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Physical Chemistry Chemical Physics: PCCP

Marten H Vos, Brandon J Reeder, Fevzi Daldal, Ursula Liebl
We present a full investigation of ultrafast light-induced events in the membraneous cytochrome bc1 complex by transient absorption spectroscopy. This energy-transducing complex harbors four redox-active components per monomer: heme c1, two 6-coordinate b-hemes and a [2Fe-2S] cluster. Using excitation of these components in different ratios under various excitation conditions, probing in the full visible range and under three well-defined redox conditions, we demonstrate that for all ferrous hemes of the complex photodissociation of axial ligands takes place and that they rebind in 5-7 ps, as in other 6-coordinate heme proteins, including cytoglobin, which is included as a reference in this study...
February 20, 2017: Physical Chemistry Chemical Physics: PCCP
Aaron A Wiegel, Matthew J Liu, William D Hinsberg, Kevin R Wilson, Frances A Houle
Multiphase chemical reactions (gas + solid/liquid) involve a complex interplay between bulk and interface chemistry, diffusion, evaporation, and condensation. Reactions of atmospheric aerosols are an important example of this type of chemistry: the rich array of particle phase states and multiphase transformation pathways produce diverse but poorly understood interactions between chemistry and transport. Their chemistry is of intrinsic interest because of their role in controlling climate. Their characteristics also make them useful models for the study of principles of reactivity of condensed materials under confined conditions...
February 20, 2017: Physical Chemistry Chemical Physics: PCCP
Irene Adroher-Benítez, Alberto Martín-Molina, Silvia Ahualli, Manuel Quesada-Pérez, Gerardo Odriozola, Arturo Moncho-Jordá
In this work the equilibrium distribution of ions around a thermo-responsive charged nanogel particle in an electrolyte aqueous suspension is explored using coarse-grained Monte Carlo computer simulations and the Ornstein-Zernike integral equation theory. We explicitly consider the ionic size in both methods and study the interplay between electrostatic and excluded-volume effects for swollen and shrunken nanogels, monovalent and trivalent counterions, and for two different nanogel charges. We find good quantitative agreement between the ionic density profiles obtained using both methods when the excluded repulsive force exerted by the cross-linked polymer network is taken into account...
February 20, 2017: Physical Chemistry Chemical Physics: PCCP
Isaac Kwame Attah, Abdel-Rahman Soliman, Sean P Platt, Michael Meot-Ner Mautner, Saaudallah G Aziz, M Samy El-Shall
Polycyclic aromatic hydrocarbons (PAHs) and polycyclic aromatic nitrogen heterocyclics (PANHs) are present in ionizing environments, including interstellar clouds and solar nebulae, where their ions can interact with neutral PAH and PANH molecules leading to the formation of a variety of complex organics including large N-containing ions. Herein, we report on the formation of a covalently-bonded (benzene·pyrimidine) radical cation dimer by the gas phase reaction of pyrimidine with the benzene radical cation at room temperature using the mass-selected ion mobility technique...
February 20, 2017: Physical Chemistry Chemical Physics: PCCP
Ernesto Quintas Sánchez, Marie-Lise Dubernet
A new five-dimensional potential energy surface is calculated at the coupled-cluster CCSD(T) level of theory for the HCN-water system, treating both monomers as rigid rotors. The associated methodology, which combines extensive ab initio calculations of moderate accuracy (CCSD(T)/AVDZ) and a fitting procedure involving a much lower angular coverage with more accurate ab initio calculations (CCSD(T)/CBS), is described in detail. This methodology provides a time-saving approach to compute quantitatively accurate potential energy surfaces with reasonable computational effort...
February 20, 2017: Physical Chemistry Chemical Physics: PCCP
B Pattengale, J Huang
Monoclinic-scheelite BiVO4 has been widely studied as a promising oxygen evolution reaction (OER) catalyst in artificial photosynthesis. Though significant progress to improve or augment its catalysis performance has been made, fundamental understanding of its relatively poor performance as a bare material is lacking. In this paper, we report the correlation of the surface structure and trap states with charge separation efficiency and OER performance of bare BiVO4 photoanodes via varying the sample thickness...
February 20, 2017: Physical Chemistry Chemical Physics: PCCP
Andrei A Mosunov, Irina S Pashkova, Maria Sidorova, Artem Pronozin, Anastasia O Lantushenko, Yuriy I Prylutskyy, John A Parkinson, Maxim P Evstigneev
We report a new analytical method that allows the determination of the magnitude of the equilibrium constant of complexation, Kh, of small molecules to C60 fullerene in aqueous solution. The developed method is based on the up-scaled model of C60 fullerene-ligand complexation and contains the full set of equations needed to fit titration datasets arising from different experimental methods (UV-Vis spectroscopy, (1)H NMR spectroscopy, diffusion ordered NMR spectroscopy, DLS). The up-scaled model takes into consideration the specificity of C60 fullerene aggregation in aqueous solution and allows the highly dispersed nature of C60 fullerene cluster distribution to be accounted for...
February 20, 2017: Physical Chemistry Chemical Physics: PCCP
Alexander Kyrychenko, Dmitry A Pasko, Oleg N Kalugin
Chemical modification of silver nanoparticles (AgNPs) with a stabilizing agent, such as poly(vinyl alcohol) (PVA), plays an important role in shape-controlled seeded-growth and colloidal stability. However, theoretical aspects of the stabilizing mechanism of PVA are still poorly understood. To gain a better understanding of the role of PVA in water protecting effects for silver nanoparticles, we developed an atomistic model of a AgNP grafted with single-chain PVA of various lengths. Our model, designed for classical molecular dynamics (MD) simulations, approximates the AgNP as a quasi-spherical silver nanocrystal with 3...
February 20, 2017: Physical Chemistry Chemical Physics: PCCP
P R Birkin, T M Foley, T T Truscott, A Merritt, S Martini
Cavitation clusters and streamers are characterised in lipid materials (specifically sunflower oil) and compared to water systems. The lipid systems, which are important in food processing, are studied with high-speed camera imaging, laser scattering and pressure measurements. In these oils, clusters formed at an aged (roughened) tip of the sound source (a piston like emitter, PLE) are shown to collapse with varied periodicity in relation to the drive amplitude employed. A distinct streamer (an area of increased flow emanating from the cavitation cluster) is seen in the lipid media which is collimated directly away from the tip of the PLE source whereas in water the cavitation plume is visually less distinct...
February 20, 2017: Physical Chemistry Chemical Physics: PCCP
Maxwell Reinhardt, Simon Dalgleish, Yoshiaki Shuku, Louisa Reissig, Michio M Matsushita, Jason Crain, Kunio Awaga, Neil Robertson
The structure and electronic properties of a novel cobalt half sandwich complex of cyclopentadiene (Cp) and diaminonaphthalene (DAnap) [CpCo(DAnap)] are described and compared to the previously reported diaminobenzene derivative [CpCo(DAbnz)] in view of their potential for (opto)electronic device application. Both complexes show stable redox processes, tunable through the diaminoacene ligand, and show strong absorption in the visible region, with additional transitions stretching into the near infrared (NIR)...
February 20, 2017: Physical Chemistry Chemical Physics: PCCP
Fabiana A Gutierrez, Flavio C Bedatty Fernandes, Gustavo A Rivas, Paulo R Bueno
The electronic density of states and its contribution to the capacitance of graphene compounds (oxidized and reduced) were investigated using an electrochemical impedance-derived capacitance spectroscopic approach. It is clearly demonstrated that graphene oxide, which is known to exhibit semiconductor electronic characteristics, has little influence on the magnitude of the measured capacitance. Moreover, when graphene oxide is electrochemically reduced to graphene, the capacitance increases dramatically by about three orders of magnitude (from microfaradays to millifaradays)...
February 20, 2017: Physical Chemistry Chemical Physics: PCCP
Alessio Ausili, Ana M de Godos, Alejandro Torrecillas, Francisco J Aranda, Senena Corbalán-García, Juan C Gómez-Fernández
α-Tocopherol is a natural preservative that prevents free radical chain oxidations in biomembranes. We have studied the location of α-tocopherol in model membranes formed by different unsaturated phosphatidylcholines, namely 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), 1-palmitoyl-2-linoleoyl-sn-glycero-3-phosphocholine (PLPC), 1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphocholine (PAPC) and 1-palmitoyl-2-docosahexaenoyl-sn-glycero-3-phosphocholine (PDPC). Small angle X-ray diffraction revealed that α-tocopherol was well mixed with all the phospholipids...
February 17, 2017: Physical Chemistry Chemical Physics: PCCP
Alireza Faghaninia, Guodong Yu, Umut Aydemir, Max Wood, Wei Chen, Gian-Marco Rignanese, G Jeffrey Snyder, Geoffroy Hautier, Anubhav Jain
Bournonite (CuPbSbS3) is an earth-abundant mineral with potential thermoelectric applications. This material has a complex crystal structure (space group Pmn21 #31) and has previously been measured to exhibit a very low thermal conductivity (κ < 1 W m(-1) K(-1) at T ≥ 300 K). In this study, we employ high-throughput density functional theory calculations to investigate how the properties of the bournonite crystal structure change with elemental substitutions. Specifically, we compute the stability and electronic properties of 320 structures generated via substitutions {Na-K-Cu-Ag}{Si-Ge-Sn-Pb}{N-P-As-Sb-Bi}{O-S-Se-Te} in the ABCD3 formula...
February 17, 2017: Physical Chemistry Chemical Physics: PCCP
Xiaoyue Zhang, Jian Shao, Yun Chen, Weijin Chen, Jing Yu, Biao Wang, Yue Zheng
Azurin (Az) has been considered as the research hotspot in molecular electronics, as well as a promising material for building functional devices on the molecular scale because of its special electrical properties and force-dependent conductance effects. Here we carry out an in-depth investigation combined with molecular scale experiments, molecular dynamics simulations, first-principles calculations and theoretical models to reveal the dynamic conductance response of the Az monolayer under cyclic mechanical loading...
February 17, 2017: Physical Chemistry Chemical Physics: PCCP
Apurva Shantilal Gangrade, Akhil Aditya Varma, Nikhil Kishor Gor, Sweta Shriniwasan, Sankara Sarma V Tatiparti
The dehydrogenation mechanism during the incubation period in nanocrystalline MgH2 (low α: converted metal fraction and dα/dt) and the reasons for the occurrence of the incubation period at 320, 350, and 400 °C were investigated. Pre-existing Mg crystallites can enhance Mg nucleation during the incubation period, as suggested by the estimated activation energy for nucleation (12 ± 2 kJ per mol H). The released H-atoms enter MgH2 as interstitials, as indicated by the MgH2 unit-cell contraction, resulting in increased equatorial Mg-H bond length, decreased charge-density distribution in the interstitial region, as observed from the charge-density maps, and decreased H-H distance in the {001} plane up to the midway of the incubation period...
February 17, 2017: Physical Chemistry Chemical Physics: PCCP
Sergey V Bondarchuk, Boris F Minaev
A new ambient-pressure metastable single-bonded 3D nitrogen allotrope (TrigN) of trigonal symmetry (space group R3[combining macron]) was calculated using density functional theory (DFT). A comprehensive characterization of this material, comprising thermodynamic, elastic, and spectral (vibrational, UV-vis absorption, and nuclear magnetic resonance) properties, was performed. Using high-throughput band structure calculation, the TrigN phase was characterized as an insulator with an indirect band gap of 2.977 eV...
February 17, 2017: Physical Chemistry Chemical Physics: PCCP
Denis A Rychkov, Jernej Stare, Elena V Boldyreva
The present study delivers a computational approach for the understanding of the mechanism of phase transitions between polymorphs of small organic molecules. By using state of the art periodic DFT calculations augmented with dispersion corrections and an external stress tensor together with gas-phase cluster calculations, we thoroughly explained the reversible phase transitions of three polymorphs of the model system, namely crystalline l-serine in the pressure range up to 8 GPa. This study has shown that at the macroscopic level the main driving force of the phase transitions is the decrease in the volume of the crystal unit cell, which contributes to the enthalpy difference between the two forms, but not to the difference in their internal crystal energies...
February 17, 2017: Physical Chemistry Chemical Physics: PCCP
Marta Reig, Gintautas Bagdziunas, Dmytro Volyniuk, Juozas V Grazulevicius, Dolores Velasco
A series of push-pull carbazole-based compounds has been experimentally and theoretically characterized in combination with the X-ray analysis of the corresponding single crystals. The introduction of the strong electron-withdrawing tricyanovinyl group in the carbazole core affords electron-transporting ability in addition to the characteristic hole-transporting properties exhibited by donor carbazole derivatives.
February 17, 2017: Physical Chemistry Chemical Physics: PCCP
Puja Paul, Soumya Sundar Mati, Subhash Chandra Bhattacharya, Gopinatha Suresh Kumar
This study focuses on the understanding of the interaction of phenothiazinium dyes methylene blue (MB), new methylene blue (NMB), azure A (AZA) and azure B (AZB) with tRNA(Phe) with particular emphasis on deciphering the mode and energetics of the binding. Strong intercalative binding to tRNA(Phe) was observed for MB, NMB and AZB, bound by a partial intercalative mode. AZA has shown groove binding characteristics. From spectroscopic studies binding affinity values of the order of 10(5) M(-1) were deduced for these dyes; the trend varied as MB > NMB > AZB > AZA...
February 17, 2017: Physical Chemistry Chemical Physics: PCCP
Xiaomin Wan, Tong Gao, Liangshun Zhang, Jiaping Lin
Self-consistent field theory with a dynamic extension is exploited to investigate the kinetics of the lamellar formation of symmetric block copolymers under the direction of external fields. In particular, three types of directed self-assembly methods - a permanent field for chemo-epitaxy, a dynamic field for zone annealing and an integrated permanent/dynamic field - are examined. For the chemo-epitaxy involving sparsely prepatterned substrates or zone annealing, the block copolymers generally develop into polycrystalline nanostructures with multiple orientations due to the lack of strong driving forces for eliminating the long-lived imperfections in a limited time...
February 17, 2017: Physical Chemistry Chemical Physics: PCCP
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