Search results for "Raphe"

From Behavior of Water on Hydrophobic Graphene Surfaces to Ultra-Confinement of Water in Carbon Nanotubes

2021

In recent years and with the achievement of nanotechnologies, the development of experiments based on carbon nanotubes has allowed to increase the ionic permeability and/or selectivity in nanodevices. However, this new technology opens the way to many questionable observations, to which theoretical work can answer using several approximations. One of them concerns the appearance of a negative charge on the carbon surface, when the latter is apparently neutral. Using first-principles density functional theory combined with molecular dynamics, we develop here several simulations on different systems in order to understand the reactivity of the carbon surface in low or ultra-high confinement. …

Polycyclic aromatic chains on metals and insulating layers by repetitive [3+2] cycloadditions

2020

The vast potential of organic materials for electronic, optoelectronic and spintronic devices entails substantial interest in the fabrication of π-conjugated systems with tailored functionality directly at insulating interfaces. On-surface fabrication of such materials on non-metal surfaces remains to be demonstrated with high yield and selectivity. Here we present the synthesis of polyaromatic chains on metallic substrates, insulating layers, and in the solid state. Scanning probe microscopy shows the formation of azaullazine repeating units on Au(111), Ag(111), and h-BN/Cu(111), stemming from intermolecular homo-coupling via cycloaddition reactions of CN-substituted polycyclic aromatic az…

Energy Storage: Giant Enhancement in the Supercapacitance of NiFe–Graphene Nanocomposites Induced by a Magnetic Field (Adv. Mater. 28/2019)

2019

Substrate and atmosphere influence on oxygen p-doped graphene

2016

Abstract The mechanisms responsible for p-type doping of substrate supported monolayer graphene (Gr) by thermal treatments in oxygen ambient have been investigated by micro-Raman spectroscopy, atomic force microscopy (AFM) and X-ray Photoelectron Spectroscopy (XPS), considering commonly employed dielectric substrates, such as SiO 2 and Al 2 O 3 thin films grown on Si. While a high p-type doping (∼10 13  cm −2 ) is observed for Gr on SiO 2 , no significant doping is found for Gr samples on the Al 2 O 3 substrate, suggesting a key role of the Gr/SiO 2 interface states in the trapping of oxygen responsible for the Gr p-type doping. Furthermore, we investigated the doping stability of Gr on SiO…

General Approach to the Description of Fundamental Properties of Disordered Nanosized Media

2017

Physics of non-regular nanosystems is a branch of physics dealing with nanoagents – nanoparticles when non-regular nanosized morphological characteristics predetermine the nature and essence of physical phenomenon (nanophenomenon). In particular, multiple technological interfaces of nanoparticles with morphologically regular systems imply a creation of micro- or mesostructures with essential nanodimensional effects (e.g. in various schemes of functionalization of nanocarbon systems, viz. carbon nanotubes (CNTs), graphene nanoribbons (GNRs), graphene nanoflakes (GNFs), carbon-based nanoaerogels and nanofoams, etc.). However, classes of nanomaterials, in addition to nanocarbon systems, can be…

Patterning and tuning of electrical and optical properties of graphene by laser induced two-photon oxidation

2015

Graphene, being an ultrathin, durable, flexible, transparent material with superior conductivity and unusual optical properties, promises many novel applications in electronics, photonics and optoelectronics. For applications in electronics, patterning and modification of electrical properties is very desirable since pristine graphene has no band gap. Here we demonstrate a simple all-optical patterning method for graphene, based on laser induced two-photon oxidation. By tuning the intensity of irradiation and the number of pulses the level of oxidation can be controlled to high precision and, therefore, a band gap can be introduced and electrical and optical properties can be continuously t…

Modified Nanocarbons for Catalysis

2018

Nanocarbons represent useful scaffolds in the preparation of last generation nanostructured catalysts, and their chemical functionalization through covalent or non-covalent modification is becoming an important tool for introducing well-distributed anchoring points and, in the meantime, could be the first step toward the assembling of hybrid nanostructured materials with a hierarchical order. In this Review are reported synthesis and catalytic applications of chemically modified nanocarbons such as fullerene, carbon nanotubes, graphene, nanohorns and nanodiamonds in organocatalytic and metal-based (metal nanoparticles, organometallic complexes) reactions, covering major chemical reactions e…

Natural optical anisotropy of h-BN: Highest giant birefringence in a bulk crystal through the mid-infrared to ultraviolet range

2018

The giant birefringence of layered h-BN was demonstrated by analyzing the interference patterns in reflectance and transmittance measurements in the mid-infrared to the deep ultraviolet energy range. The refractive index for polarization perpendicular to the c axis is much higher than the refractive index for polarization parallel to the c axis, and it displays a strong increase in the ultraviolet range that is attributed to the huge excitonic effects arising from the unique electronic structure of h-BN. Thus, h-BN is shown to exhibit a giant negative birefringence that ranges from -0.7 in the visible to -2 in the deep ultraviolet close to the band gap. The electronic dielectric constants f…

Regulation of noradrenergic coerulean neuronal firing mediated by 5-HT2 receptors: involvement of the prepositus hypoglossal nucleus.

1991

Abstract Previous studies have indicated a 5-HT2-mediated inhibitory influence on unit activity in the locus coeruleus. In the present work, attempts were made to determine which area(s) of the brain is (are) involved in this effect: (1) Microiontophoretic application of serotoninergic compounds (quipazine, ketanserin, RU 24969 (Roussel Uclaf), 8-hydroxy-2(di-n-propylamino) tetralin (8-OH-DPAT), metergoline, serotonin) in the locus coeruleus, did not alter the coerulean discharge. Local microinjection of quipazine or ketanserin in the area of the locus coeruleus, as well as in one of its major afferents, the prepositus hypoglossi, had no effect on the unit activity in the locus coeruleus. 1…

Functional biopolymer-based nanocomposites incorporating graphene nanoplatelets

2016

The effectiveness of the antimicrobial activity over time is mainly determined by the release rate of the antimicrobial compounds. The rate of release depends on different factors such as preparation method, environmental conditions, interactions between antimicrobial and matrix. In this regard, nanoparticles can potentially be used to control the release of antimicrobial agents. Moreover, it is well known that the incorporation of nano-sized fillers into a biopolymeric matrix is an effective way to improve its properties. Aim of this work was to prepare and characterize biopolymer-based nanocomposites with antimicrobial properties. In particular, graphene nanoplatelets (GnPs) as fillers an…