A molybdenum disulfide quantum dots-based ratiometric fluorescence strategy for sensitive detection of epinephrine...

In this paper, a novel and sensitive ratiometric fluorescence strategy for the detection of epinephrine (EP) and ascorbic acid (AA) was established based on the fluorescence resonance energy transfer (FRET) between the molybdenum disulfide quantum dots (MQDs) and the fluorescent oxidative polymerization product (P_EP-PEI) of EP in polyethyleneimine (PEI) aqueous solution. The continuous formation of P_EP-PEI can lead to the fluorescence quenching of MQDs at 414 nm while the fluorescence of P_EP-PEI at 522 nm gradually increased. The introduction of AA can inhibit the oxidative polymerization process of EP due to the strong reducibility of AA, resulting in the fluorescence recovery of MQDs at 414 nm and the fluorescence decreasing of P_EP-PEI at 522 nm. Therefore, EP and AA can be monitored by measuring the ratio of the fluorescence intensities at 522 nm and 414 nm. A good linear calibration of I₅₂₂/I₄₁₄ versus EP and AA concentrations were obtained within 0.2-40 μM and 0.5-40 μM, respectively. And the detection limit was 0.05 μM for EP and 0.2 μM for AA. Furthermore, the developed ratiometric fluorescence method with high sensitivity and selectivity was applied for EP in human urine samples and AA in human serum samples determination with satisfactory results obtained.