Preparation, characterization and photoelectric properties of dual-emissive Langmuir-Blodgett film of europium-substituted polyoxometalate and zinc(II) porphyrin platinum(II) complex

An organometallic/inorganic composite Langmuir-Blodgett (LB) film was prepared using a rigid-rod zinc(II) porphyrin platinum(II) complex coordinated with trans-bis(ethynylbenzene) (ZnPPt) as the π-conjugated organometallic molecule, and a europium-substituted polyoxometalate (POM), Na9EuW10O36 (EuW10) as the inorganic component. The structure and photophysical properties of the LB film was characterized by π-A isotherms, UV-vis absorption and photoluminescence spectra, atomic force microscopy imaging and scanning tunneling microscopy. The results indicate that stable, well-defined Langmuir and LB films were formed using pure water and POM as subphases. Luminescence spectra of the hybrid LB film showed that the emission spectra were obtained due to the dual-emissive nature of the mixed ZnPPt/EuW10 blends, and EuW10 was able to enhance the emission of ZnPPt. The ZnPPt-based LB film displayed an interesting electrical conductivity behavior. The 3-layer film formed by ZnPPt/EuW10 complex had a strong electrical response, giving rise to a tunneling current up to ± 100 nA when the voltage was monitored at − 1.4-3.1 V. When it was excited by light, the LB composite film generated a photovoltage of 24 μV, indicating that the hybrid film had a strong photovoltage response as well.