A turn-on fluorescent sensor for highly sensitive mercury(ii) detection based on a carbon dot-labeled oligodeoxyribonucleotide and MnO2 nanosheets†
Abstract
A novel fluorescent turn-on aptasensor has been developed for the detection of mercuric ions (Hg2+) based on carbon dots (CDs) as donor molecules and MnO2 nanosheets as acceptor molecules. In this work, an effective fluorescent probe was fabricated through the conjugation of a single-stranded oligodeoxyribonucleotide (ssDNA) on the surface of CDs. In the absence of the target Hg2+, the CDs labeled with ssDNA were adsorbed on the MnO2 surface via van der Waals forces. The fluorescence signal of CDs was then quenched by MnO2 nanosheets via the fluorescence resonance energy transfer (FRET) mechanism. While Hg2+ was introduced, the specific affinity interactions between ssDNA and Hg2+ could detach CDs-labeled ssDNA (ssDNA-CDs) from the MnO2 surface because of the production of the thymine–Hg2+–thymine (T–Hg2+–T) complex, leading to the recovery of the fluorescence intensity. Under the optimal reaction conditions, the fluorescence intensity of CDs enhanced gradually with the increasing concentration of Hg2+ ions in the range from 2 to 200 nmol L−1 and the limit of detection was found to be 0.67 nmol L−1. In addition, the proposed strategy developed its application in the determination of Hg2+ in real samples with excellent performance. These features illustrated that the designed fluorescent sensing platform is a reliable quantitative candidate for potential applications in biological and analytical fields.