A Polymer-Integrated Flexible Gold Nanotriangle Array for Quantitative and Nondestructive SERS Detection of Thiram on Apples

Abstract

To enable rapid in situ detection of pesticide residues on foods with non-planar surfaces, a polymer-integrated flexible surface-enhanced Raman scattering (SERS) substrate was constructed and demonstrated using apples as a model. An ordered gold nanotriangle (AuNT) array was integrated onto a biaxially oriented polypropylene (BOPP) film to provide conformal interfacial adaptation, while a polyethylene terephthalate (PET) overlayer was introduced as a protective barrier to suppress environmental degradation and maintain hotspot integrity during storage and deformation. The densely packed AuNTs generated strong electromagnetic enhancement, yielding an analytical enhancement factor of 3.72×108 with good signal uniformity (RSD<7%). More than 90% of the initial SERS activity was retained after 30 days, and over 80% was maintained under repeated mechanical deformation. The flexible substrate enabled direct and nondestructive detection of thiram on apple surfaces, achieving a limit of detection of 0.074 μg/L and a linear range spanning four orders of magnitude (R2=0.9865). Recoveries of 89.5-103.1% were obtained in spiked samples. These results indicate that the polymer-integrated flexible SERS platform provides a mechanically robust and storage-stable approach for practical analysis of contaminants on irregular food surfaces.