Electrostatic entrapment of chloroaurate ions in patterned lipid films and the in situ formation of gold nanoparticles

The formation of gold nanoparticle assemblies in a patterned manner on suitable substrates is described. The protocol for realizing such structures comprises the following steps. In the first step, patterned films of a fatty amine are thermally evaporated onto solid supports using suitable masks (e.g. a TEM grid). Thereafter, the fatty amine film is immersed in chloroauric acid solution and chloroaurate (AuCl₄^-) ions entrapped in the lipid matrix by electrostatic complexation with the ammonium ions of the fatty amine molecules. The final step involves the reduction of the AuCl₄^- ions in situ thus leading to the formation of gold nanoparticles within the patterned lipid matrix. The process of metal ion incorporation and reduction may be repeated a number of times to increase the nanoparticle density in the lipid matrix. AuCl₄^- ion entrapment and formation and gold nanoparticles within the patterned lipid matrix has been followed by quartz crystal microgravimetry, UV-vis spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy and energy dispersive analysis of x-ray measurements. The protocol described shows immense potential for extension to assemblies of nanoparticles in more intricate patterns as well as to the growth of semiconductor quantum dots in such patterns.