Plasmonic Detection of Pesticide Residues on Syzygium aqueum Using Cu-Modified Gold Nanobipyramids

Abstract

Pesticide residues in agricultural products have become a critical global food safety concern due to their potential risks to human health and environmental sustainability. Although conventional analytical techniques, such as gas chromatography and high-performance liquid chromatography, provide high sensitivity and selectivity, their complex procedures, expensive instrumentation, and limited applicability for rapid field monitoring have encouraged the development of alternative sensing technologies. This study aims to develop and evaluate copper-modified gold nanobipyramids (Cu-GNBPs) as a plasmonic sensor for detecting pesticide residues in Syzygium aqueum through localized surface plasmon resonance (LSPR) mechanisms. The research employed an experimental approach involving the synthesis of gold nanobipyramids and Cu-GNBPs using a seed-mediated growth method, followed by the characterization of their optical, structural, and morphological properties using UV–Vis spectroscopy, X-ray diffraction (XRD), and field emission scanning electron microscopy (FESEM). The sensing performance was evaluated based on sensitivity, reproducibility, and stability using pesticide residue samples extracted from Syzygium aqueum. The results demonstrated that copper modification enhanced the LSPR response, improved signal stability, and increased sensing reliability compared with pristine gold nanobipyramids. The developed Cu-GNBP sensor exhibited a strong linear correlation between the absorbance response and pesticide concentration, with an R² value of 0.982, a limit of detection (LOD) of 0.75 ppm, and a limit of quantification (LOQ) of 2.50 ppm. The sensor also demonstrated consistent performance in complex fruit matrices, confirming its practical potential for food safety monitoring. This study concludes that Cu-GNBPs provide an effective and promising nanoplasmonic platform for rapid pesticide residue detection and support the future development of portable food safety monitoring systems.