Formation of hybrid monolayers and Langmuir-Blodgett-type multilayers from ammonium cations and TiO2 crystalline nanosheets

A novel hybrid monolayer composed of ammonium cations and TiO2 crystalline nanosheets was formed at an air-water interface. We employed, as the subphase under the monolayer, stable colloidal suspensions obtained by exfoliating a lepidocrocite-type layered titanate, H(x)Ti(2-x/4)square O-x/4(4).H2O (x similar to 0.7; square, vacancy) into elementary host layers. Surface pressure-area isotherms demonstrated that spreading molecules of dioctadecyldimethylammonium bromide (DODAB) on the suspensions resulted in complexation of DODAB with the exfoliated single layers of quasi-TiO2. The hybrid monolayer was quantitatively transferred onto solid substrates by the Langmuir-Blodgett (LB) technique to form a multilayer film. UV-Visible absorption spectra and X-ray diffraction measurements confirmed that the film possessed a DODAB/TiO2 alternating structure with a repeating unit of 3.4 nm. (C) 2001 Elsevier Science B.V. All rights reserved.