Synergistic Pd/Pt Bimetallic Nanozyme with 3D Hollow Architecture for Ultrasensitive H2O2 Detection in Complex Food Matrices

Precise structural modulation of Pt-based nanozymes is an effective strategy to enhance the catalytic performance for biochemical sensing. Herein, we report three-dimensional (3D) hollow nanospheres (HNPs) featuring highly dispersed Pd/Pt atomic sites as an efficient peroxidase mimic. The Pd/Pt-HNPs exhibit markedly enhanced peroxidase-like activity, which we attribute to the synergistic catalysis of bimetallic active centers combined with the hollow 3D architecture. Kinetic analysis reveals a Vmax of 20.29 × 10–8 M·s–1, corresponding to an activity ∼10-fold higher than that of Pd-HNPs and ∼1.6-fold higher than that of Pt-HNPs. Notably, the Kcat reaches 5.44 × 105·s–1, which is approximately 103-fold greater than that of horseradish peroxidase (HRP) under the same assay conditions. Leveraging this excellent catalytic efficiency, we established an ultrasensitive colorimetric platform for H2O2 quantification (limit of detection (LOD): 1.14 μM by calculation; visual limit of detection (vLOD): 2.5 μM by naked-eye inspection), exhibiting a detection range from 2.5 μM to 12.8 mM. The Pd/Pt-HNPs-based method delivers a sensitivity 55 and 13-fold higher than those of HRP and a confirmatory method, respectively. The assay further demonstrates reliable accuracy in complex food matrices (milk, dried bean curds, and chicken feet), affording good recovery rates (91.36–115.71%) with a coefficient of variation in the range from 4.06 to 15.41% and low susceptibility to interference. This study highlights the synergistic effect of Pd/Pt bimetallic sites and nanoengineering in enhancing nanozyme catalysis, enabling sensitive and reliable detection in complex food matrices.