Synthesis of AgBr/ZnO nanocomposite with visible light-driven photocatalytic activity

AgBr/ZnO nanocomposite was synthesized via chemical precipitation from pure ZnO nanowires, AgNO₃, and NaBr. Inductively coupled plasma optical emission spectroscopy, X-ray diffraction, and high resolution transmission electron microscopy results confirmed the forming of AgBr/ZnO nanocomposite. High resolution transmission electron microscopy results of the as-synthesized AgBr/ZnO nanocomposite revealed that AgBr nanoparticles were attached to the surface of ZnO nanowires. UV-vis diffuse reflectance spectra of both pure ZnO and AgBr/ZnO nanocomposite displayed a band gap edge at about 350-380 nm. However, compared with pure ZnO, an additional broad tail from approximately 400 nm to 700 nm appeared in the UV-vis diffuse reflectance spectrum of AgBr/ZnO nanocomposite. The photocatalytic studies indicated that the as-synthesized AgBr/ZnO nanocomposite was a kind of promising photocatalyst in remediation of water polluted by some chemically stable azo dyes under visible light.     

Solvothermal synthesis of Cr-doped ZnO nanowires with visible light-driven photocatalytic activity

Cr-doped ZnO nanowires were fabricated by a solvothermal route from Zn(NO₃)₂6H₂O, Cr(NO₃)₃9H₂O and NaOH. Inductively coupled plasma optical emission spectroscopy, X-ray diffraction, transmission electron microscopy, and high resolution transmission electron microscopy results confirmed the doping of Cr into ZnO lattices. UV-vis absorption spectra of both pure ZnO and Cr-doped ZnO displayed a band gap absorption peak at about 365 nm. However, compared with pure ZnO, an additional broad tail from approximately 400 nm to 750 nm appeared in the UV-vis absorption spectrum of Cr-doped ZnO. The photocatalytic studies indicated that the as-synthesized Cr-doped ZnO nanowires were a kind of promising photocatalyst in remediation of water polluted by some chemically stable azo dyes under visible light.     

One-step in-situ hydrothermal synthesis of SnS2/reduced graphene oxide nanocomposites with high performance in visible light-driven photocatalytic reduction of aqueous Cr(VI)

Journal of Materials Science - Photocatalytic reduction of aqueous Cr(VI) was successfully achieved on SnS2/reduced graphene oxide (SnS2/RGO) nanocomposites. The SnS2/RGO nanocomposites have been...     

Microwave hydrothermal synthesis of AgInS2 with visible light photocatalytic activity

AgInS₂ nanoparticles with superior visible light photocatalytic activity were successfully synthesized by a microwave hydrothermal method. This method is a highly efficient and rapid route that involves no organic solvents, catalysts, or surfactants. The photocatalytic activity of AgInS₂ nanoparticles was investigated through the degradation of dyes under visible light irradiation. Compared with TiO_2−xN_x, AgInS₂ has exhibited a superior activity for photocatalytic degradation MO under the same condition. The experiment results showed that superoxide radicals (O₂⁻), hydrogen peroxides (H₂O₂) and holes (h⁺) were the mainly active species for the degradation of organic pollutants over AgInS₂. Through the determination of flat band potential, the energy band structure of the sample was obtained. A possible mechanism for the degradation of organic pollutant over AgInS₂ was proposed.     

Hydrothermal synthesis and photocatalytic activity of CdO2 nanocrystals

CdO(2) nanocrystals with different sizes were synthesized via the hydrothermal reaction of 3CdSO(4).8H(2)O and H(2)O(2) in 1.25-6.25 vol.% ammonia solutions at 100-140 degrees C for 12h. The resultant products were characterized by powder X-ray diffraction, transmission electron microscope, thermal gravimetric and differential scanning calorimetry, and UV-vis absorption spectra. It was concluded that the resultant products were pure cubic phase CdO(2) nanocrystals, and they would decompose at temperatures higher than 180 degrees C. In addition, degradation of methyl orange in aqueous solution (20.0mg/l) was carried out with the CdO(2) nanocrystals as photocatalyst under ultraviolet light irradiation. The experimental results showed that even a little amount (0.2g) of as-prepared CdO(2) nanocrystals could catalyze degradation of 500 ml methyl orange solution above 99% after 5h of illumination, and smaller size made for higher photocatalytic activity of CdO(2) nanocrystals.     

Enhanced visible light photocatalytic activity of Zn2SnO4 via sulfur anion-doping

Sulfur anion doped Zn₂SnO₄ was prepared by calcining the mixture of thiourea and spinel Zn₂SnO₄ at 300 °C under argon atmosphere and characterized by XRD, XPS and DRS. It was found that S^2? was incorporated interstitially into the bulk phase of Zn₂SnO₄. After the doping of S^2?, the band gap of Zn₂SnO₄ was sharply decreased to 2.7 eV compared with that of undoped Zn₂SnO₄ (~ 3.6 eV). The photocatalytic activity of S-doped Zn₂SnO₄ was enhanced for photodegradation of Rhodamine B (RhB) in aqueous solution under visible light irradiation.     

Hydrothermal synthesis and photocatalytic activity of anatase TiO2 nanofiber

TiO2 nanofiber consisting of 15 +/- 5 nm anatase grains was synthesized by hydrothermal treatment of fibrous hydrogen titanate precursor at 180 degrees C for 20 h. The hydrogen titanate precursor was synthesized by hydrothermal treatment of commercial P25 TiO2 powder in 10 M NaOH at 200 degrees C for 20 h followed by soaking in 0.1 M HNO3 to perform ion exchange between the as-synthesized Na titanate and H. By controlling pH of the solution during hydrothermal treatment of the hydrogen titanate precursor, pure anatase TiO2 nanofiber was obtained. Its band-gap energy determined from the onset of diffused reflectance spectrum was 3.19 eV which is equal to that of anatase TiO2 powder. The TiO2 nanofiber showed higher photodecomposition efficiency than the Cotiox KA-100 TiO2 but lower than the P25 TiO2. Photodegradation is the predominant process for 'Reactive blue 171' removal.     

Hydrothermal synthesis of hemisphere-like F-doped anatase TiO<Subscript>2</Subscript> with visible light photocatalytic activity

Hemisphere-like F-doped anatase TiO₂ has been synthesized by hydrothermal treatment of TiF₄ aqueous solution in the presence of starch at 130 °C for 10 h, and then calcined at 450 °C for 2.5 h in air. The as-synthesized product has been investigated by photocatalytic reaction test and characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray (EDX) spectroscopy, X-ray photoelectron spectroscopy (XPS), and UV–Vis diffuse reflectance spectra (DRS). The results showed that fluorine was successfully doped into the TiO₂ hemispheres. The F-doped TiO₂ hemispheres showed high visible light activity in degradation of acid orange II, which could be attributed to the creation of oxygen vacancies and good crystallinity.     

Hydrothermal synthesis of SnO2 hollow microspheres

SnO₂ hollow microspheres have been synthesized by a hydrothermal method. X-ray powder diffraction (XRD) and field-emission scanning electron microscopy (FE-SEM) were used to characterize such hollow microspheres. SEM image shows that SnO₂ microspheres with diameters of 0.5–1 μm are composed of SnO₂ nanoparticles with about 15 nm in diameter. Some broken microspheres indicate the hollow spherical structure. XRD shows that SnO₂ hollow microspheres have tetragonal structure.     

Hydrothermal synthesis and characterization of novel aloe-like SnS2 nanostructures

Novel aloe-like tin bisulfide (SnS₂) nanostructures were successfully synthesized via a thioglycolic acid (TGA) assisted hydrothermal process. X-ray powder diffraction (XRD), transmission electron microscopy (TEM) and field emission scanning electron microscopy (FESEM) were used to characterize the product. XRD pattern reveals that the product is well-crystallized SnS₂ with hexagonal structure. TEM and FESEM images clearly show an aloe-like nanostructure that is made from several single crystalline leaves. Furthermore, the possible growth mechanism is discussed.     

Bismuth oxychloride hollow microspheres with high visible light photocatalytic activity

Hollow microspheres of two bismuth oxychlorides, BiOCl and Bi₂₄O₃₁Cl₁₀, were successfully synthesized using carbonaceous microsphere sacrificial templates. The phase evolution from BiOCl to Bi₂₄O₃₁Cl₁₀ was easily realized by heating the former at 600 °C. With a uniform diameter of about 200 nm, an average shell thickness of 40 nm, and basic nanosheets of <20 nm, the hollow microspheres of both BiOCl and Bi₂₄O₃₁Cl₁₀ showed high visible light photocatalytic activity towards the degradation of Rhodamine B (RhB). Besides the effective photosensitization process and efficient photointroduced carrier separation, the high photocatalytic activity was believed to result from their hollow-structure-dependent large visible light absorption. Moreover, as a chlorine-deficient analogue, the Bi₂₄O₃₁Cl₁₀ hollow spheres possessed a narrower band gap, more dispersive band structure, and higher photocarrier conversion efficiency, which further helped them to exhibit better photocatalytic activity.

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Quasi-cube ZnFe2O4 nanocrystals: Hydrothermal synthesis and photocatalytic activity with TiO2 (Degussa P25) as nanocomposite

The fabrication and photocatalytic application of zinc ferrite nanocrystals were reported. Quasi-cube ZnFe₂O₄ nanocrystals with typical small sizes of 5-15 nm were successfully synthesized by a facile hydrothermal approach. ZnFe₂O₄/P25 nanocomposite was prepared by physically grinding the ZnFe₂O₄ nanocrystals with TiO₂ (commercial Degussa P25) at ambient temperature, and it exhibited excellent photocatalytic activity for the mineralization of Rhodamine B. UV-vis measurement and photocatalytic test results showed that ZnFe₂O₄ nanocrystals exhibited effective band-gap coupling to P25 nanopowders by simply physical grinding without any surface modification or high-energy balling, which is usually adopted in conventional mixture process. This phenomenon can be attributed to the high surface activities of the as-obtained tiny ZnFe₂O₄ nanocrystals and commercial P25 nanoparticles. It may imply that the mixing process of composite materials would be simplified by further lowering the grain sizes of their component particles.     

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.     

Synthesis and characterization of Ag/TiO2-B nanosquares with high photocatalytic activity under visible light irradiation

Square-like B doped TiO₂ nanocrystals were first synthesized by a mild solvothermal method with H₃BO₄ and titanium isopropoxide as the precursors, and isopropyl alcohol as reaction medium. Then, Ag nanoparticles were deposited on TiO₂-B nanosquares by photo-deposition. The as-synthesized products have been investigated by photocatalytic reaction test and characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and UV–vis diffuse reflectance spectra (DRS). The results showed that boron was successfully doped into TiO₂ nanosquares under solvothermal condition. The obtained Ag/TiO₂-B composite showed high efficiency in degradation of acid orange II under visible light irradiation. The high photocatalytic performance could be attributed to the synergistic effect of B doping and the plasmon photocatalysis role of the deposited silver nanoparticles over TiO₂.     

Enhancement of visible light activity in Ag modified SnO2/TiO2

Ag modified SnO₂/TiO₂ nanoparticles were successfully prepared by a modified sol–gel method, without adding any acid or alkali. The entire preparation differs from the traditional sol–gel synthesis of TiO₂ that the reaction can get controlled by adjusting the flow speed of water vapor. Ultraviolet–visible diffuse reflectance spectra (UV–vis) and spin-trapping electron paramagnetic resonance (EPR) were used to forecast the photocatalytic activity of the samples, and the results were proved by the degradation of methylene blue solution under visible light. Compared with pure TiO₂, as-prepared Ag modified SnO₂/TiO₂ nanoparticles exhibited not only an enhanced photocatalytic activity but also an improved stability. Among all of samples, the composite with 0.5% of Ag and 1% of Sn showed the best photocatalytic performance and stability. Further increasing the Ag proportion will result in the decrease of the photocatalytic activity. A relative mechanism was proposed and discussed in detail.     

Mn-doped TiO2 nanopowders with remarkable visible light photocatalytic activity

TiO₂ nanocrystalline powders with various Mn-doping levels were synthesized by the sol-gel process using tetrabutyl titanate and manganese nitrate as precursors. The crystal structure, morphology, doping concentration, optical absorption property, and elemental state of the obtained samples were analyzed. TEM results showed that the synthesized TiO₂ powders were anatase nanoparticles about 7 nm in size. EDX and XPS analyses proved the incorporation of Mn ions into the TiO₂ lattice. A remarkable red shift of the absorption edge was achievable by increased Mn content, leading to gigantically narrowed energy gap to permit absorption well into the infrared spectral region. The dramatic optical absorbance of the doped TiO₂ nanopowders in the visible spectral region led to strong photocatalytic activity under visible light illumination, which was observed by measuring the degradation of methylene blue. In contrast, little degradation was observed for the pure TiO₂ powder. The optimum Mn/Ti ratio was observed to be 0.2 at.% for photocatalytic applications.     

Enhanced visible light photocatalytic activity of CeO2/alumina nanocomposite: Synthesized via facile mixing-calcination method for dye degradation

In this present study, an effort has been made to novel CeO₂/alumina nanocomposite photocatalyst was fabricated through mixing-calcination method. The XRD, IR, SEM, TEM, EDX and XPS results designated that these synthesized materials are formed effectively. The photocatalytic results for the degradation of dye solution indicate that the most dynamic ratio is CeO₂:Al₂O₃ (2.5:1) under visible light irradiation. The photocatalytic degradation was made under dark and in the presence of light to establish the photocatalytic efficiency of the synthesized photocatalyst. The improved performance of CeO₂/alumina nanocomposite is attributed to the separation efficiency of photo-induced charge carriers and it inhibit charge recombination. The major active species are determined by radical scavengers trapping experiments were revealed that superoxide radical (O₂^?) and hydroxyl radical (OH) are playing a vital role in the degradation of dye solution. The stability of catalyst was confirmed by consecutive runs of CeO₂/alumina nanocomposite.