Studies of the Formation and Growth of Q-State Cadmium Selenide Particles in Cadmium Arachidate Langmuir-Blodgett Films

Abstract

The formation and growth of Q-state CdSe particles during exposure of Langmuir-Blodgett films of cadmium arachidate (CdAr) to hydrogen selenide has been studied using UV-visible absorption, grazing angle FTIR, X-ray photoelectron spectroscopy (XPS), and quartz crystal microbalance (QCM) measurements. UV-visible absorbance measurements showed an optical blue shift typical of particles between 1.1 and 1.3 nm in radius. In addition to the formation of Q-state CdSe particles, elemental selenium (formed by the decomposition of H 2 Se) was present in the films. Grazing angle FTIR and XPS measurements (after subtraction of the contributions due to elemental selenium) were consistent with Q-state particle formation involving quantitative conversion of the Cd 2+ ions in the films to CdSe and the corresponding conversion of CdAr to arachidic acid. Changes in the orientation of the surfactant molecules were also found to be a consequence of particle growth in the films. QCM measurements on films exposed to H 2 Se showed large apparent mass uptakes which were inconsistent with the trends observed using other techniques. This behavior was ascribed to anomalous interactions between H 2 Se gas and the QCM electrodes