Carbon dot/carbon nitride composites fluorescent probe for the highly selective detection of Cr(VI) ions

Fluorescence quenching of carbon dots (CDs) has been widely used for ions detection, but it usually exhibits poor selectivity for specific ions, so how to enhance their response selectivity is still an urgent task. In this paper, CDs and carbon nitride (C 3 N 4 ) nanosheets are prepared by pyrolysis and thermal oxidation method, respectively, followed by their ultrasonic mixing to synthesize CDs/C 3 N 4 composites. They are characterized by transmission electron microscope, X-ray diffractometer, X-ray photoelectron spectrometer, Fourier transform infrared spectroscopy, UV–vis and fluorescence spectrophotometer. The synthesized CDs and C 3 N 4 nanosheets both exhibit strong fluorescence response to multiple ions. As a comparison, CDs/C 3 N 4 composites exhibit highly enhanced selectivity to Cr 6+ as a result of partial consumption of -NH 2 groups and C N bonds or their reduced binding ability. Meanwhile, our CDs/C 3 N 4 probe exhibits high sensitivity of 54 %, short response time of less than 1 min, low detection limit of 0.39 μM, wide linear response interval of 2.0−80.0 μM and high stability.