Preparation and Organized Assembly of Nanoparticulate TiO2-Stearate Alternating Langmuir-Blodgett Films

J Colloid Interface Sci. 1997 Aug 15;192(2):275-80. doi: 10.1006/jcis.1997.4996.

Abstract

Nanoparticulate TiO2-stearate Langmuir-Blodgett-type monolayers and multilayers were directly obtained by using TiO2 hydrosol as the subphase. The surface pressure-versus-surface area isotherms showed that the monolayer could be compressed to a mean molecular area of 0.25 nm2. The monolayer was transferred onto a CaF2 or Si substrate at a dipping speed of 18 cm/min and surface pressure of 25 mN/m. It exhibited Y-type multilayer films over the range investigated (1-30 layers) with a transfer ratio of 1.0 ± 0.1. FTIR transmission spectra and linear infrared dichroic spectra provided evidence of the formation of a stable organic/inorganic alternating multilayer with nanoparticulate TiO2 between the organic monolayers. There is only slight absorption in the range of the C;equals;O stretching vibration band of the carboxylic group with the 3- and 6-nm TiO2 nanoparticles. This means that TiO2 particles are packed closely; i.e., the surface coverage is very high. A possible structure consists of layers of nanoparticles in close-packed form with two stearate ion layers inbetween. But it can be seen that there are some carboxylic groups (1700 cm-1) not connected to the 20-nm TiO2 nanoparticle. Electron microscopic (TEM) images of TiO2-stearate monolayers show that high-coverage monolayers were obtained when the surface pressure increased to 25 mN/m and the dipping speed to 18 cm/min. Copyright 1997Academic Press