Highly efficient synthesis of solid-solution alloy nanoparticles by laser-induced reduction for industrial applications

Laser-induced Reduction (LRL) is a physicochemical method for synthesizing nanoparticles by irradiating a solution containing metal ions with high-intensity pulsed laser light. It is simple and environmentally friendly because it does not require reducing agents or high-temperature, high-pressure environments for nanoparticle synthesis. In this method, solid-solution alloy nanoparticles are synthesized by the reduction of metal ions by short-lived radical species generated by the decomposition of solvent molecules in the high-intensity reaction field near the laser focus. In this study, we investigated improvement of the efficiency of nanoparticle synthesis in the LRL method using chemical and optical approaches. In the chemical approach, it was confirmed that the efficiency of nanoparticle synthesis increased by about nine times with the addition of glycerin which is a scavenger for oxidation radicals. Furthermore, the addition of the scavenger also made it possible to synthesize nanoparticles even when the concentration of metal ions in the solution was increased. As a result, the efficiency of nanoparticle synthesis increased by more than 18 times compared to conventional conditions. In the optical approach, two cylindrical lenses were used to focus laser light at two points on the laser axis. It was found that the production efficiency could be improved by up to 1.4 times by changing the distance between the two cylindrical lenses. By combining the chemical and optical approaches, it was shown that the nanoparticle production efficiency could be improved by around 25 times compared to conventional methods. This corresponds to 200 g/month of gold nanoparticles.