Double-layer silica core-shell nanospheres with superparamagnetic and fluorescent functionalities

Superparamagnetic nanocrystals and QDs have attracted much attention due to their great potential in biomedical applications. In this Letter, the interest arises from the possibility of positioning magnetic and optical particles at different layers in a silica core-shell structure. In this double layered core-shell structure, QDs are sandwiched between the core and shell silica layers, whereas Fe(3)O(4) nanoparticles are entrapped in the core. This structure was designed with the idea of preventing direct contact between QDs and Fe(3)O(4) nanoparticles, thus minimizing the 'quenching effect' and achieving high quality magnetic. uorescent dual functionality. The obtained double-layer silica nanospheres are promising candidates for applications in simultaneous biolabeling, imaging, cell sorting and separation. (C) 2008 Elsevier B.V. All rights reserved.