On-site detection of #45 transformer oil aging using high-consistency nanoarray flexible SERS aptamer sensors

A three-dimensional biomimetic high-consistency nanoarray flexible surface-enhanced Raman scattering (SERS) substrate was developed in this study, based on a cicada wing biological template. An AuAg bimetallic nanoarray with hierarchical nanogap structures was constructed on the cicada wing surface by ion sputtering technology combined with a chemical reduction method, resulting in the formation of high-density plasmonic hot spot regions. The substrate surface was further modified with 4-aminothiophenol (4-ATP), a 4-ATP-functionalized cicada wing-supported AuAg SERS substrate was successfully prepared. Additionally, a portable Raman spectroscopy field detection device for furfural in #45 mineral oil was developed, enabling rapid detection of furfural content in transformer oil. It was demonstrated by experimental results that a limit of detection (LOD) of 0.01 mg/L for furfural in #45 mineral oil was achieved by the detection system, the enhancement factor is 1.86 × 10⁴, meeting the detection requirements for furfural during mild aging of transformer insulation paper. A good fit (R² = 0.977) was yielded by linear regression analysis using the least squares method between the logarithm of furfural concentration in #45 mineral oil and Raman intensity. Furthermore, the performance metrics of the substrate were evaluated by the system: the relative standard deviation (RSD) was found to be 3.54% and 3.06%, indicating good signal repeatability and consistency for furfural; the SERS signal intensity was observed to remain at 93.5% of the initial value after 35 days, confirming the substrate's long-term stability. The method was used to detect 7110 kV transformers in northwest China, and the test results were verified by gas chromatography furfural concentration in #45mineral oil is positively correlated with carbon dioxide content and running time, which fully demonstrates that the portable Raman spectroscopy field inspection device provides reliable technical support for on-site aging assessment and great potential for power system maintenance. A reliable technical means for the rapid on-site detection of furfural in #45 mineral oil is provided by this study, offering significant practical application value for assessing the aging state of oil-paper insulation.