A redox-regulated inner filter effect between Ti₃C₂ quantum dots and MnO₂ nanosheets for sensitive alkaline...

As a well-established disease biomarker, alkaline phosphatase (ALP) plays a pivotal role in hydrolyzing phoshporylated biomolecules and exhibits significant value in clinical diagnosis. Herein, a novel and sensitive fluorescent assay was constructed for ALP sensing through a redox-regulated inner filter effect (IFE) occurred between Ti₃C₂ MXene quantum dots (Ti₃C₂ QDs) and MnO₂ nanosheets. Blue emitted Ti₃C₂ QDs with a quantum yield of 14.4% were synthesized through a top-down method. The fluorescence of Ti₃C₂ QDs was efficiently quenched by MnO₂ nanosheets based on the IFE between the two. Ascorbic acid disphosphate (AAP) could be hydrolyzed into AA by ALP. The redox reaction between the generated AA and MnO₂ nanosheets converted MnO₂ to Mn²⁺, triggering the fluorescence recovery of Ti₃C₂ QDs. Thus, sensing ALP was realized by a fluorescence turn-on mode. The Ti₃C₂ QDs/MnO₂ nanosystem exhibited favorable analytical performance towards ALP sensing. A wide linear range (0.05-10 mU/mL) and a low detection limit (0.014 mU/mL) were achieved by the assay. Moreover, practicality of the assay was also confirmed by measuring ALP levels in real biological samples. This work will broaden the use of Mxene QDs in biosensing applications.