Near-Field Scanning Optical Microscopy Studies of a Fluorescent Polyelectrolyte−Surfactant Complex

Abstract

Thin films prepared from a complex formed between poly(vinyl sulfate) (PVS) and a cationic indocarbocyanine surfactant dye (DiI) are investigated by near-field scanning optical microscopy (NSOM) and atomic force microscopy (AFM). Local film morphology and chemical composition are studied as a function of dye/anionic-site stoichiometry. AFM images show that overall film morphology changes modestly with dye content. Fluorescence NSOM images reveal that at lowest PVS loading, the films are extremely heterogeneous, exhibiting round fluorescent regions 100−250 nm in size. As the dye content is increased, the fluorescent regions increase in number but remain of similar sizes. NSOM fluorescence spectra prove these regions contain aggregated DiI and indicate they are likely polymer−surfactant micelles entrapped in the films.