Publications
117 results found
Payne D, Cali E, Thomas M, et al., 2023, Real-time insight into the multistage mechanism of nanoparticle exsolution from a perovskite host surface, Nature Communications, Vol: 14, Pages: 1-10, ISSN: 2041-1723
In exsolution, nanoparticles form by emerging from oxide hosts by application of redox driving forces, leading to transformative advances in stability, activity, and efficiency over deposition techniques, and resulting in a wide range of new opportunities for catalytic, energy and net-zero-related technologies. However, the mechanism of exsolved nanoparticle nucleation and perovskite structural evolution, has, to date, remained unclear. Herein, we shed light on this elusive process by following in real time Ir nanoparticle emergence from a SrTiO3 host oxide lattice, using in situ high-resolution electron microscopy in combination with computational simulations and machine learning analytics. We show that nucleation occurs via atom clustering, in tandem with host evolution, revealing the participation of surface defects and host lattice restructuring in trapping Ir atoms to initiate nanoparticle formation and growth. These insights provide a theoretical platform and practical recommendations to further the development of highly functional and broadly applicable exsolvable materials.
Solanki A, Autefage H, Rodriguez A, et al., 2023, Cobalt containing glass fibres and their synergistic effect on the HIF-1 pathway for wound healing applications, Frontiers in Bioengineering and Biotechnology, Vol: 11, Pages: 1-15, ISSN: 2296-4185
Introduction and Methods: Chronic wounds are a major healthcare problem, but their healing may be improved by developing biomaterials which can stimulate angiogenesis, e.g. by activating the Hypoxia Inducible Factor (HIF) pathway. Here, novel glass fibres were produced by laser spinning. The hypothesis was that silicate glass fibres that deliver cobalt ions will activate the HIF pathway and promote the expression of angiogenic genes. The glass composition was designed to biodegrade and release ions, but not form a hydroxyapatite layer in body fluid.Results and Discussion: Dissolution studies demonstrated that hydroxyapatite did not form. When keratinocyte cells were exposed to conditioned media from the cobalt-containing glass fibres, significantly higher amounts of HIF-1α and Vascular Endothelial Growth Factor (VEGF) were measured compared to when the cells were exposed to media with equivalent amounts of cobalt chloride. This was attributed to a synergistic effect of the combination of cobalt and other therapeutic ions released from the glass. The effect was also much greater than the sum of HIF-1α and VEGF expression when the cells were cultured with cobalt ions and with dissolution products from the Co-free glass, and was proven to not be due to a rise in pH. The ability of the glass fibres to activate the HIF-1 pathway and promote VEGF expression shows the potential for their use in chronic wound dressings.
Lei B, Warren L, Morrison C, et al., 2023, Computational and experimental studies of the wide bandgap semiconductors NH<sub>4</sub>TiOF<sub>3</sub> and (NH<sub>4</sub>)<sub>2</sub>TiOF<sub>4</sub>, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, Vol: 25, Pages: 4701-4709, ISSN: 1463-9076
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- Citations: 2
Arrigo R, Aureau D, Bhatt P, et al., 2022, <i>In situ</i> methods: discoveries and challenges: general discussion, FARADAY DISCUSSIONS, Vol: 236, Pages: 219-266, ISSN: 1359-6640
Arrigo R, Ban L, Bartels-Rausch T, et al., 2022, Future directions: general discussion., Faraday Discuss, Vol: 236, Pages: 412-428
Offi F, Yamauchi K, Picozzi S, et al., 2021, Identification of hidden orbital contributions in the La<sub>0.65</sub>Sr<sub>0.35</sub>MnO<sub>3</sub> valence band, PHYSICAL REVIEW MATERIALS, Vol: 5, ISSN: 2475-9953
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- Citations: 2
Harrison J, Lee J, Ormsby B, et al., 2021, The influence of light and relative humidity on the formation of epsomite in cadmium yellow and French ultramarine modern oil paints, HERITAGE SCIENCE, Vol: 9, ISSN: 2050-7445
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- Citations: 4
Moss B, Wang Q, Butler K, et al., 2021, Linking in situ charge accumulation to electronic structure in doped SrTiO3 reveals design principles for hydrogen-evolving photocatalysts, Nature Materials, Vol: 20, Pages: 511-517, ISSN: 1476-1122
Recently, high solar-to-hydrogen efficiencies were demonstrated using La and Rh co-doped SrTiO3 (La,Rh:SrTiO3) incorporated into a low-cost and scalable Z-scheme device, known as a photocatalyst sheet. However, the unique properties that enable La,Rh:SrTiO3 to support this impressive performance are not fully understood. Combining in situ spectroelectrochemical measurements with density functional theory and photoelectron spectroscopy produces a depletion model of Rh:SrTiO3 and La,Rh:SrTiO3 photocatalyst sheets. This reveals remarkable properties, such as deep flatband potentials (+2 V versus the reversible hydrogen electrode) and a Rh oxidation state dependent reorganization of the electronic structure, involving the loss of a vacant Rh 4d mid-gap state. This reorganization enables Rh:SrTiO3 to be reduced by co-doping without compromising the p-type character. In situ time-resolved spectroscopies show that the electronic structure reorganization induced by Rh reduction controls the electron lifetime in photocatalyst sheets. In Rh:SrTiO3, enhanced lifetimes can only be obtained at negative applied potentials, where the complete Z-scheme operates inefficiently. La co-doping fixes Rh in the 3+ state, which results in long-lived photogenerated electrons even at very positive potentials (+1 V versus the reversible hydrogen electrode), in which both components of the complete device operate effectively. This understanding of the role of co-dopants provides a new insight into the design principles for water-splitting devices based on bandgap-engineered metal oxides.
Mielewczyk-Gryn A, Wachowski S, Witkowska A, et al., 2020, Antimony substituted lanthanum orthoniobate proton conductor - Structure and electronic properties, JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Vol: 103, Pages: 6575-6585, ISSN: 0002-7820
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- Citations: 4
Isakov I, Faber H, Mottram AD, et al., 2020, Quantum Confinement and Thickness-Dependent Electron Transport in Solution-Processed In<sub>2</sub>O<sub>3</sub>Transistors, ADVANCED ELECTRONIC MATERIALS, Vol: 6, ISSN: 2199-160X
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- Citations: 12
Cali E, Kerherve G, Naufal F, et al., 2020, Exsolution of catalytically active iridium nanoparticles from strontium titanate, ACS Applied Materials and Interfaces, Vol: 12, Pages: 37444-37453, ISSN: 1944-8244
The search for new functional materials that combine high stability and efficiency with reasonable cost and ease of synthesis is critical for their use in renewable energy applications. Specifically in catalysis, nanoparticles, with their high surface-to-volume ratio, can overcome the cost implications associated with otherwise having to use large amounts of noble metals. However, commercialized materials, that is, catalytic nanoparticles deposited on oxide supports, often suffer from loss of activity because of coarsening and carbon deposition during operation. Exsolution has proven to be an interesting strategy to overcome such issues. Here, the controlled emergence, or exsolution, of faceted iridium nanoparticles from a doped SrTiO3 perovskite is reported and their growth preliminary probed by in situ electron microscopy. Upon reduction of SrIr0.005Ti0.995O3, the generated nanoparticles show embedding into the oxide support, therefore preventing agglomeration and subsequent catalyst degradation. The advantages of this approach are the extremely low noble metal amount employed (∼0.5% weight) and the catalytic activity reported during CO oxidation tests, where the performance of the exsolved SrIr0.005Ti0.995O3 is compared to the activity of a commercial catalyst with 1% loading (1% Ir/Al2O3). The high activity obtained with such low doping shows the possibility of scaling up this new catalyst, reducing the high cost associated with iridium-based materials.
Kousi K, Neagu D, Bekris L, et al., 2020, Low temperature methane conversion with perovskite-supported<i>exo</i>/<i>endo</i>-particles, JOURNAL OF MATERIALS CHEMISTRY A, Vol: 8, Pages: 12406-12417, ISSN: 2050-7488
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- Citations: 16
Ryan PTP, Lalaguna PL, Haag F, et al., 2020, Validation of the inverted adsorption structure for free-base tetraphenyl porphyrin on Cu(111), CHEMICAL COMMUNICATIONS, Vol: 56, Pages: 3681-3684, ISSN: 1359-7345
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- Citations: 10
Jakub Z, Hulva J, Ryan PTP, et al., 2020, Adsorbate-induced structural evolution changes the mechanism of CO oxidation on a Rh/Fe<sub>3</sub>O<sub>4</sub>(001) model catalyst, NANOSCALE, Vol: 12, Pages: 5866-5875, ISSN: 2040-3364
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- Citations: 18
Bigi C, Orgiani P, Slawinska J, et al., 2020, Direct insight into the band structure of SrNbO<sub>3</sub>, PHYSICAL REVIEW MATERIALS, Vol: 4, ISSN: 2475-9953
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- Citations: 13
Lin C-T, Lee J, Kim J, et al., 2020, Origin of open-circuit voltage enhancements in planar Perovskite solar cells induced by addition of bulky organic cations, Advanced Functional Materials, Vol: 30, ISSN: 1616-301X
The origin of performance enhancements in p‐i‐n perovskite solar cells (PSCs) when incorporating low concentrations of the bulky cation 1‐naphthylmethylamine (NMA) are discussed. A 0.25 vol % addition of NMA increases the open circuit voltage (Voc) of methylammonium lead iodide (MAPbI3) PSCs from 1.06 to 1.16 V and their power conversion efficiency (PCE) from 18.7% to 20.1%. X‐ray photoelectron spectroscopy and low energy ion scattering data show NMA is located at grain surfaces, not the bulk. Scanning electron microscopy shows combining NMA addition with solvent assisted annealing creates large grains that span the active layer. Steady state and transient photoluminescence data show NMA suppresses non‐radiative recombination resulting from charge trapping, consistent with passivation of grain surfaces. Increasing the NMA concentration reduces device short‐circuit current density and PCE, also suppressing photoluminescence quenching at charge transport layers. Both Voc and PCE enhancements are observed when bulky cations (phenyl(ethyl/methyl)ammonium) are incorporated, but not smaller cations (Cs/MA)—indicating size is a key parameter. Finally, it demonstrates that NMA also enhances mixed iodide/bromide wide bandgap PSCs (Voc of 1.22 V with a 1.68 eV bandgap). The results demonstrate a facile approach to maximizing Voc and provide insights into morphological control and charge carrier dynamics induced by bulky cations in PSCs.
Ryan PTP, Meier M, Jakub Z, et al., 2020, Probing structural changes upon carbon monoxide coordination to single metal adatoms, JOURNAL OF CHEMICAL PHYSICS, Vol: 152, ISSN: 0021-9606
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- Citations: 3
Kim N, Thomas MR, Bergholt MS, et al., 2020, Surface enhanced raman scattering artificial nose for high dimensionality fingerprinting, Nature Communications, Vol: 11, ISSN: 2041-1723
Label-free surface-enhanced Raman spectroscopy (SERS) can interrogate systems by directly fingerprinting its components’ unique physicochemical properties. In complex biological systemshowever, this can yield highly overlapping spectra that hinder sample identification. Here, we present an artificial-nose inspired SERS fingerprinting approach where spectral data is obtained as a function of sensor surface chemical functionality. Supported by molecular dynamics modelling, we show that mildly selective self-assembled monolayers can influence the strength and configuration in which analytes interact with plasmonic surfaces, diversifying the resulting SERS fingerprints. Since each sensor generates a modulated signature, the implicit value of increasing the dimensionality of datasets is shown using cell lysates for all possible combinations of up to 9 fingerprints. Reliable improvements in mean discriminatory accuracy towards 100% is achieved with each additional surface functionality. This arrayed label-free platform illustrates the wide-ranging potential of high dimensionality artificial-nose based sensing systems for more reliable assessment of complex biological matrices.
Mielewczyk-Gryn A, Wachowski S, Przesniak-Welenc M, et al., 2019, Water uptake analysis of acceptor-doped lanthanum orthoniobates, Journal of Thermal Analysis and Calorimetry: an international forum for thermal studies, Vol: 138, Pages: 225-232, ISSN: 1588-2926
In this work, lanthanum orthoniobates doped with either antimony, calcium, or both have been synthesized and studied. The water uptake of the investigated materials has been analyzed by means of thermogravimetric studies. The results show the difference between the thermodynamics of hydration between the lanthanum orthoniobate system and other proton conducting ceramics. The relation between the water uptake and effective acceptor doping for the investigated system has been found, and the energetics of the water uptake relation are discussed.
Fogarty R, Palgrave R, Bourne R, et al., 2019, Electron spectroscopy of ionic liquids: experimental identification of atomic orbital contributions to valence electronic structure, Physical Chemistry Chemical Physics, Vol: 21, Pages: 18893-18910, ISSN: 1463-9076
The atomic contributions to valence electronic structure for 37 ionic liquids (ILs) are identified using a combination of variable photon energy XPS, resonant Auger electron spectroscopy (RAES) and a subtraction...</p>
Tan SY, Payne DJ, Hallett JP, et al., 2019, Developments in electrochemical processes for recycling lead-acid batteries, Current Opinion in Electrochemistry, Vol: 16, Pages: 83-89, ISSN: 2451-9103
The lead-acid battery recycling industry is very well established, but the conventional pyrometallurgical processes are far from environmentally benign. Hence, recent developments of lead-acid battery recycling technologies have focused on low-temperature (electro-)hydrometallurgical processes, the subject of this review, covering modified electrolytes, improved reaction engineering, better reactor design and control of operating conditions.
Twyman N, Tetzner K, Anthopoulos T, et al., 2019, Rapid photonic curing of solution-processed In2O3 layers on flexible substrates, Applied Surface Science, Vol: 479, Pages: 974-979, ISSN: 0169-4332
In2O3 is one of the most important semiconducting metal oxides primarily because of its wide band gap, high electron mobility and processing versatility. To this end, high-quality thin films of In2O3 can be prepared using scalable and inexpensive solution-based deposition methods, hence making it attractive for application in a number of emerging electronic applications. However, traditional solution processing often requires high temperature and lengthy annealing steps, making it impossible to use in combination with temperature-sensitive plastic substrates, which would be desired for numerous emerging flexible device applications. Here, rapid photonic curing of In2O3 layers is explored as an alternative to thermal annealing. Oxide thin films are successfully prepared on a range of substrates, including glass, polyimide, and polyethylene naphthalate. The effect of substrate and post-processing treatment on the morphology, surface chemistry, and electronic properties is investigated by atomic force microscopy and X-ray photoelectron spectroscopy. Systematic trends are identified, particularly in the degree of conversion of the precursor and its influence on the electronic structure.
Robinson MDM, Oropeza FE, Cui M, et al., 2019, Electronic structure of lanthanide-doped bismuth vanadates: A systematic study by x-ray photoelectron and optical spectroscopies, Journal of Physical Chemistry C, Vol: 123, Pages: 8484-8499, ISSN: 1932-7447
Monoclinic BiVO 4 has emerged in recent years as one of the most promising materials for photocatalytic evolution of oxygen under solar irradiation. However, it is in itself unable to phototcatalyze reduction of water to hydrogen due to the placement of the conduction band edge below the potential required for H 2 O/H 2 reduction. As a consequence, BiVO 4 only finds application in a hybrid system. Very recently, tetragonal lanthanide-doped BiVO 4 powders have been shown to be able to both reduce and to oxidize water under solar irradiation, but to date there has been no comprehensive study of the electronic properties of lanthanide-doped bismuth vanadates aimed at establishing the systematic trends in the electronic structure in traversing the lanthanide series. Here, the accessible family of lanthanide-doped BiVO 4 quaternary oxides of stoichiometry Bi 0.5 Ln 0.5 VO 4 (Ln = La to Lu, excluding Pm) has been studied by X-ray powder diffraction, X-ray photoemission spectroscopy, and diffuse reflectance optical spectroscopy. The compounds all adopt the tetragonal zircon structure, and lattice parameters decrease monotonically in traversing the lanthanide series. At the same time, there is an increased peak broadening in the diffraction patterns as the mismatch in ionic radius between Bi 3+ and the Ln 3+ ions increases across the series. Valence band X-ray photoemission spectra show that the final state 4f n-1 structure associated with ionization of lanthanide 4f n states is superimposed on the valence band structure of BiVO 4 in the quaternary materials: in the case of the Ce-, Pr- and Tb-doped BiVO 4 , 4f-related states appear above the top of the main valence band of BiVO 4 and account for the small bandgap in the Ce compound. In all cases, the 4f structure is characteristic of the lanthanide element in the Ln(III) oxidation state. Vanadium 2p and lanthanide 3d or 4d core level photoelectron spectra of those compounds where the lanthanide may in principle adopt a hig
Leber R, Wilson L, Robaschik P, et al., 2019, Vacuum deposition of biferrocene thin films: growth strategies for stability and tuneable magnetism, 257th National Meeting of the American-Chemical-Society (ACS), Publisher: AMER CHEMICAL SOC, ISSN: 0065-7727
Regoutz A, Ganose AM, Blumenthal L, et al., 2019, Insights into the electronic structure of OsO2 using soft and hard x-ray photoelectron spectroscopy in combination with density functional theory, Physical Review Materials, Vol: 3, ISSN: 2475-9953
Theory and experiment are combined to gain an understanding of the electronic properties of OsO2, a poorly studied metallic oxide that crystallizes in the rutile structure. Hard and soft valence-band x-ray photoemission spectra of OsO2 single crystals are in broad agreement with the results of density-functional-theory calculations, aside from a feature shifted to high binding energy of the conduction band. The energy shift corresponds to the conduction electron plasmon energy measured by reflection electron energy loss spectroscopy. The plasmon satellite is reproduced by many-body perturbation theory.
Davies DW, Walsh A, Mudd JJ, et al., 2019, Identification of lone-pair surface states on indium oxide, Journal of Physical Chemistry C, Vol: 123, Pages: 1700-1709, ISSN: 1932-7447
Indium oxide is widely used as a transparent electrode in optoelectronic devices and as a photocatalyst with activity for reduction of CO2. However, very little is known about the structural and electronic properties of its surfaces, particularly those prepared under reducing conditions. In this report, directional “lone-pair” surface states associated with filled 5s2 orbitals have been identified on vacuum-annealed In2O3(111) through a combination of hard and soft X-ray photoemission spectroscopy and density functional theory calculations. The lone pairs reside on indium ad-atoms in a formal +1 oxidation state, each of which traps two electrons into a localized hybrid orbital protruding away from the surface and lying just above the valence band maximum in photoemission spectra. The third electron associated with the ad-atoms is delocalized into the conduction band, thus producing the surface electron accumulation layer identified previously on vacuum-annealed In2O3(111) (1 × 1) surfaces. The surface structure is further supported by low-energy electron diffraction, but there is no chemical shift in indium core level X-ray photoelectron spectra between surface In(I) ad-atoms and bulk In(III). The 5s2 lone pairs confer Lewis basicity on the surface In sites and may have a pronounced impact on the catalytic or photocatalytic activity of reduced In2O3.
Baker SJ, Payne DJ, Rappuoli R, et al., 2018, Technologies to address antimicrobial resistance, PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, Vol: 115, Pages: 12887-12895, ISSN: 0027-8424
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- Citations: 80
Regoutz A, Kerherve G, Villar-Garcia I, et al., 2018, The influence of oxygen on the surface interaction between CO2 and copper studied by ambient pressure X-ray photoelectron spectroscopy, SURFACE SCIENCE, Vol: 677, Pages: 121-127, ISSN: 0039-6028
Maher RC, Kerherve G, Payne DJ, et al., 2018, The reduction properties of M‐Doped (M=Zr, Gd) CeO2/YSZ scaffolds co‐infiltrated with nickel, Energy Technology, Vol: 6, Pages: 2045-2052, ISSN: 2194-4296
In recent years infiltration of materials into porous ceramic scaffolds has been shown to be an effective way of creating catalytically active components for solid oxide fuel cells (SOFCs). However, the redox properties of these novel structures are not well understood. Here, we use X‐ray photoelectron spectroscopy (XPS) and in‐situ Raman spectroscopy to investigate the oxidation properties of yttria‐stabilised zirconia (YSZ) scaffolds infiltrated with ceria (CeO2), gadolinium‐doped ceria (GDC) and zirconia‐doped ceria (ZDC), with and without Ni. XPS shows that doping ceria with zirconia increases the ratio of Ce3+ to Ce4+, while gadolinium doping results in a decrease of Ce3+. The presence of Ni increases the Ce3+/Ce4+ ratio for CeO2 and GDC, but had little effect on ZDC. We used the shift of the F2g Raman peak to monitor in‐situ, the oxidation state of ceria. In the as‐made compounds, we show that while the gadolinium and zirconium dopants significantly change the oxidation characteristics of ceria, the resulting materials are only significantly reduced above 500 °C when co‐infiltrated with Ni. In‐situ Raman monitoring during reduction as a function of temperature showed that while ZDC reduces much more readily than undoped ceria or GDC, the presence of Ni dominated the reduction dynamics.
Connor PA, Yue X, Savaniu, et al., 2018, Tailoring SOFC electrode microstructures for improved performance, Advanced Energy Materials, Vol: 8, Pages: 1-20, ISSN: 1614-6832
The key technical challenges that fuel cell developers need to address are performance, durability, and cost. All three need to be achieved in parallel; however, there are often competitive tensions, e.g., performance is achieved at the expense of durability. Stability and resistance to degradation under prolonged operation are key parameters. There is considerable interest in developing new cathodes that are better able to function at lower temperature to facilitate low cost manufacture. For anodes, the ability of the solid oxide fuel cell (SOFC) to better utilize commonly available fuels at high efficiency, avoid coking and sulfur poisoning or resistance to oxidation at high utilization are all key. Optimizing a new electrode material requires considerable process development. The use of solution techniques to impregnate an already optimized electrode skeleton, offers a fast and efficient way to evaluate new electrode materials. It can also offer low cost routes to manufacture novel structures and to fine tune already known structures. Here impregnation methodologies are discussed, spectral and surface characterization are considered, and the recent efforts to optimize both cathode and anode functionalities are reviewed. Finally recent exemplifications are reviewed and future challenges and opportunities for the impregnation approach in SOFCs are explored.
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