Abstract
As chemical pesticides are widely applied to farming, rapid and ultrasensitive detection assays should be further designed for food safety and ecological health. Herein, we present a novel localized surface plasmon resonance (LSPR) optical fiber sensor using bimetallic Au@Pt core-shell nanoparticles for simultaneous detection of Quinalphos and Thiram. Four individual Au@Pt nanostructures (Au@Pt 1-4) were synthesized and a systematic change of the platinum precursor concentration was used to induce controlled evolution of the nanostructure from smooth shells to very dendritic assemblies. Detailed characterization via UV-Vis, FE-SEM, EDS, and HR-TEM revealed that the Au@Pt 3 sample, with a dendritic shell 12.5 nm thick, exhibited the optimal balance of specific surface area and plasmonic "hot spots". When integrated into a PDMS microfluidic channel, the Au@Pt 3-functionalized fiber sensor demonstrated high sensing performance. It could reach the ultralow detection limits (LOD) of 2.01 × 10(-14) M for Quinalphos and LOD of 1.37 × 10(-11) M for Thiram with a wide linear dynamic range. In addition, the sensor showed good reproducibility (RSD = 1.67%) and short-term stability (CV < 0.1%). These results also demonstrate the crucial influence of bimetallic morphology on LSPR activity and offer a promising platform for ultrasensitive pesticide detection.