Lamellar Langmuir-Blodgett films of hydrophobized colloidal gold nanoparticles by organization at the air-water interface

The organization of hydrophobically modified colloidal gold nanoparticles a t the air-water interface and the formation thereafter of lamellar, multila yer films of the nanoparticles by the Langmuir-Blodgett (LB) technique is d escribed in this paper. The hydrophobization of the gold colloidal particle s was accomplished by the electrostatic extraction of carboxylic acid deriv atized gold particles (synthesized in an aqueous medium, 35 Angstrom in siz e) from solution into thermally evaporated fatty amine films by a simple im mersion procedure. The acid-base complex formed by the association of the c arboxylic acid groups bound to the colloidal particle surface and the amine groups in the lipid matrix leads to the formation of a strongly-bound hydr ophobic sheath of fatty amine molecules around the particles. The colloidal gold particles can thereafter be dissolved in different organic solvents, dried and redispersed repeatedly without significant aggregation of the gol d particles. The hydrophobic gold particles were dissolved in a spreading s olvent and organized on the surface of water. The organization of the parti cles and the formation of multilayer films by the Langmuir-Blodgett techniq ue was followed by surface pressure-area isotherm measurements of the collo idal particle Langmuir monolayer, quartz crystal microgravimetry, ultraviol et-vis spectroscopy and Fourier transform infrared spectroscopy. It was obs erved that a close-packed monolayer of the colloidal particles was formed o n the surface of water and that excellent multilayer films of the colloidal nanoparticles can be grown on different supports by sequential transfer by the LB technique. (C) 2001 Elsevier Science B.V. All rights reserved.