Formation of hybrid monolayers and Langmuir–Blodgett-type multilayers from ammonium cations and TiO 2 crystalline nanosheets

Abstract

A novel hybrid monolayer composed of ammonium cations and TiO 2 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 □ x/4 O 4·H 2O ( x∼0.7; □, 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-TiO 2. 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/TiO 2 alternating structure with a repeating unit of 3.4 nm.