A fluorescent nanoprobe for 4-ethylguaiacol based on the use of a molecularly imprinted polymer doped with a covalent organic framework grafted onto carbon nanodots.

An efficient and rapid fluorescent nanoprobe is described for the determination of the aroma compound 4-ethylguaiacol (4-EG). A molecularly imprinted polymer was doped with a covalent organic framework (COF) grafted onto carbon nanodots that was prepared by one-pot reverse microemulsion polymerization. Amino groups at the surface of carbon nanodots coordinate to the COFs to produce a strong bond and this warrants thermal and chemical stability of the probe. Remaining free amino groups interact with the phenolic hydroxyl groups of 4-EG through acid-base pairing interactions. The probe, with excitation/emission maxima at 350/440 nm, responds to 4-EG due to the charge transfer to the carbon nanodots. Under optimized conditions, fluorescence drops linearly as the concentrations of 4-EG increase from 0.025 to 1 μg mL-1, with a detection limit of 17 ng mL-1. The probe was applied to the determination of 4-ethylguaiacol in Chinese Baijiu and wine samples after pretreatment by a single dilution step. The recoveries of spiked samples ranged from 78.4to 110.1%. Graphical abstract Schematic presentation of the synthesis of a fluorescent nanoprobe based on molecularly imprinted polymers doped with covalent organic framework grafted onto carbon nanodots. It was used as an efficient and rapid nanoprobe for 4-ethylguaiacol detection with high selectivity and sensitivity.