Enhancing photoluminescence stability of blue emissive nitrogen doped graphene quantum dots by encapsulating inside zeolitic imidazole framework-8

Abstract

Graphene quantum dots (GQDs) have emerged as promising materials for luminescence sensing in chemical and biological fields due to their excellent optical properties. However, their limited stability hinders their practical applications. To address this, we encapsulated the nitrogen doped GQDs (nGQDs) within zeolitic imidazole framework-8 (ZIF-8) via bottle-around-ship method, resulting in nGQD@ZIF-8 nanocomposites. This encapsulation process was conducted at room temperature and aimed to enhance the photo-, thermal, pH, and storage stability of nGQDs. Through nitrogen doping, the photoluminescence (PL) intensity of GQDs was greatly enhanced by 97.3%. The nGQD@ZIF-8 retained 93.5% and 91% of its initial PL intensity after continuous exposure of 12 h UV light, and heated to 90 °C, respectively. Moreover, the PL intensity of nGQD@ZIF-8 remained relatively constant within a broad pH range (pH 2 to pH 11) and after 3 months of storage. The ZIF-8 encapsulation efficiently provides surface passivation, minimizing surface defects and enhancing the stability of nGQDs. It also effectively shields the nGQDs under harsh conditions through confinement and framework protection. The exceptional properties of the resulting nGQD@ZIF-8 nanocomposite broaden its practical applicability in multifunctional fields such as bioimaging, chemical and biological sensing probes.