Langmuir−Blodgett Films of Heteropolyoxometalate/Organomercury Acetylide Hybrid Composites: Characterization and Photoelectric Properties

A new family of organometallic/inorganic nanohybrid Langmuir−Blodgett (LB) films consisting of rigid-rod organomercury acetylide complex (OMA-C 16 or OMA-C 8 ) as the π-conjugated organometallic molecule, tungsto(molybdo)phosphoric heteropolyacids HPA (HPA = H 3 PMo 12 O 40, H 3 PW 12 O 40, H 6 P 2 Mo 18 O 62, or H 6 As 2 W 18 O 62 ) of the Keggin and Dawson structures as the inorganic component, and octadecylamine (ODA) as the auxiliary film-forming agent were prepared and characterized by π− A isotherms, UV−vis absorption spectra, fluorescence spectra, atomic force microscopy imaging, scanning tunneling microscopy, surface photovoltage spectroscopy, and low-angle X-ray diffraction. Our experimental results indicate that steady, even, and ordered Langmuir and LB films are formed in pure water and heteropolyacid subphase. They typically have a highly organized lamellar structure in which a monolayer of HPA is arranged alternately with well-ordered layers of OMA (and also ODA for OMA-C 16 ) and the periodicity of the layered structure for the OMA-C 16 /ODA/H 3 PMo 12 O 40 LB film is ca. 3.7 nm. Luminescence spectra of hybrid LB films show that HPA can quench the emission of OMA-C 16 and OMA-C 8 to some extent. These LB composites show good photovoltage responses and a photovoltage of 103 μV can be obtained for the OMA-C 16 /ODA/H 3 PMo 12 O 40 system when it is excited by light at 330 nm. The monolayer LB films on silica wafer can also display interesting electrical conductivity behavior.