Orange dye—polyaniline composite based impedance humidity sensors

Abstract

This study presents the fabrication and investigation of humidity sensors based on orange dye (OD) and polyaniline (PANI) composite films. A blend of 3 wt.% OD with 1 wt.% PANI was prepared in 1 ml water. The composite films were deposited on glass substrates between pre-deposited silver electrodes. The gap between the electrodes was 45 μm. The sensing mechanism was based on the impedance and capacitance variations due to the absorption/desorption of water vapor. It was observed that with the increase in relative humidity (RH) from 30% to 90%, the impedance decreases by 5.2×104 and 8.8×103 times for the frequencies of 120 Hz and 1 kHz, respectively. The impedance—humidity relationship showed a more uniform change compared to the capacitance—humidity relationship in the RH range of 30% to 90%. The consequence of annealing, measuring frequency, response and recovery time, and absorption—desorption behavior of the humidity sensor were also discussed in detail. The annealing resulted in an increase in sensitivity of up to 2.5 times, while the measured response time and recovery time were 34 s and 450 s, respectively. The impedance—humidity relationship was simulated.

Polyaniline-Titanium dioxide composite as humidity sensor at room temperature

“…M.T.S. Chani et al Studied the humidity sensitivity of an orange dye PANI composite film by impedance measurements and have showed a uniform change in impedance for humidity values ranging from 30 -90 % RH [17]. Room temperature humidity sensing of PANI-PVA composite has been studied by Y. Li and others, and they showed that the sensitivity of the composite increases with increased impedance from 10 -90 % RH and has both quick response and recovery times [18].…”

A smart functional surfactant activated conductive polymer coated on paper with ultra-sensitive humidity sensing characteristics

“…Orange dyedoped PANI-based impedance sensor in the relative humidity range of 30-90% showed a uniform impedance-humidity relationship. Furthermore, annealed samples showed an increase in the sensitivity [31]. However, the low electrical conductivity and reversible humidity sensing effect of PANI at high humidity conditions hindered its practical use.…”

“…Furthermore, annealed samples showed an increase in the sensitivity. 31 However, the low electrical conductivity and reversible humidity sensing effect of PANI under high humidity conditions hindered its practical use. Also, PANI sensors display poor reproducibility and stability upon repeated exposure to humidity.…”

Impedimetric sensing of humidity and temperature using CeO2–Co3O4 nanoparticles in polymer hosts

“…Depending upon the nature of materials these sensors may be expansive or require high operational power/temperature and high cost of maintenance [3]. To make the sensor suitable for commercialization; the wide range sensitivity, linear response, small hysteresis, short response and recovery time, low cost and low power along with long term physical and chemical stability are the required characteristics [4,5].…”

“…Therefore the properties can be changed by changing of the ratio of ingredients in the composite. On the other hand the ingredients should be compatible in order to fabricate stable samples, i.e., to avoid the significant degradation processes [4,7]. Similarly, investigation of temperature variation effects to electric parameters of the materials are important for better understanding of mechanism of conduction, presence of phase transformation and application of the materials in temperature sensors for potential use in practice [8][9][10].…”