Controllable Synthesis And Characterization Of Micron And Nanoscale Bismuth Oxybromides And Metal Selenides And Tellurides

The aim of this dissenation is to explore the synthesis of BiOBr, Bi₂O₃,PbSe,and CoTe₂ nanomaterials by hydrothermal method, room temperature chemical solution route and mixed-solvothemal technique. BiOBr microflowers and Bi₂O₃ shuttles with concave surfaces have been synthesized through a hydrothermal method; Based on the previous work, BiOBr sub-microflowers with the diameter of 500 nm have been prepared at room temperature. Well-crystalline PbSe cuboidal structures with different concave faces in each plane have been prepared through a solvothermal process using diethylenetriamine (DETA) and distilled water as mixed solvent. Flower-like CoTe₂ nanostructures have been synthesized on a large scale using triethylenetetramine (TETA),N2H4·H2O and distilled water as mixed solvent with adding hexadecyl trimethyl ammonium bromide (CTAB). The main contents can be summarized as follows:1. Through controlling the amount of NaOH added, BiOBr and Bi₂O₃ with different shapes were hydrothermally synthesized in the reaction system of Bi(NO₃)₃–hexadecyl trimethyl ammonium bromide (CTAB)–NaOH. In acid condition, BiOBr microflowers constructed of nanoflakes were synthesized. The thickness of these single-crystal nanoflakes was about twenty nanometers. In more basic condition, Bi₂O₃ shuttles with concave surfaces were obtained. The length of these shuttles was 100μm and the diameter at the middle of these shuttles was 50μm. The photocatalytic activity of as-prepared BiOBr microflowers was evaluated by the degradation of methyl orange (MO) under visible-light irradiation (λ> 420 nm), which was up to 96% within 90 min. Based on the previous work, flower-like BiOBr sub-microstructures about 500 nm in diameter have been synthesized in the presence of Bi(NO₃)₃ and tetraethylammonium bromide (TEAB) by a solution route at room temperature. These sub-microflowers are composed of nanoflakes with the thickness of 20 nm. The photocatalytic activities of flower-like BiOBr were evaluated by the degradation of methyl orange (MO) and phenol under visible-light and UV-light irradiation, with the efficiencies up to 97% within 1.5 h and 45% within 4 h, respectively.2. A facile mixed-solvothermal method for the preparation of the cuboidal structures with different concave faces in each plane has been established using Na₂SeO₃ as selenium source. The FESEM showed that the edge lengths of these cuboidal crystals ranged from 1.5 to 2.5μm, and the edges of a cube crystal extend outwards from its core with a tiny cubic center leaving step-like faces. DETA acts both as the reducer and the solvent.3. Well-crystallined flower-like CoTe₂ nanostructures have been synthesized on a large scale by a triethylenetetramine (TETA) and hexadecyl trimethyl ammonium bromide (CTAB) synergistic-assisted solvothermal route. The TEM results showed that the product was flower-like nanostructures composed of packed nanorods with an average diameter of 50 nm. The influence factors of synthesizing flower-like CoTe₂ nanostructures such as the volume ratio of mixed solvent and the amount of CTAB were discussed, which indicated that both TETA and CTAB played crucial roles in controlling phase composition and morphology of the resultant products.