Enhanced and Spectrally Selective Near Infrared Photothermal Conversion in Plasmonic Nanohelices

The photothermal conversion in plasmonic nanohelices is studied, unveiling how helical nanostructures made from metals with a notable interband activity ‐such as cobalt (Co) and nickel (Ni)‐ exhibit a remarkable temperature rise Δ T up to ≈1000 K under illumination. Such outstanding Δ T values exclusively occur at wavelengths close to their localized plasmon resonances (Δ T is significantly lower off resonance), and therefore the photothermal conversion of these nanoparticles is spectrally selective. The exceptional and spectrally selective temperature rise is demonstrated at near infrared (NIR) wavelengths, which prompts the use of Co and Ni helical nanoparticles in a wide range of photothermal applications including solar energy conversion, seawater desalination, catalysis, or nanomedicine.