研究领域

Materials/Physical

The structures of many solids are only partially known. This arises because diffraction and spectroscopic methods produce only an average picture of the atomic arrangement, and require specimens composed of identical, repeating units if they are to yield the actual detail. For many materials this condition is not fulfilled: particularly important cases occur in defect oxides and heterogeneous catalysts, and indeed, any material where reactivity depends on inhomogeneity. My interest is in determining the real structure of such solids, via direct imaging of the atomic arrangement. For atoms other than those on exposed surfaces this requires high resolution electron microscopy (HREM). Metal atoms can be resolved using HREM, irrespective of whether the structure is periodic or not. The structural information from HREM at this level has opened up for study a whole range of solids which were hitherto intractable. Foremost among these are defect oxides with applications in high-Tc superconductivity and fast-ion conductors: with improved data from HREM, we can now start to relate physical properties to actual structure and associated variations in stoichiometry. Similar advances have been made in microcrystalline catalysts, where changes in co-ordination influencing reactivity, particularly in surface and sub-surface regions, can be monitored directly. Two examples of this, involving platinum metal on titanium dioxide and nanocrystalline gold, are shown below. It has been found that these 'nanoparticles' possess such a high ratio of surface to bulk atoms that their chemical properties can be drastically affected, and their behaviour is nothing like bulk materials. For example, nanocrystalline alumina, normally exceptionally inert, has an extremely reactive surface, and this is believed to play an important part in the catalytic activity of metals supported on this oxide.

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Cobalt sulphide microtube array as cathode in photoelectrochemical water splitting with photoanodes C-Y Lin, D Mersch, DA Jefferson, E Reisner – Chem. Sci. (2014) 5, 4906 (DOI: 10.1039/c4sc01811g) Shape-defined nanodimers by tailored heterometallic epitaxy CA García-Negrete, TC Rojas, BR Knappett, DA Jefferson, AE Wheatley, A Fernández – Nanoscale (2014) 6, 11090 (DOI: 10.1039/C4NR01815J) Systematic control of size and morphology in the synthesis of gold nanoparticles P Abdulkin, TL Precht, BR Knappett, HE Skelton, DA Jefferson, AEH Wheatley – Particle and Particle Systems Characterization (2014) 31, 571 (DOI: 10.1002/ppsc.201300227) Characterisation of Co@Fe3O4 core@shell nanoparticles using advanced electron microscopy. BR Knappett, P Abdulkin, E Ringe, DA Jefferson, S Lozano-Perez, TC Rojas, A Fernández, AE Wheatley – Nanoscale (2013) 5, 5765 (DOI: 10.1039/c3nr33789h) Dynamic nuclear polarization enhanced natural abundance 17O spectroscopy. F Blanc, L Sperrin, DA Jefferson, S Pawsey, M Rosay, CP Grey – Journal of the American Chemical Society (2013) 135, 2975 (DOI: 10.1021/ja4004377) A single-source route to bulk samples of C3N and the co-evolution of graphitic carbon microspheres TC King, PD Matthews, JP Holgado, DA Jefferson, RM Lambert, A Alavi, DS Wright – Carbon (2013) 64, 6 (DOI: 10.1016/j.carbon.2013.04.043) Can polymorphism be used to form branched metal nanostructures? AP LaGrow, S Cheong, J Watt, B Ingham, MF Toney, DA Jefferson, RD Tilley – Adv Mater (2013) 25, 1552 (DOI: 10.1002/adma.201204366) Systematic Control of Size and Morphology in the Synthesis of Gold Nanoparticles P Abdulkin, TL Precht, BR Knappett, HE Skelton, DA Jefferson, AEH Wheatley – Particle and Particle Systems Characterization (2014) 31, 571 (DOI: 10.1002/ppsc.201300227) New routes to Cu(i)/Cu nanocatalysts for the multicomponent click synthesis of 1,2,3-triazoles P Abdulkin, Y Moglie, BR Knappett, DA Jefferson, M Yus, F Alonso, AE Wheatley – Nanoscale (2013) 5, 342 (DOI: 10.1039/c2nr32570e) Synthesis, Alignment, and Magnetic Properties of Monodisperse Nickel Nanocubes AP LaGrow, B Ingham, S Cheong, GV Williams, C Dotzler, MF Toney, DA Jefferson, EC Corbos, PT Bishop, J Cookson, RD Tilley – Journal of the American Chemical Society (2012) 134, 855 (DOI: 10.1021/ja210209r) Nanoparticulate PdZn - Pathways towards the synthetic control of nanosurface properties V Engels, DA Jefferson, F Benaskar, PC Thüne, A Berenguer-Murcia, BF Johnson, AE Wheatley – Nanotechnology (2011) 22, 205701 (DOI: 10.1088/0957-4484/22/20/205701) Copper(0) in the Ullmann heterocycle-aryl ether synthesis of 4-phenoxypyridine using multimode microwave heating (vol 51, pg 248, 2010) F Benaskar, V Engels, N Patil, EV Rebrov, J Meuldijk, V Hessel, LA Hulshof, DA Jefferson, JC Schouten, AEH Wheatley – TETRAHEDRON LETT (2010) 51, 5849 (DOI: 10.1016/j.tetlet.2010.09.001) Nanoparticulate copper - routes towards oxidative stability V Engels, F Benaskar, DA Jefferson, BF Johnson, AE Wheatley – Dalton transactions (Cambridge, England : 2003) (2010) 39, 6496 (DOI: 10.1039/c0dt00134a) Cu-based nanoalloys in the base-free ullmann heterocyle-aryl ether synthesis V Engels, F Benaskar, N Patil, EV Rebrov, V Hessel, LA Hulshof, DA Jefferson, JAJM Vekemans, S Karwal, JC Schouten, AEH Wheatley – Organic Process Research and Development (2010) 14, 644 (DOI: 10.1021/op9003423) Erratum: Copper(0) in the ullmann heterocycle-aryl ether synthesis of 4-phenoxypyridine using multimode microwave heating (Tetrahedron Letters (2010) 51 (248)) F Benaskar, V Engels, N Patil, EV Rebrov, J Meuldijk, V Hessel, LA Hulshof, DA Jefferson, JC Schouten, AEH Wheatley – Tetrahedron Letters (2010) 51, 5849 (DOI: 10.1016/j.tetlet.2010.09.001) Evidence for heterogeneous Sonogashira coupling of phenylacetylene and iodobenzene catalyzed by well defined rhodium nanoparticles VK Kanuru, SM Humphrey, JM Kyffin, DA Jefferson, JW Burton, M Armbrüster, RM Lambert – Dalton transactions (Cambridge, England : 2003) (2009) 7602 (DOI: 10.1039/b912833f) Bimetallic PdZn Nanoparticles for the Partial Hydrogenation of Phenylacetylene V Engels, AEH Wheatley, A Berenguer-Murcia, DA Jefferson, BFG Johnson – Materials Science Forum (2009) 604-605, 13 (DOI: 10.4028/3-908453-09-7.13) Exploring the Structural Complexities of Metal-Metalloid Nanoparticles: The Case of Ni center dot B as Catalyst J Geng, DA Jefferson, BF Johnson – Chemistry (2009) 15, 1134 (DOI: 10.1002/chem.200801146) A study of magnetoplumbite-type (M-type) cobalt-titanium-substituted barium ferrite, BaCoxTixFe12-2xO19 (x = 1-6) GB Teh, N Saravanan, DA Jefferson – Materials Chemistry and Physics (2007) 105, 253 (DOI: 10.1016/j.matchemphys.2007.04.054) Enhancement of MTBE photocatalytic degradation by modification of TiO2 with gold nanoparticles A Orlov, DA Jefferson, M Tikhov, RM Lambert – Catalysis Communications (2007) 8, 821 (DOI: 10.1016/j.catcom.2006.08.040)