"Plasmonic aggregates" scatted in the nano-heterogeneous gold species driven highly photothermal sensitive immunosensing for Salmonella typhimurium.

Efficient signal response and antibody coupling efficiency performance are valid strategies to enhance analytical performance while reducing antibody consumption. Herein, the CuO shell is used to gather gold nanoparticles around the plasmonic gold nanobipyramid (ACANPs) to form "plasmonic aggregates" to enhance the dual-responsive lateral flow immunoassay for detecting Salmonella typhimurium (S. typhimurium). Because the densely clustered gold nanoparticles (AuNPs) around ACANPs exhibit stronger plasmon resonance properties, providing more intensive localized surface plasmon resonance (|E| = 3.9 × 10), one order of magnitude stronger than of gold nanobipyramids (AuNBPs) (|E| = 189) thus forming "plasmonic aggregates". The results of the photothermal experiment are consistent with the finite element simulation results, confirming that the plasma resonance and elemental matching formed by a large number of AuNPs enable the photothermal conversion efficiency as high as 59.96 %. Moreover, the high antibody coupling efficiency of 94.83 % (at 25 μg mL) and photothermal signal response demonstrate the feasibility of enhancing sensitivity detection for S. typhimurium. The established ACANPs-LFIA has a lower detection limit, reaching 10 cfu mL in the colorimetric and photothermal format, which is 50 times higher in sensitivity than the traditional colloidal gold method. Hence, ACANPs serve as efficient colorimetric and photothermal signal labels for specific immune recognition, rapidly generating actionable results, facilitating early detection of food contamination risks, and supporting on-site decision-making processes.