Coating Aqueous Quantum Dots with Silica via Reverse Microemulsion Method:  Toward Size-Controllable and Robust Fluorescent Nanoparticles

Fluorescent core−shell CdTe@SiO₂ particles with controllable particle sizes were prepared via a reverse microemulsion method by hydrolyzing tetraethyl orthosilicate within microwater droplets. Aqueous CdTe nanocrystals and CdS nanocrystals stabilized by different types of thiol molecules were prepared for elucidating the mechanism leading to the core−shell structures. Photo-oxidation experiments were performed to show the enhancement effect of the silica shell on the photostability of the CdTe nanocrystals encapsulated. Further surface modifications were also performed for grafting amino groups on the surface of the resultant fluorescent CdTe@SiO₂ particles.