Rapid synthesis of multifunctional carbon nanodots as effective antioxidants, antibacterial agents, and quercetin nanoprobes

A facile and rapid synthesis of multifunctional carbon nanodots (CNDs) was developed by using the acid-base neutralization spontaneous heat with glucose as precursor, 1,2-ethylenediamine (EDA) and concentrated nitric acid as dual N-dopants. The CND has a tremendous antioxidant potency, which represents effective inhibitory concentrations of reactive oxygen species that are significantly lower than ascorbic acid. Furthermore, minimum inhibitory concentration (MIC) assay revealed CNDs possessed significant antimicrobial activity for Gram-positive S. aureus and Gram-negative E. coli. Moreover, the CNDs are endowed with favorable fluorescence (FL) behaviors including the quantum yield (QY) of 14.2% and stable FL within a wide range of pH and high tolerance to external ionic strength, rendering them applicable in quercetin (QCT) detection as a FL nanoprobe. The CNDs were effectively quenched by QCT due to static quenching which takes place by the electrostatic interaction between basic groups of CNDs and QCT of 3-hydroxyl. This nanoprobe had profitable selectivity and sensitivity towards QCT with a linearity ranging from 1 μM to 47 μM and a low detection limit of 172.4 nM and were successfully performed for QCT detection in human serum and urine samples.