Fluorescent carbon quantum dots for simple and fast detection of Cyanocobalamin

Vitamin B12 (cyanocobalamin) is a water-soluble vitamin containing a cobalt ion within tetrapyrrole ring and belongs to group B vitamins. This vitamin is an important coenzyme for cell development and growth, and it plays a key role in the normal functioning of the brain and nervous system[1]. Various analytical techniques have been employed for the determination of vitamin B12. However, the applications of these methods are limited due to time-consumption, high cost, the need of sophisticated instrumentations, low reproducibility and insufficient sensitivity[2]. In recent years, considerable attention has been paid to the synthesis and application of carbon quantum dots (CDs), due to their outstanding tunable multi-color photoluminescence (PL) properties, high chemical stability, low toxicity, biocompatibility, and easy functionalization[3]. In this work We testified that N,S-doped CDs can serve as a very effective photoluminescence probe for detection of vitamin B12. Carbon nanoparticles were synthesized from the mixture of glucose and cysteamine. Glucose served as the carbon source, and the cysteamine provided nitrogen and sulfur. Co-doped carbon dots were characterized by X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and Fourier transform infrared (FTIR) spectroscopy techniques. Briefly, the co-doped carbon dot systems showed quenching of photoluminescence intensity in the presence of vitamin B12. Functional group and doping heteroatoms were impact on the selectivity and sensitivity. The decrease of fluorescence intensity made it possible to analyze vitamin B12 with satisfactory detection limits and linear ranges. The Sterne–Volmer plot showed a linear relationship between F0/F and the concentration of vitamin B12 over the range from 0 to 10 µM with a detection limit of 0.07 µM.