Highly luminescent SiO2 beads with multiple QDs: Preparation conditions and size distributions

Multiple CdTe quantum dots (QDs) were incorporated in SiO2 beads using a reverse micelle route (i.e., a water-in-oil emulsion) and a precursor solution of SiO2-coated CdTe QDs as the water phase. The QDs in the beads retained their initial photoluminescence efficiency (56%) because they had a thin SiO2 shell that prevented removal of the ligands from their surface during incorporation. Because of the SiO2 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.

Graphical abstractHighly luminescent SiO2 beads with incorporated QDs were obtained, exhibiting a broad size distribution.Figure optionsDownload full-size imageDownload high-quality image (64 K)Download as PowerPoint slideResearch highlights► Multiple QDs were encapsulated in SiO2 beads by a reverse micelle route. ► The QDs retained their initial photoluminescence efficiency in the SiO2 beads. ► The beads displayed a broad size distribution because of a silica sol in water phase. ► Filtering was used to select different bead sizes from the broad distribution.