High performance chemical sensor is highly desirable to detect traces of toxic gas molecules. Two dimensional (2D) transition metal dichalcogenides (TMDC) semiconducting materials has attracted as high performance gas sensor device applications due to unique properties such as high surface to volume ratio. Here, we describe the utilization of single-layer MoSe₂ as high-performance room temperature NH₃ gas sensors. Our single-layer MoSe₂ based gas sensor device shows comprehensible detection of NH₃ gas down to 50 ppm. We also confirmed gas sensing measurement by recording the Raman spectra before and after exposing the device to NH₃ gas, which subsequently shows the shift due to charger transfer and analyte gas molecule adsorption on surface of single-layer MoSe₂ nanosheet. Our investigations show the potential use of single-layer and few layer thick MoSe₂ and other TMDC as high-performance gas sensors.

We report here the field emission studies of a layered WS₂-RGO composite at the base pressure of ~1 × 10⁻⁸ mbar. The turn on field required to draw a field emission current density of 1 μA/cm² is found to be 3.5, 2.3 and 2 V/μm for WS₂, RGO and the WS₂-RGO composite respectively. The enhanced field emission behavior observed for the WS₂-RGO nanocomposite is attributed to a high field enhancement factor of 2978, which is associated with the surface protrusions of the single-to-few layer thick sheets of the nanocomposite. The highest current density of ~800 μA/cm² is drawn at an applied field of 4.1 V/μm from a few layers of the WS₂-RGO nanocomposite. Furthermore, first-principles density functional calculations suggest that the enhanced field emission may also be due to an overalp of the electronic structures of WS₂ and RGO, where graphene-like states are dumped in the region of the WS₂ fundamental gap.

We investigate the growth mechanism and temperature dependent Raman spectroscopy of chemical vapor deposited large area monolayer of MoS₂, MoSe₂, WS₂ and WSe₂ nanosheets up to 70 μm in lateral size.

We report the synthesis of V₂O₅ nanosheets by a simple hydrothermal method.