National Center for Plasma Science and Technology

Dublin, Ireland

National Center for Plasma Science and Technology

Dublin, Ireland
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Flynn S.P.,Dublin City University | Flynn S.P.,National Center for Plasma Science and Technology | McKenna M.,Dublin City University | Monaghan R.,Dublin City University | And 5 more authors.
Journal of Chemical Education | Year: 2017

A visual demonstration showing the physical properties of hydrophobic and hydrophilic surfaces is described. This demonstration utilizes unique aqua-sheets that are fabricated using plasma enhanced chemical vapor deposition (PECVD) to give areas of high water contact angle (hydrophobic) and areas of low water contact angle (hydrophilic). The hidden pattern or message can be made visible by applying food dye-stained water to the sheets, resulting in aqua-art. © 2016 The American Chemical Society and Division of Chemical Education, Inc.


Vijayaraghavan R.K.,National Center for Plasma Science and Technology | McCoy A.P.,Dublin City University | Chauhan L.,Dublin City University | Chauhan L.,University of Petroleum and Energy Studies | And 5 more authors.
Journal of Physical Chemistry C | Year: 2014

p-type transparent conducting CuBr thin films were grown by thermal evaporation of CuBr followed by oxygen plasma treatment. Efficient incorporation of oxygen into the CuBr films was revealed, and the influence of plasma exposure on the electrical, structural, optical, and electronic properties of CuBr films was investigated. X-ray diffraction (XRD) analysis indicated the Zincblende structure of the oxygen plasma treated CuBr (OCB) films with the formation of nanocrystalline grains preferentially oriented along the (111) direction. p-type conducting OCB films show >85% average transmittance along with hole concentration, conductivity and Hall mobility values of ∼1019 cm-3, ∼1.5 S cm-1 and ∼0.45 cm2 V-1 s-1, respectively. The X-ray photoelectron spectra of the OCB films demonstrated that the plasma exposure resulted in a significant increase in the O 1s signal at the surface of OCB films. On the basis of the experimental results from the Hall measurements and X-ray photoemission, a possible explanation comprising the formation of a surface CuO layer is also proposed to elucidate the increase in the p-type conductivity of the OCB films. Strong room temperature emission of OCB films at around 416 nm was also observed, the intensity of which decreased with the increase of oxygen plasma exposure time. The results present oxygen plasma exposure as a simple and promising technique for the production of CuBr-based p-type materials for future transparent electronics. © 2014 American Chemical Society.


O'Connor N.,National Center for Plasma Science and Technology | O'Connor N.,Dublin City University | Cahill O.,National Center for Plasma Science and Technology | Daniels S.,National Center for Plasma Science and Technology | And 4 more authors.
Journal of Hospital Infection | Year: 2014

Healthcare-associated infections (HCAIs) affect ~4.5 million patients in Europe alone annually. With the ever-increasing number of 'multi-resistant' micro-organisms, alternative and more effective methods of environmental decontamination are being sought as an important component of infection prevention and control. One of these is the use of cold atmospheric pressure plasma (CAPP) systems with clinical applications in healthcare facilities. CAPPs have been shown to demonstrate antimicrobial, antifungal and antiviral properties and have been adopted for other uses in clinical medicine over the past decade. CAPPs vary in their physical and chemical nature depending on the plasma-generating mechanism (e.g. plasma jet, dielectric barrier discharge, etc.). CAPP systems produce a 'cocktail' of species including positive and negative ions, reactive atoms and molecules (e.g. atomic oxygen, ozone, superoxide and oxides of nitrogen), intense electric fields, and ultraviolet radiation (UV). The effects of these ions have been studied on micro-organisms, skin, blood, and DNA; thus, a range of possible applications of CAPPs has been identified, including surface decontamination, wound healing, biofilm removal, and even cancer therapy. Here we evaluate plasma devices, their applications, mode of action and their potential role specifically in combating HCAIs on clinical surfaces. © 2014 The Healthcare Infection Society.


PubMed | National Center for Plasma Science and Technology, Royal College of Surgeons in Ireland and Dublin City University
Type: Journal Article | Journal: The Journal of hospital infection | Year: 2014

Healthcare-associated infections (HCAIs) affect 4.5 million patients in Europe alone annually. With the ever-increasing number of multi-resistant micro-organisms, alternative and more effective methods of environmental decontamination are being sought as an important component of infection prevention and control. One of these is the use of cold atmospheric pressure plasma (CAPP) systems with clinical applications in healthcare facilities. CAPPs have been shown to demonstrate antimicrobial, antifungal and antiviral properties and have been adopted for other uses in clinical medicine over the past decade. CAPPs vary in their physical and chemical nature depending on the plasma-generating mechanism (e.g. plasma jet, dielectric barrier discharge, etc.). CAPP systems produce a cocktail of species including positive and negative ions, reactive atoms and molecules (e.g. atomic oxygen, ozone, superoxide and oxides of nitrogen), intense electric fields, and ultraviolet radiation (UV). The effects of these ions have been studied on micro-organisms, skin, blood, and DNA; thus, a range of possible applications of CAPPs has been identified, including surface decontamination, wound healing, biofilm removal, and even cancer therapy. Here we evaluate plasma devices, their applications, mode of action and their potential role specifically in combating HCAIs on clinical surfaces.


Kelleher S.M.,Dublin City University | Nooney R.I.,Dublin City University | Flynn S.P.,Dublin City University | Clancy E.,Dublin City University | And 8 more authors.
Nanotechnology | Year: 2015

This paper describes the fabrication of oligonucleotide-coated Cy5-doped silica nanoparticles using a combination of multivalent linkers and their use in surface-based DNA sandwich hybridization assays. Dipodal silane is introduced as a means to fabricate amine-coated silica nanoparticles and its advantages compared to monopodal silanes are discussed. The use of dipodal silane in conjunction with three different polymer linkers (oxidized dextran, linear and 8-arm polyethylene glycol (PEG)) to immobilize single-stranded DNA to Cy5-doped nanoparticles is investigated and dynamic light scattering measurements and Fourier transform infrared spectroscopy are used to follow the progression of the functionalization of the nanoparticles. We observe a significant improvement in the binding stability of the single-stranded DNA when the dipodal silane and 8-arm PEG are used in combination, when compared to alternative conjugation strategies. Both 8mer and 22mer oligonucleotides are securely conjugated to the high-brightness nanoparticles and their availability to hybridize with a complementary strand is confirmed using solution-based DNA hybridization experiments. In addition, a full surface-based sandwich assay demonstrates the potential these nanoparticles have in the detection of less than 500 femtomolar of a DNA analogue of micro RNA, miR-451. © 2015 IOP Publishing Ltd.


Yeates P.,National Center for Plasma Science and Technology | Costello J.T.,National Center for Plasma Science and Technology | Costello J.T.,Dublin City University | Kennedy E.T.,National Center for Plasma Science and Technology | Kennedy E.T.,Dublin City University
Review of Scientific Instruments | Year: 2010

Laser ion sources are used to generate and deliver highly charged ions of various masses and energies. We present details on the design and basic parameters of the DCU laser ion source (LIS). The theoretical aspects of a high voltage (HV) linear LIS are presented and the main issues surrounding laser-plasma formation, ion extraction and modeling of beam transport in relation to the operation of a LIS are detailed. A range of laser power densities (I∼ 108-1011 W cm-2) and fluences (F=0.1-3.9 kJ cm-2) from a Q-switched ruby laser (full-width half-maximum pulse duration ∼35 ns, λ=694 nm) were used to generate a copper plasma. In "basic operating mode," laser generated plasma ions are electrostatically accelerated using a dc HV bias (5-18 kV). A traditional einzel electrostatic lens system is utilized to transport and collimate the extracted ion beam for detection via a Faraday cup. Peak currents of up to I∼600 μA for Cu+ to Cu3+ ions were recorded. The maximum collected charge reached 94 pC (Cu2+). Hydrodynamic simulations and ion probe diagnostics were used to study the plasma plume within the extraction gap. The system measured performance and electrodynamic simulations indicated that the use of a short field-free (L=48 mm) region results in rapid expansion of the injected ion beam in the drift tube. This severely limits the efficiency of the electrostatic lens system and consequently the sources performance. Simulations of ion beam dynamics in a "continuous einzel array" were performed and experimentally verified to counter the strong space-charge force present in the ion beam which results from plasma extraction close to the target surface. Ion beam acceleration and injection thus occur at "high pressure." In "enhanced operating mode," peak currents of 3.26 mA (Cu2+) were recorded. The collected currents of more highly charged ions (Cu4+-Cu6+) increased considerably in this mode of operation. © 2010 American Institute of Physics.


Middleton D.P.W.,Dublin City University | Middleton D.P.W.,National Center for Plasma Science and Technology | Nikolopoulos L.A.A.,Dublin City University | Nikolopoulos L.A.A.,National Center for Plasma Science and Technology
Journal of Modern Optics | Year: 2012

In this work, single and double ionisation yields of neon under extreme ultraviolet free-electron laser (FEL) radiation tuned in the vicinity of the autoionising states (AIS) of Ne+ were studied. Density matrix equations were developed and were used to calculate the dependence of the branching ratios of singly and doubly ionised neon on the field intensity and its duration. In addition, in response to a recent experiment [M. Martins et al., Phys. Rev. A 2011, 80, 023411], a quantitative analysis was undertaken in order to reproduce the magnitude of the branching ratios by varying the FEL photon frequency in the range 41.0-42.0 eV in accordance with the experimental report. While the reported variations of the species' branching ratios as a function of the FEL field's photon energy were found, their magnitude and shape differ. In general, the branching ratios are found to be heavily dependent on the given combination of the peak intensity and the pulse duration. Furthermore, the FEL's stochastic fluctuation has been modelled by solving the average density matrix equations and it was found that stochastic effects should also affect branching ratios, mainly due to the increase in the effective bandwidth of the pulse in comparison with the AIS's decay ionisation width. Our calculations suggest that field fluctuations generally diminish the resonance features of the branching ratios. © 2012 Copyright Taylor and Francis Group, LLC.


Kavanagh P.J.,Dublin City University | Kavanagh P.J.,National Center for Plasma Science and Technology | Norci L.,Dublin City University | Norci L.,National Center for Plasma Science and Technology | And 2 more authors.
New Astronomy | Year: 2011

We present an analysis of the diffuse hard X-ray emission in the core of the young massive Galactic cluster Westerlund 1 based on a 48 ks XMM-Newton observation. Chandra results for the diffuse X-ray emission have indicated a soft thermal component together with a hard component that could be either thermal or non-thermal. We seek to resolve this ambiguity regarding the hard component exploiting the higher sensitivity of XMM-Newton to diffuse emission. Our new X-ray spectra from the central (2′ radius) diffuse emission are found to exhibit He-like Fe 6.7 keV line emission, demonstrating that the hard emission in the cluster core is predominantly thermal in origin. Potential sources of this hard component are reviewed, namely an unresolved Pre-Main Sequence population, a thermalized cluster wind and Supernova Remnants interacting with stellar winds. We find that the thermalized cluster wind likely contributes the majority of the hard emission with some contribution from the Pre-Main Sequence population. It is unlikely that Supernova Remnants are contributing significantly to the Westerlund 1 diffuse emission at the current epoch. © 2011 Elsevier B.V. All rights reserved.


McKenna M.,Dublin City University | Soberon F.,Dublin City University | Ricco A.J.,Dublin City University | Daniels S.,Dublin City University | And 2 more authors.
Sensors and Actuators, B: Chemical | Year: 2016

We compare immobilization methods for oligonucleotides on carboxylic acid surfaces with the goal of improving hybridization efficiency for single-stranded DNA (ssDNA) bioassays. When immobilized via 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC), ssDNA (either modified with a terminal amine or not) specifically binds to the surface; without EDC, binding is minimal. EDC-activated probes can, however, bind covalently to the surface through nucleobase as well as terminal amino groups. Unmatched base pairs from the former are detected via melting curve analysis: the target begins to unwind at ∼40 °C below the double-strand melting temperature of ∼64 °C. To eliminate such backbone binding, we immobilized azide-functionalized DNA via click chemistry, resulting in hybridization efficiencies 5 times higher than with EDC. This improvement, and the room-temperature hybridization of the click chemistry process, make it an important alternative to EDC for reliable DNA assays with maximum specificity and sensitivity. © 2016 Elsevier B.V. All rights reserved.


O Broin C.,Dublin City University | O Broin C.,National Center for Plasma Science and Technology | Nikolopoulos L.A.A.,Dublin City University | Nikolopoulos L.A.A.,National Center for Plasma Science and Technology
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2015

In this work we develop an approach for a molecular hydrogen ion (H2+) in the Born-Oppenheimer approximation while exposed to intense short-pulse radiation. Our starting point is the R-matrix-incorporating-time formulation for atomic hydrogen [L. A. A. Nikolopoulos, Phys. Rev. A 78, 063420 (2008)PLRAAN1050-294710.1103/PhysRevA.78.063420], which has proven to be successful at treating multielectron atomic systems efficiently and with a high accuracy [L. R. Moore, J. Mod. Opt. 58, 1132 (2011)JMOPEW0950-034010.1080/09500340.2011.559315]. The present study on H2+ is performed with the similar objective of developing an ab initio method for solving the time-dependent Schrödinger equation for multielectron diatomic molecules exposed to an external time-dependent potential field. The theoretical formulation is developed in detail for the molecular hydrogen ion where all the multielectron and internuclei complications are absent. As in the atomic case, the configuration space of the electron's coordinates is separated artificially over two regions: the inner (I) and outer (II) regions. In region I the time-dependent wave function is expanded on the eigenstate basis corresponding to the molecule's Hamiltonian augmented by Bloch operators, while in region II a grid representation is used. We demonstrate the independence of our results from the introduced artificial boundary surface by calculating observables that are directly accessed experimentally and also by showing that gauge-dependent quantities are also invariant with the region I box size. We also compare our results with other theoretical works and emphasize cases where basis-set approaches are currently very computationally expensive or intractable in terms of computational resources. © 2015 American Physical Society.

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