Vertically Aligned 2D MoS₂ Layers with Strain-Engineered Serpentine Patterns for High-Performance Stretchable Gas Sensors: Experimental and Theoretical Demonstration

Abstract

Two-dimensional (2D) molybdenum disulfide (MoS2) with vertically aligned (VA) layers exhibits significantly enriched surface-exposed edge sites with an abundance of dangling bonds owing to its intrinsic crystallographic anisotropy. Such structural variation renders the material with exceptionally high chemical reactivity and chemisorption ability, making it particularly attractive for high-performance electrochemical sensing. This superior property can be further promoted as far as it is integrated on mechanically stretchable substrates well retaining its surface-exposed defective edges, projecting opportunities for a wide range of applications utilizing its structural uniqueness and mechanical flexibility. In this work, we explored VA-2D MoS2 layers configured in laterally stretchable forms for multifunctional nitrogen dioxide (NO2) gas sensors. Large-area (>cm2) VA-2D MoS2 layers grown by a chemical vapor deposition (CVD) method were directly integrated onto a variety of flexible substrates with serpentine patterns judiciously designed to accommodate a large degree of tensile strain. These uniquely structured VA-2D MoS2 layers were demonstrated to be highly sensitive to NO2 gas of controlled concentration preserving their intrinsic structural and chemical integrity, e.g., significant current response ratios of ∼160–380% upon the introduction of NO2 at a level of 5–30 ppm. Remarkably, they exhibited such a high sensitivity even under lateral stretching up to 40% strain, significantly outperforming previously reported 2D MoS2 layer-based NO2 gas sensors of any structural forms. Underlying principles for the experimentally observed superiority were theoretically unveiled by density functional theory (DFT) calculation and finite element method (FEM) analysis. The intrinsic high sensitivity and large stretchability of VA-2D MoS2 layers confirmed in this study are believed to be applicable in sensing diverse gas species, greatly broadening their versatility in stretchable and wearable technologies.

Wafer‐Scale Van der Waals Assembly of Free‐Standing Near Atom Thickness Hetero‐Membranes for Flexible Photo‐Detectors

“…Figure 1b-g present the characterization data of these materials which were grown by a chemical vapor deposition (CVD)-based thermal sulfurization or tellurization of Pt thin films, similar to the growth of other 2D TMDs. [13,16,[18][19][20][21][22][23][24][25][26] Specific details regarding the growth conditions are found in the Experimental Section. Figure 1b displays a low-magnification cross-sectional transmission electron microscopy (TEM) image of a non-layered PtS thin film (left) as well as its corresponding high resolution TEM (HR-TEM) image (right).…”

Atomic-scale characterization of structural heterogeny in 2D TMD layers

“…In addition, vertically-aligned (VA) 2D MoS 2 layers have also been demonstrated as identified via HR-TEM (Fig. 6(d)), 57 showing uniformly-spaced vdW gaps. Moreover, integral VA 2D PtSe 2 layers have been observed via HR-TEM (Fig.…”

“…[50][51][52][53] Extensive efforts have been devoted to the direct visualization of the gaps. 57 Reproduced with permission from ref. 57 Copyright 2020 American Chemical Society.…”

MoS2–xSex Nanoparticles for NO Detection at Room Temperature

“…Several researchers have identified that semiconductor MoS 2 active sites are mostly located on the edge of the crystal structures, while the abundant basal plane is relatively less reactive for chemical reactions. , Therefore, it is necessary to modify the basal plane of MoS 2 to improve its reactivity. Among other methods, the doping process is one of the most promising techniques to modify the basal plane structure of MoS 2 because it modifies not only the structure but also the electronic and optical properties of MoS 2 . , The doping process by the substitution of the element could make different chemical bondings in the crystal lattice (expand or shrink), which could act as active site centers for the adsorption because of a strain in the crystal structure. , The strain in the crystal structure of MoS 2 increases the molecular adsorption ability including higher adsorption energy, closer adsorption distance, and better charge transfer ability …”