Fabrication of Ag@TiO2 electrospinning nanofibrous felts as SERS substrate for direct and sensitive bacterial detection

In order to develop a novel method for bacteria detection, Ag@TiO 2 electrospinning Nanofibrous felts have been fabricated by in situ decoration of size tunable Ag nanoparticles on anatase TiO 2 nanofibers. The morphologies and structures of the as-prepared Ag@TiO 2 electrospinning nanofibrous felts were characterized by techniques of scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy, and X-ray diffraction. The result show that Ag NPs were uniformly deposited on the surfaces of TiO 2 nanofibers, especially when the deposition time in Tollens’ reagent was 10 min. The free-standing composite nanofibrous felts processes superb performance of surface enhanced Raman scattering, which was demonstrated by small probe mecules of 4-mercaptobenzoic acid and 4-mercaptophenol, and the lowest detection limit was near to10 −9  mol/L. More importantly, the as-fabricated Ag@TiO 2 nanofibrous felts as SERS substrate can detect biomacromolecules such as bacteria of Escherichia coli ( E. coli ) and Staphylococcus aureus ( S. aureus ) directly without previous bacteria-aptamer conjugation as the traditonal process. In addition, the composite nanofibrous felts also show outstanding antimicrobial activities against both Gram-negative of E. coli and Gram-positive of S. aureus , evaluated by method of absorption and microscopic observation. The results show that the bacteriostasis rate is reached to 99%, especially significant for E. coli . The free-standing, high porous, and flexible substrate of Ag@TiO 2 electrospun nanofibrous membranes have potential application in versatile fields such as microorganism sensors and water purifier.