Preparation, characterization, and electrical properties of dual-emissive langmuir-blodgett films of some europium-substituted polyoxometalates and a platinum polyyne polymer

A new series of organometallic/inorganic composite Langmuir-Blodgett (LB) films consisting of a rigid-rod polyplatinyne polymer coordinated with 2,7-bis(buta-1,3-diynyl)-9,9-dihex- ylfluorene (denoted as PtP) as the π-conjugated organometallic molecule, an europium-substituted polyoxometalate (POM; POM = Na₉EuW₁₀O₃₆,K ₁₃[Eu(SiW₁₁O₃₉)₂]and K ₅EuSiW₁₁H₂O)₂]) as the inorganic component, and an amphiphilic behenic acid (BA) as the auxiliary film-forming agent were prepared. Structural and photophysical characterization of these LB films were achieved by π-A isotherms, absorption and photoluminescence spectra, atomic force microscopy imaging, scanning tunneling microscopy, and low-angle X-ray diffraction. Our experimental results indicate that stable, well-defined, and well-organized Langmuir and LB films are formed in pure water and POM subphases, and the presence of Eu-based POM in the subphase causes an area expansion. It is proposed that a lamellar layered structure exists for the PtP/BA/POM LB film in which the POM and PtP molecules can lay down with the interfacial planes. Luminescence spectra of the prepared hybrid LB films show that nearwhite emission spectra can be obtained due to the dual-emissive nature of the mixed PtP/POM blends. These Pt-polyyne-based LB films displayed interesting electric conductivity behavior. Among them, PtP/BA/POM 13-layer films showed a good electrical response, with the tunneling current up to ±100 nA when the voltage was monitored between - 1and 7 V.