Synthesis and characterization of Co-doped nano-TiO<Subscript>2</Subscript> through co-precipitation method for photocatalytic activity

The aim of this work was synthesis and investigation of various properties of Co-doped titanium dioxide nanostructures. Synthesis was conducted by the co-precipitation method using cobalt nitrate and titanium isopropoxide as a precursor, followed by thermal treatment at a temperature of 500 °C. The materials were fully characterized using several techniques (X-ray diffraction XRD, SEM, FTIR, TGA/DTA, UV–Vis diffuse reflectance DRS and photoluminescence). However, dopant has no effect on XRD pattern of the host but it can influence on the various characteristics of host such as optical and electrical properties. The scanning electron microscopy was used to detect the morphology of synthesized nanoparticles which sizes changed with the altitude in the doping concentration to 6%. FTIR spectra exhibit broad peaks where anatase phases of TiO₂ demonstrate very sharp UV–Vis band gap results showed the reduction in band gap from from 3.21 eV, for undoped TiO₂, to 2.74 eV, for Co doped 6% TiO₂. The photocatalytic activity of the samples were studied based on the degradation of methyl orange as a model compound, where the results showed that Co doped 6% TiO₂ a good photocatalytic activity.     

Facile synthesis,characterization and BET study of neodymium-doped spinel Mn<Subscript>3</Subscript>O<Subscript>4</Subscript> nanomaterial with enhanced photocatalytic activity

In this study, bare Mn₃O₄ and Neodymium (Nd)-doped Mn₃O₄ were prepared via a facile hydrothermal strategy. These materials were characterized by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, UV spectroscopy, X-ray photoelectron spectroscopy, and the Brunauer–Emmett–Teller (BET) method. XRD pattern displays that the particles were well crystallized and corresponds to a spinel structure of Mn₃O₄. The BET specific surface area and pore volume of mesoporous Mn₃O₄ greatly exceeds that of Nd-doped Mn₃O₄ samples. The sonophotocatalytic activity of Nd-doped Mn₃O₄ nanoparticles was evaluated by monitoring the decolorization of Reactive Red 43 in aqueous solution under sono-photocatalytic process. 4% Nd-doped Mn₃O₄ nanoparticles showed the highest decolorization efficiency among the different amounts of dopant agent used. The Nd-doped Mn₃O₄ could be a promising candidate material for high-capacity, low-cost, and environmentally friendly catalyst for wastewater remediation.     

Nanocrystalline ErVO<Subscript>4</Subscript>: synthesis,characterization, optical and photocatalytic properties

Nanoparticles sphere-like erbium vanadate (ErVO₄) have been successfully synthesized via the co-precipitation method process by using erbium nitrate hexahydrate, NH₄VO₃ in water. Besides, three surfactants such as polyethylene glycol, sodium dodecyl sulfate and cetyltrimethyl ammonium bromide were used to investigate their effects on the morphology and particle size of ErVO₄ nanoparticles. According to the vibrating sample magnetometer, erbium vanadate ErVO₄ nanoparticles indicated a paramagnetic behavior at room temperature. The as-synthesized nanoparticles were characterized by X-ray diffraction, scanning electron microscopy, diffuse reflectance spectroscopy, and energy dispersive X-ray microanalysis. To evaluate the catalytic properties of nanocrystalline erbium vanadate ErVO₄ the photocatalytic degradations of methyl orange under ultraviolet light irradiation were carried out.     

Morphological control of Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> particles via glycothermal process

Acicular magnetite (Fe₃O₄) powders were synthesized through new glycothermal dehydration by using crystalline α-FeOOH as precursor and glycols as solvent. When ethylene glycol was used as solvent, the phase was in-situ transformed from acicular α-FeOOH to α-Fe₂O₃ and finally to Fe₃O₄ at 270 °C for 6 h without morphological change. When water was added as a co-solvent in glycothermal reaction, Fe₃O₄ powders were synthesized through dissolution–recrystallization process at 230 °C for 3 h. The volume ratio of ethylene glycol to water (E/W) in the reaction has a strong effect on the morphology of the synthesized Fe₃O₄ particles. The particle shape of Fe₃O₄ particles changed from needle to sphere when the water content in E/W volume ratio increased from 0.5 to 1 mL in mixed glycothermal condition. When the water were added by more than 10 ml, the particle shape of Fe₃O₄ changed from sphere to octahedron truncated with the {100} faces and finally distinct octahedron with only {111} faces. Also, it is demonstrated that the size of Fe₃O₄ particles can be controlled from 1–2 μm to 100–200 nm by varying the reaction conditions such as the volume ratio of water to ethylene glycol and additive in glycothermal reaction.     

A simple sonochemical synthesis and characterization of CdWO<Subscript>4</Subscript> nanoparticles and its photocatalytic application

Cadmium tungstate (CdWO₄) nanoparticles were synthesized via a sonochemical method based on the reaction between cadmium(II) nitrate hexahydrate and sodium tungstate dihydrate in an aqueous solution. To the best of authors’ knowledge, it is the first time that cadmium tungstate was synthesized by ultrasonic method. The structural, morphological, and optical properties of as-obtained products were characterized by X-ray diffraction, Scanning electron microscopy, Fourier transform infrared spectroscopy, energy dispersive X-ray microanalysis (EDS), and ultraviolet–visible spectroscopy. The as-synthesized cadmium tungstate indicated a ferromagnetic behavior which evidenced by using vibrating sample magnetometer at room temperature. To evaluate the photocatalysts properties of nanocrystalline cadmium tungstate, the photocatalytic degradation of methyl orange under ultraviolet light irradiation was carried out.     

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.     

In-situ construction of 2D direct Z-scheme g-C<Subscript>3</Subscript>N<Subscript>4</Subscript>/g-C<Subscript>3</Subscript>N<Subscript>4</Subscript> homojunction with high photocatalytic activity

Constructing all-solid-state Z-scheme junction is a very effective strategy to design highly active photocatalysts for solar energy conversion and environmental purification. We herein firstly construct 2D g-C₃N₄/g-C₃N₄ Z-scheme homojunction by using a bottom-up approach, during which the supramolecular complex is initially formed, followed by a facile thermal polycondensation. Based on the active species trapping experiments, Mott–Schottky test and band edge position analysis, the prepared 2D nanosheet g-C₃N₄/g-C₃N₄ homojunctions are found to be Z-scheme type, different from those available reported ones with a type-II energy alignment. Benefiting from the specific 2D morphology with large exposed surface area and Z-scheme junction with efficient separation and high redox abilities of the photoinduced electrons and holes, the obtained 2D g-C₃N₄/g-C₃N₄ homojunctions are much more active than the conventional g-C₃N₄/g-C₃N₄ homojunction (CN-MT) and bulk g-C₃N₄ (CN-M) under visible light irradiation, validating by the high rhodamine degradation rate of 0.833 h^?1, which is about 3.9 and 15.4 times higher than that of CN-MT (0.214 h^?1) and CN-M (0.054 h^?1), respectively. The present work sheds light on design of novel Z-scheme photocatalysts with specific morphology and thus further application in the field of environment or energy.     

Enhanced visible light photocatalytic activity for g-C<Subscript>3</Subscript>N<Subscript>4</Subscript>/SnO<Subscript>2</Subscript>:Sb composites induced by Sb doping

In this paper, g-C₃N₄/SnO₂:Sb composite photocatalysts were fabricated by in situ loading Sb-doped SnO₂ (SnO₂:Sb) nanoparticles on graphitic carbon nitride (g-C₃N₄) nanosheets via a facile hydrothermal method. The synthesized g-C₃N₄/SnO₂:Sb composites delivered enhanced visible light photocatalytic performance for degradation of rhodamine B in comparison with g-C₃N₄/SnO₂ composites without doping Sb. Various techniques including XRD, SEM, TEM, FTIR, XPS, PL and electrochemical method were employed to demonstrate the successful fabrication of g-C₃N₄/SnO₂:Sb composite and to investigate the enhanced mechanism of photocatalytic activity. The improvement of visible light absorption and the promotion of separation efficiency and interfacial transfer of photogenerated carriers induced by Sb doping were responsible for the enhancement of photocatalytic activity. This study provides a simple and convenient method to synthesize a visible light responsive catalyst with promising performance for the potential application in environmental protection.     

Ionic liquid microemulsion-assisted synthesis and improved photocatalytic activity of ZnIn<Subscript>2</Subscript>S<Subscript>4</Subscript>

This paper reported the fabrication of high-performance ZnIn₂S₄ photocatalysts using ionic liquid microemulsion-mediated hydrothermal method under facile conditions. The influences of reaction temperature and aging time on the catalytic properties of the specimens were investigated. The crystal phase, optical property, and morphological structure of the obtained catalysts were characterized using X-ray diffraction, UV–visible spectrometer, electronic microscope, and N₂ adsorption–desorption techniques. The results indicated that all of the ZnIn₂S₄ samples prepared by this method consisted of the hexagonal phase and exhibited excellent photoresponse capability and photocatalytic performance. The sample prepared at 60 °C with an aging time of 6 h showed the best photocatalytic performance, and the corresponding degradation rate of methyl orange was measured as 98.5% after 10 min. The current study highlights an efficient and environmental method for the formulation of high-performance ZnIn₂S₄.     

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.     

Preparation,characterization and photocatalytic properties of nanoplate Bi<Subscript>2</Subscript>MoO<Subscript>6</Subscript> catalysts

Bismuth molybdate (Bi₂MoO₆) nanoplates have been successfully synthesized by a simple hydrothermal process. The nanoplates were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, and IR spectroscopy. The effects of hydrothermal temperature and reaction time on the structures and morphologies of the nanoplates were investigated. On the basis of TEM observation of time series samples, a possible formation mechanism of the nanoplates was proposed. Optical absorption experiments revealed that Bi₂MoO₆ nanoplates had absorption in visible-light region, but a blue shift appeared compared with the corresponding bulk materials. Photocatalytic experiments showed that the nanoplates exhibited good photocatalytic activities for degradation of N,N,N′,N′-tetraethylated rhodamine (RhB) under visible-light irradiation (λ > 420 nm).     

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.     

Synthesis,characterization, and investigation of magnetic and photocatalytic property of YbVO<Subscript>4</Subscript> nanoparticles

Nanocrystalline ytterbium vanadate (YbVO₄) was prepared by simple approach based on the reaction between ytterbium nitrate hexahydrate and ammonium metavanadate in water. Besides, three capping agents such as arginine, cysteine, and asparagine were used to investigate their effects on the morphology and particle size of ytterbium vanadate nanoparticles. The formation of pure crystallized YbVO₄ nanocrystals occurred when the precursor was heat-treated at 550 °C in air for 300 min. According to the vibrating sample magnetometer, ytterbium vanadate nanoparticles indicated a paramagnetic behavior at room temperature. Furthermore, the photocatalysis results reveal that the maximum decolorization of 83 % for methyl orange occurred with ytterbium vanadate nanoparticles in 60 min under ultraviolet (UV) light irradiation. The structural, morphological, and optical properties of as-obtained products were characterized by techniques such as XRD, SEM, EDX, and UV–Vis spectroscopy.     

Ce and Eu activated Na<Subscript>2</Subscript>Zn<Subscript>5</Subscript>(PO<Subscript>4</Subscript>)<Subscript>4</Subscript>, a new promising novel phosphor

A new efficient phosphor, Eu²⁺/Eu³⁺ and Ce³⁺ activated Na₂Zn₅(PO₄)₄ has been synthesized by solid-state reaction technique at high temperature. X-ray powder diffraction analysis confirmed the formation of Na₂Zn₅(PO₄)₄ host lattice. Scanning electron microscopy indicated that the microstructure of the phosphor consisted of irregular fine grains with a size of about 0·5–2 μm. Photoluminescence excitation spectrum measurements of Ce³⁺ activated Na₂Zn₅(PO₄)₄ show that the phosphor can be efficiently excited by UV-Vis light from 280 to 310 nm to realize emission in the visible (blue) range due to the 5d-4f transition of Ce³⁺ ions which is applicable for scintillation purpose, whereas Eu²⁺/Eu³⁺ activated Na₂Zn₅(PO₄)₄ phosphor emits blue, green and red emission spectrum shows at 487 nm, 546 nm with a dominant peak at 611 nm respectively, due to Eu²⁺/Eu³⁺ ions which is promising candidate for solid state lighting. Therefore, newly synthesised, by low cost and easy technique prepared, novel phosphors may be useful as RGB phosphor for solid state lighting application.     

Synthesis of graphene oxide/Ag<Subscript>3</Subscript>PO<Subscript>4</Subscript> composite with enhanced visible-light photocatalytic activity

The nano-scale Ag₃PO₄ was successfully synthesized by the silver ammonia complexing precipitation method at room temperature. And the Graphene oxide (GO)/Ag₃PO₄ nanocomposites with different contents of GO were successfully synthesized using the electrostatic driving method. The as-prepared GO/Ag₃PO₄ nanocomposites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and UV–visible diffuse reflectance spectroscopy (UV–Vis DRS), confirming that Ag₃PO₄ were highly dispersed to GO sheet. The photocatalytic properties of GO/Ag₃PO₄ were evaluated by the degradation of Methyl Orange (MO) under visible light irradiation and solar irradiation respectively. The results showed that the photocatalytic efficiencies of GO/Ag₃PO₄ nanocomposites had enhanced largely and the kinetics reaction models were followed first-order. Furthermore, 5% GO/Ag₃PO₄ exhibited the highest photocatalytic activity on degradation of MO under visible-light irradiation. The improved photocatalytic performances of the GO/Ag₃PO₄ nanocomposites mainly attributed to the introducing of GO, which benefit for electron transfer and inhibit the recombination of electron–hole pairs, promoting the practical application of Ag₃PO₄ in water purification.     

Sonochemical-assisted synthesis and characterization of CeO<Subscript>2</Subscript> nanoparticles and its photocatalytic properties

In the present study, cerium oxide (CeO₂) nanoparticles were prepared through sonochemical-assisted method, using (NH₄)₂Ce(NO₃)₆, hydrazine and ethylenediamine as precursors. Also, the effects of concentration of precursors as well as reaction time on the morphology and size of nanoparticles were investigated. The synthesized CeO₂ nanoparticles were characterized by X-ray diffraction patterns, energy-dispersive X-ray spectroscopy, scanning electron microscopy, Fourier transform infrared spectroscopy and diffuse reflectance spectroscopy. The results indicate that the estimated particle size of synthesized CeO₂ nanoparticles is about 20–30 nm. Furthermore, photocatalytic activities of CeO₂ nanoparticles were investigated by degradation of methylene blue under UV-light irradiation.     

Magnetic and photocatalytic properties of nanocrystalline ZnMn<Subscript>2</Subscript>O<Subscript>4</Subscript>

The present study describes the synthesis of ZnMn₂O₄ nanoparticles with the spinel structure. These oxide nanoparticles are obtained from the decomposition of metal oxalate precursors synthesized by (a) the reverse micellar and (b) the coprecipitation methods. Our studies reveal that the shape, size and morphology of precursors and oxides vary significantly with the method of synthesis. The oxalate precursors prepared from the reverse micellar synthesis method were in the form of rods (micron size), whereas the coprecipitation method led to spherical nanoparticles of size, 40–50 nm. Decomposition of oxalate precursors at low temperature (∼ 450°C) yielded phase pure ZnMn₂O₄ nanoparticles. The size of the nanoparticles of ZnMn₂O₄ obtained from reverse micellar method is relatively much smaller (20–30 nm) as compared to those made by the co-precipitation (40–50 nm) method. Magnetic studies of nanocrystalline ZnMn₂O₄ confirm antiferro-magnetic ordering in the broad range of ∼ 150 K. The photocatalytic activity of ZnMn₂O₄ nanoparticles was evaluated using photo-oxidation of methyl orange dye under UV illumination and compared with nanocrystalline TiO₂. Dedicated to Prof. C N R Rao on his 75th birthday     

Multifunctional performance of gC<Subscript>3</Subscript>N<Subscript>4</Subscript>-BiFeO<Subscript>3</Subscript>-Cu<Subscript>2</Subscript>O hybrid nanocomposites for magnetic separable photocatalytic and antibacterial activity

Highly active gC₃N₄-BiFeO₃-Cu₂O nanocomposites were successfully prepared via a facile, cost effective and eco-friendly method of hydrothermally wet precipitation combined with ultrasonic dispersion process. The prepared samples were characterized by XRD, FTIR, HRSEM, EDS, TEM, UV–Vis DRS, PL, VSM, BET and electrochemical properties. By means of these analysis for examine the crystal phase, nanostructure, band gap and light-harvesting properties were carried out. UV-DRS spectra indicate that the bandgap of g-C₃N₄ (2.7 eV) reduced to 2.59 and 2.21 eV by mixed with corresponds to BiFeO₃ and BiFeO₃/Cu₂O nanomaterials. The ideal photocatalytic activity of the gC₃N₄-BiFeO₃-Cu₂O nanocomposites, where RhB dye under visible light irradiation which was up to 4.36 and 2.52 times as the higher photodegradation ability to compare pristine g-C₃N₄ and gC₃N₄-BiFeO₃ catalyst. The magnetization was confirmed by VSM studies, and hence, after the photocatalytic reaction, the magnetically separable catalyst can be quickly separated from the water by an external magnetic field. The superior photocatalytic performance is due to the synergistic effect on the interface of BiFeO₃/Cu₂O in the gC₃N₄-BiFeO₃-Cu₂O nanocomposites has reduced the bandgap which enables high separation efficiency of the charge carrier, suppressed recombination rate and their high surface area. Moreover, the chief gC₃N₄-BiFeO₃-Cu₂O catalyst can exhibited the lesser charge transfer resistance (impedance), enhances of photocurrent responses, whereas exposed to the development of photocatalytic appearance and more charge carrier ability. Also, the antibacterial activity of the gC₃N₄-BiFeO₃-Cu₂O nanocomposite has showing a well deactivation in both G⁺ (S. aureus) and G^? (E. coli) bacteria’s whereas compare to other prepared samples.     

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.     

In-situ synthesis of CdS/g-C<Subscript>3</Subscript>N<Subscript>4</Subscript> hybrid nanocomposites with enhanced visible photocatalytic activity

A novel and simple in situ synthetic strategy was used to fabricate CdS/g-C₃N₄ hybrid nanocomposite catalysts with visible-light-driven photocatalytic activity from cadmium-containing carbon nitride compounds. X-ray diffraction measurements, high-resolution transmission electron microscopy images, and Fourier transform infrared spectra showed heterojunctions with a close interface between the g-C₃N₄ and the CdS nanoparticles and nanorods in the composite. Ultraviolet visible diffuse reflectance spectra exhibited a red shift that further presented the CdS in the polymer g-C₃N₄ skeleton, which allowed the efficient utilization of the solar spectrum for creating photogenerated electrons and holes. The photoluminescence spectra of the nanocomposites suggested charge transfer from g-C₃N₄ to CdS. The photocurrent intensity of hybrid nanocomposites was 2.3 times than that of pure g-C₃N₄ sample, and photocatalytic activity for the photodegradation of methyl orange was 2.5 times, and hydrogen evolution reaction was 2.8 times. Enhanced photocatalytic activity and photocurrent for the CdS/g-C₃N₄ hybrid nanocomposites were achieved.