Synergistic Pd/Pt Bimetallic Nanozyme with 3D Hollow Architecture for Ultrasensitive H ₂ O ₂ 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 V max 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 K cat reaches 5.44 × 10 5 ·s –1, which is approximately 10 3 -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 H 2 O 2 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.