Ratio fluorescence sensor based on CD/Cu-MOFs for detection of Hg2.

Trace detection of toxic heavy metals is a very important and difficult problem in several areas: convenience, sensitivity, and reliability. Herein, we develop an innovative fluorescence resonance energy transfer (FRET)-based ratio fluorescence sensor for the detection of heavy metal mercury ion (H g 2+). The sensing platform is composed of coumarin derivatives (CDs) and a copper metal-organic framework (Cu-MOF) named CD/Cu-MOF. The constructed CD/Cu-MOFs ratio fluorescence sensor exhibits dual emission peaks at 430 and 505 nm under the single excitation wavelength of 330 nm. With the addition of H g 2+, the fluorescence intensity of the system at 430 nm gradually increased, and the fluorescence intensity at 505 nm remained stable, resulting in a change in the fluorescence ratio. There is a good logarithmic relationship between the H g 2+ concentration in the range from 2×10-8 to 0.001 nM and the ratio of the fluorescence emission intensity of the system (F 430/F 505) (R 2=0.9901), and its calculated detection limit is 3.76×10-9 n M. In addition, the CD/Cu-MOFs ratio fluorescence sensor has achieved a good recovery rate of standard addition in the actual food sample recovery experiment, which provides an effective method for the detection of H g 2+ in food samples.

One-step synthesized fluorescent nitrogen doped carbon dots from thymidine for Cr (VI) detection in water.

A novel, simple and low-cost nitrogen doped carbon dots (N-CDs) fluorescent sensor for sensitive detection of Cr (VI) was developed via one-step hydrothermal method using thymidine as carbon source. As-prepared N-CDs exhibited the ability of sensitive and selective detection of Cr (VI) through the inner filter effect (IFE). The performances of N-CDs were investigated with the characterization methods of transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Under the optimized conditions, a good logarithm correlation between the fluorescence intensity of N-CDS and the concentration of Cr (VI) was obtained ranging from 0.1 µM to 430 µM (R2 = 0.992), with a low detection limit (LOD; S/N = 3) of 1.26 nM. The fluorescent sensor showed good repeatability, reproducibility and stability. Furthermore, N-CDs fluorescent sensor had a good applicability for Cr (VI) detection in real water samples with acceptable recoveries, and the detection results were consistent with the inductively coupled plasma mass spectrometry (ICP-MS) results, indicating this fluorescent sensor has a great potential for the environmental monitoring.