Nanoscale coatings of AuAlx and PtAlx and their mesoporous elemental derivatives

A method to produce nanoscale films of AuAlx and PtAlx, and their mesoporous elemental derivatives is described, and the morphology and optical properties of these coatings explored. The color of the AuAlx film is bright purple, in agreement with ab initio calculations and experimental observations for the compound AuAl2, but becomes black after de-alloying with NaOH. The film of PtAlx is silver-grey and changes to grey after being converted to mesoporous Pt by de-alloying. Both mesoporous coatings exhibit a very rough surface, with pores of between 2 and 20 nm in diameter, and display a significantly more absorptive optical characteristic compared to their ordinary elemental counterparts.