PREPARATION AND STRUCTURE OF QUANTUM-SIZED CADMIUM-SULFIDE GROWN IN AMPHIPHILIC OLIGOMER LANGMUIR-BLODGETT-FILMS

An amphiphilic oligomer, polymaleic acid with octadecanol ester (PMAO) , with ratios of 2:1, 3.7:1 and 6:1 between the carboxylic groups and the hydrocarbon chains, was synthesized and has been used as a matrix to form and grow quantum dot-sized CdS particles. The formation of qua ntum-sized CdS particles during exposure of Langmuir-Blodgett (LB) fil ms of CdPMAO to hydrogen sulfide has been studied using Fourier transf orm infrared spectroscopy and UV-vis absorption spectra. This showed t hat hydrogen bonding of the PMAO molecules were replaced by the metal ion (Cd2+) bridges to form the bridging complex structures before the reaction with H2S. The intensities of the asymmetric nu(a)(COO-) and s ymmetric nu(s)(COO-) stretching modes were reduced after the reaction. But the presence of the asymmetric nu(a)(COO-) and symmetric nu(s)(CO O-) stretching mode in spectra implied that not all the CdPMAO oligome rs in the film were converted to PMAO after exposure to H2S gas. The r esult from the UV-vis absorption spectra indicated that the CdS within PMAO LB films showed a larger blue shift of the optical absorption ed ge with the decrease of the ratio between the carboxylic groups and th e hydrocarbon chains. Moreover, it could be deduced that the size of t he aggregate of the sulfides within PMAO LB films was smaller than tha t formed in stearic acid LB films. (C) 1998 Elsevier Science S.A. All rights reserved.