Highly Sensitive and Selective Gas Sensors Based on NiO/MnO₂@NiO Nanosheets to Detect Allyl Mercaptan Gas Released by Humans under Psychological Stress

Abstract

NiO nanosheets are synthesized in situ on gas sensor chips using a facile solvothermal method. These NiO nanosheets are then used as gas sensors to analyze allyl mercaptan (AM) gas, an exhaled biomarker of psychological stress. Additionally, MnO 2 nanosheets are synthesized onto the surfaces of the NiO nanosheets to enhance the gas-sensing performance. The gas-sensing response of the NiO nanosheet sensor is higher than that of the MnO 2 @NiO nanosheet sensor. The response value can reach 56.69, when the NiO nanosheet sensor detects 40 ppm AM gas. Interestingly, a faster response time (115 s) is obtained when the MnO 2 @NiO nanosheet sensor is exposed to 40 ppm of AM gas. Moreover, the selectivity toward AM gas is about 17-37 times greater than those toward confounders. The mechanism of gas sensing and the factors contributing to the enhance gas response of the NiO and MnO 2 @NiO nanosheets are discussed. The products of AM gas oxidized by the gas sensor are identified by gas chromatography-mass spectrometry (GC/MS). AM gas detection is an unprecedented application for semiconductor metal oxides. From a broader perspective, the developed sensors represent a new platform for the identification and monitoring of gases released by humans under psychological stress, which is increasing in modern life.

Defective WO3 Nanosheets with (002)-Exposed Facet for Highly Sensitive Acetone Detection

“…Nowadays, gas sensors based on semiconductor metal oxides (MOS), such as tin oxide (SnO 2 ), zinc oxide (ZnO), and nickel oxide (NiO), have become the common sensor in the field of gas sensing applications. − As an n-type MOS, WO 3 -based gas sensors have been reported to have great potential for acetone sensing . For the low sensitivity, many strategies have been adopted to put WO 3 -based gas sensors to practical use .…”

“…The rate of response of a semiconductor oxide sensor is influenced by various factors, including the interaction of the gas with the surface of the sensitive layer, the adsorption−desorption process, and the diffusion rate. The D-WO 3 -(002) with (002) facet and the defect of oxygen vacancy may facilitate the transfer of electrons between acetone and sensitive layer 10.…”

Ultraviolet-Induced Gas Sensing Performance of Ag/WO3/rGO Nanocomposites for H2S Gas Sensors

“…Previous studies have also explored the use of precious metals such as Pd, Au, and Pt as dopants for metal oxides, resulting in improved gas sensing performance. The inclusion of noble metals as catalysts can modify the specific surface area, activation energy, and resistance of metal oxides, leading to enhanced gas sensing capabilities . Ag has advantageous physical properties as it is less toxic and more cost-effective compared to other noble metals .…”

“…The inclusion of noble metals as catalysts can modify the specific surface area, activation energy, and resistance of metal oxides, leading to enhanced gas sensing capabilities. 18 Ag has advantageous physical properties as it is less toxic and more cost-effective compared to other noble metals. 19 Additionally, the addition of Ag can create numerous active centers on metal oxide surfaces, which can enhance the selective absorption of reaction gases.…”

Facet-Controlled Synthesis of CeO2 Nanoparticles for High-Performance CeO2 Nanoparticle/SnO2 Nanosheet Hybrid Gas Sensors

“…In addition, the gas selectivity of sensors should also be improved to facilitate the identification of a plurality of gaseous components. A method of identifying gases was recently developed that relies on analyzing signals from different gas species using multiple sensors. − Such sensing applications require multiple low-concentration gas sensors with different selectivities; thus, many commercially available sensors have been developed based on SnO 2 and ZnO. However, further improvements to the performance and selectivity of these sensors are required to facilitate the detection of gases at low concentrations and the identification of target gases.…”