Highly sensitive detection of Hg2+ using molybdenum disulfide-DNA sensors

•Hg2+ cause great damage to organisms. It is important to develop sensors that detect Hg2+.•Freeze stretching can enhance the mechanism of FRET (Fluorescence Resonance Energy Transfer) for Hg2+ detection.•Detection limit of 9.41 nM and a linear range of 0–1 μM was observed under unfrozen conditions.•Detection limit of 4.58 nM and a linear range of 0–2 μM was observed under freezing conditions.