ELECTROSTATIC COMPLEXATION OF CARBOXYLIC-ACID DERIVATIZED SILVER COLLOIDAL PARTICLES WITH FATTY AMINE LANGMUIR MONOLAYERS - ROLE OF NEUTRALSPACER MOLECULES IN THE MONOLAYER

In a series of papers we have investigated the electrostatic complexat ion of carboxylic acid-derivatized metal colloidal particles with char ged fatty amine Langmuir monolayers and the formation of Langmuir Blod gett (LB) films of the colloidal particles. The role of the subphase p H in controlling the cluster density at the air-water interface and in the builtup films was addressed. In this paper we advance our study t o include the effects of an uncharged spacer molecule, octadecanol, on the colloidal particle complexation at the air-water interface in mix ed Langmuir monolayers of octadecanol and octadecyl amine. The surface density of the charged amine molecules was controlled by varying the molar concentrations of amine and alcohol molecules in the Langmuir mo nolayer and the time dependence of the complexation followed using pi- A isotherms, quartz crystal microgravimetry and UV-vis spectroscopy me asurements. The equilibrium cluster density at the air-water interface and consequently in the LB films was enhanced as the fraction of amin e molecules in the Langmuir monolayer increased. The complexation of t he clusters at the air-water interface is slow, taking similar to 15 h to reach equilibrium densities. Cluster density-dependent shifts in t he surface plasmon resonance were observed in builtup LB films and hav e been explained in terms of an effective medium theory. Ellipsometry studies of the builtup multilayer films indicate that fairly uniform c luster density films can be deposited by the LB technique. The results presented in this paper are consistent with an electrostatic interact ion-mediated process for the complexation of carboxylic acid-derivatiz ed colloidal particles with fatty amine Langmuir monolayers.