Carbon dots coated with vitamin B12 as selective ratiometric nanosensor for phenolic carbofuran

[Display omitted] •CQDs@VB12 were shown as a fluorescent sensors of phenolic carbofurans for the first time.•The coating effect resulted in a dual emission at 417 and 550nm.•The sensor response is based on the fluorescence quenching by phenolic carboufuran.•The detection limit toward carbofuran phenol 3-Keto pesticide is 12.2μM.•Good accuracy of detection when tested in soy sauces was found. A carbon quantum dots (CQDs) based ratiometric nanosensor exhibiting dual emission fluorescence was developed. The spherical fluorescent carbon nanoparticles were obtained from lactose using a hydrothermal method. Under a single excitation at 355nm they showed the typical blue emission at 417nm and a red emission at 550nm attributed to the coating effect of vitamin B12. The latter is explained by the fluorescence resonance energy transfer (FRET) and it consists of 61% of total emission. Upon the presence of carbofuran phenol 3-Keto, a phenolic metabolite of carbofuran, the red emission was quenched, resulting in a ratiometric fluorescence response in the blue range. This ratiometric nanosensor exhibited a good selectivity to carbofuran phenol 3-Keto. The ratio of I417/I550 linearly decreased with an increasing carbofuran phenol 3-Keto concentration in the range 9.8μM–1.40×10−4M. A detection limit for carbofuran phenol 3-Keto pesticide was 12.2μM. The pesticide tested was extracted from soy sauce. Recovery values ranged from 98% to 114% with RSD values from 1.50% to 6.50%.