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34 items found (0 items not approved), displaying 1 to 10.[First/Prev] 1, 2, 3, 4 [Next/Last]

Instruments / Technical Area	Publication Details	Published
	Experimental demonstration of a spectral fingerprint for the saddle and inverted conformations of porphyrins on copper Eleanor S. Frampton , Ailish Gray , Michael Clarke , Matthew Edmondson , Jonathan Bradford , David A. Duncan , Alex Saywell The Journal Of Physical Chemistry Letters DOI: 10.1021/acs.jpclett.5c00498 Open Access Show Abstract ▼ 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).	May 2025
I09-Surface and Interface Structural Analysis	d10s2 post-transition metal anions: identifying and analyzing their dual-mode Lewis basicity 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 The Journal Of Physical Chemistry Letters DOI: 10.1021/acs.jpclett.4c03649 Diamond Proposal Number(s): [20463] Open Access Show Abstract ▼ 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.	Mar 2025
I11-High Resolution Powder Diffraction	Metastable dihydrate of sodium chloride at ambient pressure Rachael Hamp , Christoph G. Salzmann , Zachary Amato , Milz L. Beaumont , Hannah E. Chinnery , Peter Fawdon , Thomas F. Headen , Paul F. Henry , Liam Perera , Stephen P. Thompson , Mark G. Fox-Powell The Journal Of Physical Chemistry Letters DOI: 10.1021/acs.jpclett.4c02752 Diamond Proposal Number(s): [36314] Open Access Show Abstract ▼ Abstract: Sodium chloride (NaCl) plays an important role in geochemistry, biology, industry, and food production, and it is among the most common salts in the solar system. Here, we report the discovery of a metastable NaCl dihydrate formed through rapid freezing (101–102 K s–1) of a NaCl solution at ambient pressure. Using synchrotron X-ray and neutron powder diffraction, we show that it transforms irreversibly to hydrohalite and ice Ih above 190 K upon heating and propose it is structurally related to hydrohalite with a 3 × 1 × 3 supercell as its unit cell. Calorimetric analyses reveal that the new hydrate transforms to hydrohalite with a heat release of −3.47 ± 0.55 kJ mol–1. The identification of this new NaCl dihydrate on the surfaces of icy worlds such as the moons of Jupiter and Saturn could indicate regions of recent activity where subsurface brines have frozen rapidly, priority targets for upcoming planetary missions.	Dec 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-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
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
B22-Multimode InfraRed imaging And Microspectroscopy	Vibrational modes and terahertz phenomena of the large-cage Zeolitic Imidazolate Framework-71 Annika F. Möslein , Jin-Chong Tan The Journal Of Physical Chemistry Letters DOI: 10.1021/acs.jpclett.2c00081 Diamond Proposal Number(s): [21472] Show Abstract ▼ Abstract: The zeolitic imidazole framework ZIF-71 has the potential to outperform other well-studied metal–organic frameworks due to its intrinsic hydrophobicity and relatively large pore size. However, a detailed description of its complex physical phenomena and structural dynamics has been lacking thus far. Herein, we report the complete assignment of the vibrational modes of ZIF-71 using high-resolution inelastic neutron scattering measurements and synchrotron radiation infrared spectroscopy, corroborated by density functional theory (DFT) calculations. With its 816 atoms per unit cell, ZIF-71 is the largest system yet for which frequency calculations have been accomplished employing the CRYSTAL17 DFT code. We discover low-energy terahertz dynamics such as gate-opening and shearing modes that are central to the functions and stability of the ZIF-71 framework structure. Nanoscale analytical methods based on atomic force microscopy (near-field infrared spectroscopy and AFM nanoindentation) further unravel the local chemical and mechanical properties of ZIF-71 single crystals.	Mar 2022
	Interface sensitivity in electron/ion yield X-ray absorption spectroscopy: The TiO2–H2O interface Matthijs A. Van Spronsen , Xiao Zhao , Maximilian Jaugstetter , Carlos Escudero , Tomas Duchon , Adrian Hunt , Iradwikanari Waluyo , Peidong Yang , Kristina Tschulik , Miquel B. Salmeron The Journal Of Physical Chemistry Letters DOI: 10.1021/acs.jpclett.1c02115 Open Access Show Abstract ▼ Abstract: To understand corrosion, energy storage, (electro)catalysis, etc., obtaining chemical information on the solid–liquid interface is crucial but remains extremely challenging. Here, X-ray absorption spectroscopy (XAS) is used to study the solid–liquid interface between TiO2 and H2O. A thin film (6.7 nm) of TiO2 is deposited on an X-ray-transparent SiNx window, acting as the working electrode in a three-electrode flow cell. The spectra are collected based on the electron emission resulting from the decay of the X-ray-induced core-hole-excited atoms, which we show is sensitive to the solid–liquid interface within a few nm. The drain currents measured at the working and counter electrodes are identical but of opposite sign. With this method, we found that the water layer next to anatase is spectroscopically similar to ice. This result highlights the potential of electron-yield XAS to obtain chemical and structural information with a high sensitivity for the species at the electrode–electrolyte interface.	Oct 2021
	Electronic structures and surface reconstructions in magnetic superconductor RbEuFe4As4 Vasily S. Stolyarov , Kirill S. Pervakov , Anna S. Astrakhantseva , Igor A. Golovchanskiy , Denis V. Vyalikh , Timur K. Kim , Sergey V. Eremeev , Vladimir A. Vlasenko , Vladimir M. Pudalov , Alexander A. Golubov , Eugene V. Chulkov , Dimitri Roditchev The Journal Of Physical Chemistry Letters DOI: 10.1021/acs.jpclett.0c02711 Show Abstract ▼ Abstract: In pnictide RbEuFe4As4, superconductivity sets in at 36 K and coexists, below 15–19 K, with the long-range magnetic ordering of Eu 4f spins. Here we report scanning tunneling experiments performed on cold-cleaved single crystals of the compound. The data revealed the coexistence of large Rb-terminated and small Eu-terminated terraces, both manifesting 1 × 2 and 2‾√×2‾√ 2 × 2 reconstructions. On 2‾√×2‾√ 2 × 2 surfaces, a hidden electronic order with a period ∼5 nm was discovered. A superconducting gap of ∼7 meV was seen to be strongly filled with quasiparticle states. The tunneling spectra compared with density functional theory calculations confirmed that flat electronic bands due to Eu 4f orbitals are situated ∼1.8 eV below the Fermi level and thus do not contribute directly to Cooper pair formation.	Oct 2020
E02-JEM ARM 300CF	Competitive nucleation mechanism for CsPbBr3 perovskite nanoplatelets growth Victor M. Burlakov , Yasser Hassan , Mohsen Danaie , Henry J. Snaith , Alain Goriely The Journal Of Physical Chemistry Letters DOI: 10.1021/acs.jpclett.0c01794 Diamond Proposal Number(s): [20564] Show Abstract ▼ Abstract: We analyse nucleation-controlled nanocrystal growth in a solution containing surface-binding molecular ligands, which can also nucleate compact layers on the crystal surfaces. We show that if the critical nucleus size for ligands is larger and the nucleation barrier is lower than those for crystal atoms, the ligands nucleate faster than the atoms on relatively wide crystal facets but much slower, if at all, on narrow facets. Such competitive nucleation of ligands and atoms results in ligands covering predominantly wider facets, thus excluding them from the growth process, and acts as a selection mechanism for the growth of crystals with narrower facets, the so-called nanoplatelets. The theory is confirmed by Monte Carlo simulations and validated experimentally for CsPbBr3 nanoplatelets grown from solution. We find that the anisotropic crystal growth is controlled by the growth temperature and the strength of surface bonding for the passivating molecular ligands.	Jul 2020

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