Dual-responsive ratiometric fluorescence detection of Ce4+ and ascorbic acid by regulating oxidase-mimicking activity of Ce4+-based nanocomplex

Herein, a dual-responsive ratiometric fluorescence sensor was developed for highly sensitive and accurate detection of Ce4+ and ascorbic acid (AA) by regulating oxidase-mimicking activity of Ce4+-based nanocomplex. Complexing with fluorescent polydopamine nanoparticles (FPDA NPs) and N-2-hydroxyethylpiperazine-N′-ethanesulfonic acid (HEPES) buffer was demonstrated to enhance the oxidase-mimicking activity of Ce4+, which greatly boosted the catalytic oxidization of 1,2-diaminobenzene (OPD) into fluorescent 2,3-diaminophenazine (DAP) with yellow emission. Meanwhile, the fluorescence of FPDA NPs with blue emission was effectively quenched owing to electron transfer effect and the inner filter effect. Contrastingly, with addition of AA, Ce4+ was chemically reduced to Ce3+ that without oxidase-mimicking activity and quenching property to FPDA NPs. Thus, the emission ratio of DAP to FPDA NPs should act as signal output for Ce4+ and AA detection. Benefiting from the dual-responsive ratiometric fluorescence technique with reverse change profile and the controllably catalytic oxidation activity of the nanocomplex, good performances for Ce4+ and AA detection in solution and in practical samples were achieved. This work not only expands the fluorescence sensing application of FPDA NPs but also offered a new sight for artificial enzymes research.