A gold coating nanoporous anodized alumina oxide membrane as the substrate for rapid surface enhanced Raman spectroscopy detection of conjugated cyanide in fingertip blood

Rapid and sensitive detection of cyanide (free and conjugated) in blood samples is of vital significance for the clinical treatments and forensic verifications of cyanide poisoning. To overcome the disadvantages of conventional in-field detection methods, a facile, rapid and sensitive surface enhanced Raman spectroscopy (SERS) method for the analysis of free and conjugated cyanide using functionalized nanoporous anodic aluminium oxide (AAO) membrane coupled with hand-held Raman spectrometer has been developed in this study. A gold coating nanoporous AAO membrane with a high specific surface area, appropriate surface roughness and super-hydrophobicity has been prepared. The significant SERS signals enhancement benefiting from the high enrichment capacity and strong plasmonic hot-spots effects of the membrane has been achieved for hydrocyanic acid (HCN). Optimal parameters, including substrate modification, dissociation and capture conditions for blood samples have been investigated. The conjugated cyanide in the fingertip blood could be effectively liberated by the addition of H3PO4 and NaBH4, followed by the capture of HCN on the membrane and analyzed based on SERS. The whole detection procedure only needed 2 min, and the limit of detection could reach 10 ng/mL in only ∼ 50 μL fingertip blood. Therefore, this approach is expected to be a powerful point of care testing (POCT) tool for the diagnosis of cyanide poisoning in clinical and forensic applications.