Controlled Preparation Of Colloidal Cu₂S Nanocrystals In Organic Phase

In recent years, colloidal nanocrystals have attracted more and more attention of researchers because of its structure, size and special optical properties. CuxS nanocrystals are a very important semiconductor material. When X changes from 1 to 2, the energy band changes from 1.2eV to 1.8eV, this particular property has been widely used in making solar cells. Because of their quantum size effects, good shape and dimensions of the Cu2S crystals can enhance the performance of the photoelectric effect. Recent research has focused on using the new synthesizing method to study the morphology, size, and arrangement of Cu2S nanocrystals and also its optical properties. In this thesis, we used the traditional colloidal chemical synthesis method to prepare semiconductor nanocrystals in the organic phase, and studied its structure. Results are summarized as follows:1. Cu2S nanocrystals were synthesized in the organic system of TOPO/TOP by using CuO and S as precursor. And then were characterized by X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) in order to analyze crystal structure, shape, size, and composition. Results indicated that the ratio of CuO and S can had influence on the shape, size and composition of Cu2S nanocrystals. When the mass ratio of CuO and S was 2:1, the nanocrystals were without the regular shape. And when the ratio was up to 1:1, the synthesized Cu2S were good dispersed and the nanocrystals were changed to nanosphere. The size of nanocrystals increased and had a better dispersion while the ratio was up to 1:2. This indicated that the increase of S could help the nanocrystals to form the core.2. In this experiment oleic acid was used as dispersant and copper acetate and n-dodecanethiol were used as reactants. In the oil phase we used the "one pot" method to synthesis Cu2S spherical nanocrystals and also used XRD, XPS, and TEM to characterize final products. And then we studied the influence on the shape, size and composition of Cu2S nanocrystals when change the different reaction temperatures, reactant ratio and reaction time. Results indicated that the synthesized nanocrystals wereβ-Cu2S with monodispersity. The size of Cu2S nanocrystals can be controlled effectively by controlling the reaction time. The size increased when the reaction time extends. In the situation that the volume of n-dodecanethiol remain the same, the size of nanocrystals decreased by increasing the amount of substance of Cu(CH3COO)2. The shape of the Cu2S can easily change from nanosphere to nanoplate just by changing reaction temperature. Because the experimental approach was simple, raw materials can easily be obtained, and the shape and size of nanocrystals can be under effectively control, it is expected to apply this method to prepare other metal sulfide nanomaterials.