A Flexible Broadband Visible Light Plasmon‐Absorber Based on a 2D Monolayer of Au‐Nanoparticle/TiO₂‐Nanowire Core–Shell Heterostructures

Abstract Plasmon‐induced hot carrier transfer is a promising approach for photoelectric applications, but its practical application is often hindered by its relatively narrow absorption bandwidth and low light harvesting at visible wavelengths. This work reports a broadband visible light plasmon‐absorber based on a dandelion‐like hierarchical metal‐semiconductor Au‐TiO₂ core–shell nanostructure where each Au nanoparticle (AuNP) core is covered by an optically transparent mesh‐shell composed of TiO₂ nanowires (TNWs) (denoted as AuTNW‐dCS). These AuTNW‐dCSs are assembled to form a 2D arrayed plasmonic monolayer by connecting adjacent AuNPs with cross‐linked TiO₂ NWs, which can induce a remarkable broadband absorption in the visible spectrum of 500–700 nm. Driven by a wide light adsorption range, improved hot‐electron carriers, and excellent analyst's immobilization capability, the AuTNW‐dCS based photoelectric immunosensor owns excellent performance for alpha‐fetoprotein detection in human serum, with a practical linear range of 0.1–1000 ng mL⁻¹, a low detection limit of 0.1 ng mL⁻¹, and satisfying selectivity under visible light‐emitting diode light irradiation. This work enlightens the prospective research on the use of metal/semiconductor core–shell heterostructures as photoactive materials for sensing applications. Additionally, it gives an impetus for developing flexible nanofilms based on plasmonic metal/semiconductor nanohybrids, beneficial for building wearable point‐of‐need platform.