The design, synthesis and characterization of biologically synthesized nanomaterials have become an area of significant interest. In this paper, we report the extracellular synthesis of gold and silver nanoparticles using Emblica Officinalis (amla, Indian Gooseberry) fruit extract as the reducing agent to synthesize Ag and Au nanoparticles, their subsequent phase transfer to an organic solution and the transmetallation reaction of hydrophobized silver nanoparticles with hydrophobized chloroaurate ions. On treating aqueous silver sulfate and chloroauric acid solutions with Emblica Officinalis fruit extract, rapid reduction of the silver and chloroaurate ions is observed leading to the formation of highly stable silver and gold nanoparticles in solution. Transmission Electron Microscopy analysis of the silver and gold nanoparticles indicated that they ranged in size from 10 to 20 nm and 15 to 25 nm respectively. Ag and Au nanoparticles thus synthesized were then phase transferred into an organic solution using a cationic surfactant octadecylamine. Transmetallation reaction between hydrophobized silver nanoparticles and hydrophobized chloroaurate ions in chloroform resulted in the formation of gold nanoparticles.

The influence of structured organic surfaces on the oriented overgrowth of inorganic crystals is a fundamental aspect of biomineralization. This paper describes the dramatic changes in the crystallization of calcium carbonate within thermally evaporated stearic acid films by varying the pH of the electrolyte solution. Reaction of CO2 with electrostatically entrapped Ca 2+ ions within the lipid films leads to the in situ growth of CaCO3 crystals. Whereas crystallization at pH ) 6 gave rise to calcite of rhombohedral morphology, crystals nucleated at pH ) 3 of the electrolyte solution were discrete crystals of the metastable polymorph, vaterite, along with calcite exhibiting unusual morphology. The process of Ca 2+ ion incorporation in the stearic acid matrix was followed by quartz crystal microgravimetry and Fourier transform infrared spectroscopy, while scanning electron microscopy and X-ray diffraction measurements were employed to study the morphology and orientation of the crystallites within the lipid bilayer stacks.

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The low-temperature alloying of Ag/Pd nanoparticles synthesized in a fatty acid film by a novel ion-entrapment process is described. Nanoparticles of silver and palladium were grown in thermally evaporated fatty acid (stearic acid) films by immersion of the film sequentially in solutions containing Ag + ions and Pd 2+ ions followed by their in-situ reduction at each stage. Incorporation of Ag + and Pd 2+ ions into the stearic acid film occurs by selective electrostatic binding with the carboxylate ions in the fatty acid matrix. It is observed that the reduction of the Pd 2+ ions in the stearic acid-Ag nanocomposite film leads to the formation of a mixture of individual Ag and Pd nanoparticles as well as particles in the Ag-core/Pd-shell structure. Thermal treatment of the stearic acid-(silver + palladium) nanocomposite film at 100°C resulted in the formation of an AgPd alloy. The process of Ag + and Pd 2+ ion incorporation in the stearic acid matrix, their reduction to form metallic nanoparticles, and synthesis of the Ag-Pd alloy were followed by quartz crystal microgravimetry (QCM), Fourier transform infrared (FTIR) spectroscopy, transmission electron microscopy (TEM), UV-vis spectroscopy, and X-ray diffraction (XRD) measurements.

Nanoparticles of silver and nickel were grown in thermally evaporated fatty acid (stearic acid) films by immersion of the film sequentially in solutions containing Ag+ ions and Ni2+ ions. Attractive electrostatic interaction between the metal cations and the carboxylate ions in the fatty acid film leads to entrapment of the cations in the film. Thereafter, the metal ions were reduced in situ to yield nanoparticles of Ag and Ni of ∼30 nm diameter within the fatty acid matrix. Thermal treatment of the stearic acid-(silver+nickel) nanocomposite films led to the formation of a Ni–Ag alloy at ∼100 °C. Prolonged heat treatment at this temperature resulted in the phase separation of the alloy and the reformation of individual Ag and Ni nanoparticles.