One-pot hydrothermal synthesis of boron and nitrogen co-doped carbon dots for copper ion assay and multicolor cell imaging using fluorescence quenchometric method

Abstract

Boron and nitrogen co-doped carbon dots (B,N-CDs) with a high quantum yield (QY, 25.3%) and strong fluorescence (FL) performance is prepared through one-pot hydrothermal method using folic acid as the source of nitrogen and carbon, glycerol as the source of carbon, and borax as the source of boron. B,N-CDs has uniform dispersion with the average size of 5.1 ± 0.8 nm. The fluorescence of B,N-CDs is gradually quenched upon sequential addition of copper ion (Cu2+). And a linear relationship is observed in the range of 0.005–5 μM with a detection limit of 1.6 nM. The unique quenching of fluorescence (measured at excitation/emission wavelengths of 365/442 nm) is attributed to the selective capture of Cu2+ by the amino and amide groups on the surface of B,N-CDs. The amino group on the surface of B,N-CDs complex with Cu2+ to split the d orbital of Cu2+. This causes the excited state electrons from B,N-CDs transfer to the d orbital of Cu2+ and quenched the fluorescence. B,N-CDs display satisfactory stability, anti-interference performance and low cytotoxicity performance. It is successfully applied to the determination of Cu2+ in actual water samples. B,N-CDs treated cells display distinguished blue and green colors under a confocal microscope.