Synthesis of Au-Core/Pt-Shell Nanoparticles within Thermally Evaporated Fatty Amine Films and Their Low-Temperature Alloying

The low-temperature alloying of bimetallic Au−Pt nanoparticles entrapped within thermally evaporated fatty amine films by a novel ion-exchange technique is described. Nanoparticles of gold and platinum were grown in thermally evaporated octadecylamine films by immersion of the film sequentially in solutions containing AuCl 4 - ions and PtCl 6 2 - ions followed by their in situ reduction at each stage. Entrapment of AuCl 4 - and PtCl 6 2 - ions in the octadecylamine (ODA) film occurs by selective electrostatic binding with the ammonium ions in the fatty amine matrix. This process leads to the formation of a Au-core/Pt-shell structure of the nanoparticles within the lipid matrix. Thermal treatment of the ODA−(Au-core/Pt-shell) nanocomposite film at 150 °C resulted in the formation of a Au−Pt alloy. The process of AuCl 4 - and PtCl 6 2 - ion incorporation in the ODA matrix and synthesis of the Au−Pt alloy were followed by quartz crystal microgravimetry, Fourier transform infrared spectroscopy, UV−vis spectroscopy, and X-ray diffraction measurements.