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Collins G.,University College Cork | Collins G.,Center for Research on Adaptive Nanostructures and Nanodevices | Schmidt M.,University College Cork | Schmidt M.,Center for Research on Adaptive Nanostructures and Nanodevices | And 5 more authors.
ACS Catalysis | Year: 2014

The structure-property relationship of palladium (Pd) catalysts in Suzuki-Miyaura cross-coupling reactions was investigated using Pd nanocrystals of uniform size and shape. Superior catalytic reactivity was observed for Pd nanoparticles with high-index {730} surface facets compared to low-index {100} facets. Although the nanocrystal morphologies were maintained during the reaction, the presence of Pd clusters, identified by high-resolution transmission electron microscopy (TEM), indicates a leaching mechanism. The nature of the surface facets on the nanoparticles was observed to influence the rate of Pd leaching during the Suzuki coupling reaction. The enhanced reactivity observed for the high-index facet catalysts stems from the greater number of leachable atoms of low abstraction energy available on high-index planes. © 2014 American Chemical Society.


Murphy F.A.,Queens Medical Research Institute | Poland C.A.,Queens Medical Research Institute | Poland C.A.,Institute of Occupational Medicine | Duffin R.,Queens Medical Research Institute | And 19 more authors.
American Journal of Pathology | Year: 2011

The fibrous shape of carbon nanotubes (CNTs) raises concern that they may pose an asbestos-like inhalation hazard, leading to the development of diseases, especially mesothelioma. Direct instillation of long and short CNTs into the pleural cavity, the site of mesothelioma development, produced asbestos-like length-dependent responses. The response to long CNTs and long asbestos was characterized by acute inflammation, leading to progressive fibrosis on the parietal pleura, where stomata of strictly defined size limit the egress of long, but not short, fibers. This was confirmed by demonstrating clearance of short, but not long, CNT and nickel nanowires and by visualizing the migration of short CNTs from the pleural space by single-photon emission computed tomographic imaging. Our data confirm the hypothesis that, although a proportion of all deposited particles passes through the pleura, the pathogenicity of long CNTs and other fibers arises as a result of length-dependent retention at the stomata on the parietal pleura. Copyright © 2011 American Society for Investigative Pathology.


Haas P.,Institute of Physics | Then P.,Physikalisches Institute | Wild A.,Institute of Physics | Grange W.,Institute Jacques Monod | And 6 more authors.
Analytical Chemistry | Year: 2010

The applicability of single-molecule fluorescence assays in liquids is limited by diffusion to concentrations in the low picomolar range. Here, we demonstrate quantitative single-molecule detection at attomolar concentrations within 1 min by excitation and detection of fluorescence through a single-mode optical fiber in presence of turbulent flow. The combination of high detectability and short measurement times promises applications in ultrasensitive assays, sensors, and point-of-care medical diagnostics. © 2010 American Chemical Society.


Keeley G.P.,Center for Research on Adaptive Nanostructures and Nanodevices | Keeley G.P.,Trinity College Dublin | O'Neill A.,Center for Research on Adaptive Nanostructures and Nanodevices | O'Neill A.,Trinity College Dublin | And 8 more authors.
Journal of Materials Chemistry | Year: 2010

This paper describes the electron transfer properties of graphene nano-sheets (GNSs) immobilised on pyrolysed photoresist film (PPF) electrodes. The former are produced by the dispersion and exfoliation of graphite in dimethylformamide, and they are characterised using transmission electron microscopy, scanning electron microscopy and Raman spectroscopy. Cyclic voltammetry and electrochemical impedance spectroscopy are used to quantify the effect of the GNSs on electrochemical surface area and on electron transfer kinetics. Compelling evidence is reported in relation to the importance of edge-plane sites and defects in the promotion of electron transfer at carbon nanostructures. A novel ascorbic acid (vitamin C) sensor is presented based on the PPF/GNS system, which is effective in the range 0.4 to 6.0 mM, with a 0.12 mM detection limit. The selectivity of the sensor is demonstrated using a commercially available vitamin C supplement. This is the first report of the electrochemical properties of graphene nano-sheets produced using liquid-phase exfoliation, and it will serve as an important benchmark in the development of inexpensive graphene-based electrodes with high surface area and electro-catalytic activity. © 2010 The Royal Society of Chemistry.


O'Regan C.,Tyndall National Institute | O'Regan C.,Center for Research on Adaptive Nanostructures and Nanodevices | Biswas S.,Tyndall National Institute | Biswas S.,Center for Research on Adaptive Nanostructures and Nanodevices | And 10 more authors.
Chemistry of Materials | Year: 2013

The synthesis of Ge nanowires with very high-aspect ratios (greater than 1000) and uniform crystal growth directions is highly desirable, not only for investigating the fundamental properties of nanoscale materials but also for fabricating integrated functional nanodevices. In this article, we present a unique approach for manipulating the supersaturation, and thus the growth kinetics, of Ge nanowires using Au/Ge bilayer films. Ge nanowires were synthesized on substrates consisting of two parts: a Au film on one-half of a Si substrate and a Au/Ge bilayer film on the other half of the substrate. Upon annealing the substrate, Au and Au/Ge binary alloy catalysts were formed on both the Au and Au/Ge-sides of the substrates, respectively, under identical conditions. The mean lengths of Ge nanowires produced were found to be significantly longer on the Au/Ge bilayer side of the substrate compared to the Au-coated side, as a result of a reduced incubation time for nucleation on the bilayer side. The mean length and growth rate on the bilayer side (with a 1 nm Ge film) was found to be 5.5 ± 2.3 μm and 3.7 × 10-3 μm s-1, respectively, and 2.7 ± 0.8 μm and 1.8 × 10-3 μm s-1 for the Au film. Additionally, the lengths and growth rates of the nanowires further increased as the thickness of the Ge layer in the Au/Ge bilayer was increased. In-situ TEM experiments were performed to probe the kinetics of Ge nanowire growth from the Au/Ge bilayer substrates. Diffraction contrast during in situ heating of the bilayer films clarified the fact that thinner Ge films, that is, lower Ge concentration, take longer to alloy with Au than thicker films. Phase separation was also more significant for thicker Ge films upon cooling. The use of binary alloy catalyst particles, instead of the more commonly used elementary metal catalyst, enabled the supersaturation of Ge during nanowire growth to be readily tailored, offering a unique approach to producing very long high aspect ratio nanowires. © 2013 American Chemical Society.


Keeley G.P.,CNRS Molecular Chemistry Department | Keeley G.P.,Center for Research on Adaptive Nanostructures and Nanodevices | Keeley G.P.,Trinity College Dublin | O'Neill A.,Center for Research on Adaptive Nanostructures and Nanodevices | And 7 more authors.
Physical Chemistry Chemical Physics | Year: 2011

The electrochemical detection of NADH is of considerable interest because it is required as a cofactor in a large number of dehydrogenase-based biosensors. However, the presence of oxygenated functionalities on the electrode often causes fouling due to the adsorption of the oxidised form, NAD +. Here we report an electroanalytical NADH sensor based on DMF-exfoliated graphene. The latter is shown to have a very low oxygen content, facilitating the exceptionally stable and sensitive detection of this important analyte. © 2011 the Owner Societies.


Kumar S.,Center for Research on Adaptive Nanostructures and Nanodevices | Kumar S.,Trinity College Dublin | Rezvani E.,Center for Research on Adaptive Nanostructures and Nanodevices | Rezvani E.,Trinity College Dublin | And 3 more authors.
Nanotechnology | Year: 2012

We present a graphene resist interlacing process (GRIP) to sandwich graphene between polymer lines in a cloth-like fashion, making it more accessible for experiments and applications. We demonstrate the handling of large-area graphene in this way. Here, GRIP is used to fabricate supports for transmission electron microscopy. These supports improve the imaging quality of nanoparticles, as we show by comparison to imaging on standard lacey carbon supports. © 2012 IOP Publishing Ltd.


Collins G.,Tyndall National Institute | Collins G.,Center for Research on Adaptive Nanostructures and Nanodevices | Fleming P.,Tyndall National Institute | Fleming P.,Center for Research on Adaptive Nanostructures and Nanodevices | And 9 more authors.
Chemistry of Materials | Year: 2010

The ambient stability and surface coverage of halogen (Cl, Br, and I) passivated germanium nanowires were investigated by X-ray photoelectron and X-ray photoelectron emission spectroscopy. After exposure to air for 24 h, the stability of the halogen-terminated Ge nanowire surfaces toward reoxidation was found to improve with the increasing size of the halogen atoms, i.e., I>Br>Cl. Halogen termination was effective in removing the native Ge oxide (GeOx) and could also be utilized for further functionalization. Functionalization of the halogenated Ge nanowires was investigated using alkyl Grignard reagents and alkanethiols. The stability of the alkyl and alkanethiol passivation layers from the different halogen-terminated surfaces was investigated by X-ray photoelectron spectroscopy and attenuated total reflectance infrared spectroscopy. Alkanethiol functionalized nanowires showed greater resistance against reoxidation of the Ge surface compared to alkyl functionalization when exposed to ambient conditions for 1 week. ©2010 American Chemical Society.


Verre R.,Center for Research on Adaptive Nanostructures and Nanodevices | Fleischer K.,Center for Research on Adaptive Nanostructures and Nanodevices | Smith C.,Center for Research on Adaptive Nanostructures and Nanodevices | McAlinden N.,Center for Research on Adaptive Nanostructures and Nanodevices | And 2 more authors.
Physical Review B - Condensed Matter and Materials Physics | Year: 2011

A simplified approach to investigate the out-of-plane response of plasmonic nanostructures using spectroscopic ellipsometry (SE) is presented. One-dimensional self-assembled arrays of Ag nanoparticles (NP's) were grown on stepped Al2O3(0001), in ultrahigh vacuum, using deposition at a glancing angle. The SE response was measured with the plane of incidence aligned along, and across, the surface steps. From the raw data, an anisotropic surface excess function (ASEF) can be extracted, whose properties depend only on the dielectric function of the NP layer. Three resonances are clearly seen in the ASEF: two in-plane resonances, which correspond to the resonances measured using normal incidence reflection anisotropy spectroscopy, and the out-of-plane resonance. A dipole model is used to simulate the optical response of the NP layer, where the presence of the out-of-plane resonance provides an important additional constraint in developing the model. © 2011 American Physical Society.


Verre R.,Center for Research on Adaptive Nanostructures and Nanodevices | Fleischer K.,Center for Research on Adaptive Nanostructures and Nanodevices | Sofin R.G.S.,Center for Research on Adaptive Nanostructures and Nanodevices | McAlinden N.,Center for Research on Adaptive Nanostructures and Nanodevices | And 2 more authors.
Physical Review B - Condensed Matter and Materials Physics | Year: 2011

One-dimensional Ag nanoparticle arrays have been grown on step-bunched vicinal Al2O3 in ultrahigh vacuum using deposition at a glancing angle. The structures grown showed a strong optical anisotropy in the visible region of the spectrum. The optical anisotropy was measured in situ using reflection anisotropy spectroscopy. Relevant optical properties were determined as a function of deposition angle and Ag thickness. A simple phenomenological model was developed to reproduce the features seen in the spectra. With this model it was possible to use the inhomogeneous broadening as a guide to the nanoparticle dispersion. © 2011 American Physical Society.

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