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Journal of Physical Chemistry Letters

Sang Beom Kim, Evan M Sparano, Rakesh S Singh, Pablo G Debenedetti
Despite the importance of water sorption isotherms for a fundamental understanding of protein-water interactions, the microscopic origin of hysteresis between the adsorption and desorption branches is not well understood. Using our recently developed simulation technique, we compute the water sorption isotherms of two proteins, lysozyme and Trp-cage, a miniprotein. We explicitly compare protein-water interactions in adsorption and desorption processes, by analyzing local hydration in terms of hydrogen bonding, water density, and solvent-accessible surface area...
February 24, 2017: Journal of Physical Chemistry Letters
Rosa B Hughes-Currie, Konstantin V Ivanovskikh, Jon-Paul R Wells, Michael F Reid, Robert A Gordon, Luis Seijo, Zoila Barandiaran
Materials that luminesce after excitation with ionizing radiation are extensively applied in physics, medicine, security, and industry. Lanthanide dopants are known to trigger crystals scintillation through their fast d-f emissions; the same is true for other important applications as lasers or phosphors for lighting. However, this ability can be seriously compromised by unwanted anomalous emissions often found with the most common lanthanide activators. We report high resolution X-ray excited optical (IR to UV) luminescence spectra of CaF2:Yb and SrF2:Yb samples excited at 8949 eV and 80 K...
February 24, 2017: Journal of Physical Chemistry Letters
David M Black, Christopher M Crittenden, Jennifer S Brodbelt, Robert L Whetten
Here we report the first results of ultraviolet photodissociation (UVPD) mass spectrometry of trapped monolayer protected cluster (MPC) ions generated by electrospray ionization. Gold clusters Au25(pMBA)18 and Au36(pMBA)24 (pMBA = para-mercaptobenzoic acid), were analyzed in both the positive and negative modes. Whereas activation methods including collisional- and electron-based methods produced relatively few fragment ions, even a single ultraviolet pulse (at λ = 193 nm) caused extensive fragmentation of the positively charged clusters...
February 24, 2017: Journal of Physical Chemistry Letters
Shoichi Matsuda, Yoshimi Kubo, Kohei Uosaki, Shuji Nakanishi
Lithium-oxygen system has attracted much attention as a battery with high energy density that could satisfy the demands for electric vehicles. However, because lithium peroxide (Li2O2) is formed as an insoluble and insulative discharge product at the positive electrode, Li-O2 batteries have poor energy capacities. Although Li2O2 deposition on the positive electrode can be avoided by inducing solution-route pathway using electrolytes composed of high donor number (DN) solvents, such systems generally have poor stability...
February 24, 2017: Journal of Physical Chemistry Letters
Olga Russina, Fabrizio Lo Celso, Natalia V Plechkova, Alessandro Triolo
Ionic Liquids (IL) represent a blooming class of advanced materials continuously developing, aiming to the greening of chemical industry. Their appealing physical and chemical properties are largely influenced by their micro- and mesoscopic structure that is known to possess a high degree of hierarchical structuring. High-impact application fields are largely affected by the complex morphology of neat ionic liquids and their mixtures. This Perspective highlights new arising research directions that point out to an enhanced level of structural complexity in several IL-based systems, including mixtures...
February 24, 2017: Journal of Physical Chemistry Letters
Samira Siahrostami, Guo-Ling Li, Venkatasubramanian Viswanathan, Jens K Norskov
Electrochemical or photo-electrochemcial oxidation of water to form hydrogen peroxide (H2O2) or hydroxide radicals (•OH) offers a very attractive route to water disinfection, and the first process could be the basis for a clean way to produce hydrogen peroxide. A major obstacle in the development of effective catalysts for these reactions is that the electrocatalyst must suppress the thermodynamically favored four-electron pathway leading to O2 evolution. We develop a thermochemical picture of the catalyst properties that determine selectivity towards the one, two, and four electron processes leading to •OH, H2O2, and O2...
February 23, 2017: Journal of Physical Chemistry Letters
Imanol Usabiaga, Jorge González, Iker León, Pedro Felipe Arnaiz, Emilio J Cocinero, Jose A Fernandez
Carbohydrates are together with amino acids, DNA bases and lipids the building blocks of living beings. They play a central role in basic functions as immunity and signaling, which are governed by non-covalent interactions between sugar units and/or with other biomolecules. To get insights on such interactions between monosaccharide units, we used a combination of mass-resolved laser spectroscopy in supersonic expansions and molecular structure calculations. The results obtained clearly demonstrate that the small stability difference between the α/β anomers of glucopyranose derivatives is reversed and amplified during molecular aggregation, making the complexes of the β-anomers significantly more stable...
February 23, 2017: Journal of Physical Chemistry Letters
Stefanie A Mewes, Felix Plasser, Andreas Dreuw
The exciton size of the lowest singlet excited state in a diverse set of organic π-conjugated polymers is studied and found to be a universal, system-independent quantity of approximately 7 Å in the single chain picture. With time-dependent density functional theory (TDDFT), its value as well as the overall description of the exciton is almost exclusively governed by the amount of non-local orbital exchange. This is traced back to the lack of the Coulomb attraction between the electron and hole quasiparticles in pure TDDFT, which is reintroduced only with the admixture of non-local orbital exchange...
February 23, 2017: Journal of Physical Chemistry Letters
Sergey N Filimonov, Wei Liu, Alexandre Tkatchenko
The design of novel elementary surface processes is important for applications in catalysis, single-molecule junctions, molecular sensors, switches and surface mounted molecular machines. Here we demonstrate by van der Waals inclusive density functional theory calculations that a small and relatively simple heteroaromatic compound s-triazine (C$_3$H$_3$N$_3$) unexpectedly possesses five metastable states when adsorbed on the Pt(111) surface. This diversity of the adsorption states stems from an interplay between versatile molecule/surface chemical bonding and van der Waals interactions and from ``softening'' of the aromatic ring by nitrogen substitution, which makes folding of the aromatic ring energetically much less demanding as compared to benzene...
February 23, 2017: Journal of Physical Chemistry Letters
Olga A Syzgantseva, Michael Saliba, Michael Grätzel, Ursula Rothlisberger
In this work we perform a computational study comparing the influence of monovalent cation substitution by methylammonium (MA+), cesium (Cs+) and rubidium (Rb+) on the properties of formamidinium lead triiodide (FAPbI3)-based perovskites. The relative stability of the desired, photoactive perovskite α phase ("black phase") and the non-photoactive, non-perovskite δ phase ("yellow phase") is studied as a function of dopant nature, concentration and temperature. Cs+ and Rb+ are shown to be more efficient in the stabilization of the perovskite α phase than MA+...
February 23, 2017: Journal of Physical Chemistry Letters
Jing Li, Laihao Luo, Hongwen Huang, Chao Ma, Zhizhen Ye, Jie Zeng, Haiping He
Fundamental to understanding and predicting the optoelectronic properties of semiconductors is the basic parameters of excitons such as oscillator strength and exciton binding energy. However, such knowledge of CsPbBr3 perovskite, a promising optoelectronic material, is still unexplored. Here we demonstrate that quasi-two-dimensional (quasi-2D) CsPbBr3 nanoplatelets (NPLs) with 2D exciton behaviors serve as an ideal system for the determination of these parameters. It is found that the oscillator strength of CsPbBr3 NPLs is up to 1...
February 23, 2017: Journal of Physical Chemistry Letters
Marc Widdrat, Emanuel Schneck, Victoria Reichel, Jens Baumgartner, Luca Bertinetti, Wouter Habraken, Klaas Bente, Peter Fratzl, Damien Faivre
It is now recognized that nucleation and growth of crystals can occur not only by the addition of solvated ions but also by accretion of nanoparticles, in a process called nonclassical crystallization. The theoretical framework of such processes has only started to be described, partly due to the lack of kinetic or thermodynamic data. Here, we study the growth of magnetite nanoparticles from primary particles-nanometer-sized amorphous iron-rich precursors-in aqueous solution at different temperatures. We propose a theoretical framework to describe the growth of the nanoparticles and model both a diffusion-limited and a reaction-limited pathway to determine which of these best describes the rate-limiting step of the process...
February 23, 2017: Journal of Physical Chemistry Letters
Benjamin May, Michael Hönle, Bettina Heller, Francesco Greco, Radha Bhuin, Hans-Peter Steinrück, Florian Maier
We demonstrate that a thermodynamic complex equilibrium within an ionic liquid film can be significantly influenced by the presence of the liquid-vacuum interface. Using surface-sensitive X-ray photoelectron spectroscopy, we find that the temperature-driven transition from the blue-colored tetrahedral [Co(II) (NCS)4](2-) to the red-colored octahedral [Co(II) (NCS)6](4-) complex already occurs within the outermost nanometers at around +4 °C as compared with -25 °C in the bulk. This thermochromic transformation in the near-surface region goes along with a loss in preferential surface orientation of free [SCN](-) anions and with a pronounced decrease in the complex density; both effects are attributed to the formation of a weakly bound solvation shell around the [Co(II) (NCS)6](4-) anion, leading to an effective complex dilution...
February 23, 2017: Journal of Physical Chemistry Letters
Yi-Fan Huang, Marc T M Koper
In order to understand the interaction between Pt and surface oxygenated species in electrocatalysis, this paper correlates the electrochemistry of atomic oxygen on Pt formed in the gas phase with electrochemically generated oxygen species, on a variety of single-crystal platinum surfaces. The atomic oxygen adsorbed on single crystalline Pt electrodes, made by thermal dissociation of molecular oxygen, are used for voltammetry measurements in acidic electrolytes (HClO4 and H2SO4). The essential knowledge of coverage, binding energy and surface construction of atomic oxygen is correlated with the charge, potential and shape of voltammograms, respectively...
February 22, 2017: Journal of Physical Chemistry Letters
Galen C O'Neil, Luis Miaja-Avila, Young Il Joe, Bradley K Alpert, Mahalingam Balasubramanian, D M Sagar, William Doriese, Joseph W Fowler, Wilfred K Fullagar, Ning Chen, Gene C Hilton, Ralph Jimenez, Bruce Ravel, Carl D Reintsema, Dan R Schmidt, Kevin L Silverman, Daniel S Swetz, Jens Uhlig, Joel N Ullom
The detailed pathways of photoactivity on ultrafast time scales are a topic of contemporary interest. Using a tabletop apparatus based on a laser plasma X-ray source and an array of cryogenic microcalorimeter X-ray detectors, we measured a transient X-ray absorption spectrum during the ferrioxalate photoreduction reaction. With these high-efficiency detectors, we observe the Fe K edge move to lower energies and the amplitude of the extended X-ray absorption fine structure reduce, consistent with a photoreduction mechanism in which electron transfer precedes disassociation...
February 22, 2017: Journal of Physical Chemistry Letters
Vladimir Toshchevikov, Jaroslav Ilnytskyi, Marina Saphiannikova
Kinetics of photoisomerization and time evolution of ordering in azobenzene-containing materials are studied theoretically and by using computer simulations. Starting from kinetic equations of photoisomerization, we show that the influence of light is equivalent to the action of the effective potential, which reorients chromophores perpendicularly to polarization direction. The strength of the potential is defined by optical and viscous characteristics of the material. The potential generates photomechanical stress of giant values ∼GPa, in accordance with recent experimental findings for azobenzene materials deep in a glassy state...
February 22, 2017: Journal of Physical Chemistry Letters
Jinyu Li, Wenping Lyu, Giulia Rossetti, Albert Konijnenberg, Antonino Natalello, Emiliano Ippoliti, Modesto Orozco, Frank Sobott, Rita Grandori, Paolo Carloni
Native electrospray ionization/ion mobility-mass spectrometry (ESI/IM-MS) allows an accurate determination of low-resolution structural features of proteins. Yet, the presence of proton dynamics, observed already by us for DNA in the gas phase, and its impact on protein structural determinants, have not been investigated so far. Here, we address this issue by a multistep simulation strategy on a pharmacologically relevant peptide, the N-terminal residues of amyloid-β peptide (Aβ(1-16)). Our calculations reproduce the experimental maximum charge state from ESI-MS and are also in fair agreement with collision cross section (CCS) data measured here by ESI/IM-MS...
February 22, 2017: Journal of Physical Chemistry Letters
Philipp Consentius, Bernhard Loll, Ulrich Gohlke, Claudia Alings, Carsten Mueller, Robert Müller, Christian Teutloff, Udo Heinemann, Martin Kaupp, Markus C Wahl, Thomas Risse
Site-directed spin labeling is a versatile tool to study structure as well as dynamics of proteins using EPR spectroscopy. Methanethiosulfonate (MTS)-spin labels tethered through a disulfide linkage to an engineered cysteine residue were used in a large number of studies to extract structural as well as dynamic information of the protein from the rotational dynamics of the nitroxide moiety. The ring itself was always considered to be a rigid body. In this contribution, we present a combination of high-resolution X-ray crystallography and EPR spectroscopy of spin-labeled protein single crystals demonstrating that the nitroxide ring inverts fast at ambient temperature, while being characterized by a bent conformation at low temperature...
February 21, 2017: Journal of Physical Chemistry Letters
Azat F Akbulatov, Sergey Yurevich Luchkin, Lyubov A Frolova, Nadezhda N Dremova, Ivan S Zhidkov, Kirill L Gerasimov, Denis V Anokhin, Ernst Z Kurmaev, Keith J Stevenson, Pavel A Troshin
We report a careful and systematic study of the thermal and photochemical degradation of a series of complex haloplumbates APbX3 (X=I, Br) with hybrid organic (A+= CH3NH3) and inorganic (A+=Cs+) cations under anoxic conditions (i.e., without exposure to oxygen and moisture by testing in an inert glove box environment). We show that the most common hybrid materials (e.g. MAPbI3) are intrinsically unstable with respect to the heat- and light-induced stress and, therefore, can hardly sustain the real solar cell operation conditions...
February 21, 2017: Journal of Physical Chemistry Letters
Christian Wiebeler, Felix Plasser, Gordon J Hedley, Arvydas Ruseckas, Ifor D W Samuel, Stefan Schumacher
Understanding electronic energy transfer (EET) is an important ingredient in the development of artificial photosynthetic systems and photovoltaic technologies. Although EET is at the heart of these applications and crucially influences their light-harvesting efficiency, the nature of EET over short distances for covalently bound donor and acceptor units is often not well understood. Here we investigate EET in an orthogonal molecular dyad (BODT4), in which simple models fail to explain the very origin of EET...
February 21, 2017: Journal of Physical Chemistry Letters
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