Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành hóa học dành cho các bạn yêu hóa học tham khảo đề tài: Research Preparation and Characterization of Silica-Coated Magnetic–Fluorescent Bifunctional Microspheres | Nanoscale Res Lett 2009 4 1078-1084 DOI s11671-009-9356-0 NANO EXPRESS Preparation and Characterization of Silica-Coated Magnetic-Fluorescent Bifunctional Microspheres Qi Xiao Chong Xiao Received 11 December 2008 Accepted 24 May 2009 Published online 20 June 2009 to the authors 2009 Abstract Bifunctional magnetic-fluorescent composite nanoparticles MPQDs with Fe3O4 MPs and Mn ZnS ZnS core-shell quantum dots QDs encapsulated in silica spheres were synthesized through reverse microemulsion method and characterized by X-ray powder diffraction scanning electron microscopy transmission electron microscopy vibration sample magnetometer and photoluminescence PL spectra. Our strategy could offer the following features 1 the formation of Mn ZnS ZnS core shell QDs resulted in enhancement of the PL intensity with respect to that of bare Mn ZnS nanocrystals due to the effective elimination of the surface defects 2 the magnetic nanoparticles were coated with silica in order to reduce any detrimental effects on the QD PL by the magnetic cores and 3 both Fe3O4 MPs and Mn ZnS ZnS core-shell QDs were encapsulated in silica spheres and the obtained MPQDs became water soluble. The experimental conditions for the silica coating on the surface of Fe3O4 nanoparticles such as the ratio of water to surfactant R the amount of ammonia and the amount of tetraethoxysilane on the photoluminescence properties of MPQDs were studied. It was found that the silica coating on the surface of Fe3O4 could effectively suppress the interaction between the Fe3O4 and the QDs under the most optimal parameters and the emission intensity of MPQDs showed a maximum. The bifunctional MPQDs prepared under the most optimal parameters have a typical diameter of 35 nm and a saturation magnetization of emu g at room temperature and exhibit strong photoluminescence intensity. Q. Xiao H C. Xiao School of Resources Processing and Bioengineering Central South University 410083 Changsha China e-mail .