Research On Surface-enhanced Raman Spectroscopy Applied In Detecting Dissolved Furfural In Transformer Oil

To realize accurate and simultaneous detection of multiple aging characteristic substances dissolved in transformer produced by oil paper insulation, and change current situation that the analysis of multiple characteristic substances need multiple equipment, cumbersome process, and laboratory complement, further research of multicomponent detection sensor technology is the key. Laser Raman spectroscopy technique has advantages for detecting multiple parameters simultaneously, which has a good application prospect in the detection of trace characteristic substances in transformer oil; But constrained minimum detectable concentration and detection sensitivity is the technical bottleneck for the application in trace characteristic substances analysis. Due to the optical enhancement effect of nanostructures, surface-enhanced Raman spectroscopy(SERS) is widely used in high sensitive and high resolution material detection, and even molecule detection, which effectively solve the issue of low sensitivity of Raman spectra in surface science and trace analysis. At the same time, the development of nanotechnology has injected new vitality to the SERS development. The paper is based on Raman spectrum detection of furfural dissolved in transformer oil, study on surface enhanced Raman spectroscopy detection method of the trace characteristic substances dissolved in transformer oil, which has important theoretical and practical significance.Combined with Raman scattering and surface-enhanced Raman scattering principle, the nanostructure model of surface enhanced substrate structure is proposed, and the near-field electric field distribution is calculated using the finite difference time domain(FDTD) simulation which further reveals parameters responsible for electromagnetic field enhancement. The simulation results show the SERS enhanced factors are sensitive to interparticle spacing and material for solid support but insensitive to particle size. Combined with the electromagnetic field simulation results, Gold nanoparticles of different particle sizes have been prepared, which are characterized by TEM and UV-vis spectrum. Different SERS substrates have been prepared, which are characterized by AFM. Rational selecting the substrate materials, the types of coupling agent according to the characterized images. p-Aminothiophenol(PATP) is used to realize the stable combination of gold particles and Au film. Self-assembled substrate from monolayer to six layers has been prepared which are characterized by SEM to investigate the nanostructure. On the basis, the influence of the assembled layers on SERS activity is studied, the enhanced factors and detection limit of the substrates with the highest Raman activity are calculated, and the reproducibility and stability are tested. The experimental results show the substrates formed by six layers of 60 nm Au NPs decorated on a 30 nm thick Au film are highest Raman-active, which is consistent with the simulation results. The SERS factor of the optimal substrates is about 5.57×103, and the detection limit is 5×10-5 mol/L. The 3D Raman spectra and RSD values for major peaks show the good reproducibility of the substrates. The SERS intensities changing with time collected on the six-layered substrate show the good stability. The Raman spectra of different concentrations of furfural in transformer oil are measured, and the detection limit of furfural in transformer oil is 1.1×10-4 mol/L using normal Raman detection. The research work has laid a solid foundation for the detection of furfural in transformer oil based on surface enhanced Raman spectroscopy.