Adsorption and Desorption Behavior of an Anionic Pyrene Chromophore in Sequentially Deposited Polyelectrolyte-Dye Thin Films

Abstract

Alternating thin films of the anionic dye pyrenetetrasulfonic acid (4-PSA) and poly(allylamine hydrochloride) (PAH) were formed by the squential deposition of 4-PSA and PAH from aqueous solution onto solid substrates. Film growth was followed by absorption spectroscopy, and the resulting polyelectrolyte-dye multilayer assemblies were characterized by using fluorescence spectroscopy, X-ray reflectivity, and atomic force microscopy (AFM) measurements. 4-PSA was successfully deposited in alternation with PAH when the ionic strength of the PAH solution was greater than 0.1 M. At each PAH adsorption step a given amount of previously adsorbed 4-PSA was extracted. The amount of dye released depended on the film thickness and the salt concentration in the PAH solution from which PAH was subsequently adsorbed. However, the total amount of dye remaining in the film after PAH deposition was essentially independent of the salt content in the PAH solution. Both X-ray reflectivity and AFM measurements revealed a high r...