Novel "on-off" fluorescence sensing for rapid and accurate determination of Cr³⁺ based on g-CNQDs

Cr³⁺ is one of the most essential trace elements in living organisms and plays a vital role in human metabolism. However, both deficiency and excess intake of Cr³⁺ can be harmful to the human body. Therefore, the quantitative determination of Cr³⁺ is of great significance in the field of life science. Based on this, in this study, a g-CNQDs@p-acetaminophenol fluorescence sensing system was developed for the quantitative detection of Cr³⁺ in actual complex samples. G-CNQDs were synthesized with sodium citrate and urea as precursors. The fluorescence signal was enhanced by the synergistic effect between p-acetaminophenol (APAP) and g-CNQDs. The fluorescence quenching phenomenon can be produced when Cr³⁺ is introduced into the fluorescence-enhanced g-CNQDs@p-acetaminophenol system. An "on-off" fluorescence sensing system was constructed based on g-CNQDs@p-acetaminophenol for the quantitative detection of Cr³⁺. The experimental data showed a wide linear region in the concentration range of 0.64-63.0 μM, and the detection limit was as low as 0.23 μM. The construction of the sensor system broadens the research field for the practical application of Cr³⁺.