Ruixing Li

Facile solvothermal synthesis of BiOCl–TiO2 heterostructures with enhanced photocatalytic activity

BiOCl–TiO2 heterostructures with different Bi to Ti molar ratios were synthesized via a facile one-pot solvothermal process. The as-synthesized BiOCl–TiO2 heterostructures included TiO2 nanoparticles deposited on the surface of BiOCl nanoplates. X-ray photoelectron spectroscopy results revealed the TiO2 of BiOCl–TiO2 heterostructures doped with Bi3+, reduced the band gap energy of the sample. The photocatalytic efficiencies were evaluated by degradation of methylene blue dye under simulated sunlight illumination. Results indicated that the BiOCl–TiO2 heterostructures with Bi : Ti = 1 : 3 exhibited the highest photocatalytic efficiency, which is 73.5 times and 8.5 times higher than that of single phase BiOCl and TiO2, respectively. In addition, the radical species involved in the degradation process have been investigated by scavenger experiments. Finally, a new mechanism for the photocatalytic action of the BiOCl–TiO2 heterostructures was put forward.

Template-free synthesis of mesoporous CeO2 powders by integrating bottom-up and top-down routes for acid orange 7 adsorption

A combined bottom-up and top-down route was developed for the template-free synthesis of mesoporous CeO2 powders using Ce(NO3)3·6H2O, NH4HCO3, H2O2, and H2O as starting reagents. The flake-like Ce2(CO3)3·8H2O precursor was etched by H2O2, and CeO2 nucleated in situ with built-in equiaxed particles. Pores formed on the flakes owing to the loss of by-products of H2O and CO2. The formation of the mesostructured CeO2 could also be explained by the large change in volume induced as a result of the difference in density between Ce2(CO3)3·8H2O and CeO2. Accordingly, the original flake-like morphology of Ce2(CO3)3·8H2O was not preserved upon pore formation and during continuous stirring in the synthesis. A subsequent hydrothermal treatment destroyed the loose aggregates of CeO2 derived from the reaction between H2O2 and Ce2(CO3)3·8H2O. Rearrangement of the CeO2 particles via a dissolution–recrystallization process occurred under certain temperatures and pressures. Consequently, CeO2 particles with coarser sizes, smoother surfaces, and mesoporous structures were obtained. The specific surface area of the particles was 166.5 m2 g−1 after hydrothermal treatment at 200 °C for 24 h. The mesoporous CeO2 particles possessed better adsorption capacities of acid orange 7 dye than basic orange 2 dye in the absence of pH pre-adjustments. The saturated adsorption amount of acid orange 7 dye was 510.2 mg g−1 at 298 K based on Langmuir linear fitting of the experimental data.

Dependence of infrared absorption properties on the Mo doping contents in MxWO3 with various alkali metals

A series of molybdenum-doped tungsten bronzes with various alkali metals were synthesized by a solvothermal process using ethanol and acetic acid as solvents. All the X-ray diffraction (XRD) peaks for the samples could be indexed as the corresponding types of hexagonal tungsten bronzes with the general formula, MxWO3, where M denotes an alkali metal. Targeted research on cesium tungsten bronze indicates that the actual atomic ratio of Cs to W (x) could be influenced by the introduction of molybdenum, which has a critical effect on the infrared absorption properties. Optical tests show that molybdenum-doping is an effective process, with respect to enhancing the absorption of infrared and the conversion efficiency of light energy to heat energy, for tungsten bronzes with various alkali metals. The optimum starting Mo/W (mol) ratios for obtaining high infrared absorption properties were 0.01 for sodium and potassium tungsten bronzes and 0.03 for rubidium and cesium tungsten bronzes. Among the samples, doped cesium tungsten bronze has the strongest properties.

Solvothermal synthesis of nano-CeO 2 and degradation of dye in indoor lighting

Azo dyes are an abundant class of synthetic, organic compounds containing one or more azo bonds (-N=N-). A large amount of these dyes are produced for using in different applications. However, their complex structure makes them difficult to biologically degrade. We sought to degrade acid orange 7 (AO7) using nitrogen-doped (N-doped) and carbon-nitrogen (C-N) co-doped nano-CeO 2 . N-doped monocrystalline CeO 2 nanoparticles was synthesised by solvothermal method using triethanolamine as a nitrogen source at 120°C for 24 h. C-N co-doped monocrystalline CeO 2 nanoparticles were synthesised by solvothermal method using hexamethylenetetramine as both nitrogen and carbon source at 140°C for 24 h. For purposes of comparison, a sample of undoped CeO 2 was synthesised using the dopant of neither triethanolamine nor hexamethylenetetramine. The doped and undoped CeO 2 monocrystals were all less than 10 nm in diameter. Nitrogen and carbon-nitrogen were shown to be incorporated into CeO 2 lattice from the results of both XRD and X-ray photoelectron spectroscopy analyses. The degradation of AO7 in water was investigated using a domestic 10 W compact fluorescent lamp. The results showed the degradation ratios of AO7 in the presence of nano-CeO 2 in the sequence of: C-N co-doped CeO 2 ≯ N-doped CeO 2 ≯≯ undoped CeO 2 , corresponding to magnitudes of 98.8%, 97.6%, and 48.2%, respectively.

Synthesis and infrared shielding properties of molybdenum-containing ammonium tungsten bronzes

A series of molybdenum-containing ammonium tungsten bronzes was synthesized by a solvothermal process at 200 °C for 72 h using ethylene glycol, acetic acid, ammonium tungstate and ammonium molybdate as starting materials. All the diffraction peaks of XRD for the samples synthesized with starting Mo/W (mol) = 0–0.2 could be rough indexed as a hexagonal ammonium tungsten bronze with the formula of (NH4)0.33WO3, which was accompanied by a shift of the main peaks after the introduction of molybdenum and a split peak for starting Mo/W (mol) = 0.1. The nitrogen content, based on both the thermogravimetry and X-ray photoelectron spectroscopy, rose with the increase of molybdenum content. Optical properties were evaluated using Fourier transform infrared spectroscopy, which proved that the molybdenum-containing ammonium tungsten bronzes could shield infrared rays better than the sample without molybdenum. The shield efficiency was related to the content of molybdenum. The optimum starting Mo/W (mol) to obtain high infrared shielding properties was 0.1. This sample consisted of uniform rods of ca. 50 nm in diameter emerging from the agglomerates.

SYNTHESIS AND CRYSTALLIZATION OF NANO-CERIA PARTICLES BY SOLVOTHERMAL ROUTES

Cerium oxides (CeO2) were synthesized by two steps solvothermal routes. First, a precursor was precipitated using solutions of cerium (III) nitrate and ammonia, and then this precursor was treated via solvothermal techniques in an autoclave. Narrow distribution of CeO2 particle size, between 10 to 15 nm, was achieved in different solvents. Hard agglomerates of nano-CeO2 were mitigated in an ethanol solvent. Most of crystal particles were in the shape of a quadrangle for the precursor. Morphology of CeO2 particles gradually changed after the precursor was treated by solvothermal techniques. There were both quadrangular and symmetrically hexagonal particles at an alkaline pH value. Alternatively, the quadrangular particles disappeared, instead of geometrically unsymmetrical hexagon with decreasing pH to a more acid value. The evolution mechanism of the morphology was discussed. These results have important implications for recognizing and controlling the crystalline shape by solvothermal techniques.

Facile synthesis of superparamagnetic Fe3O4 nanoparticles just using ferric citrate and water

ABSTRACT Fe3O4 nanoparticles were synthesized by a facile one-pot hydrothermal process just using ferric citrate and water without any additional reagent and post-treatment. The temperature of hydrothermal reaction had important influence on the crystallinity and magnetic property of Fe3O4 samples. Fe3O4 sample synthesized at 200 °C for 24 h showed a narrow size distribution (4 to 8 nm in diameter), and exhibited apparent superparamagnetism with saturated magnetization of 55.1 emu/g. The narrow size distribution and superparamagnetism were the interesting features of these Fe3O4 nanoparticles.