Research Article Impedimetric Humidity Sensor Based on Nanohybrid Composite of Conducting Poly(diphenylamine sulfonic acid) Fule Dinç Zor and Hüsnü Cankurtaran Department of Chemistry, Yildiz Technical University, Davutpasa, 34220 Istanbul, Turkey Correspondence should be addressed to S ¸ule Dinc ¸ Zor; sule dinc@yahoo.com Received 22 December 2015; Accepted 10 February 2016 Academic Editor: Sang Sub Kim Copyright © 2016 S ¸. Dinc ¸ Zor and H. Cankurtaran. Tis is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Interdigitated thin flm 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 efect 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. 1. Introduction Te development of humidity sensors has showed a remark- able progress because of using various types of sensing mate- rials in recent years. Te sensing materials used in humidity sensors can be classifed into ceramics [1–3], polymers [4, 5], and composites [6–8]. Ceramic humidity sensors based on semiconductor metal oxides have some critical limitations such as elevated working temperature, insufcient sensitivity, and repeatability. Polymeric humidity sensors have been widely studied for ten years. Almost all of the humidity sensors based on polymers sensitively operate at room temperature. In terms of the stability of the sensors, some highly hydrophilic polyelectrolyte and functional polymer based sensors are not sufciently resistant at high humidity conditions. However, their hydrophilicity and ionic conduc- tivity can be easily 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]. So, these composite humidity sensors, which combine with unique property and synergistic efect of each component, have some advantages such as high sensitivity, small hysteresis, quick response, and high stability. Nanoscaled materials have high adsorption capacity due to their small grain size and large specifc surface area. Many kinds of nanometal oxides such as, TiO 2 [16, 17], SnO 2 [18, 19], SiO 2 [20], ZrO 2 [21], and ZnO [22–27] have been widely employed alone or along with other polymers in humidity sensors due to these properties. Among them, ZnO is one of the most well-known gas sensing materials, which has been extensively carried out for study of some gases and vapors such as ethanol [28–30], acetone [31], ammonia [32], NO 2 [33], CO [34], H 2 S [35], and hydrogen [36]. Conducting polymers which are able to change in elec- trical conductivity with relative humidity are good candi- dates for humidity sensing material. Tey also have high sensitivity at room temperature, ease of synthesis, facile processability, and high stability [37]. Moreover, the com- bination of conducting polymers with inorganic nanopar- ticles leads to a development on humidity sensors with superior properties. Many reports have been published about humidity sensor applications based on nanomate- rial/conducting polymer composites [21, 38–40]. In our previous study, we reported that the water soluble/conductive Hindawi Publishing Corporation Journal of Sensors Volume 2016, Article ID 5479092, 9 pages http://dx.doi.org/10.1155/2016/5479092