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199 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
I09-Surface and Interface Structural Analysis	Quantitative measurement of cooperative binding in partially dissociated water dimers at the hematite “R-cut” surface 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 The Journal Of Physical Chemistry C 6 DOI: 10.1021/acs.jpcc.4c04537 Diamond Proposal Number(s): [31726] Open Access Show Abstract ▼ 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.	Sep 2024
	X-ray absorption spectroscopic study of the transition-metal-only double perovskite oxide Mn2CoReO6 Xiao Wang , Jie Zhang , Zhao Pan , Dabiao Lu , Maocai Pi , Xubin Ye , Cheng Dong , Jie Chen , Kai Chen , Florin Radu , Sonia Francoual , Stefano Agrestini , Zhiwei Hu , Chun-Fu Chang , Arata Tanaka , Kazunari Yamaura , Yao Shen , Youwen Long The Journal Of Physical Chemistry C DOI: 10.1021/acs.jpcc.4c04491 Show Abstract ▼ Abstract: By means of X-ray absorption spectroscopic studies, both experimentally and theoretically, we investigated the magnetic properties of the transition-metal-only double perovskite oxide Mn2CoReO6, which experiences an antiferromagnetic transition at TN = 93 K, whereas it holds a considerable net moment at low temperature. Internal exchange fields against the applied magnetic field for all the transition metal ions were identified, providing a microscopic insight into the intrasite antiferromagnetic couplings. Nevertheless, parallelly oriented canted spins of the Mn, Co, and Re cations were observed. In particularly, the Mn and Co cations hold considerable canting moments, which can be ascribed to the competition between the ferromagnetic intersite and antiferromagnetic intrasite magnetic interactions. Moreover, a spin-valve-type magnetoresistance was observed below the TN. The concurrence of the magnetoresistance effect and the antiferromagnetic semiconductive nature make Mn2CoReO6 a promising candidate for high-speed and energy-saving spintronics applications.	Sep 2024
B07-B1-Versatile Soft X-ray beamline: High Throughput ES1	La0.2Sr0.25Ca0.45TiO3 surface reactivity with H2: a combined operando NEXAFS and computational study F. Bassato , S. Mauri , L. Braglia , A. Yu. Petrov , E. Dobovičnik , F. Tavani , A. Tofoni , P. Ferrer , D. Grinter , G. Held , P. D'Angelo , P. Torelli The Journal Of Physical Chemistry Letters DOI: 10.1021/acs.jpclett.4c01900 Diamond Proposal Number(s): [33111] Show Abstract ▼ Abstract: A-site doped SrTiO3 is considered as a promising substitute for traditional anodic metals in solid oxide fuel cells (SOFCs). In this study, we present the reactivity of La0.2Sr0.25Ca0.45TiO3 (LCSTO), La0.2Sr0.7TiO3 (LSTO), and SrTiO3 (STO) toward H2 by operando ambient pressure NEXAFS spectroscopy and theoretical spectra simulation with FDMNES code. The samples were synthesized by MBE (molecular beam epitaxy), hydrothermal, and modified-Pechini routes. We found that the reducibility of the samples depends not only on their stoichiometry but also on the morphology, which is determined by the synthetic method. The results of these experiments give insight into the reducibility of Ti4+ in perovskites as well as the opportunity to further optimize the synthesis of these materials to obtain the best performance for SOFC applications.	Aug 2024
B07-B1-Versatile Soft X-ray beamline: High Throughput ES1	Effects of phosphorus doping on amorphous boron nitride’s chemical, sorptive, optoelectronic, and photocatalytic properties Ioanna Itskou , Andreas Kafizas , Irena Nevjestic , Soranyel Gonzalez Carrero , David C. Grinter , Hassan Azzan , Gwilherm Kerherve , Santosh Kumar , Tian Tian , Pilar Ferrer , Georg Held , Sandrine Heutz , Camille Petit The Journal Of Physical Chemistry C 55 DOI: 10.1021/acs.jpcc.4c02314 Diamond Proposal Number(s): [30777] Open Access	Jul 2024
I07-Surface & interface diffraction	Structure of the electrochemical interface: Ag(hkl) in an alkaline electrolyte Angeline Kasina , Elizabeth Cocklin , Sarah Horswell , Yvonne Grunder , Christopher A. Lucas The Journal Of Physical Chemistry C 9 DOI: 10.1021/acs.jpcc.4c03154 Diamond Proposal Number(s): [9653, 12715, 22272] Open Access Show Abstract ▼ Abstract: The structure of the electrochemical double layer at the interface between Ag(hkl) electrodes and 0.1 M NaOH electrolyte has been probed using in situ surface X-ray diffraction (SXRD) measurements. The three low-index Ag(hkl) surfaces were prepared and characterized under ultra-high vacuum (UHV) conditions before being transferred into the electrochemical environment. Crystal truncation rod (CTR) measurements were made at negative potentials (just negative of the pzc), where there is no specific adsorption onto the electrode surfaces, and at more positive potentials, where hydroxide species is specifically adsorbed. The measurements quantify the relaxation at the metal electrode surfaces and, through the specular CTR, give information about layering on the electrolyte side of the interface. Strong layering effects are observed on the Ag(111) and Ag(110) surfaces, whereas on Ag(001) the layering is much weaker and we attribute this to the symmetry mismatch to the adsorbing water network. The effect of saturating the electrolyte with carbon monoxide (CO) was also examined, and structural changes were only observed on the Ag(110) surface. The changes observed suggest a stabilization of a coadsorbed CO–OH adlayer due to charge redistribution that delays the onset of CO oxidation.	Jul 2024
I05-ARPES	Indium-doped crystals of SnSe2 Danrui Ni , Xianghan Xu , Zheyi Zhu , Yasemin Ozbek , Vesna Miksic Trontl , Chen Yang , Xiao Yang , Alex Louat , Cephise Cacho , Nai Phuan Ong , Pengpeng Zhang , Tonica Valla , Robert J. Cava The Journal Of Physical Chemistry C DOI: 10.1021/acs.jpcc.4c02926 Diamond Proposal Number(s): [36637] Show Abstract ▼ Abstract: Bulk crystals of undoped and In-doped (on the order of 1%) SnSe2 were synthesized using a solid-state temperature-gradient method and characterized by diffuse reflection, Raman scattering, ARPES and STM studies. An n-to-p crossover was observed as a function of the indium concentration in Hall measurements at 300 K, but the Seebeck coefficient is n-type at that temperature for all studied indium concentrations. The measured resistivity at 300 K reaches a maximum at the minimum carrier concentration. Our results suggest a multiband semiconducting nature for doped SnSe2, which provides insight into the exploration of enhanced thermoelectric performance and exotic electric behavior.	Jun 2024
I11-High Resolution Powder Diffraction	Mechanistic insights into Cs-ion exchange in the zeolite chabazite from in situ powder X-ray diffraction Daniel S. Parsons , Antony Nearchou , Ben L. Griffiths , Sharon E. Ashbrook , Joseph A. Hriljac The Journal Of Physical Chemistry C DOI: 10.1021/acs.jpcc.4c02145 Diamond Proposal Number(s): [26242, 33971] Open Access Show Abstract ▼ Abstract: Zeolites contain extraframework cations that are exchangeable under favorable aqueous conditions; this is the fundamental feature for their application in water purification and necessary to produce cation forms for other applications such as catalysis. Optimization of the process is common, but there is little fundamental understanding based on real-time experiments of the mechanism of exchange for most zeolites. The sodium and potassium forms of zeolite chabazite selectively uptake Cs+ by ion exchange, leading to its application in removing radioactive 137Cs+ from industrial nuclear waste streams, as well as from contaminated environments in the aftermath of the Fukushima and Three Mile Island accidents. In this study, in situ synchrotron powder X-ray diffraction patterns have been collected on chabazite as it undergoes Cs-ion exchange. Applying Rietveld refinement to these patterns has revealed the time-resolved structural changes that occur in the zeolite as exchange progresses, charting the changes in the spatial distribution of the extraframework cations and water molecules in the structure during the reaction. Ultimately, a detailed mechanistic understanding of how this dynamic ion-exchange reaction occurs has been obtained.	May 2024
B07-C-Versatile Soft X-ray beamline: Ambient Pressure XPS and NEXAFS	Excited-state identification of a nickel-bipyridine photocatalyst by time-resolved X-ray absorption spectroscopy Rachel F. Wallick , Sagnik Chakrabarti , John H. Burke , Richard Gnewkow , Ju Byeong Chae , Thomas C. Rossi , Ioanna Mantouvalou , Birgit Kanngießer , Mattis Fondell , Sebastian Eckert , Conner Dykstra , Laura E. Smith , Josh Vura-Weis , Liviu M. Mirica , Renske M. Van Der Veen The Journal Of Physical Chemistry Letters DOI: 10.1021/acs.jpclett.4c00226 Diamond Proposal Number(s): [31118] Open Access Show Abstract ▼ Abstract: Photoassisted catalysis using Ni complexes is an emerging field for cross-coupling reactions in organic synthesis. However, the mechanism by which light enables and enhances the reactivity of these complexes often remains elusive. Although optical techniques have been widely used to study the ground and excited states of photocatalysts, they lack the specificity to interrogate the electronic and structural changes at specific atoms. Herein, we report metal-specific studies using transient Ni L- and K-edge X-ray absorption spectroscopy of a prototypical Ni photocatalyst, (dtbbpy)Ni(o-tol)Cl (dtb = 4,4′-di-tert-butyl, bpy = bipyridine, o-tol = ortho-tolyl), in solution. We unambiguously confirm via direct experimental evidence that the long-lived (∼5 ns) excited state is a tetrahedral metal-centered triplet state. These results demonstrate the power of ultrafast X-ray spectroscopies to unambiguously elucidate the nature of excited states in important transition-metal-based photocatalytic systems.	May 2024
I07-Surface & interface diffraction	Optical absorption properties in pentacene/tetracene solid solutions Frederik Unger , Daniel Lepple , Maximilian Asbach , Luca Craciunescu , Clemens Zeiser , Andreas F. Kandolf , Zbyněk Fišer , Jakub Hagara , Jan Hagenlocher , Stefan Hiller , Sara Haug , Marian Deutsch , Peter Grüninger , Jiri Novacek , Holger F. Bettinger , Katharina Broch , Bernd Engels , Frank Schreiber The Journal Of Physical Chemistry A DOI: 10.1021/acs.jpca.3c06737 Diamond Proposal Number(s): [21899] Show Abstract ▼ Abstract: Modifying the optical and electronic properties of crystalline organic thin films is of great interest for improving the performance of modern organic semiconductor devices. Therein, the statistical mixing of molecules to form a solid solution provides an opportunity to fine-tune optical and electronic properties. Unfortunately, the diversity of intermolecular interactions renders mixed organic crystals highly complex, and a holistic picture is still lacking. Here, we report a study of the optical absorption properties in solid solutions of pentacene and tetracene, two prototypical organic semiconductors. In the mixtures, the optical properties can be continuously modified by statistical mixing at the molecular level. Comparison with time-dependent density functional theory calculations on occupationally disordered clusters unravels the electronic origin of the low energy optical transitions. The disorder partially relaxes the selection rules, leading to additional optical transitions that manifest as optical broadening. Furthermore, the contribution of diabatic charge-transfer states is modified in the mixtures, reducing the observed splitting in the 0–0 vibronic transition. Additional comparisons with other blended systems generalize our results and indicate that changes in the polarizability of the molecular environment in organic thin-film blends induce shifts in the absorption spectrum.	Jan 2024
I09-Surface and Interface Structural Analysis	Core-level binding energy shifts in ultrathin alkali-halide films on metals: KCl on Ag(100) Séverine Le Moal , Ina Krieger , Roman Kremring , Simon Weiss , Xiaosheng Yang , Serguei Soubatch , F. Stefan Tautz , Mathieu Silly , Andrei G. Borisov , Moritz Sokolowski , Eric Le Moal The Journal Of Physical Chemistry C 7 DOI: 10.1021/acs.jpcc.3c06302 Diamond Proposal Number(s): [14878] Show Abstract ▼ Abstract: We present an experimental and theoretical analysis of the core-level binding energy shifts in metal-supported ultrathin potassium chloride (KCl) films, i.e., a case from a broader class of few-atom-thick, wide-band gap insulating layers that is increasingly used in nanosciences and nanotechnologies. Using synchrotron-based high-resolution photoemission spectroscopy (HRPES) measurements, we identify the different contributions to the core-level binding energy shifts for the Cl– anions and K+ cations of two to three atomic layer-thick KCl films grown on Ag(100). The distances of the Cl– and K+ ions of the first two atomic layers of the KCl film from the metal substrate are determined from normal incidence X-ray standing wave measurements. We also calculated the core-level binding energy shifts using an analytical electrostatic model and found that the theoretical results are in agreement with the experimental HRPES results only when polarization and substrate-induced image charge effects are taken into account. Finally, our results evidence the effect of the third atomic layer of the KCl film, which partially covers and screens the first two atomic layers of KCl, wetting the metal substrate.	Dec 2023

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