Sensitive label-free oligonucleotide-based microfluidic detection of mercury (II) ion by using exonuclease I

► A novel method based on Exo I, DNA and electrophoresis for Hg2+ detection. ► Selective digestion of Exo I on ssDNA. ► Quenching effect of Hg2+ on excited fluorescence states. ► Limit of detection around 15 nM. ► Excellent selectivity over five other metal ions without any secondary reagent.