A functional Au array SERS chip for the fast inspection of pesticides in conjunction with surface extraction and coordination transferring

Rapid field trace detection of pesticide residue in food based on surface-enhanced Raman spectroscopy

Surface-enhanced Raman spectroscopy is an alternative detection tool for monitoring food security. However, there is still a lack of a conclusion of SERS detection with respect to pesticides and real sample analysis, and the summary of intelligent algorithms in SERS is also a blank. In this review, a comprehensive report of pesticides detection using SERS technology is given. The SERS detection characteristics of different types of pesticides and the influence of substrate on inspection are discussed and compared by the typical ways of classification. The key points, including the progress in real sample analysis and Raman data processing methods with intelligent algorithm, are highlighted. Lastly, major challenges and future research trends of SERS analysis of pesticide residue are also addressed. SERS has been proven to be a powerful technique for rapid test of residue pesticides in complex food matrices, but there still is a tremendous development space for future research.

A hydrophilic-hydrophobic graphitic carbon nitride@silver hybrid substrate for recyclable surface-enhanced Raman scattering-based detection without the coffee-ring effect

There is growing interest in developing a multifunctional surface-enhanced Raman scattering (SERS) substrate to deal with the challenge in the pretreatment-free detection and degradation of hazardous organic pollutants in water. Herein, a hydrophilic-hydrophobic graphitic carbon nitride@silver (g-C₃N₄@Ag) hybrid substrate was exploited as a potential candidate for the recyclable detection of dye molecules. Such a sophisticated substrate not only showed a significant SERS activity with a high enhancement factor of 3.21 × 10⁶ triggered by the significantly aggregated Ag nanoparticles, but also possessed an outstanding self-cleaning property via visible-light irradiation. Furthermore, the effective weakening of the coffee-ring effect was also facilitated by the hydrophilic-hydrophobic structure, resulting in excellent uniformity and reproducibility. Ultimately, the applicability of the developed recyclable SERS substrate in the monitoring of trace malachite green was demonstrated. It is expected that the innovative SERS substrate has great potential for application in highly sensitive, stable, and recyclable on-site analysis, especially for organic pollutant treatment and environmental protection.

Nylon membranes modified by gold nanoparticles as surface-enhanced Raman spectroscopy substrates for several pesticides detection

Surface enhanced Raman spectroscopy (SERS) is an attractive means for trace compound detection because of its high sensitivity, however, the poor reproducibility is a major challenge. Herein, we propose a facile SERS strategy employing the several developed test processes to improve the repeatability of the SERS analysis based on regular nylon membranes as substrates to detect trace compounds. Various methods, including in situ reduction, immersion adsorption, and filtration, were first compared to prepare composite substrates using nylon membranes and gold nanoparticles. The substrates prepared by filtration showed the best test parallelism (RSD = 7.85%). Its limit of detection (LOD) could reach 10^-8 g mL^-1 with a good linear relationship in the range 10^-8 to 10^-7 g mL^-1. Finally, three pesticide solutions were tested to verify the substrate applicability. A superior LOD of 10^-8 g mL^-1 was observed for thiram, whereas the LODs of both phorate and benthiocarb could reach 10^-6 g mL^-1. Overall, modifying nylon membrane substrates with gold nanoparticles improves the repeatability and economic viability of SERS and favors its wider commercial application for detecting trace compounds.

Electrochemical detection of organophosphorus pesticides based on amino acids-conjugated P3TAA-modified electrodes

In this work, amino acids (AAs) including serine (S), histidine (H) and glutamic acid (E)-conjugated poly(3-thiophene acetate acid) (P3TAA) were synthesized to promote the catalytic hydrolysis and in situ electrochemical detection of organophosphorus pesticides (OPs). The hydrolysis of OPs followed the mechanism of proton transfer relay composed of AAs of S, H, E, called the "catalytic triad", found in biomimetic hydrolases. P3TAA was used as a carrier to attach S, H, E, and these AA sites have the hydrolysis activity of Ops; the polymer P3TAA-AAs behaved like biomimetic enzymes. After the hydrolysis of OPs (e.g., methyl paraoxon, ethyl paraoxon and methyl parathion), p-nitrophenol (PNP) was generated, which can be detected electrochemically. Herein, an electrochemical method using P3TAA-conjugated S, H, E-modified electrodes for the determination of OPs was developed. OPs can be quantified by the electrochemical responses of PNP. This technique was selective toward OPs with the p-nitrophenol group. The detection limit of OPs (methyl paraoxon, methyl parathion and ethyl paraoxon) reached 0.5 μM. This detection technique was successfully applied to the detection of OPs in real samples with high detection accuracy.