Highly efficient fluorescence switching of carbon nanodots by CO2

In recent years, carbon nanodots (CDs) have attracted increasing attention in many applications because of their superior optical and chemical properties. To manipulate CDs properties for their smart applications, CDs with CO 2 switchable luminescence property have been designed and prepared in the present work. It is found that fluorescence of the polyamine-functionalized CDs can be switched “off” and “on” in DMSO-water mixture by alternatively bubbling and removal of CO 2 . 13 C NMR spectra suggest that the mechanism behind the fluorescence “on-off” results involves the reversible acid-base reaction of the functionalized CDs with CO 2 and the formation of hydrophilic polyammonium bicarbonates. Due to the poor solubility of polyammonium bicarbonates in DMSO-water mixture, the formation of the polyammonium bicarbonates precipitation, by CO 2 bubbling, decreases the concentration of the functionalized CDs in aqueous DMSO, leading to the switch off of the fluorescence. When CO 2 is removed by N 2 bubbling, the precipitation is returned to the DMSO-water mixture, and thereby the fluorescence is switched on again. Based on this novel CO 2 -switchable photoluminescence property, the functionalized CDs have been used for the quantitative detection of CO 2 and SO 2 in aqueous solution and in the air.