Browsing by Author "Quinton, JS"

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    Characterisation of methane plasma treated carbon surfaces
    (Institute of Electrical and Electronics Engineers, 2008-02-25) Deslandes, A; Jasieniak, M; Ionescu, M; Shapter, JG; Quinton, JS
    Time of Flight Secondary ion Mass Spectrometry (ToF-SIMS) was used to investigate the chemical nature of methane plasma treated graphite surfaces. Principle Component Analysis (PCA) was applied to the SIMS data, revealing chemical changes to the surfaces, in particular the extent of hydrogenation. The hydrogen content of the HOPG surface is observed to increase with systematic increases in power of the plasma treatment. These results are supported by Elastic Recoil Detection Analysis (ERDA) measurements that show a similar increase in hydrogen content. Scanning Tunneling Microscopy (STM) measurements provide insight into the morphological changes to the surface caused by the treatment, via investigating plasma-created features that are observed to increase in coverage with the increases in plasma power. © 2008 IEEE.
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    Grazing incidence x-ray studies of ultra-thin lumogen films.
    (Elsevier, 2007-12-15) Keough, SJ; Hanley, TL; Wedding, AB; Quinton, JS
    Lumogen® Yellow S0790 films have been produced on silicon wafer substrates via physical vapour deposition (PVD) and spin-coating (SC) methods. These coatings were characterised with X-ray reflectometry (XRR) and grazing incidence X-ray diffraction (GIXD) techniques. The results show that ultra-thin (less than 12nm) PVD films coat amorphously, with crystallinity becoming increasingly apparent with increasing film thickness. In contrast, measurements of ultra-thin (less than 2nm) spin-coated films reveal a second, apparently stable crystalline structure. © 2007, Elsevier Ltd.
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    Hydrogenation of sp(2)-bonded carbon surfaces using methane plasma
    (Elsevier, 2010-01-01) Deslandes, A; Jasieniak, M; Ionescu, M; Shapter, JG; Quinton, JS
    Highly ordered pyrolytic graphite was exposed to radio-frequency methane plasma to produce a hydrogen-terminated carbon surface. The effects of treatment parameters, namely exposure time, applied power and methane pressure, upon the treated surfaces’ chemical and morphological properties were systematically investigated. Scanning tunnelling microscopy measurements showed growth features on the plasma treated surface, the coverage of which was shown to increase with plasma exposure time or applied plasma power and decrease with gas pressure. Analyses of post-treated surface structures (via static secondary ion mass spectrometry with the aid of principle component analysis) showed an increase in surface hydrogen with plasma exposure time, applied plasma power and decreasing gas pressure. The results of these analyses were further supported by elastic recoil detection analysis measurements, which showed similar trends for the experimental parameters on the resultant surface hydrogen content. © 2010, Elsevier Ltd.
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    ToF-SIMS characterisation of methane- and hydrogen-plasma-modified graphite using principal component analysis.
    (Wiley-Blackwell, 2009-03) Deslandes, A; Jasieniak, M; Ionescu, M; Shapter, JG; Fairman, C; Gooding, JJ; Hibbert, DB; Quinton, JS
    Time of flight secondary ion mass spectrometry (ToF-SIMS) has been used to determine the extent of surface modification of highly ordered pyrolytic graphite (HOPG) samples that were exposed to radio-frequency methane and hydrogen plasmas. The ToF-SIMS measurements were examined with the multivariate method of principal component analysis (PCA), to maximise the amount of spectral information retained in the analysis. This revealed that the plasma (methane or hydrogen plasma) modified HOPG exhibited greater hydrogen content than the pristine HOPG. The hydrogen content trends observed from the ToF-SIMS studies were also observed in elastic recoil detection analysis measurements. The application of the ToF-SIMS PCA method also showed that small hydrocarbon fragments were sputtered from the hydrogen-plasma-treated sample, characteristic of the formation of a plasma-damaged surface, whereas the methane-plasma-treated surface sputtered larger hydrocarbon fragments, which implies the growth of a polymer-like coating. Scanning tunnelling microscopy measurements of the modified surfaces showed surface features that are attributable to either etching or film growth after exposure to the hydrogen or methane plasma. © 2009, Wiley-Blackwell.
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    Vortex fluidic induced mass transfer across immiscible phases
    (Royal Society of Chemistry, 2022-01-31) Jellicoe, M; Igder, A; Chuah, C; Jones, DB; Luo, X; Stubbs, KA; Crawley, EM; Pye, SJ; Joseph, N; Vimalananthan, K; Gardner, Z; Harvey, DP; Chen, XJ; Salvemini, F; He, S; Zhang, W; Chalker, JM; Quinton, JS; Tang, YH; Raston, CL
    Mixing immiscible liquids typically requires the use of auxiliary substances including phase transfer catalysts, microgels, surfactants, complex polymers and nano-particles and/or micromixers. Centrifugally separated immiscible liquids of different densities in a 45° tilted rotating tube offer scope for avoiding their use. Micron to submicron size topological flow regimes in the thin films induce high inter-phase mass transfer depending on the nature of the two liquids. A hemispherical base tube creates a Coriolis force as a ‘spinning top’ (ST) topological fluid flow in the less dense liquid which penetrates the denser layer of liquid, delivering liquid from the upper layer through the lower layer to the surface of the tube with the thickness of the layers determined using neutron imaging. Similarly, double helical (DH) topological flow in the less dense liquid, arising from Faraday wave eddy currents twisted by Coriolis forces, impact through the less dense liquid onto the surface of the tube. The lateral dimensions of these topological flows have been determined using ‘molecular drilling’ impacting on a thin layer of polysulfone on the surface of the tube and self-assembly of nanoparticles at the interface of the two liquids. At high rotation speeds, DH flow also occurs in the denser layer, with a critical rotational speed reached resulting in rapid phase demixing of preformed emulsions of two immiscible liquids. ST flow is perturbed relative to double helical flow by changing the shape of the base of the tube while maintaining high mass transfer between phases as demonstrated by circumventing the need for phase transfer catalysts. The findings presented here have implications for overcoming mass transfer limitations at interfaces of liquids, and provide new methods for extractions and separation science, and avoiding the formation of emulsions. © 2022 The Author(s). Published by the Royal Society of Chemistry. Open Access CC BY.