(121a) Layer-by-Layer Assembly of Charged Species in Non-Polar Media

Electrostatic layer-by-layer (LbL) deposition of charged species including polymers and nanoparticles lead to the generation of nanocomposite thin films with precisely controlled physicochemical properties. Various functional thin films with unique wetting, optical, catalytic and biological properties have been generated during the past two decades. Despite the strong interests in using the LbL deposition for creating functional thin films, the technique has been more or less used with species dissolved in aqueous solutions. In recent years, there has been a growing interest in the assembly of thin films using materials synthesized and suspended in non-polar solvents. Although layer-by-layer deposition could serve as a convenient way to assemble such films, the low permittivity of these solvents restrains these materials from acquiring charge. In our study, we demonstrate that layer-by-laser deposition of charged species can be performed in non-polar media. Charging of various colloidal particles in a non-polar organic solvent, toluene is achieved by using Aerosol-OT (Sodium bis(2-ethylhexyl) sulfosuccinate). While oxide based materials such as titania and alumina became positively charged, carbon-based particles such as carbon black and multiwalled carbon nanotubes (MWCNT) acquired a negative charge. These charged particles in toluene are subsequently used to build Carbon/Al2O3 and MWCNT/TiO2 nanocomposite films via layer-by-layer deposition. Through this process, we show that films with unique properties such as photocatalysis and sheet conductivity are attainable. The high specific area of these nanocomposite films makes them ideal as reactive surfaces.