Gold-Nanoparticle-Encapsulated ZIF-8 for a Mediator-Free Enzymatic Glucose Sensor by Amperometry

A novel method has been developed for the encapsulation of gold nanoparticles (AuNPs) and glucose oxidase (GOx) together into the cavity of a zeolitic imidazolate framework (ZIF-8) in aqueous media and subsequently used for amperometric glucose sensing application. ZIF-8 is a highly efficient, stable (thermally and chemically) microstructure and possesses a large surface area with a unique cavity to accommodate both AuNPs and GOx. The as-synthesized composite is thoroughly characterized by various physicochemical methods and confirms the uniform distribution of AuNPs within the metal–organic framework cavity. The presence of highly conducting AuNPs enhances the activity of GOx and facilitates the mediator-free tandem electrocatalytic reactions of both glucose oxidation and oxygen reduction. Further, the nanocomposite exhibits admirable stability with low-level detection of glucose in aqueous media (50 nM glucose) by using a very low concentration of GOx (62 μg in 1 mL).