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Home page > Metallic nanoparticles synthesis within self-organized surfactant systems

Contributors : R. Krishnaswamy (PhD Student), B. Pansu , M. Impéror, C. Even, P. Davidson Collaborator : Hynd Remita (Laboratoire de Chimie Physique, Orsay)

Various procedures have been proposed to synthesize metallic nanoparticles by reduction of metallic salts. Compared with chemical reducing processes, radiolysis induces homogenous nucleation and growth in the whole volume. Small and monodisperse particles can thus be obtained. In collaboration with Hynd Remita (LCP, Orsay), our goal was to study the effect of confinement on the shape and size of metallic nanoparticles produced by radiolysis. Metallic solutions of metallic salts (PtII, Au III ,…) confined between surfactant bilayers have thus been irradiated with -rays under various conditions (concentrations, dose rate…) and systematically analysed by TEM after radiolysis. This was part of the post doctoral work of Rema Krishnaswamy (LPS, Orsay). Several surfactants have been tested and among them Cetyl Trimethyl Ammonium Bromide (CTAB). Radiolysis of a lamellar complex CTAB /PtII, at room temperature and with some hexanol, leads to the formation of single-crystalline Pt nanorods, monodisperse in diameter (3-4 nm) and 20 to 60 nm long. Whereas many synthesis on gold or silver nanorods have been proposed, this is the first report for monocrystalline platinum nanorods.

During radiolysis, small platinum particles (diameter 3nm) are created and they begin to coalesce after 24h radiolysis. To observe the nanoparticles using transmission electron microscopy (LPS, Orsay) the surfactant is dissolved with a short alcohol (isopropanol). The structure of the CTAB/PtII complex as well as the structure of the Pt nanoparticles (FCC) have been studied by X-ray scattering (LPS).

Platinum nanorods observed by high resolution transmission electron microscopy after removing the surfactant..

The mechanism that leads to the nanorods formation after the end of radiolysis is still under study. It could combine two different mechanism: the coalescence of the seeds created by radiolysis as well as a slow reduction of the remaining platinum salt by hexanol. The resulting shape anisotropy could be due to the competition between CTAB and hexanol adsorbed on the seeds surface. A systematic study of the physical and chemical conditions that are necessary to induce rods is on (post-doctoral work of Geeta Surendran, LCP, Orsay).

Reference: One-step synthesis of single-crystalline Platinum nanorods within a ‘soft’ crystalline surfactant–Pt(II) complex, R. Krishnaswamy, H. Remita, M. Impéror-Clerc, C. Even, P. Davidson, B. Pansu ChemPhysChem 2006, 7, 1510-1513.