Near infrared femtosecond laser synthesizes high entropy alloy nanoparticles in water
image: Electron microscopy image and elemental maps of the synthesized high entropy noble metal alloy nanoparticles.
Credit: Osaka Metropolitan University
High-entropy alloy nanoparticles (HEA NPs) have attracted considerable attention due to their distinctive catalytic and optical properties. Numerous advanced synthetic strategies have recently been developed to overcome elemental immiscibility and enable precise structural control and large-scale production of HEA NPs.
In this study, Osaka Metropolitan University researchers successfully synthesized spherical Rh-Pd-Ir-Pt-Au HEA NPs with a mean diameter of approximately 10 nm in an aqueous mixed metal salt solution without any additional chemical reductants. The hydrated electrons generated by focusing near-infrared femtosecond laser pulses into water drove the simultaneous reduction of metal salts. The addition of polyvinylpyrrolidone (PVP) as a protecting agent effectively decreased the particle size and narrowed the size distribution. Furthermore, the presence of 2-propanol, acting as a hydroxyl radical scavenger, accelerated the consumption rate of precursor ions by a factor of 1.4–1.8. The resulting colloids remained stable for over one month in the presence of PVP.
These findings demonstrate that femtosecond laser-induced reduction offers a versatile, room-temperature, non-contact, and harsh-reagent-free approach for synthesizing multi-element alloy nanoparticles, regardless of the differences in the reduction potentials of the precursors.
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