Imaging the symmetry breaking of molecular orbitals in carbon nanotubes

Carbon nanotubes have attracted considerable interest for their unique electronic properties. They are fascinating candidates for fundamental studies of one dimensional materials as well as for future molecular electronics applications. The molecular orbitals of nanotubes are of particular importance as they govern the transport properties and the chemical reactivity of the system. Here we show for the first time a complete experimental investigation of molecular orbitals of single wall carbon nanotubes using atomically resolved scanning tunneling spectroscopy. Local conductance measurements show spectacular carbon-carbon bond asymmetry at the Van Hove singularities for both semiconducting and metallic tubes, demonstrating the symmetry breaking of molecular orbitals in nanotubes. Whatever the tube, only two types of complementary orbitals are alternatively observed. An analytical tight-binding model describing the interference patterns of ? orbitals confirmed by ab initio calculations, perfectly reproduces the experimental results

Chromophore Ordering by Confinement into Carbon Nanotubes

International audienceWe report an experimental study on the confinement of oligothiophene derivatives into single-walled carbon nanotubes over a large range of diameter (from 0.68 to 1.93 nm). We evidence by means of Raman spectroscopy and transmission electron microscopy that the supramolecular organizations of the confined oligothiophenes depend on the nanocontainer size. The Raman Radial Breathing Mode frequency is shown to be monitored by both the number of confined molecules into a nanotube section and the competition between oligothiophene/oligothiophene and oligothiophene/tube wall interactions. We finally propose simple Raman criteria to characterize oligothiophene supramolecular organization at the nanoscale

Global hybrids from the semiclassical atom theory satisfying the local density linear response

We propose global hybrid approximations of the exchange-correlation (XC) energy functional which reproduce well the modified fourth-order gradient expansion of the exchange energy in the semiclassical limit of many-electron neutral atoms and recover the full local density approximation (LDA) linear response. These XC functionals represent the hybrid versions of the APBE functional [Phys. Rev. Lett. 106, 186406, (2011)] yet employing an additional correlation functional which uses the localization concept of the correlation energy density to improve the compatibility with the Hartree-Fock exchange as well as the coupling-constant-resolved XC potential energy. Broad energetical and structural testings, including thermochemistry and geometry, transition metal complexes, non-covalent interactions, gold clusters and small gold-molecule interfaces, as well as an analysis of the hybrid parameters, show that our construction is quite robust. In particular, our testing shows that the resulting hybrid, including 20\% of Hartree-Fock exchange and named hAPBE, performs remarkably well for a broad palette of systems and properties, being generally better than popular hybrids (PBE0 and B3LYP). Semi-empirical dispersion corrections are also provided.Comment: 12 pages, 4 figure

Fermi level shift in carbon nanotubes by dye confinement

International audienceDye confinement into carbon nanotube significantly affects the electronic charge density distribution of the final hybrid system. Using the electron-phonon coupling sensitivity of the Raman G-band, we quantify experimentally how charge transfer from thiophene oligomers to single walled carbon nanotube is modulated by the diameter of the nano-container and its metallic or semiconducting character. This charge transfer is shown to restore the electron-phonon coupling into defected metallic nanotubes. For sub-nanometer diameter tube, an electron transfer optically activated is observed when the excitation energy matches the HOMO-LUMO transition of the confined oligothiophene. This electron doping accounts for an important enhancement of the photoluminescence intensity up to a factor of nearly six for optimal confinement configuration. This electron transfer shifts the Fermi level, acting on the photoluminescence efficiency. Therefore, thiophene oligomer encapsulation allows modulating the electronic structure and then the optical properties of the hybrid system

Peptidasas y lipasas vegetales como biocatalizadores en la obtención de tensioactivos derivados de aminoácidos

Se sintetizaron compuestos derivados de aminoácidos con potencial actividad superficial mediante reacciones de condensación de Arg, Gly, Ala y Leu con alquilaminas y alcoholes alifáticos (decil y dodecilamina; decanol y dodecanol). Dichas reacciones fueron catalizadas por peptidasas vegetales cisteínicas, una de origen comercial (papaína) y otra extraída del látex de la enredadera nativa Araujia sericifera. Asimismo, se probó la capacidad de la lipasa obtenida de dicho látex para catalizar estas reacciones. Las estrategias ensayadas fueron control termodinámico y control cinético. Las alquilamidas derivadas de Ala y Gly pudieron ser sintetizadas mediante el enfoque termodinámico con muy buenos rendimientos para Ala pero más bajos para Gly. Dado que los derivados de Leu no pudieron ser sintetizados mediante esta estrategia, y para aumentar el rendimiento de los derivados de Gly, se ensayó la síntesis por control cinético previa esterificación de los dadores de acilo. Mediante esta metodología, se obtuvieron rendimientos cercanos al 90% para ambos dadores de acilos empleando papaína. Se utilizó este enfoque para sintetizar los derivados de Arg utilizando los tres biocatalizadores y los cuatro nucleófilos, resultando papaína la enzima más eficiente. Se escalaron las síntesis de las alquilamidas utilizando papaína como biocatalizador, a fin de caracterizar los productos obtenidos.Amino acid-based compounds with potential surface activity were synthezised by condensation reactions between Arg, Gly, Ala and Leu with alkyl amines and aliphatic alcohols (decyl and dodecyl amines; decanol and dodecanol).Reactions were catalyzed by plant cysteine peptidases, one form commercial origin (papain) and another obtained from the native vine Araujia sericifera latex. A lipase obtained from the same plant latex (ASL) was also proved as biocatalyst. Both approaches, thermodynamic and kinetic controlled synthesis were tested. Ala derivatives were successfully synthezised under the thermodynamic approach, but the syntheses of Gly derivatives showed lower yields and Leu derivatives could not be synthezised. Kinetic controlled syntheses were tested after esterification of acyl donors. Higher yields of the Gly derivatives, as well as high yields of Leu derivatives could be reached using papain under this approach. Kinetic controlled synthesis was applied to produce the Arg derivatives using the three biocatalysts and the four nucleophiles, being papain the most efficient enzyme. Syntheses of alkylamides were scaled up using papain as biocatalyst in order to have enough product mass for characterization.Centro de Investigación de Proteínas VegetalesLaboratorio de Estudio de Compuestos OrgánicosLaboratorio de Investigación y Desarrollo de Métodos Analíticos (LIDMA

Clinical Study Is IgG4-Related Disease a Cause of Xerostomia? A Cohort Study of 60 Patients

Objective. Immunoglobulin-G4-(IgG4-) related disease (IgG4 RD) is a fibrosing process characterized by a significant infiltration of IgG4-secreting plasma cells. IgG4 RD can affect almost all organs including salivary glands. Whether IgG4 RD plays a role in the development of sicca syndrome and particularly dry mouth syndrome remains to be investigated. Methods. We conducted a monocentric cohort study for two years to search for IgG4 RD features in patients with dry mouth syndrome using immunostainings of labial salivary gland specimens with anti-IgG4 antibody. Results. Among 60 patients presenting with dry mouth syndrome who underwent labial salivary gland biopsy, 18 showed positive immunostaining with the anti-IgG4 antibody including 4 patients with typical systemic IgG4 RD. Five also fulfilled criteria for Sjögren's syndrome. Conclusion. These findings suggest that clinical forms of IgG4 RD salivary involvement without salivary swelling may occur. This salivary involvement is probably overlooked in everyday practice and could represent a mild form of IgG4 RD

Clinical Study Is IgG4-Related Disease a Cause of Xerostomia? A Cohort Study of 60 Patients

Objective. Immunoglobulin-G4-(IgG4-) related disease (IgG4 RD) is a fibrosing process characterized by a significant infiltration of IgG4-secreting plasma cells. IgG4 RD can affect almost all organs including salivary glands. Whether IgG4 RD plays a role in the development of sicca syndrome and particularly dry mouth syndrome remains to be investigated. Methods. We conducted a monocentric cohort study for two years to search for IgG4 RD features in patients with dry mouth syndrome using immunostainings of labial salivary gland specimens with anti-IgG4 antibody. Results. Among 60 patients presenting with dry mouth syndrome who underwent labial salivary gland biopsy, 18 showed positive immunostaining with the anti-IgG4 antibody including 4 patients with typical systemic IgG4 RD. Five also fulfilled criteria for Sjögren's syndrome. Conclusion. These findings suggest that clinical forms of IgG4 RD salivary involvement without salivary swelling may occur. This salivary involvement is probably overlooked in everyday practice and could represent a mild form of IgG4 RD

Evaluation et prise en charge de la surcharge en fer post-greffe recommandations de la SFGM-TC

peer reviewedAssessment and management of post-transplant iron overload: Guidelines of the Francophone Society of Marrow Transplantation and Cellular Therapy (SFGM-TC) To harmonize clinical practice in hematopoietic stem cell transplantation, the Francophone Society of Bone Marrow Transplantation and Cell Therapy (SFGM-TC) set up the sixth annual series of workshops which brought together practitioners from all member centers and took place in September 2015 in Lille. The main aim of this session was to describe the impact, evaluation and treatment of post-transplant iron overload

Synthesis and asymmetric hydrogenation of (3E)-1-benzyl-3-[(2-oxopyridin-1(2H)-yl)methylidene]piperidine-2,6-dione

The synthesis of (3E)-1-benzyl-3-[(2-oxopyridin-1(2H)-yl)methylidene]piperidine-2,6-dione 4 from N-benzylglutarimide was achieved in three steps. The asymmetric hydrogenation of 4 gave either the product of partial reduction (10) or full reduction (13), depending on the catalyst which was employed, in high ee in each case. Attempts at asymmetric transfer hydrogenation (ATH) of 4 resulted in formation of a racemic product