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) we present a comprehensive picture connecting the atomic arrangement of borophene and the X-ray absorption spectra. Once we have 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 those BSLs were examined based on total energy DFT calculations. We find a highly anisotropic electronic structure, characterized by the electronic confinement effects, and the formation of metallic channels along the superlattices. Combining DFT and the Landauer-Büttiker formalism, we investigate the electronic transport properties in the 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 huge magnification on the directional dependence of the electronic transport properties in BSLs, in comparision with the pristine borophene phase. Those findings indicate that BSLs are quite interesting systems in order to design conductive nanoribbons in a 2D platform.

Understanding the role of microscopic attributes in nanocomposites allows one to control and, therefore, accelerate experimental system designs. In this work, we extracted the relevant parameters controlling the graphene oxide binding strength to cellulose by combining first-principles calculations and machine learning algorithms. We were able to classify the systems among two classes with higher and lower binding energies, which are well defined based on the isolated graphene oxide features. Using theoretical X-ray photoelectron spectroscopy analysis, we show the extraction of these relevant features. In addition, we demonstrate the possibility of refined control within a machine learning regression between the binding energy values and the system’s characteristics. Our work presents a guiding map to control graphene oxide/cellulose interaction.

Cellulose disassembly is an important issue in designing nanostructures using cellulose-based materials. In this work, we present a combination of experimental and theoretical study addressing the disassembly of cellulose nanofibrils. Through 2,2,6,6-tetramethylpiperidine-1-oxyl-mediated oxidation processes, combined with atomic force microscopy results, we show the formation of nanofibers with diameters corresponding to that of a single-cellulose polymer chain. The formation of these polymer chains is controlled by repulsive electrostatic interactions between the oxidized chains. Further, first-principles calculations have been performed in order to provide an atomistic understanding of the cellulose disassembling processes, focusing on the balance between the interchain (IC) and intersheet (IS) interactions upon oxidation. First, we analyze these interactions in pristine systems, where we found the IS interaction to be stronger than the IC interaction. In the oxidized systems, we have considered the formation of (charged) carboxylate groups along the inner sites of elementary fibrils. We show a net charge concentration on the carboxylate groups, supporting the emergence of repulsive electrostatic interactions between the cellulose nanofibers. Indeed, our total energy results show that the weakening of the binding strength between the fibrils is proportional to the concentration and net charge density of the carboxylate group. Moreover, by comparing the IC and IS binding energies, we found that most of the disassembly processes should take place by breaking the IC O–H···O hydrogen bond interactions and thus supporting the experimental observation of single- and double-cellulose polymer chains.

Neste trabalho investigamos o comportamento de propriedades mecânicas e eletrônicas de heteroestruturas laterais 2D formadas por diferentes fases de folhas de Boro, conhecidas na literatura como borofeno. Por cálculos via DFT, replicamos os dados da literatura para duas fases distintas do borofeno, que foram a base para a montagem das superredes. As superredes foram montadas de dois modos distintos, para analisarmos as alterações estruturais e eletrônicas nas superredes devidoà mudança da direção do empilhamentos. Entre as propriedades eletrônicas, investigamos o caráter metálico das estruturas, a separação dos estados nas regiões próximas ao nível de Fermi, bem como a formação e o comportamento de canais condutores nas heteroestruturas. Também foi analisada a estabilidade energética das estruturas.