Selective detection of Cu2+ using nitrogen-doped carbon dots derived from humic acid and urea based on specific inner filter effect

Abstract A new kind of nitrogen-doped carbon dots (N-CDs) was synthesized via a simple hydrothermal strategy using humic acid as the carbon source and urea as the nitrogen source. The fluorescence intensity of as-prepared N-CDs was quenched significantly in presence of Cu2+ based on a specific inner filter effect, which could be utilized to construct a selective sensor for monitoring Cu2+ in aqueous samples. The sensor exhibited good linearity over the range of 0.1–2 μM, and high sensitivity with a detection limit of 25 nM. Under the optimal conditions, there was no significant interference by other metal ions such as Cd2+, Al3+, Cr3+, Fe3+, Pb2+, Na+, Ni+, Fe2+, Ba2+, Ca2+, Co2+, Mg2+, As3+, K+, Zn2+ for Cu2+ detecting except Hg2+. The interference of Hg2+ can be masked by addition of sodium chloride. The experimental results demonstrated that the prepared N-CDs owned strong fluorescence, high monodispersity, good stability and good water solubility, and the constructed sensor had many advances and great application prospect in environmental field.