Highly ordered macroporous gold and platinum films formed by electrochemical deposition through templates assembled from submicron diameter monodisperse polystyrene spheres

Here we report a simple and versatile technique for the preparation of novel macroporous three-dimensional gold and platinum films with regular submicron spherical holes arranged in a close-packed structure. Gold and platinum films were prepared by electrochemical reduction of gold or platinum complex ions dissolved in aqueous solution within the interstitial spaces between polystyrene latex spheres (500 or 750 nm in diameter) assembled on gold surfaces. The latex sphere templates were subsequently removed by dissolving in toluene to leave the structured metal films. Scanning electron microscopy of the gold and platinum films shows a well-formed regular three-dimensional, porous structure consisting of spherical voids arranged in a highly ordered face-centered cubic (fcc) structure. The spherical voids have the same diameter as the latex spheres used to form the template. Within the metal film the spherical voids are interconnected through a series of smaller pores. The metallic framework is dense, self-supporting, and free from defects. X-ray studies show the metal to be polycrystalline with a grain size smaller than 100 nm. The optical reflectivity of the macroporous gold and platinum films shows strong diffractive optical properties, which are potentially useful in many existing and emerging applications.