INTERCOLLOIDAL PARTICLE MONOLAYER TRANSFER IN MIXED-METAL COLLOIDS

In this paper, we provide the first evidence that suggests transfer of molecules in self-assembled monolayers between colloidal metal partic les. This was studied by capping silver/gold colloidal particles with a bifunctional molecule, 4-carboxythiophenol, and then mixing to the c apped sol, uncapped colloidal particles of gold/silver. The transfer o f the capping molecule to the bare metal particle surface leads to car boxylic acid derivatization of the uncapped sol as well. The resulting carboxylic acid derivatization of the uncapped clusters by intercollo idal particle monolayer transfer was determined by electrostatic compl exation of the clusters in the mixed hydrosol at the air-water interfa ce with a Langmuir monolayer of octadecylamine, the carboxylic acid gr oups playing the role of sticky ''tracers''. Optical absorption spectr oscopy and energy dispersive analysis of X-rays measurements of Langmu ir-Blodgett films formed from subphases of sols of capped silver/gold mixed with uncapped gold/silver revealed the presence of both silver a nd gold particles in the film thereby pointing to the transfer of mole cules between the colloidal particles. Possible mechanisms for the int ercolloidal particle monolayer transfer observed are briefly discussed .