A green emissive carbon-dot-based sensor with diverse responsive manners for multi-mode sensing.

Since different quenching mechanisms can endow carbon dots (CDs) with diverse responsive manners, multi-mode sensing can in principle be achieved by a single carbon-dot-based sensor. In this work, green emissive CDs were prepared by simple hydrothermal pyrolysis of phenolphthalein and ethylenediamine at 180 °C for 5 h, with a quantum yield of 17%. The as-prepared CDs can be selectively quenched by Hg2+ due to their specific binding affinity causing photo-induced electron transfer (PET). Due to the inner filter effect (IFE), the CDs also showed intensive fluorescent response to lemon yellow dye. Moreover, the CDs responded to Fe2+ or H2O2 selectively in the presence of H2O2 or Fe2+ owing to oxidative quenching (OQ) by hydroxyl radicals resulting from the Fenton reaction. Via the diverse responsive manners of PET, IFE and OQ, multi-mode sensing for Hg2+, lemon yellow and Fe2+, H2O2 was thus achieved by a single green emissive carbon-dot-based sensor. Accordingly, the linear ranges for the selective detection of Hg2+, lemon yellow, Fe2+ and H2O2 were found to be 0.0-500.0, 0.0-20.0, 0.0-90.0 and 0.0-50.0 μM, with the limits of detection as low as 5.8, 0.5, 1.2 and 1.1 μM, respectively.