Search results for "Raphe"
showing 10 items of 839 documents
Graphene p-Type Doping and Stability by Thermal Treatments in Molecular Oxygen Controlled Atmosphere
2015
Doping and stability of monolayer low defect content graphene transferred on a silicon dioxide substrate on silicon are investigated by micro-Raman spectroscopy and atomic force microscopy (AFM) during thermal treatments in oxygen and vacuum controlled atmosphere. The exposure to molecular oxygen induces graphene changes as evidenced by a blue-shift of the G and 2D Raman bands, together with the decrease of I2D/IG intensity ratio, which are consistent with a high p-type doping (∼1013 cm-2) of graphene. The successive thermal treatment in vacuum does not affect the induced doping showing this latter stability. By investigating the temperature range 140-350 °C and the process time evolution, …
Segregation of copper oxide on calcium copper titanate surface induced by Graphene Oxide for Water splitting applications
2020
Abstract Photoelectrochemical cells (PEC) are promising devices for hydrogen production via sunlight energy. One of the important challenges in this area is to design photoactive electrodes able to absorb visible light. A good photoelectrochemical behavior depends on the presence of surface active sites to photogenerate current at the lower possible potential for water splitting. Recent investigations in this field are focusing on perovskite materials such as CaCu3Ti4O12 (CCTO) as visible light active electrode due its outstanding structure in which CCTO encloses in its structure a visible light absorbance component (CuO). The presence CuO on the material surface is mainly responsible for t…
Functionalization of Graphene with Molecules and/or Nanoparticles for Advanced Applications
2019
Graphene is considered the material of the third millennium, due to its extraordinary electronic and mechanical properties, and due to the possibility to modulate its conductivity, flexibility, elasticity, transparency, and biocompatibility by bottom-up approach. The possibility to gather the proper- ties of graphene and graphene oxide with those of functional moieties or nanoparticles is herein reviewed. The synthetic approaches proposed, either covalent or noncovalent, are aimed to tune appropriately graphene’s properties for the realization of materials for advanced uses, such as bio- medical applications, sensors, catalysis, and energy devices. In particular, methods based on covalent l…
Synthesis and Electrochemistry of Aluminum Porphycenes. Crystal and Molecular Structure of Methyl-σ-Bonded Aluminum Etioporphycene
1997
The synthesis and characterization of three monomeric aluminum porphycenes with anionic or σ-bonded axial ligands is reported. The investigated compounds are represented as ( EtioPc ) Al ( CH 3) and ( EtioPc ) AlX where EtioPc represents the dianion of etioporphycene and X = Cl − or OH −. Each synthesized complex was characterized by mass spectrometry. 1 H NMR, IR and UV-visible spectroscopies as well as by electrochemistry. Comparisons are made between the properties of complexes in the aluminum etioporphycene series and related chloro- or methyl σ-bonded Al ( III ) porphyrins containing octaethylporphyrin ( OEP ) or tetraphenylporphyrin ( TPP ) macrocycles. Comparisons are also made betw…
Tetrahedra from Aryleneethenylenes – From small Molecules to Luminescent Glasses
2004
AbstractThe fourfold Horner olefination of tetraphenylmethane or –silane with fourp-methyl- phosphonate groups and a variety of aromatic aldehydes with donor groups or extended conjugated systems results in the formation of tetrahedra from four chromophores connected via a central atom. Electronic spectra in solution reveal an electronic interaction between the π-systems. In the solid state, the emission of compounds with a dense packing is nearly identical to the solution spectra, more open structures show significant red shifts. The emission of scaffolds with 1-styrylpyrene chromophores is nearly completely quenched. Most of these tetrahedra are thermally stable up to 420°C. Depending on …
Scritture dimenticate, scritture colonizzate: sistemi grafici e codifiche digitali
2020
L'articolo discute due esempi di come le attuali tecnologie di codifica digitale rappresentino in modo errato gli script non occidentali, in particolare i sistemi grafici dell'India (Devánāgarī) e del Medio Oriente (arabo). Le codifiche digitali come Unicode ereditano tre rigidi principi dalla stampa: (A) 1 ↔ 1, un grafema corrisponde a una lettera; (B) 1 = 1, tutti i grafemi (es. Vocali, consonanti) hanno lo stesso stato; (C) 1, 2, 3…, la scrittura è una sequenza di elementi tutti sullo stesso "livello". Questi principi, tuttavia, non si applicavano ai sistemi grafici europei medievali scritti a mano e non si applicano oggi a quelli non occidentali, compresa la loro versione stampata. In D…
THERMOMECHANICAL DEGRADATION OF A POLYPROPYLENE/GRAPHENE NANOCOMPOSITE
2016
In this work the morphology and the rheological and mechanical properties of a nanocomposite made of a polypropylene with graphene nanoplatelets (GNP) have been investigated as a function of the compounding parameters to evaluate the thermomechanical degradation behaviour of this system. The presence of graphene seems to reduce the thermomechanical degradation of the matrix. A better dispersion of the GNP seems the cause of this behaviour.
Anomalous transport effects on switching currents of graphene-based Josephson junctions
2017
We explore the effect of noise on the ballistic graphene-based small Josephson junctions in the framework of the resistively and capacitively shunted model. We use the non-sinusoidal current-phase relation specific for graphene layers partially covered by superconducting electrodes. The noise induced escapes from the metastable states, when the external bias current is ramped, give the switching current distribution, i.e. the probability distribution of the passages to finite voltage from the superconducting state as a function of the bias current, that is the information more promptly available in the experiments. We consider a noise source that is a mixture of two different types of proce…
Time-dependent Landauer-Büttiker formula: Application to transient dynamics in graphene nanoribbons
2014
In this work we develop a time-dependent extension of the Landauer-B\"uttiker approach to study transient dynamics in time-dependent quantum transport through molecular junctions. A key feature of the approach is that it provides a closed integral expression for the time-dependence of the density matrix of the molecular junction after switch-on of a bias or gate potential which can be evaluated without the necessity of propagating individual single-particle orbitals. This allows for the study of time-dependent transport in large molecular systems coupled to wide band leads. As an application of the formalism we study the transient dynamics of zigzag and armchair graphene nanoribbons of diff…
X-ray crystal structure and antimony-121 Mössbauer spectrum of catecholato bis(1,10-phenanthroline)antimony(III) tetraphenylborate
1985
The crystal structure of the title compound was solved by means of X-ray diffraction at room temperature. The salt consists of a tetrahedral tetraphenylborate anion and a complex cation containing a catecholatoantimony(III) unit chelated by two 1,10-phenanthrolines. The three bidentate ligands are essentially arranged in one half of the Sb coordination sphere, leaving ample space to accomodate the lone pair of electrons. The Mossbauer parameters of the title compound and of the complex (C6H4O2)SbF·Phen were measured and their rationalization accomplished in the light of their respective molecular structures.