“Integrated Stacked” Design “Nanobullet” for High Photothermal Conversion in Dual-Mode Lateral Flow Immunoassay

Salmonella enterica serovar typhimurium (S. typhimurium), a prevalent foodborne bacterium, necessitates creating sensitive and rapid detection methods for food safety, with lateral flow immunoassays (LFIAs) using nanomaterials as signal tracers being particularly effective. Enhancements in performance and sensitivity are not restricted to the material alone, we propose an "integrated stacked" concept, which combines amorphous active sites, hollow morphology for enhanced reflection, and symmetric structure for strong absorption resonance. This approach leads to significant photothermal enhancement (η = 60.66%) and is supported by finite element analysis (|E|_max² = 3100). A hollow "nanobullet" (RuTe₂) was created, featuring a vivid colorimetric signal enhancing the detection range, a large specific surface area (≈6:1) for improved antibody binding, and excellent photothermal properties facilitating dual-mode transduction. After 5 min of binding, the detection limits of RuTe₂-LFIA for S. typhimurium after 12 min were 2398.83 cfu mL^-1 (colorimetric) and 977.23 cfu mL^-1 (photothermal), which were 36.14 and 88.72 times lower than the values of AuNPs-LFIA (86696.19 cfu mL^-1). The superior performance of RuTe₂-LFIA suggests potential advancements in photothermal materials for point-of-care testing.