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Physical Chemistry Chemical Physics: PCCP

Yanhui Zhang, Hongxu Guo, Wen Weng, Ming-Lai Fu
Reduced graphene oxide (RGO) as an electron-conductive medium and photosensitizer have been widely used to construct efficient RGO/semiconductor photocatalysts for solar energy conversion; however, the role of RGO has been largely underestimated. Herein, the surface plasmon resonance (SPR) effect, thermal effect, support effect, and size effect of Au/RGO are demonstrated to play important roles in enhancing the photocatalytic activity, which has not been considered previously. Au/RGO nanocomposites, synthesized via a facile wet chemistry route, exhibit an excellent visible light photocatalytic performance for selective oxidation of benzylic alcohols...
November 20, 2017: Physical Chemistry Chemical Physics: PCCP
Wanheng Lu, Lai-Mun Wong, Shijie Wang, Kaiyang Zeng
Resistive switching on the nanoscale is an emerging research field and Scanning Probe Microscopy (SPM) is a powerful tool for studies in this area. Under the SPM tip, the electrical field is very high due to the small tip radius on the order of tens of nanometers, and this can enable a range of ionic/electrochemical phenomena during the resistive switching of the materials under the SPM tip. Although the ionic/electrochemical phenomena have long been considered vital for the resistive switching of materials, a few pieces of experimental evidence, as well as the decoupling of the effects of the electrochemical processes at different stages, are still needed...
November 20, 2017: Physical Chemistry Chemical Physics: PCCP
C Struzzi, M Scardamaglia, N Reckinger, H Sezen, M Amati, L Gregoratti, J-F Colomer, C Ewels, R Snyders, C Bittencourt
Plasma fluorination of graphene is studied using a combination of spectroscopy and microscopy techniques, giving insight into the yield and fluorination mechanism for functionalization of supported graphene with both CF4 and SF6 gas precursors. Ion acceleration during fluorination is used to probe the effect on grafting functionalities. Adatom clustering, which occurs with CF4 plasma treatment, is suppressed when higher kinetic energy is supplied to the ions. During SF6 plasma functionalization, the sulfur atoms tend to bond to bare copper areas instead of affecting the graphene chemistry, except when the kinetic energy of the ions is restricted...
November 20, 2017: Physical Chemistry Chemical Physics: PCCP
Alessandra Candian, Jordy Bouwman, Patrick Hemberger, Andras Bodi, Alexander G G M Tielens
Diamond nanoparticles, or nanodiamonds, are intriguing carbon-based materials which, maybe surprisingly, are the most abundant constituent of presolar grains. While the spectroscopic properties of even quite large diamondoids have already been explored, little is known about their unimolecular fragmentation processes. In this paper we characterise the dissociative ionisation of adamantane (C10H16) - the smallest member of the diamondoid family - utilising imaging Photoelectron Photoion Coincidence (iPEPICO) spectroscopy and Density Functional Theory (DFT) calculations...
November 20, 2017: Physical Chemistry Chemical Physics: PCCP
Fabio Ribeiro Negreiros, Luana Sucupira Pedroza, Flavio Leandro Souza, Gustavo Martini Dalpian
Haematite (α-Fe2O3) is a potential candidate for photo-electrochemical water splitting. It is abundant and its electronic properties fit those needed for this kind of device. However, very little is known about the intermediate steps of this photon-induced water splitting process. We propose here that surface iron vacancies can be the main defects responsible for the activity of haematite in the photoelectrochemical reaction. We perform DFT+U calculations and explicitly add holes to show that these defects are common in iron-terminated (0001) surfaces...
November 20, 2017: Physical Chemistry Chemical Physics: PCCP
Anastasia Kultaeva, Timur Biktagirov, Jens Bergmann, Linda Hensel, Harald Krautscheid, Andreas Pöppl
Continuous wave X-band electron paramagnetic resonance (EPR) and density functional theory (DFT) were successfully applied to explore the incorporation and coordination state of the Cu(2+) ions in the [Cd0.98Cu0.02(prz-trz-ia)] porous metal-organic frameworks. EPR measurements on powder samples and single crystals provided the full electron Zeeman g and copper hyperfine A(Cu) interaction tensors including the orientation of their principal axes frames. DFT computations allowed for a detailed interpretation of the experimental results in terms of coordination symmetry and binding properties of the paramagnetic Cu(2+) ions...
November 20, 2017: Physical Chemistry Chemical Physics: PCCP
Juan Ignacio Lopez Ortiz, Paola Torres, Evelina Quiroga, Claudio F Narambuena, Antonio J Ramirez-Pastor
In the present work, the adsorption of three-domain antifreeze proteins on ice is studied by combining a statistical thermodynamics based theory and Monte Carlo simulations. The three-domain protein is modeled by a trimer, and the ice surface is represented by a lattice of adsorption sites. The statistical theory, obtained from the exact partition function of non-interacting trimers adsorbed in one dimension and its extension to two dimensions, includes the configuration of the molecule in the adsorbed state, and allows the existence of multiple adsorption states for the protein...
November 20, 2017: Physical Chemistry Chemical Physics: PCCP
Jian-Qing Dai, Xiao-Ya Li, Jie-Wang Xu
For graphene/ferroelectric hybrid structures, the atomistic and electronic details of the interfaces are of crucial importance for charge doping in graphene. In this paper, we choose thermodynamically stable BiFeO3(0001) surfaces to explore the adsorption behavior and charge doping effect in a graphene/BiFeO3 system. By performing first-principles calculations, we find that both the adsorption behavior and charge doping effect show distinct characteristics for graphene adsorbed on the oppositely polarized BiFeO3(0001) surfaces...
November 20, 2017: Physical Chemistry Chemical Physics: PCCP
Peng-Wei Zhu, Luguang Chen
In this paper, we investigate the micelle (charge)-constrained collapse of a spherical poly(N-isopropylacrylamide) (PNIPAM) brush. The system is an example of the transition of a short-length neutral polymer from a stretched state to a folded state under the constraint of long-range electrostatic repulsion. The collapsed state is described as an anisotropic globule comprising a cascade of rod-like or hairpin bundles. A critical aggregation number of bound micelles is obtained to distinguish the charge-induced deformation of the globule, which provides a guideline to characterize globule dimensions under different strengths of electrostatic interaction...
November 20, 2017: Physical Chemistry Chemical Physics: PCCP
Cameron C Bright, Matthew B Prendergast, Patrick D Kelly, James P Bezzina, Stephen J Blanksby, Gabriel da Silva, Adam J Trevitt
Small nitrogen containing heteroaromatics are fundamental building blocks for many biological molecules, including the DNA nucleotides. Pyridine, as a prototypical N-heteroaromatic, has been implicated in the chemical evolution of many extraterrestrial environments, including the atmosphere of Titan. This paper reports on the gas-phase ion-molecule reactions of the three dehydro-N-pyridinium radical cation isomers with propene. Photodissociation ion-trap mass spectrometry experiments are used to measure product branching ratios and reaction kinetics...
November 20, 2017: Physical Chemistry Chemical Physics: PCCP
Lluís Blancafort, Alexander A Voityuk
The rate of photoinduced ET in molecular systems is controlled by electronic coupling of the locally excited and charge transfer states. We generalize the Bixon-Jortner-Verhoeven expression for electronic coupling to systems with a small energy gap and derive the transfer integral for charge separation in two model heterojunctions using the excitation energies and oscillator strengths computed with TD DFT. The estimated couplings are in good agreement with the reference values.
November 20, 2017: Physical Chemistry Chemical Physics: PCCP
Juan Ramón Avilés-Moreno, Giel Berden, Jos Oomens, Bruno Martínez-Haya
The distinct basicity of the guanidinium side-group of arginine (Arg) sustains specific interactions involved in essential biochemical processes. The sensing of arginine is therefore key in modern biotechnology and bioanalysis. In this context, the development of molecular receptors based on crown ether building blocks has demonstrated great potential. We investigate the complexes formed by arginine with two benchmark macrocycles, 12-crown-4 (1,4,7,10-tetraoxacyclododecane) and its N-substituted analog cyclen (1,4,7,10-tetraazacyclododecane)...
November 17, 2017: Physical Chemistry Chemical Physics: PCCP
Siqi Kai, Xu Li, Bolin Li, Xiaofeng Han, Xiaolin Lu
Hydrolysis of planar phospholipids catalyzed by honey bee venom phospholipase A2 (bvPLA2) was studied. Experiments demonstrated that Ca(2+) ions mediated between the lipids and bvPLA2, induced reorientation of bvPLA2, and activated hydrolysis. One of the hydrolysis products, fatty acids, was desorbed, and the other one, lysophospholipids, self-organized at the interface.
November 17, 2017: Physical Chemistry Chemical Physics: PCCP
Masayuki Suda, Hiroshi M Yamamoto
Stimulated by the discovery of high-temperature superconductivity in 1986, band-filling control of strongly correlated electron systems has been a persistent challenge over the past three decades in condensed matter science. In particular, recent efforts have been focused on electrostatic carrier doping of these materials, utilising field-effect transistor (FET) structures to find novel superconductivity. Our group found the first field-induced superconductivity in an organic-based material in 2013 and has been developing various types of superconducting organic FETs...
November 17, 2017: Physical Chemistry Chemical Physics: PCCP
Yutaro Kawazu, Hiroshi Hoke, Yasunori Yamada, Tatsuya Umecky, Kazuhiko Ozutsumi, Toshiyuki Takamuku
The thermodynamics of complex formation of Ni(2+) with molecular liquids (ML), dimethyl sulfoxide (DMSO), methanol (MeOH), and acetonitrile (AN) in the ionic liquid (IL) of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide ([C2mim][TFSA]) has been elucidated using ultraviolet (UV)-visible spectroscopy. X-ray structural analyses for single crystals grown from Ni(2+)-[C2mim][TFSA]-DMSO and -AN solutions at high ML contents have shown that six DMSO oxygen or AN nitrogen atoms coordinate with Ni(2+) to form octahedral structures of [Ni(dmso)6](TFSA)2 and [Ni(an)6](TFSA)2, respectively...
November 17, 2017: Physical Chemistry Chemical Physics: PCCP
Bikash Mandal, Jin Suk Chung, Sung Gu Kang
The geometric, magnetic, and electronic properties and the drug capturing abilities of Hofmann-type metal organic frameworks (MOFs) were examined using theoretical calculations. The detailed theoretical calculations predicted that the Hofmann sheet can have two different conformations, planar and twisted. The Ni-Co sheet was the most stable among the systems studied, whereas the Ni-Fe sheet was the least stable. All of the sheets were magnetic spin semiconductors, having Dirac-like and dispersionless bands, which give rise to a major spatial separation between the charge carriers upon excitation...
November 17, 2017: Physical Chemistry Chemical Physics: PCCP
S Bouzakraoui, N Mousseau
Human islet amyloid polypeptide (hIAPP) is a 37-residue polypeptide, considered to be the main component of the pancreatic islet amyloid associated with type 2 diabetes and is one of the most amyloidogenic polypeptides known. Although the structure of hIAPP fibrils has already been obtained, structures of early oligomers and the mechanism of β-sheet formation remain poorly understood. Herein, we characterize the atomic structure and the thermodynamics of the 14-37 residue fragment of hIAPP wild-type and mutated dimers and trimers...
November 17, 2017: Physical Chemistry Chemical Physics: PCCP
Yunjun Cao, Min Yu, Shandong Qi, Tingting Wang, Shiming Huang, Zhengfeng Ren, Shishen Yan, Shujun Hu, Mingchun Xu
The CO2 adsorption and dynamic behaviors on single crystal anatase TiO2(101) surfaces were investigated by UHV-FTIRS and first-principles calculations. The IRRAS results at 90 K show that the ν3(OCO) asymmetric stretching vibration of adsorbed CO2 exhibits band splitting at rather low CO2 coverage in p-polarized IR spectra for the IR beam incident along the [101[combining macron]] direction. Co-adsorbed CO can prevent such band splitting. Ab initio molecular dynamics (AIMD) simulations revealed that the adsorbed CO2 at finite temperature does not keep a stationary adsorption state but keeps a certain swing motion: one end of the linear CO2 molecule binds to surface Ti5c sites and the other end swings within the (010) plane with a tilted angle distribution ranging from 10° to 60° relative to the [101[combining macron]] direction...
November 17, 2017: Physical Chemistry Chemical Physics: PCCP
Xueqing Zhang, Chonglong Cao, Anja Bieberle-Hütter
The structures of transition metal surfaces and metal oxides are commonly believed to have a significant effect on the catalytic reactions. Density functional theory calculations are therefore used in this study to investigate the oxygen evolution reaction (OER) over nanostructured, i.e. nanocluster and nanocavity, surfaces of hematite (Fe2O3). The calculated results demonstrate an optimum nanocluster size with respect to the OER overpotential. The presence of nanoclusters on the electrode is regarded as an attractive strategy for increasing the activity in photoelectrochemical water splitting...
November 17, 2017: Physical Chemistry Chemical Physics: PCCP
Peter M Felker, Vojtěch Vlček, Isaac Hietanen, Stephen FitzGerald, Daniel Neuhauser, Zlatko Bačić
Symmetry breaking has been recently observed in the endofullerenes M@C60 (M = H2, HF, H2O), manifesting in the splittings of the three-fold degenerate ground states of the endohedral ortho-H2, ortho-H2O and the j = 1 level of HF. The nature of the interaction causing the symmetry breaking is established in this study. A fragment of the solid C60 is considered, comprised of the central C60 molecule surrounded by twelve nearest-neighbor (NN) C60 molecules. The fullerenes have either P (major) or H (minor) orientational orderings, and are assumed to be rigid with Ih symmetry...
November 17, 2017: Physical Chemistry Chemical Physics: PCCP
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