Using Graphdiyne Nanoribbons for Molecular Electronics Spectroscopy and Nucleobase Identification: A Theoretical Investigation.

In pursuit of fast, cost-effective, and reliable DNA sequencing techniques, a variety of two-dimensional (2D) material-based nanodevices such as solid-state nanopores and nanochannels have been explored and established. Given the promising potential of graphene for the design and fabrication of nanobiosensors, other 2D carbon allotropes such as graphyne and graphdiyne have also attracted a great deal of attention as candidate materials for the development of sequencing technology. Herein, employing the 2D electronic molecular spectroscopy (2DMES) method, we investigate the capability of graphdiyne nanoribbons (GDNRs) as the building blocks of a feasible, precise, and ultrafast sequencing device.

DNA/RNA sequencing using germanene nanoribbons two dimensional molecular electronic spectroscopy: an study.

Developing fast, reliable, and cost effective, yet practical DNA/RNA sequencing methods and devices is a must. In this regard, motivated by the recently introduced two-dimensional electronic molecular spectroscopy (2DMES) technique for molecular recognition, and the compatibility of 2D layers of group IV elements with the current technology of manufacturing electronic devices, we investigate the capability of germanene nanoribbons (GeNRs) as a feasible, accurate, and ultra-fast sequencing device under the application of 2DMES. We show that by employing 2DMES, not only can GeNRs unambiguously distinguish different nucleobases to sequence DNA/RNA, they are also capable of recognizing methylated nucleobases that could be related to cancerous cell growth.

A Potassium Metal-Organic Framework based on Perylene-3,4,9,10-tetracarboxylate as Sensing Layer for Humidity Actuators.

We have synthesized a novel three-dimensional metal-organic-framework (MOF) based on the perylene-3,4,9,10-tetracarboxylate linker and potassium as metallic centre. We report the formation of this K-based MOF using conventional routes with water as solvent. This material displays intense green photoluminescence at room temperature, and displays an aggregation dependent quenching.

Atomic-scale defects and electronic properties of a transferred synthesized MoS monolayer.

MoS monolayer samples were synthesized on a SiO/Si wafer and transferred to Ir(111) for nano-scale characterization. The samples were extensively characterized during every step of the transfer process, and MoS on the final substrate was examined down to the atomic level by scanning tunneling microscopy (STM). The procedures conducted yielded high-quality monolayer MoS of milimeter-scale size with an average defect density of 2 × 10 cm.

Versatile synthesis and enlargement of functionalized distorted heptagon-containing nanographenes.

Highly distorted polycyclic aromatic hydrocarbons (PAHs) are predicted to be attractive goals in nanoscience owing to the new properties they can exhibit. We have shown that a variety of functionalized distorted heptagon-containing nanographenes can be easily prepared from simple building blocks by a sequence of Co-catalyzed cyclotrimerization and cyclodehydrogenation reactions. The versatility of this strategy allows easy subsequent enlargement of these nanostructures by Ni-catalyzed cross-coupling and final cyclodehydrogenation reactions.

Adsorption of small inorganic molecules on a defective MoS monolayer.

We present a theoretical study of molecular adsorption on defects on a MoS monolayer. Based on Density Functional Theory, our calculations confirm that small inorganic molecules, such as CO, CO, HO, NO, NO, H and N, remain bonded to the pristine monolayer through weak van der Waals interactions, suggesting that the molecules may easily diffuse over the clean monolayer. On the other hand, the introduction of defects can lead to three different situations, depending on the defect and the molecule considered: physisorption, chemical (strong) bonding to the metallic defects, namely the Mo substitutional atoms on the S vacancies, and dissociation, that can take place spontaneously at 0 K in some specific cases or by the effect of thermal agitation in molecules such as CO or NO on the S vacancy.

Atomistic boron-doped graphene field-effect transistors: a route toward unipolar characteristics.

We report fully quantum simulations of realistic models of boron-doped graphene-based field-effect transistors, including atomistic details based on DFT calculations. We show that the self-consistent solution of the three-dimensional (3D) Poisson and Schrödinger equations with a representation in terms of a tight-binding Hamiltonian manages to accurately reproduce the DFT results for an isolated boron-doped graphene nanoribbon. Using a 3D Poisson/Schrödinger solver within the non-equilibrium Green's function (NEGF) formalism, self-consistent calculations of the gate-screened scattering potentials induced by the boron impurities have been performed, allowing the theoretical exploration of the tunability of transistor characteristics.

Quantum transport in graphene nanoribbons: effects of edge reconstruction and chemical reactivity.

We present first-principles transport calculations of graphene nanoribbons with chemically reconstructed edge profiles. Depending on the geometry of the defect and the degree of hydrogenation, spectacularly different transport mechanisms are obtained. In the case of monohydrogenated pentagon (heptagon) defects, an effective acceptor (donor) character results in strong electron-hole conductance asymmetry.

Chemically induced mobility gaps in graphene nanoribbons: a route for upscaling device performances.

We report a first-principles based study of mesoscopic quantum transport in chemically doped graphene nanoribbons with a width up to 10 nm. The occurrence of quasi-bound states related to boron impurities results in mobility gaps as large as 1 eV, driven by strong electron-hole asymmetrical backscattering phenomena. This phenomenon opens new ways to overcome current limitations of graphene-based devices through the fabrication of chemically doped graphene nanoribbons with sizes within the reach of conventional lithography.

Anomalous doping effects on charge transport in graphene nanoribbons.

We present first-principles calculations of quantum transport in chemically doped graphene nanoribbons with a width of up to 4 nm. The presence of boron and nitrogen impurities is shown to yield resonant backscattering, whose features are strongly dependent on the symmetry and the width of the ribbon, as well as the position of the dopants. Full suppression of backscattering is obtained on the pi-pi* plateau when the impurity preserves the mirror symmetry of armchair ribbons.

Transport length scales in disordered graphene-based materials: strong localization regimes and dimensionality effects.

We report on a numerical study of quantum transport in disordered two dimensional graphene and graphene nanoribbons. By using the Kubo and the Landauer approaches, transport length scales in the diffusive (mean free path and charge mobilities) and localized regimes (localization lengths) are computed, assuming a short range disorder (Anderson-type). The electronic systems are found to undergo a conventional Anderson localization in the zero-temperature limit, in agreement with localization scaling theory.

Anderson localization in carbon nanotubes: defect density and temperature effects.

The role of irradiation induced defects and temperature in the conducting properties of single-walled (10, 10) carbon nanotubes has been analyzed by means of a first-principles approach. We find that divacancies modify strongly the energy dependence of the differential conductance, reducing also the number of contributing channels from two (ideal) to one. A small number of divacancies (5-9) brings up strong Anderson localization effects and a seemly universal curve for the resistance as a function of the number of defects.