Study Of MoS2 Research Articles

Study of MoS2 as an Electric Field Sensor and the Role of Layer Thickness on the Sensitivity.

In this study, we investigate the scope of molybdenum disulfide (MoS2) as an electric field sensor. We show that MoS2 sensors can be used to identify the polarity as well as to detect the magnitude of the electric field. The response of the sensor is recorded as the change in the drain current when the electric field is applied. The sensitivity, defined as the percentage change in the drain current, reveals that it has a linear relation with the magnitude of the electric field. Furthermore, the sensitivity is highly dependent on the layer thickness, with the single-layer device being highly sensitive and the sensitivity decreasing with the thickness. We have also compared the electric field sensitivity of MoS2 devices to that of previously studied graphene devices and found the former to be exceptionally sensitive than the latter for a given electric field magnitude.

Effect of gamma irradiation on the physical properties of MoS2 monolayer.

Two-dimensional transition metal dichalcogenides (2D-TMDs) have been proposed as novel optoelectronic materials for space applications due to their relatively light weight. MoS2 has been shown to have excellent semiconducting and photonic properties. Although the strong interaction of ionizing gamma radiation with bulk materials has been demonstrated, understanding its effect on atomically thin materials has scarcely been investigated. Here, we report the effect of gamma irradiation on the structural and electronic properties of a monolayer of MoS2. We perform Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) studies of MoS2, before and after gamma ray irradiation with varying doses and density functional theory (DFT) calculations. The Raman spectra and XPS results demonstrate that point defects dominate after the gamma irradiation of MoS2. DFT calculations elucidate the electronic properties of MoS2 before and after irradiation. Our work makes several contributions to the field of 2D materials research. First, our study of the electronic density of states and the electronic properties of a MoS2 monolayer irradiated by gamma rays sheds light on the properties of a MoS2 monolayer under gamma irradiation. Second, our study confirms that point defects are formed as a result of gamma irradiation. And third, our DFT calculations qualitatively suggest that the conductivity of the MoS2 monolayer may increase after gamma irradiation due to the creation of additional defect states.

Gamma-ray resonance spectroscopic study of MoS2- and iron-based catalysts

1. A gamma-resonance spectroscopic study has been made of systems obtained by impregnating molybdenum disulfide samples with solutions of57Fe(NO3)3·9H2O in different solvents (formamide, acetone, water) and subsequently sulfidizing them. After a catalyst is sulfidized, most of the iron is in the form of magnetic sulfides, and the remainder is present in the form of the paramagnetic ions Fe2+ and Fe3+. 2. The catalytic activity of these systems in the hydrogenation of o-xylene in the presence of thiophene, which depends on the type of solvent, is due to the paramagnetic iron ions that form a structure in combination with the MoS2; the activity increases with increasing amounts of Fe3+ ions.

The Role of Oleophilic Surface in Lubrication

Surfaces of MoS2 and graphite are composed of ‘oleophilic’ regions, which have a strong affinity for long-chain normal hydrocarbons, and polar regions. The oleophilic regions adsorb hydrocarbons in preference to polar compounds, such as water and alcohols. Conversely, water and alcohols easily displace hydrocarbons adsorbed in the polar sites. A study of MoS2 and graphite having different proportions of oleophilic and polar sites shows that the lubricating effectiveness of these solids increases with the proportion of oleophilic sites on their surfaces. For MoS2 the sites consist of regularly disposed sulphur atoms in the basal planes of individual crystallites, and it is postulated that they can become chemically bonded to steel surfaces. When one basal plane side of a MoS2 crystallite is bonded to the steel surface, the other side presents an oleophilic surface to the surroundings, which has a low surface energy and high affinity for mineral oils. The oleophilic ‘sites’ produced in this way on the metal surface are believed to be instrumental in increasing the load-carrying capacity of the steel surfaces in sliding and rolling contact, especially in the presence of mineral oils.