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@TiO2 electrospinning Nanofibrous felts have been fabricated by in situ decoration of size tunable Ag nanoparticles on anatase TiO2 nanofibers. The morphologies and structures of the as-prepared Ag@TiO2 electrospinning nanofibrous felts were characterized by techniques of scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy, and Xray diffraction. The result show that Ag NPs were uniformly deposited on the surfaces of TiO2 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 to 10(-9) mol/L. More importantly, the as-fabricated Ag@TiO2 nanofibrous felts as SERS substrate can detect biomacromolecules such as bacteria of Escherichia coll. (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. coll. 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@TiO2 electrospun nanofibrous membranes have potential application in versatile fields such as microorganism sensors and water purifier.