Synthesis And Characterization Of CdSe Nanocrystals Under Mild Conditions

In this paper, on the basis of summarizing the synthesis methods and applications of the semiconductor nanomaterials, we have selected mild condition to synthesize the CdSe by using amine stabilizer. The very small CdSe nanocrystals(NCs) have been synthesized at room temperature, followed by low-temperature (80°C) chemical etching process in a solution of 3-amino-1-propanol(APOL)and APOL/H2O (v/v = 10/1) mixture. We have got the CdSe nanorods using solvothermal method, and have researched the structure characterization and optical properties of products through various characterization means.The very small CdSe nanocrystals(NCs) have been synthesized using EDA and EDTA as stabilizer in ethanol or distilled water at room temperature. The result of XRD shows the products were mainly zinc-blende structural phase. The CdSe NCs synthesized at room temperature have UV-vis absorption and no PL emission by ultraviolet-visible (UV-vis) absorption spectra and photoluminescence (PL) emission spectra. After etching, the CdSe NCs not only show strong band-edge photoluminescence but also have a gradual increase in the PL emission spectra with the increasing of etching time. This might be an indication of surface reconstruction and removal of surface irregularities and disorder when etching is arrested. By comparing the intensity of photoluminescence, H2O in the etching solution slows down the etching process.The arrayed CdSe nanorods have been obtained using thiourea as a surface modifier and using EDA as a solvent through first solvothermal process, then post-hydrothermal method. As the strong complexing action between thiourea and Cd2+, thiourea can effective reduce the growth of CdSe nanorods by participating in the competition reaction with Se2-. The result of photoluminescence(PL) emission spectra showed PL maxima blue shift with the molar ratios of thiourea and Cd(NO3)2 increasing, which reflects the quantum size effect. Evidently, the results revealed that thiourea is an effective surface-modified reagent for CdSe.In addition, we have synthesized CdSe with different morphologies and phases by adjusting the composition of solvent through solvothermal method. The result of XRD and TEM revealed that the amount of EDA in the reaction systems not only determine the structure of the product, but also affect the morphology of the product. With an increased concentration of EDA in the reaction system, the structural phase of the product gradually transform from zinc-blende to wurtzite, in the meantime, the morphologies transformation of products was observed, first fasciculate nanorods, then branch nanorods, and finally separate nanorods.