E. A. Albanesi

The anisotropic band structure of layered In4Se3(001)

There is discernable and significant band dispersion along both high symmetry directions for cleaved ordered surfaces of the layered In4Se3(001). The extent of dispersion of approximately 1 eV is observed along the surface chain rows, and about 0.5 eV perpendicular to the surface “furrows,” consistent with theoretical expectations. A possible surface state exists at the surface Brillouin zone edge, in the direction perpendicular to the chains, in a gap of the projected bulk band structure. Excluding the possible surface state, the experimental hole mass is 5.5 times greater along the chains than perpendicular to the chains, but the dispersion is easier to discern.

The electronic structure of surface chains in the layered semiconductor In4Se3(100)

The ordered (100) surface of layered In4Se3 single crystals is characterized by semiconducting quasi-one-dimensional indium (In) chains. A band with significant dispersion in the plane of the surface is observed near the valence band maximum. The band exhibits an anisotropic dispersion with ∼1eV band width along the In chain direction. The dispersion of this band is largely due to the hybridization of In-s and Se-p orbitals, but the hybridization between In-s and Se-p and In-p and Se-p orbitals is also critical in establishing the band gap.

Theoretical study of the adsorption of histidine amino acid on graphene

Previous studies have demonstrated how the interactions between biomolecules and graphene play a crucial role in the characterization and functionalization of biosensors. In this paper we present a theoretical study of the adsorption of histidine on graphene using density functional theory (DFT). In order to evaluate the relevance of including the carboxyl (-COOH) and amino (-NH2) groups in the calculations, we considered i) the histidine complete (i.e., with its carboxyl and its amino groups included), and ii) the histidines imidazole ring alone. We calculated the density of states for the two systems before and after adsorption. Furthermore, we compared the results of three approximations of the exchange and correlation interactions: local density (LDA), the generalized gradients by Perdew, Burke and Ernzerhof (GGA-PBE), and one including van der Waals forces (DFT-D2). We found that the adsorption energy calculated by DFT-D2 is higher than the other two: Eads-DFT-D2 >E ads-LDA >E ads-GGA . We report the existence of charge transfer from graphene to the molecule when the adsorption occurs; this charge transfer turns up to be greater for the complete histidine than for the imidazole ring alone. Our results revealed that including the carboxyl and amino groups generates a shift in the states of imidazole ring towards EF .

Molecular Dynamics Simulation of the Adsorption of Histidine on Graphene

The possibility of utilizing graphene as a biosensor has received a considerable attention in recent years. Here, we present results on the molecular dynamics of the adsorption of the aminoacid histidine on graphene, based on ab initio calculations within a pseudopotentials approach. Taking into consideration the amine and carboxylic groups of the aminoacid (not only the imidazole ring), we calculate the adsorption energy and final mean distance to the graphene sheet, along with the slight deformation of the graphene. Furthermore, we provide with a detailed discussion on two ways of calculating (and presenting) the adsorption curve (interaction energy vs. mean distance), depending on how relaxation of atomic positions is included in the calculations.