Fiber Optic SERS Sensor with Silver Nanocubes Attached Based on Evanescent Wave for Detecting Pesticide Residues

Abstract

Surface-enhanced Raman scattering (SERS) has great potential in the field of rapid detection of pesticide residues in food. In this paper, a fiber optic SERS sensor excited by evanescent waves was proposed for efficient detection of thiram. Silver nanocubes (Ag NCs) were prepared as SERS active substrates, which had much stronger electromagnetic field intensity than nanospheres under laser excitation due to much more "hot spots". By using the method of electrostatic adsorption and laser induction, Ag NCs were uniformly assembled at the fiber taper waist (FTW) for enhancing the Raman signal. Different from the traditional way of stimulation, evanescent wave excitation greatly increased the interaction area between the excitation and analyte, while reducing the damage of the excited light to the metal nanostructures. The methods proposed in this work have been successfully used to detect the pesticide residues of thiram and showed good detection performance. The detection limits for 4-Mercaptobenzoic acid (4-MBA) and thiram were determined to be 10 −9 and 10 −8 M, the corresponding enhancement factor could be 1.64 × 10 5 and 6.38 × 10 4 . Low concentration of thiram was detected in the peels of tomatoes and cucumbers, indicating its feasibility in actual sample detection. The combination of evanescent waves and SERS provides a new direction for the application of SERS sensors, which had great application potential in the field of pesticide residue detection.

A Comprehensive Numerical Study on Fiber Optic SERS Probe Design

“…While an array of optical fiber structures has been employed for SERS probes in previous studies, ,− we chose to work with a flat-cleaved fiber structure. Although other structures, including the tapered fiber, have demonstrated enhanced SERS signal intensity due to their extended SERS active area, the SERS probes on the fiber end facets offer the advantage of high spatial resolution.…”

Seeing is believing: what is on the surface of silver nanocrystals suspended in their original reaction solution

“…Inorganic nanocrystals synthesized using colloidal methods have found widespread use in a broad range of applications. As a notable example, Ag nanocubes have been extensively studied owing to their fascinating properties related to localized surface plasmon resonance (LSPR) and surface-enhanced Raman scattering (SERS), [1][2][3][4][5][6][7][8] as well as their applications as an antimicrobial agent 9,10 and a catalyst toward the epoxidation reaction. 11,12 Many colloidal methods have been developed for the synthesis of Ag nanocubes with uniform and controllable sizes, with the most successful ones built around polyol reduction.…”

Core–Satellite Nanoassemblies as SPR/SERS Dual-Mode Plasmonic Sensors for Sensitively Detecting Ractopamine in Complex Media

“…SERS is a powerful label-free analysis tool that provides unique molecular fingerprints with high sensitivity and speed, meeting the requirements of rapid detection in the field. In addition, due to its simple operation, no complicated sample pretreatment, and nondestructive characteristics, SERS has been widely used in the analytical fields of medicine, , biochemistry, − environment, and food safety. − Particularly, SERS combined with immunotechnology has been developed to detect clenbuterol and RAC through immobilizing antibodies on plasmonic substrates for capturing targets with high specificity. , Antibodies are expensive, require complex preparation, and are susceptible to external chemical modifications, which limit their application. Aptamers have a much smaller size and complexity, are easier to manufacture, are stable during storage and modification, and are relatively inexpensive.…”