Use of Fluorescent DNA-Templated Gold/Silver Nanoclusters for the Detection of Sulfide Ions

We have developed a one-pot approach to prepare fluorescent DNA-templated gold/silver nanoclusters (DNA-Au/Ag NCs) from Au3+, Ag+, and DNA (5'-CCCTTAATCCCC-3' in the presence of NaBH4 in order to detect sulfide (S2-) ions on the basis of fluorescence quenching. The as-prepared DNA-Au/Ag NCs have been characterized by UV-vis absorption, fluorescence, circular dichroism, X-ray photoelectron spectroscopy, and electrospray ionization-mass spectrometry measurements. Relative to DNA-Ag NCs, DNAAu/Ag NCs are much more stable in high ionic strength media (e.g., 200 mM NaC1). The quantum yield of the as-prepared DNA-Au/Ag NCs is 4.5%. We have demonstrated that the fluorescence of DNA-Au/Ag NCs is quenched by S2- ions through the interaction between sulfide ions and gold/silver atoms/ions, a result which leads to changes in the conformation of the templated DNA from packed hairpin to random coil structures. These changes in fluorescence intensity allow sensitive detection of S2ions at concentrations as low as 0.83 nM. To minimize interference from I- ions for the detection of S2- ions using the DNA-Au/ Ag NCs, the addition of sodium peroxydisulfate to the solution is essential. We have validated the practicality of this probe for the detection of S2- ions in hot spring and seawater samples, demonstrating its advantages of simplicity, sensitivity, selectivity, and low cost.