Sol-Gel-Assisted Microwave-Derived Synthesis of Anatase Ag/TiO2/GO Nanohybrids toward Efficient Visible Light Phenol Degradation

Visible-light-activated antibacterial and antipollutant properties of biocompatible Cu-doped and Ag-decorated TiO2 nanoparticles

Optical and photocatalytic restrictions of anatase TiO2 nanoparticles (Nps) limit their potential applications, as antipollutant and antibacterial agents for sanitary applications, to the UV spectral region. While modification with transition metals extends the absorption capacity to the visible light spectrum, often undermines the photocatalysts' biocompatibility due to toxic ion leaching. In this study, we synthesized Cu-doped and Ag-decorated TiO2 photocatalysts by employing solvothermal (ATiO2:Cu) and sol-gel synthetic procedures (BTiO2:Ag), respectively. We acquired TiO2 Nps modified with three percentages of either Cu or Ag content, to examine the potential differentiation of their structural, photocatalytic, and biological impact. Comprehensive structural characterization supports the prevailing anatase crystalline structure of bare and modified titania nanostructures, while morphological differences are demonstrated among the different samples. Optical response in the visible region of ATiO2:Cu Nps stems from band gap narrowing and lattice-defect generation, while plasmonic effects are at play for BTiO2:Ag Nps. Their photocatalytic potential under visible light irradiation, originated from low-energy LED lamps commonly found in indoor spaces, was verified after monitoring the successful enhancement of methylene blue (MB) degradation rate. Safety assessment on immortalized healthy human keratinocyte cell line (HaCaT) revealed their biocompatibility up to a certain concentration, while reactive oxygen species (ROS) production was intensified after light irradiation. The visible-light-induced photocatalytic-driven antibacterial activity was confirmed against both gram-positive Staphylococcus aureus and gram-negative Escherichia coli.

Self-Assembly Regulated Photocatalysis of Porphyrin-TiO2 Nanocomposites

Photoactive artificial nanocatalysts that mimic natural photoenergy systems can yield clean and renewable energy. However, their poor photoabsorption capability and disfavored photogenic electron-hole recombination hinder their production. Herein, we designed two nanocatalysts with various microstructures by combining the tailored self-assembly of the meso-tetra(p-hydroxyphenyl) porphine photosensitizer with the growth of titanium dioxide (TiO2). The porphyrin photoabsorption antenna efficiently extended the absorption range of TiO2 in the visible region, while anatase TiO2 promoted the efficient electron-hole separation of porphyrin. The photo-induced electrons were transferred to the surface of the Pt co-catalyst for the generation of hydrogen via water splitting, and the hole was utilized for the decomposition of methyl orange dye. The hybrid structure showed greatly increased photocatalytic performance compared to the core@shell structure due to massive active sites and increased photo-generated electron output. This controlled assembly regulation provides a new approach for the fabrication of advanced, structure-dependent photocatalysts.

Biosynthesized and chemically synthesized Ag/TiO2 nanocomposites: Effect of reaction parameters on synthesis using watermelon rind extract and comparative analysis

This work synthesized Ag/TiO2 nanocomposite via an aqueous reduction method using a green and chemical reducing agent. Citrullus lanatus (watermelon) rind extract (WMRE) and sodium borohydride (NaBH4) were used as the reducing agents during green synthesis and chemical synthesis, respectively. During green synthesis, a pH of 12, a reaction time of 45 min, and an operating temperature of 100 °C yielded the best visible light activity. The biosynthesized and chemically-synthesized Ag/TiO2 were compared using UV-Vis spectroscopy, X-ray fluorescence spectroscopy (XRF), X-ray diffraction spectroscopy (XRD), Fourier transform infrared spectroscopy (FTIR), energy dispersive spectroscopy-scanning electron microscopy (EDS-SEM) and transmission electron microscopy (TEM). Synthesis using WMRE yielded spherical Ag nanoparticles modified on the surface of TiO2 nanoparticles. The Ag nanoparticles had enhanced monodispersity with an average diameter of 7.48 ± 4.06 nm. Therefore, the developed WMRE green synthesis method provides a simple, less chemical-intensive, and effective alternative to chemical synthesis.

Multicomponent Photocatalytic-Dispersant System for Oil Spill Remediation

In the present work, the potential application of a fabricated halloysite nanotubes-Ag-TiO2 (HNT-Ag-TiO2) composite loaded with a binary surfactant mixture made up of lecithin and Tween 80 (LT80) in remediating oil spillages was examined. The as-prepared Ag-TiO2 that was used in the fabrication of the HNT-Ag-TiO2-LT80 composite was characterized by X-ray diffraction, Raman spectroscopy, UV-vis and diffuse reflectance spectroscopy, CV analyses, and SEM-EDX. The synthesized composite was also characterized by thermogravimetric analysis, Fourier-transform infrared spectroscopy, and scanning electron microscopy-energy dispersive X-ray spectroscopy. The synthesized composite was active in both the UV and visible light regions of the electromagnetic spectrum. The oil-remediating potential of the as-prepared composite was examined on crude oil, and aromatics and asphaltene fractions of crude oil. The composite was able to reduce the surface tension, form stable emulsions and smaller oil droplet sizes, and achieve a high dispersion effectiveness of 91.5%. A mixture of each of the crude oil and its fractions and HNT-Ag-TiO2-LT80 was subjected to photodegradation under UV light irradiation. The results from the GC-MS and UV-vis analysis of the photodegraded crude oil revealed that the photocatal composite was able to photodegrade the crude oil, aromatics, and asphaltene fractions of crude oil with the formation of intermediate photodegradation products depicting that the HNT-Ag-TiO2-LT80 has a potential as an oil spill remediation material.

Daylight Photoactive TiO2 Sol-Gel Nanoparticles: Sustainable Environmental Contribution

Visible-light-photoactive titania micro- or nanoparticles excel in a wide range of industrial areas, particularly in environmental remediation. The sol-gel methodology is one pivotal technique which has been successfully used to synthesize either crystalline and amorphous TiO₂ micro- and nanoparticles due to its outstanding chemical simplicity and versatility, along with the green chemistry approach. This short review aims to collect and discuss the most recent developments in visible-light-photoactive titania-based nanoparticles in the environmental remediation area. Titania co-doping, titania composite design, and, recently, amorphous networks have been the most used strategies to address this goal. Finally, a prediction regarding the future of these fields is given.

Microwave assisted sol-gel approach for Zr doped TiO2 as a benign photocatalyst for bismark brown red dye pollutant

A microwave supported sol-gel approach was developed in this study to fabricate Zr-doped TiO2 mesoporous nanostructures for efficient photocatalytic activity on bismark brown red (BBR) dye under visible light illumination. Sophisticated analytical techniques such as X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), high resolution transmission electron microscopy (HRTEM), field emission scanning electron microscopy (FESEM) with energy dispersive X-ray spectroscopy (EDX), X-ray fluorescence analysis (XRF), Fourier transform infrared (FT-IR), ultraviolet-visible diffuse reflectance (UV-vis-DRS) spectroscopy and Brunauer-Emmet-Teller (BET) surface area analyses were used to obtain their structural, electrical: optical and spectroscopic characteristics. The analysis results revealed that the developed nanostructures exhibited strong broad absorption in the visible region with good adsorption capacity and thus enhanced photocatalytic performance. The average crystallite size was found to be 12.5 nm (UTO), 6.4 nm (ZT4), and 4.7 nm (ZT4M4) respectively. The nanocatalysts (ZT4M4) showed a decrease in bandgap and particle size with an increase in the surface area of the Zr-TiO2 nanoparticles (119 m2 g-1). In comparison to previous studies on the photocatalytic degradation of BBR dye under visible light irradiation employing Ni-S co-doped (110 min), Cu-doped TiO2 (75 min), etc., ZT4M4 exhibited a remarkable degradation rate of 99% in 50 minutes. This may be due to the hydroxyl radicals being the principle reactive species responsible for the BBR dye oxidative degradation. The present study showed that ZT4M4 was found to be the best photocatalyst for the BBR dye degradation under the optimal conditions.

Nile Tilapia Skin Impregnated with Antibacterial Silver/Titanium Dioxide Compounds

The development of alternative (and free-of-antibiotics) antibacterial and antibiofilm agents is an important strategy to circumvent the resistance of bacteria to antibiotics. Herein, we explore the production of mixed oxides by incorporating silver nanoparticles in titanium dioxide as a silver concentration-dependent antibacterial agent that is further incorporated in Tilapia fish skin (a promising prototype of xenograft), integrating the antibacterial activity of mixed oxide into the intrinsic properties of Tilapia skin. The antibiofilm activity of samples prepared with high concentrations of silver (10 wt% of precursor AgNO3) has been considered a good antibiofilm response. The influence of silver content is also observed with respect to the minimum bactericidal concentration, which is reduced to 3.13 mg/mL with a characteristic kill time in the order of 30 min that is associated with antibiofilm activity in biofilm-forming strains of Staphylococcus aureus. These results indicate that modified Tilapia fish skin acquires antibacterial behavior and can be explored for xenografts with prospective applications in the light-dependent actuation of TiO2-based compounds.

Multifunctional nanocomposite based on polyvinyl alcohol, cellulose nanocrystals, titanium dioxide, and apple peel extract for food packaging

Although polyvinyl alcohol (PVA) is a potential biodegradable food packaging material, it has several critical limitations: low mechanical strength, poor ultraviolet (UV) and water vapor barrier properties, and lack of antioxidant and antimicrobial properties. Previous studies have used cellulose nanocrystals (CNCs) to improve the mechanical and water vapor barrier properties of the PVA matrix. In this study, a multifunctional nanocomposite for food packaging applications was developed by incorporating titanium dioxide (TiO₂) and apple peel extract (APE) into a PVA/CNC matrix. The combination of TiO₂ and APE in the nanocomposites not only enhanced multifunctionality but also improved mechanical and barrier properties. The mechanical strength and water vapor barrier properties of PVA/CNC/TiO₂/APE (5 wt% TiO₂ and 20 wt% APE in the PVA/CNC matrix containing 5 wt% of CNCs) increased by 49.9 % and 36.6 % compared to PVA. Furthermore, PVA/CNC/TiO₂/APE exhibited an excellent UV barrier (UV-protection factor of 1012.73) and high antioxidant and antimicrobial properties. In food packaging tests with fresh cherry tomatoes and potatoes, PVA/CNC/TiO₂/APE effectively protected samples from external influences and prolonged their self-life, demonstrating the potential use of this nanocomposite as a biodegradable and multifunctional food packaging material.

Plasmon Effect of Ag Nanoparticles on TiO2/rGO Nanostructures for Enhanced Energy Harvesting and Environmental Remediation

We report Ag nanoparticles infused with mesosphere TiO₂/reduced graphene oxide (rGO) nanosheet (TiO₂/rGO/Ag) hybrid nanostructures have been successfully fabricated using a series of solution process synthesis routes and an in-situ growth method. The prepared hybrid nanostructure is utilized for the fabrication of photovoltaic cells and the photocatalytic degradation of pollutants. The photovoltaic characteristics of a dye-sensitized solar cell (DSSC) device with plasmonic hybrid nanostructure (TiO₂/rGO/Ag) photoanode achieved a highest short-circuit current density (J_SC) of 16.05 mA/cm², an open circuit voltage (V_OC) of 0.74 V and a fill factor (FF) of 62.5%. The fabricated plasmonic DSSC device exhibited a maximum power conversion efficiency (PCE) of 7.27%, which is almost 1.7 times higher than the TiO₂-based DSSC (4.10%). For the photocatalytic degradation of pollutants, the prepared TiO₂/rGO/Ag photocatalyst exhibited superior photodegradation of methylene blue (MB) dye molecules at around 93% and the mineralization of total organic compounds (TOC) by 80% in aqueous solution after 160 min under continuous irradiation with natural sunlight. Moreover, the enhanced performance of the DSSC device and the MB dye degradation exhibited by the hybrid nanostructures are more associated with their high surface area. Therefore, the proposed plasmonic hybrid nanostructure system is a further development for photovoltaics and environmental remediation applications.

Co, Cu, Fe, and Ni Deposited over TiO2 and Their Photocatalytic Activity in the Degradation of 2,4-Dichlorophenol and 2,4-Dichlorophenoxyacetic Acid

Pure TiO2 synthesized by the sol-gel method and subsequently deposited at 5% by weight with Co, Cu, Fe, and Ni ions by the deposition–precipitation method were studied as photocatalysts. The nanomaterials were analyzed by SEM, TEM, UV-Vis DRS, DRX, Physisorption N2, and XPS. The SEM and TEM images present a semi-spherical shape with small agglomerations of particles and average size between 63 and 65 nm. UV-Vis results show that a reduction below 3.2 eV exhibits a redshift displacement and increment in the optical absorption of the nanoparticles promoting the absorption in the UV-visible region. XRD spectra and analysis SAED suggest the characteristic anatase phase in TiO2 and deposited materials according to JCPDS 21-1272. The specific surface area was calculated and the nanomaterial Ni/TiO2 (21.3 m2 g−1) presents a slight increment when comparing to TiO2 (20.37 m2g−1). The information generated by the XPS spectra present the deposition of metallic ions on the support and the presence of different valence states for each photocatalyst. The photocatalytic activity was carried out in an aqueous solution with 80 mg L−1 of 2,4-D or 2,4-DCP under UV light (285 nm) with 100 mg L−1 of each photocatalysts for 360 min. The nanomaterial that presented the best efficiency was Ni/TiO2, obtaining a degradation of 85.6% and 90.3% for 2,4-D and 2,4-DCP, respectively. Similarly, this material was the one that presented the highest mineralization, 68.3% and 86.5% for 2,4-D and 2,4-DCP, respectively. Photocatalytic reactions correspond to the pseudo-first-order Langmuir–Hinshelwood model.

Removal of chemical and microbial water pollutants by cold plasma combined with Ag/TiO2-rGO nanoparticles

This study aimed to investigate the synergistic effect of the cold atmospheric plasma (CAP) and heterogeneous photocatalytic processes in an aqueous solution to enhance water purification efficacy and reduce the energy cost required by CAP. 0.1% Ag/TiO₂-reduced graphene oxide (rGO) nanoparticles (NPs) photo-composite were prepared and fully characterized. Data showed that Ag nanoparticles and the rGO play an important role in increasing the efficiency of the whole treatment process and the photo-composite (0.1% Ag/TiO₂-1% rGO at 400 °C) revealed the highest phenol removal rate with excellent reusability. Also, complete inactivation (~ 5log₁₀ reduction) of both E. coli and S. aureus by NPs was observed without CAP exposure, whereas a minimal effect (0.1-0.5 log₁₀) on viruses (Adenovirus (AdV), rotavirus, and ɸX174) was observed after 10 min incubation. Interestingly, the photocatalytic virus inactivation test was promising, as it resulted in > 4.7log₁₀ reduction of AdV at 2 min treatment, whereas < 1log₁₀ could be reduced using only CAP at the same treatment time. Accordingly, we believe that this work could provide new insights into how the synergy between CAP and 0.1% Ag/TiO₂-1% rGO photo-composite in aqueous media imposes a great potential for environmental applications, such as water purification and microbial inactivation.

Synthesis of Electrospun PAN/TiO2/Ag Nanofibers Membrane As Potential Air Filtration Media with Photocatalytic Activity

The PAN/TiO2/Ag nanofibers membrane for air filtration media was successfully synthesized with electrospinning method. The morphology, size, and element percentage of the nanofiber were characterized by a scanning electron microscopy-energy dispersive spectroscopy, while X-ray fluorescence and FTIR were used to observe the chemical composition. The water contact angle and UV-vis absorption were measured for physical properties. Performance for air filtration media was measured by pressure drop, efficiency, and quality factor test. TiO2 and Ag have been successfully deposited in nonuniform 570 nm PAN/TiO2/Ag nanofibers. The nanofiber membrane had hydrophilic surface after TiO2 and Ag addition with a water contact angle of 34.58°. UV-vis data showed the shifting of absorbance and band gap energy of nanofibers membrane to visible light from 3.8 to 1.8 eV. The 60 min spun PAN/TiO2/Ag nanofibers membrane had a 96.9% efficiency of PM2.5, comparable to results reported in previous studies. These properties were suitable to be applied on air filtration media with photocatalytic activity for self-cleaning performance.

Development of Gold Nanoparticle-Based SERS Substrates on TiO2-Coating to Reduce the Coffee Ring Effect

Hydrophilic surface-enhanced Raman spectroscopy (SERS) substrates were prepared by a combination of TiO₂-coatings of aluminium plates through a direct titanium tetraisopropoxide (TTIP) coating and drop coated by synthesised gold nanoparticles (AuNPs). Differences between the wettability of the untreated substrates, the slowly dried Ti(OH)₄ substrates and calcinated as well as plasma treated TiO₂ substrates were analysed by water contact angle (WCA) measurements. The hydrophilic behaviour of the developed substrates helped to improve the distribution of the AuNPs, which reflects in overall higher lateral SERS enhancement. Surface enhancement of the substrates was tested with target molecule rhodamine 6G (R6G) and a fibre-coupled 638 nm Raman spectrometer. Additionally, the morphology of the substrates was characterised using scanning electron microscopy (SEM) and Raman microscopy. The studies showed a reduced influence of the coffee ring effect on the particle distribution, resulting in a more broadly distributed edge region, which increased the spatial reproducibility of the measured SERS signal in the surface-enhanced Raman mapping measurements on mm scale.

Synthesis of enhanced corrosion resistant Fe-B-C-Ti amorphous ribbons and evaluation of their photodegradation efficiency under light irradiation

Fe-based amorphous alloys have been found to be very efficient in the degradation of water pollutants due to their unique atomic arrangements with long-range disordered structure. In this work, Fe-B-C-Ti amorphous ribbons were successfully synthesized and showed high catalytic efficiency in the degradation of methylene blue (MB) under simulated sunlight and across a wide pH range. The catalytic efficiency was evaluated under different conditions to optimize the degradation performance. The amorphous ribbon Fe₇₅B₁₀C₁₀Ti₅ was found to exhibit the highest photocatalytic activity as explained by its optical and photoelectrochemical properties. It can degrade MB completely with low Fe-leaching and significant recyclability at pH close to a neutral range (pH 5). The degradation mechanisms can be explained in terms of photocatalytic activity along with the galvanic cell effect which contributed to the efficient MB degradation. This work provides a comprehensive idea for the synthesis of amorphous alloys by optimizing their elemental composition and also explains the catalytic activity of partially crystallized regions on the ribbon surface. The significant corrosion resistance and the quick degradation of MB in a wide pH range in a recyclable manner by these easily separable and highly efficient catalysts indicate great potential for their practical application.

CO2/CH4 and H2/CH4 Gas Separation Performance of CTA-TNT@CNT Hybrid Mixed Matrix Membranes

This study explored the underlying synergy between titanium dioxide nanotube (TNT) and carbon nanotube (CNT) hybrid fillers in cellulose triacetate (CTA)-based mixed matrix membranes (MMMs) for natural gas purification. The CNT@TNT hybrid nanofillers were blended with CTA polymer and cast as a thin film by a facile casting technique, after which they were used for single gas separation. The hybrid filler-based membrane depicted a higher CO₂ uptake affinity than the single filler (CNT/TNT)-based membrane. The gas separation results indicate that the hybrid fillers (TNT@CNT) are strongly selective for CO₂ over CH₄ and H₂ over CH₄. The increment in the CO₂/CH₄ and H₂/CH₄ selectivities compared to the pristine CTA membrane was 42.98 from 25.08 and 48.43 from 36.58, respectively. Similarly, the CO₂ and H₂ permeability of the CTA-TNT@CNT membrane increased by six- and five-fold, respectively, compared to the pristine CTA membrane. Such significant improvements in CO₂/CH₄ and H₂/CH₄ separation performance and thermal and mechanical properties suggest a feasible and practical approach for potential biogas upgrading and natural gas purification.

Local Structure and Redox Properties of Amorphous CeO2-TiO2 Prepared Using the H2O2-Modified Sol-Gel Method

Amorphous CeO₂-TiO₂ nanoparticles synthesized by the H₂O₂-modified sol-gel method were investigated in terms of the Ce-O-Ce and Ti-O-Ti linkage, local structure, and redox properties. The decrease in the crystallinity of CeO₂-TiO₂ by H₂O₂ addition was confirmed. The metal–oxygen linkage analysis showed the difference in size of the metal–oxygen network between crystalline CeO₂-TiO₂ and amorphous CeO₂-TiO₂ due to the O₂²⁻ formed by H₂O₂. The local structure of CeO₂-TiO₂ was analyzed with an extended X-ray absorption fine structure (EXAFS), and the oscillation changes in the k space revealed the disordering of CeO₂-TiO₂. The decrease in Ce-O bond length and the Ce-O peak broadening was attributed to O₂²⁻ interfering with the formation of the extended metal–oxygen network. The temperature-programmed reduction of the H₂ profile of amorphous CeO₂-TiO₂ exhibited the disappearance of the bulk oxygen reduction peak and a low-temperature shift of the surface oxygen reduction peak. The H₂ consumption increased compared to crystalline CeO₂-TiO₂, which indicated the improvement of redox properties by amorphization.

Synthesis of TiO2/RGO with plasmonic Ag nanoparticles for highly efficient photoelectrocatalytic reduction of CO2 to methanol toward the removal of an organic pollutant from the atmosphere

The synergistic photoelectrochemical (PEC) technology is a robust process for the conversion of CO₂ into fuels. However, designing a highly efficient UV-visible driven photoelectrocatalyst is still challenging. Herein, a plasmonic Ag NPs modified TiO₂/RGO photoelectrocatalyst (Ag-TiO₂/RGO) has been designed for the PEC CO₂ reduction into selective production of CH₃OH. HR-TEM analysis revealed that Ag and TiO₂ NPs with average sizes of 4 and 7 nm, respectively, were densely grown on the few-micron-sized 2D RGO nanosheets. The physicochemical analysis was used to determine the optical and textural properties of the Ag-TiO₂/RGO nanohybrids. Under VU-Vis light illumination, Ag-TiO₂/RGO photocathode possessed a current density of 23.5 mA cm^-2 and a lower electrode resistance value of 125 Ω in CO₂-saturated 1.0 M KOH-aqueous electrolyte solution. Catalytic studies showed that the Ag-TiO₂/RGO photocathode possessed a remarkable PEC CO₂ reduction activity and selective production of CH₃OH with a yield of 85 μmol L^-1 cm^-2, the quantum efficiency of 20% and Faradic efficiency of 60.5% at onset potential of -0.7 V. A plausible PEC CO₂ reduction mechanism over Ag-TiO₂/RGO photocathode is schematically demonstrated. The present work gives a new avenue to develop high-performance and stable photoelectrocatalyst for PEC CO₂ reduction towards sustainable liquid fuels production.

Photocatalytic hydrogen production by ternary heterojunction composites of silver nanoparticles doped FCNT-TiO2

Silver nanoparticles doped with FCNT-TiO₂ heterogeneous catalyst was prepared via one-step chemical reduction process and their efficacy was tested for hydrogen production under solar simulator. Crystallinity, purity, optical properties, and morphologies of the catalysts were examined by X-Ray diffraction, Raman spectroscopy, UV-Visible diffuse reflectance spectra, and Transmission Electron Microscopy. The chemical states and interface interactions were studied by X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. The optimized catalyst showed 19.2 mmol g^-1 h^-1 of hydrogen production, which is 28.5 and 7 times higher than the pristine TiO₂ nanoparticles and FCNT-TiO₂ nanocomposite, respectively. The optimized catalyst showed stability up to 50 h under the solar simulator irradiation. The natural solar light irradiated catalyst showed ~2.2 times higher hydrogen production rate than the solar simulator irradiation. A plausible reaction mechanism of Ag NPs/FCNT-TiO₂ photocatalyst was elucidated by investigating the beneficial co-catalytic role of Ag NPs and FCNTs for enhanced hydrogen production.

Photocatalytic degradation of methylene blue with P25/graphene/polyacrylamide hydrogels: Optimization using response surface methodology

An environment-friendly hydrogel was synthesized by entrapping Degussa P25 on the surface of a reduced graphene oxide (rGO)-polyacrylamide (PAM) matrix.The PAM content of the P25-rGO-PAM (PGP) hydrogel considerably influenced the adsorption and photocatalytic degradation of methylene blue (MB), and the optimal PAM content was 10% (w/v). Furthermore, rGO not only enhanced the adsorption capacity of the hydrogel by increasing the surface area but also increased the photodegradation efficiency synergistically by separating electron-hole pairs. The reaction kinetic constant for MB degradation by the hydrogel was 0.0276 min^-1, which was three and five times the reaction kinetic constants of P25-PAM and rGO-PAM hydrogels, respectively. The synthesized PGP showed high stability and its MB degradation efficiency was considerably high up to five consecutive cycles under UV-irradiation. The eco-friendly nature of the hydrogel was evaluated on the basis of bacterial inactivation, and the treated water was found to be safe for use. Three key operating parameters (initial MB concentration, temperature, and pH) were optimized for maximizing MB removal using a response surface methodology. The complete MB removal efficiency was obtained for the optimal conditions of pH 9.4, a temperature of 31.2 °C, and an initial MB concentration of 5.2 mg/L.

Understanding the Role of Silver Nanostructures and Graphene Oxide Applied as Surface Modification of TiO2 in Photocatalytic Transformations of Rhodamine B under UV and Vis Irradiation

This work is focused on photocatalytic properties of titanium dioxide thin coatings modified with silver nanostructures (AgNSs) and graphene oxide (GO) sheets which were analyzed in processes of chemical transformations of rhodamine B (RhB) under ultraviolet (UV) or visible light (Vis) irradiation, respectively. UV-Vis spectroscopy was applied to analyze the changes in the RhB spectrum during photocatalytic processes, revealing decolorization of RhB solution under UV irradiation while the same process coexisting with the transformation of RhB to rhodamine 110 was observed under Vis irradiation. The novelty of this study is the elaboration of a methodology for determining the parameters characterizing the processes occurring under the Vis irradiation, which enables the comparison of photocatalysts' activity. For the first time, the method for quantification of rhodamine B transformation into rhodamine 110 in the presence of a semiconductor under visible light irradiation was proposed. Photocatalysts with various surface architectures were designed. TiO2 thin coatings were obtained by the sol-gel method. GO sheets were deposited on their surface using the dip-coating method. AgNSs were photogenerated on TiO2 or grown spontaneously on GO flakes. For characterization of obtained photocatalysts, scanning electron microscopy (SEM), X-ray diffraction (XRD) and diffuse-reflectance spectroscopy (DRS) techniques were applied. The results indicate that the surface architecture of prepared coatings does not affect the main reaction path but have an influence on the reaction rates and yields of observed processes.

Heterostructured TiO2/SiO2/γ-Fe2O3/rGO Coating with Highly Efficient Visible-Light-Induced Self-Cleaning Properties for Metallic Artifacts

A novel nanohybrid composite of TiO₂, SiO₂, γ-Fe₂O₃, and reduced graphene oxide (TiO₂@Si:Fe:rGO) is fabricated by the sol-gel method. The properties of the coated film were examined by structural and self-cleaning analyses using simulated discoloration/soiling and roofing tests. The fabricated transparent TiO₂@Si:Fe:rGO composite showed excellent photoactivity and wettability, behaving well in self-cleaning applications. The addition of SiO₂ improved the crystalline structure and surface hydroxylation of TiO₂ nanoparticles. γ-Fe₂O₃ decreased the recombination rate of e^-/h⁺ pairs, and significantly improved photocatalytic activity under visible light. Moreover, rGO sheets as excellent electron acceptors and transporters also reduced recombination, as well as affected wettability, achieving superhydrophilicity under irradiation. The coated substrate showed excellent resistance to simulated acid rain and significantly preserved the substrate from soiling in roofing tests.

Hydrothermal Synthesis of rGO-TiO2 Composites as High-Performance UV Photocatalysts for Ethylparaben Degradation

A series of reduced graphene oxide-TiO2 composites (rGO-TiO2) were prepared by hydrothermal treatment using graphite and titanium isopropoxide as raw materials. The structural, surface, electronic, and optical properties of the prepared composites were extensively characterized by N2 adsorption, FTIR, XRD, XPS, Raman spectroscopy, and DRS. GO was found to be effectively reduced and TiO2 to be in pure anatase phase in all composites obtained. Finally, experiments were performed to evaluate the effectiveness of these new materials as photocatalysts in the degradation of ethylparaben (EtP) by UV radiation. According to the band-gap energies obtained (ranging between 3.09 eV for 4% rGO-TiO2 to 2.55 eV for 30% rGO-TiO2), the rGO-TiO2 composites behave as semiconductor materials. The photocatalytic activity is highest with a rGO content of 7 wt% (7% rGO-TiO2), being higher than observed for pure TiO2 (Eg = 3.20 eV) and achieving 98.6% EtP degradation after only 40 min of treatment. However, the degradation yield decreases with higher percentages of rGO. Comparison with rGO-P25 composites showed that a better photocatalytic performance in EtP degradation is obtained with synthesized TiO2 (rGO-TiO2), probably due to the presence of the rutile phase (14.1 wt %) in commercial P25.

Preparation and characterization of TiO2-Ag loaded fish gelatin-chitosan antibacterial composite film for food packaging

In this study, fish gelatin and chitosan were used as the film-forming substrate, and different concentrations of TiO₂-Ag were added to prepare composite films. The physicochemical characteristics and microstructure of the films were studied. The results showed that the addition of TiO₂-Ag significantly increased the water solubility of the film. When the TiO₂-Ag concentration was increased to 0.5%, the film had the best antibacterial ability and the lowest light transmittance (54.6%), but the tensile strength of the film was the lowest, decreased from 17.39 MPa to 9.014 MPa. The water vapor permeability of film first decreased and then increased, and the minimum value was 2.63 × 10^-12 g·cm/cm²·s·Pa when the concentration of TiO₂-Ag was 0.4%. XRD, XPS, and ATR-FTIR results showed that the presence of TiO₂-Ag crystals in the film could enhance the interaction between the components, and FE-SEM results showed that the film had a very smooth and uniform surface. In general, FG/Ch/TiO₂-Ag composite film is expected to be used in the food packaging industry.

Enhanced detoxification of p-bromophenol by novel Zr/Ag-TiO2@rGO ternary composite: Degradation kinetics and phytotoxicity evolution studies

The toxicity and persistence of the halogenated aromatics, particularly brominated phenolic compounds have drawn serious concerns to the environment, emphasizing the potential effects on human health and ecosystems balance. Advanced oxidation process (AOP) has received much attention as an alternative for the conventional wastewater treatment methods to treat water contaminated with toxic pollutants. This study investigated the degradation and detoxification of p-bromophenol (p-BP) by a novel Zr/Ag-TiO₂@rGO photocatalyst under visible light. Upon 3 h of visible light irradiation over Zr/Ag-TiO₂@rGO, more than 95% of p-BP (15 mg/L) degradation was achieved at a rate of 0.23 min^-1. The degradation products were identified by GC-MS and possible degradation pathway was proposed. The phytotoxicity evolution of the degraded products was assessed on Vigna radiata (V. radiata), in which seeds treated with pure p-BP showed less germination (40%) compared to degradation products (100%). Furthermore, the germination index (GI) of p-BP was found to be 11.1% before degradation while it increased to 80.5% after 3 h of degradation indicated that this photodegradation process achieved detoxification of p-BP. Thus, this study demonstrated that p-BP elimination and detoxification could be simply achieved with Zr/Ag-TiO₂@rGO nanocomposite under visible light irradiation, which provides new solution for wastewater treatment and water reuse in crop irrigation.

A facile synthesis of Cs loaded TiO2 nanotube photoelectrode for the removal of 4-chloroguaiacol

In this study, novel Cesium (Cs) doped TiO₂ nanotubes photoelectrode (Cs/TiO₂NTs) were synthesized by simple electrochemical anodization method and characterized by several physicochemical techniques. In particular, the photocatalytic (PC), electrocatalytic (EC) and photoelectrocatalytic (PEC) activity of newly synthesized Cs/TiO₂NTs electrodes was investigated using 4-Chloroguaiacol (4-CG). The effect of operating parameters like Cs concentration, electrolyte concentration, external current and pH on degradation efficacy was examined. PEC oxidation using Cs/TiO₂NTs lead to 92% degradation of 4-CG in 6 h of solar light irradiation under optimized conditions (2.5 mM Cs, 160 mg L^-1 Na₂SO₄, 0.03 A current and pH 3). A comparative assessment between PEC, PC and EC process manifested that PEC process was most efficient than the other two processes and Cs/TiO₂NTs exhibited higher PEC activity than bare-TiO₂ electrodes in terms of degradation and mineralization of organic pollutant. The generation of OH radicals was found to be highest in PEC when compared to EC and PC process. Possible intermediates/byproducts were identified by GC-MS technique and a corresponding tentative degradation pathway has been proposed. Cytotoxicity study showed that PEC has potential to detoxify 4-CG. Hence, combination of TiO₂ electrodes decorated with Cs metal can act as a highly efficient photoelectrode for the degradation of hazardous pollutants.

Photocatalytic Treatment of An Actual Confectionery Wastewater Using Ag/TiO2/Fe2O3: Optimization of Photocatalytic Reactions Using Surface Response Methodology

Titanium dioxide (TiO2) photocatalysis is one of the most commonly studied advanced oxidation processes (AOPs) for the mineralization of deleterious and recalcitrant compounds present in wastewater as it is stable, inexpensive, and effective. Out of all, doping with metal and non-metals, and the heterojunction with another semiconductor were proven to be efficient methods in enhancing the degradation of organic pollutants under ultraviolet (UV) and visible light. However, complex degradation processes in the treatment of an actual wastewater are difficult to model and optimize. In the present study, the application of a modified photocatalyst, Ag/TiO2/Fe2O3, for the degradation of an actual confectionery wastewater was investigated. Factorial studies and statistical design of experiments using the Box-Behnken method along with response surface methodology (RSM) were employed to identify the individual and cross-factor effects of independent parameters, including light wavelength (nm), photocatalyst concentration (g/L), initial pH, and initial total organic carbon (TOC) concentration (g/L). The maximum TOC removal at optimum conditions of light wavelength (254 nm), pH (4.68), photocatalyst dosage (480 mg/L), and initial TOC concentration (11,126.5 mg/L) was determined through the numerical optimization method (9.78%) and validated with experimental data (9.42%). Finally, the first-order rate constant with respect to TOC was found to be 0.0005 min−1 with a residual value of 0.998.

Self-Assembled AgNP-Containing Nanocomposites Constructed by Electrospinning as Efficient Dye Photocatalyst Materials for Wastewater Treatment

The design and self-assembly of graphene oxide (GO)-based composite membranes have attracted enormous attention due to their wide application in nanomaterial and environmental fields. In this work, we have successfully developed a strategy to fabricate new composite membranes based on poly(vinyl alcohol)/poly(acrylic acid)/carboxyl-functionalized graphene oxide modified with silver nanoparticles (PVA/PAA/GO-COOH@AgNPs), which were prepared via thermal treatment and the electrospinning technique. Due to the strong π-π forces and strong electrostatic interactions of GO-COOH sheets, the prepared composite membranes and their lager surface areas were modified by scores of AgNPs, which demonstrated that a high-efficiency photocatalyst removed the organic dyes from the aqueous solutions. The prepared PVA/PAA/GO-COOH@AgNPs nanocomposite membranes showed a remarkable photocatalytic capacity in the catalytic degradation of the methylene blue dye solutions. Most importantly, the whole process was easy, mild, and eco-friendly. Additionally, the as-prepared membranes could be repeatedly used after the catalytic reaction.