Discovery Magazine

Photo Credit: Aaron Funk

Controlling electronic, desolvation and cooperative effects at gold nanoparticle surfaces for enhanced catalysis

Reactions involving homogeneous catalysis, particularly those involving hydrolytic mechanisms, are a critical area to research to enable the development of new countermeasure approaches against chemical and biological WMD. We are interested in understanding the basis of how to enhance metal-based homogeneous catalysis or heterogeneous catalysis that can be directed to either chemical agents neutralization and/or bacterial/viral decontamination.

Homogeneous catalysis can be finely tuned, both sterically and electronically, through a judicious selection of ligands, neutral molecules, or ions bound either covalently or electrostatically to the catalytically active metal ion center. We propose to further enhance hydrolysis using a novel approach that combines electronically-modulated homogeneous catalysis - via molecular wires attached to nanoparticle (NP) surfaces - with additional desolvation effects, as well as decreased conformational freedom, and cooperative effects of ligand stabilized multi-metallic catalytic centers at NP surfaces. We are also investigating the unique photophysical properties of metal nanoparticles (NPs) and how they can be used to enhance homogeneous catalysis. Our goal is to enhance catalytic rates via laser-induced plasmonic effects, an area of research using active plasmonics to drive chemical reactions at nanoparticle surfaces.

Enhanced catalytic hydrolysis of organophosphate esters p-bis(nitrophenyl)phosphate (BNPP) and methyl parathion under homogeneous conditions was achieved by irradiating 10 nm gold nanoparticles capped with thiol-functionalized copper(II) bipyridine complexes. It was demonstrated that hydrolysis of methyl parathion increased by a factor of x2 via irradiation of the plasmon absorption band (~530 nm) of copper-on-gold nanoparticles using a low power (~120 mW) green laser. In addition, we have further increased kcat/Km by ~12-fold for the hydrolysis of BNPP. This represents the first example of the use of plasmonics in a metal catalyzed hydrolysis reaction. The mechanism and scope of laser-induced catalysis is under investigation.