A Simple Approach to Fabricate CdS-SiO_2 Hybrid Microspheres by Producing CdS Nanoparticles on the Surface of Thiolated SiO_2 Microspheres

We have developed a simple synthetic method to prepare the hybrid microspheres of CdS nanoparticles on the surface of silica microspheres modified by（3-mercaptopropyl） trimethoxysilane（MPS）. The--SH groups of MPS can bind with the Cd^2＋ ions on the surface of SiO2. When thioacetamide releases H2S, the nanosized CdS particles（ 1-6 nm） will successfully be generated on the silica surface under the experimental conditions. The size of the CdS nanoparticles was found to be related to the concentration of Cd^2 ＋ feed and the size of silica spheres, the higher the concentration of Cd^2＋ and the larger of silica microspheres, the bigger the size of CdS nanoparticles. Techniques including UV, PL, TEM and XPS were used to characterize the CdS-SiO2 hybrid microspheres.

PREPARATION OF SILICA/POLY(METHACRYLIC ACID)/POLY(DIVINYLBENZENE-CO-METHACRYLIC ACID) TRI-LAYER MICROSPHERES AND THE CORRESPONDING HOLLOW POLYMER MICROSPHERES WITH MOVABLE SILICA CORE

Hollow poly（divinylbenzene-co-methacrylic acid） （P（DVB-co-MAA）） microspheres were prepared by the selective dissolution of the non-crosslinked poly（methacrylic acid） （PMAA） mid-layer in ethanol from the corresponding silica/PMAA/P（DVB-co-MAA） tri-layer hybrid microspheres, which were afforded by a three-stage reaction. Silica/PMAA core-shell hybrid microspheres were prepared by the second-stage distillation polymerization of methacrylic acid （MAA） via the capture of the oligomers and monomers with the aid of the vinyl groups on the surface of 3-（methacryloxy）propyl trimethoxysilane （MPS）-modified silica core, which was prepared by the Stober hydrolysis as the first stage reaction. The tri-layer hybrid microspheres were synthesized by the third-stage distillation precipitation copolymerization of functional MAA monomer and divinylbenzene （DVB） crosslinker in presence of silica/PMAA particles as seeds, in which the efficient hydrogen-bonding interaction between the carboxylic acid groups played as a driving force for the construction of monodisperse hybrid microspheres with tri-layer structure. The morphology and the structure of silica core, silica/PMAA core-shell particles, the tri-layer hybrid microspheres and the corresponding hollow polymer microspheres with movable silica cores were characterized by transmission electron microscopy （TEM）, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy （XPS）.

SYNTHESIS OF CdS/SiO_2/POLYMER TRI-LAYER FLUORESCENT NANOSPHERES WITH FUNCTIONAL POLYMER SHELLS

Tri-layer CdS/SiOz/polymer hybrid nanospheres were synthesized by distillation precipitation polymerization of either ethyleneglycol dimethacrylate （EGDMA） or EGDMA together with comortomers havirLg different functional groups, such as methacrylic acid, 4-vinylpyridine and 2-hydroxyethylmethacrylate, in the presence of 3-（methacryloxy）propyl trimethoxysilane （MPS）-modified CdS/SiO2 nanoparticles as seeds in acetonitrile with 2,2＇-azobisisobutyronitrile （AIBN） as initiator. In this approach, MPS-modified inorganic seeds were prepared by the modification of CdS/SiO2 nanoparticles via the self-condensation reaction between the hydroxyl groups of sinaols, in which the CdS/SiO2 nanoparticles were afforded by a reverse microemulsion technique for the synthesis of CdS core nanoparticles with the subsequent coating of silica layer. The polymer shell-layers encapsulated over the MPS-modified CdS/SiO2 inorganic seeds via the efficient capture of the monomers and oligomers from the solution with the aid of the vinyl groups incorporated by the MPS modification, in which the polymer shell-thickness and functional groups including carboxyl, pyridyl and hydroxyl, were facilely controlled by the feed of EGDMA as well as the types of comonomers used for the polymerization. These nanospheres were characterized by transmission electron microscopy （TEM）, Fourier-transform infrared spectroscopy （FT-IR）, thermogravimetric analysis （TGA）, fluorescence spectroscopy and zeta potential.