Ultrastable Plasmonic Cu-Based Core–Shell Nanoparticles

Abstract

Cu\nis the cheapest plasmonic metal showing plasmonic resonance\nin the visible region, which makes it highly attractive in various\nfields (e.g., sensing, surface-enhanced Raman scattering, and photocatalysis).\nHowever, its poor chemical stability severely restricts its application.\nHerein, we develop a seed-mediated approach to synthesize ultrastable\nCu-based nanoparticles (NPs) stabilized with a thin, completely covered\nshell. By precisely controlling the reaction conditions, we are able\nto achieve uniform plasmonic Cu–Au core–shell NPs with\nsignificantly enhanced chemical stability even in a harsh environment\nin the presence of a strong oxidizing acid (HNO₃) solution.\nIn-depth characterizations and analysis allow us to identify the critical\nrole of the external crystalline Au layer, as compared to the AuCu\nalloy layer, in achieving superior stability. Furthermore, a deeper\nunderstanding of the plasmonic spectra was obtained by correlating\nthe theoretical calculations on NPs of different core–shell\ndimensions with experimental results. Transient absorption measurements\nreveal that the plasmon dynamics and the heat transfer coefficients\nare not affected with the shell formation. As a proof of concept,\nthese NPs demonstrate high photothermal efficiency and chemical stability\nfor solar steam generation. This work offers a general strategy for\nthe synthesis of ultrastable cost-effective, plasmonic Cu-based NPs,\nwhich show great potential in catalysis, electronics, and optics.