Sol−Gel Preparation of AuCu and Au₄Cu Nanocluster Alloys in Silica Thin Films

Using sol−gel processing and high-temperature annealing, metal alloy nanoclusters of AuCu and Au₄Cu in SiO₂ thin films were synthesized. The crystallographic data show that the lattice parameters of those nanocluster alloys, both showing the fcc structure, are very close to the bulk values. The nanocrystals obtained by annealing at 900 °C were nearly spherical in shape, having the AuCu size of ca. 23 nm in radius and the Au₄Cu size of ca. 35 nm. The peaks of the optical spectra of the samples annealed at 700−900 °C are located at 555 nm for AuCu and at 562 nm for Au₄Cu.