Dual Role of Au nanoparticles in the Catalytic Formation of an Amorphous Polynuclear Peroxo Complex and Surface Enhanced Resonance Raman Scattering

Abstract

We report the catalytic formation of bridged polynuclear peroxo complex of Co(II) and 2-picolylamine (2-PA) in aqueous alkaline medium on the surface of Au nanoparticle. The reaction followed sigmoidal kinetics both in absence and presence of the Au nanoparticle with an order of magnitude higher rate constant in the presence of nanoparticle. Importantly, using UV-Vis spectroscopy, mass spectrometry and surface enhance resonance Raman scattering (SERRS), we conclude the formation of peroxo complex with 2-PA acting as a monodentate ligand. The absorbance of the polynuclear complex at 595 nm and the extinction maximum of (agglomerated) the Au nanoparticles at 750 nm provided the right opportunity to pursue SERRS using 632.8 nm laser excitation. Density functional theoretical calculation indicated that the lowering of HOMO-LUMO energy gap of 2-PA bonded to the nanoparticle surface helped catalyze the reaction.