Simon R. Hall

Fast and scalable synthesis of strontium niobates with controlled stoichiometry

Co-reporter:Omar Gómez Rojas;Ge Song

CrystEngComm (1999-Present) 2017 vol. 19(Issue 36) pp:5351-5355

Publication Date(Web):2017/09/18

DOI:10.1039/C7CE01298E

Recently a new method for the synthesis of metal oxides has been reported, using ionic liquids as an effective metal cation solvent and chelating agent. Here we discuss the mechanism of action of this technique and demonstrate its efficacy as a means to synthesise phase-pure strontium niobates of controlled stoichiometry.

On the synergistic interaction of an ionic liquid and biopolymers in the synthesis of strontium niobate

Co-reporter:Omar Gómez Rojas, Simon R. Hall

Materials Chemistry and Physics 2017 Volume 202(Volume 202) pp:

Publication Date(Web):1 December 2017

DOI:10.1016/j.matchemphys.2017.09.024

•A synthesis of strontium niobate using ionic liquids containing biopolymers is proposed.•The solutions are capable of forming totally homogeneous multicationic systems.•Shape, size and crystallinity of strontium niobates are able to be finely controlled.The wide range of interesting properties that metal oxides exhibit has always driven creative research in this area. Here we analyse the interaction between an ionic liquid, 1-Ethyl-3-methylimidazolium acetate (emim)OAc, and biopolymers such as cellulose, chitosan, starch and dextran and demonstrate how they are intimately involved in the control of shape, size and crystallinity of strontium niobate.

Polymorphism in crystals of bis(4-bromophenyl)fumaronitrile through vapour phase growth

Co-reporter:Torsten T. Jensen;Jason Potticary;Lui R. Terry;Hannah E. Bruce Macdonald;Jan Gerit Brandenburg

CrystEngComm (1999-Present) 2017 vol. 19(Issue 48) pp:7223-7228

Publication Date(Web):2017/12/12

DOI:10.1039/C7CE01543G

Polymorphic selectivity within crystals grown via physical vapour transport (PVT) is dependent on the thermodynamic stabilities of differing molecular conformations and the kinetic regime within the growth apparatus. Crystals of bis(4-bromophenyl)fumaronitrile have been grown for the first time via this method, with the formation of both the conventional polymorph and a new, unforseen polymorph. Analysis suggests that the conventional form is less thermodynamically stable, with this form crystallising at higher temperature than the newly discovered form due to the release of binding energy of intermolecular interactions during the growth process. Fluorometry reveals the new form to exhibit weaker, red-shifted fluorescence emission owing to greater intermolecular π–π overlap.

On the Mechanism of Cuprate Crystal Growth: The Role of Mixed Metal Carbonates

Co-reporter:David C. Green;Rebecca Boston;Stefan Glatzel;Martin R. Lees;Stuart C. Wimbush;Jason Potticary;Wataru Ogasawara

Advanced Functional Materials 2015 Volume 25( Issue 29) pp:4700-4707

Publication Date(Web):

DOI:10.1002/adfm.201501058

The mechanism of formation of the superconductor Bi₂Sr₂CaCu₂O_8+x (Bi-2212) has been an open question since its discovery in 1988. By controlling crystal growth through the use of biopolymers as multivalent cation chelating agents, it is demonstrated through X-ray diffraction and thermogravimetric analysis, that it is the formation of a mixed metal carbonate eutectic that promotes the formation of the target phase. X-ray diffraction experiments, supported by infrared spectroscopy, identify this phase as (Sr_1−xCa _x )CO₃. This knowledge allows to further reduce the eutectic melting point by the incorporation of a biopolymer rich in potassium ions, resulting in the scalable formation of Bi-2212 at a temperature 50 °C lower than has been achieved previously.

Graphene oxide as a template for a complex functional oxide

Co-reporter:R. Boston, A. Bell, V. P. Ting, A. T. Rhead, T. Nakayama, C. F. J. Faul and S. R. Hall

CrystEngComm 2015 vol. 17(Issue 32) pp:6094-6097

Publication Date(Web):05 Jun 2015

DOI:10.1039/C5CE00922G

We report the first use of graphene oxide (GO) as a sacrificial template for the structural direction of complex oxides. The superconductor yttrium barium copper oxide (YBCO) was used as a quarternary oxide test system, with the GO templates being used to create foams and layered paper-like structures which retained the superconducting properties of YBCO.

Formation of superconducting yttrium barium copper oxide using sulphur-containing templates

Co-reporter:R. Boston, K. Awaya, T. Nakayama, W. Ogasawara and S. R. Hall

RSC Advances 2014 vol. 4(Issue 51) pp:26824-26828

Publication Date(Web):06 Jun 2014

DOI:10.1039/C4RA04745A

The formation of yttrium barium copper oxide (YBCO) via biotemplated routes is often plagued by unwanted stable intermediates, some of which arise from the template itself. Here we describe a method which allows sulphur-containing templates, such as proteins, to form superconducting YBCO which would have hitherto resulted in non-superconducting sulphated phases.

In Situ TEM Observation of a Microcrucible Mechanism of Nanowire Growth

Co-reporter:Rebecca Boston;Zoe Schnepp;Yoshihiro Nemoto;Yoshio Sakka

Science 2014 Vol 344(6184) pp:623-626

Publication Date(Web):09 May 2014

DOI:10.1126/science.1251594

Nanowire Growth Observed

In the hypothetical microcrucible growth mechanism for nanowires, a molten catalytic particle located in a pore on a substrate continually feeds the outward growth of the wire. To observe such a mechanism requires the ability to examine nanowire growth in situ. Boston et al. (p. 623) studied various stages of Y₂BaCuO₅ nanowire growth using transmission electron microscopy and were able to observe a microcrucible growth mechanism directly.

Synthesis of phase pure praseodymium barium copper iron oxide

Co-reporter:Joshua L. Konne, Sean A. Davis, Stefan Glatzel and Simon R. Hall

Chemical Communications 2013 vol. 49(Issue 48) pp:5477-5479

Publication Date(Web):03 May 2013

DOI:10.1039/C3CC42462F

The control of crystallization of praseodymium barium copper iron oxide, an intermediate temperature solid oxide fuel cell cathode material, has been demonstrated for the first time using a biotemplated sol–gel synthesis technique. The results obtained showed significant improvement in purity, synthesis time, surface area and simplicity over that previously reported.

Designed 3D architectures of high-temperature superconductors

Co-reporter:David C. Green, Martin R. Lees and Simon R. Hall

Chemical Communications 2013 vol. 49(Issue 29) pp:2974-2976

Publication Date(Web):31 Jan 2013

DOI:10.1039/C3CC38271K

Self-supporting superconducting replicas of pasta shapes are reported, yielding products of differing 3D architectures. Functioning high-temperature superconductor wires are developed and refined from replicas of spaghetti, demonstrating a unique sol–gel processing technique for the design and synthesis of novel macroscopic morphologies of complex functional materials.

Synthesis of spherical superconductors

Co-reporter:Rebecca Boston, Antony Carrington, Dominic Walsh and Simon R. Hall

CrystEngComm 2013 vol. 15(Issue 19) pp:3763-3766

Publication Date(Web):19 Mar 2013

DOI:10.1039/C3CE40269J

The cuprate superconductor YBa2Cu3O7−δ (Y123) has been synthesised for the first time in a spherical morphology. The use of carboxymethyl-dextran in a pre-formed, spherical morphology enables not only the engineering of this new macromorphological motif, but also crystallochemical control of the superconductor at the nano-scale.

Biotemplated synthesis of catalytic Au–Pd nanoparticles

Co-reporter:Simon R. Hall, Andrew M. Collins, Natalie J. Wood, Wataru Ogasawara, Moataz Morad, Peter J. Miedziak, Meenakshisundaram Sankar, David W. Knight and Graham J. Hutchings

RSC Advances 2012 vol. 2(Issue 6) pp:2217-2220

Publication Date(Web):22 Dec 2011

DOI:10.1039/C2RA01336C

In this paper, we demonstrate a facile route to carbon-supported nanoparticles of a gold/palladium alloy which exhibit catalytic activity for the oxidation of benzylic alcohols, using the biopolymer chitosan. The biomolecule acts triply as a structure-directing agent, anti-sintering matrix and in situ source of carbon in which the catalytically active nanoparticles are dispersed. The catalyst works without the need for environmentally harmful bases and solvents.

Biotemplated synthesis of superconducting plate-like YBa2Cu3O7−δ using oligosaccharides

Co-reporter:Simon R. Hall, Stuart C. Wimbush, Yosuke Shida, Wataru Ogasawara

Chemical Physics Letters 2011 Volume 507(1–3) pp:144-150

Publication Date(Web):29 April 2011

DOI:10.1016/j.cplett.2011.03.071

Abstract

Crystallization of the high temperature superconductor YBa₂Cu₃O_7−δ (Y123) in a plate-like morphology has been achieved through the use of the short-chained oligosaccharides. This is the first time that biotemplates with such a high degree of monodispersity have been used to synthesize superconducting oxides, with control over crystallization being effected through a single molecular species. We find that for all the oligosaccharides used, there is an increasing prevalence of thin, plate-like crystals as the oligosaccharide chain length increases. SQUID magnetometry revealed that there was an increase in critical current density (J_c) concomitant with an increase in the plateyness of the crystallites.

Formation of cobalt-Prussian Blue nanoparticles in a biopolymer matrix

Co-reporter:Andrew M. Collins, Stephen Mann and Simon R. Hall

Nanoscale 2010 vol. 2(Issue 11) pp:2370-2372

Publication Date(Web):28 Sep 2010

DOI:10.1039/C0NR00382D

The molecular magnet material, cobalt-Prussian Blue, has been synthesized using chitosan as a morphological structure-directing agent. The strong chelating ability of the biopolymer ensures that the inorganic phase remains nanoparticulate. SQUID magnetometry reveals that the nanoparticles exhibit a sharp ferrimagnetic to paramagnetic transition at 16 K.

Biopolymer-mediated synthesis of anisotropic piezoelectric nanorods

Co-reporter:Zoe Schnepp, John Mitchells, Stephen Mann and Simon R. Hall

Chemical Communications 2010 vol. 46(Issue 27) pp:4887-4889

Publication Date(Web):14 Jun 2010

DOI:10.1039/C0CC00516A

Alginate biopolymer was used to control the crystal growth of the lead-free piezoelectric material langasite. The piezo-response of these nanorods was demonstrated to be equivalent to that of ZnO. This is the first time that templated growth of langasite and its associate phases has been demonstrated.

Alginate-mediated routes to the selective synthesis of complex metal oxide nanostructures

Co-reporter:Zoe Schnepp, Stuart C. Wimbush, Stephen Mann and Simon R. Hall

CrystEngComm 2010 vol. 12(Issue 5) pp:1410-1415

Publication Date(Web):25 Jan 2010

DOI:10.1039/B923543B

The exceptional electronic, magnetic, optical and catalytic properties demonstrated by many ceramic materials when confined to the nanoscale are well established. However, the synthesis of multicomponent metal oxide nanowires and nanoparticles is notoriously problematic due to the difficulty of controlling homogeneity and achieving the correct stoichiometry. In this paper, we demonstrate a selective route to nanowires or nanoparticles of a quaternary metal oxide product using sodium or ammonium alginate respectively. By pre-organizing metal cations within an alginate gel the nucleation and growth of precursor crystalline phases can be constrained to the nanoscale. On further calcination the alginate decomposition products prevent sintering of these precursor nanoparticles prior to conversion to the final product. The cooperative effect of polymer microstructure and decomposition products allows an exceptional level of control over nucleation, growth and transport of the intermediate phases and subsequently on the particle size and morphology of the final product.

A novel route for the synthesis of nanocomposite tungsten carbide–cobalt using a biopolymer as a carbon source

Co-reporter:Michael W. R. Holgate;Thomas Schoberl

Journal of Sol-Gel Science and Technology 2009 Volume 49( Issue 2) pp:

Publication Date(Web):2009 February

DOI:10.1007/s10971-008-1869-y

A new synthetic route to nanoparticulate tungsten carbide–cobalt is demonstrated, using a sol–gel approach in an aqueous solution containing a biopolymer. On calcination, the biopolymer was found to act both as a source of carbon and also as an anti-sintering, structure-directing template. By keeping the tungsten carbide phase nanoparticulate, the hardness was found to be commensurate with that seen in more traditional ‘heat and beat’ syntheses.

Structural Evolution of Superconductor Nanowires in Biopolymer Gels

Co-reporter:Zoe A. C. Schnepp;Stuart C. Wimbush;Stephen Mann

Advanced Materials 2008 Volume 20( Issue 9) pp:1782-1786

Publication Date(Web):

DOI:10.1002/adma.200702679

Biomimetic Synthesis of High-Tc, Type-II Superconductor Nanowires

Co-reporter:S. R. Hall

Advanced Materials 2006 Volume 18(Issue 4) pp:487-490

Publication Date(Web):18 JAN 2006

DOI:10.1002/adma.200501971

Chitosan from crab shells is used to control the synthesis of superconductors. The morphological control over crystallization provided by the chitosan matrix during calcination allows the production of nanowires of the high-T_c superconductor Y124 (YBa₂Cu₄O₈). SQUID magnetometry of these nanowires indicates that the high T_c is successfully retained in this highly anisotropic and technologically important morphology.

Addition of Iridium to the Biopolymer Mediated Synthesis of YBa2Cu3O7 δ

Co-reporter:Stuart C. Wimbush, Werner Marx, Andreas Barth, Simon R. Hall

Physics Procedia (2012) Volume 36() pp:544-550

Publication Date(Web):1 January 2012

DOI:10.1016/j.phpro.2012.06.081

This work represents the first study into the addition of iridium into the solgel synthesis of the high temperature superconductor YBa2Cu3O7δ (Y123). Through a biopolymermediated synthetic approach, the homogeneous nature of the precursor sol and the preferred nucleation and growth of Y123 phases allow for a high yield of superconducting nanoparticles with no suppression of the superconducting critical temperature, even at high levels (40 wt%) of iridium addition. We attribute this to iridium not substituting into the Y123 crystal lattice, instead forming an associate phase.

Designed 3D architectures of high-temperature superconductors

Co-reporter:David C. Green, Martin R. Lees and Simon R. Hall

Chemical Communications 2013 - vol. 49(Issue 29) pp:NaN2976-2976

Publication Date(Web):2013/01/31