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187 items found (0 items not approved), displaying 1 to 10.[First/Prev] 1, 2, 3, 4, 5, 6, 7, 8 [Next/Last]

Instruments / Technical Area	Publication Details	Published
I06-Nanoscience (XPEEM)	Fabrication of isolated iron nanowires David C. Grinter , Bobbie-Jean A. Shaw , Chi L. Pang , Chi-Ming Yim , Christopher A. Muryn , Charlotte A. Hall , Francesco Maccherozzi , Sarnjeet S. Dhesi , Masahiko Suzuki , Tsuneo Yasue , Takanori Koshikawa , Geoff Thornton The Journal Of Physical Chemistry Letters DOI: 10.1021/acs.jpclett.3c02362 Diamond Proposal Number(s): [9824, 12815] Open Access Show Abstract ▼ Abstract: Nanoscale interconnects are an important component of molecular electronics. Here we use X-ray spectromicroscopy techniques as well as scanning probe methods to explore the self-assembled growth of insulated iron nanowires as a potential means of supplying an earth abundant solution. The intrinsic anisotropy of a TiO2(110) substrate directs the growth of micron length iron wires at elevated temperatures, with a strong metal–support interaction giving rise to ilmenite (FeTiO3) encapsulation. Iron nanoparticles that decorate the nanowires display magnetic properties that suggest other possible applications.	Sep 2023
I20-Scanning-X-ray spectroscopy (XAS/XES)	Using ex situ and in situ HERFD-XANES to reveal the superior oxidation and reduction cycling of ceria nanocubes dispersed in silica aerogel Lucy M. Morgan , Danilo Loche , Anna Corrias , Shusaku Hayama , Gavin Mountjoy The Journal Of Physical Chemistry C DOI: 10.1021/acs.jpcc.3c03785 Diamond Proposal Number(s): [19013] Open Access Show Abstract ▼ Abstract: The oxygen storage capacity of ceria-based catalytic materials is influenced by their size, morphology, and surface structure, which can be tuned using surfactant-mediated synthesis. In particular, the cuboidal morphology exposes the most reactive surfaces; however, when the capping agent is removed, the nanocubes can agglomerate and limit the available reactive surface. Here, we study ceria nanocubes, lanthanum-doped ceria nanocubes, and ceria nanocubes embedded inside a highly porous silica aerogel by high-energy resolution fluorescence detection─X-ray absorption near edge spectroscopy at the Ce L3 edge. In situ measurements showed an increased reversibility of redox cycles in ceria nanocubes when embedded in the aerogel, demonstrating enhanced reactivity due to the retention of reactive surfaces. These aerogel nanocomposites show greater improvement in the redox capacity and increased thermal stability of this catalytic material compared to the surfactant-capped nanocubes. Ex situ measurements were also performed to study the effect of lanthanum doping on the cerium oxidation state in the nanocubes, indicating a higher proportion of Ce4+ compared to that of the undoped ceria nanocubes.	Sep 2023
I15-1-X-ray Pair Distribution Function (XPDF)	Local order in liquid gallium-indium alloys Alfred Amon , Philip A. Chater , Gavin Vaughan , Rachael Smith , Christoph G. Salzmann The Journal Of Physical Chemistry C 263 DOI: 10.1021/acs.jpcc.3c03857 Diamond Proposal Number(s): [26945] Open Access Show Abstract ▼ Abstract: Liquid metals such as eutectic Ga–In alloys have low melting points and low toxicity and are used in catalysis and micro-robotics. This study investigates the local atomic structure of liquid gallium-indium alloys by a combination of density measurements, diffraction data, and Monte-Carlo simulation via the empirical potential structure refinement approach. A high-Q shoulder observed in liquid Ga is related to structural rearrangements in the second coordination shell. Structure analysis found coordination environments close to a random distribution for eutectic Ga–In alloy, while electronic effects appear to dominate the mixing enthalpy.	Aug 2023
I18-Microfocus Spectroscopy	Intermediates during the nucleation of platinum nanoparticles by a reaction with ethylene glycol: operando X-ray absorption spectroscopy studies with a microfluidic cell Sylvia Britto , Christopher M. A. Parlett , Stuart Bartlett , Joshua D. Elliott , Konstantin Ignatyev , Sven L. M. Schroeder The Journal Of Physical Chemistry C 38 DOI: 10.1021/acs.jpcc.2c08749 Diamond Proposal Number(s): [21484] Open Access Show Abstract ▼ Abstract: Using operando X-ray absorption spectroscopy in a continuous-flow microfluidic cell, we have investigated the nucleation of platinum nanoparticles from aqueous hexachloroplatinate solution in the presence of the reducing agent ethylene glycol. By adjusting flow rates in the microfluidic channel, we resolved the temporal evolution of the reaction system in the first few seconds, generating the time profiles for speciation, ligand exchange, and reduction of Pt. Detailed analysis of the X-ray absorption near-edge structure and extended X-ray absorption fine structure spectra with multivariate data analysis shows that at least two reaction intermediates are involved in the transformation of the precursor H2PtCl6 to metallic platinum nanoparticles, including the formation of clusters with Pt–Pt bonding before complete reduction to Pt nanoparticles.	May 2023
I09-Surface and Interface Structural Analysis	Zinc-porphine on coinage metal surfaces: adsorption configuration and ligand-induced central atom displacement Aleksandr Baklanov , Johannes T. Kuchle , David A. Duncan , Reinhard J. Maurer , Martin Schwarz , Eduardo Corral Rascon , Ignacio Piquero-Zulaica , Huynh Thien Ngo , Alexander Riss , Francesco Allegretti , Willi Auwärter , Paul T. P. Ryan The Journal Of Physical Chemistry C 35 DOI: 10.1021/acs.jpcc.3c00232 Diamond Proposal Number(s): [18874, 24276] Show Abstract ▼ Abstract: We present a comprehensive, quantitative multimethod characterization of the geometric and electronic interfacial structure of zinc-porphine (Zn-P) on coinage metal supports, namely, Ag(111) and Cu(111). Complementary techniques including X-ray standing waves, X-ray photoelectron spectroscopy, scanning tunneling microscopy, bond-resolved atomic force microscopy, and density functional theory calculations reveal the molecular conformations, signal a temperature-dependence of element-specific adsorption heights, rule out a decisive role of the d10 nature of the Zn center for the adsorption configuration, and uncover a considerably increased Zn-P adsorption height on Ag(111) compared to Cu(111). Furthermore, a pronounced out-of-plane displacement of the Zn center upon water ligation is demonstrated, a manifestation of the surface trans-effect. This study thus sheds light on effects of temperature, chemical nature of the metal center, its ligation, and the coinage metal support on interfacial structure and molecular deformation of an archetypical surface-anchored metal-tetrapyrrole.	Apr 2023
I07-Surface & interface diffraction	Direct experimental determination of Ag adatom locations in TCNQ-Ag 2D metal–organic framework on Ag(111) Philip J. Mousley , Luke A. Rochford , Hadeel Hussain , Stefania Moro , Pengcheng Ding , Gavin R. Bell , Giovanni Costantini , Christopher Nicklin , D. Phil Woodruff The Journal Of Physical Chemistry C DOI: 10.1021/acs.jpcc.2c07683 Diamond Proposal Number(s): [24284] Open Access Show Abstract ▼ Abstract: A previous investigation of the structure of TCNQ adsorbed on Ag(111) using normal-incidence X-ray standing waves (NIXSW) and density functional theory (DFT) provided indirect evidence that Ag adatoms must be incorporated into the molecular overlayer. New surface X-ray diffraction (SXRD) results, presented here, provide direct evidence for the presence and location of these Ag adatoms and clearly distinguishes between two alternative models of the adatom registry favored by two different DFT studies.	Feb 2023
I11-High Resolution Powder Diffraction	Donor–acceptor co-adsorption ratio controls the structure and electronic properties of two-dimensional alkali–organic networks on Ag(100) B. Sohail , P. J. Blowey , L. A. Rochford , P. T. P. Ryan , D. A. Duncan , T.-L. Lee , P. Starrs , G. Costantini , D. Phil Woodruff , R. J. Maurer The Journal Of Physical Chemistry C DOI: 10.1021/acs.jpcc.2c08688 Diamond Proposal Number(s): [17261, 20785] Open Access Show Abstract ▼ Abstract: The results are presented of a detailed combined experimental and theoretical investigation of the influence of coadsorbed electron-donating alkali atoms and the prototypical electron acceptor molecule 7,7,8,8-tetracyanoquinodimethane (TCNQ) on the Ag(100) surface. Several coadsorption phases were characterized by scanning tunneling microscopy, low-energy electron diffraction, and soft X-ray photoelectron spectroscopy. Quantitative structural data were obtained using normal-incidence X-ray standing wave (NIXSW) measurements and compared with the results of density functional theory (DFT) calculations using several different methods of dispersion correction. Generally, good agreement between theory and experiment was achieved for the quantitative structures, albeit with the prediction of the alkali atom heights being challenging for some methods. The adsorption structures depend sensitively on the interplay of molecule–metal charge transfer and long-range dispersion forces, which are controlled by the composition ratio between alkali atoms and TCNQ. The large difference in atomic size between K and Cs has negligible effects on stability, whereas increasing the ratio of K/TCNQ from 1:4 to 1:1 leads to a weakening of molecule–metal interaction strength in favor of stronger ionic bonds within the two-dimensional alkali–organic network. A strong dependence of the work function on the alkali donor–TCNQ acceptor coadsorption ratio is predicted.	Jan 2023
I11-High Resolution Powder Diffraction I15-1-X-ray Pair Distribution Function (XPDF)	On the local structure in ordered and disordered closo-hydroborate solid electrolytes Paul Till , Ryo Asakura , Arndt Remhof , Wolfgang G. Zeier The Journal Of Physical Chemistry C 1413 DOI: 10.1021/acs.jpcc.2c07835 Diamond Proposal Number(s): [26379] Show Abstract ▼ Abstract: Na+closo-hydroborates are a heavily researched solid electrolyte class for applications in all-solid-state Na batteries. The structural characterization of these materials is notoriously challenging due to the elements involved and the fast rotational motion of hydroborate cages. The average structures obtained by Bragg diffraction have numerous atomic positions with low occupancies, complicating the determination of actual atom–atom distances. Total average scattering and derived pair distribution functions display atom–atom distances in real space, providing additional structure information to the average crystal structure. In this work, we present the pair distribution functions of the five different Na+closo-hydroborates: Na2B10H10, Na2B12H12, NaCB11H12, and the mixtures of 1:1 Na2B12H12/Na2B10H10 and 2:1 NaCB11H12/Na2B12H12. All pair distribution functions show a fast decay of peak height with increasing atom–atom distance on the local scale, suggesting a low correlation of atom motions between hydroborate cages, as observed in various other molecular crystals. The combination of Bragg diffraction, showing the average ordering of closo-hydroborate cages, and pair distribution function analysis, providing local atom–atom distances, is a useful tool to develop a deeper understanding of the closo-hydroborates and also of other plastic crystals.	Jan 2023
	Characterizing molecule–metal surface chemistry with ab initio simulation of X-ray absorption and photoemission spectra Samuel J. Hall , Benedikt P. Klein , Reinhard J. Maurer The Journal Of Physical Chemistry C DOI: 10.1021/acs.jpcc.2c06996 Open Access Show Abstract ▼ Abstract: X-ray photoemission and X-ray absorption spectroscopy are important techniques to characterize chemical bonding at surfaces and are often used to identify the strength and nature of adsorbate–substrate interactions. In this study, we judge the ability of X-ray spectroscopic techniques to identify different regimes of chemical bonding at metal–organic interfaces. To achieve this, we sample different interaction strength regimes in a comprehensive and systematic way by comparing two topological isomers, azulene and naphthalene, adsorbed on three metal substrates with varying reactivity, namely the (111) facets of Ag, Cu, and Pt. Using density functional theory, we simulate core-level binding energies and X-ray absorption spectra of the molecular carbon species. The simulated spectra reveal three distinct characteristics based on the molecule-specific spectral features which we attribute to types of surface chemical bonding with varying strength. We find that weak physisorption only leads to minor changes compared to the gas-phase spectra, weak chemisorption leads to charge transfer and significant spectral changes, and strong chemisorption leads to a loss of the molecule-specific features in the spectra. The classification we provide is aimed at assisting interpretation of experimental X-ray spectra for complex metal–organic interfaces.	Jan 2023
I09-Surface and Interface Structural Analysis	Band alignments, electronic structure, and core-level spectra of bulk molybdenum dichalcogenides (MoS2, MoSe2, and MoTe2) Leanne A. H. Jones , Zongda Xing , Jack E. N. Swallow , Huw Shiel , Thomas J. Featherstone , Matthew J. Smiles , Nicole Fleck , Pardeep K. Thakur , Tien-Lin Lee , Laurence J. Hardwick , David O. Scanlon , Anna Regoutz , Tim D. Veal , Vinod R. Dhanak The Journal Of Physical Chemistry C 44 DOI: 10.1021/acs.jpcc.2c05100 Diamond Proposal Number(s): [25980] Open Access Show Abstract ▼ Abstract: A comprehensive study of bulk molybdenum dichalcogenides is presented with the use of soft and hard X-ray photoelectron (SXPS and HAXPES) spectroscopy combined with hybrid density functional theory (DFT). The main core levels of MoS2, MoSe2, and MoTe2 are explored. Laboratory-based X-ray photoelectron spectroscopy (XPS) is used to determine the ionization potential (IP) values of the MoX2 series as 5.86, 5.40, and 5.00 eV for MoSe2, MoSe2, and MoTe2, respectively, enabling the band alignment of the series to be established. Finally, the valence band measurements are compared with the calculated density of states which shows the role of p-d hybridization in these materials. Down the group, an increase in the p-d hybridization from the sulfide to the telluride is observed, explained by the configuration energy of the chalcogen p orbitals becoming closer to that of the valence Mo 4d orbitals. This pushes the valence band maximum closer to the vacuum level, explaining the decreasing IP down the series. High-resolution SXPS and HAXPES core-level spectra address the shortcomings of the XPS analysis in the literature. Furthermore, the experimentally determined band alignment can be used to inform future device work.	Dec 2022

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