A new fluorescence detection method for sulfide ions based on Cu-containing metal–organic framework materials and dye-labeled DNA of arbitrary sequence

We developed a new quantitative detection method for trace sulfur ions (S 2− ) in water using a Cu-containing metal–organic framework material (CuBDC) and 6-carboxyfluorescein group (FAM)-labeled DNA of arbitrary sequence. Without S 2− in the system, the FAM-labeled DNA can be adsorbed on the CuBDC surface through π–π stacking, hydrogen bonding, and van der Waals forces, and then the fluorescent dye FAM is near the Cu 2+ on the CuBDC surface, and the fluorescence of FAM is quenched by a photoinduced electron transfer mechanism between Cu 2+ and FAM. With S 2− in the system, S 2− reacts with Cu 2+ in CuBDC to form the more structurally stable compound CuS, leading to CuBDC decomposition, and the FAM-labeled DNA detaches from the CuBDC surface and the fluorescence of FAM recovers. The quantitative detection of S 2− is realized according to the change in FAM fluorescence intensity. Under optimized conditions, a good linear relationship holds between the fluorescence intensity (F i ) of FAM and the concentration ( C i ) of S 2− in the range of 2–120 nmol/L, and the detection limit is 1.5 nmol/L (3 σ, n = 9). The method has good selectivity and accuracy, and it can be applied to rapidly and accurately analyze S 2− in real water samples.