A label-free SERS approach to quantitative and selective detection of mercury (II) based on DNA aptamer-modified SiO2@Au core/shell nanoparticles

A prototype of label-free SERS sensor, based on the formation of T-Hg2+-T pairs and the corresponding orientation variation of DNA on Au shell surface, was developed for detection of Hg2+ in aqueous solution quantitatively and selectively. The DNA aptamer immobilized on the surface of SiO2@Au core/shell nanoparticles (NPs) consisted of two segments, namely, the segment which has the consecutive thymines (T) severing as the Hg2+ recognition elements, and the segment which contains the guanine (G) and adenine (A) bases working as the signal reporter. With interaction of Hg2+ ions and the thymines between the adjacent single-stranded DNA (ssDNA), the DNA molecule adopted vertical orientation, resulting in increase of Raman intensity ratio I(660 cm(-1))/I(736 cm(-1)) with increase of Hg2+ concentration, which thus allowed to measure trace amounts of Hg2+ in aqueous solution selectively and quantitatively. Our results revealed that this label-free SERS sensor could sensitively respond to Hg2+ ions within a wide concentration range (from 1 x 10(-8) to 1 x 10(-3) M). This work therefore demonstrates that proper design of aptamer-modified SiO2@Au core/shell NPs can be utilized for label-free SERS detection of heavy metal ions in the environment. (c) 2017 Elsevier B.V. All rights reserved.