Controlled growth of the size-quantized CdS at the interface of the stearic acid Langmuir–Blodgett films

Abstract

A pure Y-type transfer form for cadmium stearate (CdSt 2) Langmuir–Blodgett (LB) films was obtained on a subphase of which the pH is suitable (6.4) as a result of using a higher surface pressure. The pressure dependence of the structure of the CdS produced within the LB matrix was observed. Monolayers of CdS were prepared by the exposure of CdSt 2 LB films deposited under higher surface pressure (37.5 mN/m) to H 2S gas at a pressure of 0.25 Torr. If the LB films deposited under lower surface pressure were used as the matrix, CdS would aggregate to the particles within the stearic acid (SA) LB films. And these phenomena suggest a novel means to control the microstructure of aggregates formed. We suggested that it should be ascribed to the larger interaction between the hydrocarbon chains of the LB films in the case of the higher surface pressure. This larger interaction can offer a sufficient position control for the guest sulphide monolayer. At the same time, the reaction speed of the LB films with the H 2S gas, as well as the form speed of CdS, was dependent on the layer number of the LB films and the surface pressure under which the LB films were deposited.