Amine-capped silicon quantum dots

Water-soluble photoluminescent (PL) silicon quantum dots (SiQDs) can be obtained by surface modification with small organic molecules, while still leaving some sites uncovered by the employed organic molecules due to steric repulsion. Using a density-functional tight-binding method, we show the possibility of fully capping surface of SiQDs by amine, which is more effective in protecting the surface against oxidation. The presence of amine not only reduces the optical gaps but also results in a significant enhancement of absorbance and fluorescence. Moreover, the amine-capped SiQDs are expected to be water soluble and PL stable, and thus could be used as biological sensors.