A Facile Liquid‐Phase, Solvent‐Dependent Exfoliation of Large Scale MoS 2 Nanosheets and Study of Their Photoconductive Behaviour for UV‐Photodetector Application

Water as Solvent for the Dispersion of 2D Nanostructured Materials

The development of large number of two-dimensional (2D) nanostructured materials that followed the success of graphene and the need for their handling and manipulation e. g., in inks, brought to the fore the study of solvents and substances that contribute to the stabilization of 2D nanomaterials in the liquid phase. The successful dispersion of 2D materials in solvents is combined with one of the most widespread preparation methods, that of liquid phase exfoliation. In this article, a review for the role of water in the preparation of different 2D nanostructures and their stable dispersions in the liquid phase is discussed. The use of water as a solvent or dispersant is instrumental in promoting materials with an ecological footprint, low cost, and sustainability.

High-Performance MoS2/SWCNT Composite Films for a Flexible Thermoelectric Power Generator

Single-walled carbon nanotube (SWCNT)-based thermoelectric materials have been extensively studied in the field of flexible wearable devices due to their high flexibility and excellent electrical conductivity (σ). However, poor Seebeck coefficient (S) and high thermal conductivity limit their thermoelectric application. In this work, free-standing MoS₂/SWCNT composite films with improved thermoelectric performance were fabricated by doping SWCNTs with MoS₂ nanosheets. The results demonstrated that the energy filtering effect at the MoS₂/SWCNT interface increased the S of composites. In addition, the σ of composites was also improved due to the reason that S-π interaction between MoS₂ and SWCNTs made good contact between MoS₂ and SWCNTs and improved carrier transport. Finally, the obtained MoS₂/SWCNT showed a maximum power factor of 131.9 ± 4.5 μW m^-1 K^-2 at room temperature with a σ of 680 ± 6.7 S cm^-1 and an S of 44.0 ± 1.7 μV K^-1 at a MoS₂/SWCNT mass ratio of 15:100. As a demonstration, a thermoelectric device composed of three pairs of p-n junctions was prepared, which exhibited a maximum output power of 0.43 μW at a temperature gradient of 50 K. Therefore, this work offers a simple method of enhancing the thermoelectric properties of SWCNT-based materials.

A Thrifty Liquid-Phase Exfoliation (LPE) of MoSe2 and WSe2 Nanosheets as Channel Materials for FET Application

Two-dimensional materials are trending nowadays because of their atomic thickness, layer-dependent properties, and their fascinating application in the semiconducting industry. In this work, we have synthesized MoSe₂ and WSe₂ nanosheets (NSs) via a liquid-phase exfoliation method and investigated these NSs as channel materials in field-effect transistors (FET). The x-ray diffraction (XRD) pattern revealed that the synthesized NSs have a 2H phase with 0.65 nm d-spacing which belongs to the (002) Miller plane. Transmission electron microscopy (TEM) studies revealed that MoSe₂ and WSe₂ have a nanosheet-like structure, and the average lateral dimensions of these NSs are ~ 25 nm and ~ 63 nm, respectively. From Raman spectra, we found that the intensity of the A_1g vibrational mode decreases with the reduction in the number of layers. UV-visible spectroscopy revealed that the bandgap values of MoSe₂ and WSe₂ NSs are 1.55 eV and 1.50 eV, respectively, calculated using the Tauc equation. The output and transfer characteristics of the FET devices reveals that the fabricated FETs have good ohmic contact with the channel material and an ON/OFF current ratio of about 10² for both devices. This approach for the fabrication of FET devices can be achieved even without sophisticated fabrication facilities, and they can be applied as gas sensors and phototransistors, among other applications.