Ultra-sensitive, on-site pesticide detection for environmental and food safety monitoring using flexible cellulose nano fiber/Au nanorod@Ag SERS sensor

This paper introduces a highly absorbent and sensitive cellulose nanofiber (CNF)/gold nanorod (GNR)@Ag surface-enhanced Raman scattering (SERS) sensor, fabricated using the vacuum filtration method. By optimizing the Ag thickness in the GNR@Ag core-shell structures and integrating them with CNFs, optimal SERS hotspots were identified using the Raman probe molecule 4-aminothiophenol (4-ATP). To concentrate pesticides extracted from fruit and vegetable surfaces, we utilized the evaporation enrichment effect using hydrophilic CNF and hole-punched hydrophobic polydimethylsiloxane (PDMS). This design leverages the hydrophilic substrate and localized evaporation to create a microfluidic flow that concentrates analytes within a small hole area, enhancing SERS sensitivity by up to 465 %. The sensor achieved on-site detection limits for Thiram as low as 10^-11 M on fruit surfaces, specifically apples and chili peppers. This approach underscores how localized molecule enrichment can substantially improve field-based pesticide analysis. the sensor's response to interfering substances (e.g., glucose and citric acid) and other harmful molecules (e.g., carbendazim and nitrofurazone was also evaluated, demonstrating high sensitivity and accuracy). The PDMS-assisted CNF/GNR@Ag SERS sensor exhibits flexibility, ease of fabrication, and excellent sensitivity and selectivity, showing significant potential for applications in food safety, agriculture, and environmental monitoring. These advancements are anticipated to promote the practical adoption of SERS-based sensor technology across diverse fields, suggesting broad future utility.