Study On The Preparation And Photocatalytic Properties Of Cadmium Sulfide Of Controllable Morphology

Cadmium sulfide(CdS) is one of the most significant Ⅱ-Ⅵsemiconductors and with a typical wide band gap of2.42eV at roomtemperature and excellent physioehemieal properties such as photoelectricconversion characteristics and luminescence property. At the same time, with thedecreasing of the size and shape change, the band gap of CdS nanostructuresproduces a significant change, causing them to show excellent photoelectricproperties that different from the massive material, and its photocatalyticperformance have vary widely changed. So, many attempts have been made tosynthesize CdS nanocrystals especially for the control of their shape, size, anddisperse, in order to get materials with different photoelectric properties.(1) The high-purity wurtzite CdS microspheres with smooth surface and thecauliflower-like CdS microspheres have been successfully synthesized through asimple template-free approach employing a hydrothermal process usingcadmium chloride as cadmium source, sodium thiosulfate as sulfur source. Theinfluences of precursor concentration, reaction time and also reactiontemperature on the morphologies, the size and the photocatalytic properties ofCdS products was analyzed. The results showed that these conditions havemainly influenced on the crystallinity, the morphology and photocatalyticperformance of CdS products. Therefore, the focus of this study is to identify thebest experimental conditions of the preparation of samples with excellentphotocatalytic performance.(2) By controlling the mole ratio of precursor, reaction time andtemperature, the netted sphere-like CdS microspheres with excellentphotocatalytic performance were prepared in ethylenediamine using cadmiumnitrate tetrahydrate and L-cysteine as precursors by a solvothermal process. Andthe UV absorption edges of the obtained samples showed an obvious red shiftcompared to block CdS materials, and absorption peak intensity was obviouslyincreased. The results showed that the ethylenediamine has an important influence on the formation of netted CdS microspheres and the improvement ofphotocatalytic performance.(3) By adjusting the molar ratio of precursor cadmium nitrate tetrahydrateand thioglycolic acid(TGA), reaction temperature and reaction time, three kindsof CdS samples with obvious different morphologies were successfullysynthesized in ethylenediamine or deionized water by a solvothermal process.The possible formation mechanism of this three kinds of morphologies ispresented, and the photocatalytic performance of the CdS nanostructures wereinvestigated. The effect of different parameters such as the molar ratio TGA toCd2+, temperature, reaction time, which are known as the key parameter on themorphology and particle size of products were investigated.(4) Well-defined hierarchical CdS dendrites in a pure hexagonal phase weresynthesized by hydrothermal treatment of the initial cadmium chloride andthiourea. The results illuminated that, in our system, thiourea was an excellentreactant as a sulfur source and a ligand to provide an appropriate condition forthe dendritic CdS crystal growth, and that can also modulate the morphology ofCdS dendrites by confining the growth of certain facets.