Portable paper-based sensing platform based on cerium dioxide-coated metal-organic framework nanozymes for rapid point-of-care pH indication

Abstract

In the study, ZIF-67 nanomaterials loaded with cerium dioxide nanozymes (ZIF-67@CeO2) were synthesized by a friendly chemical deposition method and solvothermal route, which possessed significant peroxidaseand catalase-like activities. Interestingly, the prepared bimetallic Ce-doped cobalt-based MOFs nanozymes promoted H2O2 adsorption (HOOHad), catalysis, and rapid electron transfer at the metal sites for the generation of hydroxyl radical (center dot OH) due to the bimetallic synergistic effect. Additionally, steady-state kinetic studies demonstrated that ZIF-67@CeO2 had higher affinity for H2O2 and TMB (smaller Km values of 0.058 mM and 0.94 mM, respectively), even when compared with natural horseradish peroxidase (HRP) and other metal-based nanozymes. Furthermore, a multi-color changing portable smart paper-based sensing device was designed based on the peroxidaselike property of ZIF-67@CeO2 nanozymes for colorimetric detection of pH in point-of-care (POC) manner. This work not only synthesizes a bimetallic nanozyme with multiple enzyme-like properties and develops a simple and rapid strategy for indicating pH, but also provides a new approach for POC clinical disease diagnosis and food safety monitoring.