Black Hole Quencher-Enhanced Plasmonic Photothermal Conversion

A common goal in the field of thermoplasmonics is to improve the photothermal conversion efficiency (PCE) of plasmonic nanostructures, yet it is highly challenging. We herein report a universal method to dramatically improve plasmonic photothermal conversion by add-on black hole quencher (BHQ) molecules. BHQs, nonfluorescent resonant molecules, are immobilized to matched metal nanostructures to afford the excited coupling plasmonic hybrids with charge/energy transfer upon laser irradiation. Photothermal efficacy test confirms that the PCE of the hybrids is much higher than that of the sum of single plasmon and BHQ alone, leading to enhanced plasmonic photothermal conversion by approximately three times. Moreover, the PCE of the hybrid nanoparticles exhibits a nonlinear response to the plasmon fields, a phenomenon that cannot be achieved by fluorophores. The comparative experiments suggest that the whole photothermal efficacy of this hybrid stems from plasmonic nanoparticles, BHQ itself, as well as the mutual charge/energy transfer interaction. We demonstrate the generalizability of the strategy on various plasmonic nanostructures with three absorption-matched BHQs. The resultant BHQ-plasmon hybrids with enhanced conversion as high as 69.1% in NIR-II, which allows for highly efficient hyperthermia ablation of cancer cells in vitro and deep-seated tumors in vivo.