A Fluorescence Biosensor Based on Carbon Quantum Dots Prepared from Pomegranate Peel and T-Hg²⁺-T Mismatch for Hg²⁺ Detection

Mercury ions (Hg²⁺) can cause damage to human health, and thus, the study of the detection of Hg²⁺ is extraordinarily important in daily life. This work reported a fluorescence biosensor for the detection of Hg²⁺. The key point of this strategy was that the fluorescence of carbon quantum dots made from pomegranate peel (P-CQDs) was quenched by hemin, and restored after G-quadruplex binding with hemin. The presence of Hg²⁺ caused thymine (T)-rich DNA fragments to form T-Hg²⁺-T mismatches, and this change allowed the release of G-quadruplex. G-quadruplex could change the fluorescence of hemin/P-CQDs. P-CQDs exhibited excellent properties through characterization analysis, such as transmission electron microscope, X-ray photoelectron spectroscopy and Fourier transform infrared. This proposed fluorescence detection strategy established the linear ranges of Hg²⁺ from 1 nM to 50 nM. In conclusion, this simple biosensor had the advantages of strong sensitivity, high selectivity, and low cost for Hg²⁺ detection in environmental water samples.