Pd Nanoclusters Confined in ZIF-8 Matrixes for Fluorescent Detection of Glucose and Cholesterol

Nanomaterials possessing intrinsic enzyme-mimetic activity are becoming an important topic of current research. However, their enzyme-mimetic activity is limited by the particle size of the nanomaterials. In this study, Pd nanoclusters with an average size of 1.4 nm are synthesized by using a metal organic framework, zeolitic imidazolate framework-8 (ZIF-8), as a matrix via an impregnation-reaction method. By virtue of the confined channels of ZIF-8 and the strong chemical interaction between the Pd nanoclusters and ZIF-8 framework, the Pd nanoclusters show a high dispersity and stability. The obtained Pd@ZIF-8 is proven to have enhanced intrinsic peroxidase-like activity, showing Michaelis–Menten constants (Km) as high as 0.13 mM for 3,3′,5,5′-tetramethylbenzidine and 14.02 mM for hydrogen peroxide. Colorimetric testing and electron spin resonance spectra reveal that radicals are generated during the catalytic process of peroxidase-like Pd@ZIF-8 toward H2O2. With the addition of glucose or cholesterol oxidase, the Pd@ZIF-8 can be utilized to construct a highly selective and sensitive fluorescent sensor for glucose and cholesterol, exhibiting a detection limit of 0.10 and 0.092 μΜ, respectively. Additionally, the proposed fluorescent platform exhibits the capability to detect glucose and cholesterol in serum samples with satisfactory recovery, indicating potential application prospects in biochemical analysis.