Intercolloidal particle monolayer transfer in mixed metal colloids

Abstract

In this paper, we provide the first evidence that suggests transfer of molecules in self-assembled monolayers between colloidal metal particles. This was studied by capping silver/gold colloidal particles with a bifunctional molecule, 4-carboxythiophenol, and then mixing to the capped sol, uncapped colloidal particles of gold/silver. The transfer of the capping molecule to the bare metal particle surface leads to carboxylic acid derivatization of the uncapped sol as well. The resulting carboxylic acid derivatization of the uncapped clusters by intercolloidal particle monolayer transfer was determined by electrostatic complexation of the clusters in the mixed hydrosol at the air-water interface with a Langmuir monolayer of octadecylamine, the carboxylic acid groups playing the role of sticky "tracers". Optical absorption spectroscopy and energy dispersive analysis of X-rays measurements of Langmuir-Blodgett films formed from subphases of sols of capped silver/gold mixed with uncapped gold/silver revealed the presence of both silver and gold particles in the film thereby pointing to the transfer of molecules between the colloidal particles. Possible mechanisms for the intercolloidal particle monolayer transfer observed are briefly discussed.