In view of their immensely intriguing properties, 2D materials are being intensely researched in search of novel phenomena and diverse application interests; however, studies on the realization of 2D/2D nanocomposites in the application-worthy thin film platform are rare. Here we have grown MoS2-hBN 2D/2D composite thin films on different substrates by the pulsed laser deposition (PLD) technique and made comparative studies with the pristine MoS2 and hBN films. The Raman and x-ray photoelectron spectroscopy (XPS) techniques as well as high-resolution transmission electron microscopy (HRTEM) confirm the concomitant presence of both the 1T (conducting) and 2H (semiconducting) polymorphs of MoS2 in the composite film. Interestingly, a peculiar reentrant semiconductor-metal-insulator transition is seen in the MoS2-hBN 2D/2D composite film which is absent in the MoS2 film, and it correlates well with the signatures of phonon softening seen in temperature dependent Raman spectroscopy. Furthermore, electrostatic force microscopy (EFM) reveals the presence of three distinct regions (metallic, semiconducting and insulating) in the MoS2-hBN composite film with differing contact potentials and enhanced propensity for charge transfer with respect to pristine MoS2. A triboelectric nanogenerator (TENG)device containing biphasic MoS2-hBN composite film as an electron acceptor exhibits more than two-fold (six-fold) enhancement in peak-to-peak output voltage as compared to the pristine MoS2 2 (hBN) film. These observations bring out the potential of 2D/2D nanocomposite thin films for unfolding emergent phenomena and technological applications.
Research on electromagnetic interference (EMI) shielding materials has become very important as one looks for polymer composites as EMI shielding paints and coatings. EMI Shielding is mainly dependent on absorption and reflection losses, which in turn depend on conductivity, permittivity and permeability of the material. In the present work, we have tried to use the properties of graphene to improve EMI shielding and absorbing properties of the polymer composite. The work is focussed on two aspects of the materials; firstly, to developed an EMI shielding paint which can be used as coating and secondly, development of such paint which has absorption as the dominant mechanism of shielding. Reduced graphene oxide(rGO) has been conjugated with ferromagnetic nanostructures. Absorption of up to ∼12 dB for composite of rGOFe 3 O 4 and ∼18 dB for the composite of rGONi was observed, which is more than 99% of the total radiation and hence, can be useful for commercial applications.
Composite materials made of polymers and carbon‐based ferromagnetic filler are attractive for electromagnetic interference shielding through a combination of reflection and microwave absorption. It is possible to enhance their shielding properties by controlling electrical conductivity, dielectric, and magnetic properties. In this work, the aforementioned properties are tailored to achieve optically transparent films with microwave absorbing properties. Nanocarbon materials, namely carbon nanotubes, graphene nanoribbons (GNR) and their ferromagnetic nanocomposites with Fe3O4 and cobalt in PVA‐PEDOT:PSS matrix were made and tested in X‐band. The highest shielding effectiveness for PVA films with nanocarbon filler was observed for 0.5 wt% GNR − Fe3O4 at 16.36 dB (9.7 GHz) with 79.8% transmittance.
In this work we address the question of growth of thin films of a soft van der Waals solid (2D MoS 2 ) on a hard, crystalline metal oxide substrates. Thus, MoS 2 thin films are grown on different single-crystal metal oxide substrates (SrLaAlO 4 , c-Al 2 O 3 , SrTiO 3 , LaAlO 3 ) by pulsed laser deposition (PLD) and characterized by different techniques to confirm and quantify their phase constitution (2H, 1T′). We observe that, on the SrLaAlO 4 (001) substrate, a mixed 1T′+2H phase of MoS 2 grows with a dominant (∼75%) 1T′ phase, while on c-Al 2 O 3 (0001) pure 2H phase grows. On the SrTiO 3 and LaAlO 3 substrates also the mixed phase grows, but with a much lesser component of the 1T′. Higher 1T′ contribution in SLAO and STO points to the chemical role of strontium in the early growth. It is also noted that, with increased film thickness on SrLaAlO 4 , the contribution of the pure 2H phase is enhanced, indicating the pivotal role of lattice strain in stabilizing the initial layer(s). The mixed 1T′+2H phase in the ultrathin film shows significantly lower room temperature resistivity (∼2 mΩ cm) with respect to that of the pure 2H phase (∼14 mΩ cm). The substrate selective polymorphism with distinct electronic features could invite multiple application interests.
Hydrogen is considered to be a very promising clean energy carrier that is expected to play a pivotal role in energy applications in the near future. [1,2] Researchers around the globe are therefore putting serious efforts to find efficient, scalable, inexpensive, and nonprecious metal-based materials/ electrodes to produce hydrogen on an industrial scale. Specifically, the production of hydrogen from water via an electrochemical process involving hydrogen evolution reaction (HER) in different alkaline/acidic media has been receiving enormous attention from the scientific community due to several specific benefits offered by this approach, as discussed in the literature. [3][4][5] Among the available materials choices of electrocatalysts, the transition metal oxides (TMOs) are considered one of the prominent materials due to their high chemical stability, rich chemistry, earth abundance, and therefore low cost, availability of easy synthetic routes, and environmentally friendly character. [6,7] These characteristics could potentially facilitate the eventual replacement of more
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