Highly luminescent SiO 2 beads with multiple QDs: Preparation conditions and size distributions

Abstract

Multiple CdTe quantum dots (QDs) were incorporated in SiO 2 beads using a reverse micelle route (i.e., a water-in-oil emulsion) and a precursor solution of SiO 2-coated CdTe QDs as the water phase. The QDs in the beads retained their initial photoluminescence efficiency (56%) because they had a thin SiO 2 shell that prevented removal of the ligands from their surface during incorporation. Because of the SiO 2 sol in the precursor solution, the size of the water pools in water-in-oil emulsion increased to 700 ± 320 nm compared to 25 ± 5 nm when an aqueous CdTe QD solution was used. The size of the beads prepared in the water pools depended strongly on the preparation parameters (water phase injection speed, tetraethyl orthosilicate concentration, reaction time). The beads were easily separated into three size ranges (60 ± 23, 160 ± 40, and 650 ± 200 nm) by filtering for further application.