Reversible detection of Hg(II) in pure water based on thymine modified nitrogen, sulfur co-doped carbon dots combined with antidote.

Conventional Hg visual sensors are unsustainable, hindering their practical application for improved water quality and health. In order to address this challenge, herein, N, S co-doped carbon nanodots (NS-CDs) were prepared and well characterized, presented the fluorescent monitoring for Hg over other metal ions with the limit of detection (LOD) of 0.47 µM. Next, the CDs were successfully modified by thymine without any fluorescence labelling (referred to as T-NS-CDs). The sensitivity to Hg cloud be noticeable enhanced due to the formation of T-Hg-T specific base pairs. Accordingly, the LOD was calculated with values as low as 1.56 nM. Furthermore, Hg could be released and complexed with antidote (meso-2,3-dimercaptosuccinic acid) (DMSA-Hg), being the responsible for the reversible interconversion between T-Hg-T and DMSA-Hg. Interestingly, the proposed sensing system also applies to the fluorescent sensing for Hg in tap water with satisfactory recoveries (96.97 %-101.38 %, RSD < 2 %). Thus, by simply combination of elemental doping and surface functionalization, the surface state and functionalities of CDs could be tailorable, endowing the fluorometric sensing towards Hg in environmental system.