Preparation of Organic-Inorganic Nano-Composite Films by the Assistance of Molecular Assembly Systems

Preparations of an organic-inorganic nano-composite film based on the synthesis of nano-sized inorganic materials in molecuar assembly films have been described. Exposure of metal stearate Langmuir-Blodgett (LB) films to H2S and HI gases results in the formation of size-quantized metal sulfides (CdS, ZnS, PbS) and PbI2, respectively, in the stearate LB films. When the metal sulfide-bearing composite film was subjected repeatedly to a cycle of immersion in aqueous solutions of the corresponding metal ion (I) and the exposure to H2S gas (S), a nano-order increase in the size of the metal sulfide was observed. The dimension of size-quantized CdS formed in LB films was also controlled precisely by the occupied molecular area of amphiphiles which regulates the concentration of Cd2+ ions introduced in the hydrophilic interlayers. When the CdS-bearing stearate LB film was subjected alternately to the intercalation of Pb2+ ions and sulfidation, a composite film in which size-quantized CdS and PbS coexisted was produced. On the structure of CdS bearing stearate LB films, the existence of an ordered (crystalline) region consisting of a layered structure of stearic acid and CdS sheets was suggested from IR and X-ray diffraction results. Third-order optical nonlinearity of the PbS-bearing composite system was relatively large and was optimizedby the amount and size of PbS.