Formation of Au(III)-DNA Coordinate Complex by Laser Ablation of Au Nanoparticles in Solution

Abstract

We discovered that an Au(III)-DNA coordinate complex, Au(III)(DNA-base)2(amine)l, are formed by laser ablation of Au nanoparticles in an aqueous solution containing DNA molecules in the presence of amines and multi-valent cations, where l represents an unknown ligand (either amine or water). Optical absorption spectrum of the solution after laser ablation exhibited a 360 nm absorption peak assigned to ligand→Au(III) charge transfer (LMCT) band of the coordinate complex. The complex is considered to be formed as follows: 1) the DNA molecules are neutralized by binding the multi-valent cations to their negatively charged phosphate groups, and adsorbed on the surface of the Au nanoparticles by a hydrophobic interaction, 2) Au(III) ions are liberated from the Au nanoparticles by laser ablation, and 3) an Au(III) ion reacts with amine and two DNA bases of a DNA molecule into an Au(III)(DNA-base)2(amine)l.