Encapsulation of CdSe/ZnS nanocrystals within mesoporous silica spheres

Quantum dots (QDs) have attracted much attention on account of their unique optical and electronic properties. Applications of QDs in biological systems face challenges owing to their toxicity and hydrophobicity. Incorporation of QDs in mesoporous silica spheres affords not only hydrophilic shell for QDs in order to enhance their dispersion in aqueous medium, but also offers chemically inert shielding to reduce QD cytotoxicity. In the current work, two types of mesoporous silica encapsulated QDs were synthesized by rationally adjusting the reaction conditions. Mesoporous silica coated single CdSe/ZnS nanoparticles (sCdSe/ZnS@mSiO₂) were prepared through the one-pot reaction. Further modification of this reaction offered hollow mesoporous silica spheres (CdSe/ZnS@HMSS) encapsulating multiple CdSe/ZnS QDs assembled on the internal surface of the spheres. Both of sCdSe/ZnS@mSiO₂ and CdSe/ZnS@HMSS show significant photophysical properties. Possible formation mechanism of the two types of nanostructures was investigated and discussed.