Sun-Graphyne: A New 2D Carbon Allotrope with Dirac Cones

Due to the success achieved by graphene, several 2D carbon-based allotropes were theoretically predicted and experimentally synthesized. Here, we propose a new 2D carbon allotrope named Sun-Graphyne (S-GY). We used density functional theory and reactive molecular dynamics simulations to investigate its mechanical, structural, electronic, and optical properties. The results showed that S-GY exhibits good dynamical and thermal stabilities. Its formation energy and elastic moduli are -8.57 eV/atom and 262.37 GPa, respectively. S-GY is a semi-metal and presents two Dirac cones in its band structure. This material is transparent, and its intense optical activity is limited to the infrared region. Remarkably, the band structure of S-GY remains practically unchanged at even moderate strain regimes. As far as we know, this is the first 2D carbon allotrope to exhibit this behaviour.Comment: 17 pages, and 11 figure

Improving the room-temperature ferromagnetism in ZnO and low-doped ZnO:Ag films using GLAD sputtering

ZnO and doped ZnO films with non-ferromagnetic metal have been widely used as biosensor elements. In these studies, the electrochemical measurements are explored, though the electrical impedance of the system. In this sense, the ferromagnetic properties of the material can be used for multifunctionalization of the sensor element using external magnetic fields during the measurements. Within this context, we investigate the room-temperature ferromagnetism in pure ZnO and Ag-doped ZnO films presenting zigzag-like columnar geometry. Specifically, we focus on the films’ structural and quasi-static magnetic properties and disclose that they evolve with the doping of low-Ag concentrations and the columnar geometry employed during the deposition. The magnetic characterization reveals ferromagnetic behavior at room temperature for all studied samples, including the pure ZnO one. By considering computational simulations, we address the origin of ferromagnetism in ZnO and Ag-doped ZnO and interpret our results in terms of the Zn vacancy dynamics, its substitution by an Ag atom in the site, and the influence of the columnar geometry on the magnetic properties of the films. Our findings bring to light an exciting way to induce/explore the room-temperature ferromagnetism of a non-ferromagnetic metal-doped semiconductor as a promising candidate for biosensor applications.This works was partially supported by the Brazilian agencies CNPq and CAPES. Furthermore, this work was also supported by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UID/FIS/04650/2019 and project PTDC/BTMMAT/28237/2017. A. Ferreira thanks FCT for the contract under the Stimulus of Scientific Employment (CTTI-31/18–CF (2) junior researcher contract). RMT thanks the Center for Computational Engineering & Sciences (CCES) at Unicamp for financial support through the FAPESP/CEPID Grant 2013/08293-7. LDM would also like to thank the support of the High-Performance Computing Center at UFRN (NPAD/UFRN). The work reported in this paper was supported by On-Surf Mobilizar Competencias Tecnologicas em Engenharia de Superficies, Project POCI-01-0247-FEDER-024521

Two-dimensional (2D) d-Silicates from abundant natural minerals

In the last decade, the materials community has been exploring new 2D materials (graphene, metallene, TMDs, TMCs, MXene, among others) that have unique physical and chemical properties. Recently, a new family of 2D materials, the so-called 2D silicates, have been proposed. They are predicted to exhibit exciting properties (such as high catalytic activity, piezoelectricity, and 2D magnetism). In the current work, we demonstrate a generic approach to the synthesis of large-scale 2D silicates from selected minerals, such as Diopside (d). Different experimental techniques were used to confirm the existence of the 2D structures (named 2D-d-silicates). DFT simulations were also used to gain insight into the structural features and energy harvesting mechanisms (flexoelectric response generating voltage up to 10 V). The current approach is completely general and can be utilized for large-scale synthesis of 2D silicates and their derivatives, whose large-scale syntheses have been elusive

Atomic Adsorption on Nitrogenated Holey Graphene

Two-dimensional (2D) crystals with C₂N stoichiometry have recently been synthesized. This novel material, dubbed nitrogenated holey graphene (NHG), is a semiconductor unlike pristine graphene. For any novel material, it is fundamental to understand the behaviors of different adatoms on its surface, a process responsible for a rich phenomenology. In this work, we employed first-principles calculations and a hybrid quantum mechanics/molecular mechanics method to investigate the adsorption of H, B, and O on NHG sheets. The adsorption of H atoms could prove important for applications in hydrogen storage and gas sensors, whereas the adsorption of O in any new material is important to understand its oxidation process. Both N and B are common dopants in carbon-based systems, such as in BNC structures. We found that H and B prefer to adsorb on top of a nitrogen atom, whereas O prefers to adsorb on top of a carbon–carbon bond. The electronic structure of NHG also changes as a result of the presence of adatoms, with the appearance of midgap states close to the Fermi level. In the case of NHG + H and NHG + B, we observed the appearance of a finite magnetic moment, related to the midgap states, which could give rise to a magnetoresistance effect. Our results provide insight into the adsorption of impurities on this novel 2D carbon-based material, with potential for applications in novel electronic devices

Plasmodium sporozoite search strategy to locate hotspots of blood vessel invasion

International audienceAbstract Plasmodium sporozoites actively migrate in the dermis and enter blood vessels to infect the liver. Despite their importance for malaria infection, little is known about these cutaneous processes. We combine intravital imaging in a rodent malaria model and statistical methods to unveil the parasite strategy to reach the bloodstream. We determine that sporozoites display a high-motility mode with a superdiffusive Lévy-like pattern known to optimize the location of scarce targets. When encountering blood vessels, sporozoites frequently switch to a subdiffusive low-motility behavior associated with probing for intravasation hotspots, marked by the presence of pericytes. Hence, sporozoites present anomalous diffusive motility, alternating between superdiffusive tissue exploration and subdiffusive local vessel exploitation, thus optimizing the sequential tasks of seeking blood vessels and pericyte-associated sites of privileged intravasation