Study On The Preparation Of Photoluminescent Semiconductor Materials-SiO₂ Composite Colloidal Particles

Due to outstanding photo-electronic properties, photoluminescent semiconductor materials have shown great prospect in photonluminance, sensor, luminescence and biological imaging. It is necessary to fabricate semiconductor-inert materials because of stability and consistency of semiconductor materials reacting with organism. Base on this idea, we try to prepare CdTe semiconductor-silica composites and have prepared CdTe-SiO₂ doped composite microspheres, core-shell composite nanoparticles and films. First, based on prepared high quality CdTe nanocrystals aqueous, we havesynthesized monodisperse, doped CdTe-SiO₂ composite microspheres by a facile and prevalent method. Without any modifying or altering, the CdTe nanocrystals can be incorporated into SiO₂ matrix by sol-gel method in St?ber system. This method changing the idea that the nanocrystals have to be modified by silane ligands with thio or amido group before introducing into silica, moreover, the method has simplified the process. The composite microspheres can be controlled from 200 nm to 1.4μm in diameter. We have prepared four kinds of CdTe nanocrystals with different stabilizers and it is found that MPA molecular is the best stabilizers for synthesizing CdTe-SiO₂composites. Because of the protecting of silica matrix, the nanocrystals in composite microspheres are more stable to surroundings changing than the CdTe in solution. The mechanism of reaction has also been invested and more kinds of composites are expected to be synthesized with this method. The CdTe-SiO₂ composite microspheres can be used as building block to prepare photonic crystals in future.In order to prepare CdTe-silica composite nanoparticles, the nanocrystals have been coated with a thin silica film by grafting silane ligands with epoxy, at the same time, the nanocrystals bave been dissolved in ethanol. The CdTe-silica composite nanoparticles can be modified with functional group by grafting silane ligands in ethanol. The functional CdTe-silica nanoprticles will show more effect in biological imaging, et al.In order to prepare monodisperse CdTe/SiO₂ nanocomposite spheres. a water in oil microemulsion was used. Furthermore, We have tried to coat CdTe nanocrystal and Fe₃O₄ magnetic nanoparticles with SiO₂ simultaneously to form dual-functional nanocomposites. As a result, the CdTe NCs and Fe₃O₄ MPs can be introduced into SiO₂ microspheres and the nanocomposites show a narrow size distribution (40nm-200nm). The properties of nanocomposites were adjusted by controlling the concentration of NH4OH, H2O and the mass fraction of functional nanoparticles. The fluorescent and magnetic properties of functional nanoparticles were kept down well and nanocomposites revealed better stability.