A Micromachined Metal Oxide Composite Dual Gas Sensor System for Principal Component Analysis-Based Multi-Monitoring of Noxious Gas Mixtures.

In-Hwan Yang,Nam Ki Min,Joon-Hyung Jin

doi:10.3390/mi11010024

Abstract

Microelectronic gas-sensor devices were developed for the detection of carbon monoxide (CO), nitrogen dioxides (NO2), ammonia (NH3) and formaldehyde (HCHO), and their gas-sensing characteristics in six different binary gas systems were examined using pattern-recognition methods. Four nanosized gas-sensing materials for these target gases, i.e., Pd-SnO2 for CO, In2O3 for NOX, Ru-WO3 for NH3, and SnO2-ZnO for HCHO, were synthesized using a sol-gel method, and sensor devices were fabricated using a microsensor platform. Principal component analysis of the experimental data from the microelectromechanical systems gas-sensor arrays under exposure to single gases and their mixtures indicated that identification of each individual gas in the mixture was successful. Additionally, the gas-sensing behavior toward the mixed gas indicated that the traditional adsorption and desorption mechanism of the n-type metal oxide semiconductor (MOS) governs the sensing mechanism of the mixed gas systems.

Highlights

With the increasing importance of indoor and outdoor air quality for human health and the natural environment, various air-monitoring applications equipped with highly sensitive gas sensors have been used for detecting hazardous gases emitted from various sources, such as automobiles, industrial plants, waste-management facilities, and food and household products
Metal oxide semiconductor (MOS)-based gas sensors have attracted considerable attention owing to their high compatibility with various consumer applications that demand low energy consumption, simplicity of use, and multi-gas detection ability [1]
Besides these intrinsic sensing properties of metal oxide materials, environmental conditions such as the presence of water and interference gas species in an atmosphere affect the selectivity and sensitivity of metal oxide semiconductor (MOS) sensors [8]. To overcome these issues related to selectivity and sensitivity, nanomaterials are increasingly used as sensing materials for MOS sensors owing to their size-dependent properties

Summary

Introduction

With the increasing importance of indoor and outdoor air quality for human health and the natural environment, various air-monitoring applications equipped with highly sensitive gas sensors have been used for detecting hazardous gases emitted from various sources, such as automobiles, industrial plants, waste-management facilities, and food and household products. MOS gas sensors, which can detect either the oxidation or reduction of gas coming into contact with a thin metal oxide surface by measuring changes in the surface conductivity, have been successfully manufactured using thin- and thick-film technologies for the microfabrication of a gas-sensitive metal oxide film on an electrode substrate [2,3,4,5] Their low selectivity, response-curve drifts, temperature-dependent properties prevent them from achieving high selectivity and sensitivity to the target gas species in a gaseous atmosphere with long-term stability and reliability [6,7]. Nanosized metal oxide materials doped with noble metals or synthesized with mixed metal oxides improve the sensitivity and selectivity to a target gas through the catalytic reactivity and morphology of deposited films [9,10]

Methods

Results

Conclusion