Self-assembly Film Of Functionlized Carbon Microspheres

Photonic crystals are artificially arranged 3-D periodic structures of new materials. Because their structures exhibit photonic band gap, they are of promising applications in fast and large capacity and highly integrated photonic devices. In this paper, carbon microspheres (CMSs) were used as the building blocks, which were firstly oxidized by the surface chemical modification, and then organized into carbon films by self-assembly with excellent thermal stability, mechanical stability and optical properties. The carbon films may be used as photonic crystals and for potential development and application prospects in optoelectronic device fields.First, CMSs were synthesized by chemical vapor deposition method (CVD). Subsequently, the surface chemical modification of CMSs was carried out by chitosan (CS), SiO2 and ZnO to give CS/CMSs, SiO2/CMSs and ZnO/CMSs composites. The fluorescence properties of CS/CMSs and SiO2/CMSs composites were investigated and their composites were self-assembled by vertical deposition. The effects of deposition temperature and suspension concentration on the quality of self-assembling film were investigated. Morphologies and structures of the samples were characterized by field emission scanning electron microscopy, atomic force microscopy, X-ray diffraction, thermogravimetry and Fourier transformation infrared spectrometry. The results are as follows:1. CMSs were firstly oxidized by a mixture of concentrated HNO3 and H2O2, and CS was coated to the surface of CMSs by electrostatic interaction between CMSs with negative charge and CS with positive charge, thus giving CS/CMSs composites. When the mass ratio of CMSs to CS was 1:2, the surface of CMSs was uniformly covered with CS, giving improved dispersion in water and ethanol; As-synthesized CMSs and SiO2 were compounded to form SiO2/CMSs composites by sol-gel method with surfactant hexadecyl trimethyl ammonium bromide (CTAB) as a bridge linking. The uniform SiO2/CMSs composites with good mono-dispersion were prepared with 0.5g of CMSs,2 mL of TEOS,30 mL of ammonia and 12 h of reaction time; CMSs were covered with ZnO by the hydrolysis of zinc acetate under the presence of triethanolamine. The obtained ZnO/CMSs composites with uniform size had smooth surface and strong interaction between ZnO and CMSs when the molar ratio of zinc acetate to triethanolamine was 1:2 and the reaction time was 2 h; As-synthesized CMSs, oxidized CMSs, CS/CMSs and SiO2/CMSs with different suspension concentrations emitted different fluorescence in organic solvent (ethanol and tetrachloromethane) and water. With increasing concentration, the fluorescence color gradually deepened and finally resulted in fluorescence quenching at too high concentration.2. CS/CMSs and SiO2/CMSs were self-assembled by vertical deposition. The film thickened with increasing suspension concentration at fixed temperature, and more dense film was obtained at 10 mg/mL of suspension concentration and 50℃; SiO2/CMSs composite films had higher degree of order and density than CS/CMSs composite films prepared under the same conditions. This study lays an experimental basis for the formation of carbon-based photonic crystals.