| As a new detection method,surface enhanced Raman scattering?SERS?has attracted more and more attention from scholars and experts because of its nondestructive and high-sensitivity detection characteristics.At present,the most widely used SERS substrates are Au,Ag and Cu,Among them,Ag has the best SERS performance as a substrare However,there are still many shortcomings of the nano silver ball as the traditional SERS substrate,such as the chemical reaction of the target molecule and the impurity peak,the aggregation and oxidation are easy to occur in the storage time,and the target can not be used for the target.The specific detection of molecules and so on;the emergence of these problems will cause interference in the actual detection process of samples.In this paper,two kinds of nano silver with linear and flower morphology were prepared,and the sensitivity of SERS substrate was optimized.At the same time,a new type of SERS substrate was prepared by coated silica and molecularly imprinted layer with flower like nano silver as the carrier,and the problem of poor stability of the substrate and the detection of target molecule specificity could be solved.The main contents and results are as follows:1.Silver nanowires were prepared using silver nitrate as the silver source.Polyvinyl alcohol was used to prepare silver nanowires.Nano silver wires were characterized by scanning electron microscopy?SEM?and ultraviolet-visible spectrophotometer?UV-Vis?.Nanoparticles with uniform diameter and length were successfully prepared.Silver line.The norfloxacin solution was detected using a hand-held Raman spectrometer with an excitation wavelength of 785 nm.The results show that the substrate has a good SERS effect,and the enhancement factor reaches 1.44×107.When the concentration of 10-3mol/L 10-8 mol/L of norfloxacin solution was detected,the sample concentration and the characteristic peak intensity were found to have a good linear relationship;to further investigate the dispersion of nano silver wire on the glass sheet and Spectral reproducibility,Randomly collected 6 points of Raman signal on a glass slide to detect norfloxacin(10-3 mol/L)samples,and repeated the detection of 6 norfloxacin(10-5 mol/L)samples Raman spectrum.The results of Raman show that the silver nanowires have good dispersibility on the glass sheet,and exhibit good spectral reproducibility in the detection of norfloxacin.2.Using silver nitrate as the silver source,ascorbic acid as the reducing agent,and citric acid as the stabilizer,nanometer silver flowers with uniform morphology were prepared by SEM,XRD and Fourier transform infrared spectrometer?FT-IR?.With silver flower as the core and tetraethylorthosilicate?TEOS?as the silicon source,using its characteristic of hydrolysis under alkaline conditions,silica is deposited on the surface by SEM,transmission electron microscope?TEM?,FT-IR,Energy spectrum?EDS?and X-ray diffraction?XRD?characterization methods were used to successfully prepare Ag@Si O2composites;4-mercaptobenzoic acid?4-MBA?was used as a probe molecule to study different cladding thicknesses for Ag.The influence of SERS performance on the@Si O2substrate shows that the SERS signal gradually decreases as the thickness of the silicon layer increases.The results of Raman indicate that the Ag@Si O2 substrate has the best SERS performance when the cladding thickness is 7 nm,and the detection limit of the norfloxacin solution is 10-9 mol/L.Finally,the stability of Ag@Si O2 is investigated.It was found that when the storage time is 6 months,the Ag@Si O2 substrate still has a good SERS effect,and it has been proved that the coating of the silica greatly improves the stability of the Ag substrate.3.The nano-silver flower was used as the carrier,3-aminopropyltriethoxysilane?Aptes?was the silanization reagent and functional monomer,norfloxacin was the template molecule,TEOS was the cross-linker,were analyzed by SEM,TEM,XRD,EDS,FT-IR and other characterization methods to successfully prepare Ag@MIP composites.First of all,by changing the adsorption time and the substrate to investigate its SERS performance,then using oxacillin and R6G as competitive molecules,the competitive adsorption of Ag@MIP was investigated.Finally,Ag@MIP was repeated to examine the substrate reutilization.The experimental results show that the best adsorption time of Ag@MIP substrate is 120 min.It has good selectivity as a SERS substrate and can achieve specific adsorption of norfloxacin molecules.The limit of detection for norfloxacin is 10-13 mol/L,at the same time,the substrate shows better SERS performance and better repeatability than Ag and Ag@NIP.In this paper,three SERS substrates of Ag,Ag@Si O2,and Ag@MIP have been prepared.Compared with traditional SERS substrates,they have high SERS sensitivity,high stability,specific adsorption,and reusability.The SERS technique is used to detect real samples. |
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