Effect of the pore size of TiO2 porous film on humidity sensitive properties of TiO2/NaPSS composite films

TiO2 and polystyrene sulfonic sodium (NaPSS) composite film humidity sensors were fabricated via dip-coating method on the alumina substrate. The effect of the pore size of TiO2 porous film on humidity sensing properties was investigated in this study. Surface morphology of these films was measured by field emission scanning electron microscope (FESEM) and atomic force microscopy (AFM). The different morphology of these films was observed when the pore size of TiO2 porous film was varied from 4500 nm to 100 nm. The impedance measurements were done with a LCR analyzer. Remarkable variations of the impedance of the composite film humidity sensors were observed by changing the pore size of TiO2 porous film.