Preparation Of Several Nano-system Characterization And Biological Applications

Nanomaterials. which are different from their corresponding hulk materials.have the novel optic, electric and magnetic properties. In this dissertation, the chemical synthesis, physical characterization and biological applications of some nanoscale semiconductor materials have been systematically studied. The main research results are shown as followed:Using the organic solvent method, nearly mono-dispersed CdS nanocrystals were obtained in liquid paraffin. The CdS nanocrystals in tetrahedron shape capped with the hydrophobic surfactants in nanometer scale can be assembled to a close-packed monolayered structure. The CdS nanocrystals with different sizes have been prepared by changing the reaction conditions such as the concentrations of cadmium precursor and sulfur precursor, the initial ratio of Cd:S precursors and the pH value of reaction system. The UV-visible absorption and photoluminescence spectra show the quantum confinement effect clearly. The time-resolved photoluminescence spectra have also been examined.In this article, mono-dispersed hexagonal structure CdSe nanocrystals with polyhedron shape were prepared by an open solvent thermal reaction. They show a discrete excitonic transition structure in the absorption spectra and the minimal PL peak full-width at half-maximum (FWHM) of 19 nm. The PL quantum yield (QY) is about 60%. Transmission electron micrographs (TEM). high-resolution transmission electron micrographs (HRTEM), X-ray powder diffraction (XRD) patterns, UV-vis absorption spectra and photoluminescence (PL) spectra were obtained for the as-prepared CdSe nanocrystals. The size of the CdSe nanocrystals can be tuned by changing the reaction temperature or time. Due to the improved synthesis method, a different growth mechanism of the CdSe nanocrystals is discussed. The mechanism of...