Ultrastable Plasmonic Cu-Based Core-Shell Nanoparticles

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

Automated summary

The study presents a seed-mediated approach to synthesize ultrastable Cu-based nanoparticles with a thin, completely covered shell, achieving uniform plasmonic Cu-Au core-shell NPs with significantly enhanced chemical stability. The critical role of the external crystalline Au layer in achieving superior stability was identified through in-depth characterizations and analysis. These NPs demonstrate high photothermal efficiency and chemical stability for solar steam generation, offering potential in catalysis, electronics, and optics.