Fabrication of transition-metal (Zn, Mn, Cu)-based MOFs as efficient sensor materials for detection of H2 gas by clad modified fiber optic gas sensor technique

Abstract

Recent research demonstrates that promising gas sensing materials are called metal-organic frameworks (MOFs) and their products due to their tunable form, high surface area, highly porous structure, and physisorption towards gases with relatively low temperature. In this report, recent developments in transition-metal (Zn, Mn, Cu)-based MOFs and their derivatives were synthesized as sensing materials. The sensors samples were analyzed by XRD, SEM, TEM, BET and XPS to know their textural, structural and electronic state. XRD results suggest that Zn-MOF showed hexagonal crystalline structure, while Mn-MOF and Cu-MOF showed monoclinic crystalline structure. The SEM images of Zn-MOF, Mn-MOF, and Cu-MOF samples and the relative morphologies are nanotubes, nanosheets, and nanoparticles, respectively.Further, the TEM image of Zn-MOF clearly shows that nanotubes with length around 200–300 nm and diameter of 10–20 nm. Fiber optic clad modified sensors were fabricated and tested gas sensing properties towards H2 gas with various concentrations (0–1000 ppm). Among the three sensing materials, Zn doped MOFs sensor showed outstanding selectivity with high sensitivity (115 counts/kpa) towards H2 gas. Moreover, it has shown high response (20 s) and recovery time (27 s), and long-term stability. The designed sensors may be required to apply to the production of an outstanding sensor for H2 for commercial uses.