A label-free multifunctional nanosensor based on N-doped carbon nanodots for vitamin B12and Co2+detection, and bioimaging in living cells and zebrafish

Multifunctional N-doped carbon nanodots (N-CNDs) with a fluorescence (FL) quantum yield (QY) of 13.6% have been synthesizedviaa facile one-step hydrothermal process usingArtemisia annuaand 1,2-ethylenediamine as precursors. As-prepared N-CNDs showed excellent FL properties and were developed as a multifunctional sensing platform for vitamin B-12(VB12) and Co(2+)determination, and bioimaging in living cells and zebrafish. The FL of N-CNDs is quenched efficiently in the presence of VB(12)on the basis of the inner filter effect (IFE) or Co(2+)by static quenching, respectively. EDTA as a masking agent enables Co(2+)to be effectively eliminated and N-CNDs were used to selectively detect VB(12)in the presence of both VB(12)and Co2+. The present FL nanosensor can detect VB(12)and Co(2+)in the linear ranges of 0.5-35 mu M and 2.5-25 mu M with the corresponding detection limits of 47.4 nM and 230.5 nM, respectively. The study proved that the determination of Co(2+)was based on the static quenching to form a complex between the amino group of N-CNDs and Co2+. Inspired by these outstanding properties, practical applications of this nanosensor for the detection of VB(12)in actual samples (human serum, egg yolk, VB(12)tablets and VB(12)injection) and Co(2+)in water samples were further verified with satisfactory results. The as-constructed N-CNDs have negligible toxicity and good biocompatibility, which facilitates utilization of N-CNDs in bioimaging of A549 cells and zebrafish, and sensing VB(12)in living cells.