Application of maleimide modified graphene quantum dots and porphyrin fluorescence resonance energy transfer in the design of ‘‘turn-on’’ fluorescence sensors for biothiols

Two novel fluorescent probes were designed to detect the biothiol in foods using the highly efficient Michael addition reaction between maleimide-derived probes and the biothiol. First, maleimide functionalized GQDs (M-GQDs) were synthesized and used for biothiol identification according to the Michael addition principle. The biothiol can be detected in the range of 5 × 10 −9 to 4 × 10 −7  mol/L and the detection limit was 1.69 × 10 −9  mol/L. Then, a fluorescence resonance energy transfer (FRET) system between M-GQDs and tetrakis (4-aminophenyl) porphyrin (TAPP) for biothiol detection was developed. However, the process of FRET was switched off in the presence of biothiols due to the switch of M-GQDs fluorescence emission to the“ON” mode following the Michael addition mechanism. The system could quickly and accurately detect the biothiol with a detection range of 6.7 × 10 −10 to 2 × 10 −7  mol/L and a detection limit of 2.34 × 10 −10  mol/L. Compared to the single detection system, the FRET system had a wider detection range and lower detection limit, and the related biomolecules did not interfere with the quantitative identification of the biothiol. The proposed method was successfully applied for the determination of the biothiol in foods and human blood samples.