Synthesis of 1,4-Bis(o-cyanostyryl)benzene-Silica Nanoparticles with Core-Shell Structures and Effects of Reaction Conditions

Core-shell nanoparticles with 1,4-bis(o-cyanostyryl)benzene (CSB), which is a commonly used fluorescent agent, as the core and with nanosilica particles as the shell were prepared by a self-templating method. The morphologies, structure, particle size distribution, and optical properties of the resulting CSB-SiO 2 nanoparticles were characterized. The effects of the reaction conditions on the structure and morphologies, their stability in aqueous solutions, and their optical properties were investigated. During the process, an oil-in-water emulsion system was formed, and the core-shell nanoparticles were obtained by a rapid solidification reaction from the outer surface toward the center of the emulsion. The whole process required neither surface treatment for nanosilica particles nor additional surfactant or stabilizer. Experimental results indicated that the resulting CSB-SiO 2 nanoparticles were perfectly spherical with smooth particle surfaces and had distinct core-shell structures. The CSB-S7O 2 nanopaticles had good stability in aqueous solutions for a period of time. The particle size and shell thickness could be readily tuned by altering reaction conditions. The resulting CSB-SiO 2 core-shell nanoparticles exhibited strong UV absorption and fluorescence emission. In addition, the mechanism of the self-templating method for forming core-shell nanoparticles is discussed.