Surface-enhanced Raman scattering (SERS), owing to its high sensitivity and rapid response, has been widely used in various fields. However, it is still a challenge to prepare SERS substrates with high stability and reproducibility. Metal–organic frameworks (MOFs), with excellent enrichment capacity and stability, provide a new material for high-performance SERS substrates. In this paper, we prepare a MIL-101­(Cr) film via a secondary growth method, and Ag+ is reduced to Ag NPs by UV irradiation and attach to the film to synthesize the Ag@MIL-101­(Cr) film SERS substrate. Then, we change the time of UV light illumination and the amount of silver nitrate in order to obtain the optimal substrate. The detection capability of this sample can be up to 10–11 M for 4-ATP, and the relative standard deviation (RSD) is only about 5%, which demonstrates that the substrate has excellent SERS effect and reproducibility. Finally, the prepared substrate has been applied for the determination of nitrofurantoin, with its detection capability up to 10–7 M. This work proposes a simple method to synthesize MOF-based film substrate with high SERS performance and uniformity and provides potential for the sensitive detection of chemical or antibiotic residue.

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.

Controllable synthesis of novel metal nanoparticles and effective capture of hotspots are of great significance for SERS (surface-enhanced Raman spectroscopy) detection. Therefore, in this paper, a green controllable synthesis method of gold nanoparticle was achieved via epigallocatechin gallate reduction. Different morphologies of gold nanoparticles were synthesized just by changing the solution pH values, and the growth kinetics of AuNPs (gold nanoparticles) were systematically studied. The synthetic AuNPs were put in a droplet to study dynamic variations of self-assembly SERS hotspots from the liquid sol state to the solid dry state. The addition of halogen ions in the droplet can controllably regulate the self-assembly three-dimensional hotspot model of gold nanoparticles in the evaporation process of a droplet, during which the most enhancement effect can be easily captured. The dynamically changing images of nanoparticles in the process were graphically described based on the internal interaction forces of a droplet. Two stronger areas in the changes of SERS intensity were achieved with a high concentration of halogen ions, while only one maximum intensity area was obtained with a low concentration of halogen ions added. This method can effectively avoid complex and unpredictable microenvironments of SERS substrates in the liquid drop, further improving the reproducibility of SERS detection as well as broadening it to biological applications.

The spectroscopy of surface-enhanced Raman scattering (SERS), with its high sensitivity and specific chemical fingerprinting, has received increasing attention. A stable substrate is extraordinarily important for the trace detection of the SERS technique, but the challenge of SERS substrate production with high stability and uniformity still imposes the unavoidable barriers. In this paper, we design a multilayer core−shell-nanostructured ZrO 2 @Ag@SiO 2 nanoparticle through liquid extraction. First, we regulated the usage of AgNO 3 (1 wt %) to obtain Ag@SiO 2 which is silver coated with uniform distribution; on the surface of silica, the number of silver particles is abundant. Then, we discussed the influence when different concentrations of zirconium propoxide are added on the zirconia layer's thickness. Then, we applied FDTD simulation to explain the position of SERS "hotpots" with and without ZrO 2 coating. We have found that the detection capability of ZrO 2 @Ag@SiO 2 can be up to 10 −9 M for 4-ATP; with ZrO 2 @Ag@SiO 2 SERS substrates exposed to the atmospheric environment for up to 30 days, we could still obtain the excellent SERS signal performance contributed by the good chemical stability of ZrO 2 , when ZrO 2 is coated on the surface of Ag@SiO 2 , the zirconia layer formed has a protective role . These experimental results have indicated that the outer zirconia layer could prevent the silver surface from being oxidized, ensuring its stability , which is quite crucial for the applied SERS.

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