Defect Damping-Enhanced Plasmonic Photothermal Conversion

Significantly increasing the photothermal conversion of plasmonic nanostructured particles (PNPs) is a common goal for all applications of thermoplasmonics, but it is still in challenge, especially for PNPs with the morphology and composition required for a specific photothermal application. Here, we present a concept of defect-induced damping-enhanced photothermal conversion, which favors PNP intrinsic properties. A model of a defect-damped harmonic oscillator is established to depict photothermal conversion correlation with the structure of PNPs and is capable of accurately reproducing the optical performance of the PNPs with the local surface plasmon resonance far from the interband transition. The theoretical model analyses demonstrate that the defect-induced damping can significantly suppress the light scattering of the PNPs and effectively improve their photothermal conversion efficiency. Especially for the PNPs with a sufficiently large size (larger than ∼100 nm for Au and Ag), we show that defect-induced damping can significantly enhance their light absorption and photothermal performances. These are experimentally confirmed. Typically, defect-enriched Au nanostars with ∼100-150 nm profile size were fabricated and showed much higher photothermal performance and a big increment by 23% in photothermal conversion efficiency, compared with the normal (or defect-impoverished) counterpart. Furthermore, the in vitro and in vivo biological experiments demonstrate that this defect-enriched PNP can indeed exhibit significantly higher photothermal performance than the normal counterpart in cells and mouse tumors, which confirms the validity of the presented strategy in typical practical applications. This work provides a strategy to intrinsically and significantly enhance plasmonic photothermal conversion of PNPs with a sufficiently large size, which is not only suitable for PNPs with the morphology and composition required for specific applications but also can be combined with existing strategies to further increase their photothermal performance.