Facile Preparation of Bifunctional Monodisperse Nanospheres with Tunable Size and Luminescence.

Nanotechnology has found wide use in biomedical applications and the food and bioprocessing industry. In this light, we demonstrate a facile strategy to prepare bifunctional monodisperse silica nanospheres encapsulating chitosan-coated magnetic nanoparticles and CdTe quantum dots. The size of these composite spheres can be adjusted from 90 nm to 500 nm by varying the concentration of ammonia, water, tetraethyl orthosilicate, and the ratio of the chitosan-coated magnetic nanoparticles and CdTe quantum dots. The composite spheres are characterized using scanning electron microscope analyses, transmission electron microscope analyses, energy-dispersed spectrum studies, Malvern Zetasizer, vibrating sample magnetometer, and fluorescence microscopy. The spheres exhibit good monodispersion and favorable superparamagnetic and fluorescent properties. The luminescence of the spheres can be varied by using different types of coated quantum dots. Such composite spheres with tunable characteristics allow for external manipulation of research systems by magnetic fields together with the real-time fluorescent monitoring of multiple samples. The abovementioned properties can potentially be exploited for application in the biomedical and biosensing fields.