Preparation and structure of copper nanoparticle/poly(acrylic acid) composite films

Composite films consisting of metallic Cu nanoparticles dispersed in poly(a crylic acid) (PAA) have been prepared by reduction of Cu2+ from the copper salt of PAA above 220 degreesC under a H-2 atmosphere. Optical absorption p roperties and structures have also been investigated by UV/VIS, WAXD, TEM a nd IR. Spherical Cu particles were found to be homogeneously dispersed in t he PAA and the diameters of the particles were in the range 10-16 nm. The c omposite films exhibited an optical absorption peak centered at ca. 570 nm, which was attributed to surface plasmon resonance of Cu nanoparticles. The composite film made by heat treatment at 220 degreesC was less stable beca use Cu particles in the film were oxidized to Cu2+ ions within several week s, while the composite films prepared by heating above 230 degreesC were st able and the Cu particles in their films were not oxidized. The stability o f the Cu nanoparticles in PAA is suggested to be related to the formation o f ketone groups by condensation reactions between carboxylic acids of PAA a bove 230 degreesC.