Boron nitride nanoscrolls: structure, synthesis, and applications

This is the author accepted manuscriptBoron nitride nanoscrolls (BNS) are open-ended, one-dimensional (1D) nanostructures made by the process of rolling boron nitride nanosheets (BNNS) into a scroll-like morphology. BNS offer a high surface area to volume ratio and possess many unique properties (similar to carbon nanotubes (CNT), carbon nanoscrolls (CNS) and boron nitride nanotubes (BNT)) such as high resistance to oxidation, chemical stability, increased lubrication, high-temperature resistance, electrical insulation, the ability to cap molecules inside and at the ends,and a wide band gap regardless of chirality. Despite these attractive featuresand properties well suited for applications in biotechnology, energy storage, and electronics, the true potential of boron nitride, and BNS as the next ‘miracle material’ is yet to be fully explored. In this critical review, we assess, for the first time, various studies published on the formation, structural and dynamic characteristics of BNS, potential routes for BNS synthesis, and the toxicology of BNS. Finally, the future perspectives of BNS are discussed in view of its unique and exceptional candidacy for many (real-world) applications

Computational analysis of dispersive and nonlinear 2D materials by using a GS-FDTD method

In this paper, we propose a novel numerical method for modeling nanostructures containing dispersive and nonlinear two-dimensional (2D) materials, by incorporating a nonlinear generalized source (GS) into the finite-difference time-domain (FDTD) method. Starting from the expressions of nonlinear currents characterizing nonlinear processes in 2D materials, such as second- and third-harmonic generation, we prove that the nonlinear response of such nanostructures can be rigorously determined using two linear simulations. In the first simulation, one computes the linear response of the system upon its excitation by a pulsed incoming wave, whereas in the second one the system is excited by a nonlinear GS, which is determined by the linear near-field calculated in the first linear simulation. This new method is particularly suitable for the analysis of dispersive and nonlinear 2D materials, such as graphene and transition-metal dichalcogenides, chiefly because, unlike the case of most alternative approaches, it does not require the thickness of the 2D material. To investigate the accuracy of the proposed GS-FDTD method and illustrate its versatility, the linear and nonlinear responses of graphene gratings have been calculated and compared to results obtained using alternative methods. Importantly, the proposed GS-FDTD can be extended to three-dimensional bulk nonlinearities, rendering it a powerful tool for the design and analysis of more complicated nanodevices

Nonlocal Spin Transport as a Probe of Viscous Magnon Fluids

Magnons in ferromagnets behave as a viscous fluid over a length scale, the momentum-relaxation length, below which momentum-conserving scattering processes dominate. We show theoretically that in this hydrodynamic regime viscous effects lead to a sign change in the magnon chemical potential, which can be detected as a sign change in the nonlocal resistance measured in spin transport experiments. This sign change is observable when the injector-detector distance becomes comparable to the momentum-relaxation length. Taking into account momentum- and spin-relaxation processes, we consider the quasiconservation laws for momentum and spin in a magnon fluid. The resulting equations are solved for nonlocal spin transport devices in which spin is injected and detected via metallic leads. Because of the finite viscosity we also find a backflow of magnons close to the injector lead. Our work shows that nonlocal magnon spin transport devices are an attractive platform to develop and study magnon-fluid dynamics

COTTON – GRAPHENE BASED NANO-COMPOSITES AS A SEMI-SUSTAINABLE MATERIAL FOR OIL AND CHEMICAL CLEANUP

The world is facing severe ecological and environmental problems due to the oil spills and the discharge of organic solvents into the environment. This problem has led to development of different tools and high performance materials that can both effectively and efficiently absorb these discharges from water bodies. Moreover, greener and economical methods to produce these materials are on high demand. Herein, we demonstrate a novel method of attaching graphene to functionalized cotton cellulose. The hydrophobic graphene coated cellulose with a contact angle of 144.76 o (with water) shows great oil absorption with a contact angle less than 10o towards oil and non-polar organic solvents. The absorption experiments performed exhibited an absorption capacity of 28.32, 39.91, 42.32, 40.89, 22.1, 27.67, 34.69 and 39.01 for dodecane, paraffin oil, pump oil, mineral oil, hexane, toluene and crude oil respectively. In addition, the graphene coated cellulose revealed excellent reusability, great selectivity and a high capacity. By the combination of cost effective combination, eco-friendly nature and excellent oil absorption performance, the graphene coated cotton is a promising candidate with a strong potential for large scale removal of oils from water and their environmental remediation

Misfit layer compounds as ultra-tunable field effect transistors: from charge transfer control to emergent superconductivity

Misfit layer compounds are heterostructures composed of rocksalt units stacked with few layers transition metal dichalcogenides. They host Ising superconductivity, charge density waves and good thermoelectricity. The design of misfits emergent properties is, however, hindered by the lack of a global understanding of the electronic transfer among the constituents. Here, by performing first principles calculations, we unveil the mechanism controlling the charge transfer and demonstrate that rocksalt units are always donor and dichalcogenides acceptors. We show that misfits behave as a periodic arrangement of ultra-tunable field effect transistors where a charging as large as 6\times10^{14} e^-cm^{-2} can be reached and controlled efficiently by the La-Pb alloying in the rocksalt. Finally, we identify a strategy to design emergent superconductivity and demonstrate its applicability in (LaSe)_{1.27}(SnSe_2)_2. Our work paves the way to the design synthesis of misfit compounds with tailored physical properties.Comment: First version of the manuscript (before revisions

Enhanced Amplitude for Superconductivity due to Spectrum-wide Wave Function Criticality in Quasiperiodic and Power-law Random Hopping Models

We study the interplay of superconductivity and a wide spectrum of critical (multifractal) wave functions ("spectrum-wide quantum criticality," SWQC) in the one-dimensional Aubry-Andr\'e and power-law random-banded matrix models with attractive interactions, using self-consistent BCS theory. We find that SWQC survives the incorporation of attractive interactions at the Anderson localization transition, while the pairing amplitude is maximized near this transition in both models. Our results suggest that SWQC, recently discovered in two-dimensional topological surface-state and nodal superconductor models, can robustly enhance superconductivity.Comment: 8+9 pages, 4+13 figures; v2: added superfluid stiffness result