Study On The Surface-enhanced Method Of Raman Spectroscopy For Detecting Trace Characteristic Substances Dissolved In Transformer Oil

The accurate detection of trace characteristic substances dissolved in transformer oil is the key to diagnose the oil-paper insulation aging problems.Nowadays,detecting and analyzing these characteristic substances needs various equipment and complex processes,are mostly done in the laboratory,and without in-situ detection.Surface-Enhanced Raman Spectroscopy(SERS)has advantages for detecting multiple parameters simultaneously by a laser with single frequency.With the advantage of high sensitivity,rapid analysis and no sample pretreatment,it has broad application prospects in detecting trace characteristic substances dissolved in transformer oil.In the application of SERS,the selection and preparation of substrates with SERS activity is the key to obtain enhanced Raman signals with high quality.This paper carries out a research on surface-enhanced Raman spectroscopy detection method of the trace characteristic substances dissolved in transformer oil.The main research contents and achievements are as follows:(1)Based on the principle of surface-enhanced Raman scattering,FDTD Solutions is performed to build metallic nanostructure model,the effect of factors such as metal materials,substrate,particle spacing to Localized Surface Plasmon Resonance(LSPR)in oil have been simulated.The results show that Ag produces a larger electric field enhancement than Au under 532 nm.Compared with silicon wafer,Ag dimers located on Au film have a larger electric field enhancement.The electric field intensity between Ag nanoparticles increases with the decrease of gap distance.(2)Silver colloids are prepared by using sodium citrate as reducing agent,which are characterized by transmission electron microscopy(TEM)and UV-Visible absorption spectroscopy(UV-Vis).The results show that the Ag nanoparticles are nearly spherical-like with average diameter of 52 nm,and the size distribution is uniform.Bifunctional molecules 3-aminopropyltrimethoxysilane(APTMS)and p-Aminothiophenol(PATP)are used to realize the stable combination of Ag nanoparticles and different substrate surface(silicon wafer and Au film).The substrates are characterized by X-ray photoelectron spectroscopy(XPS),scanning electron microscope(SEM),R6 G.The results show that the substrates prepared with Au film,silver nanoparticles in per unit area are more than that of silicon wafer,which have more "hot spot" and better enhancement effect.(3)Using Au film as substrate,we have prepared SERS substrates with different experimental parameters(PATP concentration,deposition time of PATP,immersion time of silver colloids)which are characterized by SEM,R6 G.We have performed a detailed investigation as to the effect of surface particle coverage on the enhance performance of substrates.The results show that Ag nanoparticles on substrates which are deposited from 0.1 mol/L PATP solutions for 5 h and silver colloids for 12 h are more uniform and closely arranged and have better enhancement effect.Based on the Raman spectroscopy detection platform that built in laboratory,combined with the substrates prepared by Au-based silver nanoparticles,taking the analysis of furfural dissolved in transformer oil as an example,the in-situ detection limit is 0.53 mg/L.At the same time,the substrates show good homogeneity and uniformity.