Silanization of quantum dots: Challenges and perspectives

Abstract

Here we report the facile strategies for synthesis of silica-coated quantum dots (QDs). Due to their small size, chemical and optical stability and high luminescence quantum yield these particles can be further applicable in chemical and biomedical analysis, and in vivo imaging. The article gives a structured and detailed overview of the silanization strategies and potential pitfalls and common technical issues in function of the stability of the obtaining QDs. Different types of QDs, In- and Cd-based, were compared in terms of their behaviour during the silica-encapsulation. To achieve that each silica nanoparticle contains only one single QD the silanization reaction was performed via a water-in-oil emulsion formation. We investigated a number of parameters which have an impact on the silica-coating process and on characteristics of the obtained nanoparticles, such as a nature of initial ligands on the QD surface, a silanization reagent, surfactant, ZnS shelling, etc. It was found that DDT is an optimal ligand for the silanization of InP-based quantum dots, but not for CdZnSeS-nanocomposites. GOPTES and CEST are the best silanization agents for covering InP-QDs, and the AOT/isooctane microemulsion is preferable for the silanization of CdZnSeS-composites.