Gold Nanoparticles in Novel Green Deep Eutectic Solvents Self Limited Growth, Self Assembly amp; Catalytic Implications

In this article, we are reporting the catalytic activity of gold nanoparticles AuNPs dispersed in a novel eco friendly Deep Eutectic Solvent DES; choline chloride and urea at room temperature. A low energy sputter deposition method is employed to synthesize AuNPs on the DES surface. This is a simple, economical and clean method for producing monodisperse gold nanoparticles by a self limited growth mechanism. Detailed Small Angle X ray Scattering SAXS , UV Vis and Transmission Electron Microscopy TEM investigations show the formation of spherical AuNPs of 5 nm in diameter. Moreover, these particles have a strong tendency to self assemble at the DES surface as well as into the bulk. This is a new addition to a novel generation of gold based catalysts. The catalytic activity of Au nanoparticles in DES is revealed quantitatively by analyzing the apparent conversion reaction rate constant amp; 119896;app of para nitrophenol to paraaminophenol in the presence of sodium borohydride. Catalytic activity reported in the present article ismuch faster amp; 119896;app 0.34 s amp; 8722;1 than the rate reported earlier amp; 119896;app 0.030 min amp; 8722;1 by Chirea et al. for gold nanowire networks [Langmuir, 2011, 27, 3906]. In agreement with the literature, we explain the higher catalytic activity in terms of a larger surface area of AuNPs in a non self assembled state. Keywords Catalysis, Para Nitrophenol Reduction, Reaction Kinetics, Gold, Nanoparticles, Self Limited Growth, Self Assembl