Publications

A free-standing ultrathin film of a poly(vinyl alc.) (PVA)/titania (TiO2) composite was prepared by spin coating. The thickness of the film was adjusted to 30-50 nm by changing the spin-coating speed and the concentrations of PVA and the TiO2 precursor. A template mol., (4-phenylazo)benzoic acid (4PABA), was introduced into the film as a mixture in the TiO2 precursor and was removed after film formation by dipping the film in aqueous NH3 (1%). Aqueous solutions of tetraphenylporphyrin tetrasulfonic acid (TPPS), 4PABA, and sodium benzoate (SB) were filtered through this film, and the concentrations of these compounds in the filtered solution were monitored by UV-vis absorption measurements. The filtered TPPS solution was colorless, and its absorbance at 413 nm was 8% that of the original solution In contrast, almost 100% of SB and 28.4% of 4PABA were passed through the film. The ultrathin TiO2/PVA film obtained without imprinting with 4PABA had no cavities, and aqueous solutions did not pass through this film. Therefore, the nonimprinted film was defect free and that imprinting of the template mol. in the film resulted in the formation of a size-selective channel across a 40 nm thickness.