Size Quantized Semiconductors in Porous Hosts—Quantum Dots

Summary

The construction of discreet clusters of semiconductors inside the pore structure of zeolite hosts has generated a new class of materials where confinement effects on the semiconductor optical properties are pronounced. In addition to the size-quantization effects, novel intercluster phenomena become manifest as the individual semiconductor clusters reach a volume density above the percolation limit and begin to interact three-dimensionally. This interaction is modulated by the zeolite framework topology and hence leads to an ordered array of quantum dots in what we have termed superclusters. Novel absorption, emission and excitation behaviors of these materials, dominated by defect sites, result. Detailed characterization of the semiconductor species responsible (by X-ray powder diffraction and EXAFS) reveal a cubane-like (CdS)4 unit as the basic building block of the structure.