Nitrogen-Doped Graphene Quantum Dots Anchored on Hollow Zeolitic Imidazolate Framework-8 Colloidosomes for Fluorescence Detection of Glucose

Hollow-structured nanomaterials, featuring a porous crystalline structure and hollow interior, are conducive to achieving a compartmentalized architecture comprising diverse functional entities. In this study, we have constructed a novel fluorescent enzyme nanocomposite derived from the nanosized hollow ZIF-8 (H-ZIF-8) colloidosomes via a diffusion strategy. Insights into the underlying mechanisms revealed that the diffusion process was driven by mesopore properties and electrostatic interactions. It has also been demonstrated that the molecular sieving property of the colloidosome shell induced an exceptional compartmentalized structure, where nitrogen-doped graphene quantum dots (N-GQDs) were anchored onto the outer surface of the nanosized H-ZIF-8 colloidosomes, whereas glucose oxidase (GOx) was homogeneously encapsulated in the entire cavity. The resultant nanocomposite inherited the mesopore properties of the colloidosome exoskeleton, catalytic ability of GOx, and fluorescence properties of N-GQDs. In particular, the porous properties of the nanosized H-ZIF-8 colloidosomes favored enrichment to target analytes, whereas the compartmentalized GOx and N-GQDs served as a "promoter" (initiate the biochemical reaction) and "signal unit" (intuitive observation) in the glucose probing system, respectively. Furthermore, anchoring N-GQDs onto the outer surface of the nanosized H-ZIF-8 resulted in tailoring of the fluorescence property of the nanocomposite. In the part of glucose sensing, the proposed fluorescence nanosensor could well quantify glucose within a range of 10 to 100 mu M with a lower limit of detection of 5.4 mu M. This proposed strategy presents opportunities to engineer novel metal-organic framework-based multifunctional nanocomposites and create new applications by combining their unique functions.