The effect of membrane charge on gold nanoparticle synthesis via surfactant membranes

The effect of vesicle membrane structure and charge on the synthesis of gold nanoparticles was investigated, The vesicle membranes were comprised of either negatively charged soy lipids or mixtures of charge neutral and negatively charged soy lipids. Palladium ions bound to the membranes served as the catalyst for metal particle synthesis using an electroless metallization procedure. The size range of particles synthesized using membranes comprised of only negatively charged lipids (5-15 nm) was significantly smaller than those synthesized using mixtures of negatively charged and charge-neutral lipids (2-180 nm). X-ray diffraction revealed that the average crystallite size decreased with increasing palladium ion content of the membranes. It also showed that the average crystallite size was smaller for particles synthesized using vesicles comprised of only soy phoshohydroxyethanol lipids than for particles synthesized using vesicles comprised of only soy phosphatidic acid lipids. Particles synthesized with membranes comprised of only negatively charged lipids were encapsulated within the resulting lipid membrane matrix. FT-IR of the lipid matrix indicated that the matrix was formed as the result of ionic bridging of the lipid phosphate headgroups with gold ions. (C) 1999 Academic Press.