁰ This interference caused certain wavelengths (colors) to be in phase and enhanced while others were out of phase and dampened.³¹ Consequently, the observed color was used as an indicator of the oxide layer’s thickness.³² 

Coating the TiO₂ substrate with silver nanoparticles required dipping the substrate (2 cm in length and 1 cm in width) in a colloidal solution for ∼24 h. The colloidal solution (20 ml) was then placed in a beaker. Figure 6 shows the coating of the TiO₂ substrate with Ag NPs. The TiO₂ layer thickness was measured to be ∼200 nm using a profilometer.

The silver nanoparticle-modified TiO₂ substrates were characterized using several advanced techniques to evaluate their optical, structural, and morphological properties. UV-visible spectroscopy was performed using a Perkin Elmer Lambda 365 UV-visible spectrophotometer covering a range of 190 to 1100 nm at the Archbishop Casimir Instrumentation Center (ACIC), St. Joseph’s College, Tiruchirappalli.³³ This analysis provided absorbance spectra indicative of the surface plasmon resonance (SPR) of the silver nanoparticles, confirming successful modification. X-ray diffraction (XRD) analysis was conducted using a PANalytical X’Pert3 powder diffractometer with a SAXS attachment at the Heber Analytical Instrumentation Facility (HAIF), Bishop Heber College, Trichy, to determine the crystalline phases and assess any changes in crystallinity post-modification. A Zeiss EVO 18 scanning electron microscope (SEM) at ACIC was employed to observe the surface morphology and nanoparticle distribution on the TiO₂ substrates. The SEM images revealed detailed microstructural features, illustrating the dispersion of silver nanoparticles on the TiO₂ surface. By interacting with the sample, the electrons generate signals that are detected and used to create a highly magnified image of the surface topography and composition.

UV spectroscopy is a technique in which the absorbance of a substance is determined using ultraviolet light. Ag NPs have unique optical properties owing to their small size and surface plasmonic resonance (SPR), which can be characterized using UV-vis spectroscopy.²² 

Ag NPs typically exhibit a characteristic SPR peak at around 350–450 nm in the UV-visible region, as shown in Fig. 7. This is attributed to the collective oscillation of conduction band electrons on the surface of the nanoparticles. Previous literature has also confirmed that silver nanocolloids produce a UV excitation peak between 350 and 450 nm. The present analysis shows that the respective sample’s absorption range falls between 390 and 410 nm.

The diameter of the silver nanoparticles, which is depressed in the solution, plays a major role in SPR because it determines the resonance condition, affecting how efficiently the nanoparticles absorb and scatter light. It works as a catalyst to absorb visible light and enhance the photocatalytic reaction. Silver nanoparticles with an average hydrodynamic diameter of 250 nm were obtained using the particle size analyzer technique, as shown in Fig. 8. The polydispersity index was ∼0.306. The Ag NP photocatalytic reactions were enhanced due to the increased light absorption (due to SPR) and the generation of reactive oxygen species (ROS) like hydroxyl radicals (·OH) and superoxide radicals (O2·−), which are highly reactive and can break down organic compounds. A polydispersity index (PDI) of 0.306 shows that the sizes of the particles were moderately spread out. This implies that the particles were quite uniform in size with some variability. The optical properties and photocatalytic efficiency of nanoparticles depend on their average size and PDI. As a result, larger particles or those having a wider size distribution can exhibit different SPR characteristics, which may influence the enhancement of photocatalytic reactions.

XRD is a highly effective analytical method for examining the atomic-scale structures of materials. By employing this technique, the structural parameters of the Ti substrate were determined. The dislocation density was 2.52 × 10⁹ lines/m², the lattice strain was ∼0.091 16%, and the average crystalline size was ∼28.67 nm. The crystal’s preferred orientation at the (100) plane corresponds to a simple cubic structure, the (002) plane corresponds to a body-centered cubic (BCC) structure, and the (101) and (102) planes correspond to a face-centered cubic (FCC) structure, as shown in Fig. 9(a).

The formation of a TiO₂ layer on the Ti substrate after anodization and subsequent annealing was confirmed through x-ray diffraction (XRD) patterns. The characteristic diffraction peaks corresponding to anatase TiO₂ in the XRD pattern were analyzed. The most prominent peaks for anatase TiO₂ were generally found at 2θ values around (101) at 25.3°, (004) at 37.8°, (200) at 48.1°, (211) at 54.0°, and (204) at 62.7°. In the XRD pattern in Fig. 9(b) for the anodized Ti substrate, a significant peak can be observed at around 25° 2θ, which corresponds to the (101) plane of anatase TiO₂. This confirms the presence of the anatase phase after annealing. The XRD pattern in Fig. 9(a) is for the pure Ti substrate before anodization. The characteristic peaks for titanium (Ti) are observed at (100) at ∼35.1°, (002) at ∼38.4°, and (101) at ∼40.2°. By comparing pattern (a) with pattern (b), the presence of new peaks in pattern (b) can be observed. In particular, the peak around 25° 2θ indicates the formation of a TiO₂ layer. The formation of anatase TiO₂ can be confirmed if the observed peaks in the XRD pattern (a) match the standard diffraction data for anatase TiO₂ (PDF card 21-1272). The XRD pattern of the anodized Ti substrate [pattern (a)] shows a prominent peak at 25° 2θ, which corresponds to the (101) plane of anatase TiO₂. This confirms the successful formation of an anatase TiO₂ layer after anodization and annealing at 450 °C.

After anodization, coatings were formed on the surface of the Ti substrate. Titanium dioxide was developed, and its structural parameters were determined. The dislocation density was 1.9427 × 10⁹ lines/m², the lattice strain was ∼0.070 30%, and the average crystalline size was ∼3.76 nm. The preferred orientations were at the (101), (200), (220), and (301) planes and commonly associated with the face-centered cubic structure, as shown in Fig. 10. The results were compared with JCPDS, USA file No: 75-1537. The parameters determined using these formulae were as follows:

• •Scherrer’s equation for the crystallite size: $D=Kλβ⁡cos⁡θ=3.76nm$⁠.

• •Dislocation density: $σ=1D2$ = 1.9427 × 10⁹ lines/m².

• •Lattice strain: $ε=β4⁡tan⁡θ$ = 0.070 30%

Electron microscopy that uses a focused beam of high-energy electrons to produce images of a sample’s surface is known as scanning electron microscopy (SEM).³⁴ By interacting with the sample, the electrons generate signals that are detected and used to create a highly magnified image of the surface topography and composition.³⁵ Many nanotube structures in TiO₂ substrates can be observed in SEM images. The nanotube structures in TiO₂ substrates have unique properties that make them useful for various applications. They have a high surface area and can be used as efficient photocatalysts and adsorption materials.³⁶  Figure 11 shows the morphology and size of the investigated nanotubes, and the results indicate that the material subjected to analysis is applicable for the photocatalytic mechanism; hence, it can degrade dye molecules to a greater extent.

Titanium dioxide coated with silver nanoparticles was immersed in an MB solution and kept under sunlight for 2.30 hours. UV-visible spectroscopy was performed for the control and degraded solutions, and the results are shown in Fig. 11. The two values were then merged, and a graph was plotted. From Figs. 12 and 13, it is clear that the methylene blue dye was completely degraded after exposure to sunlight irradiation. The absorption spectra of methylene blue are distinguished by three main bands, two of which are in the UV spectrum (l_max = 300 nm and l_max = 250 nm) and one of which is visible (l_max = 661.8 nm). The most significant band in this case was located at 661.8 nm (corresponding to azo dye content), as the azo dye class (–N=N–) is the most prevalent chromophore group found in wastewater from the textile industry. The azo dye concentration was greatly degraded by titanium dioxide, with its absorbance rate changing from 0.472 22 to 0.089 34 a.u. The absorption peak around 300 nm was also reduced, which can be attributed to the degradation of aromatic structures within the MB dye. The photocatalytic process, facilitated by the plasmonic resonance of silver nanoparticles, likely leads to the formation of intermediate degradation products, such as leucomethylene blue, which have different absorption characteristics.

In addition, there is a large difference between the UV excitation peaks and the absorbance peak after 150 min in sunlight, which indicates that the intensity of the MB dye in the solution decreased rapidly after exposure to sunlight. This process efficiently removed methylene blue dye from the wastewater, and the rapid reaction of the photocatalyst proved to be an effective method for wastewater treatment.³³ Hence, the degradation of the MB dye using the titanium substrate worked well and successfully exhibited a photocatalytic mechanism.

Photocatalysis, particularly in the context of MB degradation, involves a complex series of chemical reactions facilitated by a semiconductor photocatalyst like titanium dioxide (TiO₂) under illumination. TiO₂ is commonly used because it has a bandgap that matches well with the energy of ultraviolet (UV) or visible light, enabling it to generate electron–hole pairs upon light absorption. When TiO₂ absorbs photons with sufficient energy (equal to or greater than its bandgap), electrons in its valence band are excited to the conduction band, leaving behind positively charged holes in the valence band. These electron–hole pairs (e⁻ and h⁺) are crucial to the photocatalytic process. MB is a widely used dye in various industrial processes and exists in its oxidized form with a positively charged phenothiazine chromophore. In the presence of TiO₂ and under illumination, MB interacts primarily with the electrons that are excited into the conduction band of TiO₂. These electrons are highly reducing and have sufficient energy to transfer to the MB molecules, thereby reducing them. The reduction process converts MB into its reduced form, known as leucomethylene blue (LMB). LMB is colorless and lacks the chromophore responsible for the characteristic blue color of MB. This reduction step is crucial because it renders the dye molecule more susceptible to subsequent degradation.²⁴ Simultaneously, the holes generated in the valence band of TiO₂ can react with water molecules or other substances present in the solution, leading to the formation of highly reactive oxygen species (ROS) such as hydroxyl radicals (·OH) and superoxide ions (O₂⁻). These ROS are strong oxidizing agents and play a significant role in breaking down the organic molecules present, including the intermediates and by-products formed during the degradation of MB. The degradation pathway of LMB typically proceeds through a series of intermediate steps, where the complex organic structure of the dye molecule is gradually broken down into smaller molecules. This process may involve the cleavage of aromatic rings, oxidation of side chains, and eventually complete mineralization into carbon dioxide (CO₂), water (H₂O), and inorganic ions like sulfate (SO₄²⁻) and nitrate (NO₃⁻), depending on the specific conditions and the exact pathway followed.

The overall effectiveness of photocatalytic degradation depends on several factors, including the type and concentration of the photocatalyst, the intensity and wavelength of the light source, the pH of the solution, and the presence of any co-catalysts or electron donors. Optimizing these parameters can enhance the efficiency of MB degradation and make photocatalysis a viable method for treating wastewater contaminated with organic dyes.

In summary, the photocatalytic degradation of MB involves reduction processes facilitated by TiO₂ photocatalyst-generated electrons, leading to the conversion of MB into its colorless form, LMB. Concurrently, oxidizing holes in TiO₂ generate ROS that aid in the breakdown of LMB and its intermediates, ultimately resulting in the detoxification and degradation of the dye molecules in wastewater treatment applications. The Chemical Oxygen Demand (COD) value decreased from 157 mg/l initially to 21 mg/l after treatment, reflecting the effective breakdown of the MB dye into simpler, less harmful substances. Similarly, the Total Organic Carbon (TOC) value decreased from 103 mg/l initially to 16 mg/l after treatment, further confirming the substantial degradation of the dye. These reductions in the COD and TOC values underscore the effectiveness of the TiO₂ substrate decorated with silver nanoparticles in degrading MB dye under sunlight and validate its potential for practical applications in wastewater treatment.

This study has demonstrated the photocatalytic oxidation of methylene blue (MB) dye using a TiO₂ substrate decorated with silver nanoparticles. The results showed that the decorated TiO₂ substrates exhibited significantly higher photocatalytic activity in sunlight than undecorated substrates. The plasmonic nanoparticles were found to enhance the absorption of visible light, resulting in increased electron–hole separation and improved photocatalytic activity.

This study also investigated the effect of the nanoparticle size and concentration on the photocatalytic activity of decorated substrates. The results showed that smaller nanoparticles and higher concentrations resulted in higher photocatalytic activity. A titanium plate was oxidized using a controlled emission-free electrolysis method, where the deposition layer thickness could be fine-tuned. Titanium oxides usually exhibit adequate bandgap levels for photoconductivity. This effect can be enhanced by coating the TiO₂ with Ag nanoparticles. The plasmonic-enhanced TiO₂ substrate was then used to treat MB-dyed wastewater for the photolytic degradation of methylene blue into leucomethylene blue. This conversion is facilitated by free electrons, which can be explained by a phenomenon called the electron relay effect. The novelty of this research is that, unlike conventional powder-based or liquid-based solutions, the TiO₂ strip used here can be reused multiple times and shaved after each use, thus reducing costs at industrial scales. The findings of this study suggest that plasmonic nanoparticle-decorated TiO₂ substrates have great potential for use in photocatalytic oxidation, representing an important step toward a healthier and cleaner environment.

This study contributes to the general understanding of the role of plasmonic nanoparticles in enhancing the photocatalytic activity of TiO₂ substrates and provides a basis for further research in this area. These results have important implications for the development of new and efficient photocatalytic systems that can contribute to a more sustainable future.

The authors thank, DST-FIST, Government of India for funding toward infrastructure and instrumentation facilities at ACIC, St. Joseph’s College (Autonomous), Tiruchirappalli – 620002, India.

The authors have no conflicts to disclose.

The corresponding author will provide the datasets produced during and/or analyzed during the current investigation upon reasonable request.

Jackson Joseph Arulsamy completed his Master of Science in physics at St. Joseph’s College (Autonomous) and was awarded his degree by Bharathidasan University, Tiruchirappalli, in 2023. He conducted his research under the supervision of Assistant Professor Dr. H. Joy Prabu. His current research interests include materials for energy storage and materials for sustainable energy.

Joy Prabu Henry Prunier is an Assistant Professor of Physics at St. Joseph’s College (Autonomous), Tiruchirappalli, Tamil Nadu, India. He received his Ph.D. in physics in 2017 from Bharathidasan University, Tiruchirappalli. His research interests include the synthesis of nanomaterials for energy storage and wastewater treatment. He has published 35 scientific articles in peer-reviewed journals, contributed chapters to several books, and has filed two patents in his field of research.

Felix Sahayaraj Arockiasamy is a renowned expert in the field of natural fiber composites, with a focus on fiber characterization, composite preparation, and the use of agricultural waste in biocomposites. Holding a Ph.D. from Anna University, Chennai, he has made significant contributions to polymer composites, bioresins, and the extraction of cellulose nanocrystals. His extensive research, documented in more than 65 research publications, delves into various aspects of composite materials, including their mechanical, thermal, and acoustic properties.

Johnson Irudhayaraj is the Head and Associate Professor of the Department of Physics at St. Joseph’s College (Autonomous), Tiruchirappalli. He holds a Ph.D. in Chemical Physics from Bharathidasan University and completed a post-doctoral fellowship in materials science at the University of Coimbra, Portugal. With extensive experience in ultrasonics, chemical physics, materials science, and nanotechnology, his research focuses on advanced materials and their applications in energy storage and wastewater treatment. As a prolific author and reviewer, he has written numerous articles for peer-reviewed journals and authored chapters in various books within his field of research. He has received many international awards for his significant contributions to his field with practical applications in materials science and technology.

Ebenezer Thaninayagam, a postgraduate student at the University of Birmingham, has worked on photocatalytic materials and supercapacitors. He is currently working on electrospinning polymers with inert solvents and studying the underlying physics of bead formation and alignment. His research interests include superconductors, phase-changing materials, and materials for green energy. He has authored eight research articles and two books.

Gopi Rajakannu Ravi is a doctoral student in the Faculty of Mechanical and Electrical Engineering (FIME) at the Universidad Autónoma de Nuevo León (UANL), Mexico. His research expertise spans advanced materials, including MXene, Metal-Organic Frameworks (MOFs), and nanomaterials, with a particular focus on their applications in supercapacitors. Gopi’s work has gained recognition in the scientific community, reflecting his commitment to developing innovative energy storage solutions. He is also actively engaged in publishing research papers and contributing to the advancement of materials science.

Snowlin Venice Selvam completed her Master of Science in physics at St. Joseph’s College (Autonomous), Tiruchirappalli, where she built a strong foundation in materials science and nanotechnology. She is currently advancing her studies through a Ph.D. program at the same institution, working under the esteemed guidance of Dr. H. Joy Prabu. Her doctoral research is focused on innovating and applying advanced materials specifically designed to enhance the methods involved in wastewater treatment. She has published five research articles in reputed journals and remains actively engaged in expanding her research contributions in materials science and nanotechnology.