Thymine-Functionalized Gold Nanoparticles (Au NPs) for a Highly Sensitive Fiber-Optic Surface Plasmon Resonance Mercury Ion Nanosensor.

Mercury ion (Hg) is considered to be one of the most toxic heavy metal ions. Once the content of Hg exceeds the quality standard in drinking water, the living environment and health of human beings will be threatened and destroyed. Therefore, the establishment of simple and efficient methods for Hg ion detection has important practical significance. In this paper, we present a highly sensitive and selective fiber-optic surface plasmon resonance (SPR) Hg ion chemical nanosensor by designing thymine (T)-modified gold nanoparticles (Au NPs/T) as the signal amplification tags. Thymine-1-acetic acid (T-COOH) was covalently coupled to the surface of 2-aminoethanethiol (AET)-modified Au NPs and Au film by 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride/N-Hydroxysuccinimide (EDC/NHS) activation effect, respectively. In the presence of Hg ions, the immobilized thymine combines specifically with Hg ions, and forms an Au/thymine-Hg-thymine/Au (Au/T-Hg-T/Au) complex structure, leading to a shift in SPR wavelength due to the strong electromagnetic couple between Au NPs and Au film. Under optimal conditions, the proposed sensor was found to be highly sensitive to Hg in the range of 80 nM-20 µM and the limit of detection (LOD) for Hg was as low as 9.98 nM. This fiber-optic SPR sensor afforded excellent selectivity for Hg ions against other heavy metal ions such as Fe, Cu, Ni, Ba, K, Na, Pb, Co, and Zn. In addition, the proposed sensor was successfully applied to Hg assay in real environmental samples with excellent recovery. Accordingly, considering its simple advantages, this novel strategy provides a potential platform for on-site determination of Hg ions by SPR sensor.