Dual‐Wavelength Photosensitizer Based on Phthalocyanine Nanodots for Multifunctional Composites with Enhanced Photodynamic Antibacterial, Photothermal Performance, and UV Protection

Abstract Designing efficient near‐infrared photosensitive molecules and excellent photosensitive materials is a major challenge in the fields of photodynamic antibacterial and photothermal energy conversion. The Förster resonance energy transfer shows much promise for enhancing the photodynamic antibacterial property and photothermal performance. Herein, a novel water‐soluble dual‐band enhanced naphthylimide functionalized phthalocyanine photosensitizer is designed and synthesized. The designed dual‐band enhanced photosensitizer, 2,9(10),16(17),23(24)‐Tetrakis[N‐Benzyl‐N,N'‐dimethyl‐1‐propanaminium‐4‐(N‐hydroxyethyl)‐1,8‐naphthylimino] phthalocyanine Zinc(II) (NAPc‐N), can self‐assemble by the π–π stacking interactions to form nanodots with a size of ≈40–50 nm. Nanodot composites prepared using waterborne polyurethane (WPU), exhibit dual‐wavelength photodynamic antibacterial at 440 and 680 nm irradiations, efficiently photothermal conversion, and excellent UV protection (UPF) performances. The produced singlet oxygen amount by NAPc‐N shows tremendous enhancement in dual‐wavelength irradiations. After 30 min under the blue and infrared lights, the antibacterial rate of NAPc‐N against Staphylococcus aureus and Escherichia coli reaches 99.99%. The temperature of the NAPc‐N composite can be heated up to 60 °C and the UPF value can be up to 128.23. These dual‐wavelength enhanced photosensitizer nanodots hold significant potential for advanced photodynamic materials and biomaterials applications.