B18-Core EXAFS
E01-JEM ARM 200CF
I09-Surface and Interface Structural Analysis
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Thomas J.
Liddy
,
Benjamin J.
Young
,
Emerson C.
Kohlrausch
,
Andreas
Weilhard
,
Gazi N.
Aliev
,
Yifan
Chen
,
Manfred E.
Schuster
,
Mohsen
Danaie
,
Luke L.
Keenan
,
Donato
Decarolis
,
Diego
Gianolio
,
Siqi
Wang
,
Mingming
Zhu
,
Graham J.
Hutchings
,
David M.
Grant
,
Wolfgang
Theis
,
Tien-Lin
Lee
,
David A.
Duncan
,
Alberto
Roldan
,
Andrei N.
Khlobystov
,
Jesum
Alves Fernandes
Diamond Proposal Number(s):
[38764]
Open Access
Abstract: Ammonia is an attractive hydrogen carrier, yet its practical use is limited by the need for efficient catalytic decomposition. We demonstrate that in-situ N-doping of Ru nanoparticles and graphitized carbon nanofiber supports during reaction produces a sharp increase in hydrogen production during the first 40 h, followed by stable activity. Spectroscopic and microscopic analyses, together with density functional theory simulations, reveal that Ru nitridation is rapid and support-independent, resulting in a mechanistic shift from the traditional Langmuir–Hinshelwood to a Mars–van Krevelen pathway, further confirmed by isotopic labelling experiments. In contrast, the progressive nitridation of the carbon support, observed via X-ray photoelectron spectroscopy, modulates the electronic environment of Ru and functions as a dynamic nitrogen reservoir that enables reversible N atoms exchange with the Ru particles, facilitating N desorption from the Ru surface and thereby governing the catalytic activity enhancement. These new findings provide new mechanistic insight into ammonia decomposition and establish progressive nitrogen doping of carbon supports as a strategy for designing efficient metal-based catalysts for hydrogen production.
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Dec 2025
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I09-Surface and Interface Structural Analysis
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Ali
Sufyan
,
Tyler
James
,
Connor
Fields
,
Shabnam
Naseri
,
Filipe L. Q.
Junqueira
,
Sofia
Alonso Perez
,
Sally
Bloodworth
,
Gabriella
Hoffman
,
Mark C.
Walkey
,
Elizabeth S.
Marsden
,
Richard J.
Whitby
,
Yitao
Wang
,
David A.
Duncan
,
Tien-Lin
Lee
,
James N.
O'Shea
,
Andreas
Larsson
,
Brian
Kiraly
,
Philip
Moriarty
Diamond Proposal Number(s):
[31574]
Open Access
Abstract: Core-level and tunnelling spectroscopies applied to noble gas endofullerenes offer complementary insights into electron transfer rates, addressing both intramolecular and extramolecular processes. Elastic and inelastic tunnelling spectroscopy of empty C60 and Kr@C60 on Pb/Cu(111) each show that the encapsulated atom is essentially invisible to scanning probes. We interpret the lineshape of the lowest unoccupied molecular orbital (LUMO) of Pb-adsorbed (endo)fullerenes in tunnelling spectra as a signature of the dynamic Jahn-Teller (DJ-T) effect. This effect persists in electronically decoupled second-layer molecules, which also display distinct vibronic progressions in on-resonance tunnelling. DFT calculations reproduce the LUMO alignment and low density of states at the Fermi level seen in experimental tunnelling spectra for (endo)fullerenes on Pb, and, in line with submolecular resolution STM images, also predict that an atom-down orientation of the fullerene cage is energetically most favourable (although other adsorption geometries differ only by tens of meV at most). In contrast to the tunnelling data, core-level-focussed techniques -namely, photoemission, X-ray absorption, and resonant Auger-Meitner electron spectroscopy -of Ar@C60/Pb(111) indicate that the encapsulated atom is heavily coupled to the molecular environment, with both a clear influence of substrate screening on the core-level lineshape and the absence of spectator signal in decay spectra.
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Oct 2025
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E02-JEM ARM 300CF
I09-Surface and Interface Structural Analysis
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Benedikt P.
Klein
,
Matthew A.
Stoodley
,
Joel
Deyerling
,
Luke A.
Rochford
,
Dylan B.
Morgan
,
David G.
Hopkinson
,
Sam
Sullivan-Allsop
,
Henry
Thake
,
Fulden
Eratam
,
Lars
Sattler
,
Sebastian M.
Weber
,
Gerhard
Hilt
,
Alexander
Generalov
,
Alexei
Preobrajenski
,
Thomas
Liddy
,
Leon B. S.
Williams
,
Mhairi A.
Buchan
,
Graham A
Rance
,
Tien-Lin
Lee
,
Alex
Saywell
,
Roman
Gorbachev
,
Sarah J.
Haigh
,
Christopher S.
Allen
,
Willi
Auwärter
,
Reinhard
Maurer
,
David A.
Duncan
Diamond Proposal Number(s):
[25379, 30875, 31695, 31165, 33709]
Open Access
Abstract: Chemical vapour deposition enables large-domain growth of ideal graphene, yet many applications of graphene require the controlled inclusion of specific defects. We present a one-step chemical vapour deposition procedure aimed at retaining the precursor topology when incorporated into the grown carbonaceous film. When azupyrene, the molecular analogue of the Stone–Wales defect in graphene, is used as a precursor, carbonaceous monolayers with a range of morphologies are produced as a function of the copper substrate growth temperature. The higher the substrate temperature during deposition, the closer the resulting monolayer is to ideal graphene. Analysis, with a set of complementary materials characterisation techniques, reveals morphological changes closely correlated with changes in the atomic adsorption heights, network topology, and concentration of 5-/7-membered carbon rings. The engineered defective carbon monolayers can be transferred to different substrates, potentially enabling applications in nanoelectronics, sensorics, and catalysis.
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Sep 2025
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Open Access
Abstract: Combined density functional theory (DFT) and X-ray standing wave (XSW) studies have previously provided evidence for the preferential adoption of an inverted conformation of 2H-TPP on Cu(111) in contrast to the saddle conformation usually favored by porphyrin molecules adsorbed on metals. We experimentally demonstrate, via X-ray photoelectron spectroscopy (XPS) analysis, that the binding energies of the aminic and iminic nitrogen species provide a spectral fingerprint for both inverted and saddle conformations, as predicted by DFT studies. Our complementary scanning tunneling microscopy (STM) characterization also reveals conversion from the saddle to inverted conformation at an elevated temperature for an analogous porphyrin species (Br2TPP).
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May 2025
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I09-Surface and Interface Structural Analysis
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Connor
Fields
,
Aleksandra
Foerster
,
Sadegh
Ghaderzadeh
,
Ilya
Popov
,
Bang
Huynh
,
Filipe
Junqueira
,
Tyler
James
,
Sofia
Alonso Perez
,
David A.
Duncan
,
Tien-Lin
Lee
,
Yitao
Wang
,
Sally
Bloodworth
,
Gabriela
Hoffman
,
Mark
Walkey
,
Richard J.
Whitby
,
Malcolm H.
Levitt
,
Brian
Kiraly
,
James N.
O'Shea
,
Elena
Besley
,
Philip
Moriarty
Diamond Proposal Number(s):
[31574]
Open Access
Abstract: Charge transfer is fundamentally dependent on the overlap of the orbitals comprising the transport pathway. This has key implications for molecular, nanoscale, and quantum technologies, for which delocalization (and decoherence) rates are essential figures of merit. Here, we apply the core hole clock technique—an energy-domain variant of ultrafast spectroscopy—to probe the delocalization of a photoexcited electron inside a closed molecular cage, namely the Ar 2p54s1 state of Ar@C60. Despite marginal frontier orbital mixing in the ground configuration, almost 80% of the excited state density is found outside the buckyball due to the formation of a markedly diffuse hybrid orbital. Far from isolating the intracage excitation, the surrounding fullerene is instead a remarkably efficient conduit for electron transfer: we measure characteristic delocalization times of 6.6 ± 0.3 fs and ≲ 500 attoseconds, respectively, for a 3D Ar@C60 film and a 2D monolayer on Ag(111).
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May 2025
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I09-Surface and Interface Structural Analysis
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Jake M.
Seymour
,
Ekaterina
Gousseva
,
Lewis G.
Parker
,
Frances K.
Towers Tompkins
,
Richard M.
Fogarty
,
Lennart
Frankemoelle
,
Rebecca
Rowe
,
Coby J.
Clarke
,
David A.
Duncan
,
Robert G.
Palgrave
,
Roger A.
Bennett
,
Patricia A.
Hunt
,
Kevin R. J.
Lovelock
Diamond Proposal Number(s):
[20463]
Open Access
Abstract: Liquid-phase d10s2 post-transition metal anions, such as [SnCl3]−, appear in a range of applications with a focus on catalysis and material preparation. However, little is known about their electronic structure and how it relates to reactivity. Using X-ray photoelectron spectroscopy and ab initio calculations, we demonstrate that liquid-phase d10s2 post-transition metal anions can act as dual-mode Lewis bases, interacting through the metal center and/or the ligands, with the interaction mode depending on the identity of the Lewis acid/electron acceptor. The Lewis basicity of the metal donor atom is controlled mainly by the metal identity; the ligand can be used for fine-tuning. Changing the metal center has a strong effect on the ligand basicity. These findings provide insight into d10s2 post-transition metal anion electronic structure, which will enable better molecular-level design of catalytic systems.
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Mar 2025
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I09-Surface and Interface Structural Analysis
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Open Access
Abstract: The synthesis of large, freestanding, single-atom-thick two-dimensional (2D) metallic materials remains challenging due to the isotropic nature of metallic bonding. Here, we present a bottom-up approach for fabricating macroscopically large, nearly freestanding 2D gold (Au) monolayers, consisting of nanostructured patches. By forming Au monolayers on an Ir(111) substrate and embedding boron (B) atoms at the Au/Ir interface, we achieve suspended monoatomic Au sheets with hexagonal structures and triangular nanoscale patterns. Alternative patterns of periodic nanodots are observed in Au bilayers on the B/Ir(111) substrate. Using scanning tunneling microscopy, X-ray spectroscopies, and theoretical calculations, we reveal the role of buried B species in forming the nanostructured Au layers. Changes in the Au monolayer’s band structure upon substrate decoupling indicate a transition from 3D to 2D metal bonding. The resulting Au films exhibit remarkable thermal stability, making them practical for studying the catalytic activity of 2D gold.
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Dec 2024
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I09-Surface and Interface Structural Analysis
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Dennis
Meier
,
Peter
Knecht
,
Pablo
Vezzoni Vicente
,
Fulden
Eratam
,
Hongxiang
Xu
,
Tien-Lin
Lee
,
Alexander
Generalov
,
Alexander
Riss
,
Biao
Yang
,
Francesco
Allegretti
,
Peter
Feulner
,
Joachim
Reichert
,
Johannes V.
Barth
,
Ari Paavo
Seitsonen
,
David A.
Duncan
,
Anthoula C.
Papageorgiou
Diamond Proposal Number(s):
[30095]
Open Access
Abstract: Metalloporphyrins on interfaces offer a rich playground for functional materials and hence have been subjected to intense scrutiny over the past decades. As the same porphyrin macrocycle on the same surface may exhibit vastly different physicochemical properties depending on the metal center and its substituents, it is vital to have a thorough structural and chemical characterization of such systems. Here, we explore the distinctions arising from coverage and macrocycle substituents on the closely related ruthenium octaethyl porphyrin and ruthenium tetrabenzo porphyrin on Ag(111). Our investigation employs a multitechnique approach in ultrahigh vacuum, combining scanning tunneling microscopy, low-energy electron diffraction, photoelectron spectroscopy, normal incidence X-ray standing wave, and near-edge X-ray absorption fine structure, supported by density functional theory. This methodology allows for a thorough examination of the nuanced differences in the self-assembly, substrate modification, molecular conformation and adsorption height.
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Dec 2024
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I09-Surface and Interface Structural Analysis
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Pablo
Vezzoni Vicente
,
Tobias
Weiss
,
Dennis
Meier
,
Wenchao
Zhao
,
Birce Sena
Tömekçe
,
Marc
G. Cuxart
,
Benedikt P.
Klein
,
David A.
Duncan
,
Tien-Lin
Lee
,
Anthoula C.
Papageorgiou
,
Matthias
Muntwiler
,
Ari Paavo
Seitsonen
,
Willi
Auwärter
,
Peter
Feulner
,
Johannes V.
Barth
,
Francesco
Allegretti
Diamond Proposal Number(s):
[25907]
Abstract: In light of the recent research interest in low-dimensional bismuth structures as spin-active materials and topological insulators, we present a comprehensive characterization of the Bi/Au(111) interface. The nuanced evolution of Bi phases upon deposition in ultrahigh vacuum (UHV) on a Au(111) surface is investigated from semidisordered clusters to few-layer Bi(110) thin films. Particular attention is devoted to the high-coverage, submonolayer phases, commonly grouped under the (𝑃×√3) nomenclature. We bring forth a new model, refining the current understanding of the Bi/Au(111) interface and demonstrating the existence of submonolayer moiré superstructures, whose geometry and superperiodicity depend on their coverage. This tuneable periodicity paves the way for their use as tailored buffer and templating layers for epitaxial growth of thin films on Au(111). Finally, we clarify the growth mode of multilayer Bi(110) as bilayer-by-bilayer, allowing precise thickness control of anisotropically strained thin films. This holistic understanding of the structural properties of the material was enabled by the synergy of several experimental techniques, namely low-energy electron diffraction (LEED), x-ray photoelectron spectroscopy (XPS), scanning tunneling microscopy and spectroscopy (STM, STS), and x-ray standing waves (XSW), further corroborated by density functional theory (DFT) simulations.
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Oct 2024
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I09-Surface and Interface Structural Analysis
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Paul
Ryan
,
Panukorn
Sombut
,
Ali
Rafsanjani-Abbasi
,
Chunlei
Wang
,
Fulden
Eratam
,
Francesco
Goto
,
Cesare
Franchini
,
Ulrike
Diebold
,
Matthias
Meier
,
David A.
Duncan
,
Gareth S.
Parkinson
Diamond Proposal Number(s):
[31726]
Open Access
Abstract: Water–solid interfaces pervade the natural environment and modern technology. On some surfaces, water–water interactions induce the formation of partially dissociated interfacial layers; understanding why is important to model processes in catalysis or mineralogy. The complexity of the partially dissociated structures often makes it difficult to probe them quantitatively. Here, we utilize normal incidence X-ray standing waves (NIXSW) to study the structure of partially dissociated water dimers (H2O–OH) at the α-Fe2O3(012) surface (also called the (11̅02) or “R-cut” surface): a system simple enough to be tractable yet complex enough to capture the essential physics. We find the H2O and terminal OH groups to be the same height above the surface within experimental error (1.45 ± 0.04 and 1.47 ± 0.02 Å, respectively), in line with DFT-based calculations that predict comparable Fe–O bond lengths for both water and OH species. This result is understood in the context of cooperative binding, where the formation of the H-bond between adsorbed H2O and OH induces the H2O to bind more strongly and the OH to bind more weakly compared to when these species are isolated on the surface. The surface OH formed by the liberated proton is found to be in plane with a bulk truncated (012) surface (−0.01 ± 0.02 Å). DFT calculations based on various functionals correctly model the cooperative effect but overestimate the water–surface interaction.
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Sep 2024
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