Green anhydrous synthesis of hydrophilic carbon dots on large-scale and their application for broad fluorescent pH sensing

A green and convenient anhydrous method was developed to synthesize hydrophilic carbon dots (H-CDs) on large-scale in this work. During the whole process of preparation, toxicity materials and high pressure conditions were not used, and H-CDs can be formed in several minutes by directly putting glucose powder into hot edible oil, which can be used again. Therefore, it is a green method and very suitable for the industrial preparation of CDs on large-scale. Characterizations demonstrate the H-CDs possess excellent optical properties, higher photostability and very low cytotoxicty. Noticeably, the H-CDs exhibit a distinct pH-sensitive feature, and have been used to construct fluorescent pH sensor with a nice linear relationship in the pH range of 3.0-13.0. To the best of our knowledge, this is the broadest reported pH range based on carbon dots without heteroatom doped. The mechanism of pH-sensitive response was also discussed. The proposed pH sensor has been successfully used for the pH monitoring of environmental water samples and living cells, which demonstrates their applicability in complex matrixes. (C) 2017 Elsevier B.V. All rights reserved.