Development of Wearable MXene/Ag Nanopopcorn-Decorated Finger Caps for Rapid On-Site SERS Detection of Fipronil in Food and Water Samples

Pesticide residues in vegetables pose serious human health risks, thereby underscoring the need for developing rapid, cost-effective, sensitive, and nondestructive analysis methods for on-site pesticide detection. Here, we report a wearable adhesive SERS-active finger cap created by decorating silver nanopopcorns (AgNPCs) and molybdenum carbide (Mo2C) nanoparticles on flexible aluminum tape (AT) to constitute the hybrid AgNPCs/Mo2C@AT SERS platform for reliable detection of the toxic pesticide fipronil (FP). The synergistic electromagnetic and chemical enhancements of the AgNPCs/Mo2C composite greatly amplify SERS signals, while strong adhesion and flexibility ensure robust nanoparticle retention and efficient analyte collection from irregular surfaces, The AgNPCs/Mo2C@AT SERS finger cap demonstrates a broad detection range from 10–10 to 10–4 M with an enhancement factor of 1.90 × 109 and an ultralow limit of detection of 1.16 × 10–10 M, which is far below the regulatory thresholds set by the European Union and China. Besides, it exhibits superior signal uniformity (RSD = 8.81%), good reproducibility (RSD = 8.01%), and excellent storage stability, which can retain 70% of its original SERS activity after 14 days. Its flexibility allows for its intimate contact with curved surfaces to enable efficient FP residue detection on tomatoes and chilies using a simple “paste, press, and peel” method. Overall, the proposed wearable SERS finger cap represents a low-cost, user-friendly, amd highly sensitive SERS platform for real-time on-site pesticide detection with broad applications in food safety and environmental monitoring.