Flatband λ-Ti₃O₅ Nanoparticles Unlocking Near-Unity Solar Absorptivity for Ultrarobust Photothermal Antibiofouling

Light-assisted antibiofouling represents a promising approach to combat pervasive microbial contamination owing to exceptional antibacterial efficiency without inducing drug resistance. However, existing photothermal platforms suffer from inefficient solar energy harvesting and weak visible-light responsiveness, even after extensive bandgap engineering. Herein, we report metallic λ-Ti₃O₅ nanoparticles as a new photothermal antibiofouling paradigm by leveraging a flat-band electronic structure with a markedly enhanced joint density of states. A supramolecular-nanoscaffold-guided strategy is developed to overcome the longstanding challenge of synthesizing high-purity, phase-stable λ-Ti₃O₅ with well-defined nanoscale architectures. Relative to conventional microsized counterparts, λ-Ti₃O₅ nanoparticles exhibit near-perfect solar absorptivity (∼100%) and outstanding photothermal conversion efficiency (∼8% increase), governed by Ti-Ti dimer-induced flat bands near the Fermi level in combination with pronounced nanoscale confinement effects. This ultrarobust and recyclable nanoformulation delivers broad-spectrum photothermal bactericidal activity and efficient disruption of biofilms. All-atom simulations reveal synergistic antibiofouling modes, including enhanced electrostatic adhesion to bacterial surfaces, intense photoinduced reactive oxygen species generation, and localized thermal effects, collectively increasing the fluidity and inhomogeneity of bacterial membranes. This work provides a distinctive perspective on the crucial role of Ti-Ti dimer-induced flat bands in boosting photothermal antimicrobial activity and pioneers a rational framework for designing next-generation photoresponsive nanomaterials for diverse biointerface applications.