Excitation dependent emission combined with different quenching manners supports carbon dots to achieve multi-mode sensing

In this paper, multi-mode sensing for the detections of methotrexate (MTX), rutin (RT), quercetin (QCT) and temperature were achieved by a type of highly fluorescent CDs, benefiting from an excitation dependent emission combined with different quenching mechanisms. The highly luminescent CDs were prepared by a simple hydrothermal pyrolysis of citric acid and monoethanolamine at 180 degrees C for 4 h with a high quantum yield of 46.6%, exhibiting an excitation dependent emission. An approach to the detection of MTX was built by using the CDs as a sensor under excitation at 370 nm based on the synergistic action of inner filter effect (IFE) and photo induced electron transfer (PET). Although the absorption spectra of RT and QCT both centered at 350 nm are entirely overlapped, the maximum absorption of QCT can be moved from 350 to 430 nm since it forms a coordination complex with Cu2+ under acidic condition. Assisted by Cu2+, detections of individual RT and QCT were therefore achieved by the CDs via IFE under excitation at 350 and 430 nm, respectively. Moreover, a nanosensor for temperature sensing was also fabricated according to temperature caused aggregation of the CDs and aggregation induced quenching effect. (C) 2018 Elsevier B.V. All rights reserved.