Publikationen


Suche nach „[M.] [Kelly]“ hat 10 Publikationen gefunden
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    Zeitschriftenartikel

    T. Blaschke, G. Hay, M. Kelly, S. Lang, Peter Hofmann, E. Addink, R. Queiroz Feitosa, van der Meer, F., van der Werff, H., F. van Coillie, D. Tiede

    Geographic Object-Based Image Analysis – Towards a new paradigm

    ISPRS Journal of Photogrammetry & Remote Sensing, vol. 87, no. 1, pp. 180-191

    2014

    Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen

    Vortrag

    M.-O. M. Piepenbrock, M. O’Neill, Thomas Stirner, S. Kelly

    Growth dynamics of CdTe quantum dot ensembles in liquid and crystalline phases

    SPIE Optics and Photonics /Nanoscience and Engineering, San Diego, CA, USA

    2008

    Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen

    Zeitschriftenartikel

    M.-O. M. Piepenbrock, Thomas Stirner, M. O’Neill, S. Kelly

    Dynamics of the size distribution of CdTe quantum dot ensembles during growth in liquid and crystalline phases

    Physical Chemistry Chemical Physics (PCCP), vol. 9, no. 7, pp. 1057-1061

    2008

    Abstract anzeigen

    We recently reported that the growth rate of colloidal CdTe nanoparticles decreases by orders of magnitude when the particles undergo a phase transition from liquid to crystal. The dynamics of nanoparticle growth are dominated by this factor rather than the size dependence of the chemical potential. Herein we discuss how the phase transition affects the size distribution and photoluminescence quantum efficiency of the nanoparticles. We suggest that the absorption linewidth is a better monitor of size distribution than the photoluminescence linewidth because the photoluminescence quantum efficiency, which affects the latter via energy transfer, varies substantially with reaction time. We find that the size distribution broadens in the early stages of growth possibly because of inhomogeneities in the phase transition radius or because particles nucleated at later times coalesce with nanocrystals. The quantum efficiency is enhanced when tellurium is depleted in the reaction solution, giving a cadmium-enriched surface. Batches with high initial tellurium and cadmium concentrations show a substantial amount of delayed nucleation, lower quantum efficiency and some anisotropic growth.

    Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen

    Zeitschriftenartikel

    M. Carrasco-Or, D. Dong, R. Kelly, C. Ellis, M. O’Neill, Thomas Stirner, M.-O. M. Piepenbrock

    Superlattices of organic/inorganic semiconductor nanostructures from liquid-crystal templates

    Physical Review B - condensed matter and materials physics, vol. 75

    2007

    DOI: 10.1103/PhysRevB.75.035207

    Abstract anzeigen

    A lyotropic liquid-crystal-templated superlattice of inorganic CdSe semiconductor nanostructures within an organic semiconductor polymer-network film was fabricated by a self-assembly process. The film is characterized with small-angle x-ray diffraction experiments and ultraviolet-visible absorption measurements. Empirical pseudopotential calculations of the effective CdSe nanocrystal band gap show that the experimental observations are consistent with the formation of CdSe nanostructures inside lyotropic liquid-crystal nanotubes. A potential application of these nanocomposite supramolecular arrays is demonstrated via a photoconductive device.

    Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen

    Zeitschriftenartikel

    M.-O. M. Piepenbrock, Thomas Stirner, M. O’Neill, S. Kelly

    Growth dynamics of CdTe nanoparticles in liquid and crystalline phases

    Journal of the American Chemical Society (JACS), vol. 129, no. 24, pp. 7674-7679

    2007

    Abstract anzeigen

    Normally the size dependence of the chemical potential is used to explain the growth dynamics of semiconductor nanoparticles. Instead we show that very small CdTe nanoparticles continue to grow at high dilution, the growth rate is virtually independent of monomer concentration, nucleation continues after the growth of larger particles has saturated, and the growth rate has a much greater nonlinear dependence on particle size than predicted by theory. We suggest that nanoparticle growth is fast in the liquid phase and then saturates as the particles change phase from liquid to crystal at a threshold size which depends on the growth temperature and not the monomer concentration. The photoluminescence quantum efficiency becomes high when tellurium is depleted in the reaction solution giving a cadmium enriched surface.

    Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen

    Zeitschriftenartikel

    A. Löbbert, S. Kitney, M. O’Neill, S. Kelly, Thomas Stirner

    Terminal end-group efficiency for the nematic phase using model bicyclo[2.2.2]octanes

    Liquid Crystals, vol. 34, no. 12, pp. 1357-1367

    2007

    Abstract anzeigen

    The synthesis is reported of new liquid crystals incorporating the 1,4-disubstituted bicyclo[2.2.2] octane ring and a series of substituents in a terminal position on the molecular core. The nature of the terminal substituent is varied from apolar with a small dipole moment to polar with a strong dipole moment. The angle of the dipole moment with respect to the molecular axis is also varied. An updated order of terminal group efficiency for substituents in a terminal position for the nematic phase is provided. The bicyclo[2.2.2] octane ring shields halogen substituents in a lateral position on phenyl rings attached to the bicyclooctane ring to a small degree and reduces the steric efects of these substituents, giving rise to high relative nematic - isotropic transition temperatures.

    Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen

    Zeitschriftenartikel

    G. Bergmann, P. Jackson, J.H.C. Hogg, Thomas Stirner, M. O’Neill, W. Duffy, S. Kelly, G. Clark

    Photoinduced changes of surface order in coumarin side-chain polymer films used for liquid crystal photoalignment

    Applied Physics Letters, vol. 87

    2005

    DOI: 10.1063/1.2009070

    Abstract anzeigen

    Specular x-rayreflectivity probes morphological changes in a crosslinkable coumarin photoalignment polymer film resulting from ultraviolet irradiation. An ordered surface layer with density oscillations compatible with planar side-chain alignment is obtained before irradiation. The ordering is enhanced in the early stages of crosslinking. This is attributed to the photoinduced increase of mobility of the side-chains resulting from the creation of free volume by the crosslinking process. The expansion of the thin film confirms that free volume is created. The surface ordering decreases with prolonged ultraviolet irradiation because of increased material viscosity resulting from a high crosslinked density. The implications of surface ordering on liquid crystal photoalignment are discussed.

    Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen

    Beitrag (Sammelband oder Tagungsband)

    S. Kelly, Thomas Stirner, M. O’Neill

    Cadmium chalcogenide nanocrystals

    Chapter 4

    The handbook of electroluminescent materials, Bristol, UK; Philadelphia, PA

    2004

    ISBN: 978-0750309233

    Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen

    Vortrag

    G. Bergmann, P. Jackson, J.H.C. Hogg, Thomas Stirner, W. Duffy, S. Kelly, G. Clark, M. O’Neill

    In-situ study of the ultraviolet irradiation of side-chain coumarin polymers using specular x-ray reflectivity

    Synchrotron Radiation in Polymer Science II Conference, Sheffield, Großbritannien

    2002

    Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen

    Zeitschriftenartikel

    Thomas Stirner, N. Kirkman, L. May, C. Ellis, J. Nicholls, S. Kelly, M. O’Neill, J.H.C. Hogg

    CdTe nanocrystals: synthesis, optical characterisation and pseudopotential calculation of the bandgap

    Journal of Nanoscience and Nanotechnology, vol. 1, no. 4, pp. 451-455

    2001

    DOI: 10.1166/jnn.2001.053

    Abstract anzeigen

    CdTe nanocrystals were synthesized in aqueous solution using 1-thioglycerol and 2-mercaptoethanol as surface stabilizers. The nanocrystals were characterized by means of X-ray powder diffraction and UV-vis absorption measurements. The UV-vis absorption spectra exhibit two distinct transition lines. Comparison of the experimental measurements with the results of the empirical pseudopotential calculations of the CdTe nanocrystals showed that the lower energy absorption line can be assigned to the heavy-hole exciton transition, whereas the higher energy absorption line can be attributed to the light-hole exciton transition.