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BACKGROUND: Surface‐enhanced Raman scattering (SERS) substrates based on metallic nanoparticles locked in some flexible materials have great potential for rapid detection of pesticide residues in foods, but these substrates are generally not reusable. RESULTS: A bendable and reusable sponge based on polydimethylsiloxane (PDMS) and Au nanospheres was synthesized and employed as SERS substrate to analyze thiram on the surfaces of apples and grapes (20–1000 ng cm−2) and in their juices (0.5–5.0 mg L−1) with minimum sample pretreatments. The lowest detectible concentrations for thiram in fruit juices and on fruit skins were 0.5 mg L−1 and 20 ng cm−2, respectively. The Au‐PDMS substrate had acceptable intra‐reproducibility for SERS analysis of thiram in fruit juices and on fruit skins, resulting in 3.6–16.9% relative standard deviation (RSD) for the SERS signal of the primary peak of thiram. Moreover, the Au‐PDMS substrate exhibited distinguished reusability and stability, which could provide a reproducible SERS signal of thiram in apple juice even after the substrate being reused ten times (RSDs for the three major characteristic peaks of thiram were 2.7–10.5% during the ten reused cycles). CONCLUSION: This flexible and reusable Au‐PDMS SERS substrate for thiram detection could be readily extended to the analysis of other trace chemicals in a broad range of foods, providing a new possibility for SERS application. © 2022 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

With the large-scale use of pesticides, food safety issues caused by their residues have been drawn increasing concern. In this study, surface-enhanced Raman spectroscopy (SERS) coupled with a Au@Ag nanoparticle (NP)-graphene oxide (GO) composite substrate which was synthesized by a simple self-assembly method was applied for the rapid determination of thiram residues in fruit juice. To obtain high SERS activity, the loading and the aggregation of Au@Ag NP on the graphene oxide sheets were adjusted by controlling the size of Au@Ag nanoparticle and the concentration of graphene oxide in solution. Using the optimal conditions, the limit of detection for thiram standard solution was 6.3 ng/mL, while the limits of detection for thiram in apple juice and grape juice without any pretreatment were 36.7 and 134.4 ng/mL, respectively. The entire analytical process required less than 20 min. The results indicated that SERS technology coupled with Au@Ag nanoparticle graphene oxide composite substrate was a simple, rapid, and sensitive approach for the determination of pesticide residues in fruit juice. [ABSTRACT FROM AUTHOR]

Surface‐enhanced Raman spectroscopy (SERS) provides a potential solution for rapid analysis of trace compounds such as residual pesticides, naturally occurred toxicants, banned or restricted drugs, and food additives in complex food matrices. In this review, the basic principles of SERS and general approaches to successfully apply SERS in food analysis are covered from an applications perspective. The key steps including substrate selection and evaluation, sample preparation and simplification, spectral collection, and data analysis during the development of SERS methods for food analysis are summarized, together with the discussion of typical underlying technical barriers or major challenges of these methods and their applications. Future directions in successfully applying SERS technology as a routine analytical approach to solve real‐world food problems are analyzed. This comprehensive review summarizes the recent progress on theory, application, and scope of SERS for food analysis, providing a basic understanding of the technology; more importantly, key methodology, potential pitfalls, and possible solutions during the development of rapid SERS methods based on authors' years of SERS experience are shared with researchers in the field. [ABSTRACT FROM AUTHOR]

Residual pesticides in vegetables or fruits have been become one of the world's most concerned food safety issues. Au-Ag core-shell nanoparticles (Au@Ag NPs) coupled with surface-enhanced Raman spectroscopy (SERS) was used for analysis of flusilazole which was widely applied in pears. Three different diameters of Au@Ag NPs were prepared to select the best SERS substrate for analyzing flusilazole. The Au@Ag NPs sizes of 90 ± 7 nm showed the highest enhancement effect and could be detected flusilazole standard solution and the minimum detectable concentration was 0.1 mg/L. Flusilazole in pear could also identified at as low as 0.1 μg/g. The amount of adsorbent is critical in the sample preparation process and the best amount of each absorber dosage was 0.6 g MgSO4, 0.2 g C18 and 0.2 g primary secondary amine (PSA). The experimental results indicated a good linear relationship between the Raman intensities of chief peaks and the concentrations of flusilazole solutions (R2 = 0.924-0.962). This study shows that Au@Ag as SERS substrate has great potential to analyze of flusilazole in food matrices. [ABSTRACT FROM AUTHOR]

Residual pesticides in fruits and vegetables are one of the major food safety concerns around the world. Surface-enhanced Raman spectroscopy (SERS) coupled with chemometric methods was applied for quantitative analysis of trace levels of carbaryl pesticide in apple. The lowest detectable level for carbaryl in apple was 0.5 μg g −1 , which was sensitive enough for identifying apple contaminated with carbaryl above the maximum residue level. Quantification of carbaryl residues (0–10 μg g −1 ) was conducted using partial least squares regression (PLSR) and support vector regression (SVR) models. Based upon the results of leave-one-out cross-validation, carbaryl levels in apples could be predicted by PLSR ( R 2 = 0.983) or SVR ( R 2 = 0.986) with a low root mean square errors (RMSE = 0.48 μg g −1 or 0.44 μg g −1 ) and a high ratio of performance to deviation (RPD = 7.71 or 8.11) value. This study indicates that SERS has the potential to quantify carbaryl pesticide in complex food matrices reliably. [ABSTRACT FROM AUTHOR]

Abstract: Residual pesticides such as phosmet in fruits and vegetables are one of the major food safety concerns for consumers around the world. Surface-enhanced Raman spectroscopy (SERS) with gold-coated substrates was exploited to analyze phosmet (0.5–10 μg/g) in apples. Phosmet could be detected from its SESR spectra at as low as 1 μg/mL in standard solution and 1 μg/g in apple extracts. The calculated limit of detection for phosmet in standard solution and in apple extracts were 1.01 μg/mL and 1.44 μg/g, respectively. There were linear relationships between the concentrations of phosmet solutions and the Raman intensities of four major characteristic peaks, with the coefficient of determination (R 2) ranging from 0.905 to 0.984, the root mean square error of prediction (RMSEP) ranging from 0.46 to 1.16 μg/mL, and the ratio performance deviation (RPD) from 3.22 to 8.21. Although the linear regression results for phosmet in apple extracts with Raman intensities were not as good as those for the standard solutions (R 2 = 0.866–0.945, RMSEP = 0.84–1.38 μg/g, RPD = 2.65–4.33, which still showed great potential of using SERS for quantitative analysis. The presence of non-targeted compounds in apple extracts affected the sensitivity for qualitative analysis and accuracy for quantitative analysis. This study demonstrated that SERS coupled with gold nanosubstrates could be used for analysis of trace contaminants like phosmet in complex food matrices. [Copyright &y& Elsevier]

Twelve different Au nanoparticles (NPs; diameter, 19–87 nm) and Au–Ag core-shell NPs (diameters of core and particles: 19 nm, 35–91 nm; 43 nm, 66–127 nm) varying in size and the ratio of gold to silver were employed as surface enhanced Raman scattering (SERS) substrates for rapid analysis of herbicide diquat cation in apple juice. The minimum detectible concentrations for diquat cation standards with three selected optimal SERS substrates were 0.005 mg/L (43 nm Au NPs), 0.05 mg/L (91 nm Au–Ag NPs, 19 nm core), and 0.025 mg/L (78 nm Au–Ag NPs, 43 nm core), respectively. However, only the 78 nm Au–Ag NPs led to acceptable SERS enhancement effect for diquat cation in apple juice with minimum sample preparation, allowing its detection at as low as 0.025 mg/L. In addition to providing a rapid analysis approach for diquat in fruit juices, this study indicates that the influences of particle size and composition of NPs on SERS enhancement effects for an analyte in standard solutions could be quite different from that in a real food sample, while the optimal ratio of gold to silver of the bimetallic NPs depended on the Au seeds and sample matrix. • Twelve Au and Au@Ag nanoparticles (NPs) were used for SERS detection of diquat. • As low as 5 ppb of diquat in standards was detected with Au NPs (dia. 43 nm). • Au@Ag NPs (dia. 78 nm, core 43 nm) worked the best for diquat in apple juice. • Diquat in apple juice with minimum sample preparation was detected at 25 ppb. • SERS effects for diquat in foods may not be consistent with that in standards. [ABSTRACT FROM AUTHOR]

Residual pesticides in agricultural produce pose a threat to wildlife and domestic animals, and are one of the major food safety concerns around the world. Surface-enhanced Raman spectroscopy (SERS) coupled with gold nanoparticles was applied for rapid analysis of phosmet and thiabendazole, two widely used pesticides in apples. Four different diameters of nanoparticles were fabricated to select the optimal SERS substrate for analyzing each pesticide. A simple sample preparation method allowed for extracting the pesticides from apples within 20 min. The minimum detectable concentration was 0.5 μg/g for phosmet and 0.1 μg/g for thiabendazole in apples. Partial least squares regression (PLSR) models were also developed to correlate SERS spectra of apple extracts with the concentrations of each pesticide in apple for quantitative analysis purpose. The coefficient of determination ( R 2 cv ) of actual values versus values predicted with PLSR models was 0.936 for phosmet and 0.959 for thiabendazole in apples. This study provides a new, rapid and sensitive approach for analysis of trace amounts of residual pesticides in apples based on SERS coupled with gold nanoparticles, which has great potential for analysis of other trace contaminants. [ABSTRACT FROM AUTHOR]

• Spherical and monodispersed AgNPs were synthesized for SERS measurement. • SERS based on AgNPs generated strong enhancement of Raman signals. • Detection limit of phosmet in Tieguanyin Oolong tea was 0.1 mg/kg. • SERS based on AgNPs is a novel tool for detecting phosmet in Oolong tea. There have been increasing concerns among consumers about pesticide residues in Oolong tea. This study aimed to establish surface-enhanced Raman scattering (SERS) method for rapid measurement of chemical contaminants in Oolong tea. Synthesis of SERS substrate was achieved by synthesizing silver nanoparticles (AgNPs) via a reduction method. AgNPs were spherical and highly monodispersed, which created remarkable electromagnetic fields during SERS activities to measure phosmet in the methanol-water solution and Oolong tea. Partial least squares regression models were established to predict the concentrations of phosmet in the methanol-water solution (r = 0.934; slope = 0.880; RMSEP = 1.001 mg/L) and Oolong tea samples (r = 0.927; slope = 0.938; RMSEP = 1.157 mg/kg) with the detection limit of 0.1 mg/kg. The results indicate that SERS coupled with silver nanoparticles is a fast, sensitive, and reliable method for detection and characterization of pesticide contaminants in Oolong tea products. [ABSTRACT FROM AUTHOR]