Preparation And Detection Of Controllable Flexible SERS Substrate

The localized surface plasmon coupling effect generated by the deposition of precious metals in the design of nanostructures has achieved ultra-high sensitivity detection as low as single molecule level.These nanostructures largely rely on the optical resonance characteristics of composite metal nanostructures,which can significantly enhance local electromagnetic fields.Therefore,optimizing the detection effect means optimizing the plasma nanostructure to concentrate the local electromagnetic field at the desired location.Ordered nanoarrays with different morphologies were prepared on self-assembled polystyrene（PS）spherical arrays by Magnetron sputtering,etching and other methods,which have excelent SERS enhancement effects and realize the quantitative detection of pesticide thiram and pathogenic toxin.1.Construction of a large and uniform dense hot spot structure and optimization of SERS strength.The importance of optimizing the density and intensity of hot spot distribution for SERS detection is self-evident.However,the design and formation of dense hotspots are difficult,as they exist in nano gaps,cavities,and tips.Based on Magnetron sputtering co sputtering technology,Ag-Si O₂ composite nanoparticle structure was prepared on flexible PDMS substrate.The gap between the nanoparticles in this structure reaches a controllable range of 2-3 nm.The samples were simulated by finite difference time-domain（FDTD）method to prove the cause and location of hot spots.On this basis,a strategy of using flexible PDMS substrate surface wrinkles to construct three-dimensional nano hot spot cavities and composite nano particle structures was proposed,achieving the goal of preparing excelent SERS detection results.The detection limit of thiram was 10^-13M by using the"drip dry"sampling detection method,and the quantitative analysis of thiram concentration was completed.2.Research on uniform nanostructured arrays and structural colors of"lightning rods"with controllable temperature and humidity.After the preparation of general micro nanostructures,it is difficult to design them for secondary processing,and the micro morphology is difficult to easily change.For modern anti-counterfeiting structural colors,the ability to adjust the microstructure based on macroscopic physical quantities and design and process structural colors will be a promising technology for application.Due to the superior water absorption,expansion,dehydration,and contraction properties of PVA adhesive,the ordered and uniform nanostructure undergoes significant changes at different temperatures,resulting in the sample presenting the desired color.By utilizing the good transparency of PDMS,vertical observation without color is achieved,and when tilted at 45°,the sample color is clearly visible.It has important application significance in anti-counterfeiting and information confidentiality transmission processes.3.A reusable SERS substrate is used to detect the mixed virogens secreted by molds.With increasing attention paid to food safety and other issues,SERS testing work is increasing.This puts forward higher requirements for detection efficiency and the cost and reusability of SERS detection substrates.In actual detection work,samples are all mixtures.How to clearly and accurately separate the content and characteristic peaks of each substance from complex mixtures is another test for modern SERS detection work.We prepared a PVA mixed sol containing the substance to be tested and spin coated it on the surface of the nanoarray structure.Perform SERS testing on the sample and analyze the detection sensitivity of the substrate before and after multiple uses.Based on SERS spectroscopy,analyze the characteristic peaks of various pathogenic toxin mixtures and determine the content ratio of each substance.Accurate quantitative analysis of pathogenic toxins secreted by three types of corn surface molds has been completed.