"Plasmonic Blackbody" with Broadband Absorption Facilitates Efficient Colorimetric/Fluorescence Dual-Response for Sensitive Bimodal-Type Immunochromatography.

While exploring the physicochemical properties of plasmonic metal nanoparticles provides fascinating optical properties, current research typically ignores the ever-increasing point-of-care (POC) demands with target-dependent dual-response variation and built-in self-calibration function. Herein, we propose utilizing the distinct difference in reduction potential between Au3+/Au0 (1.00 eV) and Pt4+/Pt0 (1.44 eV) for preparing complex 3D highly branched nanostructure as "plasmonic blackbody" with broadband absorption to facilitate efficient colorimetric-fluorescence bimodal-type immunochromatography (ICA). Availing the mesoporous Au@Pt (mAPt) induced minimal scattering section, pronounced broadband absorption with dual-spectral overlap contributed to ∼12.90-fold fluorescence quenching enhancement. Meanwhile, "plasmonic blackbody" spanning the visible region (380-780 nm)-mediated higher contrast combined with larger surface area-induced abundant antibody binding sites resulted in ∼3.125-fold colorimetric response enhancement. By employing ractopamine (RAC) as the model target, this "plasmonic blackbody"-driven colorimetric/fluorescence dual-response platform integrating intensified immuno-recognition demonstrated 0.079 ng mL-1 detection sensitivity in ICA system (∼14.95-fold than classical colloidal gold method). This work showcases the superiority of exploiting physicochemical properties to enhance analytical performance and expands the application scenarios of plasmonic metal nanoparticles.