Excited Semiconductor Clusters: Magic Source

Abstract

In this paper, we review the preparation and properties of CdS-like clusters as well as their important applications in several nanostructures. The clusters created by the reaction of S2− ions generated by the decomposition of thioglycolic acid (TGA) and Cd2+ ions play important roles for the construction of novel nanocrystals (NCs), the assembly of the NCs, and the formation of nanostructures including 1D solid and tubal fibers, 2D dendritic morphology, and 3D crystals. The formation and property of the clusters depended strongly on the molar ratio of TGA and Cd2+ ions in solutions. When aqueous CdTe NCs coated with a hybrid SiO2 shell containing the clusters, they revealed a drastic increase in photoluminescence (PL) efficiency (from 28 to 80 %) and temperature-dependent PL. These excellent PL properties were ascribed to the clusters very closed to CdTe cores. This is confirmed through the observation of a lengthening of the Auger recombination lifetime by a factor of ~3.5 in the presence of the clusters. The size of the clusters determined the PL properties of the hybrid SiO2-coated NCs and those fibers. Because of their high PL, these biofunctional materials could provide a platform for various applications.