Luminescent Carbon Nanoclusters for Sensitive Detection of Ascorbic Acid and Fluorescent Printing

Carbon nanoclusters (CNCs) is a kind of carbon-based luminescent nanomaterial between macromolecular substances and carbon quantum dots, which is a valuable potential probe for fluorescence sensing and biological imaging. Herein, a mild and fast contact route was established for synthesis of CNCs with strong green fluorescence at 516 nm. The method involves direct mixing of polyethyleneimine (PEI) solution with ascorbic acid (AA) at room temperature without any energy and time consumption. The CNCs were formed once PEI and AA solutions came into contact, which could be used to detect the presence of AA. The fluorescence intensity of the as-prepared CNCs was also quantitatively enhanced with the increase of AA. Therefore, a fluorescence "turn-on" method was developed for the sensitive detection of AA based on the formation of the CNCs in a linear range from 0.5 to 100 μM with a low limit of detection of 0.15 μM. This method was also successfully employed to detect AA in real samples of human plasma and cherry tomato with recoveries ranging from 97 to 105%. Due to the excellent fluorescence property and low toxicity of the as-prepared CNCs, they were also applied as a bright fluorescent ink for fluorescent printing.