Fabrication of Ag<Subscript>3</Subscript>PO<Subscript>4</Subscript>-AgBr-PTh composite loaded on Na<Subscript>2</Subscript>SiO<Subscript>3</Subscript> with enhanced visible-light photocatalytic activity

A novel Ag₃PO₄-AgBr-PTh composite loaded on Na₂SiO₃ was synthesized for enhanced visible-light photocatalytic activity. The photocatalytic activity of the samples was evaluated by photodegrading rhodamine B (RhB) under visible light irradiation. The main reactive species and possible photocatalytic mechanism were also discussed. As a result, the Ag₃PO₄-AgBr-PTh composite loaded on Na₂SiO₃ exhibited enhanced photocatalytic activity for RhB compared with Ag₃PO₄ under visible-light irradiation. Additionally, it was demonstrated that the hole (h⁺) and superoxide radical (?O ₂ ^? ) were the major reactive species involving in the RhB degradation. PTh played vital role for the enhanced photocatalytic activity of Ag₃PO₄-AgBr-PTh-Na₂SiO₃ composite, which offered an electron transfer expressway and accelerated the transfer of the electrons from the CB of AgBr into Ag₃PO₄. This work could provide a new perspective for the synthesis of Ag₃PO₄-based composites and the improvement of photocatalytic activity of Ag₃PO₄.     

A facile one step synthesis of SnO<Subscript>2</Subscript>/CuO and CuO/SnO<Subscript>2</Subscript> nanocomposites: photocatalytic application

Here novel photocatalysts, SnO₂/CuO and CuO/SnO₂ nanocomposites were successfully synthesized by chemical method at room temperature. X-ray Diffraction (XRD), transmission electron microscopy (TEM), Fourier transform Infrared (FT-IR), UV–Visible (UV–Vis) and photoluminescence (PL) spectroscopy were utilized for characterization of the nanocomposites. The photocatalytic activity of the nanocomposites was investigated. The hybrid nanocomposites exhibited high photocatalytic activity as evident from the degradation of methylene blue (MB) dye. The result revealed substantial degradation of the MB dye (92 and 69.5% degradation of SnO₂/CuO and CuO/SnO₂, respectively) under visible light illumination with short period of 30 min. Their large conduction band potential difference and the inner electrostatic field formed in the p–n heterojunction provide a strong driving force for the photogenerated electrons to move from Cu₂O to SnO₂ under visible light illumination. The excellent photodegradation of methylene blue suggested that the heterostructured SnO₂/CuO nanocomposite possessed higher charge separation and photodegradation abilities than CuO/SnO₂ nanocomposite under visible light irradiation.     

Sn<Superscript>4+</Superscript> and La<Superscript>3+</Superscript> co doped TiO<Subscript>2</Subscript> nanoparticles and their optical,photocatalytic and antibacterial properties under visible light

Sn⁴⁺ and La³⁺ co-doped TiO₂ photocatalytic material with nanoparticle structure have been successfully prepared using SnCl₂·2H₂O and La(NO₃)₃·6H₂O as precursors. Scanning electron microscopy, X-ray diffraction, transmission electron microscopy and UV–visible spectroscopy have been used to for the characterization of the morphology, crystal structure, particle size and optical properties of the samples. The photocatalytic properties of sample with various amount of La doped TiO₂ have been studied by photo degradation of methyl orange (MO) in water under visible light. XRD patterns showed both rutile and anatase phases for 5 mol% of Sn and 5–10 mol% of La. But anatase phase with a little rutile phase was formed for 5 mol%Sn and 10 mol%La. The prepared Sn and La co doped TiO₂ photo-catalyst showed optical absorption edge in the visible light area and exhibited excellent photo-catalytic ability for degradation of MO solution under visible irradiation. Antibacterial behavior towards E. coli was then studied under visible irradiation. The synthesized T-5%Sn-10%La powder exhibited superior antibacterial activity under visible irradiation compared to the pure TiO₂.     

Photocatalytic activity of polypyrrole/TiO<Subscript>2</Subscript> nanocomposites under visible and UV light

A series of polypyrrole (PPy)/titanium dioxide (TiO₂) nanocomposites were prepared in different polymerization conditions by ‘in situ’ chemical oxidative polymerization. The nanocomposites were characterized by transmission electron microscopy (TEM), Fourier transform infrared spectra (FT-IR), X-ray photoelectron spectroscopy spectra (XPS), and UV–Vis diffuse reflectance spectra. The photocatalytic degradation of methyl orange (MO) was chosen as a model reaction to evaluate the photocatalytic activities of TiO₂/PPy catalysts. The results show that a strong interaction exists at the interface between TiO₂ and PPy, the deposition of PPy on TiO₂ nanoparticles can alleviate their agglomeration, PPy/TiO₂ nanocomposites show stronger absorbance than neat TiO₂ under the whole range of visible light. The obtained PPy/TiO₂ nanocomposites exhibit significantly higher photocatalytic activity than the neat TiO₂ on the degradation of MO aqueous solution under visible and UV light illumination. The reasons for improving the photocatalytic activity were also discussed.     

Flexible electrospun MWCNTs/Ag<Subscript>3</Subscript>PO<Subscript>4</Subscript>/PAN ternary composite fiber membranes with enhanced photocatalytic activity and stability under visible-light irradiation

Semiconductor photocatalysis is a promising technology for removing contaminants from water. Particularly, visible-light photocatalysis has attracted much attention because of its potential to utilize solar energy. However, nano-sized visible-light-driven photocatalysts easily aggregate during water treatment. Besides, it is difficult to recycle them from treated systems. Therefore, it is of great importance to develop visible-light-responsive immobilized photocatalysts with high activity. In this work, MWCNTs/Ag₃PO₄/polyacrylonitrile (PAN) ternary composite fiber membranes (TCFMs) with good photocatalytic performance were fabricated by electrospinning technique combined with in situ Ag₃PO₄ forming reaction. Due to the addition of MWCNTs, the band gap of MWCNTs/Ag₃PO₄/PAN TCFMs became narrower than that of Ag₃PO₄/PAN binary composite fiber membranes (BCFMs), which made MWCNTs/Ag₃PO₄/PAN TCFMs be able to use light at longer wavelengths. Compared with Ag₃PO₄/PAN BCFMs, the as-prepared MWCNTs/Ag₃PO₄/PAN TCFMs showed enhanced photocatalytic activity and stability for degrading rhodamine B (RhB) in batch processing systems, which mainly ascribed to fast electron transfer from Ag₃PO₄ to MWCNTs and the resulting high electron–hole (e^?–h⁺) separation efficiency. Radical trapping experiments revealed that holes (h⁺) and superoxide radicals (^·O₂^?) played primary roles in RhB degradation. In addition, the flexible MWCNTs/Ag₃PO₄/PAN TCFMs also showed potential practical application in the continuous wastewater treatment by a suitable photocatalytic membrane reactor. This work provides a facile approach to prepare flexible supported photocatalytic membrane with visible-light response, high activity and good stability.     

Improved photocatalytic degradation of organic dye using Ag<Subscript>3</Subscript>PO<Subscript>4</Subscript>/MoS<Subscript>2</Subscript> nanocomposite

Highly efficient Ag₃PO₄/MoS₂ nanocomposite photocatalyst was synthesized using a wet chemical route with a low weight percentage of highly exfoliated MoS₂ (0.1 wt.%) and monodispersed Ag₃PO₄ nanoparticles (~5.4 nm). The structural and optical properties of the nanocomposite were studied using various characterization techniques, such as XRD, TEM, Raman and absorption spectroscopy. The composite exhibits markedly enhanced photocatalytic activity with a low lamp power (60 W). Using this composite, a high kinetic rate constant (k) value of 0.244 min^-1 was found. It was observed that ~97.6% of dye degrade over the surface of nanocomposite catalyst within 15 min of illumination. The improved photocatalytic activity of Ag₃PO₄/MoS₂ nanocomposite is attributed to the efficient interfacial charge separation, which was supported by the PL results. Large surface area of MoS₂ nanosheets incorporated with well dispersed Ag₃PO₄ nanoparticles further increases charge separation, contributing to enhanced degradation efficiency. A possible mechanism for charge separation is also discussed.     

Facile fabrication of hierarchical BiVO<Subscript>4</Subscript>/TiO<Subscript>2</Subscript> heterostructures for enhanced photocatalytic activities under visible-light irradiation

BiVO₄/TiO₂ nanocomposites were fabricated by a facile wet-chemical process, followed by the synthesis of TiO₂ hierarchical spheres via hydrothermal method. The BiVO₄/TiO₂ nanocomposites were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, UV–Vis diffuse reflectance spectroscopy and X-ray photoelectron spectroscopy. The results showed that prepared TiO₂ presented hierarchical spherical morphology self-assembled by nanoparticles and an anatase–brookite mixed crystal phase. The introduction of monoclinic BiVO₄ components retained the hierarchical structures and expanded the light response to around 510 nm. Type II BiVO₄/TiO₂ heterostructured nanocomposites exhibited improved photocatalytic degradation towards methylene blue under visible-light irradiation, especially for the composite photocatalysts with atomic Ti/Bi?=?10, which showed double degradation rate than that of pure BiVO₄. The enhanced photocatalytic mechanism of the heterostructured BiVO₄/TiO₂ nanocomposites was discussed as well.     

Self-assembly of nanoparticles to prepare of dendritic AgCl–Ag<Subscript>2</Subscript>S nanocomposites through a simple one-pot hydrothermal approach and its photocatalytic activity

Herein, AgCl–Ag₂S nanocomposites with dendritic morphology were synthesized via a simple one-pot hydrothermal route for the first time. AgNO₃, HCl, and thioacetamide were utilized as starting reagents. The as-prepared AgCl–Ag₂S nanocomposites were extensively characterized by techniques such as X-ray diffraction patterns, scanning electron microscopy, energy dispersive X-ray spectroscopy and diffused reflectance UV–visible spectrum. The results showed that the nanoparticles were self-assembled to prepare AgCl–Ag₂S nanocomposites with dendritic morphology. The efficiency of AgCl–Ag₂S nanocomposites as a photocatalyst for the decolorization of methyl orange (MO) using visible light irradiation has been evaluated. As a result, an enhanced photocatalytic efficiency of AgCl–Ag₂S nanocomposites compared to AgCl nanostructures was obtained due to absorption of wider range of light wavelength by AgCl–Ag₂S nanocomposites.     

Synthesis and investigation of SnS<Subscript>2</Subscript>/RGO nanocomposites with different GO concentrations: structure and optical properties,photocatalytic performance

In this study, we report the synthesis of tin disulfide/reduced graphrene oxide (SnS₂/RGO) nanocomposites by a simple one-step hydrothermal method. In order to investigate the effect of RGO on the structure and optical properties and photocatalytic activity of the products a series of nanocomposites was prepared with different concentrations of GO. The samples were examined using X-ray diffraction, field emission scanning electron microscopy (FESEM), Raman spectroscopy, UV–Vis spectroscopy and photoluminescence techniques. The results confirmed the growth of SnS₂ with the hexagonal phase. FESEM analysis showed that the hexagonal tin disulfide nanoplates are uniformly dispersed on the surface of the graphene oxide sheets. The optical examination of SnS₂ and SnS₂/RGO nanocomposites indicated that the band gaps of all nanocomposites are greater than that of SnS₂ due to the quantum confinement effect. The photocatalytic activity of the SnS₂/RGO nanocomposites was investigated for degradation of the acid orange 7 dye under visible light. It was observed that all nanocomposites have a higher photocatalytic activity for the degradation in comparison with pure SnS₂. The optimum concentration of GO in SnS₂/RGO nanocomposite for achieving the highest photocatalytic efficiency (81%) was determined as 2 mg ml^?1 during 180 min.     

Synthesis and characterization of Ag3PO4/multiwalled carbon nanotube composite photocatalyst with enhanced photocatalytic activity and stability under visible light

A novel Ag₃PO₄/multiwalled carbon nanotube (Ag₃PO₄/MWCNT) composite has been prepared by a simple precipitant approach. The obtained samples were characterized by X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray, UV–Vis diffuse reflectance, and Raman spectroscopy. It is found that the MWCNTs are well deposited on Ag₃PO₄ nanoparticles. The Ag₃PO₄/MWCNT composite with MWCNT content of 1.4 wt% exhibits optimal photocatalytic activity under visible light. The rate constant of MO degradation over Ag₃PO₄/1.4 wt% MWCNT is 5.84 times that of pure Ag₃PO₄. Compared with pure Ag₃PO₄, the incorporation of MWCNTs not only significantly enhances the photocatalytic activity but also improves the structural stability of Ag₃PO₄, suggesting that the synergistic effects take place in the composite. The improvement is attributed to the conductive structure supported by MWCNTs, which favors electron–hole separation and the removal of photogenerated electrons from the decorated Ag₃PO₄. A possible photocatalytic mechanism of the Ag₃PO₄/MWCNT photocatalyst was assumed as well.     

Plasmon-enhanced instantaneous photocatalytic activity of Au@Ag<Subscript>3</Subscript>PO<Subscript>4</Subscript> heterostructure targeted at emergency treatment of environmental pollution

The metallic Au-incorporated Au@Ag₃PO₄ heterostructure described in this study exhibited a highly productive photocatalytic activity in the generation process from hydroxyapatite to Ag₃PO₄ caused by the rapid release of hydroxyl groups which were converted into hydroxyl radicals by the combined effect of the LSPR by metallic Au nanoparticles and photoexcitation of Ag₃PO₄ crystals. A conceptually different approach was first demonstrated which we called “instantaneous catalysis” (IC) to degrade rhodamine B, amido black 10b, and bromophenol blue dyes with an extra high degradation rate in about 5 s. It was estimated that the creative photocatalytic activity was due to the effective utilization of the hydroxyl radicals during the synthesis of Au@Ag₃PO₄ heterostructure. The IC process is suitable for the emergency treatment of unexpected serious environmental pollution.     

Effects of sodium oleate on synthesis and photocatalytic activity of Bi<Subscript>2</Subscript>WO<Subscript>6</Subscript>/Bi<Subscript>2</Subscript>O<Subscript>3</Subscript>@RGO

In this study, the effects of sodium oleate on synthesis of Bi₂WO₆/Bi₂O₃ loaded reduced graphene oxide photocatalyst was studied. The as-prepared composites were characterized by X-ray diffraction, Fourier transform infrared, X-ray photoelectron spectroscopy, UV–visible diffuse reflectance and photoluminescence spectroscopy. The results suggested that addition of sodium oleate not only promoted synthesis of Bi₂O₃, but also enhanced the reduction of GO to graphene. When the amount of sodium oleate was 4 mol (Bi:SO?=?1:1), Bi₂WO₆/Bi₂O₃@RGO to the best visible-light photocatalytic activity can be synthesized by a facile one-step solvothermal process without further reduction reaction. Hence, it indicated that sodium oleate could affect the synthesis of the as-prepared composites and the photocatalytic activity for degradation of RhB. This study did provide not only a facile method to synthesize Bi₂WO₆/Bi₂O₃@RGO, but also a method to reduce graphene oxide to graphene.     

A new visible driven nanocomposite including Ti-substituted polyoxometalate/TiO<Subscript>2</Subscript>: synthesis,characterization, photodegradation of azo dye process optimization by RSM and specific removal rate calculations

A new visible driven photocatalyst K₇Ti₂W₁₀PO₄₀/TiO₂ (KPW/TiO₂) with various KPW contents (2, 11 and 20 wt%) was successfully synthesized through a modified sol–gel-hydrothermal method. The structural properties of the prepared nanocomposite were characterized by X-ray diffraction, field emission scanning electron microscopy, Fourier transform infrared, photoluminescence spectroscopy and diffuse reflectance spectra (DRS). From the results obtained, the 11-KPW/TiO₂ showed the highest photocatalytic activity. Photoluminescence analysis for all synthesized samples showed that the 11-KPW/TiO₂ had the lowest intensity and recombination rate of photogenerated electron and holes. Tauc plots of the photocatalysts show that the presence of KPW in the x-KPW/TiO₂ nanocomposites reduced the band gap of nanocomposites, but the change in the amount of KPW have not a specific effect on the band gap reduction. It seems that the change in the loading of the KPW is effective on the amount of recombination of electron–hole. The absorption edge of the modified TiO₂ showed a red shift into the visible light range. Mott–Schottky plots show a positive slope as expected for n-type semiconductor. The prepared photocatalysts were examined for degradation of DR16 under visible light irradiation. The performance of the photocatalyst was analyzed and modeled by response surface methodology. Optimum conditions were DR16 conc. of 20 mg/L, reaction time 4 h, initial pH (3) and polyoxometalate loading 11 wt%. In order to assess the treatment capacity of the nanophotocatalyst, specific removal rate for the DR16 at all operating conditions were calculated.     

Oxalic acid assisted hydrothermal synthesis and optical absorption property of WO<Subscript>3</Subscript>/TiO<Subscript>2</Subscript> nanocomposites

The WO₃/TiO₂ nanocomposites were successfully prepared via a facile oxalic acid assisted hydrothermal process. The oxalic acid played a vital role on the preparation of WO₃/TiO₂ nanocomposites. Notably, it has been observed that the nanocomposites exhibited the wider absorption edge, and the higher photocatalytic activity, compared with pure TiO₂. In addition, the photocatalytic mechanism was proposed, and it elaborated that WO₃/TiO₂ nanocomposite promoted the separation of the photoproduction carriers, and improved photocatalytic activity. The WO₃/TiO₂ nanocomposite may have a potential application as a UV–visible photocatalyst.     

Magnetically separable Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>@TiO<Subscript>2</Subscript> nanospheres: preparation and photocatalytic activity

A facile and efficient approach for the fabrication of Fe₃O₄@TiO₂ nanospheres with a good core–shell structure has been demonstrated. Products were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectra (XPS), X-ray diffraction (XRD) and vibrating sample magnetometer (VSM). The results showed that Fe₃O₄@TiO₂ nanocomposites exhibited high degree of crystallinity, excellent magnetic properties at room temperature. Furthermore, the as-prepared Fe₃O₄@TiO₂ nanocomposites exhibited good photocatalytic activity toward the degradation of Rhodamine B (RhB) solution. Additionally, the recycling experiment of Fe₃O₄@TiO₂ nanocomposites had been done, demonstrating that Fe₃O₄@TiO₂ nanocomposites have high efficiency and stability.     

Enhancement of photocatalytic activity and stability of Ag2CO3 by formation of AgBr/Ag2CO3 heterojunction in mordenite zeolite

Two serious problems for semiconductor photocatalysts are their poor photocatalytic activity and low stability. In this work, Ag₂CO₃ nanoparticles incorporated in mordenite zeolite (MOR) by a facile precipitation method. Silver bromide (AgBr) with different weight percentage (20%, 40% and 50%) was coupled into Ag₂CO₃-MOR composite and producing a series of novel AgBr/Ag₂CO₃-MOR nanocomposites. The effects of AgBr on the Ag₂CO₃–MOR catalyst for the photocatalytic degradation of methyl blue (MB) under visible light irradiation have been investigated. The structure, composition and optical properties of nanocomposites were investigated by UV–Visible diffuse reflectance spectroscopy (UV–Vis DRS), X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM). The prepared AgBr/Ag₂CO₃-MOR photocatalyst with the optimal content of AgBr (50 wt%) indicated higher photocatalytic activity than that of the Ag₂CO₃-MOR and Ag₂CO₃ for degradation of methylene blue (MB) under visible light irradiation. For studying of stability of nanocomposites, Fe⁺³ ions, as a cheap and available cocatalyst, was inserted into mordenite matrix (Fe³⁺/MOR) by impregnation method. The hybrid material (AgBr/Ag₂CO₃) was synthesized in the Fe³⁺/MOR matrix by precipitation method. The cycle experiments on the AgBr/Ag₂CO₃-Fe/MOR nanocomposite indicated that cocatalyst, not only to improve photocatalytic activity, but also enhance photoinduced stability of photosensitive silver compounds in all cycles with respect to MOR. On the basis of the experimental results, a possible mechanism for the enhanced photocatalytic activity and photoinduced stability of silver compounds by Fe³⁺ cocatalyst was proposed. The mordenite support played an important role in decreases of recombination of photogenerated electrons-holes and increases of MB absorption. The Fe cocatalyst reduced photocorrosion of silver compounds.     

Visible-light activities of Gd<Subscript>2</Subscript>O<Subscript>3</Subscript>/BiVO<Subscript>4</Subscript> composite photocatalysts

Gd₂O₃/BiVO₄ composite photocatalysts were hydrothermal synthesized and characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, and UV–vis diffusion reflectance spectra; all the composite photocatalysts exhibited enhanced photocatalytic activities than the pure BiVO₄ for degradation of methyl orange under visible-light irradiation. The improved activity of composites was discussed and ascribed to the electron-scavenging effect of dopants.     

Preparation and characterization of novel HgO/MoO<Subscript>2</Subscript> nanocomposite by ultrasound-assisted precipitation method to enhance photocatalytic activity

In this work, the HgO/MoO₂ as novel nanocomposite has been successfully synthesized for the first time. The nanocomposite has been synthesized using simple ultrasound-assisted precipitation method and using organic molecular [2-hydroxybenzaldehyde] as precursor. The as-prepared nanocomposites were characterized by X-ray-diffraction (XRD), energy dispersive X-ray Microanalysis (EDS), scanning electron microscopy (SEM), UV–Vis diffuse reflectance spectroscopy (DRS), Fourier transform infrared spectroscopy (FT-IR) techniques. Some parameters such as surfactant effect (CTAB, SDS, SDBS and PEG-200) and solvent (distilled water, propylene glycol) effect were investigated to found grain size, shape, purity and reach the optimum conditions. These catalytic systems displayed high activity in the photodegradation of rhodamine B in a liquid phase under UV irradiation. The results show that the photocatalytic activity of HgO/MoO₂ nanocomposite with PEG-200 surfactant has improved than another surfactant to degradation of rhodamine B (RhB) dye under ultraviolet irradiation.     

Ag<Subscript>2</Subscript>S/Bi<Subscript>2</Subscript>S<Subscript>3</Subscript> co-sensitized TiO<Subscript>2</Subscript> nanorod arrays prepared on conductive glass as a photoanode for solar cells

TiO₂ nanorod arrays (TiO₂ NRAs) were synthesized through a hydrothermal method. Ag₂S and Bi₂S₃ were then grown on the surface of TiO₂ NRAs with successive ionic layer adsorption and reaction method. The pristine rutile TiO₂ NRAs, Ag₂S/TiO₂, Bi₂S₃/TiO₂, and Bi₂S₃/Ag₂S/TiO₂ electrodes were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, ultraviolet–visible absorption spectroscopy, and electrochemical analysis. According to photoelectrochemical (PEC) measurement, an enhanced short circuit current density was obtained for the co-sensitized TiO₂ NRAs under simulated sunlight illumination, which was 10.7 times higher than that of the TiO₂ NRAs. Appropriate potential positions of conduction band and valence band of Bi₂S₃ that match well those of rutile TiO₂ NARs and Ag₂S lead to the improved PEC performance. In addition, the PEC property of the co-sensitized TiO₂ NRAs under visible light irradiation was also investigated and showed a dramatically enhanced photocurrent response.     

Green gelatin-assisted: Synthesis of Co3O4NPs@rGO nanopowder for highly efficient magnetically separable methylene orange dye degradation

GO and Co(NO₃)₂ were respectively used as rGO and Co₃O₄ precursors for preparing magnetically separable Co₃O₄NPs attached Co₃O₄NPs@rGO nanocomposites by a straightforward sol–gel technique. To characterize the nanocomposite materials, FESEM, EDX, elemental mapping, XRD, FTIR, Raman spectroscopy, UV–vis, VSM and BET were employed. When exposed to UV rays, the nanocomposite showed extraordinary photocatalytic degradation of MO dye. According to the measurements of photocatalytic activity, the highly efficient photocatalytic efficiency of the nanocomposite could be attributed to preventing electron-hole recombination by highly effective electron transfer between rGO and semiconductor NPs. The nanocomposite succeeded in the efficient degradation of MO dye, even after five photocatalytic cycles.