Glutathione modified N-doped carbon dots for sensitive and selective dopamine detection

The water-soluble N-doped carbon dots (NCDs) are designed by simple hydrothermal treatment of aqueous mixture of citric acid and urea. The initially prepared NCDs are further been passivated by l-glutathione (GSH) through carbodiimide-activated coupling reaction to enhance the emissive properties of the NCDs. The as-obtained passivated carbon dots (GSH-NCDs) show intense blue emission at 440 nm when excited at 355 nm. However, this emission is observed to be quenched selectively in the presence of dopamine (DA) leading to design a platform for DA detection. The quenching of fluorescence of GSH-NCDs is dependent on DA concentration. The limit of detection is 1.01 nM, with a linear detection ranges from 20 nM to 10 μM (R2 = 0.992). The average lifetime values and the spectral profile of GSH-NCDs in absence and presence of DA indicate the possibility of photoinduced electron transfer assisted inner filter effect mechanism for the DA induced quenching of GSH-NCDs’ fluorescence. Further experiments show that the as-designed DA detection technique works successfully for biological fluids.