Impedance spectroscopy characteristics of nano ZnO doped liquid crystal/polymer film

Zhu Qing; Liu Yourong; Jiang Zhipeng; Zheng Jihong

doi:10.12086/oee.2020.190540

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Zhu Q, Liu Y R, Jiang Z P, et al. Impedance spectroscopy characteristics of nano ZnO doped liquid crystal/polymer film[J]. Opto-Electron Eng, 2020, 47(9): 190540. doi: 10.12086/oee.2020.190540

Citation:

Zhu Q, Liu Y R, Jiang Z P, et al. Impedance spectroscopy characteristics of nano ZnO doped liquid crystal/polymer film[J]. Opto-Electron Eng, 2020, 47(9): 190540. doi: 10.12086/oee.2020.190540

Impedance spectroscopy characteristics of nano ZnO doped liquid crystal/polymer film

1.
School of Optical-Electrical and Computer Engineering, University of Shanghai for Science and Technology, Shanghai 200093, China
2.
Shanghai Key Lab of Modern Optical System, University of Shanghai for Science and Technology, Shanghai 200093, China

Fund Project: Supported by National Natural Science Foundation of China (61975122) and Science and Technology Development Project of University of Shanghai for Science and Technology(USST) (36-17-302-041)

More Information

^*Corresponding author: Zheng Jihong, E-mail:jihongzheng@usst.edu.cn

Received Date 12 September 2019

Revised Date 03 January 2020

Published Date 15 September 2020

Abstract

Abstract

In this paper, the electrical impedance spectroscopy characteristics of polymer dispersed liquid crystal (PDLC) doped with nano-zinc oxide rods and its sensing applications are studied. Polymer dispersed liquid crystal films have the characteristics of stable structure, resistance to mechanical impact and easy preparation. By doping nano-zinc oxide rods into the material, the sensing function of polar molecules such as ethanol gas can be realized through the analysis of electrical impedance spectroscopy. In this paper, the complex impedance spectra of thin films encountering ethanol molecules are studied and analyzed through comparative experiments. In addition, the electrochemical equivalent circuit was established and analyzed. It was found that the film could sensitively and effectively realize the sensing function of the ethanol molecules. The sensitivity and response time of the sensor are further analyzed and studied. The experimental study and analysis show that nano-zinc oxide rod doped PDLC film is expected to be used as a gas sensor for detecting polarity of ethanol and other materials. It has the advantages of high sensitivity, stable structure, high repeatability, and easy fabrication.
- polymer dispersed liquid crystal /
- nano-ZnO rods /
- gas detection /
- impedance analysis /
- equivalent circuit model

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References

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Overview

Overview

Overview: In this paper, the electrical impedance spectroscopy characteristics of polymer dispersed liquid crystal (PDLC) doped with nano-zinc oxide rods and its sensing applications are studied. Polymer dispersed liquid crystal films have the characteristics of stable structure, resistance to mechanical impact, and easy preparation. By doping nano-zinc oxide rods into the material, the sensing function of polar molecules, such as ethanol gas, can be realized through the analysis of electrical impedance spectroscopy. The design realizes the detection of ethanol by measuring the impedance change of the film. It does not need complicated optical instruments to analyze the spectra of polar gases, such as ethanol before and after passing through. The design is simple, practical, and real-time. Based on the liquid crystal cell coated with ITO conductive glass, nano-ZnO rod doped PDLC thin films were prepared by photopolymerization phase separation method. In this paper, the complex impedance spectra of thin films encountering ethanol molecules are studied and analyzed through comparative experiments. And the electrochemical equivalent circuit was established and analyzed. It was found that the film could sensitively and effectively realize the sensing function of ethanol molecules. The principle is that when nano-ZnO rods based on polymer dispersed liquid crystals are exposed to reducing gas ethanol, then oxygen atoms react with reducing gas to release electrons, thus forming conduction channels, which ultimately results in great changes in film impedance values. The sensitivity and response time of the sensor are further analyzed and studied. The impedance curve of nano-ZnO rod-doped PDLC changes instantaneously and drops sharply in the response time of 15 s after it is fed into ethanol gas at 100 Hz. Then in the instant of withdrawing ethanol gas, the impedance curve responds instantaneously and rises rapidly in the recovery time of 4 s. In addition, the experimental results show that the nano-ZnO films doped with 0.1% are very sensitive to the detection of ethanol polar gases when the frequency is about 100 Hz and the ambient temperature is 25 ℃. The sensitivity value is as high as 14.3. The sensitivity of PDLC films doped with nano-ZnO is much higher than that of films without any doping. Both experimental and simulation results show that the material is extremely sensitive to ethanol as a polar molecule. We believe that nano-ZnO rod doped PDLC films can be used as sensors and have important application value in the detection of polar molecules.