Quantification of gold(III) in solution and with a test stripe via the quenching of the fluorescence of molybdenum disulfide quantum dots

The paper describes a fluorescent method for determination of Au(III) using molybdenum disulfide quantum dots (MoS₂ QDs) that were prepared by a hydrothermal route using glutathione as a reductant. The photoluminescence of MoS₂ QDs peaks at 416 nm if excited at 340 nm and is temporally stable even in presence of NaCl or when stored in the refrigerator for one year. Its quantum yield is 12.7 %. The blue-green fluorescence of MoS₂ QDs is fairly specifically quenched by Au(III) ions and therefore presents a useful nanoprobe for this ion. Fluorescence intensity drops linearly with the concentration of Au(III) in the range from 0.5 to 1000 μM, and the lower detection limit is 64 nM. The quenching mechanism was investigated and it is concluded that the process is due to the reduction of Au(III) and the deposition of Au(0) on the surface of the MoS₂ QDs. The nanoprobe was successfully applied to the determination of Au(III) in (spiked) environmental samples. A test stripe for Au(III) was obtained by soaking a piece of paper with a colloidal solution of the MoS₂ QDs, and it was found that this stripe, after drying, can also be used to quantify Au(III) via fluorescence. (author)