Unveiling the Excited‐State Dynamics and Interfacial Interactions in Dye‐Sensitized NaNdF₄ Nanoparticles for Efficient Photothermal Effect

Near-infrared (NIR) dyes can overcome the weak absorption of lanthanide nanoparticles (NPs) by antenna sensitization, offering new avenues to develop efficient and versatile lanthanide nanomaterials. However, current research on dye-sensitized lanthanide NPs for photothermal conversion is still preliminary, and the involved excited-state dynamics and interfacial interactions remain elusive. Herein, steady-state/transient absorption spectroscopy and theoretical calculation are used to investigate the coordination and aggregation states of cypate dyes on NaNdF₄ NPs, revealing the influence of interfacial interactions on resonant energy transfer. Synergetic heat-generation mechanism of lanthanide cross-relaxation and dye intermolecular collisions is further proposed. The photothermal conversion efficiency of cypate-NaNdF₄ nanocomposites reaches 50.4%, outperforming those of typical photothermal materials with high NIR absorption. Moreover, the intersystem crossing of cypate can be inhibited due to the depopulation of the S₁ exciton via ET, thereby improving anti-photobleaching ability. These dye-sensitized NaNdF₄ nanocomposites exhibit superior photothermal effect, stability and NIR-II luminescence, showing great potential in theranostic applications.