Study On Highly Consistent SERS And Its Detection Characteristics For Furfural In Transformer Oil

Surface enhanced Raman spectroscopy（SERS）technology can be well applied to the detection of state characteristics in the process of power equipment operation,which is an important measure to ensure the safety of power equipment operation.The content of furfural in transformer oil is one of the key indexs of oil-paper insulation equipment aging state.The research of SERS detection of furfural in oil is of great significance to expand the application of Raman spectroscopy in the field of power equipment operation safety detection,and to realize the reliable detection of furfural and other oil paper insulation aging characteristics.In this paper,the problems of low furfural content in transformer oil and small molecular scattering cross section are discussed.The preparation of high consistency SERS substrate and its detection characteristics for furfural in transformer oil were studied.The influence of different parameters on the performance of SERS substrate was calculated theoretically,and the optimal values of each parameter were determined.The differences of fabrication methods and properties between the two methods were compared and analyzed to determine the optimal preparation method of SERS substrate.The Au@Ag core-shell structure was used to solve the problem of poor homogeneity of particles,and high consistency SERS substrate was obtained.The Raman spectra of furfural in transformer oil based on Au@Ag core-shell structure SERS substrate were studied.The main work of this paper is as follows:（1）COMSOL software was used to simulate the effects of particle morphology,material,spacing and particle size on the enhancement effect and consistency of SERS substrate.The influence of different parameters on the performance of SERS substrate was theoretically calculated,and the optimal parameters for preparing high consistent SERS substrate were determined.The results show that when the particle size is 150±5nm and the particle spacing is 1-1.4 nm,the SERS substrate has high enhancement performance and consistency under the excitation of 532 nm incident wavelength.（2）The different fabrication mechanisms of liquid-solid self-assembled SERS substrate and gas-liquid self-assembled SERS substrate were studied in order to determine the best preparation method of SERS substrate.It was found that the particle films on the gas-liquid self-assembled SERS substrate were more compact by characterization.Different concentrations of R6G were detected by SERS,and the enhancement effect and consistency of the two SERS substrates were compared and analyzed.It is found that the relative standard deviation of Raman characteristic peak intensity at different positions of gas-liquid self-assembled SERS substrate is only 9.8%.Therefore,the gas-liquid self-assembly method is the best method to prepare high consistency SERS substrate.（3）In order to solve the problem of poor uniformity of large-size silver nanoparticles（NPs）,the Au@Ag core-shell NPs were proposed to replace the pure Ag NPs.Through theoretical calculation,it is found that gold and silver core-shell nanoparticles have the same optimal particle size corresponding to the maximum enhancement factor,and the effect on the enhancement factor only accounted for 3.39%of the total value.The results showed that the enhancement factor of R6G was 1.75×10⁵,and the relative standard deviation（RSD）was only 4.8%.Therefore,It is confirmed that the SERS substrate with Au@Ag core-shell NPs prepared by gas-liquid self-assembly method has better enhancement performance and consistency,and the SERS substrate is suitable for Raman spectroscopy detection of target molecules.（4）The method and characteristics of Raman spectroscopy in situ detection of furfural content in transformer oil were studied.Firstly,the mathematical relationship between furfural concentration and characteristic peak intensity was established,and the minimum detection concentration of unenhanced Raman spectroscopy was determined as 2.5 mg/L.The reason for the shift of characteristic peak of furfural was analyzed by density functional theory.It was confirmed that the shift of characteristic peak 1670cm^-1 was mainly due to the interference of C=O bond of furfural.Furthermore,the detection characteristics of furfural in transformer oil based on the high consistency SERS substrate with Au@Ag core-shell NPs were studied.The linear function relationship between Raman characteristic peak and furfural concentration was established,and the minimum detection concentration was determined to be 0.092.The results show that the enhancement factor can reach 4.53×10³,and the relative standard deviation corresponding to the intensity of characteristic peak is only 5.8%,which has good consistency.In this paper,the application of Raman spectroscopy technology in the condition detection of oil paper insulation power equipment is studied and expanded,which lays a solid foundation for the high sensitive and reliable detection of oil paper insulation aging characteristics such as furfural.