Ultrathin PtTeNi nanosheets as a peroxidase mimic for colorimetric detection of ascorbic acid

Utilizing the peroxidase (POD) activity of nanozymes to construct the colorimetric sensors is a popular strategy for assessing the antioxidant capacity of biological molecules, but the detection sensitivity is often compromised by their low enzymatic activity. Pt-based nanozymes, favored by their regulated nanostructures, well provide numerous binding sites for H2O2, and exhibit enhanced POD performance. Here, we utilized a simple hydro- thermal method to synthesize PtTeNi nanomaterials featured with the ultrathin sheets for detecting biological antioxidant (ascorbic acid (AA) as the model). With the TMB-H2O2 system as the colorimetric substrate, PtTeNi nanomaterial exhibited superior POD-like activity with a higher Vmax (5.02 x 10-4 mM s-1) and lower Km (3.14 mM)) in contrast to natural HRP. AA significantly inhibited the colorimetric reaction of PtTeNi-TMB-H2O2 system via competitively binding center dot OH generated by PtTeNi-mediated H2O2 catalysis and further blocking oxTMB formation. Inspired by this fact, the PtTeNi-TMB-H2O2 colorimetric sensor successfully realized highly sensitive and selective detection of AA with a good linear range from 5 mu M to 500 mu M and the detection limit of 2.94 mu M. For analyzing the total antioxidant capability and AA contents in actual samples (commercial drinks and vitamin C tablets), the PtTeNi-based colormetric method displayed comparable results with the commercial total antioxidant capacity assay kit, with the advantages of easy operation, convenient storage and high stability. This work fully affirms the excellent enzyme-like performance of Pt-based nanomaterial and confirms the feasibility of nanozymes-based colorimetric sensing strategy in detecting antioxidant capability of biological molecules.