Enhanced fluorescent effect of graphitic CN@ZIF-8 nanocomposite contribute to its improved sensing capabilities.

A novel graphitic carbon nitride (g-CN)@ZIF-8 nanocomposite was synthesized by a facile approach and applied as a fluorescent sensor. The fluorescent quenching and enhancing effect of g-CN@ZIF-8 nanocomposite was explored for potential applications in sensing metal ions and solvents based on photoluminescence (PL) measurements. Compared with g-CN nanosheets alone, the combined g-CN@ZIF-8 nanostructure greatly improved the sensitivity for the detection of metal ions due to the special fluorescent quenching effect. In particular, the sensitivities of the detection of Cu and Ag improve from 29.1 to 11.2 ppm and from 40 to 16.5 ppm, respectively, which were significantly improved compared to that of g-CN nanosheets alone. The sensitivity could increase about 100% and 250% for Cu and Ag by the g-CN@ZIF-8. The limit of detection (LOD) for Cu and Ag by g-CN@ZIF-8 was 11.2 ppm and 13.2 ppm, respectively. Both g-CN nanosheets and g-CN@ZIF-8 nanocomposite can be used for distinguishing Fe and Fe in solutions. The LOD of Fe by g-CN@ZIF-8 was as low as 65.4 ppm. On the other hand, the relative increased luminescence of g-CN@ZIF-8 to the g-CN in tetrahydrofuran (THF) was selective, which was successfully applied for detecting this specific solvent. An excellent linear relationship (0-1.0 v/v of THF/water) between the THF fraction and PL intensities was obtained. These results demonstrate that the g-CN@ZIF-8 nanocomposite provide a convenient and novel approach for the enhance fluorescence detection of metal ions and distinguishing of specific solvents.