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Abstract: PbS and Bi2S3 nanocrystals with well-controlled sizes and shapes were easily produced from molecular precursors (xanthate) in ethylene diamine (en) solution at room temperature. When lead or bismuth ethylxanthate were added into en solution, the precipitates were instantly formed, and subsequently, PbS cubes and flower-like Bi2S3 hierarchical structures were obtained if the mixtures were left still for 5days under ambient conditions. This work not only provides a facile route to synthesize chalcogenides with well-defined nano- and microstructures in a solution-phase system, but also gives insight into understanding on decomposition behavior of molecular precursors in various solvents. [Copyright &y& Elsevier]

Presents a letter to the editor about NMR assignments.

In the present study, bismuth tungstate (Bi2WO6) nanocrystals were prepared by the hydrothermal method using bismuth nitrate (Bi(NO3)3 x 5H2O) and sodium tungstate (Na2WO4 x 2H2O) as raw materials at 150 degrees C for 24 h. The powder X-ray diffraction (XRD) pattern shows that the Bi2WO6 nanocrystals belong to the orthorhombic phase with calculated lattice constants a = 5.457 angstroms, b = 16.435 angstroms and c = 5.438 angstroms. The X-ray photoelectron spectra (XPS) indicate that the obtained Bi2WO6 was pure. The photocatalytic activity of the nanocrystal prepared by using water, N, N-dimethyl formamide (DMF) and ethylene glycol (EG) as the solvent respectively were studied for the degradation of rhodamine B under visible light irradiation. The results show that Bi2WO6 sample obtained in EG has the best photocatalytic activity mainly owing to good dispersion, small particle size and broader spectrum response for visible light. In addition, the influence of pH and surfactant on the Bi2WO6 photocatalytic activity was also studied. The results show that Bi2WO6 sample has better photocatalytic activity when prepared at 150 degrees C and pH 1.0 with sodium dodecylsulfate (SDS) as the surfactant. The photoluminescence (PL) spectra of the prepared Bi2WO6 reveal that the recombination of photo-generated electrons and holes was inhibited over Bi2WO6 prepared with SDS and thus its photocatalytic ability was enhanced.

Ceria (CeO2) nanoparticles were prepared by precipitation method using cerium nitrate (Ce(NO3)3 x 6H2O) and ammonia (25 Wt%) as raw materials under the reaction for 3 h and ageing for 9 h at 80 degrees C without any surfactants and further calcination. The powder X-ray diffraction (XRD) pattern shows the as-prepared CeO2 crystals belong to the cubic phase and are well crystallized. Transmission electron microscopic (TEM) studies reveal that the appearance of as-prepared CeO2 is hexagonal, which is proposed to be the projection of polyhedral shape. The regular fringes spacing of 0.31 nm is in agreement with the d value of (111) lattice planes of cubic phase CeO2 from high-magnification TEM image. Reaction conditions such as the concentration of precipitant, reaction temperature and ageing duration exert important influence on the purity and morphology of the product. Ce(OH)3 was detected when the reaction was processed at lower pH (< 9) or with ageing duration less than 8 h at 80 degrees C. The size of polyhedral ceria nanoparticles increased with longer ageing time (> 15 h). If the reaction went on at a temperature lower than 40 degrees C, a large quantity of rodlike Ce(OH)3 was produced according to TEM observation. Raman spectra of CeO2 nanocrystallines exhibit a Raman shift at 465 cm(-1), corresponding to a F2g Raman band from the space group Fm3m of a cubic fluorite structure, while the Raman shift at about 600 cm(-1) may be attributed to the second Raman vibration mode of O2- vacancy due to Ce3+ impurity. Photoluminescence spectrum of CeO2 shows an emission at 465 nm at room temperature, which may be explained by charge transition from the 4f band to the valence band of CeO2.

In the present study, bismuth sulfide (Bi2S3) nanoribbons were prepared by the hydrothermal method using bismuth nitrate (Bi(NO3)3 x 5H2O), thioacetamide (C2H5NS) and nitrilotriacetic acid (C6H9NO6) as raw materials at 180 degrees C for 12 h. The reaction time was largely reduced and the route has been unreported. The constituent, structure and morphology of the products were characterized by XRD, XPS and TEM, respectively. The powder X-ray diffraction (XRD) pattern shows that the Bi2S3 crystals belong to the orthorhombic phase (JCPDS:17-320) with calculated lattice constants a = 1.1106 nm, b = 1.0993 nm and c = 0.3892 nm, which are consistent with the reported values (a = 1.1149 nm, b = 1.1304 nm and c = 0.3981 nm). Transmission electron microscopic (TEM) studies reveal that the appearance of as-prepared Bi2S3 is nanoribbon-like with the typical width of about 100 nm; and the high-resolution transmission electron microscope (HRTEM) image shows that the crystal grows along the y axis. The quantification of X-ray photoelectron spectra (XPS) analysis peaks gives an atomic ratio of 2 : 3 for Bi : S, which is consistent with the given formula of Bi2S3. Furthermore, the Raman and UV-Vis spectra of the product were also studied. Compared with bulk Bi2S3 (236 cm(-1)), the Raman absorption band of the Bi2S3 nanoribbons (195 cm(-1)) red-shifts 41 cm(-1), which is because of the surface effect of nanomaterials. Furthermore, the product has absorption at the wavelength of about 450 nm in the UV-Vis region. The direct bang gap energy (Eg) was estimated to be about 1.58 eV(Eg of the bulk Bi2S3 is 1.3 eV), which indicates that the product has potential application in the optical and electrical areas.