Colorimetric detection of mercury(II) ion using unmodified silver nanoparticles and mercury-specific oligonucleotides

A sensitive and selective colorimetric detection method for mercury(II) has been well-established in this paper. It was based on the conformation change of mercury-specific oligonucleotides (MSO) from random coil structure to hairpin structure upon the addition of Hg(2+) and the phenomenon of salt-induced unmodified silver nanoparticles (AgNPs) aggregation. The calibration curve showed that the net absorption ratio value at 395 and 570 nm increased linearly over the Hg(2+) concentration range of 25-500 nM with a limit of detection of 17 nM. The other environmentally relevant metal ions did not interfere with the determination of Hg(2+).