Interplay between symmetry and spin-orbit coupling on graphene nanoribbons

We study the electronic structure of chiral and achiral graphene nanoribbons with symmetric edges, including curvature and spin-orbit effects. Curved ribbons show spin-split bands, whereas flat ribbons present spin-degenerate bands. We show that this effect is due to the breaking of spatial inversion symmetry in curved graphene nanoribbons, while flat ribbons with symmetric edges possess an inversion center, regardless of their having chiral or achiral edges. We find an enhanced edge-edge coupling and a substantial gap in narrow chiral nanoribbons, which is not present in zigzag ribbons of similar width. We attribute these size effects to the mixing of the sublattices imposed by the edge geometry, yielding a behavior of chiral ribbons that is distinct from those with pure zigzag edges. © 2013 American Physical Society.This work has been partially supported by the Spanish Ministries of Science and Innovation (MICINN) and Economy and Competitivity (MINECO) DGES under Grants No. MAT2009-14578-C03-03, No. PIB2010BZ-00512, No. FIS2010-21282-C02-02, No. FIS2011-23713, No.MAT2012-38045-C04-04, and No. FIS2012-33521.Peer Reviewe

Vacancy induced zero energy modes in graphene stacks: The case of ABC trilayer

The zero energy modes induced by vacancies in ABC stacked trilayer graphene are investigated. Depending on the position of the vacancy, a new zero energy solution is realised, different from those obtained in multilayer compounds with Bernal stacking. The electronic modification induced in the sample by the new vacancy states is characterised by computing the local density of states and their localisation properties are studied by the inverse participation ratio. We also analyse the situation in the presence of a gap in the spectrum due to a perpendicular electric field.Comment: 6 pages, 4 figures Published in special issue: Exploring Graphene, Recent Research Advance

Cancer-derived exosomes loaded with ultrathin palladium nanosheets for targeted bioorthogonal catalysis

The transformational impact of bioorthogonal chemistries has inspired new strategies for the in vivo synthesis of bioactive agents through non-natural means. Among these, Pd catalysts have played a prominent role in the growing subfield of bioorthogonal catalysis by producing xenobiotics and uncaging biomolecules in living systems. However, delivering catalysts selectively to specific cell types still lags behind catalyst development. Here, we have developed a bioartificial device comprising cancer-derived exosomes that are loaded with Pd catalysts by a method that enables the controlled assembly of Pd nanosheets directly inside the vesicles. This hybrid system mediates Pd-triggered dealkylation reactions in vitro and inside cells, and displays preferential tropism for their progenitor cells. The use of Trojan exosomes to deliver abiotic catalysts into designated cancer cells creates the opportunity for a new targeted therapy modality; that is, exosome-directed catalyst prodrug therapy, whose first steps are presented herein with the cell-specific release of the anticancer drug panobinostat

Momentum dependence of spin-orbit interaction effects in single-layer and multi-layer transition metal dichalcogenides

One of the main characteristics of the new family of two-dimensional crystals of semiconducting transition metal dichalcogenides (TMDs) is the strong spin-orbit interaction, which makes them very promising for future applications in spintronics and valleytronics devices. Here we present a detailed study of the effect of spin-orbit coupling (SOC) on the band structure of single-layer and bulk TMDs, including explicitly the role of the chalcogen orbitals and their hybridization with the transition metal atoms. To this aim, we combine density functional theory (DFT) calculations with a Slater-Koster tight-binding (TB) model. Whereas most of the previous TB models have been restricted to the K and K' points of the Brillouin zone (BZ), here we consider the effect of SOC in the whole BZ, and the results are compared to the band structure obtained by DFT methods. The TB model is used to analyze the effect of SOC in the band structure, considering separately the contributions from the transition metal and the chalcogen atoms. Finally, we present a scenario where, in the case of strong SOC, the spin/orbital/valley entanglement at the minimum of the conduction band at Q can be probed and be of experimental interest in the most common cases of electron-doping reported for this family of compounds

Modulación de factores de transcripción Nrf2 y NF-κB por esculetina en células leucémicas humanas

La esculetina (6,7-dihidroxicumarina) es un antioxidante que modula el balance redox en diferentes células. Además posee propiedades antiinflamatorias y antitumorales. Se ha estudiado el efecto antitumoral de esculetina en células de leucemia humana promielocítica aguda NB4. Se ha analizado la respuesta antioxidante celular (actividad de la enzima superóxido dismutasa –SOD–) con la modulación de los niveles de factores de transcripción (Nrf2 y NF-κB)

Modulación de factores de transcripción Nrf2 y NF-κB por esculetina en células leucémicas humanas

La esculetina (6,7-dihidroxicumarina) es un antioxidante que modula el balance redox en diferentes células. Además posee propiedades antiinflamatorias y antitumorales. Se ha estudiado el efecto antitumoral de esculetina en células de leucemia humana promielocítica aguda NB4. Se ha analizado la respuesta antioxidante celular (actividad de la enzima superóxido dismutasa –SOD–) con la modulación de los niveles de factores de transcripción (Nrf2 y NF-κB)