SYNTHESIS OF SIZE-CONFINED METAL SULFIDES IN LANGMUIR-BLODGETT-FILMS

Size-confined sulfides of lead, zinc and copper as well as a mixture o f cadmium and lead sulfides have been synthesized in Langmuir-Blodgett (LB) matrices by the repeated processes of sulfidation, by exposing t he metal ion-binding LB films to a flow of H2S gas, and intercalation, by immersing the metal sulfide-bearing LB films into an aqueous solut ion of the corresponding metal ion. Quantum state PbS and ZnS were for med and grown stepwise in the stearate LB films. The interconversion o f carboxylate groups between ionic and acidic forms played a key role in the stepwise growth of the metal sulfides. For the synthesis of cop per sulfide, however, the stearate LB matrix was unavailable owing to the instability of a copper stearate LB film, but copper sulfide, poss ibly Cu2S, was successfully synthesized in an n-octadecylacetoacetate LB film in which the interconversion between the beta-ketonic and enol ic forms was responsible for the binding and release of CU2+ ions. Whe n the CdS-bearing stearate LB film was subjected alternately to interc alation of Pb2+ and sulfidation, it was suggested that PbS was formed and grown on the surface of the preformed CdS.