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The monoclinic nanocrystalline Ni1−xMnxWO4 heterostructure has been successfully synthesized by the hydrothermal technique for achieving better sensitive and photocatalytic performances. Different characterization techniques such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), ultraviolet-visible (UV–Vis), and photoluminescence (PL) spectroscopy have been employed to investigate their structural, microstructural, and optical properties. Mn-ion incorporation in the NiWO4 lattice reduces the particle size of the sample compared with the pure undoped NiWO4 sample, which has been confirmed from the transmission electron microscope image. The Tauc plot of the Ni1−xMnxWO4 sample exhibits a significant decrease in bandgap energy compared with the pure undoped NiWO4 sample due to the quantum confinement effect. Finally, the material was explored as a photocatalyst for the degradation of methyl orange (MO) dye from wastewater under visible light irradiation. Various reaction parameters such as pH, catalyst dose, reaction time, and kinetics of the photodegradation were studied using the batch method. The results showed that the Ni1−xMnxWO4 is highly efficient (94.51%) compared with undoped NiWO4 (65.45%). The rate of photodegradation by Ni1–xMnxWO4 (0.067) was found to be 1.06 times higher than the undoped NiWO4 (0.062). [ABSTRACT FROM AUTHOR]

For the first time, NiO and Ag–Cd co-doped NiO CdxAg0.30Ni0.70−xO (X = 0.0, 0.05, 0.10, and 0.15) have been synthesized through a facile sol–gel method to investigate the photocatalytic performance by visible-light-driven degradation of rhodamine B dye for wastewater treatment. All samples were characterized through X-ray diffraction, field emission scanning electron microscopy, energy-dispersive X-ray, Fourier transform infrared, photoluminescence, and ultraviolet–visible spectroscopy for structural, morphological, elemental, functional groups, optical, and bandgap analysis, respectively. Face-centered cubic structure of NiO was confirmed through X-ray diffraction. The formation of NiO and Ag–Cd co-doped NiO nanoparticles was confirmed through elemental and functional groups analysis. Optical properties obtained from photoluminescence spectroscopy revealed visible-light emission spectrum and slower electron/hole pair recombination rate with an increase in doping. Minimum optical bandgap energy of 2.37 eV was found for the Cd0.15Ag0.30Ni0.55O sample. Photocatalytic performance study revealed that degradation followed first-order kinetics. Cd0.15Ag0.30Ni0.55O was the best sample which showed the maximum efficiency of 97%, the reaction rate constant K (min−1) of 0.0496, and the correlation coefficient (R2) of 0.988 after 140-min degradation of rhodamine B dye. The reusability and stability of the best sample were checked for six cycles by obtaining an X-ray diffraction pattern after the photocatalytic process. [ABSTRACT FROM AUTHOR]

Silver‐containing materials have been the source of attraction due to their excellent optical and photocatalytic properties. Silver vanadium phosphate, Ag2VO2PO4, (hereafter abbreviated as AVP) in nanorods form was synthesized by hydrothermal method at 220 °C for 24 h and characterized by PXRD, FT‐IR, 31P MAS NMR, SEM‐EDS, TEM‐SAED, N2 adsorption‐desorption, UV‐Vis DRS and XPS techniques. It was crystallized in the monoclinic crystal lattice with space group C2/m and the crystal structure consists of layers of edge‐sharing VO6 octahedra and PO4 tetrahedra. The Ag2VO2PO4 nanorods have shown the photocatalytic property against the degradation of Rhodamine B (RhB) dye. The degradation of RhB by AVP after 180 min of visible light irradiation was 45 %. The photocatalytic activity of this material was explained by its visible light absorption, which makes it a promising photocatalyst for use in solar photocatalysis and with a good photocatalytic rate. A mechanism for photodegradation of RhB dye was proposed based on scavenger experiments. It was noticed that.OH radicals are actively participating in the degradation of RhB followed by holes while the role of O2.− radicals is negligible. Antibacterial activity of this material was studied over gram‐positive Staphylococcus aureus and gram‐negative Pseudomonas aeruginosa bacteria. [ABSTRACT FROM AUTHOR]

The monoclinic nanocrystalline Ni1−xMnxWO4 heterostructure has been successfully synthesized by the hydrothermal technique for achieving better sensitive and photocatalytic performances. Different characterization techniques such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), ultraviolet-visible (UV–Vis), and photoluminescence (PL) spectroscopy have been employed to investigate their structural, microstructural, and optical properties. Mn-ion incorporation in the NiWO4 lattice reduces the particle size of the sample compared with the pure undoped NiWO4 sample, which has been confirmed from the transmission electron microscope image. The Tauc plot of the Ni1−xMnxWO4 sample exhibits a significant decrease in bandgap energy compared with the pure undoped NiWO4 sample due to the quantum confinement effect. Finally, the material was explored as a photocatalyst for the degradation of methyl orange (MO) dye from wastewater under visible light irradiation. Various reaction parameters such as pH, catalyst dose, reaction time, and kinetics of the photodegradation were studied using the batch method. The results showed that the Ni1−xMnxWO4 is highly efficient (94.51%) compared with undoped NiWO4 (65.45%). The rate of photodegradation by Ni1–xMnxWO4 (0.067) was found to be 1.06 times higher than the undoped NiWO4 (0.062).

Bismuth halide oxide with three halogen elements (P‐BiOXs) catalyst was prepared by a facile precipitation method at room temperature only for 30 min. Several measurement technologies were employed to characterise the structures and morphologies of the obtained samples. Coloured Rhodamine B (RhB), methyl orange (MO), methylene blue (MB) and colourless bisphenol A (BPA) were selected to evaluate the photocatalytic activity of the samples. The experimental results showed the P‐BiOXs thin nanoplates exhibited the most excellent photocatalytic activity among the prepared samples for the degradation of MO under visible light illumination. More importantly, the catalyst P‐BiOXs could effectively degradate RhB, MB and BPA. The P‐BiOXs catalyst displayed good photocatalytic stability by the recycling tests. The highly efficient visible light catalytic properties of P‐BiOXs could be due to the high specific surface area, enhanced light‐harvesting ability, the suitable bandgap energy and the lower recombination rate of the photogenerated electrons and holes. [ABSTRACT FROM AUTHOR]

In this study, KHf0.5Te1.5O6 (KHTO) semiconductor has been synthesized by the solid-state method. The synthesized material is characterized using X-ray diffraction, Fourier transform infrared spectroscopy, UV-visible diffuse reflectance spectroscopy, field emission-scanning electron microscopy, energy dispersive spectroscopy, X-ray photoelectron spectroscopy and N2 adsorption/desorption measurements. The material is found to be crystallized in a cubic lattice with the space group Fd3m. The bandgap energy of the KHTO is 2.6 eV. The photocatalytic activity of KHTO has been investigated by measuring the degradation of methylene blue (MB) and methyl violet (MV) dyes under the visible light irradiation. The mechanistic dye degradation pathway of MB has been studied. The radical quenching experiments reveal that the short-lived species O2 -, OH, and h+ actively participate in the degradation of MB and MV dyes. An additional terephthalic acid experiment has been carried out to establish the participation of OH? radicals in the dye degradation. The stability and reusability of the KHTO catalyst are also studied. [ABSTRACT FROM AUTHOR]

In this study, KHf0.5Te1.5O6 (KHTO) semiconductor has been synthesized by the solid-state method. The synthesized material is characterized using X-ray diffraction, Fourier transform infrared spectroscopy, UV-visible diffuse reflectance spectroscopy, field emission-scanning electron microscopy, energy dispersive spectroscopy, X-ray photoelectron spectroscopy and N2 adsorption/desorption measurements. The material is found to be crystallized in a cubic lattice with the space group Fd3m. The bandgap energy of the KHTO is 2.6 eV. The photocatalytic activity of KHTO has been investigated by measuring the degradation of methylene blue (MB) and methyl violet (MV) dyes under the visible light irradiation. The mechanistic dye degradation pathway of MB has been studied. The radical quenching experiments reveal that the short-lived species O2 -, OH, and h+ actively participate in the degradation of MB and MV dyes. An additional terephthalic acid experiment has been carried out to establish the participation of OH? radicals in the dye degradation. The stability and reusability of the KHTO catalyst are also studied. [ABSTRACT FROM AUTHOR]

In recent years, metal–nonmetal codoping has become a promising approach that can be used for effective tailoring of the structure–activity properties of semiconductors in photocatalysis. In the present study, N-doped K 2 Nd 2 Ti 3 O 10 (KNdTON), Ag-doped K 2 Nd 2 Ti 3 O 10 (AgNdTO), as well as N and Ag codoped K 2 Nd 2 Ti 3 O 10 (AgNdTON) photocatalysts were successfully synthesized by solid-state and ion-exchange methods, using the pre-prepared K 2 Nd 2 Ti 3 O 10 (KNdTO). The parent K 2 Nd 2 Ti 3 O 10 catalyst was synthesized using a facile gel-burning method. The prepared materials are characterized by different techniques such as powder X-ray diffraction (XRD), thermogravimetric (TG) analysis, scanning electron microscopy–energy dispersive X-ray (SEM–EDX) spectroscopy, transmission electron microscopy (TEM), high- resolution-TEM (HR–TEM), oxygen–nitrogen–hydrogen (O–N–H) analysis, inductively coupled plasma-optical emission spectroscopy (ICP-OES), Fourier transform-infrared spectroscopy (FT-IR), and diffuse reflectance UV–visible spectroscopy (UV–vis DRS). The photocatalytic activity of the obtained catalysts was investigated by studying the degradation of two different pollutants viz., methylene blue (MB) and methyl violet (MV) under visible light irradiation. The shift in the XRD peaks and absorption edges confirms the incorporation of guest ions into the lattice of KNdTO. The photocatalytic degradation of MB and MV is found to be significantly improved via metal mono-doping and codoping. In particular, AgNdTON showed a remarkable increase in photodegradation compared to KNdTON, AgNdTO, and KNdTO. Such an improved photocatalytic activity of AgNdTON is due to the extended visible light absorption and the lower bandgap energy. Furthermore, AgNdTON demonstrated reasonable photocatalytic activity for the MV degradation up to five cycles. [ABSTRACT FROM AUTHOR]

Perovskite type oxides, sodium bismuth titanate (Na0.5Bi0.5TiO3), and Ag+, Cu2+, and Sn2+ doped Na0.5Bi0.5TiO3 were prepared by pechini and ion exchange methods, respectively. Photocatalytic activities of these catalysts were tested by decomposition of methylene blue (MB) under visible light irradiation. Results showed that the photocatalytic activity of metal ion doped Na0.5Bi0.5TiO3 was higher than undoped Na0.5Bi0.5TiO3. Relatively high photocatalytic performance of Ag+‐doped Na0.5Bi0.5TiO3 is mainly ascribed to the efficient separation of electron‐hole (e–, h+) pairs, lower bandgap energy and the creation of active hydroxyl radicals (•OH). Further, the Ag+‐doped Na0.5Bi0.5TiO3 catalyst showed good reusability up to four cycles. A possible mechanism for the enhanced photocatalytic performance was proposed. The synthesized photocatalysts were characterized by XRD, SEM, EDS, XPS, FT‐IR, and UV/Vis DRS techniques. [ABSTRACT FROM AUTHOR]

The urea-modified ZnWO4 samples were synthesized by hydrothermal method. Urea was used as a nitrogen source. These materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FT-IR), and UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS). Photocatalytic properties of urea-modified ZnWO4 was studied and compared with its parent ZnWO4. Urea-modified ZnWO4 (10 mol%) has shown higher photocatalytic activity in the degradation of methylene blue under the visible light irradiation. Participation of holes, hydroxyl radicals, and super oxide radicals in the photocatalytic dye degradation was investigated. [ABSTRACT FROM AUTHOR]

The photocatalytic activity of isomorphously substituted transition metal (TM) ions into the vanadosilicate AM-6 framework, at TM/V ratios of 0.025-0.10, has been investigated. All 0.025TM-substituted AM-6 products showed enhanced photocatalytic activity under UV light irradiation which was attributed to the bandgap photoexcitation of these products. The photocatalytic activity decreased with increasing TM concentrations (TM > 0.025). Under visible light irradiation, only 0.025Cr-AM-6 showed enhanced photocatalytic activity ( k = 4.6 × 10 −3 min −1 ± 4.0 × 10 −4 min −1 ). This was attributed to the electron excitation for the interfacial charge-transfer in the visible light region. 0.025Fe-AM-6 ( k = 3.1 × 10 −3 min −1 ± 4.0 × 10 −4 min −1 ), 0.025Co-AM-6 ( k = 3.4 × 10 −3 min −1 ± 6.0 × 10 −4 min −1 ), and unmodified AM-6 ( k = 2.9 × 10 −3 min −1 ± 7.0 × 10 −4 min −1 ) were inactive towards the photodegradation of methylene blue under visible light irradiation (direct photolysis k = 2.8 × 10 −3 min −1 ± 4.0 × 10 −4 min −1 ). This was likely attributed to the ineffectiveness of the electron excitation for the interfacial charge-transfer, as suggested by the UV–vis spectroscopic analyses. [ABSTRACT FROM AUTHOR]

Brannerite-type layered vanadomolybdate, KVMoO6, was synthesized by sol-gel method using ethylene glycol as gelating agent. Its silver- and nitrogen-doped analogues were prepared by ion exchange and solid state methods, respectively. All compounds were characterized by powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), energy dispersive spectroscopy (EDS), Fourier transform IR spectroscopy (FT-IR), and UV-vis diffuse reflectance spectra. The bandgap energy of all compounds was obtained from their diffuse reflectance spectra. Bandgap was reduced considerably upon silver and nitrogen doping in KVMoO6. The photocatalytic activity of parent and doped samples was studied by degradation of methylene blue. The nitrogen-doped KVMoO6 shows higher photocatalytic activity against the degradation of methylene blue. The stability and reusability of the nitrogen-doped KVMoO6 were investigated. N-doped KVMoO6 is a potential catalytic material for cleaning wastewater. [ABSTRACT FROM AUTHOR]

Silver/copper-nitrogen co-doped Na3SbO(PO4)2 were prepared by solid state/ion exchange methods. The materials were characterized by powder XRD, SEM-EDS, TG analysis, as well as FT-IR and UV/Vis diffuse reflectance spectroscopy. All the doped materials crystallize in orthorhombic lattice with space group P212121. The infrared spectra of the samples gave characteristic bands corresponding to PO4 and SbO6 groups. The bandgap energy of all the samples was deduced from their UV/Vis DRS profiles. The bandgap energy of doped materials decreased substantially. Visible-light-induced photocatalytic oxidation of the methyl violet (MV) and methylene blue (MB) was examined. The influence of cation, anion, and co-doping on the photoactivity of Na3SbO(PO4)2 was studied. The Ag+ and nitrogen co-doped Na3SbO(PO4)2 exhibited the highest photocatalytic activity among the materials investigated. [ABSTRACT FROM AUTHOR]

Silver/copper-nitrogen co-doped Na3SbO(PO4)2 were prepared by solid state/ion exchange methods. The materials were characterized by powder XRD, SEM-EDS, TG analysis, as well as FT-IR and UV/Vis diffuse reflectance spectroscopy. All the doped materials crystallize in orthorhombic lattice with space group P212121. The infrared spectra of the samples gave characteristic bands corresponding to PO4 and SbO6 groups. The bandgap energy of all the samples was deduced from their UV/Vis DRS profiles. The bandgap energy of doped materials decreased substantially. Visible-light-induced photocatalytic oxidation of the methyl violet (MV) and methylene blue (MB) was examined. The influence of cation, anion, and co-doping on the photoactivity of Na3SbO(PO4)2 was studied. The Ag+ and nitrogen co-doped Na3SbO(PO4)2 exhibited the highest photocatalytic activity among the materials investigated. [ABSTRACT FROM AUTHOR]

Quaternary oxides containing transition metal and tungsten with the general formula AMWO 6 ( A = K, Rb, Cs; M = Sb, Nb, Ti) have been studied as photocatalysts for decomposition of organic dyes. In this paper, defect pyrochlore of composition KTi 0.5 W 1.5 O 6 was prepared via facile sol–gel method. Its nitrogen and tin doped analogues were prepared by solid state and ion exchange methods respectively. All compounds were characterized by powder X-ray diffraction, Thermogravimetric analysis, FT-IR, Raman, Scanning electron microscopy and UV–Vis diffuse reflectance spectra. X-ray photoelectron spectroscopy and energy dispersive spectroscopy were also used to characterize the incorporation of doped ions into the defect pyrochlore lattice. The photocatalytic activity of all compounds was studied by degradation of methylene blue and Rhodamine B. The tin doped KTi 0.5 W 1.5 O 6 shows higher photocatalytic activity against both the dyes. The experimental results show that the higher photocatalytic activity of tin doped KTi 0.5 W 1.5 O 6 is due to more absorption of light energy in the visible region attributable to the lowering of bandgap energy. Further, the role of reactive intermediate species in the photocatalytic degradation of dyes was studied using their appropriate scavengers and the obtained results show that OH radicals produced in the photocatalytic reaction play dominant role. [ABSTRACT FROM AUTHOR]

BACKGROUND Sn-doped metal oxides have attracted considerable attention due to their potential applications in environmental remediation by degrading organic pollutants to less harmful byproducts and hydrogen generation from water splitting. Divalent tin was doped into defect pyrochlore K0. 51Sb2. 67O6.26 ( KSO) to improve its visible light photocatalytic activity. RESULTS The Sn-doped K0. ( SSO) was obtained from parent KSO by an ion exchange method. The bandgap energy of KSO was reduced from 3.64 to 2.68 eV following Sn51 doping into the KSO latttice. The photocatalytic activity of KSO and SSO was studied by degradation of methylene blue ( MB) and rhodamine B ( RhB) under visible light irradiation. SSO showed higher photodegrdation of MB and RhB whereas pristine KSO was almost inactive for the degradation of both dyes. CONCLUSIONS The MB and RhB degradation efficiency of SSO was 86 and 53%, respectively. The higher photocatalytic activity of SSO is attributed to more absorption of light energy in the visible region due to lowering of the bandgap energy as well as the generation of 2. 67O6.26 ( SSO) was obtained from parent KSO by an ion exchange method. The bandgap energy of KSO was reduced from 3.64 to 2.68 eV following Sn2+ doping into the KSO latttice. The photocatalytic activity of KSO and SSO was studied by degradation of methylene blue ( MB) and rhodamine B ( RhB) under visible light irradiation. SSO showed higher photodegrdation of MB and RhB whereas pristine KSO was almost inactive for the degradation of both dyes. CONCLUSIONS The MB and RhB degradation efficiency of SSO was 86 and 53%, respectively. The higher photocatalytic activity of SSO is attributed to more absorption of light energy in the visible region due to lowering of the bandgap energy as well as the generation of • OH radicals during the photocatalytic reaction. Even after a fourth cycle of photodegradation of MB, the photocatalyst ( SSO) was found to be stable, with a marginal decrease in the rate of degradation. © 2013 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Nano sized defect pyrochlores of compositions KCrWO and ACrWO· nHO (A = Sn, Ag, Bi, Sm, Eu, and Gd) have been synthesized by sol-gel and ion exchange methods, respectively. These oxides were characterized by thermogravimetric analysis, powder X-ray diffraction, energy dispersive spectra, transmission electron microscopy, UV-Vis diffuse reflectance spectra, Raman spectra, and Fourier transform infrared spectra. Spontaneous exchange of K with A ion is accompanied by insertion of water also into the lattice. KCrWO and ACrWO· nHO crystallize in cubic lattice and isomorphous with KSbWO. The optical properties of Cr were investigated. Substitution of K by A ion leads to a shift of absorption onset to longer wavelengths marginally. The Raman spectra of all the samples are characteristic of defect pyrochlore system. The photocatalytic degradation of methylene blue aqueous solution was investigated using these oxides. The results obtained were fitted with the Langmuir-Hinshelwood model to study the degradation kinetics. Both Sn and Bi-doped KCrWO exhibit higher photoactivity in the degradation of methylene blue. The structure/composition of the photocatalyst remains the same even after fourth cycle of photodegradation. [ABSTRACT FROM AUTHOR]

Abstract: N-doped In2Ga2ZnO7 photocatalysts were fabricated by solid state reaction route. All the prepared photocatalysts were successfully characterised by PXRD, optical absorption spectra, SEM, TEM, XPS, BET surface area and photoresponse studies. The formation of In2Ga2ZnO7 was confirmed by the PXRD pattern. Optical absorption spectra showed that the visible light absorption of all the photocatalysts were enhanced by nitrogen doping. Among all the prepared photocatalysts, 1 wt% Pt loaded N-GaInZn-500 showed enhanced photocatalytic activity towards hydrogen evolution under visible light irradiation in presence of 10 vol% methanol solution as sacrificial agent. The excellent photocatalytic activity of N-GaInZn-500 is in agreement with N-content, bandgap energy, PL intensity and Surface area. [Copyright &y& Elsevier]