Electrostatically controlled diffusion of carboxylic acid derivatized Q-state CdS nanoparticles in thermally evaporated fatty amine films

Abstract

The organization of Q-state semiconductor nanoparticles in thin film form is an important research problem of today. In this paper, we demonstrate that carboxylic acid derivatized Q-state CdS nanoparticles can be incorporated in thermally evaporated fatty amine films through selective electrostatic interaction by simple immersion of the film in the CdS hydrosol. The density of CdS nanoparticles in the amine matrix can be modulated by variation of the hydrosol pH. The kinetics of cluster incorporation has been followed by quartz crystal microgravimetry (QCM) and the data analyzed in terms of a one-dimensional (1D) Fickian type diffusion model. It is found that the 1D diffusion model is an adequate representation of the cluster incorporation process. An interesting film thickness and hydrosol pH dependence of the cluster diffusivity is observed. Fourier transform IR spectroscopy of the thermally evaporated amine films before and after CdS nanoparticle diffusion showed a weak coupling of the clusters with the protonated amine groups as well as an increase in the all-trans packing of the hydrocarbon chains after cluster incorporation. X-Ray photoelectron spectroscopy (XPS) measurements were performed on the CdS nanoparticle films for a chemical characterization of the film surface.