Effects of Different Surfactants on Humidity Sensing Properties of CeO2 Nanobelts Thin Film Prepared by Hydrothermal Method

CeO2 nanobelts were synthesized with three different types of surfactants (polyethyleneglycol [PEG], cetyltrimethyl ammonium bromide [CTAB], and sodium dodecylbenzene sulfonate [SDBS]) via hydrothermal method. X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) were utilized to characterize the phase structures and morphologies of the products. CeO2-C (the sample with CTAB as surfactant) has the largest specific surface area among three samples. The humidity sensing performances of the corresponding sensors were also investigated. CeO2-C shows high humidity sensitivity (the impedance decreases by about five orders of magnitude), rapid response–recovery characteristics (6 and 7 s), and narrow hysteresis loop (4%) at 100 Hz in the relative humidity range from 11% to 95%. Such results indicate that the cationic surfactant (CTAB) can effectively improve on the performance of CeO2 humidity sensors.