Electrical and Humidity-Sensing Properties of Impedance-Type Humidity Sensors that Were Made of Ag Microwires/PPy/SnO2 Ternary Composites

Pi-Guey Su,Ping-Hsiang Lu

doi:10.3390/chemosensors8040092

Abstract

Impedance-type humidity sensors were fabricated via one-step UV-irradiation photopolymerization of Ag microwires (Ag MWs), polypyrrole (PPy) and SnO2 ternary composite (Ag MWs/PPy/SnO2) films on an alumina substrate. X-ray diffractometry (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) coupled with an energy dispersive X-ray (EDX) elemental mapping were used to analyze the morphology, structure, and composition of Ag MWs/PPy/SnO2 ternary composite films. Microstructural observations revealed that the Ag MWs were embedded, and PPy formed on the surface of the Ag MWs/PPy/SnO2 ternary composite film. The effects of the addition amounts of loading of Ag and PPy on the electrical and humidity-sensing properties of the Ag MWs/PPy/SnO2 ternary composite films were investigated. The impedance-type humidity sensor based on Ag MWs/PPy/SnO2 ternary composite film containing 6 mg of Ag and 0.1 g of PPy had the highest sensitivity and an acceptable linearity over the RH ranged from 10% to 90% RH, a low hysteresis, a fast response time, and long-term stability. This technique is useful for practical application because its fast and ease of fabrication. The ions (H3O+) that dominate the impedance changed with relative humidity (RH) for the humidity sensor that based on Ag MWs/PPy/SnO2 ternary composite film was analyzed using complex impedance spectra.

Highlights

Measuring and controlling humidity is an important issue because humidity is necessary in controlling the quality of productions in fabrication processes and maintaining human health in a comfortable environment [1,2,3]
Microstructural observations revealed that the Ag microwires (Ag MWs) were embedded, and PPy formed on the surface of the Ag MWs/PPy/SnO2 ternary composite film
The impedance-type humidity sensor based on Ag MWs/PPy/SnO2 ternary composite film containing 6 mg of Ag and 0.1 g of PPy had the highest sensitivity and an acceptable linearity over the relative humidity (RH) ranged from 10% to 90% RH, a low hysteresis, a fast response time, and long-term stability

Summary

Introduction

Measuring and controlling humidity is an important issue because humidity is necessary in controlling the quality of productions in fabrication processes and maintaining human health in a comfortable environment [1,2,3]. Various materials have been fabricated as humidity sensors including polymers [6,7,8,9,10], ceramics [11,12,13,14], and composite materials [5,15,16,17,18,19] Among these materials, ceramics are favored materials in the humidity-sensing because they had the advantages such as good heat resistance, cost-effectiveness, water resistance at high humidity, and high stability in a wider humidity-working range [5]. Among various metal oxide sensors, most of the development work was centered on SnO2 material due to its advantages such as lower working temperature, excellent electrochemical stability, high sensitivity to water vapor in air, non-toxicity, corrosion resistance, low cost and long lifetime [20,21], which makes it can be used as a candidate material for humidity detection. SnO2 , a n-type semiconducting material, was the most studied ceramic humidity-sensing material because it exhibited inherent chemical, physical stability, and helpful H2 O adsorption ability [5,22], but did not have obvious resistance changes at higher relative humidity (RH)

Methods

Discussion

Conclusion