Dual Selective Gas Sensing Characteristics of 2D α-MoO_3–x via a Facile Transfer Process

Abstract

Metal oxide-based gas sensor technology is promising due to their practical applications in toxic and hazardous gas detection. Orthorhombic α-MoO3 is a planar metal oxide with a unique layered structure, which can be obtained in two-dimensional (2D) form. In 2D form, the larger surface to volume ratio of the material facilitates significantly higher interaction with gas molecules while exhibiting exceptional transport properties. Presence of oxygen vacancies results in non-stoichiometric MoO3 (MoO3-x), which further enhances the charge carrier mobility. Here, we study dual gas sensing characteristics and mechanism of 2D α-MoO3-x.Herein, conductometric dual gas sensors based on CVD grown 2D α-MoO3-x are developed and demonstrated. A facile transfer process is established to integrate the material into any arbitrary substrate. The sensors show high selectivity towards NO2 and H2S gases with response/recovery rates of 295.0 kΩ/s and 276.0 kΩ/s towards NO2, and 28.5 kΩ/s and 48.0 kΩ/s towards H2S, respectively. These gas sensors also show excellent cyclic endurance with a variation in ΔR ~112 ± 1.64 MΩ and 19.5 ± 1.13 MΩ for NO2 and H2S, respectively. As such, this work presents the viability of planar 2D α-MoO3-x as a dual selective gas sensor.

In-plane anisotropic optical and mechanical properties of two-dimensional MoO3

“…Among the available anisotropic 2D materials, molybdenum trioxide is a wide band gap semiconductor (>2.7eV) 28 , which makes it quasi-transparent in the visible spectrum while being still electrically conductive. This nanomaterial has been proven useful for gas sensing 29 , resistive memory technology 30 , optoelectronic [31][32][33][34][35][36][37][38][39][40] , electrochromic 41 and flexible 42,43 applications. The difference between the in-plane (a-c) lattice parameters makes α-MoO3 a perfect candidate to investigate optical, mechanical, and electrical in-plane anisotropic properties.…”

Two-Dimensional Materials in Large-Areas: Synthesis, Properties and Applications

“…In producing large-area uniform 2D oxides, ME methods do not provide a universal synthesis method since a majority of oxides have non-layered crystal structures. Recently, CVD methods have been reported to produce large-area 2D oxides of MoO 3 [ 183 ] and consequently, the reliable transfer techniques [ 184 ] have been invented to enable large-area optoelectronics and sensing applications using MoO 3 . LM seems to be a frontier in 2D oxide synthesis with uniform thicknesses [ 47 ].…”

Advanced Strategies to Improve Performances of Molybdenum-Based Gas Sensors

“…The nanosheets with a higher surface area than the nanoflakes provide more active sites for surface reaction. Rahman et al [75] also performed exfoliation using a different route. The CVD method was used to deposit α-MoO 3 on the substrate.…”