In the presence of Fe3O4 nano-particles, a new type of super-paramagnetic Fe3O4/Au microspheres with core/shell structures was prepared by reduction of Au3+ with hydroxylamine. The formation mechanism of the core/shel...In the presence of Fe3O4 nano-particles, a new type of super-paramagnetic Fe3O4/Au microspheres with core/shell structures was prepared by reduction of Au3+ with hydroxylamine. The formation mechanism of the core/shell microspheres was studied in some detail. It was shown that the formation of the complex microspheres can be divided into two periods, that is, surface reaction-controlled process and diffusion-controlled process. The relative time lasted by either process depends upon the amount of Fe3O4 added and the initial concentration of Au3+. XPS analysis revealed that along with increasing in coating amount, the strength of the characteristic peaks of Au increased, and the Auger peaks of Fe weakened and even disappeared. Size distribution analysis showed that the core/shell microspheres are of an average diameter of 180 nm, a little bit larger than those before coating.展开更多
基金Acknowledgements This work was supported by the National Natural Science Foundation of China (Grant No. 29973024), University Key Teacher Plan and the State Key Laboratory Visiting Scholar Foundation of the Ministry of Education of China.
文摘In the presence of Fe3O4 nano-particles, a new type of super-paramagnetic Fe3O4/Au microspheres with core/shell structures was prepared by reduction of Au3+ with hydroxylamine. The formation mechanism of the core/shell microspheres was studied in some detail. It was shown that the formation of the complex microspheres can be divided into two periods, that is, surface reaction-controlled process and diffusion-controlled process. The relative time lasted by either process depends upon the amount of Fe3O4 added and the initial concentration of Au3+. XPS analysis revealed that along with increasing in coating amount, the strength of the characteristic peaks of Au increased, and the Auger peaks of Fe weakened and even disappeared. Size distribution analysis showed that the core/shell microspheres are of an average diameter of 180 nm, a little bit larger than those before coating.
