Cadmium sulphide (CdS) nanoparticles were grown by the reaction of sodium sulphide (Na₂S) with Langmuir-Blodgett (LB) films of cadmium salts ofn-octadecylsuccinic acid (ODSU) and with LB films of ODSU in mixtures of octadecylamine and octadecyl alcohol. The results indicate that heterogeneous nucleation and aggregation in the pure ODSU LB films due to processes like Ostwald ripening are destabilized by the presence of the long-chain amine and alcohol in mixed systems. CdS nanoparticles in the LB films were monitored by UV-visible absorption spectra, which allow an estimation of the size of the particles. The morphology, size and nature of the nanocrystallites formed depend on whether the sulphidation was done on the pure film or in the mixed films. It is seen that particles of size around 1.6 nm were formed in ODSU/octadecylalcohol and ODSU/ octadecylamine mixed LB films while in pure ODSU films the size was about 2.7 nm. These films showed typical needle-shaped structures, as observed by the optical microscopic technique. Mean size and morphology were confirmed by transmission and scanning electron microscopy, while selective area electron diffraction patterns showed six-fold symmetry and indicated that the CdS crystals grow epitaxially with respect to the monolayer. Further, the crystallisation enhanced in the mixed LB films showed a characteristic zinc oxide (Wurtzite) structure compared with the pure ODSU matrix.

Cadmium complex ofn-octadecyl succinic acid (ODSA) in Langmuir films at air/water interface has been studied using surface pressure-molecular area (π - A) and surface potential-molecular area (ΔV - A) isotherms. The metal complex formed, transferred as LB film onto solid substrates, was analysed using FT-IR and was subjected to sulphidation reaction. Antisymmetric and symmetric carboxylate stretching vibrations have been used to determine the nature of the ODSA/cation complexes. CdS formed after sulphidation of the cadmium complex (ODSACd) showed possible single-electron phenomenon indicating the nanosized nature of clusters formed. Atomic Force Microscopy (AFM) measurements carried out confirmed the size of these CdS clusters.