Highly Sensitive Surface-Enhanced Raman Spectroscopy Substrates of Ag@PAN Electrospinning Nanofibrous Membranes for Direct Detection of Bacteria

Surface-enhanced Raman spectroscopy (SERS) can be applied for biological detection because of its high sensitivity and noninvasiveness for analytes. Herein, we engineer plasmonic free-standing substrates composed of Ag nanoparticles (NPs) supported on polyacrylonitrile (PAN) electrospinning nanofibrous felts as sensors for bacterial detection. Ag NPs are evenly distributed on PAN nanofibers after preimpregnation and impregnation of PAN nanofibers in Tollens' reagent. The size and loading density of Ag NPs are tunable by adjusting the reaction time of glucose and Tollens' reagent, thereby allowing the tuning of the surface plasmon resonance. Using 4-mercaptophenol (4-MPh) and 4-mercaptobenzoic acid (4-MBA) as probe molecules, SERS effects of Ag@PAN composite nanofibers are investigated, and the substrates allow the detection of 4-MPh and 4-MBA at a low concentration of 10 -9 mol/L. Importantly, the substrates exhibit a high sensitivity of SERS performance for bacterial identification without a specific bacteria-aptamer conjugation. The SERS substrates also show good uniformity of SERS response for bacterial organelles. Furthermore, the antimicrobial property was evaluated, and the results indicate that the sample of Ag@PAN nanofiber mats possesses excellent antibacterial properties against Escherichia coli and Staphylococcus aureus .