A SERS biosensor with magnetic substrate CoFe2O4@Ag for sensitive detection of Hg2+

Mercuric ion (Hg 2+ ) is one toxic metal ion existed in aquatic ecosystems which would seriously damage human central nervous system and other organs. So developing an approach to sensitively detect Hg 2+ in our living environment is urgent and important. In this work, a novel surface enhancement Raman spectrum(SERS) sensor is fabricated for high selective and ultrasensitive detection of Hg 2+ in aqueous solution, based on a stable thymine-Hg 2+ -thymine (T-Hg 2+ -T) structure and the π - π interaction between single-stranded DNA (ssDNA) and single walled carbon nanotubes (SWCNTs). Herein, SWCNTs act as Raman labels to produce characteristic Raman peaks which can be a beacon to quantitative detect Hg 2+ . In the presence of Hg 2+ , the ssDNA can capture Hg 2+ forming T-Hg 2+ -T structure, which makes SWCNTs leave the hot spots of the SERS-based biosensor. With this design, the Raman intensity of SWCNTs decreased with the increasing concentration of Hg 2+ . At the same time, CoFe 2 O 4 @Ag as active SERS substrates can effectively enhance sensitivity and uniformity of the biosensor through aggregation by magnet. Under optimal conditions, this proposed biosensor can detect Hg 2+ at a range from 1   pM to 100   nM with a detection limit of 0.84   pM. With the advantages of good sensitivity, selectivity, simplicity and rapidity, the biosensor is potentially suitable for monitoring of Hg 2+ in environmental applications.