Liquid Shear Exfoliation of MoS2: Preparation, Characterization, and NO2-Sensing Properties

Abstract

2D materials possess great potential to serve as gas-sensing materials due to their large, specific surface areas and strong surface activities. Among this family, transition metal chalcogenide materials exhibit different properties and are promising candidates for a wide range of applications, including sensors, photodetectors, energy conversion, and energy storage. Herein, a high-shear mixing method has been used to produce multilayered MoS2 nanosheet dispersions. MoS2 thin films were manufactured by vacuum-assisted filtration. The structural morphology of MoS2 was studied using ς-potential, UV–visible, scanning electron microscopy (SEM), atomic force microscopy (AFM), energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), X-ray diffraction (XRD), and Raman spectroscopy (RS). The spectroscopic and microscopic analyses confirm the formation of a high-crystalline MoS2 thin film with good inter-sheet connectivity and relative thickness uniformity. The thickness of the MoS2 layer is measured to be approximately 250 nm, with a nanosheet size of 120 nm ± 40 nm and a number of layers between 6 and 9 layers. Moreover, the electrical characteristics clearly showed that the MoS2 thin film exhibits good conductivity and a linear I–V curve response, indicating good ohmic contact between the MoS2 film and the electrodes. As an example of applicability, we fabricated chemiresistive sensor devices with a MoS2 film as a sensing layer. The performance of the MoS2-chemiresistive sensor for NO2 was assessed by being exposed to different concentrations of NO2 (1 ppm to 10 ppm). This sensor shows a sensibility to low concentrations of 1 ppm, with a response time of 114 s and a recovery time of 420 s. The effect of thin-film thickness and operating temperatures on sensor response was studied. The results show that thinner film exhibits a higher response to NO2; the response decreases as the working temperature increases.

Water-Based Bi2S3 Nano-Inks Obtained with Surfactant-Assisted Liquid Phase Exfoliation and Their Direct Processing into Thin Films

“…of the nanosheet rather than the thickness [43]. Since both small thickness and small lateral length of the nanosheets correspond to higher band gap values, because of the quantum confinement, the influence of layer thickness is not considered in the values of DLS, thus causing the mismatch between band gap values and average particle size, as measured from DLS.…”

“…It is apparent that some inconsistencies emerge in band gap values versus average particle size calculated from DLS. This discrepancy may arise from the fact that for 2D and 1D materials, DLS primarily estimates the lateral length of the nanosheet rather than the thickness [43]. Since both small thickness and small lateral length of the nanosheets correspond to higher band gap values, because of the quantum confinement, the influence of layer thickness is not considered in the values of DLS, thus causing the mismatch between band gap values and average particle size, as measured from DLS.…”

2D Material‐Based Wearable Energy Harvesting Textiles: A Review

“…The majority of these nanosheets exhibit a similar apparent AFM height of 2–4 nm (Figure 4j), with a step height of 0.8–1 nm, which is consistent with the monolayer height of chemically exfoliated MoS 2 . [ 294 ] The high shear method created significantly expanded/delaminated MXene (Ti 3 C 2 Tx) nanosheets, according to scanning electron microscopy (SEM) images from a study. In Figure 4k, layered morphology illustrates the expanded/delaminated MXene's existence.…”

“…Spectra, XPS (NMP‐exfoliated samples) measured on thin films, AFM on a surfactant‐exfoliated sample. h) AFM images of MoS2 nanosheets; i) layer number distribution of MoS 2 nanosheets; j) thickness plot of selected MoS 2 nanosheets in images (h); [ 294 ] k) SEM image of MX–H delaminated layered surface morphology. Reproduced with permission.…”

Integrated Logic Circuits Based on Wafer-Scale 2D-MoS2 FETs Using Buried-Gate Structures

“…Therefore, it shows a wide range of applications in the various fields. For example, previous reports on photodetectors [24], optoelectronic memories [25], sensors [26], flexible electronic devices, and logic devices are currently being actively studied [7,[27][28][29][30][31].…”