Highly sensitive fluorescent nitrobenzene gas sensing by nitrogen-doped graphene quantum dots embedded in ZIF-8 nanocomposite

This study introduces a straightforward and highly sensitive luminescence gas sensor designed for the detection of nitrobenzene in gaseous state. The sensor utilizes an innovative composite composed of nitrogen doped graphene quantum dots (nGQDs) as luminescent materials, successfully encapsulated within the stable porous carrier zeolitic imidazolate framework -8 (ZIF-8). The resulting nGQD@ZIF-8 nanocomposite showed highly sensitive luminescence sensing towards nitrobenzene gas, with a wide linear detection range from 8 to 320 ppm, and the detection limits of sensor as low as 0.44 ppm. Moreover, the nGQD@ZIF-8 sensor demonstrated enhanced ppm-level sensitivity and long-term stability for nitrobenzene detection at room temperature, while maintaining high stability under varying humidity levels and exposure to high temperatures. This enhancement is attributed to the increased contact area provided by ZIF-8 matrix, facilitating adsorption of nitrobenzene molecules on nGQDs. The nGQD@ZIF-8 exhibited good selectivity towards nitrobenzene gas (57 %) compared to other nitro volatile organic compound (VOC) vapors (nitromethane and nitropropane), and almost no significant responses were observed for the other tested VOC vapors (methanol, acetone, formaldehyde, benzene). This can be attributed to the strong interaction between the electron -deficient nitrobenzene and the nGQD@ZIF-8 nanocomposite. Overall, the proposed gas sensor in this study showed high potential for a simple, efficient, and reliable detection of nitrobenzene gas in environmental monitoring.