Laser-Based Formation of Copper Nanoparticles in Aqueous Solution: Optical Properties, Particle Size Distributions, and Formation Kinetics

We explore the formation kinetics, optical absorption spectra, and particle size distributions of copper nanoparticles (CuNPs) formed by direct laser ablation from the bulk metal via a process we refer to as Laser Ablation Synthesis in Solution (LASiS). Comparisons are made between CuNPs formed in pure water versus those formed in the presence of 1 x 10(-4) M solutions of the N-donor ligands 4,4'-bipyridine (4,4'Bipy) and 1H-5-(4-pyridyl)tetrazole (T-4Py). CuNPs formed in pure water and in the presence of 4,4'Bipy display similar UV-visible absorption spectra and very similar particle size distributions. In comparison, CuNPs formed in the presence of T-4Py display significantly different absorption properties, with the surface plasmon resonance transition blue-shifted by similar to 55 nm, and a much smaller and narrower particle size distribution compared with the former samples. Based on previous literature reports, it is possible to ascribe these differences to differences in the CuNP surface oxidation states for samples prepared in the presence of T-4Py. However, an analysis of the formation kinetics of all three samples indicates near-identical behaviour.