DNA-engineered nanoprobe with single-excitation dual-emission for ratiometric luminescence detection of mercury ions

The development of single-excitation dual-emission (SEDE) ratiometric nanoprobes has emerged as a crucial strategy for the detection of heavy metal ions. In this study, a rare earth-based SEDE nanoprobe, designated ZG-Tb, was developed for rapid and sensitive Hg 2+ detection through Tb 3+ coordination onto guanine-rich hairpin DNA (GH5)-functionalized Cr-doped zinc gallogermanate nanoparticles. Upon 260 nm excitation, ZG-Tb exhibits two distinct emission bands: an intrinsic 696 nm emission from Z nanoparticles and a Tb 3+ -mediated 545 nm emission sensitized by surface-immobilized GH5. In the presence of Hg 2+ , competitive interaction between Hg 2+ and Tb 3+ for GH5 results in the selective quenching of the 545 nm emission while leaving the 696 nm emission unaltered. The ratiometric luminescence response ( I 545 / I 696 ) enables quantitative detection of Hg 2+ within 1 min, with a linear range of 0–30 nmol/L and a detection limit of 1.45 nmol/L. The nanoprobe also shows reliable performance in drinking and tap water samples, underscoring its potential for practical applications.