Abstract
Interdigitated thin film humidity sensors have been prepared using organic/inorganic nanocomposites of poly(diphenylamine sulfonic acid) (PSDA), 3-mercaptopropyltrimethoxysilane (MPTMS), and nano-ZnO. Humidity sensing properties of the sensors, regarding the effect of nano-ZnO addition and the applied alternating current frequency, were studied by impedance measurements in the frequency range of 100 Hz–1 kHz. It was found that the sensing properties of the ZnO based nanocomposite sensors had better properties than those of the PSDA-MPTMS based composite due to contribution of the nanomaterial. Good sensitivity (about three orders’ magnitude change in impedance), linear response, rapid response (90 s) and recovery (60 s), and low hysteresis within 4% as well as good repeatability and stability in the range from 12% to 95% RH were obtained.
Highlights
The development of humidity sensors has showed a remarkable progress because of using various types of sensing materials in recent years
We reported that the water soluble/conductive Journal of Sensors poly(diphenylamine sulfonic acid) in its diblock copolymer and blend with poly(ethylene glycol) and poly(vinyl acetateco-butyl acrylate) would be a good candidate as humidity sensing material [41]
The magnitude of the distinct stretching vibration band of ZnO near 480 cm−1 decreases in PSDA-MPTMS-ZnO nanocomposite
Summary
The development of humidity sensors has showed a remarkable progress because of using various types of sensing materials in recent years. In terms of the stability of the sensors, some highly hydrophilic polyelectrolyte and functional polymer based sensors are not sufficiently resistant at high humidity conditions. Their hydrophilicity and ionic conductivity can be adjusted using various methods such as copolymerization, cross-linking with relatively hydrophobic and insulating polymers. Composites in humidity sensors consist of polymer and another material which is insulating or conducting polymer [9], metal [10, 11], metal oxide [12, 13], or nanomaterials [14, 15]. These composite humidity sensors, which combine with unique property and synergistic effect of each component, have some advantages such as high sensitivity, small hysteresis, quick response, and high stability
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