4-ATP-modified CNTs@NiO–Fe2O3–Ag SERS filter membrane for rapid in-situ detection of furfural in mineral oil

Evaluating the transformer aging state and detecting multi-aging characteristics in transformer oil with high sensitivity and fast speed has become a key challenge. This study introduces a P–N heterojunction (CNTs@NiO-α-Fe2O3) fabricated through electroless nickel plating and a one-step hydrothermal method. Additionally, silver nanoparticles (AgNPs) with adjustable particle sizes are grown on the surface using a chemical reduction method. To obtain high sensitivity and rapid SERS signal, CNTs@NiO-α-Fe2O3–Ag gel is adsorbed on a disposable needle filter (220 nm) surface, and 4-aminothiophene (4-ATP) is grafted onto the surface of SERS substrate. The minimum detection limit was 0.025 mg/L (EF = 5.22 × 104), and the response time of SERS best signal could be shortened to 3 min. Density functional theory (DFT) calculations reveal that by constructing a P–N heterostructure of NiO–Fe2O3 and assessing the adsorption energies of furfural, acetone, and methanol on the surface of the P–N heterojunction. This SERS strategy has a huge application prospect in the aging diagnosis of oil-paper insulation systems in a transformer. To obtain high sensitivity and rapid SERS signal, CNTs@NiO-α-Fe2O3–Ag gel is adsorbed on a disposable needle filter (220 nm) surface, and 4-aminothiophene (4-ATP) was grafted onto the surface of SERS substrate. The formed nanofiltration membrane realized detection of furfural in transformer oil with high-sensitivity, selectivity and specificity. [Display omitted] •CNTs@NiO–Fe2O3–Ag SERS filter membrane was designed and synthesized successfully.•4-ATP was used to enrich furfural molecules on the SERS membrane surface.•The semiconductor has rapid electron transfer efficiency when combined with Ag.•The response time of the best signal on the SERS substrate reduced to 3 min.•The detection limit is 0.025 mg/L, which meets the international detection standard.