Metal-organic frameworks-driven ZnO-functionalized carbon nanotube fiber for NO2 sensor

Abstract

In this study, heterogeneous ZnO/CNTF composites were developed to improve the NO2-sensing response, facilitated by the selfheating property. Highly conductive and mechanically stable CNTFs were prepared by a wet-spinning process assisted by the liquid crystal (LC) behavior of CNTs. Metal-organic frameworks (MOFs) of ZIF-8 were precipitated on the surface of the CNTF (ZIF-8/CNTF) via one-pot synthesis in solution. The subsequent calcination process resulted in the formation of the ZnO/CNTF composites.The calcination temperatures were controlled at 400, 500, and 600oC in an N2 atmosphere to confirm the evolution of the microstructures and NO2-sensing properties. Gas sensor characterization was performed at 100oC by applying a DC voltage to induce Joule heating through the CNTF. The results revealed that the ZnO/CNTF composite after calcination at 500oC (ZnO/CNTF-500) exhibited an improved response (Rair/Rgas = 1.086) toward 20 ppm NO2 as compared to the pristine CNTF (Rair/Rgas = 1.063). Selective NO2-sensing properties were demonstrated with negligible responses toward interfering gas species such as H2S, NH3, CO, and toluene. Our approach for the synthesis of MOF-driven ZnO/CNTF composites can provide a new strategy for the fabrication of wearable gas sensors integrated with textile materials.