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

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.