Highly Selective and Sensitive Detection of Hg Based on Förster Resonance Energy Transfer between CdSe Quantum Dots and g-CN Nanosheets.

In the presence of Hg, a fluorescence resonance energy transfer (FRET) system was constructed between CdSe quantum dots (QDs) (donor) and g-CN (receptors). Nanocomposites of g-CN supported by CdSe QDs (CdSe QDs/g-CN nanosheets) were fabricated through an electrostatic interaction route in an aqueous solution. The nanocomposites were characterized by X-ray photoelectron spectroscopy, X-ray diffraction, Fourier-transform infrared spectroscopy, and transmission electron microscopy. Results showed that the g-CN nanosheets were decorated randomly by CdSe QDs, with average diameter of approximately 7 nm. The feasibility of the FRET system as a sensor was demonstrated by Hg (II) detection in water. At pH 7, a linear relationship was observed between the fluorescence intensity and the concentration of Hg (II) (0-32 nmol/L), with a detection limit of 5.3 nmol/L. The new detection method was proven to be sensitive for detecting Hg in water solutions. Moreover, the method showed high selectivity for Hg over several metal ions, including Na, Mg, Ca, Pb, Cr, Cd, Zn, and Cu. The CdSe QDs/g-CN nanosheet conjugate exhibited desirable long-term stability and reversibility as a novel FRET sensor. The novel FRET-based fluorescence detection provided an attractive assay platform for quantifying Hg in complex water solutions.