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Physical Chemistry Chemical Physics: PCCP

Han-Shi Hu, Nikolas Kaltsoyannis
Compounds featuring unsupported metal-metal bonds between actinide elements remain highly sought after yet confined experimentally to inert gas matrix studies. Notwithstanding this paucity, actinide-actinide bonding has been the subject of extensive computational research. In this contribution, high level quantum chemical calculations at both the scalar and spin-orbit levels are used to probe the Th-Th bonding in a range of zero valent systems of general formula LThThL. Several of these compounds have very short Th-Th bonds arising from a new type of Th-Th quadruple bond with a previously unreported electronic configuration featuring two unpaired electrons in 6d-based δ bonding orbitals...
January 18, 2017: Physical Chemistry Chemical Physics: PCCP
H Akbarzadeh, A N Shamkhali, E Mehrjouei
In this work, two probabilistic and thermodynamic limits for formation of a bimetallic nanocluster from a homogeneous gas phase were obtained in order to investigate the related phenomena using molecular dynamics simulation. Therefore, by application of some simple assumptions from thermodynamics and statistical mechanics, a new expression for composition of the nanocluster was derived which depends only on the initial conditions of the system and one adjustable parameter. This expression can be easily fitted to the results of molecular dynamics and can be used as a measure of the thermodynamic contribution in the cluster formation process...
January 18, 2017: Physical Chemistry Chemical Physics: PCCP
Bason Clancy, Joshua Salafsky
Second Harmonic Generation (SHG) has emerged as a highly sensitive probe of protein conformation. SHG can also be used to determine the tilt angle of an SHG-active moiety bound to a surface-adsorbed protein through polarization-dependent measurements. However, due to the coherent nature of SHG, interference occurs between the SHG produced by the SHG-active moieties and background sources at a solid-liquid interface, obscuring the signal of interest. In order to separate the protein-specific signal from the background signal, the phase difference between these two different sources of SHG must be determined...
January 18, 2017: Physical Chemistry Chemical Physics: PCCP
Eugene Heifets, Eugene A Kotomin, Alexander A Bagaturyants, Joachim Maier
BiFeO3 perovskite attracts great attention due to its multiferroic properties and potential use as a parent material for Bi1-xSrxFeO3-δ and Bi1-xSrxFe1-yCoyO3-δ solid solutions in intermediate temperature cathodes of oxide fuel cells. Another iron-based LaFeO3 perovskite is the end member for well-known solid solutions (La1-xSrxFe1-yCoyO3-δ) used for oxide fuel cells and other electrochemical devices. In this study an ab initio hybrid functional approach was used for the study of the thermodynamic stability of both LaFeO3 and BiFeO3 with respect to decompositions to binary oxides and to elements, as a function of temperature and oxygen pressure...
January 18, 2017: Physical Chemistry Chemical Physics: PCCP
L Pavasaryte, A Katelnikovas, V Klimavicius, V Balevicius, A Krajnc, G Mali, J Plavec, A Kareiva
Nd(3+)-Doped yttrium aluminium garnet and Eu(3+)-Nd(3+)-co-doped yttrium aluminium garnet were synthesized using an environmentally friendly sol-gel method at low temperatures. The results of X-ray diffraction (XRD) analysis of the powders sintered at 1000 °C showed the purity and formation of monophasic compounds. The phase composition and purity confirmation of the samples were also characterized via FTIR spectroscopy. Desirable microstructural features and particle size of phosphorous materials of the polycrystalline samples were studied via scanning electron microscopy (SEM)...
January 18, 2017: Physical Chemistry Chemical Physics: PCCP
Miguel A Soler, José Zúñiga, Alberto Requena, Adolfo Bastida
Despite the increasing evidence that conformational transitions in peptides and proteins are driven by specific vibrational energy pathways along the molecule, the current experimental techniques of analysis do as yet not allow to study these biophysical processes in terms of anisotropic energy flows. Computational methods offer a complementary approach to obtain a more detailed understanding of the vibrational and conformational dynamics of these systems. Accordingly, in this work we investigate jointly the vibrational energy distribution and the conformational dynamics of trialanine peptide in water solution at room temperature by applying the Instantaneous Normal Mode analysis to the results derived from equilibrium molecular dynamics simulations...
January 18, 2017: Physical Chemistry Chemical Physics: PCCP
G Kruthika, J Karthikeyan, P Murugan
By employing first principles density functional calculations, we investigated an α-MnO2 compound with a tunnel framework, which provides an eminent platform to alter the intrinsic antiferromagnetic (AFM) to ferromagnetic (FM) ordering, through the introduction of chemical or mechanical tensile strain. Our calculations further showed that the strength of FM ordering increases until 10% triaxial tensile strain. Since long range FM ordering is induced, it is realized to be superior as compared to the experimentally observed short-range FM ordering in oxygen-deficient compound...
January 18, 2017: Physical Chemistry Chemical Physics: PCCP
Eric Ganz, Ariel B Ganz, Li-Ming Yang, Matthew Dornfeld
Graphene and its analogues have some of the highest predicted melting points of any materials. Previous work estimated the melting temperature for freestanding graphene to be a remarkable 4510 K. However, this work relied on theoretical methods that do not accurately account for the role of bond breaking or complex bonding configurations in the melting process. Furthermore, experiments to verify these high melting points have been challenging. Practical applications of graphene and carbon nanotubes at high temperatures will require a detailed understanding of the behavior of these materials under these conditions...
January 18, 2017: Physical Chemistry Chemical Physics: PCCP
P Gast, D Mance, E Zurlo, K L Ivanov, M Baldus, M Huber
To understand the dynamic nuclear polarization (DNP) enhancements of biradical polarizing agents, the magnetic resonance parameters need to be known. We describe a tailored EPR approach to accurately determine electron spin-spin coupling parameters using a combination of standard (9 GHz), high (95 GHz) and ultra-high (275 GHz) frequency EPR. Comparing liquid- and frozen-solution continuous-wave EPR spectra provides accurate anisotropic dipolar interaction D and isotropic exchange interaction J parameters of the DNP biradical AMUPol...
January 18, 2017: Physical Chemistry Chemical Physics: PCCP
Zhanli Cao, Zhendong Li, Fan Wang, Wenjian Liu
The spin-separated exact two-component (X2C) relativistic Hamiltonian [sf-X2C+so-DKHn, J. Chem. Phys., 2012, 137, 154114] is combined with the equation-of-motion coupled-cluster method with singles and doubles (EOM-CCSD) for the treatment of spin-orbit splittings of open-shell molecular systems. Scalar relativistic effects are treated to infinite order from the outset via the spin-free part of the X2C Hamiltonian (sf-X2C), whereas the spin-orbit couplings (SOC) are handled at the CC level via the first-order Douglas-Kroll-Hess (DKH) type of spin-orbit operator (so-DKH1)...
January 18, 2017: Physical Chemistry Chemical Physics: PCCP
Shuixing Li, Zhongqiang Zhang, Minmin Shi, Chang-Zhi Li, Hongzheng Chen
Nowadays, organic solar cells (OSCs) with efficiencies over 10% have been achieved through the elaborate design of electron donors and fullerene acceptors. However, the drawbacks of fullerene acceptors, like poor absorption, limited chemical and energetic tunabilities, high-cost purification and morphological instability, have become the bottlenecks for the further improvement of OSCs. To overcome the mentioned shortages from fullerene, research studies on non-fullerene electron acceptors have boomed. To date, the highest efficiency of fullerene-free OSCs has been pushed to be 12%, which surpasses that of fullerene-based OSCs...
January 17, 2017: Physical Chemistry Chemical Physics: PCCP
Allegra A Latimer, Hassan Aljama, Arvin Kakekhani, Jong Suk Yoo, Ambarish Kulkarni, Charlie Tsai, Max Garcia-Melchor, Frank Abild-Pedersen, Jens K Nørskov
While natural gas is an abundant chemical fuel, its low volumetric energy density has prompted a search for catalysts able to transform methane into more useful chemicals. This search has often been aided through the use of transition state (TS) scaling relationships, which estimate methane activation TS energies as a linear function of a more easily calculated descriptor, such as final state energy, thus avoiding tedious TS energy calculations. It has been shown that methane can be activated via a radical or surface-stabilized pathway, both of which possess a unique TS scaling relationship...
January 17, 2017: Physical Chemistry Chemical Physics: PCCP
Rocío Domínguez, Núria F Montcada, Pilar de la Cruz, Emilio Palomares, Fernando Langa
Two new planar and symmetrical A-D-A (electron acceptor-electron donor-electron acceptor) small molecules based on a commercial cyclopentadithiophene derivative have been synthesized for solution processed small molecule organic solar cells. The aim was to synthesise the molecules to be energetically identical (similar HOMO-LUMO energy levels) in order to assign the differences observed to changes in the film morphology or to differences in the interfacial recombination kinetics or both. Devices were electrically characterized under one sun simulated (1...
January 17, 2017: Physical Chemistry Chemical Physics: PCCP
Natasha W Pettinger, Robert E A Williams, Jinquan Chen, Bern Kohler
A stable sol of cerium oxide nanoparticles forms spontaneously when cerium(iv) ammonium nitrate (CAN) is dissolved in room-temperature water at mM concentrations. Electron microscopy experiments reveal the formation of highly crystalline cerium oxide particles several nm in diameter and suggest that they are formed from amorphous particles that are similar in size. Under the low pH conditions of the experiments, the nanoparticles form a stable dispersion and show no evidence of aggregation, even many months after synthesis...
January 17, 2017: Physical Chemistry Chemical Physics: PCCP
Steffen Büning, Abhishek Sharma, Shivang Vachharajani, Estella Newcombe, Angelique Ormsby, Mimi Gao, David Gnutt, Tobias Vöpel, Danny M Hatters, Simon Ebbinghaus
Huntington's disease is caused by a CAG trinucleotide expansion mutation in the Huntingtin gene that leads to an artificially long polyglutamine sequence in the Huntingtin protein. A key feature of the disease is the intracellular aggregation of the Huntingtin exon 1 protein (Httex1) into micrometer sized inclusion bodies. The aggregation process of Httex1 has been extensively studied in vitro, however, the crucial early events of nucleation and aggregation in the cell remain elusive. Here, we studied the conformational dynamics and self-association of Httex1 by in-cell experiments using laser-induced temperature jumps and analytical ultracentrifugation...
January 17, 2017: Physical Chemistry Chemical Physics: PCCP
Weitao Fu, Lingfeng Chen, Zhe Wang, Yanting Kang, Chao Wu, Qinqin Xia, Zhiguo Liu, Jianmin Zhou, Guang Liang, Yuepiao Cai
The activation and overexpression of fibroblast growth factor receptors (FGFRs) are highly correlated with a variety of cancers. Most small molecule inhibitors of FGFRs selectively target FGFR1-3, but not FGFR4. Hence, designing highly selective inhibitors towards FGFR4 remains a great challenge because FGFR4 and FGFR1 have a high sequence identity. Recently, two small molecule inhibitors of FGFRs, ponatinib and AZD4547, have attracted huge attention. Ponatinib, a type II inhibitor, has high affinity towards FGFR1/4 isoforms, but AZD4547, a type I inhibitor of FGFR1, displays much reduced inhibition toward FGFR4...
January 17, 2017: Physical Chemistry Chemical Physics: PCCP
Yao Liu, Martin R Ward, Andrew J Alexander
In a seminal report on laser-induced nucleation in aqueous supersaturated solutions (Phys. Rev. Lett., 1996, 77, 3475) it was noted that needle-shaped crystals of urea were aligned with the direction of the electric field of the linearly polarized laser pulse. The results gave rise to a new mechanism for control of crystal nucleation involving alignment of solute molecules (optical Kerr effect) now commonly known as non-photochemical laser-induced nucleation (NPLIN). Recent theoretical and experimental work has cast doubts on the optical Kerr effect mechanism...
January 17, 2017: Physical Chemistry Chemical Physics: PCCP
Rui Xia, Xingzhong Cao, Meizhen Gao, Peng Zhang, Minfeng Zeng, Baoyi Wang, Long Wei
Chitosan, CS, cross-linked with bivalent palladium has shown enhanced mechanical and thermal properties depending on the transformation of the structure at a microscopic scale. In the present study, CS directly cross-linked by palladium cation membranes (CS-cr-PM) was prepared through a solution-casting method. Mobility of chitosan chains were greatly reduced after crosslinking, making a great reduction in the swelling ratio studied by a water-swelling degree measurement, which led to an improvement in molecular chain rigidity...
January 17, 2017: Physical Chemistry Chemical Physics: PCCP
Tao Yang, Masahiro Ehara
The electronic structure of the oxide-supported nanoclusters based on metal-support interactions including charge and spin reorganization plays a crucial role in the catalytic activity at the interface region. In this work, by using density functional theory periodic calculations, we theoretically investigated the stability, nucleation and electronic properties of cobalt clusters Con (n = 1-5) supported on γ-Al2O3 surfaces including dehydrated (100) and hydrated (110) surfaces. In Con/γ-Al2O3(100) (n = 1-5) and Con/γ-Al2O3(110) (n = 1 and 2), the Con clusters prefer to adsorb on the surface...
January 17, 2017: Physical Chemistry Chemical Physics: PCCP
M Kakazey, M Vlasova, V Gómez-Vidales, A Ángeles-Pascual, V A Basiuk
Mixtures of zinc oxide with carbon nanoparticles, ZnO + xC (x = 0.1%, 1% and 3% by weight), were subjected to mechanical processing (MP) in a hermetically sealed grinding chamber. Using electron paramagnetic resonance (EPR) spectroscopy, we monitored the evolution of spin centers in CNPs. While the initial CNPs were EPR silent, their short-duration MP (tMP) gave rise to emergence of low-intensity carbon signal. Increasing the sample temperature at tMP > 9 min induced CNP oxidation, which lead to a dramatic increase in the intensity of C signal...
January 17, 2017: Physical Chemistry Chemical Physics: PCCP
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