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1.
J Colloid Interface Sci ; 530: 424-432, 2018 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-29990778

RESUMO

Silver iodide nanowires have been grown within tubular J-aggregates of the cyanine dye 3,3'-bis(2-sulfopropyl)-5,5',6,6'-tetrachloro-1,1'-dioctylbenzimida-carbo-cyanine (C8S3) from aqueous AgNO3 solutions. Crystal structure analysis by selected area electron diffraction (SAED), high resolution transmission electron microscopy (HRTEM) and energy-dispersive X-ray spectroscopy (EDXS) of single nanowires revealed that they are of silver iodide (AgI), while previously they were presumed to be of metallic silver. Iodine has not been added intentionally, but it is a remnant from the chemical synthesis of the dye and present in a dye:iodine ratio of almost 2:1, as revealed by inductively coupled plasma mass spectrometry (ICP-MS). The AgI wires grow as single crystals with lengths of several 10-100 nm and width of 6.5 ±â€¯0.5 nm. The width and the orientation of the crystal relative to the aggregate axis are defined by the tubular structure of the templating dye aggregate. Caused by the nucleation at the tube wall the main growth is not along the usually preferred [0 0 0 1] direction but along the extension of the basal plane, which is furthermore tilted by an angle of 6°â€¯±â€¯2° against the main axis of the aggregate. This self-assembled system represents an organic-inorganic hybrid system with a well-defined semiconductor nanowire, AgI, that is strictly oriented with respect to the aggregated phase of conjugated molecules.

2.
Nanoscale ; 9(11): 3774-3783, 2017 Mar 17.
Artigo em Inglês | MEDLINE | ID: mdl-28266670

RESUMO

Carbon-based architectures, especially graphene and its derivatives, have recently attracted much attention in the field of biomedicine and biotechnology for their use as pathogen inhibitors or biosensors. One of the major problems in the development of novel virus inhibitor systems is the adaption of the inhibitor to the size of virus particles. We here report the synthesis and biological testing of carbon-based inhibitors differing in size for evaluating the potential size effect on the inhibition of virus entry and replication. In this context, different sized nanomaterials were functionalized with polygylcerol through a "grafting from" polymerization to form new polyvalent nanoarchitectures which can operate as viral inhibitor systems after post-modification. For this purpose a polysulfation was carried out to mimic the heparan sulfates present on cell surfaces that we reasoned would compete with the binding sites of herpes simplex virus type 1 (HSV-1) and equine herpesvirus type 1 (EHV-1), which both cause major global health issues. Our results clearly demonstrate that the inhibitory efficiency is regulated by the size of the polymeric nanomaterials and the degree of sulfation. The best inhibiting graphene sheets were ∼300 nm in size and had a degree of sulfation of ∼10%. Furthermore, it turned out that the derivatives inhibited virus infection at an early stage during entry but did not affect cell-to-cell spread. Overall, tunable polyvalent nanomaterials are promising and efficient virus entry inhibitors, which can likely be used for a broad spectrum of enveloped viruses.


Assuntos
Grafite , Herpesvirus Equídeo 1/fisiologia , Herpesvirus Humano 1/fisiologia , Nanoestruturas , Internalização do Vírus , Animais , Células Cultivadas , Chlorocebus aethiops , Cavalos , Polímeros , Pele/citologia , Células Vero
3.
Sportverletz Sportschaden ; 30(3): 143-8, 2016 Aug.
Artigo em Alemão | MEDLINE | ID: mdl-27490352

RESUMO

BACKGROUND: Injuries of the knee and ankle joint are a serious ongoing problem in soccer. Although there is a variety of prevention programmes, a significant reduction of severe knee injuries has not been observed. Therefore, current strategies for diagnostics and training need to be re-evaluated. OBJECTIVE: Our study aimed to test a totally new intervention strategy (fast response training on the SpeedCourt). The efficiency of this method was evaluated with youth soccer athletes. MATERIALS AND METHODS: 24 young male class A athletes (mean age 18.0 ±â€Š0.7 years) of a local soccer team underwent SpeedCourt training for 7 weeks (1 training session per week = TS) during the regular season of competition. TS contained life-kinetic elements (time of exercise: 15 - 30 seconds, break: 2 minutes) and included a warm-up phase (15 minutes) and fast response training on the SpeedCourt (30 minutes). The players were tested on the SpeedCourt with different tests (Counter Movement Jump (CMJ), shuttle run, tapping, 10-second sprint) before and after the training programme. RESULTS: The univariate single-factor analysis of variance showed significant improvements in all test parameters (η(2)> 0.10). The range varied between η(2) = 0.106 (time of ground contact right leg) und η(2) = 0.730 (reaction time right leg). We did not find any relevant correlations between the tests and parameters. The number of injury-related accidents involving the lower extremities was reduced by about 50 % during defined periods of time. CONCLUSION: Our data revealed that training with fast responses at the SpeedCourt system clearly improved speed and speed strength performance of young soccer athletes, which is remarkable given the low intensity of influences (one TS per week). The increase in performance was accompanied by a significant reduction of the injury rate.


Assuntos
Traumatismos em Atletas/prevenção & controle , Desempenho Atlético/fisiologia , Treinamento Intervalado de Alta Intensidade/métodos , Traumatismos do Joelho/prevenção & controle , Futebol/lesões , Futebol/fisiologia , Adolescente , Traumatismos em Atletas/fisiopatologia , Humanos , Traumatismos do Joelho/fisiopatologia , Masculino , Resultado do Tratamento
4.
Nano Lett ; 15(2): 1171-6, 2015 Feb 11.
Artigo em Inglês | MEDLINE | ID: mdl-25615007

RESUMO

Control over nanoscale patterning of ultrathin molecular films plays an important role both in natural as well as artificial nanosystems. Here we report on nanophase separated patterns of water and ethanol within monomolecularly thin films confined between the cleavage plane of mica and single or a few layers of graphene. Employing scanning force microscopy of the graphene layers conforming to the molecular films we quantify the patterns using the ethanol-water cross correlation and the autocorrelation of domain wall directions. They reveal that lateral pattern dimensions grow and the domain walls stiffen upon increasing the thickness of the graphene multilayers. We attribute the control of the patterns through the graphene layers to the competition between the mechanical deformation energy of the graphene sheets and the electrostatic repulsion of dipoles normal to the interface. The latter results from charge transfer between graphene and the molecules confined between mica and graphene.

5.
Langmuir ; 30(12): 3455-9, 2014 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-24621444

RESUMO

The structure of multicomponent fluids in confined geometries is a key to understanding their properties. However, it remains an experimental challenge to gain molecular-scale resolution information on this structure. Here we show that mono- and multilayers of graphene, conforming to heterogeneous monolayers of molecules in a flexible slit pore between a mica surface and the graphene layers, allow for mapping the phase separation of water and ethanol within such a slit pore. Employing scanning force microscopy, we readily distinguish clusters of ethanol and water molecules due their different sizes, and we show that the phase separated water-ethanol structures become coarser under thicker graphenes. Moreover, we obtain a lower bound for the two-dimensional diffusion coefficient of ethanol in water of D ≥ 2 × 10(-14) m(2) s(-1). Thus, the molecularly thin slit pore provides a powerful tool to control and to investigate mixed fluids in self-adjusting nanopores.


Assuntos
Etanol/química , Termodinâmica , Água/química , Tamanho da Partícula , Propriedades de Superfície
6.
J Colloid Interface Sci ; 407: 500-4, 2013 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-23856061

RESUMO

Molecular adlayers on mica have been visualized previously by coating the sample with graphene and imaging it by scanning force microscopy. While it had been argued that this shows that ambient water on mica exhibits ice-like structures, recent apparently similar experiments indicate different behaviors. Here, we demonstrate that adhesive tapes, which are often used to mechanically exfoliate graphenes onto solid substrates, can lead to water-containing adlayers, which differ substantially from pure water layers. We exfoliated graphenes with the aid of different adhesive tapes and demonstrate that the results depend on the particular tape. Our results imply that structure and properties of confined water adlayers can be controlled by minor amounts of additives.

7.
Nat Chem ; 4(8): 655-62, 2012 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-22824898

RESUMO

Supramolecular assemblies that interact with light have recently garnered much interest as well-defined nanoscale materials for electronic excitation energy collection and transport. However, to control such complex systems it is essential to understand how their various parts interact and whether these interactions result in coherently shared excited states (excitons) or in diffusive energy transport between them. Here, we address this by studying a model system consisting of two concentric cylindrical dye aggregates in a light-harvesting nanotube. Through selective chemistry we are able to unambiguously determine the supramolecular origin of the observed excitonic transitions. These results required the development of a new theoretical model of the supramolecular structure of the assembly. Our results demonstrate that the two cylinders of the nanotube have distinct spectral responses and are best described as two separate, weakly coupled excitonic systems. Understanding such interactions is critical to the control of energy transfer on a molecular scale, a goal in various applications ranging from artificial photosynthesis to molecular electronics.

8.
Nano Lett ; 11(6): 2436-9, 2011 Jun 08.
Artigo em Inglês | MEDLINE | ID: mdl-21574589

RESUMO

The electronic properties of graphenes depend sensitively on their deformation, and therefore strain engineered graphene electronics is envisioned. In order to deform graphenes locally, we have mechanically exfoliated single and few layer graphenes onto atomically flat mica surfaces covered with isolated double stranded plasmid DNA rings. Using scanning force microscopy in both contact and intermittent contact modes, we find that the graphenes replicate the topography of the underlying DNA with high precision. The availability of macromolecules of different topologies, e.g., programmable DNA patterns, render this approach promising for new graphene based device designs. On the other hand, the encapsulation of single macromolecules offers new prospects for analytical scanning probe microscopy techniques.


Assuntos
DNA/química , Grafite/química , Silicatos de Alumínio/química , Substâncias Macromoleculares/química , Tamanho da Partícula , Plasmídeos , Propriedades de Superfície
9.
Phys Rev Lett ; 104(24): 246805, 2010 Jun 18.
Artigo em Inglês | MEDLINE | ID: mdl-20867325

RESUMO

The adsorption of the molecular acceptor hexaazatriphenylene-hexacarbonitrile on Ag(111) was investigated as function of layer density. We find that the orientation of the first molecular layer changes from a face-on to an edge-on conformation depending on layer density, facilitated through specific interactions of the peripheral molecular cyano groups with the metal. This is accompanied by a rehybridization of molecular and metal electronic states, which significantly modifies the interface and surface electronic properties, as rationalized by theoretical modeling.

10.
Science ; 325(5939): 456-60, 2009 Jul 24.
Artigo em Inglês | MEDLINE | ID: mdl-19628864

RESUMO

In the formation of chiral crystals, the tendency for twist in the orientation of neighboring molecules is incompatible with ordering into a lattice: Twist is expelled from planar layers at the expense of local strain. We report the ordered state of a neat material in which a local chiral structure is expressed as twisted layers, a state made possible by spatial limitation of layering to a periodic array of nanoscale filaments. Although made of achiral molecules, the layers in these filaments are twisted and rigorously homochiral--a broken symmetry. The precise structural definition achieved in filament self-assembly enables collective organization into arrays in which an additional broken symmetry--the appearance of macroscopic coherence of the filament twist--produces a liquid crystal phase of helically precessing layers.


Assuntos
Estrutura Molecular , Nanoestruturas , Cristalização , Microscopia de Força Atômica , Microscopia Eletrônica de Transmissão , Microscopia de Polarização , Difração de Raios X
11.
Nano Lett ; 9(1): 457-61, 2009 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-19143507

RESUMO

We demonstrate trench channeling of mono- and multilayer graphenes with silver nanoparticles with high speed in ambient environment and at elevated temperatures. A silver nanoparticle located at a graphene edge catalyzes oxidation of neighboring carbon atoms, thereby burning a trench into the graphene layer. High-resolution scanning tunneling microscopy imaging reveals that the trench edges are very smooth with a peak-to-peak roughness below 2 nm. We discuss the channeling mechanism and demonstrate that channeling speeds of up to 250 nm/s and the smoothness of the resulting trenches indicate the prospect of a "catalytic pen" for high-precision lithography on graphenes.


Assuntos
Cristalização/métodos , Grafite/química , Nanopartículas/química , Nanoestruturas/química , Nanoestruturas/ultraestrutura , Nanotecnologia/métodos , Prata/química , Catálise , Substâncias Macromoleculares/química , Teste de Materiais , Conformação Molecular , Tamanho da Partícula , Propriedades de Superfície
12.
Ultramicroscopy ; 109(1): 85-90, 2008 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-18947924

RESUMO

We investigated the scattering of current-voltage data obtained with scanning tunneling spectroscopy (STS) at room temperature at a solid-liquid interface on highly oriented pyrolytic graphite (HOPG) and in ultrahigh vacuum on HOPG and Au(111). For both experimental conditions, the data scattering can be described by a lognormal function for a moderate number of subsequent measurements. The lognormal distribution of the current can be explained by a normal distribution of the tip-surface distance. We give a simple empirical rule for STS data sorting.

13.
Phys Rev Lett ; 100(12): 126102, 2008 Mar 28.
Artigo em Inglês | MEDLINE | ID: mdl-18517888

RESUMO

Electron donor-acceptor molecular charge transfer complexes (CTCs) formed by alpha-sexithiophene (6T) and tetrafluoro-tetracyano-quinodimethane (F4TCNQ) on a Au(111) surface are investigated by scanning tunneling microscopy, spectroscopy, and spectroscopic imaging at 6 K. New hybrid molecular orbitals are formed in the CTCs, and the highest occupied molecular orbital of the CTC is mainly located on the electron accepting F4TCNQ while the lowest unoccupied molecular orbital is predominantly positioned on the electron donating 6T. We observed the conductance switching of F4TCNQ inside CTCs, which may find potential applications in novel molecular device operations.

14.
Langmuir ; 24(6): 2767-71, 2008 Mar 18.
Artigo em Inglês | MEDLINE | ID: mdl-18275233

RESUMO

We report on the self-assembly of several surfactant-encapsulated clusters (SECs) on the basal plane of graphite consisting of the doughnut-shaped tungstophosphate anion [Na(H2O)P5W30O110] covered by a hydrophobic shell of surfactants. Well-ordered rodlike structures are observed using scanning force microscopy. No such ordering is observed if the surfactant methyltrioctadecylammonium is used for encapsulation, suggesting that the density of alkyl chains around the polyoxometalate cluster is an important factor in determining the order of SEC assemblies on graphite. Coadsorption of tetratetracontane (n-C44H90) and (DODA)14[Na(H2O)P5W30O110] results in single, isolated SECs on a buffer layer of tetratetracontane, as determined by scanning tunneling microscopy.


Assuntos
Grafite/química , Compostos Organometálicos/química , Tensoativos/química , Tungstênio/química , Tamanho da Partícula , Propriedades de Superfície
15.
Langmuir ; 23(19): 9860-5, 2007 Sep 11.
Artigo em Inglês | MEDLINE | ID: mdl-17696454

RESUMO

The internal structure of porous TiO2 films prepared by electrostatic layer-by-layer deposition was investigated. The films were prepared by alternate dipping of solid substrates into dispersions of TiO2 nanoparticles and polycations, polyanions, or pure buffer solution, respectively. The surface charge of the amphoteric TiO2 particles was controlled by the pH of the aqueous dispersions. The morphology of the film surface was investigated by means of scanning electron microscopy. It was found that the surface roughness strongly depends on the polymeric material used for the deposition process but is independent of the ionic strength of the solution or the molecular weight of the polyions. The samples with rough surfaces feature strong light scattering. The porosity and internal structure of the TiO2/polyelectrolyte films were investigated by adsorption/desorption of dye molecules. A crude estimate yields an internal surface that is up to 160 times the plane surface of the substrate for a film thickness of 1 microm. The composition of the films was investigated by X-ray photoelectron spectroscopy (XPS). Detection of the XPS signal after each deposition step of the first three dipping cycles shows a significant increase of the relative surface coverage of Ti after the TiO2 deposition step and of PSS after the PSS deposition step. For later dipping cycles, such an increase was also detectable but less prominent.

16.
Nano Lett ; 6(11): 2561-6, 2006 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-17090091

RESUMO

We report here experimental observations which indicate that topologically or covalently formed polymer loops embedded in an ultrathin liquid film on a solid substrate can be "blown" into circular "bubbles" during scanning force microscopy (SFM) imaging. In particular, supercoiled vector DNA has been unraveled, moved, stretched, and overstretched to two times its B-form length and then torn apart. We attribute the blowing of the DNA bubbles to the interaction of the tapping SFM tip with the ultrathin liquid film.


Assuntos
DNA/química , Nanoestruturas/química , DNA/ultraestrutura , Membranas Artificiais , Microscopia de Força Atômica/métodos , Nanoestruturas/ultraestrutura , Tamanho da Partícula , Poliestirenos/química , Sensibilidade e Especificidade , Propriedades de Superfície
17.
Phys Rev Lett ; 96(15): 156803, 2006 Apr 21.
Artigo em Inglês | MEDLINE | ID: mdl-16712184

RESUMO

Evidence for temperature-dependent electron band dispersion in a pentacene thin film polymorph on graphite is provided by angle- and energy-dependent ultraviolet photoelectron spectroscopy. The bands derived from the highest occupied molecular orbital exhibit dispersion of approximately 190 meV at room temperature, and approximately 240 meV at 120 K. Intermolecular electronic coupling in pentacene thin films is thus confirmed to be dependent on temperature and possibly crystal structure, as suggested by additional infrared absorption measurements.

18.
Eur Phys J E Soft Matter ; 17(3): 339-43, 2005 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-15968478

RESUMO

We use ultraviolet photoelectron spectroscopy to investigate the effect of oxygen and air exposure on the electronic structure of pentacene single crystals and thin films. It is found that O(2) and water do not react noticeably with pentacene, whereas singlet oxygen/ozone readily oxidize the organic compound. Also, we obtain no evidence for considerable p-type doping of pentacene by O(2) at low pressure. However, oxygen exposure lowers the hole injection barrier at the interface between Au and pentacene by 0.25 eV, presumably due to a modification of the Au surface properties.


Assuntos
Eletroquímica/métodos , Nanoestruturas/química , Compostos Orgânicos/química , Oxigênio/química , Semicondutores , Espectrofotometria Ultravioleta , Teste de Materiais/métodos , Nanoestruturas/análise , Compostos Orgânicos/análise
19.
Eur Radiol ; 14(9): 1641-6, 2004 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-15232713

RESUMO

X-ray spectra are composed of a broad bremsspectrum and anode-characteristic emission lines. In mammography typically molybdenum (Mo), rhodium (Rh) or tungsten (W) anodes are used in combination with Mo, Rh or aluminium filters. Only the photons with energies between 17 and 22 keV of the resulting spectrum are suitable for the soft tissue imaging needed for mammography. The aim of this article is to present first results obtained with a monochromator module mounted at the exit of the X-ray tube of a conventional clinical mammography unit. The experimental setup consists of a Siemens Mammomat 300, an X-ray monochromator module and a linear array detector for image acquisition. The technique is similar to the slot-scan technique known from digital mammography. The experimental machine allows to obtain images both with polychromatic and monochromatic X-rays. Initial evaluation of the system was performed by examination of a contrast-detail phantom (CD-MAM-phantom, Nijmegen, The Netherlands). Images done with the new monochromatic technique were compared to images of the phantom done with polychromatic spectra, with film-screen mammography as well as with digital mammography. The new technique with monochromatic slot-scan mammography resulted in correct identification of 93% of the phantom. Digital slot-scan mammography with polychromatic beam resulted in correct identification of 87%, digital full-field mammography in 83% and conventional film-screen mammography in 70% of the phantom. The results suggest that monochromatization has a potential for improving image quality or decreasing dose in X-ray mammography.


Assuntos
Mamografia/instrumentação , Intensificação de Imagem Radiográfica/instrumentação , Desenho de Equipamento , Feminino , Humanos , Imagens de Fantasmas , Sensibilidade e Especificidade , Tecnologia Radiológica , Ecrans Intensificadores para Raios X
20.
Phys Rev Lett ; 92(18): 188303, 2004 May 07.
Artigo em Inglês | MEDLINE | ID: mdl-15169538

RESUMO

A prototypical single-molecule chemical-field-effect transistor is presented, in which the current through a hybrid-molecular diode is modified by nanometer-sized charge transfer complexes covalently linked to a molecule in an STM junction. The effect is attributed to an interface dipole which shifts the substrate work function by approximately 120 meV. It is induced by the complexes from electron acceptors covalently bound to the molecule in the gap and electron donors coming from the ambient fluid. This proof of principle is regarded as a major step towards monomolecular electronic devices.

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