Ionic liquid capped white luminescent carbon dots: application in sensing and bioimaging

A new category of white luminescent materials, white-light-emitting carbon dots (CDs), has gained massive attention due to their exclusive features and potential applications. The complicated structure of CDs confuses the understanding of their photoluminescence (PL) mechanism, which is still unclear and a significant challenge to interpret the surface chemistry. This work compares the hydrothermal and ionic liquid (IL) solvothermal approaches to producing high-quality CDs. The modulation of solvent with IL and doping amount of nitrogen gives the white-light-emitting CDs. In particular, the CDs-IL exhibits novel and robust white PL performance. IL surface modification led to PL enhancement with a red shift from 543 nm to 620 nm and an increase in the quantum yield from 16.8 +/- 2% to 68.6 +/- 2%. The enhancement in PL of CDs-IL inspired us to utilize them as bioimaging probes on bacterial cell lines and sensing probes for water pollutants Fe3 thorn and trinitrophenol, lower the detection limit 0.117 +/- 0.010 mM and 0.049 +/- 0.005 mM. These results confirmed that IL capped on the surface functional group of CDs forms a stable structure surrounding the CDs. Our finding provides clear evidence for the surface chemistrydependent PL behavior of CDs.