Optical sensing to organic vapors of fluorinated polyimide nanocomposites containing silver nanoclusters

Polyimide-silver nanocomposite films were prepared by surface modification with KOH aqueous solution followed by K-assisted Ag doping and thermal reduction in hydrogen-containing atmosphere. The film porosity was controlled by dispersing into the polymer the compound azodicarbonamide, which decomposes and desorbs during thermal treatment, thus generating a more porous structure. After heat treatment in reducing atmosphere, the films present mono-dispersed metallic nanoparticles with average size of about 5 nm and a narrow size distribution. The exposure to water, acetone and ethanol vapors causes absorbance changes of the plasmon absorption peak of silver, which are ascribed to the changes of the refractive index of the embedding medium. The reversible absorbance changes and the fast response (40–160 s) over a concentration range from 800 to 88,000 ppm make these nanocomposite films useful for optical detection of organic vapors.