DNA-based chemiluminescent nanoprobes for highly sensitive and selective detection of mercury(II) ion

A simple and sensitive DNA-stablized gold nanoparticle (AuNP)-based chemiluminescent (CL) probe for detecting mercury ion (Hg(2+)) in aqueous solution has been developed. The CL strategy relies upon the catalytic activity of unmodified AuNPs on the luminol-H2 O2 CL reaction, and the interaction of unmodified AuNPs with DNA. The unmodified AuNPs can effectively differentiate unstructured and folded DNA. The DNA desorbs from AuNPs in the presence of Hg(2+), leading to the increase in CL signal. By rationally varying the number of thymine in single-strand oligonucleotides, the detection range could be tuned. Employing single-strand oligonucleotides with 14 thymine in the detecting system, a sensitive linear range for Hg(2+) ions from 5.0 × 10(-10) to 1.0 × 10(-7) mol/L and a detection limit of 2.1 × 10(-10) mol/L are obtained. Changing the number of thymine to 10 and 6, it leads to a narrow detection range but a high sensitivity. Besides, DNA-based CL nanoprobes exhibit a remarkable selectivity for Hg(2+) ions over a variety of competing metal ions.