Synthesis and characterization of Cu-doped ZnO nanofibers for ethanol vapor sensing

Pure and copper-doped zinc oxide (ZnO) nanofibers (NFs) were fabricated by the sol-gel electrospinning (ES) technique with varying concentrations (1, 3, and 5 w%). Scanning electron microscope (SEM), X-ray diffraction (XRD), and ultraviolet-visible (UV-Vis) spectroscopy were used to investigate the morphology, structure, and optical properties of the NFs. The average fiber diameter (AFD) of the Cu-doped ZnO (Cu-Z) NFs decreased with the increase in doping concentration. The structural analysis found that all the NFs samples were polycrystalline and oriented along the (101) plane. Also, the crystalline size decreased from 26.58 to 18.45 nm as the copper (Cu) concentration increased, and a maximum crystalline size was observed for 5 w% Cu-Z NFs. The band gap of undoped and Cu-Z NFs was calculated from UV VIS spectra, and it was observed that the bandgap decreased from 3.45 to 2.9 eV due to the addition of 5 w% Cu. The sensing performance of the NFs was investigated for 50 ppm of ethanol vapor at various operating temperatures (25–300 °C). The results indicated that the 5 w% Cu-Z NFs had the highest response to ethanol vapor, of 12.65 for 50 ppm, with response and recovery times of 70s and 35s. The Cu-Z NFs exhibited good selectivity and stability while tested with other vapors.