Dual enzyme-mimicking fluorescent amino terephthalic acid/CuFe/adenosine triphosphate nanoparticles for determination of H2O2 and ascorbic acid

Abstract

Many nanozymes have been synthesized, though, it is still necessary to rationally synthesize multifunctional nanozymes for diverse applications. Herein, we fabricate three fluorescent nanozymes with peroxidase- and laccase-like activities under moderate conditions. Three nanozymes, NH2BDC/CuFe/ATP (NPs-1), NH2BDC/CuFe/ADP (NPs-2), NH2BDC/CuFe/AMP (NPs-3), are constructed based on three adenosine phosphates coordinated transition metal ions (Cu2+ and Fe3+) and adsorbing fluorescent amino terephthalic acid (NH2-BDC). They exhibit different laccase-like activity, which may result from the difference in steric configurations of nanozymes. Among them, NPs-1 possesses high peroxidase-mimicking activity and stability. Interestingly, o-phenylenediamine (OPD) is oxidized to 2,3-diaminophenazine (DAP) by ·OH which NPs-1 catalyzes H2O2 to produce. The fluorescence of NPs-1 (λem = 445 nm) is effectively reduced based on the inner filter effect between DAP and NPs-1, which recovers after adding AA. Based on stable fluorescence and high peroxidase-like activity of NPs-1, a system for determining H2O2 and AA is established in linear ranges of 2.0–200.0 and 4.0–300.0 μmol L−1 with limits of detection of 1.82 and 2.92 μmol L−1. The fluorescent probe shows a good performance in detecting AA in real samples. Furthermore, NPs-1 is applied in smartphone-based detection of AA by measuring its intrinsic fluorescence. This work provides a facile strategy for the design of multi-functional nanozymes.