Research On The Preparation And Properties Of CdSe Nanocrystals And P3HT/CdSe Nanocomposites

CdSe nanocrystals belong to II~VI direct band gap semiconductornanomaterials and they have a wide application prospect in many fields withtheir special physical and chemical properties. Since a lot of properties ofsemiconductor nanomaterials are closely related to their morphology andstructure, numerous scientific researchers in material field have committed tothe study on shape control, surface modification, synthesis method of CdSenanomaterials in recent years, and there are plenty of achievements on theaspects of light, electricity, magneticand so on, which constantly promotes theresearch and development of CdSe nanomaterials and their composite. The mainresearch work of this paper can be divided into the following two aspects:1) Study on the synthesis and properties of CdSe nanocrystals. In this paper,CdSe nanocrystals were prepared by two kinds of methods, which aretemplate-free hydrothermal synthesis and polymer template route. In the processof template-free hydrothermal synthesis of CdSe nanocrystals, cadmiumchloride, sodium selenite, ammonia were used as raw material, the reaction timewas modified for2h,5h,10h, then dendritic, rodlike and transitional (fromdendritic to rodlike) tufted hexagonal phase CdSe nanocrystals were respectivelyprepared. By investigating the formation mechanism and the structuralproperties of the obtained products, the resulting morphology and structure ofCdSe nanocrystals are mainly subject to the crystal form of crystal nuclei,surface energy effects of crystals and the growing environment of crystals. Inthe polymer template route, cadmium acetate and selenium powder were used asthe raw material, polyethylene glycol (PEG) as the polymer template, glycolbenzene aether as solvent, the as-prepared products were characterized by XRD,UV-Vis, TEM. The results show that the structure, morphology and opticalproperties of these CdSe nanocrystals are heavily influenced by the Cd:Se molarratio, but relatively less affected by the amount of PEG.2) Study on the synthesis and properties of P3HT/CdSe nanocomposites.P3HT/CdSe nanocomposites were prepared directly, by using cadmium oxide ascadmium source, selenium powder as selenium source, liquid paraffin and oleicacid (LP-OA) as solvents, P3HT as a conjugated polymer template in the reaction system. The effects of the Cd:Se molar ratio, reaction temperature andthe amount of P3HT on the morphology and optical properties of P3HT/CdSenanocomposites were investigated. The results show that with a Cd:Se molar ratioof1:2, well-distributed spherical P3HT/CdSe nanocomposites, which possessthe best fluorescence quenching effect, can be obtained at260℃.2:1to4:1isthe appropriate Cd:Se molar ratio for the synthesis of the tetrapod-shapedCdSe/P3HT nanocomposites. In the process of the synthesis of theseCdSe/P3HT nanocomposites, P3HT and oleic acid molecules act as the guidetemplate and the surfactant respectively, affecting and conditioning themorphology and structure of CdSe nanocrystals. The optical properties of thesolutions, which were formed by mix CdSe/P3HT nanocomposites with differentanions in proportions, were characterized. It was found that the anions,especially OH-, enhanced the fluorescence intensity of CdSe/P3HTnanocomposites in different degrees, and the fluorescence intensity ofCdSe/P3HT nanocomposites increased with decreasing amplitude as theconcentrations of the anions increased.