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

Abstract

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.