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Journal of Physical Chemistry Letters

Hari Vignesh Ramasamy, Karthikeyan Kaliyappan, Ranjith Thangavel, Won Mo Seong, Kisuk Kang, Zhongwei Chen, Yun-Sung Lee
Despite their high specific capacity, sodium layered oxides suffer from severe capacity fading when cycled at higher voltages. This key issue must be addressed in order to develop high-performance cathodes for sodium ion batteries (SIBs). Herein, we present a comprehensive study on the influence of Al doping of Mn sites on the structural and electrochemical properties of a P2-Na0.5Mn0.5-xAlxCo0.5O2 (x = 0, 0.02, or 0.05) cathode for SIBs. Detailed structural, morphological, and electrochemical investigations were carried out using X-ray diffraction, cyclic voltammetry, and galvanostatic charge-discharge measurements and some new insights are proposed...
September 15, 2017: Journal of Physical Chemistry Letters
Adam Grofe, Xin Chen, Wenjian Liu, Jiali Gao
Kohn-Sham Density functional theory has been tremendously successful in chemistry and physics. Yet, it is unable to describe the energy degeneracy of spin-multiplet components with any approximate functional. This work features two contributions. (1) We present a multistate density functional theory (MSDFT) to represent spin-multiplet components and to determine multiplet energies. MSDFT is a hybrid approach, taking advantage of both wave function theory and density functional theory. Thus, the wave functions, electron densities and energies for ground and excited states and for different components are treated on the same footing...
September 15, 2017: Journal of Physical Chemistry Letters
Xue-Feng Peng, Xiao-Yan Wu, Xia-Xia Ji, Jie Ren, Qi Wang, Guo-Qing Li, Xiao-Hui Yang
Modification of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) with sodium-poly(styrenesulfonate) leads to a ca. 0.3 eV increase in the work function and 15 times enhancement in the photoluminescence intensity of the overlying perovskite layer, which is closely correlated with the formation of a highly PSS-enriched top layer. As a direct result, the hybrid halide perovskite light-emitting devices with a modified PEDOT:PSS layer show the maximum external quantum efficiency of 7.2% and power efficiency of 19...
September 15, 2017: Journal of Physical Chemistry Letters
Heeseon Lim, Hyuksang Kwon, Sang Kyu Kim, Jeong Won Kim
Light absorption in organic molecules on an inorganic substrate and subsequent electron transfer to the substrate create so-called hybrid charge transfer exciton (HCTE). The relaxation process of the HCTE states largely determines charge separation efficiency or optoelectronic device performance. Here, the study on energy and time-dispersive behavior of photoelectrons at the hybrid interface of copper phthalocyanine (CuPc)/p-GaAs(001) upon light excitation of GaAs reveals a clear pathway for HCTE relaxation and delayed triplet formation...
September 15, 2017: Journal of Physical Chemistry Letters
Nandakumar Rajasekaran, Ashok Sekhar, Athi N Naganathan
Understanding the extent to which information is transmitted through the intra-molecular interaction network of proteins upon a perturbation, i.e. an allosteric effect, has long remained an unsolved problem. Through an analysis of high-resolution NMR data from the literature on 28 different proteins and 49 structural perturbations, we show that the extent of induced structural changes through mutations, and molecular events including protein-protein, protein-peptide, protein-ligand binding and post-translational modifications exhibit a near-universal exponential functional form...
September 14, 2017: Journal of Physical Chemistry Letters
Thiago Martins Francisco, William J Gee, Helena J Shepherd, Mark R Warren, David A Shultz, Paul R Raithby, Carlos B Pinheiro
The valence tautomeric interconversion (VTI) is a reversible process occurring in metal complexes in which an intramolecular metal-ligand electron transfer is accompanied by a change of metal ion spin state creating two switchable electronic states (redox isomers). Herein, we describe the low temperature, 30 - 100 K, single-crystal study of the [Co(diox)2(4-CN-py)2]·benzene complex (1) (diox = 3,5-di-t-butylsemiquinonate (SQ(•-)) and/or 3,5-di-t-butylcatecholate (Cat(2-)) radical; 4-CN-py = 4-cyano-pyridine) using hard synchrotron X-ray radiation with different intensities...
September 14, 2017: Journal of Physical Chemistry Letters
Roland Jung, Michael Metzger, Filippo Maglia, Christoph Stinner, Hubert Gasteiger
In this study, we compare the stability of alkyl carbonate electrolyte on NMC111, 622, 811, LNMO, and conductive carbon electrodes. We prove that CO2 and CO evolution onset potentials depend on the electrode material and increase in the order NMC811 < NMC111 ≈ NMC622 < conductive carbon ≈ LNMO, which we rationalize by two fundamentally different oxidation mechanisms, the chemical and the electrochemical electrolyte oxidation. Additionally, in contrast to the widespread understanding that transition metals in cathode active materials catalyze the electrolyte oxidation, we will prove that such a catalytic effect on the electrochemical electrolyte oxidation does not exist...
September 14, 2017: Journal of Physical Chemistry Letters
Felix Hoffmann, Juliane Adler, Bappaditya Chandra, Kaustubh R Mote, Gül Bekcioglu-Neff, Daniel Sebastiani, Daniel Huster
We explored structural details of fibrils formed by a mutated amyloid β (Aβ(1-40) peptide carrying a Phe19 to Lys19 mutation, which was shown to completely abolish the toxicity of the molecule. Computer models suggest that the positively charged Lys19 side-chain is expelled from the hydrophobic fibril interior upon fibrillation. This can be accommodated by either a 180° flip of the entire lower β-strand (model M1) or local perturbations of the secondary structure in the direct vicinity of the mutated site (model M2)...
September 14, 2017: Journal of Physical Chemistry Letters
Ferruccio Palazzesi, Omar Valsson, Michele Parrinello
Many enhanced sampling methods rely on the identification of appropriate collective variables. For proteins, even small ones, finding appropriate descriptors has proven challenging. Here we suggest that the NMR S(2) order parameter can be used to this effect. We trace the validity of this statement to the suggested relation between S(2) and conformational entropy. Using the S(2) order parameter and a surrogate for the protein enthalpy in conjunction with Metadynamics or Variationally Enhanced Sampling we are able to reversibly fold and unfold a small protein and draw its free energy at a fraction of the time that is needed in unbiased simulations...
September 14, 2017: Journal of Physical Chemistry Letters
Liudmila G Kudriashova, David Kiermasch, Philipp Rieder, Marshall Campbell, Kristofer Tvingstedt, Andreas Baumann, Georgy V Astakhov, Vladimir Dyakonov
We studied charge carrier recombination in methylammonium lead iodide (MAPbI3) perovskite and the impact of interfaces on the charge carrier lifetime using time-resolved photoluminescence. Pristine films and those covered with organic electron and hole transport materials (TMs) were investigated at various laser repetition rates ranging from 10 kHz to 10 MHz in order to separate the bulk and interface-affected recombination. We revealed two different components in the PL decay. The fast component (shorter than 300 ns) is assigned to interfacial processes, and the slow one to bulk recombination...
September 14, 2017: Journal of Physical Chemistry Letters
Christian J Burnham, Niall J English
An extensive suite of nonequilibrium molecular-dynamics (NEMD) simulations have been performed for ∼60 ns of human aquaporin 4 in externally applied circularly polarized (CP) electric fields, applied axially along channels. These external fields were 0.05 V/Å in intensity and 100 GHz in frequency. This has the effect of "electro-pumping" the water through the pores as prototypical biochannels, from conversion of molecules' spin angular momentum to linear momentum in the asymmetric heterogeneous-frictional environment of the pores, thus inducing overall net flow...
September 14, 2017: Journal of Physical Chemistry Letters
Ruo Xi Yang, Jonathan M Skelton, Lora da Silva, Jarvist M Frost, Aron Walsh
The local crystal structures of many perovskite-structured materials deviate from the average space group symmetry. We demonstrate, from lattice-dynamics calculations based on quantum chemical force constants, that all the caesium-lead and caesium-tin halide perovskites exhibit vibrational instabilities associated with octahedral titling in their high-temperature cubic phase. Anharmonic double-well potentials are found for zone-boundary phonon modes in all compounds with barriers ranging from 108 to 512 meV...
September 14, 2017: Journal of Physical Chemistry Letters
Michihiro Nagao, Elizabeth G Kelley, Rana Ashkar, Robert Bradbury, Paul D Butler
The elastic and viscous properties of self-assembled amphiphilic membranes dictate the intricate hierarchy of their structure and dynamics ranging from the diffusion of individual molecules to the large-scale deformation of the membrane. We previously demonstrated that neutron spin echo spectroscopy measurements of model amphiphilic membranes can access the naturally occurring submicrosecond membrane motions, such as bending and thickness fluctuations. Here we show how the experimentally measured fluctuation parameters can be used to determine the inherent membrane properties and demonstrate how membrane viscosity and compressibility modulus are influenced by lipid composition in a series of simple phosphatidylcholine bilayers with different tail lengths as a function of temperature...
September 14, 2017: Journal of Physical Chemistry Letters
Daniele Fazzi, Mario Barbatti, Walter Thiel
The evolution of the excited-state manifold in organic D/A aggregates (e.g. the prototypical P3HT/PCBM) is investigated through a bottom-up approach via first-principles calculations. We show how the excited-state energies, the charge transfer (CT) states, and the electron-hole density distributions are strongly influenced by the size, the orientation and the position (i.e. on-top vs. on-edge phases) of P3HT/PCBM domains. We discuss how the structural order influences the excited-state electronic structure, providing an atomistic interpretation of the photophysics of organic blends...
September 13, 2017: Journal of Physical Chemistry Letters
Atul D Sontakke, Alban Ferrier, Pauline Burner, Vinicius Ferraz Guimarães, Mathieu Salaun, Vincent Maurel, Isabelle Gautier-Luneau, Alain Ibanez, Bruno Viana
Wet-chemically synthesized amorphous yttrium-aluminum-borates (a-YAB) exhibit intense visible photoluminescence (PL). Preliminary investigations revealed a correlation of PL with the presence of carbon-related impurities; however their exact nature is still under investigation. These powders also exhibit afterglow luminescence that lasts for several seconds at room-temperature (RT). A comparison with persistent phosphors and phosphorescent dye revealed that the afterglow in a-YAB is a phosphorescence phenomenon and not the persistence luminescence, which is more common in inorganic solids...
September 13, 2017: Journal of Physical Chemistry Letters
Tomoya Endo, Yoshiyuki Matsuda, Asuka Fujii
Infrared spectroscopy of the hydrated clusters of cationic pentane, which are generated through the vacuum ultraviolet photoionization in the gas phase, is carried out to probe the acidic properties of their CH bonds. The mono-hydrated pentane cation forms the proton-shared structure, in which the proton of CH in cationic pentane is shared between the pentyl radical and water molecule. In the di- and tri-hydrated clusters, the proton of CH is completely transferred to the water moiety, so that the clusters are composed of the pentyl radical and protonated water cluster...
September 13, 2017: Journal of Physical Chemistry Letters
Xiangrui Kong, Astrid Waldner, Fabrizio Orlando, Luca Artiglia, Thomas Huthwelker, Markus Ammann, Thorsten Bartels-Rausch
The interfacial ionization of strong acids is an essential factor of multi-phase and heterogeneous chemistry in environmental science, crysophereic science, catalysis research and material science. We investigate the mechanism of HCl dissociation at the ice surface using surface-sensitive ambient-pressure core level X-ray photoelectron spectroscopy. At 253 K and low surface coverage, adsorbed HCl is found in both states, molecular and dissociated. Depth profiles derived from XPS data clearly show that the dissociated acid is found deeper in the interfacial region compared to the molecular form...
September 13, 2017: Journal of Physical Chemistry Letters
Janus J Eriksen, Filippo Lipparini, Jürgen Gauss
It is demonstrated how full configuration interaction (FCI) results in extended basis sets may be obtained to within sub-kJ/mol accuracy by decomposing the energy in terms of many-body expansions in the virtual orbitals of the molecular system at hand. This extension of the FCI application range lends itself to two unique features of the current approach, namely, that the total energy calculation can be performed entirely within considerably reduced orbital subspaces and may be so by means of embarrassingly parallel programming...
September 13, 2017: Journal of Physical Chemistry Letters
Tibor Nagy, György Lendvay
An approximation-free adiabatic switching method to generate semiclassically quantized ensembles of rovibrational states of polyatomic molecules for use as initial conditions in quasiclassical trajectory calculations is presented. Vibrational states are prepared, starting from an ensemble of classical states corresponding to the desired quantum state of the normal-mode Hamiltonian by slowly switching on the anharmonicity in internal coordinates, thereby avoiding rotational contamination. To generate rovibrational states, an extension is proposed: The vibrationally quantized molecules are slowly spun up to the desired quantized angular momentum...
September 13, 2017: Journal of Physical Chemistry Letters
Woo Hyun Han, Sunghyun Kim, In-Ho Lee, Kee Joo Chang
Black phosphorus is an emerging material in nanoelectronics and nanophotonics due to its high carrier mobility and anisotropic in-plane properties. In addition, the polymorphism of phosphorus leads to numerous searches for new allotropes that are more attractive than black phosphorus in a variety of applications. On the basis of ab initio evolutionary crystal structure search computation, we report the prediction of a phosphorus allotrope called green phosphorus (λ-P), which exhibits direct band gaps ranging from 0...
September 13, 2017: Journal of Physical Chemistry Letters
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