Low temperature synthesis of highly stable phosphate functionalized two color carbon nanodots and their application in cell imaging

Phosphate functionalized carbon nanodots (C-dots) with satisfactory quantum yield have been prepared through one-step acidic oxidation of sucrose by H3PO4 at low temperature (60 °C). The as-prepared C-dots are monodisperse with narrow size distribution. Besides, two C-dots emitting different colors, namely green and yellow, can be easily separated by collecting the supernatant and precipitate after neutralization and centrifugation. Both C-dots show good photoluminescence properties over a very wide pH range (2.0–13.0). Moreover, they exhibit high tolerance to various external conditions, such as high ionic strength, external cations and UV excitation. The obtained C-dots can be internalized by cells without post surface passivation and they exhibit minimum toxicity as well as favorable biocompatibility. The highly stable, phosphate functionalized and two color C-dots with narrow size distribution are expected to have great potential application in bioimaging and bioanalysis.