SnO<Subscript>2</Subscript>-based thin films with excellent photocatalytic performance

SnO₂ semiconductor is a new-typed promising photocatalyst, but wide application of SnO₂-based photocatalytic technology has been restricted by low visible light utilization efficiency and rapid recombination of photogenerated electrons–holes. To overcome these drawbacks, we prepared B/Fe codoped SnO₂–ZnO thin films on glass substrates through a simple sol–gel method. The photocatalytic activities of the films were evaluated by degradation of organic pollutants including acid naphthol red (ANR) and formaldehyde. UV–Vis absorption spectroscopy and photoluminescence (PL) spectra results revealed that the B/Fe codoped SnO₂–ZnO film not only enhanced optical absorption properties but also improved lifetime of the charge carriers. X-ray diffraction (XRD) results indicated that the nanocrystalline SnO₂ was a single crystal type of rutile. Field emission scanning electron microscopy (FE-SEM) results showed that the B/Fe codoped SnO2–ZnO film without cracks was composed of smaller nanoparticles or aggregates compared to pure SnO2 film. Brunauer–Emmett–Teller (BET) surface area results showed that the specific surface area of the B/Fe codoped SnO₂–ZnO was 85.2 m² g^?1, while that of the pure SnO₂ was 20.7 m² g^?1. Experimental results exhibited that the B/Fe codoped SnO₂–ZnO film had the best photocatalytic activity compared to a pure SnO₂ or singly-modified SnO₂ film.     

Efficient growth of aligned SnO2 nanorod arrays on hematite (α-Fe2O3) nanotube arrays for photoelectrochemical and photocatalytic applications

SnO₂ nanorod arrays were fabricated on hematiete nanotube arrays by an efficient hydrothermal method. The hematiete nanotube arrays were prepared by anodization of pure iron foil in an ethylene glycol solution. SnO₂ nanorod arrays grew from the bottom of hematite nanotubes and were firmly combined with the iron foil substrate. The morphology and microstructure of SnO₂ nanorod arrays are investigated by field-emission scanning electron microscopy, grazing incidence X-ray diffraction and UV–Vis absorbance spectra. The sample presented typical SnO₂ nanorod arrays (reacted for 2 h) generally of 400 nm in length and 50 nm in side width showed the best photocatalytic activity and photoelectrochemical response under the UV illumination. It should be attributed to the effective electron–hole separation and the excellent electron transfer pathway along the 1D SnO₂ nanorod arrays and hematiete nanotube arrays.     

Highly enhanced photocatalytic degradation of dye rhodamine B on the biogenic hierarchical porous TiO<Subscript>2</Subscript>/SiO<Subscript>2</Subscript> with 1D/3D-chain

A hybrid photocatalyst consisting of TiO₂ and nonporous SiO₂ (TiO₂/CS-RH) is prepared by loading TiO₂ sol on one-dimensional/three-dimensional chain (1D/3D-chain) which is synthesized from rice husk. The products are characterized by X-ray diffraction, N₂-adsorption–desorption analysis and scanning electron microscopy. Meanwhile, the corresponding photocatalytic activity is evaluated by measuring the photocatalytic oxidation of rhodamine B (RhB). The results reveal that TiO₂/CS-RH displays a hierarchical porous structure from micrometer to nanometer scale with high BET surface area (574.7–719.4 cm²/g). Meanwhile, the activity of TiO₂/CS-RH for the photocatalytic degradation of RhB in aqueous slurry is significantly higher than that of the unsupported TiO₂. The optimal TiO₂ loaded on the support was two times and then treated at 600 °C for 120 min to complete the conversion of RhB. In contrast, the unsupported TiO₂ photocatalyst could convert only 20% of RhB in the same irradiation time and condition.     

Sonochemical synthesis, characterization, and photocatalytic properties of Bi2−x Sb x WO6 nanorods

We report an efficient route for the sonochemical synthesis of Bi_2?x Sb _x WO₆ (x = 0, 0.01, 0.02, 0.05, 0.1, and 2) nanorods using bismuth nitrate/antimony chloride and sodium tungstate as precursors. The products obtained have been characterized using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and UV–Vis diffuse reflectance spectroscopy. The photoactivities of all the samples for the Rhodamine-B (RhB) photodegradation were investigated systematically under UV and visible light irradiation. The results of the photocatalytic degradation of RhB in aqueous solution showed that 2–5 % antimony ion doping greatly improved the photocatalytic efficiency of sonochemically synthesized Bi₂WO₆ nanorods under both UV and visible radiation compared to its undoped counterpart. Among all the samples, the Sb₂WO₆ nanorods exhibited the highest photodegradation efficiency since 86 % of RhB could be photodegraded in 90 min under UV radiation. The stability of the photocatalysts was ascertained using FT-IR and Raman spectroscopy.     

Hydrothermal synthesis,characterisation and photocatalytic properties of BiOIO3 nanoplatelets

In this work, BiOIO₃ nanoplatelets were successfully prepared by a simple hydrothermal method. The as-prepared samples were characterised by energy-dispersive spectroscopy, scanning electron microscopy, high-resolution transmission electron microscopy, X-ray powder diffraction and ultraviolet visible diffuse reflectance spectroscopy. The photocatalytic activities of the as-prepared BiOIO₃ nanoplatelets were evaluated by photodegradation of rhodamine B (RhB) under simulated solar light. The results showed that the change of temperature within a certain range has almost no influence on the morphology and size of BiOIO₃ nanoplatelets. However, it had an obvious effect on the photocatalytic performance of BiOIO₃ nanoplatelets. The results showed that the BiOIO₃ sample synthesised at 130 °C exhibited the highest photocatalytic activities compared to others, with RhB completely decomposed in 80 min. The products with proper crystallinity formed at 130 °C have the optimal rate of RhB photodegradation. It indicated that the most favourable crystallinity made it beneficial to improve the photocatalytic activity. The possible mechanism of the photocatalytic reaction based on deep analysis and the experimental results was discussed in detail.     

Hydrothermal synthesis of hierarchical flower-like α-CNTs/SnO2 architectures with enhanced photocatalytic activity

The hierarchical flower-like α-CNTs/SnO₂ architectures composed of curved sheets are synthesized with hydrothermal method at 160?°C for 8?h. The α-CNTs/SnO₂ composite was doped with α-CNTs during preparation, the photocatalytic activity of α-CNTs/SnO₂ was evaluated by photodegradation of Rhodamine B (RhB) under simulated visible light. The results showed that the photocatalytic activity of α-CNTs/SnO₂ for degradation of RhB was up to 90.35% within 120?min, which was much higher than that of pure compound. It was significantly found that the introduction of α-CNTs, which may suppressed the recombination of photogenerated electron-hole pairs on the interface of SnO₂, leading to enhanced photocatalytic activity.     

Enhanced thermoelectric properties of WO3 by adding SnO2

Tungsten trioxide (WO₃) doped with stannic oxide (SnO₂) was prepared by a conventional mixed oxide processing route. The microstructure of the SnO₂-added WO₃ ceramics samples were investigated by X-ray diffraction and scanning electron microscopy. The grain size and porosity decreased with the increasing SnO₂ content. The sign of the Seebeck coefficient for all samples was negative over the entire temperature range, i.e., n-type conduction. The addition of SnO₂ to WO₃ led to an increase in both the electrical conductivity and the absolute value of the Seebeck coefficient. This indicates that the power factor was significantly enhanced by adding SnO₂ to WO₃. The thermoelectric power factor was maximized to 7.77 μW m^?1 K^?2 at 1,023 K for the 10.0 mol% sample.     

Synthesis of AgBr/TiO2/(I/S) composite and its enhanced photocatalytic performance to rhodamine B

Novel AgBr/TiO₂/(I/S) composite was synthesized by deposition–precipitation method. The AgBr/TiO₂/(I/S) composite was characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectra, UV–Vis diffuse reflectance spectra and the N₂ adsorption/desorption instrument. Under visible light irradiation, AgBr/TiO₂/(I/S) composite displayed much higher photocatalytic activity than that of pure I/S in the degradation of Rhodamine B (RhB). The RhB dye was degraded by 89% in less than 100 min. All results indicated that AgBr/TiO₂/(I/S) composite have good photocatalytic activity and chemical stability. Moreover, ·O₂^? is demonstrated to be the dominant radical for the photocatalytic degradation of RhB.

     

Vanadium doped SnO<Subscript>2</Subscript> nanoparticles for photocatalytic degradation of methylene blue

Nanometric V-doped particles with vanadium concentration varying from 0 to 10% were prepared using the polyol method. The influence of the doping on the textural, structural and optical properties was studied by various methods of characterization. X-ray diffraction (XRD) patterns disclose that nanocrystallites of cassiterite, i.e. rutile-like tetragonal structure SnO₂ and the absence of a new vanadium phase in the XRD pattern in the different concentration of doping were formed after annealing, the ordinary crystallite size decreased from 20.6 to 12.3 when the doping concentration increased from 0 to 10%, respectively. Moreover, the N₂ sorption porosimetry and transmission electron microscopic show that all samples synthesized were constituted of an aggregated network of almost spherical nanoparticles, which sizes changed with the altitude in the doping concentration to 10%. In accordance with UV–visible absorption measurements, this diminution of nanoparticles sizes was followed by a decrease in the band gap value from 3.25 eV, for undoped SnO₂, to 2.75 eV, for SnO₂ doped at 10%. On the other part, the photocatalytic activity of undoped and V-doped SnO₂ nanoparticles was studied using methylene blue (MB) as model organic pollutants. The SnO₂ nanoparticles doped at 10% of vanadium disclosed that the discoloration of MB reached 97.4% after irradiation of 120 min, with an apparent constant rate of the degradation reaching 0.035 min^?1 for MB degradation that was about 2.5 times more than that of pure SnO₂ (0.014 min^?1).     

Cr-induced modifications in the structural,photoluminescence and acetone-sensing behaviour of hydrothermally synthesised SnO2 nanoparticles

Cr-doped SnO₂ nanoparticles have been synthesised by the hydrothermal route, using SnCl₄·5H₂O as the host precursor and C₁₅H₂₁CrO₆ as the source of dopant. The structural and morphological studies have been carried out by X-ray diffraction, transmission electron microscopy and scanning electron spectroscopy, which reveal a tetragonal rutile structure of SnO₂ nanoparticles and improvement in the crystallinity upon Cr doping. Compositional analyses by energy-dispersive X-ray confirm the incorporation of Cr ions into the SnO₂ lattice. The existence of defect levels in the visible region has been studied by photoluminescence. The room-temperature electrical conductivity decreases with Cr doping due to the replacement of Sn⁴⁺ ions by Cr³⁺ ions. The response to acetone has been found to improve with the increase of Cr-doping concentration relative to the undoped SnO₂, except in the case of 0.5 at% Cr-doped sample where it decreases at low concentrations (up to 30 ppm) and operating temperatures (up to 200 °C). The response time decreases with the increasing Cr-doping concentration and is found to be minimum for the 1.5 at% Cr-doped SnO₂. A possible reaction mechanism of acetone sensing has been explained.     

Photocatalytic activities of Mo-doped Bi2WO6 three-dimensional hierarchical microspheres

The Mo-doped Bi₂WO₆ three-dimensional (3D) hierarchical microspheres from nanoplates have been synthesized by a hydrothermal route. The products were characterized in detail by multiform techniques: X-ray diffraction (XRD), energy-dispersive X-ray analysis (EDS), scanning electron microscopy (SEM), and UV-vis absorption spectrum. The results of the photocatalytic degradation of Rhodamine-B (RhB) in aqueous solution showed that molybdenum ions doping greatly improved the photocatalytic efficiency of Bi₂WO₆ 3D hierarchical microspheres. The Mo-doped Bi₂WO₆ microspheres with atomic ratio of Mo-W of 0.05 had the best activity in photodegradation of RhB in aqueous solution under 500 W Xe lamp light irradiation.     

Microwave Synthesis of Cu/Cu<Subscript>2</Subscript>O/SnO<Subscript>2</Subscript> Composite with Improved Photocatalytic Ability Using SnCl<Subscript>4</Subscript> as a Protector

Cu/Cu₂O/SnO₂ composites were successfully prepared with a facile microwave synthesis method. The structure of Cu/Cu₂O/SnO₂ composite was studied by morphology characterizations, such as X-ray diffraction, transmission electron microscopy and high-resolution transmission electron microscopy, which showed that the size of the Cu/Cu₂O/SnO₂ particles is 20–50 nm. The synthesis mechanism revealed that SnCl₄ obstructed between Cu(OH) and ethylene glycol, preventing Cu(OH) being reduced into Cu at high temperature. The photocatalytic property of Cu/Cu₂O/SnO₂ composite was investigated by degrading the mixed dyestuff under the irradiation of visible light at room temperature. Benefiting from the effect of electron transfer, the photocatalytic performance of the microwave-prepared Cu/Cu₂O/SnO₂ composite was much better than that of pure Cu₂O. The possible photocatalytic mechanism of the Cu/Cu₂O/SnO₂ composite catalysts was proposed and elaborated in this study. This synthesis of Cu/Cu₂O/SnO₂ composite may provide a method for other Cu₂O/semiconductor composites microwave preparation.     

Generation and photocatalytic activities of Bi@Bi2O3 microspheres

Composite Bi@Bi₂O₃ microspheres have been synthesized via a microwave-assisted solvothermal route. The Bi@Bi₂O₃ microspheres had a narrow size distribution in the range 1.2–2.8 mm. Glucose was selected as the reductant, BiCl₃ as the bismuth source, and ethylene glycol (EG) as the solvent in the synthesis system. The as-synthesized sample was characterized by X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), particle diameter distribution, energy dispersive X-ray spectroscopy (EDS), ultraviolet-visible (UV-vis) spectroscopy, and photoluminescence (PL) spectroscopy. The photocatalytic activities of the Bi@Bi₂O₃ microspheres were evaluated by the photodegradation of rhodamine B (RhB) and methyl orange (MO) dyes under UV light irradiation. The degradation reached ∼96.6% for RhB and 100% for MO after 4 h reaction in the presence of the as-synthesized Bi@Bi₂O₃ microspheres.     

Graphene oxide (GO)-doping SnO2 flower-like structure to enhance photocatalytic activity

The GO/SnO₂ micronanostructure was synthesized by a simple and effective hydrothermal method. The combined characterization methods such as Scanning Electron Microscope (SEM), Transmission electron microscope (TEM), X-ray diffraction (XRD), Element mapping, Energy Dispersive X-Ray Spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), the Raman spectroscopy, the Fourier transform infrared spectroscopy (FT-IR), Brunauer-Emmett-Teller (BET), photoluminescence (PL) the Ultraviolet–visible spectroscopy (UV-Vis) and Diffuse reflectance spectrum (DRS) indicated the successful formation of GO/SnO₂ micronanostructure. Moreover, the photocatalytic activity tested with RhB aqueous solution revealed that GO/SnO₂ had excellent photocatalytic properties compared with SnO₂. The photocatalytic efficiency of GO/SnO₂ was much higher (about 2.5 times) than that of pure SnO₂ under visible light irradiation. Based on these test results, we believe that the present work will provide some thoughts for further fabrication of other novel nanostructures and exploration of their applications.     

Synthesis of SnO2@SnS2 core–shell nanorods by double crucible method and their photocatalysis

SnO₂@SnS₂ core–shell structural nanorods were prepared by the solid phase double crucible method. The structure, morphology and optical properties of the as-prepared samples were characterized by X-ray diffraction, transmission electron microscope and ultraviolet–visible–near-infrared spectrophotometer. The results indicated that the mixture of hexagonal phases SnS₂ and tetragonal phase SnO₂ was formed at 400 and 500 °C and the molar ratio of SnO₂ to thioacetamide was 1:3. SnS₂ was uniformly coated on the surface of SnO₂ nanorods, and SnO₂@SnS₂ core–shell nanorods with the shell thickness of about 3–5 nm were obtained. Furthermore, their photocatalytic properties were tested for the degrading of methyl orange in water under visible light (λ > 420 nm) irradiation. Compared with pure SnS₂ nanomaterials, the core–shell nanorods demonstrated more superior photocatalytic activity. These meaningful results had laid certain foundation for further research on metal oxide@metal sulfide core–shell structure nanomaterials.     

Enhanced photocatalytic activity of Fe-doped ZnO nanoparticles synthesized via a two-step sol–gel method

A series of Zn_1–x Fe _x O (x = 0, 1, 2, 3, 4 %) powders via a two-step sol–gel method in open system were successfully fabricated. Influence of Fe doping concentration on the structure, morphology, optical properties and photo catalysis properties were investigated by means of X-ray diffraction, scanning electron microscopy, UV–Vis spectrophotometer and photochemical reaction instrument. The results showed that the ZnO powders were hexagonal wurtzite structures and their crystalline sizes and particle diameters decreased with the increase of Fe doping concentration. An increase of visible light absorption value and a decrease in band gap from 3.219 to 3.167 eV were found with the increase of Fe doping concentration, which enable the sample harvest more photons to excite the electron from the valence. Enhanced visible light induced photocatalytic activity has been found in Fe doped ZnO and the ultraviolet light induced photocatalytic properties of the Fe-doped ZnO have been improved greatly compared with undoped ZnO and commercially available TiO₂ (P25). The photocatalytic activities were not significantly affected by the particle size, and the best Fe doping concentration is 1 %.     

Synthesis and conductive performance of antimony-doped tin oxide-coated TiO2 by the co-precipitation method

The synthesis of Sb–SnO₂/TiO₂ (SST) composites by assembling antimony-doped tin oxide (Sb–SnO₂) nanoparticles on the surface of titanium dioxide (TiO₂) is systematically investigated. X-ray diffraction data show that the SST composite materials with good crystallinity can be indexed as anatase TiO₂ phase and cassiterite SnO₂ phase. The scanning electron microscopy and transmission electron microscopy indicate that Sb–SnO₂ particles with average diameter of 25 nm have been successfully coated on the surface of TiO₂. In addition, the Ti–O–Sn band can be detected on the surface of TiO₂ through Fourier translation infrared spectroscopy. The influences of pH, Sn/Ti mole ratio, hydrolysis temperature and calcination temperature on the electrical resistivity of the SST powders are studied. Under the optimum experimental conditions, the electrical resistivity of the composite conductive powders is 2.546 × 10³ Ω cm. Therefore, the SST composite conductive powders are useful as conductive fillers for the application in antistatic materials.     

SnO2/g-C3N4 photocatalyst with enhanced visible-light photocatalytic activity

Visible light-responsive SnO₂/g-C₃N₄ nanocomposite photocatalysts were prepared by ultrasonic-assisting deposition method with melamine as a g-C₃N₄ precursor. The as-prepared photocatalysts were characterized by X-ray diffraction, transmission electron microscopy, UV–vis diffuse reflectance spectroscopy, Fourier transform infrared spectra and photoluminescence emission spectra. The photocatalytic activities of the samples were evaluated by monitoring the degradation of methyl orange solution under visible light irradiation (wavelength ≥400 nm). The results show that the SnO₂ nanoparticles with the size of 2–3 nm are dispersed on the surface of g-C₃N₄ evenly in SnO₂/g-C₃N₄ nanocomposites. The visible-light photocatalytic activity of SnO₂/g-C₃N₄ nanocomposites is much higher than that of pure g-C₃N₄, and increases at first and then decreases with the increment of the content of g-C₃N₄ in the nanocomposites. The visible-light photocatalytic mechanism of the investigated nanocomposites has been discussed.     

In situ incorporation of well-dispersed Cu–Fe oxides in the mesochannels of AMS and their utilization as catalysts towards the Fenton-like degradation of methylene blue

Multi-components active metal oxide-supported catalysts are highly promising in heterogeneous catalysis due to some special promoting effects. In this study, by the controllable amount of Cu, Cu–Fe decorated anionic surfactant-templated mesoporous silica (Cu _x Fe/AMS) was directly prepared. The obtained catalysts were characterized by X-ray diffraction, N₂ adsorption–desorption, inductively coupling plasma emission spectroscopy, scanning electron microscopy, transmission electron microscopy, UV–visible, hydrogen temperature-programmed reduction, and X-ray photoelectron spectroscopy techniques. The results revealed that bimetallic Cu–Fe oxides were directly formed and highly dispersed in the mesochannels during the calcinations and the introduction of Cu²⁺ and Fe²⁺ on the micelles has influence on the structure properties. As compared to the monometallic Fe-modified AMS, the presence of Cu promotes the effects between Fe species and silica wall, leading to the better dispersion of Fe in the mesochannels of AMS. Finally, a series of Cu–Fe-modified AMS were used as Fenton-like catalysts and exhibited good catalytic activity in the degradation of methylene blue (MB), which resulted from high dispersion of Fe species and synergetic effect between Cu and Fe active sites. 1.0 was the optimum molar ratio of Cu²⁺ to Fe²⁺ ions to achieve the best catalytic activity and stability.     

Popcorn like morphology and absence of room temperature ferromagnetism in Ni doped SnO<Subscript>2</Subscript> nanoparticles

Ni-doped SnO₂ nanoparticles were synthesized by the microwave oven assisted solvothermal method. The structural characterization was done by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy. The outcomes confirmed that Ni-doped SnO₂ nanoparticles have a pure rutile-type tetragonal phase of SnO₂ structures with a high degree of crystallization and a crystallite size of 10–14 nm. Popcorn like SEM morphology of the nickel doped sample is shown. Optical characterization was done by UV–Vis spectrometer, fluorescence spectroscopy and electron paramagnetic resonance spectroscopy. Magnetic characterization was done by vibrating sample magnetometer (VSM). The VSM measurements revealed that the Ni doped SnO₂ powder samples were diamagnetic at room temperature. This diamagnetic result is in contradiction to earlier published results.