The formation of inorganic-organic hybrid films of a titania nanosheet and an amphiphilic alkylammonium cation has been investigated, and the photocatalytic decomposition of the alkylammonium cation in the film has been pursued. When a solution of the amphiphilic alkylammonium salt (octadecylammonium chloride: ODAH+ Cl-) was spread on an interface between the air and a titania nanosheet suspension, the negatively charged nanosheets were adsorbed onto the floating monolayer of ODAH+ to form a hybrid monolayer. The hybridization was confirmed by pi-A isotherm measurements, atomic force microscopy, and X-ray photoelectron spectroscopy. Multilayered films were fabricated in a layer-by-layer way by transferring the hybrid monolayers onto glass plates. Areas per ODAH+ cation in the films were estimated from the infrared (IR) spectra of the films, but these areas were smaller than those estimated from the pi-A isotherm curves. The orientation of the alkyl chain of ODAH+ in the hybrid film was determined by means of polarized IR spectroscopy. The alkyl chains were tilted 41 +/- 1 degrees and 47 +/- 1 degrees from the surface normal for the films prepared from the 8 and 20 ppm (ppm = mg dm(-3)) suspensions, respectively. Together with X-ray diffraction data of the films, the structure of the hybrid film was discussed. When the films were illuminated with a UV light, the absorption intensities due to the alkyl chain of ODAH+ decreased exponentially, indicating the photocatalytic decomposition of ODAH+ by the titania nanosheets in the films. Deviation from the exponential trend in the decomposition rate was observed in the initial period for the hybrid films prepared from the suspensions at low concentrations. Interestingly, the layered structure of the hybrid film was disturbed significantly after the ODAH+ cations were decomposed.

Hybrid multilayers of titania nanosheet, amphiphilic alkylammonium cation, and (rac-or Λ-)Ru(II) complex cation have been prepared by a modified Langmuir-Blodgett technique. When a solution of octadecylammonium chloride (CH 3 (CH 2 ) 17 NH 3 + Cl -: ODAH + Cl -) was spread at an interface between the air and an aqueous dispersion of the negatively charged nanosheets, the nanosheets were adsorbed onto the floating monomolecular film of ODAH + to form a hybrid film at the interface. The surface of the hybrid film deposited on a substrate was immersed in an aqueous [Ru(bpy) 3 ]Cl 2 solution. By repeating these procedures, the hybrid multilayer was fabricated. Electronic and infrared spectra of the multilayers indicated layer-by-layer deposition of the hybrid monolayers. X-ray diffraction patterns of the films showed that the layer structure for the film of Λ-[Ru(bpy) 3 ] 2+ was perturbed rather than that of rac-[Ru(bpy) 3 ] 2+ . The second-harmonic generation (SHG) from the hybrid film of Λ-[Ru(bpy) 3 ] 2+ was much more intense than that from the film of rac-[Ru(bpy) 3 ] 2+ , because the former system included noncentrosymmetric component of the optical active (enantiomeric) Ru(II) complex. The IR spectral data for the film of Λ-[Ru(bpy) 3 ] 2+ indicated that the water content in the film increased by the illumination of visible light at 465 nm. However, only a small increase in the water content was observed for the film of rac-[Ru(bpy) 3 ] 2+ when it was illuminated by the visible light. These results were explained by the following mechanism; the visible light irradiated to the hybrid film of Λ-[Ru(bpy) 3 ] 2+ was changed to the ultraviolet light by the SHG effect of the film, which induced superhydrophilicity on the surface of the titania nanosheet. The water content in the film increased, so that the layer structure was perturbed. On the contrary, the SHG-inactive film of rac-[Ru(bpy) 3 ] 2+ kept the layer structure.