Metal Dithiocarbamates As Precursors For Preparation Of Semiconductor Sulfide Nanocrystals

Semiconductor nanocrystals have attracted broad attentions from researchers invarious disciplines due to their size-dependent optical, electronic, magnetic, andchemical properties that can’t be obtained in their bulk counterparts. Among thevarious nanocrystals, metal sulfide nanocrystals have been widely investigated formany applications including biological labeling and diagnostics, light-emitting diodes,photovoltaic devices, and electroluminescent devices. Thus, developing facile andgeneral synthetic approaches that yield sulfide metal with precise control over notonly the chemical composition but also the size and shape is highly desirable fromfundamental studies to practical applications. In this thesis, chemical leaching withdithiocarbamate-based generalized direction preparation of metal chalcogenidenanocrystals, including Ag2S, Cu9S5, In2S3, AgInS2, CuInS2and janus Ag-Ag2S havebeen developed. The contents of this thesis are as follows：1. we have reported a general and facile strategy for preparing metal sulfidenanocrystals based on thermolysis of metal dithiocarbamate salts, which was in situformated from chemical leaching. The chemical leaching was an oxygen-dependentprocess and cholofom greatly faciliated the dissolving rates. Furthermore, a series ofmetal suldides nanocrystals were successfully prepared through this stratage. Basedon this, uniform spherical Ag2S nanocrystals with particle sizes of2.8，8.1，11.8nm,21.5nm and cubic Ag2S nanocrystals with34.5nm were synthesized. Binary In2S3,and Cu9S5nanocrystals with70nm were obtained. Further, ternary AgInS2andCuInS2were prepared from a reaction mixture of Ag or Cu, In and dithiocarbamatewith their own stoichiometric molar ratio. Those obtained nanocrystals werecharacterized by UV-Vis、TEM(HRTEM)、EDS and XRD. By this method, the size,shape, and chemical composition of the nanomaterials can be easily controlled, andthese as-synthesized metal sulfides exhibit novel optical properties. This facilemethodology for synthesis of metal sulfides may be generally expanded to fabricateother nanocrystals and the readily available metal elements may provide an alternativeapproach for synthesis of nanomaterials.2. A controllable synthetic approach to janus Ag-Ag2S nanoparticles wasproposed by adjusting the ratio of surfactants. Octadecylamine and oleic acid (1:1inmolar) as surfactants, through thermolysis of silver dithiocarbamate precursor, janusAg-Ag2S nanoparticles can be obtained. The obtained nanocrystals were characterized by TEM(HRTEM), EDS, XRD and spectrum. The effect of surfactants on formingJanus Ag-Ag2S nanoparticles was investigated. It was found that the ratio ofsurfactants played a great role for formation of Janus nanoparticles. When the contentof octadecylamine decreased, only Ag2S nanoparticles could be obtained. The resultsshowed that it can be achieved by adjusting the ratio of surfactants to controlmorphology of the nanoparticles.