Surface derivatization of colloidal silver particles using interdigitated bilayers: a novel strategy for electrostatic immobilization of colloidal particles in thermally evaporated fatty acid/fatty amine films

Abstract

We have recently demonstrated that interdigitated bilayers of fatty acid molecules self-assemble on nanoscale curved surfaces, thereby highlighting an important difference between self-assembly on planar surfaces where such structures have not been reported to form. On a more practical level, this approach leads to a new strategy for derivatization of colloidal particle surfaces without the use of terminally functionalized molecules. In this paper, we use this new strategy to derivatize colloidal silver particle surfaces with carboxylic acid and amine functional groups and, thereafter, to incorporate the colloidal particles in thermally evaporated conjugate fatty lipid films via electrostatically controlled diffusion from the sol. The diffusion of the colloidal particles in the thermally evaporated organic films has been followed using quartz crystal microgravimetry and modeled on the basis of a 1-D diffusion process and the cluster diffusivities determined. It is observed that both the charge on the clusters and the length of the alkyl tail of the molecules in the secondary monolayer (via a hydrophobic interaction contribution) influence the cluster diffusivity in the thermally evaporated films. The cluster-incorporated films have been further characterized using optical absorption spectroscopy and X-ray photoemission spectroscopy.