Study On The Method Of Improving The SERS Precision Of Silver Sol Substrate

Surface enhanced Raman scattering spectroscopy(SERS)has the advantages of ultra-high sensitivity,high selectivity and non-invasiveness,and has great potential for development in the fields of life sciences,food safety,and environmental testing.In view of the advantages of silver sol substrates such as easy preparation,low cost,and significant SERS effect,silver sol substrates are widely used in the field of academic research.Generally,during the testing process,the silver sol substrate is mixed with the sample to be tested.Changes in sample composition and mixing process have a significant effect on the formation of hot spots.In the process of repeatedly collecting its SERS spectrum,the hot spot distribution is difficult to reproduce result in poor reproducibility of its SERS analysis results;some substances are also accompanied by the generation of fluorescence spectra under Raman laser irradiation,and the fluorescence decreases significantly with the laser irradiation time.The trend also caused great interference to the SERS spectral accuracy.Therefore,although SERS academic research is very active,there are still many difficulties in practical application,the most serious is poor accuracy.To this end,this paper aims to conduct research on methods to improve the accuracy of SERS analysis on silver glue substrates.The main research contents are as follows:(1)Using hydrothermal reduction method,sodium citrate and silver nitrate were used to prepare a silver sol substrate,which was used to improve the accuracy of SERS analysis.Using basic rhodamine B molecule as a SERS probe,the influence of the order of sample addition,the amount of coagulant,the pH of the mixed solution with the sample,the mixing time,and the concentration of rhodamine B on the SERS effect were studied.The results show that the volume of 1M coagulant is 5μL,1M citric acid is 5μL,the order of addition is silver gum-rhodamine B-coagulant,the mixing time is lmin,its SERS effect is the best;with 1 ppm rhodamine B as the probe molecule And under the above test conditions,the linear correlation coefficient R2=0.98204 of the SERS spectrum of silver glues prepared in different batches.(2)Using basic rhodamine B molecule as a SERS probe,the fluorescence signal accompanying laser irradiation changes with time and concentration,etc.,which causes a serious drift in the baseline of the SERS spectrum and has a significant adverse effect on the accuracy of SERS analysis.The commonly used baseline correction method of Raman spectrum is purely based on mathematical methods.If the parameters are not properly selected,the baseline will be forced to be flattened,which will distort the signal.Based on the change mechanism of Raman fluorescence effect,this paper proposes a difference spectrum matrix of SERS spectrum with time,and performs principal component analysis(PCA)to extract the fluorescence spectrum component in SERS spectrum and establish a new baseline of SERS spectrum.The correction method avoids the distortion problem of the mathematical method and improves the accuracy of SERS analysis.(3)This paper analyzes the influence of the mixing of silver sol and sample on the formation of hot spot distribution,and it is concluded that the hot spot distribution formed by the silver gel substrate during the test is poorly microscopically reproducible.The spot size is on the order of micrometers,and its statistical significance is insufficient.To this end,based on statistical principles,a method to improve the accuracy of SERS analysis using a large spot(maximum spot diameter 7mm)laser Raman spectrometer is proposed.The results show that increasing the spot diameter can significantly improve the accuracy of SERS analysis.Accumulating the spectrum collected with the continuous acquisition of the integrated spectrum has the effect of suppressing high-frequency noise.Using the integrated spectrum is beneficial to improve the accuracy of SERS analysis.Combined with the best test conditions,large spot SERS and the new Raman spectral baseline treatment method can significantly improve the accuracy of silver-based SERS analysis,and increase by about 1 times.