Nanoscale structural and electronic properties of cellulose/graphene interfaces.

The development of electronic devices based on the functionalization of (nano)cellulose platforms relies upon an atomistic understanding of the structural and electronic properties of a combined system, cellulose/functional element. In this work, we present a theoretical study of the nanocellulose/graphene interfaces (nCL/G) based on first-principles calculations. We find that the binding energies of both hydrophobic/G (nCLphob/G) and hydrophilic/G (nCLphil/G) interfaces are primarily dictated by the van der Waals interactions, and are comparable with those of their 2D interface counterparts. We verify that the energetic preference of nCLphob/G has been reinforced by the inclusion of an aqueous medium via an implicit solvation model. Further structural characterization was carried out using a set of simulations of the carbon K-edge X-ray absorption spectra to identify and distinguish the key absorption features of the nCLphob/G and nCLphil/G interfaces. The electronic structure calculations reveal that the linear energy bands of graphene lie in the band gap of the nCL sheet, while depletion/accumulation charge density regions are observed. We show that external agents, i.e., electric field and mechanical strain, allow for tunability of the Dirac cone and charge density at the interface. The control/maintenance of the Dirac cone states in nCL/G is an important feature for the development of electronic devices based on cellulosic platforms.

Electronic stripes and transport properties in borophene heterostructures.

We performed a theoretical investigation of the structural and electronic properties of (i) pristine and (ii) superlattice structures of borophene. In (i), by combining first-principles calculations, based on the density functional theory (DFT), and simulations of the X-ray Absorption Near-Edge Structure (XANES) spectra we present a comprehensive picture connecting the atomic arrangement of borophene and the X-ray absorption spectra. Once we characterized the electronic properties of the pristine systems, we next examined the electronic confinement effects in 2D borophene superlattices (BSLs) [(ii)]. Here, the BSL structures were made by attaching laterally two different structural phases of borophene. The energetic stability and the electronic properties of these BSLs were examined based on total energy DFT calculations. We find a highly anisotropic electronic structure, characterized by the electronic confinement effects, giving rise to "electronic stripes", and metallic channels ruled by the superlattices. Combining DFT and the Landauer-Büttiker formalism, we investigated the electronic transport properties in BSLs. Our results of the transmission probability reveal that the electronic transport is ruled by π or a combination of π and σ transmission channels, depending on the atomic arrangement and periodicity of the superlattices. Finally, we show that there is a huge magnification of the directional dependence of the electronic transport properties in BSLs, in comparison with the pristine borophene phase. These findings indicate that BSLs are quite interesting systems in order to design conductive nanoribbons on a 2D platform.