A Carbon Dots Probe for Specific Determination of Cysteine based on Inner Filter Effect

Carbon dots ( CDs ) with yellow-green fluorescence were synthesized by using m -aminophenol and ethylenediamine under mild conditions and applied as a sensor for detecting cysteine ( Cys ). Cys reacted with p -nitrophenyl acrylate via Michael addition and cyclization to form p -nitrophenol ( PNP ) which had the UV absorption maximum at 405 nm. PNP quenched the fluorescence of CDs at the excitation wavelength of 420 nm based on inner filter effect. The fluorescence intensity change of CDs was used as an output signal for Cys detection. The probe detected Cys over homocysteine and glutathione in a solution with high selectivity. The system was highly sensitive to Cys with low limit of detection of 0.8 μM and showed a good linear relationship in the range of 1–50 μM. This carbon dots probe has the potential to be applied in biological analysis.