Metal ion reductions by femtosecond laser pulses with micro-Joule energy and their efficiencies

Chemical reactions of metal ions in solution were studied using 800 nm, 90 femtosecond laser pulses with a laser intensity range beginning at sub-micro-joules/pulse, where the intensities were at or just below supercontinuum generation. Products were observed as surface resonance absorptions assignable to Ag, Au nanoparticles (NPs) and light scattering, indicating the formation of Pd NPs. The consumption efficiencies of metal ions from the Au and Pd ions were estimated to be 10(-3) per incident photon. The major absorbing species of the laser energy was water, which led to the formation of solvated electrons that acted as a reducing agent of metal ions, while direct multi-photon dissociation to neutral atoms was unlikely. Metal ion Fe3+ and Yb3+ systems are also discussed, where Fe3+ to Fe2+ was ascribed to two-photon absorption and Yb3+ to Yb2+ to a reduction followed by solvent ionization. (C) 2016 Elsevier B.V. All rights reserved.