Enhanced Gas Sensing Performance of Surface‐Activated MoS₂ Nanosheets Made by Hydrothermal Method with Excess Sulfur Precursor

Abstract

Defect engineering of two‐dimensional (2D) nanostructures is of significant importance for achieving enhanced surface properties in optoelectronic, sensors, and catalytic applications. In this work, the authors study the gas‐sensing properties of 2D molybdenum sulfide (MoS2) nanosheets fabricated using a hydrothermal synthetic route with various nominal S/Mo precursor ratios, in order to generate nano‐domains on the surface. The effect of the excess S precursor on the morphology and the resulting gas sensing performance are investigated by varying the S/Mo precursor ratio in the range of 2–12. Nano‐domains are generated on the MoS2 basal plane for all samples, and their evolution became significant as the S/Mo precursor ratio increases. The presence of the nano‐domains provides additional active edge sites, enhancing the surface‐to‐mass ratio and the resulting gas‐sensing properties. Resistive type gas sensing tests using such 2D MoS2 show that, when the S/Mo precursor ratio is increased from 2 to 12, the sensitivity to 500 ppm NO2 gas at room temperature increased from 27 to 213%.

Controlled synthesis of ultrathin MoS2nanoflowers for highly enhanced NO2sensing at room temperature

“…17,37 However, some other works indicated that in spite of slow rates of gas adsorption and desorption, the pristine MoS 2 -based sensors showed the complete recovery at RT to target gases. 20,[38][39][40] This characteristic can be attributed to several factors, such as high specic surface area, defective/strained surface and weak van der Waals binding between the target gas and the MoS 2 surface. 20,38,39 In addition, Ikram et al indicated that the high specic surface area not only increases the response of the sensor but also plays an important role in fast response and recovery times.…”

“…20,[38][39][40] This characteristic can be attributed to several factors, such as high specic surface area, defective/strained surface and weak van der Waals binding between the target gas and the MoS 2 surface. 20,38,39 In addition, Ikram et al indicated that the high specic surface area not only increases the response of the sensor but also plays an important role in fast response and recovery times. 41 Thus, understanding the detailed mechanism for the complete recovery of the sensor is still under debate because of the combined effects of physi-, chemi-sorption, role of defects sites and transduction mechanism 37 .…”

“…The sensors work at RT, but their response to a high NO 2 concentration of 100 ppm is as low as 99.3%. 20 Similarly, sensors based on PbS quantum dot/MoS 2 composites show an optimal OT at RT but a low sensitivity of 22.5% to 100 ppm NO 2 . 22 The gas-sensing performance of MoS 2 materials is strongly dependent on material morphology and quality, such as specic surface area and crystallite size.…”

“…16,17 A previous study also formed MoS 2 nanoakes through sonication-assisted exfoliation. 9 Several 3D MoS 2 nanostructures, such as spheres and nanosheets, were synthesised using a hydrothermal approach, [18][19][20] which is a simple and low-cost mass-production synthesis method with growth parameters that can be easily controlled. Regarding the sensing characteristics of hydrothermally synthesised MoS 2 nanostructures, Zhang et al fabricated sensors based on MoS 2 nanospheres grown via a hydrothermal procedure assisted with CTAB for NO 2 detection.…”

Controlled growth of 3D assemblies of edge enriched multilayer MoS2 nanosheets for dually selective NH3 and NO2 gas sensors

“…Recently, the three-dimensional (3D) assembly of multilayer TMD nanosheets has attracted the attention of many researchers, since the gas adsorption at the edge sites of the TMD nanosheets is more significant than at their basal plane, thus enhancing sensitivity and selectivity. 26–28 In the case of MoS 2 , its basal plane is most of the times used as a chemical receptor, because it is easy to expose and produce using exfoliation or chemical vapor deposition techniques. However, this basal plane surface has minimal dangling bonds, and due to thermodynamic forces, it is difficult to expose their edge sites to the environment.…”