Abstract
In this paper, we report on the development of a highly sensitive and humidity-tolerant metal-oxide-based volatile organic compound (VOC) sensor, capable of rapidly detecting low concentrations of VOCs. For this, we successfully fabricated two different thicknesses of nickel oxide (NiO) sensors using a spin-coating technique and tested them with seven different common VOCs at 40% r.h. The measured film thickness of the spin-coated NiO was ~5 μm (S-5) and ~10 μm (S-10). The fastest response and recovery times for all VOCs were less than 80 s and 120 s, respectively. The highest response (Rg/Ra = 1.5 for 5 ppm ethanol) was observed at 350 °C for both sensors. Sensors were also tested in two different humidity conditions (40% and 90% r.h.). The humidity did not significantly influence the observed sensitivity of the films. Furthermore, S-10 NiO showed only a 3% drift in the baseline resistance between the two humidity conditions, making our sensor humidity-tolerant compared to traditional n-type sensors. Thus, we propose thick-film NiO (10 μm) sensing material as an interesting alternative VOC sensor that is fast and humidity-tolerant.
Highlights
The abundance of volatile organic compounds (VOCs) present in the air is an everincreasing worldwide problem [1]
According to the World Health Organization (WHO), there are more than 4.2 million deaths every year as a result of air pollution, with an increasing percentage of these deaths linked to VOCs [2]
The detection mechanism of metal-oxide semiconductor (MOX)-based gas sensors is chemo-resistive, where a change in the electrical resistance of the sensing material is correlated to the change in gas change in the electrical resistance of the sensing material is correlated to the change in gas concentration
Summary
The abundance of volatile organic compounds (VOCs) present in the air is an everincreasing worldwide problem [1]. Everyday human activity results in the emission of toxic chemicals, including VOCs, driven by the increase in global industrial processes. According to the World Health Organization (WHO), there are more than 4.2 million deaths every year as a result of air pollution, with an increasing percentage of these deaths linked to VOCs [2]. Several major environmental safety agencies, such as the National VOCs are very complex to detect, when separating VOCs of similar chemical structures
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