Application of bimetallic gold–platinum nanoparticles in optical fiber sensors for pesticide detection

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.