Laser‐Synthesized Carbon‐Coated Elemental Bismuth Nanoparticles for Sustained Reactive Oxygen Species Generation Under Visible‐Light Irradiation

ABSTRACT

Owing to its visible light‐responsive electronic properties, redox activity, and potential biocompatibility, elemental bismuth is a promising candidate for photodynamic and chemodynamic therapies primarily via reactive oxygen species generation. However, accelerated surface oxidation of zero‐valent bismuth suppresses photoinduced charge transfer, limiting its practical application. Here we introduce metallic bismuth core‐shell nanoparticles produced by femtosecond laser ablation in acetone, featuring a crystalline Bi° core encapsulated within a conformal amorphous carbon shell (∼5 nm thick), proved via TEM. XPS with depth profiling confirms that metallic bismuth dominates the nanoparticles’ composition, with oxygen‐containing species confined to a thin, buried interfacial region. Optical absorption measurements show a broadband response across the visible range, with no oxide‐associated features. Under visible irradiation, these nanoparticles exhibit sustained photoinduced redox activity, leading to the formation of hydroxyl radicals, quantified using a coumarin fluorescence assay. Methylene blue degradation is used as a model reaction to investigate charge transfer pathways and wavelength dependence, supporting a dye‐sensitization‐assisted mechanism mediated by the Bi ⁰ surface. Repeated irradiation cycles preserve photoactivity, consistent with resistance to chemical deactivation under the tested conditions. The demonstrated design provides a basis for controlled redox activity relevant to photo‐assisted therapeutic approaches and related biomedical technologies.