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1.
Rhinology ; 2024 Jun 07.
Artigo em Inglês | MEDLINE | ID: mdl-38848046

RESUMO

BACKGROUND: Research on the immune mechanism behind chronic rhinosinusitis (CRS) has revealed various new endotypes, leading to targeted therapies, especially for severe uncontrolled CRS. Biologics are novel therapeutic strategies providing targeted treatment for the difficult-to-treat recalcitrant CRSwNP patients. Dupilumab is a fully human-derived monoclonal antibody that binds to IL4Rα, inhibiting the signalling of both IL-4 and IL-13. In Hungary, it is approved for the treatment of uncontrolled CRSwNP according to criteria based on the EPOS2020 and the Hungarian guidelines. METHODOLOGY: This study aimed to collect and evaluate real-world therapeutic data of CRSwNP patients treated with dupilumab. One hundred thirty-five patients from eight different referral centres have been enrolled in this study, who received dupilumab since 2020. All subjects were adult patients (over 18 years) with uncontrolled CRSwNP. Baseline data collection included demographics, medical history, previous surgeries, related comorbidities, total endoscopic nasal polyp score (NPS), SNOT22, nasal congestion parameters measured with visual analogue scale (VAS) and nasal obstruction evaluation scale (NOSE), loss of smell score (LSS) and eosinophil count. 300 mg dupilumab was administered subcutaneously every second week. Follow up visits were performed after 6 and 12 months. RESULTS: After 6 and 12 months of treatment significant improvement was detected in all clinical parameters. Safety was proved, no severe side effects occurred, and no rescue treatment was necessary. CONCLUSIONS: Our real-life findings show that continuous dupilumab treatment is effective and safe in daily clinical practice in CRSwNP and other type 2 comorbidities such as bronchial asthma and NERD.

2.
Phys Rev E ; 108(2-2): 025205, 2023 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-37723798

RESUMO

Recent validation experiments on laser irradiation of polymer foils with and without implanted golden nanoparticles are discussed. First we analyze characteristics of craters, formed in the target after its interaction with the laser beam. Preliminary experimental results show significant production of deuterons when both the energy of laser pulse and concentration of nanoparticles are high enough. We consider the deuteron production via the nuclear transmutation reactions p+C→d+X where protons are accelerated by the Coulomb field generated in the target plasma. We argue that maximal proton energy can be above threshold values for these reactions and the deuteron yield may noticeably increase due to presence of nanoparticles.

3.
Int J Mol Sci ; 23(21)2022 Nov 05.
Artigo em Inglês | MEDLINE | ID: mdl-36362358

RESUMO

In this work, the effects of femtosecond laser irradiation and doping with plasmonic gold nanorods on the degree of conversion (DC) of a urethane dimethacrylate (UDMA)-triethylene glycol dimethacrylate (TEGDMA) nanocomposite were investigated. The UDMA-TEGDMA photopolymer was prepared in a 3:1 weight ratio and doped with dodecanethiol- (DDT) capped gold nanorods of 25 × 75 or 25 × 85 nm nominal diameter and length. It was found that the presence of the gold nanorods alone (without direct plasmonic excitation) can increase the DC of the photopolymer by 6-15%. This increase was found to be similar to what could be achieved with a control heat treatment of 30 min at 180 °C. It was also shown that femtosecond laser impulses (795 nm, 5 mJ pulse energy, 50 fs pulse length, 2.83 Jcm-2 fluence), applied after the photopolymerization under a standard dental curing lamp, can cause a 2-7% increase in the DC of undoped samples, even after thermal pre-treatment. The best DC values (12-15% increase) were obtained with combined nanorod doping and subsequent laser irradiation close to the plasmon resonance peak of the nanorods (760-800 nm), which proves that the excited plasmon field can directly facilitate double bond breakage (without thermoplasmonic effects due to the short pulse length) and increase the crosslink density independently from the initial photopolymerization process.


Assuntos
Nanocompostos , Nanotubos , Ouro , Lasers
5.
Entropy (Basel) ; 24(4)2022 Apr 06.
Artigo em Inglês | MEDLINE | ID: mdl-35455177

RESUMO

We present a new family of exact solutions of dissipative fireball hydrodynamics for arbitrary bulk and shear viscosities. The main property of these solutions is a spherically symmetric, Hubble flow field. The motivation of this paper is mostly academic: we apply non-relativistic kinematics for simplicity and clarity. In this limiting case, the theory is particularly clear: the non-relativistic Navier-Stokes equations describe the dissipation in a well-understood manner. From the asymptotic analysis of our new exact solutions of dissipative fireball hydrodynamics, we can draw a surprising conclusion: this new class of exact solutions of non-relativistic dissipative hydrodynamics is asymptotically perfect.

6.
Materials (Basel) ; 12(9)2019 Apr 30.
Artigo em Inglês | MEDLINE | ID: mdl-31052351

RESUMO

Since damping in lightweight floors is usually low, dynamic amplification can be rather high. Long rectangular plates subjected to concentrated loads are often investigated by a replacement beam with a so called "effective width". Although this approach is a reliable tool for static loads, the steady-state dynamic response of beams and long plates subjected to periodic loads are significantly different. The maximum displacements and accelerations of beams (and of not-long rectangular plates) are obtained by using a dynamic amplification factor, which in the case of resonance is equal to 1 / 2 ξ , where ξ is the damping ratio. For long plates (and for not-long orthotropic rib-stiffened plates), as discussed in the paper, the response and the amplification factor are substantially different from those of beams. Hence, design based on effective width may lead to 2-4 times higher acceleration than the real values. In an economic design, to avoid unnecessary damping enhancement, this effect must be taken into account.

7.
Nanomaterials (Basel) ; 9(5)2019 May 17.
Artigo em Inglês | MEDLINE | ID: mdl-31108971

RESUMO

Gas/vapor sensors based on photonic band gap-type materials are attractive as they allow a quick optical readout. The photonic nanoarchitectures responsible for the coloration of the wing scales of many butterfly species possessing structural color exhibit chemical selectivity, i.e., give vapor-specific optical response signals. Modeling this complex physical-chemical process is very important to be able to exploit the possibilities of these photonic nanoarchitectures. We performed measurements of the ethanol vapor concentration-dependent reflectance spectra of the Albulina metallica butterfly, which exhibits structural color on both the dorsal (blue) and ventral (gold-green) wing sides. Using a numerical analysis of transmission electron microscopy (TEM) images, we revealed the details of the photonic nanoarchitecture inside the wing scales. On both sides, it is a 1D + 2D structure, a stack of layers, where the layers contain a quasi-ordered arrangement of air voids embedded in chitin. Next, we built a parametric simulation model that matched the measured spectra. The reflectance spectra were calculated by ab-initio methods by assuming variable amounts of vapor condensed to liquid in the air voids, as well as vapor concentration-dependent swelling of the chitin. From fitting the simulated results to the measured spectra, we found a similar swelling on both wing surfaces, but more liquid was found to concentrate in the smaller air voids for each vapor concentration value measured.

8.
Cochrane Database Syst Rev ; 4: CD008205, 2019 04 15.
Artigo em Inglês | MEDLINE | ID: mdl-30985922

RESUMO

BACKGROUND: Survival rates have greatly improved as a result of more effective treatments for childhood cancer. Unfortunately, the improved prognosis has been accompanied by the occurrence of late, treatment-related complications. Liver complications are common during and soon after treatment for childhood cancer. However, among long-term childhood cancer survivors, the risk of hepatic late adverse effects is largely unknown. To make informed decisions about future cancer treatment and follow-up policies, it is important to know the risk of, and associated risk factors for, hepatic late adverse effects. This review is an update of a previously published Cochrane review. OBJECTIVES: To evaluate all the existing evidence on the association between antineoplastic treatment (that is, chemotherapy, radiotherapy involving the liver, surgery involving the liver and BMT) for childhood cancer and hepatic late adverse effects. SEARCH METHODS: We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2018, Issue 1), MEDLINE (1966 to January 2018) and Embase (1980 to January 2018). In addition, we searched reference lists of relevant articles and scanned the conference proceedings of the International Society of Paediatric Oncology (SIOP) (from 2005 to 2017) and American Society of Pediatric Hematology/Oncology (ASPHO) (from 2013 to 2018) electronically. SELECTION CRITERIA: All studies, except case reports, case series, and studies including fewer than 10 patients that examined the association between antineoplastic treatment for childhood cancer (aged 18 years or less at diagnosis) and hepatic late adverse effects (one year or more after the end of treatment). DATA COLLECTION AND ANALYSIS: Two review authors independently performed the study selection and 'risk of bias' assessment. The 'risk of bias' assessment was based on earlier checklists for observational studies. For the original version of the review, two review authors independently performed data extraction. For the update of the review, the data extraction was performed by one reviewer and checked by another reviewer. MAIN RESULTS: Thirteen new studies were identified for the update of this review. In total, we included 33 cohort studies including 7876 participants investigating hepatic late adverse effects after antineoplastic treatment (especially chemotherapy and radiotherapy) for different types of childhood cancer, both haematological and solid malignancies. All studies had methodological limitations. The prevalence of hepatic late adverse effects, all defined in a biochemical way, varied widely, between 0% and 84.2%. Selecting studies where the outcome of hepatic late adverse effects was well-defined as alanine aminotransferase (ALT) above the upper limit of normal, indicating cellular liver injury, resulted in eight studies. In this subgroup, the prevalence of hepatic late adverse effects ranged from 5.8% to 52.8%, with median follow-up durations varying from three to 23 years since cancer diagnosis in studies that reported the median follow-up duration. A more stringent selection process using the outcome definition of ALT as above twice the upper limit of normal, resulted in five studies, with a prevalence ranging from 0.9% to 44.8%. One study investigated biliary tract injury, defined as gamma-glutamyltransferase (γGT) above the upper limit of normal and above twice the upper limit of normal and reported a prevalence of 5.3% and 0.9%, respectively. Three studies investigated disturbance in biliary function, defined as bilirubin above the upper limit of normal and reported prevalences ranging from 0% to 8.7%. Two studies showed that treatment with radiotherapy involving the liver (especially after a high percentage of the liver irradiated), higher BMI, and longer follow-up time or older age at evaluation increased the risk of cellular liver injury in multivariable analyses. In addition, there was some suggestion that busulfan, thioguanine, hepatic surgery, chronic viral hepatitis C, metabolic syndrome, use of statins, non-Hispanic white ethnicity, and higher alcohol intake (> 14 units per week) increase the risk of cellular liver injury in multivariable analyses. Chronic viral hepatitis was shown to increase the risk of cellular liver injury in six univariable analyses as well. Moreover, one study showed that treatment with radiotherapy involving the liver, higher BMI, higher alcohol intake (> 14 units per week), longer follow-up time, and older age at cancer diagnosis increased the risk of biliary tract injury in a multivariable analysis. AUTHORS' CONCLUSIONS: The prevalence of hepatic late adverse effects among studies with an adequate outcome definition varied considerably from 1% to 53%. Evidence suggests that radiotherapy involving the liver, higher BMI, chronic viral hepatitis and longer follow-up time or older age at follow-up increase the risk of hepatic late adverse effects. In addition, there may be a suggestion that busulfan, thioguanine, hepatic surgery, higher alcohol intake (>14 units per week), metabolic syndrome, use of statins, non-Hispanic white ethnicity, and older age at cancer diagnosis increase the risk of hepatic late adverse effects. High-quality studies are needed to evaluate the effects of different therapy doses, time trends, and associated risk factors after antineoplastic treatment for childhood cancer.


Assuntos
Antineoplásicos/efeitos adversos , Doença Hepática Induzida por Substâncias e Drogas , Neoplasias/tratamento farmacológico , Neoplasias/radioterapia , Radioterapia/efeitos adversos , Adolescente , Alanina Transaminase/metabolismo , Antineoplásicos/uso terapêutico , Criança , Pré-Escolar , Humanos , Lactente , Hepatopatias , gama-Glutamiltransferase/metabolismo
9.
Sci Rep ; 9(1): 2338, 2019 02 20.
Artigo em Inglês | MEDLINE | ID: mdl-30787341

RESUMO

Color is a widely used communication channel in the living world for a variety of functions ranging from sexual communication to warning colors. A particularly rich spectrum of colors appears on the wings of many butterflies. The males of lycaenid butterflies often exhibit a conspicuous blue coloration generated by photonic nanoarchitectures on their dorsal wing surfaces. Using UV-VIS spectroscopy, we investigated the spatio-temporal variations of this coloration for Polyommatus icarus butterflies, considering an interval of more than 100 years and a geographical range spanning Europe (west) and Asia (east). The blue coloration in Hungary is very stable both within a year (three broods typical in Hungary) and within the period of 100 years (more than 300 generations). East-west geographic variation was investigated among 314 male P. icarus butterflies. In agreement with earlier genetic and morphometric studies, it was found that the western males are not divided in distinct lineages. Clear differences in coloration were found between the eastern and western groups, with a transition in the region of Turkey. These differences are tentatively attributed to bottleneck effects during past glaciations.


Assuntos
Borboletas/anatomia & histologia , Borboletas/classificação , Filogeografia , Animais , Ásia , Europa (Continente) , Masculino , Fenômenos Ópticos , Análise de Componente Principal , Asas de Animais/anatomia & histologia
10.
Icarus ; 321: 346-357, 2019 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-34316081

RESUMO

Both the northern and southern arms of Kasei Valles are occupied by platy-ridged flood lavas. We have mapped these flows and examined their morphology to better understand their emplacement. The lavas were emplaced as high-flux, turbulent flows (exceeding 106 m3 s-1). Lava in southern Kasei Valles can be traced back up onto the Tharsis rise, which is also the likely source of lavas in the northern arm. These eruptions were similar to, but somewhat smaller than, the Athabasca Valles flood lava in Elysium Planitia, with estimated volumes of >1200 km3 here and 5000 km3 in Athabasca Valles. The flood lavas in both Kasei and Athabasca Valles have evidence for distal inflation as well as widespread drainage or volume loss in medial areas; this may be an important characteristic of many large, recent Martian eruptions. Despite their great size and flux, the Kasei Valles flood lavas are only a late modification to the valley system capable of only modest local erosion. The more vigorous Athabasca Valles lava may have been capable of somewhat more erosion in its smaller valley system.

11.
Inorg Chem ; 57(21): 13679-13692, 2018 Nov 05.
Artigo em Inglês | MEDLINE | ID: mdl-30351069

RESUMO

[NH4Cu(OH)MoO4] as active photocatalyst in the decomposition of Congo Red when irradiated by UV or visible light has been prepared in an unusual ammonia/water ligand exchange reaction of [tetraamminecopper(II)] molybdate, [Cu(NH3)4]MoO4. [Cu(NH3)4]MoO4 was subjected to moisture of open air at room temperature. Light blue orthorhombic [Cu(NH3)(H2O)3]MoO4 was formed in 2 days as a result of an unexpected solid/gas phase ammonia-water ligand exchange reaction. This complex does not lose its last ammonia ligand on further standing in open air; however, a slow quasi-intramolecular (self)-protonation reaction takes place in 2-4 weeks, producing a yellowish-green microcrystalline material, which has been identified as a new compound, [NH4Cu(OH)MoO4], ( a = 10,5306 Å, b = 6.0871 Å, c = 8.0148 Å, ß = 64,153°, C2, Z = 4). Mechanisms are proposed for both the sequential ligand exchange and the self-protonation reactions supported by ab initio quantum-chemical calculations and deuteration experiments as well. The [Cu(NH3)(H2O)3]MoO4 intermediate transforms into NH4Cu(OH)(H2O)2MoO4, which loses two waters and yields [NH4Cu(OH)MoO4]. Upon heating, both [Cu(NH3)4]MoO4 and [Cu(NH3)(H2O)3]MoO4 decompose, losing three NH3 and three H2O ligands, respectively, and stable [Cu(NH3)MoO4] is formed from both. The latter can partially be hydrated in boiling water into [NH4Cu(OH)MoO4. This compound can also be prepared in pure form by boiling the saturated aqueous solution of [Cu(NH3)4]MoO4. All properties of [NH4Cu(OH)MoO4] match those of the active photocatalyst described earlier in the literature under the formulas (NH4)2[Cu(MoO4)2] and (NH4)2Cu4(NH3)3Mo5O20.

12.
Sci Rep ; 7(1): 3035, 2017 06 08.
Artigo em Inglês | MEDLINE | ID: mdl-28596579

RESUMO

Patterning graphene into various mesoscopic devices such as nanoribbons, quantum dots, etc. by lithographic techniques has enabled the guiding and manipulation of graphene's Dirac-type charge carriers. Graphene, with well-defined strain patterns, holds promise of similarly rich physics while avoiding the problems created by the hard to control edge configuration of lithographically prepared devices. To engineer the properties of graphene via mechanical deformation, versatile new techniques are needed to pattern strain profiles in a controlled manner. Here we present a process by which strain can be created in substrate supported graphene layers. Our atomic force microscope-based technique opens up new possibilities in tailoring the properties of graphene using mechanical strain.

13.
Sci Rep ; 6: 29726, 2016 07 22.
Artigo em Inglês | MEDLINE | ID: mdl-27445217

RESUMO

MoS2 single layers have recently emerged as strong competitors of graphene in electronic and optoelectronic device applications due to their intrinsic direct bandgap. However, transport measurements reveal the crucial role of defect-induced electronic states, pointing out the fundamental importance of characterizing their intrinsic defect structure. Transmission Electron Microscopy (TEM) is able to image atomic scale defects in MoS2 single layers, but the imaged defect structure is far from the one probed in the electronic devices, as the defect density and distribution are substantially altered during the TEM imaging. Here, we report that under special imaging conditions, STM measurements can fully resolve the native atomic scale defect structure of MoS2 single layers. Our STM investigations clearly resolve a high intrinsic concentration of individual sulfur atom vacancies, and experimentally identify the nature of the defect induced electronic mid-gap states, by combining topographic STM images with ab intio calculations. Experimental data on the intrinsic defect structure and the associated defect-bound electronic states that can be directly used for the interpretation of transport measurements are essential to fully understand the operation, reliability and performance limitations of realistic electronic devices based on MoS2 single layers.

14.
Sci Rep ; 5: 14714, 2015 Oct 07.
Artigo em Inglês | MEDLINE | ID: mdl-26443185

RESUMO

Isolating large-areas of atomically thin transition metal chalcogenide crystals is an important but challenging task. The mechanical exfoliation technique can provide single layers of the highest structural quality, enabling to study their pristine properties and ultimate device performance. However, a major drawback of the technique is the low yield and small (typically < 10 µm) lateral size of the produced single layers. Here, we report a novel mechanical exfoliation technique, based on chemically enhanced adhesion, yielding MoS2 single layers with typical lateral sizes of several hundreds of microns. The idea is to exploit the chemical affinity of the sulfur atoms that can bind more strongly to a gold surface than the neighboring layers of the bulk MoS2 crystal. Moreover, we found that our exfoliation process is not specific to MoS2, but can be generally applied for various layered chalcogenides including selenites and tellurides, providing an easy access to large-area 2D crystals for the whole class of layered transition metal chalcogenides.

15.
J Geophys Res Planets ; 120(11): 1800-1819, 2015 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-29082120

RESUMO

The Athabasca Valles flood lava is among the most recent (<50 Ma) and best preserved effusive lava flows on Mars and was probably emplaced turbulently. The Williams et al. [2005] model of thermal erosion by lava has been applied to what we term "proximal Athabasca," the 75 km long upstream portion of Athabasca Valles. For emplacement volumes of 5000 and 7500 km3 and average flow thicknesses of 20 and 30 m, the duration of the eruption varies between ~11 and ~37 days. The erosion of the lava flow substrate is investigated for three eruption temperatures (1270°C, 1260°C, and 1250°C), and volatile contents equivalent to 0-65 vol% bubbles. The largest erosion depths of ~3.8-7.5 m are at the lava source, for 20 m thick and bubble-free flows that erupted at their liquidus temperature (1270°C). A substrate containing 25 vol% ice leads to maximum erosion. A lava temperature 20°C below liquidus reduces erosion depths by a factor of ~2.2. If flow viscosity increases with increasing bubble content in the lava, the presence of 30-50 vol % bubbles leads to erosion depths lower than those relative to bubble-free lava by a factor of ~2.4. The presence of 25 vol % ice in the substrate increases erosion depths by a factor of 1.3. Nevertheless, modeled erosion depths, consistent with the emplacement volume and flow duration constraints, are far less than the depth of the channel (~35-100 m). We conclude that thermal erosion does not appear to have had a major role in excavating Athabasca Valles.

16.
Nature ; 514(7524): 608-11, 2014 Oct 30.
Artigo em Inglês | MEDLINE | ID: mdl-25355361

RESUMO

The possibility that non-magnetic materials such as carbon could exhibit a novel type of s-p electron magnetism has attracted much attention over the years, not least because such magnetic order is predicted to be stable at high temperatures. It has been demonstrated that atomic-scale structural defects of graphene can host unpaired spins, but it remains unclear under what conditions long-range magnetic order can emerge from such defect-bound magnetic moments. Here we propose that, in contrast to random defect distributions, atomic-scale engineering of graphene edges with specific crystallographic orientation--comprising edge atoms from only one sub-lattice of the bipartite graphene lattice--can give rise to a robust magnetic order. We use a nanofabrication technique based on scanning tunnelling microscopy to define graphene nanoribbons with nanometre precision and well-defined crystallographic edge orientations. Although so-called 'armchair' ribbons display quantum confinement gaps, ribbons with the 'zigzag' edge structure that are narrower than 7 nanometres exhibit an electronic bandgap of about 0.2-0.3 electronvolts, which can be identified as a signature of interaction-induced spin ordering along their edges. Moreover, upon increasing the ribbon width, a semiconductor-to-metal transition is revealed, indicating the switching of the magnetic coupling between opposite ribbon edges from the antiferromagnetic to the ferromagnetic configuration. We found that the magnetic order on graphene edges of controlled zigzag orientation can be stable even at room temperature, raising hopes of graphene-based spintronic devices operating under ambient conditions.

17.
J R Soc Interface ; 9(73): 1745-56, 2012 Aug 07.
Artigo em Inglês | MEDLINE | ID: mdl-22319114

RESUMO

The photonic nanoarchitectures responsible for the blue colour of the males of nine polyommatine butterfly species living in the same site were investigated structurally by electron microscopy and spectrally by reflectance spectroscopy. Optical characterization was carried out on 110 exemplars. The structural data extracted by dedicated software and the spectral data extracted by standard software were inputted into an artificial neural network software to test the specificity of the structural and optical characteristics. It was found that both the structural and the spectral data allow species identification with an accuracy better than 90 per cent. The reflectance data were further analysed using a colour representation diagram built in a manner analogous to that of the human Commission Internationale de l'Eclairage diagram, but the additional blue visual pigment of lycaenid butterflies was taken into account. It was found that this butterfly-specific colour representation diagram yielded a much clearer distinction of the position of the investigated species compared with previous calculations using the human colour space. The specific colours of the investigated species were correlated with the 285 flight-period data points extracted from museum collections. The species with somewhat similar colours fly in distinct periods of the year such that the blue colours are well tuned for safe mate/competitor recognition. This allows for the creation of an effective pre-zygotic isolation mechanism for closely related synchronic and syntopic species.


Assuntos
Comunicação Animal , Lepidópteros/fisiologia , Lepidópteros/ultraestrutura , Pigmentação/efeitos da radiação , Asas de Animais/fisiologia , Asas de Animais/ultraestrutura , Animais , Masculino , Redes Neurais de Computação , Análise Espectral
18.
Nanoscale ; 4(6): 1824-39, 2012 Mar 21.
Artigo em Inglês | MEDLINE | ID: mdl-22080243

RESUMO

One of the most interesting features of graphene is the rich physics set up by the various nanostructures it may adopt. The planar structure of graphene makes this material ideal for patterning at the nanoscale. The breathtakingly fast evolution of research on graphene growth and preparation methods has made possible the preparation of samples with arbitrary sizes. Available sample production techniques, combined with the right patterning tools, can be used to tailor the graphene sheet into functional nanostructures, even whole electronic circuits. This paper is a review of the existing graphene patterning techniques and potential applications of related lithographic methods.


Assuntos
Cristalização/tendências , Grafite/química , Nanoestruturas/química , Nanoestruturas/ultraestrutura , Nanotecnologia/tendências , Substâncias Macromoleculares/química , Teste de Materiais , Conformação Molecular , Tamanho da Partícula , Propriedades de Superfície
19.
Nature ; 479(7374): 485, 2011 Nov 16.
Artigo em Inglês | MEDLINE | ID: mdl-22089137
20.
Nano Lett ; 10(11): 4544-8, 2010 Nov 10.
Artigo em Inglês | MEDLINE | ID: mdl-20945848

RESUMO

Theory has predicted rich and very distinct physics for graphene devices with boundaries that follow either the armchair or the zigzag crystallographic directions. A prerequisite to disclose this physics in experiment is to be able to produce devices with boundaries of pure chirality. Exfoliated flakes frequently exhibit corners with an odd multiple of 30°, which raised expectations that their boundaries follow pure zigzag and armchair directions. The predicted Raman behavior at such crystallographic edges however failed to confirm pure edge chirality. Here, we perform confocal Raman spectroscopy on hexagonal holes obtained after the anisotropic etching of prepatterned pits using carbothermal decomposition of SiO(2). The boundaries of the hexagonal holes are aligned along the zigzag crystallographic direction and leave hardly any signature in the Raman map indicating unprecedented purity of the edge chirality. This work offers the first opportunity to experimentally confirm the validity of the Raman theory for graphene edges.


Assuntos
Modelos Químicos , Nanoestruturas/química , Nanoestruturas/ultraestrutura , Análise Espectral Raman/métodos , Simulação por Computador , Luz , Substâncias Macromoleculares/química , Teste de Materiais , Conformação Molecular , Tamanho da Partícula , Espalhamento de Radiação , Propriedades de Superfície
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