Analysis of the surface chemical composition and morphological structure of vapor-sensing gold-fluoropolymer nanocomposites

A systematic spectroscopic and morphological characterization of gold-fluoropolymer (CFx(Au)) nanocomposites, deposited by ion beam cosputtering, is presented. These composites are technologically relevant, since they exhibit vapor-sensing properties based on swelling phenomena. Analysis by X-ray photoelectron spectroscopy (XPS) allows us to assess that gold codeposition induces a progressive defluorination of the polymeric chains, leading to a significant increase of the polymer chains' branching and of the concentration of unsaturated fluorinated carbons. The presence of a fluoride peak in the F is spectrum proves the formation of polar gold fluorides. Transmission electron microscopy reveals the presence of in-plane homogeneously distributed nanosized gold domains, while angle-resolved X-ray photoelectron spectroscopy indicates a nonhomogeneous in-depth distribution of the gold particles, with the outer surface being less rich in nanoparticles. Results derived from the analytical characterization allow a deeper understanding of the swelling phenomena involved in the sensing processes.