Recent Progress on Anti-Humidity Strategies of Chemiresistive Gas Sensors

Abstract

In recent decades, chemiresistive gas sensors (CGS) have been widely studied due to their unique advantages of expedient miniaturization, simple fabrication, easy operation, and low cost. As one ubiquitous interference factor, humidity dramatically affects the performance of CGS, which has been neglected for a long time. With the rapid development of technologies based on gas sensors, including the internet of things (IoT), healthcare, environment monitoring, and food quality assessing, the humidity interference on gas sensors has been attracting increasing attention. Inspiringly, various anti-humidity strategies have been proposed to alleviate the humidity interference in this field; however, comprehensive summaries of these strategies are rarely reported. Therefore, this review aims to summarize the latest research advances on humidity-independent CGS. First, we discussed the humidity interference mechanism on gas sensors. Then, the anti-humidity strategies mainly including surface engineering, physical isolation, working parameters modulation, humidity compensation, and developing novel gas-sensing materials were successively introduced in detail. Finally, challenges and perspectives of improving the humidity tolerance of gas sensors were proposed for future research.

Rapid Detection of Trace Nitro-Explosives under UV Irradiation by Electronic Nose with Neural Networks

“…When the humidity continues to increase to 80% RH, the response values of all eight sensors show an increasing trend, which may be due to the formation of a large amount of OH – on the surface of the sensitive material. NO 2 molecules react with OH – and obtain electrons from the sensitive material, resulting in an increase in the response value. , When the humidity changes from 0 to 20% RH, the sensor response value changes significantly, while when the humidity is between 20 and 80% RH, the sensor response value fluctuates within an acceptable range. Due to the fact that the humidity in the actual testing environment is usually in the range of 20–80% RH, the sensor array is minimally affected by humidity interference.…”

One-step green synthesis of Cu2O/CuO@rGO composites for ppt level detection of NO2 at room temperature

“…71 Under a high humidity environment, it is mainly physical adsorption. 72 Meanwhile, the absorbed H 2 O will occupy the active adsorption sites of the material and where M denotes metal elements in metal oxides, the text is Cu; M m is the site of M on the surface; O ad À presents ionosorbed oxygen species; e À is an electron; (M m + À OH) presents a terminal hydroxyl group; and N denotes a surface site for chemically adsorbing oxygen. Therefore, the chemical adsorption of H 2 O molecules can directly change the baseline resistance of the sensor with humid atmospheres.…”

Heterojunctions of ZnO-Nanorod-Decorated WO3 Nanosheets Coated with ZIF-71 for Humidity-Independent NO2 Sensing

“…19,20 So, many researchers have also focused on improving the immunity to humidity of metal oxide-based sensors. 21 Recently, MOF materials have stood out in the fields of gas adsorption, 22 separation and storage, 23 catalysis, 24 and sensors 25,26 by virtue of their high porosity, large specific surface area, and tunable pore size. The high thermal stability and hydrophobic properties of the ZIF family are exactly what we are seeking.…”

“…It is important to form heterojunctions with two-dimensional materials for the gas sensing performance improvement of sensors. , Nevertheless, the issue of humidity impacts on metal oxide semiconductor gas sensors still deserves to be addressed. The main reason is that atmospheric humidity cannot be ignored in practice, while in high-humidity environments water vapor molecules can occupy the adsorption sites of oxygen molecules, reducing or even destroying the performance of the gas sensor. , So, many researchers have also focused on improving the immunity to humidity of metal oxide-based sensors …”