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Physical Chemistry Chemical Physics: PCCP

Fan Zhang, Yong-Heng Wang, Xiaowen Tang, Ruibo Wu
The TEAS, one of the sesquiterpene cyclases (FPPC), shows enzyme promiscuity that can effectively catalyze both the natural substrate (trans,trans)-FPP and the non-native (cis,trans)-FPP substrate to generate diverse products/byproducts. So far, the catalytic mechanism of the promiscuous substrate is still unclear. In this work, QM(DFT)/MM MD simulations were employed to illuminate the predominant 1,6-closure pathway reaction mechanism for the non-native substrate (cis,trans)-FPP, while the 1,10-closure pathway is the major reaction for the native substrate...
May 23, 2018: Physical Chemistry Chemical Physics: PCCP
Alec Owens, Andrey Yachmenev, Jochen Küpper, Sergei N Yurchenko, Walter Thiel
Accurate ab initio calculations on the rotation-vibration spectrum of methyl fluoride (CH3F) are reported. A new nine-dimensional potential energy surface (PES) and dipole moment surface (DMS) have been generated using high-level electronic structure methods. Notably, the PES was constructed from explicitly correlated coupled cluster calculations with extrapolation to the complete basis set limit and considered additional energy corrections to account for core-valence electron correlation, higher-order coupled cluster terms beyond perturbative triples, scalar relativistic effects, and the diagonal Born-Oppenheimer correction...
May 23, 2018: Physical Chemistry Chemical Physics: PCCP
Peter S Sherin, Yuri P Tsentalovich, Eric Vauthey, Enrico Benassi
Kynurenines (KNs) are natural UV filters of the human eye lens, protecting the eye tissues from solar UV radiation. Key points of their effective protection are the intramolecular charge transfer (ICT) in the excited state and the fast dissipation of absorbed light energy into heat via the intermolecular H-bonds. Herein we report that the introduction of an unsaturated double bond in the amino acid side chain, operating as an ICT-enhancing electron donor group, drastically accelerates the internal conversion (IC) due to a conical intersection (CI) between the potential energy surfaces of the excited and ground states...
May 23, 2018: Physical Chemistry Chemical Physics: PCCP
Meenakshi Joshi, Aditi Chandrasekar, Tapan K Ghanty
The positions of lawrencium (Lr), lutetium (Lu), actinium (Ac) and lanthanum (La) in the periodic table have been a controversial topic for quite some time. According to studies carried out by different groups with their justifications, these elements may potentially be placed in the d-block, p-block or all four in a 15 element f-block. The present work looks into this issue from a new perspective, which involves encapsulation of these four elements into Zintl ion clusters, Pb122- and Sn122-, followed by the determination of the structural, thermodynamic and electronic properties of these endohedral M@Pb122- and M@Sn122- clusters (M = Lrn+, Lun+ with n = 0, 1, 2, 3) using first principles based density functional theory (DFT)...
May 23, 2018: Physical Chemistry Chemical Physics: PCCP
Segun Goh, Andreas M Menzel, Hartmut Löwen
Ferrogels are smart soft materials, consisting of a polymeric network and embedded magnetic particles. Novel phenomena, such as the variation of the overall mechanical properties by external magnetic fields, emerge consequently. However, the dynamic behavior of ferrogels remains largely unveiled. In this paper, we consider a one-dimensional chain consisting of magnetic dipoles and elastic springs between them as a simple model for ferrogels. The model is evaluated by corresponding simulations. To probe the dynamics theoretically, we investigate a continuum limit of the energy governing the system and the corresponding equation of motion...
May 23, 2018: Physical Chemistry Chemical Physics: PCCP
Anita Dawes, Natalia Pascual, Nigel J Mason, Sabrina Gärtner, Søren V Hoffmann, Nykola C Jones
We present results of a combined vacuum ultraviolet (VUV) and infrared (IR) photoabsorption study of amorphous benzene : water mixtures and layers to investigate the benzene-water interaction in the solid phase. VUV spectra of 1 : 1, 1 : 10 and 1 : 100 benzene : water mixtures at 24 K reveal a concentration dependent shift in the energies of the 1B2u, 1B1u and 1E1u electronic states of benzene. All the electronic bands blueshift from pure amorphous benzene towards gas phase energies with increasing water concentration...
May 23, 2018: Physical Chemistry Chemical Physics: PCCP
Alicja Domaracka, Rudy Delaunay, Arkadiusz Mika, Michael Gatchell, Henning Zettergren, Henrik Cederquist, Patrick Rousseau, Bernd A Huber
Ionization, fragmentation and molecular growth have been studied in collisions of 22.5 keV He2+- or 3 keV Ar+-projectiles with pure loosely bound clusters of coronene (C24H12) molecules or with loosely bound mixed C60-C24H12 clusters by using mass spectrometry. The heavier and slower Ar+ projectiles induce prompt knockout-fragmentation - C- and/or H-losses - from individual molecules and highly efficient secondary molecular growth reactions before the clusters disintegrate on picosecond timescales. The lighter and faster He2+ projectiles have a higher charge and the main reactions are then ionization by ions that are not penetrating the clusters...
May 23, 2018: Physical Chemistry Chemical Physics: PCCP
Wojciech Olszewski, Irene Isturiz, Carlo Marini, Marta Avila, Masashi Okubo, Huiqiao Li, Haoshen Zhou, Takashi Mizokawa, Naurang Lal Saini, Laura Simonelli
We have investigated the nanostructuring effects on the local structure of V2O5 cathode material by means of temperature dependent V K-edge X-ray absorption fine structure measurements. We have found that the nanostructuring largely affects V-O and V-V bond characteristics with a general softening of the local V-O and V-V bonds. The obtained bond strengths correlate with the specific capacity shown by the different systems, with higher capacity corresponding to softer atomic pairs. The present study suggests the key role of local atomic displacements in the diffusion and storage of ions in cathodes for batteries, providing important information for designing new functional materials...
May 23, 2018: Physical Chemistry Chemical Physics: PCCP
Jianguang Feng, Hongzhou Dong, Beili Pang, Feifei Shao, ChunKai Zhang, Liyan Yu, Lifeng Dong
The effects of four heteroatoms (B, N, P, and S) with three doping patterns on graphene quantum dots (GQDs) are systematically investigated using time-dependent density functional theory (TD-DFT). The absorption spectra and HOMO-LUMO gaps are quantitatively analyzed to study the correlations between the optical properties and heteroatom doping of doped GQDs. Heteroatom doping can endow GQDs with various new optical and structural properties, depending on the dopants and doping configurations. Compared with the absorption spectra of pristine GQD, both N and S surface doping demonstrate a slight blue shift, whereas B and P doping lead to a blue shift for edge-doped GQDs with heteroatoms in a pentatomic ring...
May 23, 2018: Physical Chemistry Chemical Physics: PCCP
Daisuke Matsushita, Hirotaka Uji, Shunsaku Kimura
Electron transfer (ET) reactions via helical peptides composed of -(Aib-Pro)n- were studied in self-assembled monolayers and compared with -(Ala-Aib)n- peptides. Short Aib-Pro peptides showed slightly higher ET rates due to the better electronic coupling of the Pro residue. But, the 24mer Aib-Pro peptide showed a smaller ET rate than the corresponding Ala-Aib peptide. On the basis of DFT calculations, the deceleration of the ET rate of the longer Aib-Pro peptide is considered to be due to the smaller number of active modes of accordion-like oscillations than the Ala-Aib peptide, which has a strong influence on a long-range ET reaction...
May 23, 2018: Physical Chemistry Chemical Physics: PCCP
Libin Yang, Qinqin Sang, Juan Du, Ming Yang, Xiuling Li, Yu Shen, Xiaoxia Han, Xin Jiang, Bing Zhao
Ag simultaneously deposited and doped TiO2 (Ag-TiO2) hybrid nanoparticles (NPs) were prepared via a sol-hydrothermal method, as both a sensitive surface-enhanced Raman scattering (SERS) substrate and a superior photocatalyst for the first time. Ag-TiO2 hybrid NPs exhibit excellent SERS performance for several probe molecules and the enhancement factor is calculated to be 1.86 × 105. The detection limit of the 4-mercaptobenzoic acid (4-MBA) probe on the Ag-TiO2 substrate is 1 × 10-9 mol L-1, which is four orders of magnitude lower than that on pure TiO2 as a consequence of the synergistic effects of TiO2 and Ag...
May 23, 2018: Physical Chemistry Chemical Physics: PCCP
Bing Zheng, Liang Qiao, Hai-Tao Yu, Qi-Yue Wang, Ying Xie, Chao-Qun Qu
In this study, the structures and field-emission properties of Li-decorated buckled α-borophene (BBP) were investigated by first-principles density functional theory at the PW91 level. Using the computed binding energies, Hirshfeld- and electrostatic potential-derived charges, induced dipole moments, densities of states, and ionization potentials, we evaluated the influence of an applied electric field on the structural stability, work function, and field-emission current of the Li-decorated BBP nanostructures...
May 23, 2018: Physical Chemistry Chemical Physics: PCCP
Hyun-Young Lee, Jin Luo, Zhen Zhou, Wei Sun, Jing-Feng Li
High-quality (1 - x)(Bi0.5Na0.5)TiO3-xSrTiO3 lead-free piezoelectric thin films (x = 0, 0.1, and 0.25) on Pt(111)/Ti/SiO2/Si(100) substrates were prepared by a sol-gel method. The microstructures of the thin films as a function of SrTiO3 doping level and temperature were investigated by X-ray diffraction and Raman spectroscopy. Their temperature- and frequency-dependent piezoelectric properties were studied on the nanoscale using switching spectroscopy piezoresponse force microscopy (SS-PFM). A rhombohedral ferroelectric to pseudocubic relaxor phase transition was observed when either ST content or temperature increased...
May 23, 2018: Physical Chemistry Chemical Physics: PCCP
Jinggao Wu, Maowen Xu, Chun Tang, Guannan Li, Hong He, Chang Ming Li
F-Doping effects on polyaniline-derived carbon coated Li3V2(PO4)3 (Li3V2(PO4)3-xFx@C) as a cathode for high performance Li rechargeable batteries are systematically investigated with a combined experimental and DFT theoretical calculation approach. The results clearly indicate that the doping amount has a significant impact on the rate capability and long cycle life. The optimal material (Li3V2(PO4)2.88F0.12@C) delivers 123.16 mA h g-1@2C, which is close to the theoretical value (133 mA h g-1), while showing a greatly improved cycle stability...
May 23, 2018: Physical Chemistry Chemical Physics: PCCP
Chulho Song, Anli Yang, Osami Sakata, L S R Kumara, Satoshi Hiroi, Yi-Tao Cui, Kohei Kusada, Hirokazu Kobayashi, Hiroshi Kitagawa
To unveil the origin of the hydrogen-storage properties of rhodium nanoparticles (Rh NPs), we investigated the electronic and crystal structures of the Rh NPs using various synchrotron based X-ray techniques. Electronic structure studies revealed that the hydrogen-storage capability of Rh NPs could be attributed to their more unoccupied d-DOSs than that of the bulk near the Fermi level. Crystal structure studies indicated that lattice distortion and mean-square displacement increase while coordination number decreases with decreasing particle size and the hydrogen-absorption capability of Rh NPs improves to a greater extent with increased structural disorder in the local structure than with that in the mean structure...
May 23, 2018: Physical Chemistry Chemical Physics: PCCP
Jingyu Jin, Xiaoyan Li, Jiafeng Geng, Dengwei Jing
Combinations of nanoparticles and surfactants have been widely employed in many industrial processes, i.e., boiling and condensation in heat transfer and hydraulic fracturing in shale oil and gas production, etc. However, the underlying mechanism for various phenomena resulting from the addition of nanoparticles into the surfactant solutions is still unclear. For instance, there are contradictory conclusions from the literature regarding the variations of surface tension upon the addition of nanoparticles into surfactant solutions...
May 23, 2018: Physical Chemistry Chemical Physics: PCCP
Aniyush Juneja, G Rajasekaran
Graphene, viz., the one-atom-thick sheet of carbon, exhibits outstanding mechanical properties, but defects, which are inevitable at the time of synthesis, may strongly affect these properties. In this study, the effects of two types of Stone-Thrower-Wales (namely, STW-1 and STW-2) defects on the mechanical properties of graphene sheets at different temperatures and strain rates were investigated on the basis of molecular dynamics simulations. The authors also investigated the effect of the strain rate and defect concentration on the failure morphology of STW-1 and STW-2 defected graphene sheets...
May 23, 2018: Physical Chemistry Chemical Physics: PCCP
Matthew R Leyden, Toshinori Matsushima, Chuanjiang Qin, Shibin Ruan, Hao Ye, Chihaya Adachi
Organo-metal-halide perovskites are a promising set of materials for optoelectronic applications such as solar cells, light emitting diodes and lasers. Perovskite thin films have demonstrated amplified spontaneous emission thresholds as low as 1.6 μJ cm-2 and lasing thresholds as low as 0.2 μJ cm-2. Recently the performance of perovskite light emitting diodes has rapidly risen due to the formation of quasi 2D films using bulky ligands such as phenylethylammonium. Despite the high photoluminescent yield and external quantum efficiency of quasi 2D perovskites, few reports exist on amplified spontaneous emission...
May 23, 2018: Physical Chemistry Chemical Physics: PCCP
Ankita Joshi, C N Ramachandran
Using the dispersion-corrected density functional B97D and 6-31g(d,p) basis set, the structural, stability, electronic, optical and charge transport properties of the complexes formed by encapsulating indigo inside carbon nanotubes (CNTs) of varying diameters are investigated. Based on the stabilization energy of the complexes indigo@(n,n)CNT (where n = 6, 7 and 8), indigo@(7,7)CNT is shown to be the most stable owing to the ideal diameter of (7,7)CNT for encapsulating indigo. The nature of the interaction between the guest and the host is investigated by means of energy decomposition analysis employing the symmetry adapted perturbation theory...
May 23, 2018: Physical Chemistry Chemical Physics: PCCP
Jia-Huan Hou, Di Wu, Jia-Yuan Liu, Si-Yi Li, Dan Yu, Ying Li
The interaction of the superalkali cation Li3+ with water molecules, as well as the structures and stability of the resulting water complexes are theoretically studied at the MP2/6-311++G(d,p) level. A great number of geometrical configurations were obtained for the Li3+(H2O)n (n = 1-5) complexes and Li3+ is found to have a maximum coordination number of four. Natural population analysis shows that the charge distribution of Li3+ becomes seriously uneven upon interaction with five water molecules, so it loses ring conjugation and splits in the lowest-energy isomer of Li3+(H2O)5...
May 23, 2018: Physical Chemistry Chemical Physics: PCCP
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