In-situ Hf/Zr co-doped Fe2O3 nanorod decorated with CuOx/CoOx: Enhanced photocatalytic performance for antibacterial and organic pollutants

Herein, we successfully synthesized Hf/Zr co-doping on Fe2O3 nanorod photocatalyst by a hydrothermal process and quenching methods. The synergistic roles of Hf and Zr double-doping on the bacteria inactivation test and decomposition of organic pollutants were investigated in detail for the 1 wt% CoOx loaded Hf/Zr-Fe2O3 NRs and CuOx/CoOx loaded Hf/Zr-Fe2O3 NRs photocatalyst. Initially, the rod-like porous morphology of the Hf/Zr-doped Fe2O3 NRs was produced via a hydrothermal method at various Hf co-doping (0, 2, 4, 7 and 10)%. Further, CoOx and CuOx loaded by a wet impregnation approach on the Hf/Zr-Fe2O3 NRs and a highly photoactive Hf(4)/Zr-Fe2O3 [CoOx/CuOx] NRs photocatalyst were developed. After the Hf(4)/Zr-Fe2O3 [CoOx/CuOx] NRs photocatalyst treatment, the Bio-TEM imagery of bacterial cells showed extensive morphological deviations in cell membranes. Hf(4)/Zr-Fe2O3 NR achieved 84.1% orange II degradation upon 3 h illumination, which is higher than that of Hf-Fe2O3 and Zr-Fe2O3 (68.7 and 73.5%, respectively). Additionally, the optimum sample, Hf(4)/Zr-Fe2O3 [CoOx/CuOx] photocatalyst, exhibited 95.5% orange II dye degradation after light radiation for 3 h. Optimized Hf(4)/Zr-Fe2O3 [CoOx/CuOx] catalysts exhibited 99.9% and 99.7% inactivation of E. coli and S. aureus with 120 min, respectively. Further, scavenger experiments revealed that the electrons are the primary responsible species for photocatalytic kinetics. This work will provide a rapid method for the development of high photocatalytic performance materials for bacterial disinfection and organic degradation.

A review of tungsten trioxide (WO3)-based materials for antibiotics removal via photocatalysis

Antibiotics are extensively used in human medicine and animal breeding. The use of antibiotics has posed significant risks and challenges to the natural water environment. On a global scale, antibiotics have been frequently detected in the environment, azithromycin (254-529 ng·L^-1), ciprofloxacin (245-1149 ng·L^-1), ofloxacin (518-1998 ng·L^-1), sulfamethoxazole (1325-5053 ng·L^-1), and tetracycline (31.4-561 ng·L^-1) are the most detected antibiotics in wastewater and surface water. Abuses of antibiotics has caused a significant threat to water resources and has seriously threatened the survival of human beings. Therefore, there is an urgent need to reduce antibiotic pollution and improve the environment. Researchers have been trying to develop effective methods and technologies for antibiotic degradation in water. Finding efficient and energy-saving methods for treating water pollutants has become an important global topic. Photocatalytic technology can effectively remove highly toxic, low-concentration, and difficult-to-treat pollutants, and tungsten trioxide (WO₃) is an extremely potential alternative catalyst. Pt/WO₃ photocatalytic degradation efficiency of tetracycline was 72.82%, While Cu-WO₃ photocatalytic degradation efficiency of tetracycline was 96.8%; WO₃/g-C₃N₄ photocatalytic degradation efficiency of ceftiofur was 70%, WO_3/W photocatalytic degradation efficiency of florfenicol was 99.7%; WO₃/CdWO₄ photocatalytic degradation efficiency of ciprofloxacin was 93.4%; WO₃/Ag photocatalytic degradation efficiency of sulfanilamide was 96.2%. Compared to other water purification methods, photocatalytic technology is non-toxic and ensures complete degradation through a stable reaction process, making it an ideal water treatment method. Here, we summarize the performance and corresponding principles of tungsten trioxide-based materials as a photocatalytic catalyst and provide substantial insight for further improving the photocatalytic potential of WO₃-based materials.

Domestic microwave assisted one-step co-precipitation of Ag–CuO nanocomposite of Cu/Ag ratio optimized for photocatalysis and comparison with blending CuO with Ag nanoparticles

The Ag–CuO metal–semiconductor nanocomposite (NC) is an important component in various nanomaterial-based applications. Several approaches have been studied to facilitate its synthesis. However, most of them encounter some drawbacks. In the present work, we show the synthesis of Ag–CuO NCs through one-pot co-precipitation with the aid of simple starting chemicals and measures including metal nitrates, hexamine, agar, and domestic microwave heating. Photocatalyzed degradation of Congo Red in addition to the structural and optical characteristics show that this method is successful in production of the Schottky barrier in Ag–CuO NCs with improved photocatalytic activity (PCA). Changing the Cu content shows that the NC is not successfully formed at low Cu mol%. Consequently, the PCA of Ag–CuO of low Cu (2%–6%) lies within 4.5 × 10−4 – 5.1 × 10−4 min−1, which is even lower than those of plain Ag and CuO nanoparticles (6.0 × 10−4 – 8.1 × 10−4 min−1, respectively). 60 mol% was the optimum Cu content with the highest PCA (18.8 × 10−4 min−1). Blending plain Ag and CuO nanoparticles to mimic the co-precipitated 60 mol% Ag–CuO showed very low PCA, even lower than the plain Ag and CuO, which once again confirms the efficiency of the simple one-pot co-precipitation approach in producing Ag–CuO with the Schottky barrier and promoted PCA.

RGO/WO3 hierarchical architectures for improved H2S sensing and highly efficient solar-driving photo-degradation of RhB dye

Surface area and surface active sites are two important key parameters in enhancing the gas sensing as well as photocatalytic properties of the parent material. With this motivation, herein, we report a facile synthesis of Reduced Graphene Oxide/Tungsten Oxide RGO/WO3 hierarchical nanostructures via simple hydrothermal route, and their validation in accomplishment of improved H2S sensing and highly efficient solar driven photo-degradation of RhB Dye. The self-made RGO using modified Hummer's method, is utilized to develop the RGO/WO3 nanocomposites with 0.15, 0.3 and 0.5 wt% of RGO in WO3 matrix. As-developed nanocomposites were analyzed using various physicochemical techniques such as XRD, FE-SEM, TEM/HRTEM, and EDAX. The creation of hierarchic marigold frameworks culminated in a well affiliated mesoporous system, offering efficient gas delivery networks, leading to a significant increase in sensing response to H2S. The optimized sensor (RGO/WO3 with 0.3 wt% loading) exhibited selective response towards H2S, which is ~ 13 times higher (Ra/Rg = 22.9) than pristine WO3 (Ra/Rg = 1.78) sensor. Looking at bi-directional application, graphene platform boosted the photocatalytic activity (94% degradation of Rhodamine B dye in 210 min) under natural sunlight. The RGO's role in increasing the active surface and surface area is clarified by the H2S gas response analysis and solar-driven photo-degradation of RhB dye solution. The outcome of this study provides the new insights to RGO/WO3 based nanocomposites' research spreadsheet, in view of multidisciplinary applications.

Fabrication of Ag2O/WO3 p-n heterojunction composite thin films by magnetron sputtering for visible light photocatalysis

Semiconductor-based nanostructures which are photo-catalytically active upon solar light irradiation were extensively used for environmental remediation due to the potential decomposition of various kinds of pollutants. In this work, we report the preparation of a sustainable thin film composite, i.e. Ag2O/WO3 p-n heterojunction, and investigation of its photocatalytic activity. To achieve the composite structure, WO3/Ag-WO3 layers were deposited over a quartz substrate by magnetron sputtering at room temperature and subsequently annealed at 823 to 923 K. The thin film structure, morphology, and chemical states were thoroughly characterized by X-ray diffraction, field-emission scanning electron microscopy, transmission electron spectroscopy, and X-ray photoelectron spectroscopy. The obtained results revealed that the amorphous Ag-doped WO3 was crystallized into monoclinic WO3 and Ag2O, in which nanocrystalline Ag2O was diffused towards the surface of WO3. Optical transmittance spectra recorded by UV-vis-NIR spectroscopy revealed that the WO3/Ag-WO3 films became transparant in the visible region after annealing at high temperature (873 K and 923 K). The Ag2O/WO3 p-n heterojunction composite thin films showed high photocatalytic activity (0.915 × 10-3 min-1) under visible light irradiation, which is attributed to the efficiency of effective photogenerated charge-carrier formation and the reduced recombination rate of photogenerated electron-hole pairs. Unlike the powder-based photocatalysts, the reported thin film-based heterojunction photocatalyst could be very sustainable, and cost-effective.

Removal of acetylsalicylate and methyl-theobromine from aqueous environment using nano-photocatalyst WO3-TiO2 @g-C3N4 composite

Highly efficient, visible light-driven and a novel ternary hybrid photocatalyst WO₃-TiO₂-g-C₃N₄ with robust stabilities and versatile properties has been synthesized through facile hydrothermal method. This study considers the photo-degradation of aspirin (acetylsalicylate) and caffeine (methyl-theobromine) via photocatalysts (WO₃, WO₃/TiO_2, and WO₃/TiO₂/g-C₃N₄ (WTCN) composite) under visible-light irradiation. The SEM and TEM images show the formation of WO₃ nanoparticles with orthorhombic structure and average particle size of 65 nm. The photocatalyst WTCN composite possesses higher-catalytic activity when compared to that of WO₃ and WO₃/TiO₂ for degradation of aspirin and caffeine. The incorporation of g-C₃N₄ in WO₃/TiO₂ composite exhibited significant influence on the photocatalytic performance for both pollutants. Excellent photocatalytic performance of WTCN composite was observed owing to hydroxyl radical (OH) and superoxide radical (O₂^-) as main active species. The enhanced photocatalytic activity of WTCN composite can be attributed to following three reasons: (1) extended visible-light absorption; (2) extended surface area; (3) efficient charge-separation due to synergistic effects between g- and WO₃/TiO₂ composite. The removal efficiency of aspirin and caffeine (Methyl theobromine) could be achieved as much as 98% and 97% for acetylsalicylate and methyl-theobromine using WTCN composite material, respectively. This study could provide new insights into the synthesis of novel WO₃-based materials for environmental and energy applications.

Ultrasonic assisted synthesis with enhanced visible-light photocatalytic activity of NiO/Ag3VO4 nanocomposite and its antibacterial activity

The NiO/Ag₃VO₄ nanocomposite photocatalysts were developed by ultrasonic assisted preparation method to study the photocatalytic activity under visible light irradiation. The samples were characterized by UV-DRS, XRD, FT-IR, XPS, SEM, EDX, TEM, EIS and BET analysis. The photocatalytic activity of NiO/Ag₃VO₄ nanocomposite for the photodegradation of 4-Nitro Phenol (4-NP) and Rose Bengal (RB) under visible light irradiation was studied and it is observed that the activity has been much higher than that of the pure Ag₃VO₄. DRS spectrum shows the absorption edge of NiO-Ag₃VO₄ in visible region of spectrum. The formation of cubic structured NiO and orthorhombic structured Ag₃VO₄ was confirmed by powder X-ray diffraction analysis. The results of XPS analysis confirmed the coexistence of NiO and Ag₃VO₄ in the NiO/Ag₃VO₄ composite. The specific surface area and pore structure of the prepared samples were measured by BET. Enhanced charge separation efficiency was confirmed by electrochemical impedance spectroscopy (EIS) measurements. The kinetics of the NiO/Ag₃VO₄ nanocomposite was proposed to investigate the intervened effects of NiO to Ag₃VO₄ on the promotion of photocatalytic property. NiO/Ag₃VO₄ was found to be stable and reusable without appreciable loss of catalytic activity up to four consecutive cycles. A possible electron-hole transfer mechanism at the NiO/Ag₃VO₄ interface is proposed. It also showed effective and efficient bactericidal activities against Staphylococcus aureus, Streptococcus, Proteus and Escherichia coli bacteria. Our results provide some new insights on the performance of visible light photocatalysts on environmental remediation.

Efficient difunctional photocatalyst prepared in situ from Prussian blue analogues for catalytic water oxidation and visible-light absorption

Co(OH)₂-modified CuO (Co(OH)₂/CuO) nanoparticles serve as both visible-light-driven water oxidation catalysts and visible-light-absorption centers.

Morphological Control of Mesoporosity and Nanoparticles within Co3O4-CuO Electrospun Nanofibers: Quantum Confinement and Visible Light Photocatalysis Performance

The one-dimensional (1D) mesoporous and interconnected nanoparticles (NPs) enriched composite Co₃O₄-CuO nanofibers (NFs) in the ratio Co:Cu = 1/4 (Co₃O₄-CuO NFs) composite have been synthesized by electrospinning and calcination of mixed polymeric template. Not merely the mesoporous composite Co₃O₄-CuO NFs but also single mesoporous Co₃O₄ NFs and CuO NFs have been produced for comparison. The choice of mixed polymer templates such as polyvinylpyrrolidone (PVP) and polyethylene glycol (PEG) for electrospinning is responsible for the formation of 1D mesoporous NFs. The HR-TEM result showed evolution of interconnected nanoparticles (NPs) and creation of mesoporosity in all electrospun NFs. The quantum confinement is due to NPs within NFs and has been proved by the surface-enhanced Raman scattering (SERS) study and the UV-vis-NRI diffuse reflectance spectra (DRS). The high intense photoluminescence (PL) spectra showing blue shift of all NFs also confirmed the quantum confinement phenomena. The lowering of PL spectrum after mixing of CuO in Co₃O₄ nanofibers framework (Co₃O₄-CuO NFs) proved CuO as an efficient visible light response low cost cocatalyst/charge separator. The red shifting of the band gap in composite Co₃O₄-CuO NFs is due to the internal charge transfer between Co²⁺ to Co³⁺ and Cu²⁺, proved by UV-vis absorption spectroscopy. Creation of oxygen vacancies by mixing of CuO and Co₃O₄ also prevents the electron-hole recombination and enhances the photocatalytic activity in composite Co₃O₄-CuO NFs. The photocurrent density, Mott-Schottky (MS), and electrochemical impedance spectroscopy (EIS) studies of all NFs favor the high photocatalytic performance. The mesoporous composite Co₃O₄-CuO NFs exhibits high photocatalytic activity toward phenolic compounds degradation as compared to the other two NFs (Co₃O₄ NFs and CuO NFs). The kinetic study of phenolic compounds followed first order rate equation. The high photocatalytic activity of composite Co₃O₄-CuO NFs is attributed to the formation of mesoporosity and interconnected NPs within NFs framework, quantum confinement, extended light absorption property, internal charge transfer, and effective photogenerated charge separations.

Construction of WO3–g-C3N4 composites as efficient photocatalysts for pharmaceutical degradation under visible light

Simple construction of WO₃–g-C₃N₄ Z-scheme heterojunctions as efficient photocatalysts to degrade sulfamethoxazole, which is one of the most commonly used pharmaceuticals.

A novel ternary CuO decorated Ag3AsO4/GO hybrid as a Z-scheme photocatalyst for enhanced degradation of phenol under visible light

A novel Z-scheme ternary CuO/Ag₃AsO₄/GO hybrid having significant visible light catalytic activity and stability is successfully synthesized via a self-assembly method.

Ag loaded WO3 nanoplates for efficient photocatalytic degradation of sulfanilamide and their bactericidal effect under visible light irradiation

Sulfonamides (SAs) are extensively used antibiotics and their residues in the water bodies propose potential threat to the public. In this study, degradation efficiency of sulfanilamide (SAM), which is the precursor of SAs, using WO3 nanoplates and their Ag heterogeneous as photocatalysts was investigated. WO3 nanoplates with uniform size were synthesized by a facile one step hydrothermal method. Different amount of Ag nanoparticles (Ag NPs) were loaded onto WO3 nanoplates using a photo-reduction method to generate WO3/Ag composites. The physio-chemical properties of synthesized nanomaterials were systematically characterized. Photodegradation of SAM by WO3 and WO3/Ag composites was conducted under visible light irradiation. The results show that WO3/Ag composites performed much better than pure WO3 where the highest removal rate was 96.2% in 5h. Ag as excellent antibacterial agent also endows certain antibacterial efficiency to WO3, and 100% removal efficiency against Escherichia Coli and Bacillus subtilis could be achieved in 2h under visible light irradiation for all three WO3/Ag composites synthesized. The improved performance in terms of SAM degradation and antibacterial activity of WO3/Ag can be attributed to the improved electron-hole pair separation rate where Ag NPs act as effective electron trapper during the photocatalytic process.

The fabrication of a novel Ag3VO4/WO3 heterojunction with enhanced visible light efficiency in the photocatalytic degradation of TC

The construction of efficient photocatalysts for environmental remediation has attracted a great deal of attention in recent years.

Construction of nitrogen-doped graphene quantum dots-BiVO4/g-C3N4Z-scheme photocatalyst and enhanced photocatalytic degradation of antibiotics under visible light

In this study, an effective nitrogen-doped graphene quantum dots (NGQDs)-BiVO₄/g-C₃N₄Z-scheme heterojunction has been successfully prepared for environmental remediation.

Tuning of the crystal engineering and photoelectrochemical properties of crystalline tungsten oxide for optoelectronic device applications

WO₃crystals with {002} or {111} facets primarily exposed, WO₃films with dominant orientations, doping and heterostructuring are highlighted.

Novel synthesis of C, N doped rice grain shaped ZnS nanomaterials – towards enhanced visible light photocatalytic activity for aqueous pollutant removal and H2 production

Novel synthesis of C, N doped rice grain shaped visible active ZnS nano photocatalysts. Enhanced activity for the pollutant removal and H₂ production from water.

Z-scheme photocatalytic hydrogen production over WO3/g-C3N4 composite photocatalysts

WO₃/g-C₃N₄ catalysts exhibit excellent photocatalytic performance for H₂ production from aqueous solution through the Z-scheme mechanism, which results in the efficient charge separation.