Direct Hybridization of Hydrophobic Nanocrystals with Colloidal Silica via van der Waals Force.

We present a novel, direct approach to hybridize hydrophobic quantum dot (QD) nanocrystals with colloidal silica (A) via van der Waals (vdW) force only. The A is constructed by aggregation of 15-25 nm sized hydrophobic silica nanoparticles with octadecyl groups. For hybridization, the hydrophobic QDs sit on the crevices of A via reinforced vdW force by interdigitation of long-chained hydrocarbons along the enlarged contact area of the crevices. The hybrids (B) are easily encapsulated with silica with/without functional groups, yielding QD-layer-incorporated silica particles (C) with greatly enhanced PL (up to 690%) and astonishing photostability compared with their free QDs under an identical QD concentration. This approach is simple, novel, versatile, and extended to the cases of three different sized QDs. The hydrophobic product C with phenylethyl groups is applicable to fabricate a white LED, and its hydrophilic analogues can be a promising material for bioapplications.