In Situ SERS Detection of Furfural in Various Insulating Dielectrics in Carbon Cloth-Au-Ag for Understanding LOD Influence Mechanism under Multiple Parameters

Insulating oil, as a crucial liquid dielectric in large oil-immersed power transformers, directly influences the safety and stability of the power transmission and transformation system through its physical, chemical, and electrical properties. Presently, mineral insulating oil is extensively utilized on a global scale. Regrettably, this type of oil is confronted with various safety and environmental challenges owing to its low flash point and the inherent difficulty in natural degradation. Therefore, new types of natural ester and synthetic ester insulating oils are expected to serve as promising alternatives to mineral oil. This study employed ion sputtering and chemical reduction techniques to deposit Au-Ag nanoparticles on the surface of carbon cloth, resulting in the fabrication of a flexible carbon cloth-Au-Ag (CC-Au-Ag) surface-enhanced Raman scattering (SERS) substrate. Subsequently, a study was conducted to explore the aging behavior of both natural esters and synthetic esters. Simultaneously, with the unique benzene ring structure of the adapter molecule 4-Aminothiophenol (4-ATP), one end can be anchored on the CC-Au-Ag surface through the S-Ag/Au bond. The thiol group (-SH) at the other end, under acidic and thermal catalytic conditions, reacts with furfural through a Schiff base reaction, securely anchoring the furfural molecules on the substrate surface and generating furfural derivatives with a larger Raman scattering cross-section. Building upon distinct limit of detection (LOD) of furfural in diverse insulating dielectrics including Canola oil (0.01 mg/L), Mineral oil (0.025 mg/L), Soybean oil (0.05 mg/L), Pentaerythritol ester oil (0.1 mg/L), and Mixed vegetable oil (1 mg/L), this study delves into the influence patterns of physical parameters-such as Viscosity, Dielectric constant, Density, Pour point on the LOD. Furthermore, a dynamic diffusion model for furfural in various insulating media was established through molecular dynamics simulation. This model elucidated that viscosity stands out as one of the primary factors influencing furfural diffusion. This study introduces an innovative approach for the in-situ, non-destructive, and rapid detection of furfural in various insulating dielectrics. It holds promising applications for on-site assessment and diagnostic evaluation of the aging status of electrical equipment.