(492d) Synthesis of Thiol Capped Gold Nanoparticles and Their Immobilization on a Substrate

Ligand protected gold nanoparticles are being used in many fields of science from physics, chemistry to medicine. Ligand shell serves a critical role, providing the particles with a long series of properties as stability against coalescence, solubility in many solvents and assembly properties. Two dimensional assemblies of monodisperse metal particles with controlled size in the nanometer range present considerable interest in various applications of nanophysics, magnetic properties of ultrahigh density media storage and nanoelectronic devices.

Recently magnetism has been observed in gold NPs capped with dodecanethiol, in spite of the diamagnetic behavior of the bulk gold. For these free NP's, the magnetic moments can fluctuate because of nanoparticle rotation, hence prohibiting their application where permanent magnetic moments are required. Furthermore, the continuous movement of the nanoparticles prevents their use in creating patterns of stable magnetic fields. These problems can be overcome by creating an ensemble of nanoparticles.

In this work, we have synthesized 16-meracaptohexadecanoic acid capped gold nanoparticles by one-phase cold synthesis method to get uniform sized thiol stabilized Au particles without leaving hydrogen bound unreacted thiols. Later we report on the immobilization of these nanoparticles on Si/Au substrate through covalent binding to enhance their stability in magnetic field. The covalent bonding of nanoparticles is confirmed using the spectroscopic techniques such as X-ray photoelectron spectroscopy (XPS) and UV-Vis spectroscopy. The surface morphology of nanoparticles was studied by using Field emission scanning electron microscopy (FESEM).