A kind of nitrogen doped carbon quantum dots(N-CDs) with high stability

good water solubility were prepared by one-step microwave method with citric acid as carbon source and urea as nitrogen source.The prepared N-CDs were characterized by transmission electron microscopy(TEM)

atomic force microscopy(AFM)

X-ray photoelectron spectroscopy(XPS) and infrared spectroscopy(IR).Results showed that the N-CDs contained a particle size ranging from 0.5 nm to 5 nm with an average particle size of 2.6 nm

which were rich in hydroxyl

carboxyl and amino groups and other functional groups.The N-CDs were used in the detection of dopamine.Under the selected experimental conditions

there was a good linear relationship for the fluorescence quenching efficiency(IF/IF0) of N-CDs with dopamine within the concentration range of 25-375 μmol/L

and the method detection limit was 0.08 μmol/L.This method was applied in the detection of dopamine in urine of normal people with high accuracy and satisfactory results.The average recoveries ranged from 995% to 106% with relative standard deviations(RSDs) of 1.8%-2.3%.