SERS/ratio-colorimetric/smartphone triple-mode sensing LFIA based on mesoporous silica nanospheres for precise on-site detection of chlorothalonil.

We developed a novel triple-mode lateral flow immunoassay platform for rapid chlorothalonil detection. The platform integrates surface-enhanced Raman scattering, ratiometric colorimetry, and smartphone readout. It utilizes a hierarchically structured mesoporous silica nanosphere loaded with SERS-active Ag@Au nanoparticles and magnetic Fe3O4 nanoparticles for target enrichment and signal amplification. The test strip shows concentration-dependent color transitions (red→purple→blue) using competitive immunoassay with Prussian blue nanoparticles for visual/smartphone analysis and strong SERS signals. The platform achieves ultra-sensitive detection (LODs: 0.0007 ng mL-1 for SERS; 0.005 ng mL-1 for smartphone colorimetry), a broad dynamic range (0.0007-864 ng mL-1), excellent specificity, and accurate recoveries (80.6-110.6%) in spiked produce, validated by HPLC. This work offers a reliable, high-performance sensing strategy for advanced pesticide monitoring.