A smartphone-integrated ready-to-use paper-based sensor with mesoporous carbon-dispersed Pd nanoparticles as a highly active peroxidase mimic for H2O2 detection

In analytical science, it is always of great scientific and practical significances to explore convenient, rapid, and reliable methods/devices to trace the H 2 O 2 level in various matrices. Herein, we fabricated a ready-to-use paper-based chemosensor by using mesoporous carbon-dispersed Pd nanoparticles (Pd NPs/meso-C) as a promising peroxidase mimic for the visual determination of H 2 O 2 . Thanks to the large exposed surface of the meso-C support and the highly dispersed active Pd NPs, the synthesized Pd NPs/meso-C exhibited favorable catalytic performance to trigger the chromogenic reaction of colorless TMB to blue TMBox mediated by H 2 O 2 , providing a K cat of 326.67 s −1 for H 2 O 2 and 0.55 s −1 for TMB, larger than the bare Pd NPs and even comparable to the activity of natural horse radish peroxidase. As demonstrated, this principle could be employed to colorimetrically detect H 2 O 2 in the linear scope of 5–300 μM. By simply immobilizing the Pd NPs/meso-C mimic and the TMB substrate onto a common filter paper, ready-to-use paper-based sensors were further prepared. By combining these test strips with a smartphone and an easy-to-access color-scanning APP together, the integrated platform could be used for the quantitative analysis of H 2 O 2 with advantages of simple operation, fast response, low cost, and good selectivity and repeatability. Furthermore, reliable sensing of the target in milk matrices suggested great promise of the integrated platform in practical applications.