MoSe₂ Crystalline Nanosheets for Room-Temperature Ammonia Sensing

Abstract

We report a highly sensitive and selective ammonia (NH 3 ) gas sensor made from liquid exfoliated MoSe 2 nanosheets. The powder obtained after exfoliation was used to make a two-terminal sensor on a quartz substrate with predeposited silver contacts. The device so obtained, exhibited excellent sensitivity (5.5%) at an ammonia concentration down to 1 ppm, a fast response and recovery time of 15 and 135 s, respectively, better reproducibility, and impressive selectivity against various gases at room temperature. Moreover, density functional theory (DFT) simulations were used to understand the adsorption kinetic and electronic structure and therefore to shed light on the fundamentals of the sensing mechanism. Bader analysis was performed to understand the charge transfer process between the adsorbed ammonia gas molecule and underlying MoSe 2 surface. The resulting analysis confirmed that the electrons transfer from NH 3 molecules to MoSe 2 . The slight shift of the valence band toward the Fermi level which is clear from band structure analysis, along with the experimental fact that after exposure to ammonia the sensor displays an increase in resistance, indicates p-type behavior of the processed MoSe 2 crystalline nanosheets. These results imply the potential use of scaled nanosheets of MoSe 2 as a promising sensing material for enhanced and selective NH 3 gas monitoring at room-temperature.

NiWO4 Microflowers on Multi-Walled Carbon Nanotubes for High-Performance NH3 Detection

“…Although the NH 3 detection methods based on optical instruments feature with high accuracy, good reliability, and low detection limits, the equipment based on optical instruments is usually expensive and large in volume, requiring professional personnel to operate. Therefore, such methods are not suitable for widespread applications. , The electrochemical method to detect NH 3 is the most mature, but its disadvantages include its small detection range, low accuracy, and need for frequent calibration. − In terms of gas-sensitive materials, the solid-state sensors based on metal oxides can be commercialized on a large scale and can achieve a low detection limit and high sensitivity. − …”

Electrospun Polyacrylonitrile Nanofibers Mixed with Citric Acid as a Quartz Crystal Microbalance Ammonia Vapor Sensor

“…Monitoring of ammonia level in the air using a gas/vapor sensor is in great demand [4,5] . Many works have been devoted to developing a high‐performance ammonia vapor sensor using various sensing platforms (i. e., resistive, [6,7] optical, [8] amperometric, [9] and acoustic [10] ). Among these devices, acoustic sensors based on quartz crystal microbalance (QCM) have been preferred due to their high sensitivity, real‐time measurement capability, and simple integration with other electronic components [11–16] .…”

Vanadium Disulfide Nanosheets Synthesized by Facile Liquid‐Phase Exfoliation for Ammonia Detection with High Selectivity

“…[30] MoSe 2 NSs has also been discovered to show resistance enhancement to ammonia, which has also been explained by the p-type MoSe 2 and reducing ability of ammonia. [32] Although T-VS 2 has been theoretically predicted to be metallic and it surely exhibit low resistance in the research of Feng et al, [11] some theoretical research predicted metal-insulator (semiconductor) transition of T-VS 2 from bulk to monolayer. [33,34] Therefore, it is of great necessity to systematically investigate ammonia sensing property of VS 2 not only for extending the application of VS 2 but also for understanding the properties of VS 2 more deeply.…”

“…the resistance is enhanced [30][31][32]. Intuitively, the VS 2 in this research is supposed to be p-type semiconductor.…”