Plasmonic magnetic nanoparticle-based photothermal sensor for sensitive detection of chlorantraniliprole

The development of a sensitive lateral flow immunoassay (LFIA) for the quantitative detection of pesticide residues is crucial. Herein, a magnetically assisted, sensitive LFIA platform was developed using magnetic branched nanoparticles (MBNPs). MBNPs comprised a superparamagnetic iron oxide (Fe₃O₄) core and branched plasmonic gold (Au) shell. The core enabled rapid magnetic separation under an external field, while the shell exhibited strong surface plasmon resonance absorption. The MBNPs exhibited a high molar extinction coefficient of 11.41 × 10¹⁰ M^-1 cm^-1 and photothermal conversion efficiency of 48.37%. When MBNPs applied to the LFIA platform, the MBNPs-LFIA enabled the sensitive detection of chlorantraniliprole in lettuce and grape within 25 min with a limit of detection of 0.016 ng mL^-1, representing an 11.28-fold improvement over AuNPs-LFIA. This study demonstrates that MBNPs-LFIA enables high-performance sensing, offering a promising platform for future point-of-care testing applications.