Linear and nonlinear optical spectroscopy of CdS nanoparticles in Nafion membranes

CdS nanoparticles embedded in Nafion membranes were studied by a variety of optical spectroscopic methods. Quantum confinement was achieved (particle mean diameter of 40 A) and the growth was found to follow a linear temporal kinetic law. Discrete energy levels were observable, even at room temperature. They could be attributed to light hole and heavy hole IS and 2S transitions. The experimental results are in good agreement with theoretical calculations of light hole and heavy hole masses in the cases of cubic CdS. An enhancement of the nonlinear susceptibility chi(3) at the quantized exciton energy levels was observed. The clusters were found to be photo-unstable, with a diffusion-limited growth rate due to Ostwald ripening.