Anomalous Photoluminescence in Silica-Coated Semiconductor Nanocrystals After Heat Treatment

An anomalous photoluminescent (PL) behavior observed in silica-coated semiconductor nanocrystals (NCs) after heat treatment was investigated. The NCs were silica-coated at room temperature using the sol-gel reaction of tetraethylorthosilicate (TEOS) in alkaline conditions through a Stöber method. During preparation, the Cd2+ to TGA ratio were adjusted to ensure that the target properties were obtained. The absorption and PL spectra were measured using conventional spectrometers. The PL efficiencies of the samples in solution were estimated by comparison with those of quinine sulfate. Investigation of the absorption spectra of small CdSe NCs as a function of the mutual distance of the NCs has shown that as the distance becomes smaller, the absorption spectrum shifts to red with a featureless structure. It was also observed that due to the glass network formed during reflux, the diffusion of the ions in the glass beads was minimal at room temperature.