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Chemical Physics

Current research reports and chronological list of recent articles..




The international scientific journal Chemical Physics welcomes experimental and theoretical papers in the molecular, biological and materials sciences.

The publisher is Elsevier. The copyright and publishing rights of specialized products listed below are in this publishing house. This is also responsible for the content shown.

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Additional research articles see Current Chemistry Research Articles. Magazines with similar content (chemical physics):

 - ChemPhysChem.

 - Faraday Discussions.

 - Journal of Chemical Physics.

 - Journal of Physical Chemistry.

 - Physical Chemistry Chemical Physics PCCP.



Chemical Physics - Abstracts



Gas-liquid diffusion synthesis of different Ni(OH)<sub>2</sub> nanostructures for their supercapacitive performance

Publication date: 1 September 2019

Source: Chemical Physics, Volume 525

Author(s): Jiangshan Zhao, Suqi Huang, Liang Song, Zongshan Zhao

Abstract

The wide interlayer spacing can improve charge transfer rate and release the internal strain during the discharge-charge processes. The interlayer spacing and crystal phase of Ni(OH)2 nanocrystals are generally associated with the introduction of various anions. In this study, we have prepared four kinds of Ni(OH)2 nanocrystals with a simple gas-liquid route by simply altering the Ni salts. The crystal phases of the obtained Ni(OH)2 nanostructures can be controlled by the introduction of nitrate, chlorine, acetate and sulfate anions respectively. The electrochemical test results indicate that flake-like Ni(OH)2 prepared using nickel acetate exhibits the largest charge storage capacity and capacitance value can be reached 2018 F g−1 at 10 A g−1 current density in 2 mol L−1 KOH electrolyte.


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Several considerations on the empirical rate formula for ion-molecule reactions and low-temperature-high-speed radical reactions

Publication date: 1 September 2019

Source: Chemical Physics, Volume 525

Author(s): Shin Sato

Abstract

Empirical rate formula for the low temperature reaction is applied to ion-molecule and radical reactions and several comments on them are discussed: the role of the third body molecules on the ion-molecule reactions, the reactivity of O+ ions, the mixing of high-speed radical reaction with Arrhenius-type reaction and the contribution of Wigner’s limits of old and newly measured radical reactions to the knowledge on the reaction mechanisms of these reactions.


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High-pressure control of photosynthetic excitons

Publication date: 1 September 2019

Source: Chemical Physics, Volume 525

Author(s): Mihkel Pajusalu, Margus Rätsep, Liina Kangur, Arvi Freiberg

Abstract

In photosynthesis, collective pigment excitations – excitons – facilitate chemical reactions for sustainable biological function. Here, the effect of hydrostatic pressure – an important thermodynamic stress factor – on optical spectral properties of excitons in the cyclic light-harvesting 2 pigment-protein complex from photosynthetic bacterium Rhodoblastus acidophilus was first studied. The high pressure-induced modifications of absorption, fluorescence and polarized fluorescence excitation spectra were theoretically analyzed in terms of the disordered molecular exciton model. We uniquely show that the observed shift of the spectra under pressure is largely governed by the pressure-induced rise of two factors: the exciton displacement energy and the exciton coupling energy, which increases the spread of the exciton state manifold. A significant increase of static energy disorder revealed by model calculations suggests that high-pressure compressing of the complex is actually accompanied by altered spatial orientations and conformations of the protein-embedded pigment molecules.

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Influence of triplet states on single donor-acceptor pair fluorescence

Publication date: 1 September 2019

Source: Chemical Physics, Volume 525

Author(s): I.S Osad'ko

Abstract

Single donor-acceptor (D-A) pairs whose molecules have both singlet and triplet states are considered. Fluorescence of such D-A pair has two types of fluctuations: fluctuations due to singlet-triplet transitions and fluctuations because of energy transfer in D-A pair. Both types of fluctuations manifest themselves in the duration of on/off intervals in fluorescence trajectories. Triplet state in the donor molecule creates off-intervals in D- and A-fluorescence. However, it does not influence FRET efficiency E. Another picture we will observe if we take into account triplet state in the acceptor molecule. This state influences FRET efficiency distribution S(E) considerable. 1) Acceptor triplet state hampers energy transfer in D-A pair and changes expression for S(E). 2) Acceptor triplet state is responsible for appearance off-intervals in A-fluorescence and dual d-fluorescence: bright and moderate. Fluctuating D- and A-fluorescence are simulated with the help of Monte Carlo method. Dual d-fluorescence of single D-A pair creates FRET efficiency distribution S(E) with two maxima.


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Heterogeneity in structure and dynamics of water near bilayers using TIP3P and TIP4P/2005 water models

Publication date: 1 September 2019

Source: Chemical Physics, Volume 525

Author(s): Abhinav Srivastava, Sheeba Malik, Ananya Debnath

Abstract

Capturing structure and dynamics of both lipids and water near membranes using simulations as in experiments is a challenging task till date. Dimyristoylphophatidylcholine (DMPC) lipid bilayers with Berger and CHARMM36 force-fields have been investigated at fluid phase with TIP3P and TIP4P/2005 water models. Interfacial water molecules (IW) near lipid bilayers exhibit local distorted tetrahedrality within the first hydration shell of interface water for both water models. Anomalous diffusion exponents of IW hydrogens show oscillations without decaging at an intermediate length scale slightly larger than the intermolecular separation. The non-Gaussian parameters of bulk water decay to zero for both water models at a time-scale consistent with previously reported neutron scattering experiments, whereas IW exhibit β to α relaxations which are universal signatures of glassy dynamics. These results provide insights on the choice of force-fields to apprehend underlying physical laws of water relaxations near membranes and will be useful to study membrane phase transitions in future.

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High-temperature and high-pressure thermophysical properties of AlP semiconducting material: A systematic <em>ab initio</em> study

Publication date: 1 September 2019

Source: Chemical Physics, Volume 525

Author(s): Salah Daoud, Nadir Bouarissa, Nadhira Bioud, Pawan Kumar Saini

Abstract

The finite temperature thermophysical quantities are one of the most important properties of solids and have become the subject of significant interdisciplinary interest in recent years. We report a detailed theoretical investigation on the equation of state (EoS) parameters, electronic polarizability and finite temperature thermophysical properties of aluminum phosphide using plane-wave pseudopotential approach in the framework of the density functional theory within the generalized gradient approximation. Our results regarding EoS parameters and electronic polarizability are found to be in good accord with previous data reported in the literature. Moreover, using the model of the quasi-harmonic Debye approximation plus empirical energy corrections, the thermophysical properties for temperatures up to 2000 K are examined and discussed. Our findings show that the thermophysical properties vary monotonically with either temperature or pressure which is consistent with the trends previously reported in the literature.


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Preparation and properties of TiO<sub>2</sub>/illite composites synthesized at different hydrothermal pH values

Publication date: 1 September 2019

Source: Chemical Physics, Volume 525

Author(s): Zhiqiang Dong, Meiqi Ling, Yinshan Jiang, Minglei Han, Guihua Ren, Jiahao Zhang, Xuanyu Ren, Fangfei Li, Bing Xue

Abstract

In this experiment, The TiO2/illite composites were synthesized by a simple hydrothermal method, taking Ti(SO4)2 as Ti precursor and illite as substrate. The as-prepared composites were characterized by XRD, FT-IR, BET, SEM, TEM and photocatalytic performance. The results show that TiO2 particles do not enter the interlayer of the illite because the (0 0 1) diffraction peak of illite in the composites does not shift. Illite and TiO2 are connected by Si-O-Ti and Al-O-Ti bond and the presence of illite can inhibit the transition from anatase to rutile. Moreover, the dispersion of TiO2 particles in the composite is obviously improved. When the pH value is 1.5, the photocatalytic performance of the composites is the best. The degradation rate of methyl orange (MO) solution can reach 73.4% after 8 h visible light irradiation and 93.6% after 40 min ultraviolet light irradiation, which is better than P25.

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One-step hydrothermal synthesis of SnO<sub>2</sub>-MoS<sub>2</sub> composite heterostructure for improved visible light photocatalytic performance

Publication date: 1 September 2019

Source: Chemical Physics, Volume 525

Author(s): Xiao Ni, Changzhao Chen, Qian Wang, Zhe Li

Abstract

The formation of a heterostructure in a photocatalyst is considered to be an effective method for improving photocatalytic performance. In this paper, the SnO2-MoS2 heterostructures are synthesized by a simple one-step hydrothermal method. The structure, composition and morphology of the samples are characterized by XRD, XPS, SEM, (HR)TEM, and Raman spectroscopy. The photocatalytic performance of the samples are judged by the degradation of two dyes, i.e., methylene blue (MB) and rhodamine B (RhB), under visible light. The photocatalytic performance of all composite samples is better than that of pure MoS2 or SnO2. In particular, 60% SnO2-MoS2 has the best photocatalytic performance, which is characterized by its large degradation rate to pollutants and excellent reusability. The high-efficiency photocatalytic activity of the SnO2-MoS2 heterostructure is due to the high specific surface area and enhanced absorption of visible light in its composite structure, which effectively improves the separation of electron-hole pairs.

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Structural, optical and magnetic properties of cobalt doped hematite nanoparticles

Publication date: 1 September 2019

Source: Chemical Physics, Volume 525

Author(s): Houda Mansour, K. Omri, Saleh Ammar

Abstract

Pure α-Fe2O3 and Co-doped α-Fe2O3 (CFO) nanoparticles were synthesized by Co-precipitation method. The structure and the morphology of the samples were characterized by X-ray diffraction (XRD), Raman spectroscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM), UV–visible diffuse reflectance spectroscopy (DRS), and a vibrating sample magnetometer (VSM). The results showed that CFO nanoparticles have rhombohedral structure and that the Co2+ ions were well incorporated into the α-Fe2O3 crystal lattice, which are consistent with the results obtained from Raman spectroscopy. The crystallite sizes were in the range 36–38 nm, which are consistent with the results obtained from TEM and SEM images. Meanwhile, the Co doping could extend the visible light absorption of α-Fe2O3 nanoparticles. Furthermore, magnetic investigations demonstrate that magnetic properties strongly depend on doping content.


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Label-free measurements on the solution of monomeric and dimeric insulin using a periodical terahertz split ring resonator

Publication date: 1 September 2019

Source: Chemical Physics, Volume 525

Author(s): Pengfei Wang, Liyuan Liu, Xiangchao Wang, Jianbing Zhang, Wei Qi, Hongwei Zhao, Zhen Tian, Mingxia He

Abstract

A silicon-based sensor, consisting of periodical split ring resonators was demonstrated to monitor monomeric and dimeric insulin solutions in terahertz time-domain spectroscopy (THz-TDS). As concentration increases, the resonant frequencies of sensor show red shifts with a rapid trend in dilute solutions and a slow trend in concentrated solutions, consistent with CST simulations. For monomeric insulin, the turning concentration is 11.6 mg/ml and the total frequency shift is larger than that of dimeric insulin which shows a turning concentration at 17.4 mg/ml. The deviation in frequency shift and turning concentration can be attributed to the structural changes of insulin during dimerization process.


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Visualising the role of non-perturbative environment dynamics in the dissipative generation of coherent electronic motion

Publication date: 1 September 2019

Source: Chemical Physics, Volume 525

Author(s): A.W. Chin, E. Mangaud, V. Chevet, O. Atabek, M. Desouter-Lecomte

Abstract

Targeted exciton transport is crucial for efficient light-harvesting, but its microscopic description in biological systems is complicated by strong environmental coupling, highly structured vibrational environments and non-Markovian open system dynamics. In this article we employ the non-perturbative hierarchical equations of motion (HEOM) technique to explore how structured environments and tuned electronic properties can lead to the generation of coherent motion across a directed transport network, i.e. one containing an energy gradient. By further exploiting the information contained in the auxiliary HEOM matrices, we also visualize the complete displacement distributions of the main reaction coordinate during the ultrafast relaxation, and show that highly non-Gaussian profiles emerge when the electronic dynamics become quasi-reversible and involve bath-induced delocalized states. These coherent dynamics are spontaneously generated by earlier incoherent relaxation events, and we also demonstrate the correlation between the environmental coordinates and a quantitative volume-based measure of non-Markovianity.


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Linear and nonlinear Herzberg−Teller vibronic coupling effects. II: Hole-burning and fluorescence line narrowing spectroscopy

Publication date: 1 September 2019

Source: Chemical Physics, Volume 525

Author(s): Mohamad Toutounji

Abstract

Part I of this series showed that Herzberg-Teller vibronic coupling manifests itself in linear spectroscopy through the breakdown of the mirror image symmetry between the absorption and emission spectra, whereby a nuclear exponential function was used to represent the molecular electronic transition dipole moment. This part tests the applicability of the framework developed in Paper I to absorption-emission asymmetry in nonlinear signals such as hole-burned and fluorescence line narrowed spectra. Model calculations of nonlinear absorption and emission spectra showing asymmetry is provided. Hole-burning and fluorescence line narrowing signals are to exemplify nonlinear absorption and emission spectra so as to reveal the anticipated asymmetry in 4-wave mixing experiments, and probe the consequent zero-phonon hole and the phonon-sideband hole. These calculations prove to be efficient and fast, exhibiting remarkable numerical stability. The observation of richer phonon-side band (PSB) in linear spectra, phono-side band hole (PSBH) in Hole-burning and fluorescence line narrowing signals, and emergence of new quantum beats over longer time scale (despite the dissipative medium) under the non-Condon regime are linked to the long quantum coherence phenomenon and stimulated photon peak shift in photosynthetic systems.


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Theoretical investigation of storage capacity of hydrocarbon gas in sH hydrate

Publication date: 1 September 2019

Source: Chemical Physics, Volume 525

Author(s): Jinxiang Liu, Youguo Yan, Jun Zhang, Jiafang Xu, Gang Chen, Jian Hou

Abstract

Hydrates are considered an excellent approach for transporting and storing natural gas. In this study, the structural properties and stability of sH hydrates with the inclusion of different hydrocarbon molecules were investigated by performing density functional theory (DFT) calculations and ab initio molecular dynamics (AIMD) simulations. The small and medium cages can encapsulate one methane molecule per cage. The large cage is likely to encapsulate the long straight-chain hydrocarbon molecules than the small hydrocarbon molecules, and the optimum cage occupancy is four methane molecules, three ethane molecules, two propane molecules, two butane molecules, and one pentane molecule, respectively. The presented results provide a much needed molecular insights of sH hydrates and are helpful to promote the development of the hydrate technology for the storage and transport of natural gas.

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BH<sub>x</sub><sup>+</sup> (x = 1–6) clusters: In the quest for superalkali cation with B-core and H-ligands

Publication date: 1 August 2019

Source: Chemical Physics, Volume 524

Author(s): Ambrish Kumar Srivastava

Abstract

In the quest for non-metallic superalkali cation without an electronegative core, we investigate BHx+ clusters (x = 1–6) using MP2/6-311++G(d,p) calculations. We noticed that these BHx+ cations are stable against dissociation into BHx−1 + H+ and BHx−2+ + H2 fragments. The vertical electron affinity (EAv) values suggest that BH6+ cluster indeed behaves as a superalkali cation with EAv of 2.94 eV, lower than the IE of Cs atom. The atomic charges reveal that B contains negative charge due to electron transfer from H-ligands. The kinetic stability of BH6+ is confirmed by ab initio molecular dynamics simulations with 1 ps trajectory at various temperatures. We have also demonstrated that BH6+ superalkali cation can, in principle, be synthesized by using double protonation of BH4 superhalogen anion. Nevertheless, we have also studied AlH6+ and GaH6+ cations, whose EAv values are larger than that of BH6+ but smaller than the IE of the Li atom.

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Superior photocatalytic activity of Cu doped NiWO<sub>4</sub> for efficient degradation of benzene in air even under visible radiation

Publication date: 1 September 2019

Source: Chemical Physics, Volume 525

Author(s): Nguyen Le Minh Tri, Dao Sy Duc, Doan Van Thuan, Talal Al Tahtamouni, Thanh-Dong Pham, Dinh Trinh Tran, Nguyen Thi Phuong Le Chi, Van Noi Nguyen

Abstract

We effectively used Cu dopant to improve photocatalytic performance of NiWO4 to remove benzene in air. The obtained experimental result indicated that photocatalytic performance of the prepared Cu-NiWO4 materials were greater than that of the pure NiWO4. This was because Cu effectively acted as novel dopant, which not only affected valence band (VB) top and conduction band (CB) bottom of NiWO4 but also formed a medium energy level between CB and VB of the NiWO4 to decrease its energy band gap and electron-hole recombination rate. Hence, the photocatalyst produced large available charge amounts (electron and hole) initiating photocatalysis for degradation of gaseous benzene. The optimized Cu/Ni mole ratio for maximum improving photocatalytic performance of NiWO4 was 3%. The maximum benzene removal efficiency and its mineralization via visible light photocatalysis of the 3Cu-NiWO4 were 93.7 and 96.5%, respectively. The synthesized Cu-NiWO4 photocatalyst also presented great stability in benzene removal processes.

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Optical and luminescence characteristics of europium doped barium lithium fluoroborate glasses

Publication date: 1 September 2019

Source: Chemical Physics, Volume 525

Author(s): K. Mariselvam, R. Arun Kumar, S. Karthik

Abstract

This is a report on the synthesis and spectroscopic study of europium doped barium lithium fluoroborate glasses (Eu3+:BLFB) by conventional melt quenching technique and their structural and luminescence characteristics. The X-Ray diffraction result confirms the amorphous nature of the glasses. The Judd-Ofelt parameters (Ω2, Ω4, Ω6) were calculated from the emission spectra and the trends in the intensity parameters are found to be Ω2 > Ω4 > Ω6. The JO parameters were used to predict the radiative properties like transition probability, branching ratio, radiative lifetime and stimulated emission cross section for all the emission levels of europium (Eu3+) ions. Phonon energy (1228 cm−1) have been calculated from the phonon side band spectra. From the emission spectra, fluorescence intensity ratio (R), color chromaticity values were calculated and x, y parameters which indicates the emission of red color, as observed in the in the CIE diagram. The nature of decay profiles of 5D0 state of Eu3+ in all glasses were measured and were compared with the calculated lifetimes.

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Understanding of structures, dynamics, and hydrogen bonds of imidazolium-based ionic liquid mixture from molecular dynamics simulation

Publication date: 1 September 2019

Source: Chemical Physics, Volume 525

Author(s): Xueping Wang, Fangjia Fu, Kuilin Peng, Zhen Yang, Na Hu, Xiangshu Chen, Wei Li

Abstract

Here we employ molecular dynamics simulation to study structures, dynamics, and hydrogen bonds of the imidazolium-based ionic liquid mixture, which consists of equimolar [Emim][BF4] and [Bmim][BF4]. Our simulation results demonstrate that the imidazolium rings of both different cations almost show identical structures with [BF4] anions regardless of the alkyl chain length. Meanwhile, both kinds of cations almost display the same association/dissociation dynamics with anions. By comparison, the order of diffusion speed is [Emim]+ > [Bmim]+ > [BF4] while that of rotation speed is [BF4] > [Emim]+ > [Bmim]+ in the ionic liquid mixture. By analyzing the average numbers of hydrogen bonds (HBs) and the relevant HB dynamics between cations and anions, we find that [Bmim]+ cations have more and stronger HBs with anions than [Emim]+ cations, which should be partly responsible for slower diffusion and rotation of [Bmim]+ cations than those of [Emim]+ cations. Therefore, this simulation study provides a molecular-level understanding of the role of alkyl chain and HB on the relevant structure and dynamics properties in the imidazolium-based ionic liquid mixture.

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Exploring reactive species of chlorocarbons and oxygen atom generation at low temperatures using electron gun assembly

Publication date: 1 September 2019

Source: Chemical Physics, Volume 525

Author(s): N. Ramanathan, K. Sundararajan, Shubhra Sarkar, P.K. Sruthi

Abstract

The study of reactive species remains a challenge under ambient conditions owing to their extremely shorter life times. The advent of technique of matrix isolation changed the scenario as the reactive species produced will have a long life time due to the cage effect of matrixes and low temperatures. Of many possible routes for the generation of reactive species, electron impact seems to be very attractive as the tunability of electron energy results in the selective fragmentation of the bonds. In this work, the electron gun assembly developed in house for the generation of reactive species was coupled with matrix isolation infrared facility for trapping and studying the species under the influence of matrixes. The reactive species formed out of chlorocarbons were investigated. Subsequently, the feasibility of producing nascent oxygen atoms and ozone through electron bombardment of O2 molecule was investigated with a special emphasis on ‘dark’ oxidation.


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Heteroatoms (N-, Si-) self-doped spongy carbon derived from wild fungus sharia bambusicola as electrode materials for supercapacitors

Publication date: 1 September 2019

Source: Chemical Physics, Volume 525

Author(s): Xinran Hu, Jiangfeng Li, Yan Zhang, Qingsheng Wu, Gengshou Xia

Abstract

Heteroatoms (N-, Si-) self-doped spongy carbon material was synthesized for the first time via activation and carbonization of sharia bambusicola. Due to the hierarchical porous nature and heteroatom doping efforts, the obtained materials show a high specific capacitance (339 F g−1 at 0.5 A g−1), superior rate stability (75% capacitance retention at the range of 0.5 to 50 A g−1) and long cycle period (98% capacitance retention over 5000 cycles).

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Schematic diagram of wild bamboo parasitic fungus derived spongy-like carbon with heteroatoms (N, Si) doping via KOH activation and carbonization for supercapacitors.

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Morphological and photophysical study in hybrid ternary organic nanoparticles blends

Publication date: 1 September 2019

Source: Chemical Physics, Volume 525

Author(s): Anubhav Raghav, Mrinmoy Kumar Chini, Amarnath Bheemaraju, Rajashik Paul, Soumitra Satapathi

Abstract

The electron donor-acceptor based hybrid ternary nanostructures remains a frontier area of research in designing novel light harvesting devices. Here we report the morphological and photophysical study in Intra-triad and Inter-triad nanoparticles by using electron donating donor-acceptor-donor (D-A-D) type Diketopyrrolopyrrole (DPP) molecule which imparts the advantages of both polymers and small molecules and non fullerene electron acceptor, Naphthalene diimide (NDI) and fullerene based acceptor, Phenyl-C61-butyric acid methyl ester (PCBM). Both these nanostructures were fabricated by modified mini-emulsion technique. The Intra-triad nanostructure contains DPP, NDI and PCBM molecules inside the same matrix and in case of Inter-triad nanostructure, individual nanoparticles are attached together by electrostatic force. The morphological optimizations in hybrid nanostructures are performed with the help of AFM studies. We have further studied the structure mediated charge transfer phenomena and lifetime decay profiles by time resolved photoluminescence and steady state spectroscopy measurements. Due to the favorable energy levels, DPP molecules have been employed here as donor molecule for cascade energy transfer in ternary heterotriad geometric system. We have further studied the structure mediated charge transfer phenomena and lifetime decay profiles by time resolved photoluminescence and steady state spectroscopy measurements. Due to the favorable energy levels, DPP molecules have been employed here as donor molecule for cascade energy transfer in ternary heterotriad geometric system. The steady state and time resolved spectroscopy reveal interesting photophysics about the ternary heterostructures. The Intra-triad system has shown improved charge transfer properties compared to Inter-triad system and could be a futuristic material for opto-electronic applications.

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Electrical conductivity of undoped bilayer Graphene: Beyond nearest neighbor approximation

Publication date: 1 September 2019

Source: Chemical Physics, Volume 525

Author(s): Afsaneh Abbasi, Hamed Rezania

Abstract

We have addressed density of states and electrical conductivity of undoped biased bilayer graphene for both AA and AB stacking in the context of tight binding model hamiltonian. The effects of next nearest neighbor hopping amplitude for electrons and gap parameter on electronic density of states and electrical conductivity have been investigated. Green’s function approach has been implemented to find the behavior of electrical conductivity of bilayer graphene within linear response theory. We have found the temperature dependence of electrical conductivity for different values of gap parameter and bias voltage in the presence of neat nearest neighbor hopping integral. Our results for density of states of bilayer graphene in the presence of gap parameter show the increase of bias voltage reduces the band gap width. Also a peak in the dependence of thermal conductivity on temperature has been observed for all physical parameters. An anisotropic behavior for electrical conductivity of unbiased simple bilayer graphene in the presence of gap parameter has been resulted.


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Self-assembly of doxorubicin and a drug-binding peptide studied by molecular dynamics

Publication date: 1 September 2019

Source: Chemical Physics, Volume 525

Author(s): Gergana Gocheva, Kalina Peneva, Anela Ivanova

Abstract

A promising approach when developing efficient drug-delivery systems is to utilize a single carrier loaded with several drug molecules. Drug-binding peptides can be used as such transporters. However, knowledge about the microscopic mechanism of the self-assembly is needed. To unveil it, the behavior of a complex between an experimentally tailored drug-binding peptide (DBP) and the chemotherapeutic doxorubicin (DOX) is investigated via molecular dynamics. Simulations of one peptide and five DOX molecules in aqueous solution at room and body temperature are carried out. In all cases multiple DOXs bind spontaneously to the transporter, matching the expressed experimental affinity of the drug for the peptide. Aggregates form fast either stepwise, or by attaching preformed DOX associates. Tryptophan and tyrosine are key for the attachment, the dominant DBP-DOX interaction is π-stacking. Considering this, DBP can be outlined as a prospective drug-carrying unit with enhanced potential for binding π-conjugated drugs.

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Colloidal stability of silica and graphite in aqueous suspensions

Publication date: 1 September 2019

Source: Chemical Physics, Volume 525

Author(s): Lingyun Liu, Miguel Angel Gonzalez-Olivares, Haoyu Bai, Hao Yi, Shaoxian Song

Abstract

In order to investigate the effect of surface wettability on colloidal stability, aggregation/dispersion behaviors of fine silica and graphite in aqueous suspensions have been investigated. It was found that hydrophobic graphite particles showed a high aggregation degree in low pH suspensions, while it showed very low aggregation degree in high pH suspensions due to the strong electrostatic repulsions between graphite particles. On the other hand, silica particles showed stable dispersion behaviors even under strong Van der Waals attraction in low pH suspensions, which could not be explained by DLVO theory. Solvation factor on hydrophilic silica particles was applied to prove the strong hydration of silica, and it is the hydration repulsion forces among silica particles that determined the stable dispersion of silica particles in a wide pH range. Therefore, it was concluded that hydration layers formed on hydrophilic mineral surfaces played an important role in colloidal stability.


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Source: Chemical Physics, Volume 524

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Preface

Publication date: 1 August 2019

Source: Chemical Physics, Volume 524

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The effect of impurity on the separation of CO<sub>2</sub> from N<sub>2</sub> by MCM-41: A simulation study

Publication date: 1 August 2019

Source: Chemical Physics, Volume 524

Author(s): Saeed Khoshhal Salestan, Majid Taghizadeh

Abstract

Pure CO2 and N2 adsorption isotherms on MCM-41 were simulated by Grand Canonical Monte Carlo method. The results showed a reasonable agreement with literature reported data. The CO2/N2 selectivity was determined for the pure phase and binary mixture. Nevertheless, competitive adsorption improved the selectivity but decreased adsorption amount of each gas. The effect of impurity on CO2/N2 selectivity was also simulated in a ternary mixture in the presence of water, NO2, and SO2 molecules. Also, an isosteric heat calculation and radial distribution function analysis were performed to prove that the water molecules interact more with MCM-41 than other gases.

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Effect of addition of cerium (III) nitrate hexahydrate on gamma ray interaction properties in acetone at various gamma energies obtained by Compton scattering technique

Publication date: 1 September 2019

Source: Chemical Physics, Volume 525

Author(s): Mohinder Singh, Akash Tondon, Bhajan Singh, B.S. Sandhu

Abstract

The objective of the present work is to assign radiation interaction parameters to the solutions of cerium (III) nitrate hexahydrate [(Ce(NO3)3.6H2O)] in different concentrations dissolved in acetone [(CH3)2CO]. The photons scattered from cylindrical aluminum target result in secondary photon beam of desired energy and were detected using 2″ × 2″ NaI(Tl) scintillation spectrometer. The results show a decrease in mass attenuation coefficient (μm), effective atomic number (Zeff) and Electron density (Nel) with the increasing gamma photon energies and decreasing concentrations. The values of Computed tomography (CT) number, interpreters of CT scan, are found to be increasing linearly with increase in concentration and exponentially with increase in Zeff. These results show a good agreement with the theoretical values obtained from WinXCom.

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Combined temperature- and magnetic field-induced optical responses of phosphorene

Publication date: 1 August 2019

Source: Chemical Physics, Volume 524

Author(s): Doan Quoc Khoa, Tran Cong Phong, Vo Thanh Lam, Bui Dinh Hoi

Abstract

The paper presents a theoretical investigation of the temperature and an out-of-plane Zeeman magnetic field effects on the interband optical conductivity of phosphorene. The electronic states are calculated with the tight-binding Hamiltonian and to compute the optical conductivity, the Kubo formalism is employed. The main result is that the multiple bands due to the perpendicular Zeeman splitting of the energy levels lead to the multiple resonance structures of the optical conductivity. It is found that the strong anisotropic interband optical conductivity of pristine phosphorene keeps the anisotropic feature when the temperature is increased. Importantly, our results show that the optical properties can be externally tuned via a magnetic field. In particular, when the magnetic field is applied, the unique anisotropic property breaks down and there is a little to no sign for temperature- and orientation-dependent transitions. The scientific soundness of findings is useful for practical aspects of phosphorene in spintronic.


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A DFT approach for theoretical and experimental study of structure, electronic, Hirshfeld surface and spectroscopic properties of 12-(4-bromophenyl)-2-(prop-2-ynyloxy)-9,10-dihydro-8<em>H</em>-benzo[<em>a</em>]xanthen-11(12<em>H</em>)-on single crystal

Publication date: 1 August 2019

Source: Chemical Physics, Volume 524

Author(s): Harjinder Singh

Abstract

Xanthene-propargyl derivative was synthesized by multicomponent reaction and was characterized by SCXRD analysis. Structure was optimized to ground state using DFT calculations at the B3LYP/6-311++G(d, p) level of theory in gas phase and in solvent. NBO analysis was performed at same level of theory. The vibrational spectrum was obtained theoretically by DFT calculations; vibrational assignments were made to different vibrational modes using potential energy distribution (PED) method. The non-covalent interactions present in molecule were investigated with Hirshfeld surface and fingerprint plots analysis, shape index, and curvedness using SCXRD data while theoretically these interactions were investigated using reduced density gradient (RDG) method. MEP surface was also analyzed and chemical reactivity descriptors were calculated theoretically. FMO and TDOS analysis was performed to study energy and distribution of molecular orbitals. NLO analysis was performed to determine its ability to act as potential NLO material. The high value of molar refractivity was also calculated theoretically.

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Editorial Board

Publication date: 1 August 2019

Source: Chemical Physics, Volume 524

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Extensive stacking of DHI-like monomers as a model of out-of-plane complexity in eumelanin protomolecules: Chemical and structural sensitivity of optical absorption spectra

Publication date: 1 August 2019

Source: Chemical Physics, Volume 524

Author(s): Elena Molteni, Giancarlo Cappellini, Giovanni Onida, Guido Mula

Abstract

In this work, we study the optical absorption spectra of extensive stacking forms of four molecules known to be among eumelanin basic building blocks: 5,6-dihydroxyindole (DHI), 5,6-dihydroxyindole-2-carboxylic acid (DHICA), indolequinone (IQ) and quinone-methide (MQ). Stacked monomers can be considered as a minimal model of out-of-plane complexity in eumelanin, as complementary to in-plane oligomerization. The choice of a plane wave density functional theory (DFT) approach allows us to address extensive, i.e. several-layer, stacking of these DHI-like monomers at a relatively low computational cost, by treating stacked systems as periodic along the stacking direction. Absorption spectra of stacked monomers display interesting trends in terms of chemical and structural sensitivity, which can shed light on the role of extensive stacking in the transition from the optical properties of small molecules such as DHI to the typical broadband and monotonic absorption spectrum of the eumelanin pigment.


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The effects of the applied current and the measurement temperature on the negative differential resistance behaviour of carbonized xerogel

Publication date: 1 August 2019

Source: Chemical Physics, Volume 524

Author(s): I. Najeh, L. El Mir

Abstract

Electrical properties of carbonised organic xerogel based on resorcinol–formaldehyde (RF), prepared by pyrolysis at 675 °C in nitrogen atmosphere for two hours, were investigated. In this temperature an insulator to semiconductor-like transition occurs. The voltage–current (V–I) characteristics indicate the presence of non-linear conductivity depending on the measurement temperature. The origin of the non-linearity in the electrical conductivity is discussed using different theoretical models. The obtained results reveal that this non-linear conductivity starts above a threshold current, which is illustrated by the presence of negative differential resistance (NDR) region. The properties of the obtained NDR are controlled by the applied current and are attributed to a percolation phenomenon in the carbonised sample. The obtained result is very promising for many applications in power electronic technology specially for the development of some negatronic devices.

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Electrical properties of carbonised organic xerogel based on resorcinol-formaldehyde (RF), prepared by pyrolysed at 675 °C in nitrogen atmosphere for two hours, were investigated. The voltage–current (V–I) characteristics indicate the presence of non-linear conductivity depending on the measurement temperature. The origin of the non-linearity in the electrical conductivity is discussed using different theoretical models. The obtained results reveal that this non-linear conductivity starts above a threshold current, which is illustrated by the presence of a region of negative differential resistance (NDR). The properties of the obtained NDR are controlled by the applied current and are attributed to a percolation phenomenon in the carbonised sample. The obtained result is very promising for many applications in power electronic technology specially for the development of some negatronic devices.

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Investigation into the molecular and electronic structures of a newly synthesized <em>o</em>-quinone derivative

Publication date: 1 August 2019

Source: Chemical Physics, Volume 524

Author(s): Nobutsugu Hamamoto, Sachie Arae, Tetsuji Moriguchi, Ryo Irie, Hitoshi Fujimoto

Abstract

We studied on the geometric and electronic structures of a newly synthesized compound, 3-(tert-butyl)dinaphtho[1,2-b;1′,2′-d]furan-12,13-dione (1), having a twisted molecular structure at an o-quinone region in a crystal. The density functional theory (DFT) has been applied to investigate the geometric and electronic structures using the model compound (1H), where a tertiary butyl group of the compound 1 is replaced by a hydrogen atom. The optimized geometry for the model dimer of 1H represented well the twisted molecular structure of 1. The time-dependent DFT method explained the observed optical properties of 1 in a solution and a powdery solid. The DFT calculations also gave a good estimation of the ionization potential and the electron affinity of 1H, explaining a similarity in reduction and a difference in oxidation between 1H and o-benzoquinone. This similarity in the electron affinity was confirmed by measuring a reduction potential of the compound 1 with cyclic voltammetry.

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Photochemical reaction mechanisms of 4,5-dimethoxy-2-nitrobenzyl acetate analysed by a sub-10 fs near-ultraviolet pulse laser

Publication date: 1 August 2019

Source: Chemical Physics, Volume 524

Author(s): Sena Hashimoto, Kenta Hamada, Izumi Iwakura, Atsushi Yabushita, Takayoshi Kobayashi, Hirotaka Fujita, Kento Takeda, Yuta Ono, Noriko Chikaraishi Kasuga, Kazuo Yamaguchi

Abstract

The present study examined the electronic dynamics of 4,5-dimethoxy-2-nitrobenzyl acetate after π-π* excitation. Pump-probe measurement using a near-ultraviolet sub-10 fs pulse laser revealed that the lifetime of the S*(π-π*) state is 500 fs after photoexcitation to produce the S*(n-π*) state and that the lifetime of the S*(n-π*) state is 1000 fs. By studying different alpha substituents, the lifetimes of the S*(π-π*) state and the S*(n-π*) were found to be independent on the alpha substituents.

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Evidences for phase transition and metallization in <em>β</em>-In<sub>2</sub>S<sub>3</sub> at high pressure

Publication date: 1 August 2019

Source: Chemical Physics, Volume 524

Author(s): Kaixiang Liu, Lidong Dai, Heping Li, Haiying Hu, Linfei Yang, Chang Pu, Meiling Hong

Abstract

The high-pressure characteristics including structural phase transition, vibration and electronic transport of β-In2S3 up to 43.0 GPa are determined using a diamond anvil cell (DAC) combined with AC impedance spectroscopy, Raman spectroscopy, atomic force microscopy (AFM) and high-resolution transmission electron microscopy (HRTEM). A structural phase transition and a semiconductor-to-metal transition are observed at ∼7 GPa and ∼41.2 GPa, respectively. When the pressure is released from 43.0 GPa, a single amorphous state is observed from Raman spectroscopy. We determine that the phase transition of metallization is irreversible after decompression from the pressure above 40 GPa. However, when the sample is decompressed from the pressure below 10 GPa, the phase transition is reversible. The unique properties displayed by β-In2S3 under different experimental pressure ranges can be reasonably explained by its crystalline structure observable from the microscopic observations of HRTEM and AFM images.


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Structures of clusters surrounding ions stabilized by hydrogen, halogen, chalcogen, and pnicogen bonds

Publication date: 1 August 2019

Source: Chemical Physics, Volume 524

Author(s): Steve Scheiner, Mariusz Michalczyk, Wiktor Zierkiewicz

Abstract

Four H-binding HCl and HF molecules position themselves at the vertices of a tetrahedron when surrounding a central Cl. Halogen bonding BrF and ClF form a slightly distorted tetrahedron, a tendency that is amplified for ClCN which forms a trigonal pyramid. Chalcogen bonding SF2, SeF2, SeFMe, and SeCSe occupy one hemisphere of the central ion, leaving the other hemisphere empty. This pattern is repeated for pnicogen bonding PF3, SeF3 and AsCF. The clustering of solvent molecules on one side of the Cl is attributed to weak attractive interactions between them, including chalcogen, pnicogen, halogen, and hydrogen bonds. Binding energies of four solvent molecules around a central Na+ are considerably reduced relative to chloride, and the geometries are different, with no empty hemisphere. The driving force maximizes the number of electronegative (F or O) atoms close to the Na+, and the presence of noncovalent bonds between solvent molecules.

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First-order transitions in glasses and melts induced by solid superclusters nucleated and melted by homogeneous nucleation instead of surface melting

Publication date: 1 August 2019

Source: Chemical Physics, Volume 524

Author(s): Robert F. Tournier

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Supercooled liquids give rise, by homogeneous nucleation, to solid superclusters acting as building blocks of glass, ultrastable glass, and glacial glass phases before being crystallized. Liquid-to-liquid phase transitions begin to be observed above the melting temperature Tm as well as critical undercooling depending on critical overheating ΔT/Tm. Solid nuclei exist above Tm and melt by homogeneous nucleation of liquid instead of surface melting. The Gibbs free energy change predicted by the classical nucleation equation is completed by an additional enthalpy which stabilize these solid entities during undercooling. A two-liquid model, using this renewed equation, predicts the new homogeneous nucleation temperatures inducing first-order transitions, and the enthalpy and entropy of new liquid and glass phases. These calculations are successfully applied to ethylbenzene, triphenyl phosphite, d-mannitol, n-butanol, Zr41.2Ti13.8Cu12.5Ni10Be22.5, Ti34Zr11Cu47Ni8, and Co81.5B18.5. A critical supercooling and overheating rate ΔT/Tm = 0.198 of liquid elements is predicted in agreement with experiments on Sn droplets.

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Ethylbenzene enthalpy Δεig × ΔHm below Tm = 178.1 K. Undercooled Phase 3 enthalpy coefficient Δεig versus (T − 178.1)2/178.12 in a two-liquid model; Δεig × ΔHm being the enthalpy difference between those of Liquid 1 and Liquid 2. Phase 3 undergoes a first-order transition at TK2 = 104.7 K in the absence of glass transition at Tg = 114.5 K and its enthalpy coefficient cannot be lower than (−0.17855). An underlying first-order transition limits the relaxation enthalpy and fixes the first-order transition temperatures of ultrastable glasses. Phase 3 undergoes other first-order transitions at higher temperatures associated glacial, superheated and supercooled phases in various substances.


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Water-mediated weakening of inter-ionic interactions in aqueous mixtures of ionic liquid: An investigation combining quantum chemical calculations and molecular dynamics simulations

Publication date: 1 August 2019

Source: Chemical Physics, Volume 524

Author(s): Sukanya Konar, Anirban Sharma, Swarup Banerjee, Pradip Kr. Ghorai, Ranjit Biswas

Abstract

Quantum chemical calculations and molecular dynamic simulations have been performed to understand the structure and energetics of ionic liquid (IL) in presence of water. Addition of water is found to induce charge flow from the anion to cation, reducing the strength of the electrostatic interactions between the ion-pair without changing the interionic distance. Composition dependent isotropic (α0) and anisotropic (αaniso) components of the total polarizability do not show any dependence on the number of water molecules present in the (IL + water) binary mixture. Vibrational density of states for ions obtained from simulated velocity auto correlation function do not show any composition dependence. These provide much-needed explanation for the insensitivity of spectral shift to water concentration reported in OHD-RIKES measurements with IL + water mixtures. Continuous and structural H-bond lifetimes predict a decrease of both with water concentration. This can be understood in terms of concomitant reductions in inter-ionic electrostatic interactions and solution viscosity.

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A simulation of free radicals induced oxidation of dopamine in aqueous solution

Publication date: 1 August 2019

Source: Chemical Physics, Volume 524

Author(s): Branislav Milovanović, Jelica Ilić, Ivana M. Stanković, Milana Popara, Milena Petković, Mihajlo Etinski

Abstract

Understanding the basic chemistry between highly reactive free radicals and dopamine is an important step in characterizing the antioxidative activity of catecholamine neurotransmitters. In this work, we simulated the reactions between dopamine and hydroxyl, peroxyl and methoxy radicals in aqueous solution by employing first principle molecular dynamics based on density functional theory and the BLYP functional. The simulations provide mechanistic insight into the reaction mechanisms but underestimate reaction timescales. The failure of the BLYP functional to address the formal hydrogen atom transfer barriers between dopamine and free radicals is attributed to the self-interaction error.

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Energy separation calculations of the vibrational ground state in the Jahn-Teller E ⊗ e system and application to nitrate radical

Publication date: 1 August 2019

Source: Chemical Physics, Volume 524

Author(s): Kohei Tada

Abstract

We perform numerical calculations of the vibrational ground state in the Jahn-Teller E ⊗ e molecular system with a strong quadratic coupling by the Wentzel-Kramers-Brillouin method and obtain three allowed energies by treating the adiabatic potential energy surface of this system as that of a hindered rotor. These three vibrational energies correspond to a non-degenerated “ground state” and a doubly-degenerated “first excited state”. We obtain the relationship among the three quantities, namely, the height of potential barriers of the hindered rotor, the moment of inertia of the hindered rotor and the energy separation between “the ground state” and “the first excited state.” Based on the calculations, the experimentally detected splittings of the spin-orbit components in the B2E′ (v = 0) state of nitrate radical is well explained to be due to the Jahn-Teller effect. The stabilization energy due to the Jahn-Teller effect for the B2E′ state is calculated to be about 4000 cm−1.

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Effects of the inter- and intra-molecular hydrogen bonding interactions in forming atmospheric malonic acid-containing clusters

Publication date: 1 August 2019

Source: Chemical Physics, Volume 524

Author(s): Xia Sheng, Xue Song, Huina Zhu, Cleopatra Ashley Ngwenya, Hailiang Zhao

Abstract

The possible involvement of chemical compounds in atmospheric new particle formation has received increased attention in recent years. Extensive density functional theory calculations were performed to characterize the effects of the inter- and intra-molecular hydrogen bonding interactions in forming atmospheric malonic acid (MOA)-containing clusters. Methanol, water, formaldehyde, and acetone are common atmospheric nucleation precursors, and they were chosen as the counterpart to interact with MOA. There are two types of hydrogen bonds: addition and insertion. When MOA behaves as the donor of a hydrogen bond, the formation of an inter-molecular hydrogen bond lightly increases the strength of the intra-molecular hydrogen bonds. Strong hydrogen bonds were formed when MOA executes as a hydrogen bond donor. The strength of the insertion conformer depends on the inserting molecule. The IR frequencies of the hydrogen bonded system were investigated. Furthermore, geometrically identified inter- and intra-molecular hydrogen bonds were provided by atoms in molecules approach.

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The study of mechanical and thermoelectric behavior of MgXO<sub>3</sub> (X = Si, Ge, Sn) for energy applications by DFT

Publication date: 1 August 2019

Source: Chemical Physics, Volume 524

Author(s): Q. Mahmood, M. Yaseen, Bakhtiar Ul Haq, A. Laref, Aalia Nazir

Abstract

Magnesium-based perovskites are being investigated for their electronic, mechanical, and thermoelectric properties using density functional theory and Boltzmann transport theory. The structural, thermodynamic, and mechanical stabilities of MgSiO3, MgGeO3 and MgSnO3 are confirmed by tolerance factor (0.93–1.0 the stability range for cubic structure), enthalpy of formation, and Born mechanical stability criteria, respectively. The ductile nature of studied materials has been explored by Pugh’s (B/G > 1.75) and Poisson (υ > 0.26) ratios. The studied compounds are indirect bandgap semiconductors having band gap range 2.5 eV to 0.7 eV and, correspondingly, their thermoelectric properties are modified. The small values of σ/κ ratio and large values ZT (0.57, 0.66, and 0.67) at room temperature make them suitable for thermoelectric applications.


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Tuning the electronic properties of GaS monolayer by strain engineering and electric field

Publication date: 1 August 2019

Source: Chemical Physics, Volume 524

Author(s): Khang D. Pham, Vo T.T. Vi, Doan V. Thuan, Nguyen V. Hieu, Chuong V. Nguyen, Huynh V. Phuc, Bui D. Hoi, Le T.T. Phuong, Nguyen Q. Cuong, Dung V. Lu, Nguyen N. Hieu

Abstract

In the present study, the effects of the strain engineering and electric field on electronic properties of the GaS monolayer are investigated by ab initio investigations. Our calculated results demonstrate that the GaS monolayer is a semi-conductor with a large indirect bandgap of 2.568 eV at the equilibrium. In the presence of a biaxial strain, the band structure of the GaS monolayer, especially the conduction band, changes significantly. However, while the effect of compressive strain on the energy gap of the GaS monolayer is quite weak, its energy gap depends strongly on the tensile strain. On the other hand, external electric fields can cause the semiconductor–metal transition in the monolayer. Being able to control electronic properties, especially the occurrence of the semiconductor–metal phase transition, makes the GaS monolayer a prospective material for nanoelectromechanical and nanospintronic applications.


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Theoretical model in cylindrical coordinates to describe dynamic interfacial tension determination with spinning drop tensiometry

Publication date: Available online 25 June 2019

Source: Chemical Physics

Author(s): Yulian Jiang, Changming Zhao, Tiexin Cheng, Guangdong Zhou

Abstract

In this paper, a theoretical model in cylindrical coordinates is presented to describe the behavior of dynamic interfacial tension (DIFT) between the oil and water phases. The equation of DIFT is derived from mathematical derivation combined with Gibbs equation. The DIFTs of three sodium alkylbenzene sulfonates (p-S14-5, p-S16-5 and p-S18-5) were studied by the spinning drop technique. It is a function of time and exponential decay is observed. The experimental data are in agreement with the calculated theoretical curves. Meanwhile, the equation predicts that the computable variable (r/2·Ln1-exp-γ-γR·T·Γ should be linear with interphase diffusion time t and its slope depends on the interphase diffusion coefficient K if the assumptions involved in the derivation are valid. The average values and range of the interphase diffusion coefficient K of three surfactants were calculated by applying the slopes from the linear portions.

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Charge Carrier Dynamics Study and Morphology Optimization in Solvent Annealed CH<sub>3</sub>NH<sub>3</sub>PbI<sub>3</sub> Perovskite for Air Processed Stable Solar Cell Application

Publication date: Available online 24 June 2019

Source: Chemical Physics

Author(s): Anubhav Raghav, Shivam Singh, Dhanashree Moghe, Shailendra Sharma, Dinesh Kabra, Soumitra Satapathi

Abstract

We report room temperature excitation intensity dependent charge carrier dynamics in solvent-annealed organo-metal halide perovskite semiconductor CH3NH3PbI3 thin film using steady state and time resolved photoluminescence studies. The average lifetime of these solvent annealed films does not vary significantly with excitation fluence confirming the formation of almost defect free perovskite crystallites. The photocarrier dynamics are well described by a simple rate equation. The local reduction of shallow trap densities as observed in PL dynamics was correlated with scanning electron microscopy (SEM) and X-ray spectroscopy. The observed photophysical investigation and morphology study suggests that anti-solvent method as a potential approach for CH3NH3PbI3 perovskite solar cell fabrication under ambient condition. A prototype all air processed anti-solvent method based stable perovskite device yielded the efficiency of 7.54% with JSC value of 14.21 mA/cm2 and VOC of 810 mV.

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Spin – orbit interaction in Yb<sup>3+</sup> – ground level and nephelauxetic effect in crystals

Publication date: Available online 22 June 2019

Source: Chemical Physics

Author(s): Dimitar N. Petrov, B.M. Angelov

Abstract

The matrix elements of spin – orbit interaction (SOI) have been evaluated for the ground level 2F7/2 of Yb3+ ions in crystals. The dependence of the normalized ratios of SOI relative to the free ion Yb IV – value on the crystal field strength Nv has been found similar to the nephelauxetic effect. The variations with Nv of the nephelauxetic parameter β, maximum splitting of the ground level, and the number of crystal – field parameters have been discussed. The analysis comprises 49 symmetry sites of Yb3+ ions in stoichiometric or doped compounds: complexes with inorganic ligands, simple and complex oxides, halogenides, and semiconductors. A discrepancy has been found between theoretical and experimental values of the maximum splitting in the ground level 2F7/2 of Yb3+ ions in crystals.

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Effects of Phosphate on Drug Solubility Behavior of Mixture Ibuprofen and Lidocaine

Publication date: Available online 21 June 2019

Source: Chemical Physics

Author(s): Hitoshi Chatani, Satoru Goto, Hikaru Kataoka, Momoko Fujita, Yuta Otsuka, Yohsuke Shimada, Hiroshi Terada

Abstract

Drug solubility is an important characteristic affecting its bioavailability. The properties of ionic drugs affect their sensitivity to buffer composition. We aimed to elucidate the variations in ibuprofen solubility due to different buffers and buffer concentrations. We also examined the intermolecular interaction between IBP and lidocaine (LDC) in the presence or absence of phosphate ion to determine whether phosphate in buffer modifies IBP hydration and LDC hydrophobic hydration. The IBP/LDC mixture formed a complex in phosphate buffer, as confirmed by van't Hoff plot and diffusion-ordered NMR spectroscopy, where dissolving behavior changed from endothermic to an exothermic process. This behavior was only achieved in the presence of phosphate ion. We also examined the dependence of a drug’s solubility on the solubility of other drugs. Phosphate ion can greatly affect drug solubility behavior. This knowledge gives us to ensure comparative assessment that is suitable for the Electrolyte environment of patients.

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Superatomic Anion Al<sub>6</sub>O<sup>2-</sup> and the Prospect for Cluster Assembled Crystals

Publication date: Available online 21 June 2019

Source: Chemical Physics

Author(s): Zhaoyan Zhang, Junmiao Zhao, Jianling Tang, Hongshan Chen

Abstract

The structures of Al6OK2 and Al7N/CK are determined using unbiased genetic algorithm combined with ab initio methods. It was experimentally confirmed that Al7C- possesses exceptional stability. This study presets the interpretation for the hetero magic clusters. The delocalized Jellium orbitals of the metal moieties and the atomic orbitals of the nonmetal atom interact strongly and form bonding and antibonding orbitals. The orbital interactions lead to closed s2p6 shells of the nonmetal atom and the 18-electron S2P6D10 shells of the metal moieties. The 26 valence electrons correspond to a strong magic number. Al6OK2 cluster is formed by ionically bonding two K+ cations to the Al6O2- anion. The electronic structures of Al6O2- core also accord with the Wade-Mingos rule. We build two typical ionic AB2 crystals. The interactions between the building units reach 1.48 eV, and the phonon dispersion curves and elastic constants confirm the assembled structures are dynamically stable.


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Laser cooling of the SiO<sup>+</sup> molecular ion: A theoretical contribution

Publication date: Available online 21 June 2019

Source: Chemical Physics

Author(s): Rui Li, Xiang Yuan, Guiying Liang, Yong Wu, Jianguo Wang, BingYan

Abstract

The feasibility of laser-cooling SiO+ molecular ion is studied by using ab initio methods. The electronic structures of 14 Λ-S states and 30 Ω states of SiO+ are computed by means of high-level configuration interaction method (including Davidson correction) with scalar relativistic correction. The calculated spectroscopic constants of bound states of SiO+ are in excellent agreement with available experimental results. The perturbation on vibrational levels of B2Σ+ is studied with the help of a spin-orbit coupling matrix elements which includes B2Σ+-14Σ-, B2Σ+-14Π, and B2Σ+-12Σ- interacting states pairs. The calculated Franck-Condon factors and branching ratio of the B2Σ+1/2-X2Σ+1/2 transition are highly diagonal. The radiative lifetime of B2Σ+1/2 state is evaluated to be 68.0 ns, which is sufficiently short for laser cooling. On the basis of the B2Σ+1/2-X2Σ+1/2 transition, we propose a possible laser cooling scheme by using two lasers with wavelengths around 400 nm.

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Suggested laser cooling scheme for SiO+ molecule utilizing the B2Σ+→X2Σ+ transition. Dashed arrows display the decay channel from B2Σ+(ν′=0), and solid arrows present the laser-driven transitions with certain wavelength λν′ν″.

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Mechanisms of Sequential Ion-molecule Reactions in Protonated Methanol Using Mass Spectrometry, <em>Ab Initio</em> Methods, and Statistical Modeling

Publication date: Available online 21 June 2019

Source: Chemical Physics

Author(s): Melanie C. White, Rachel E. Mizrahi, Jennifer E. Ruliffson, Matthew Khoury, Joshua J. Melko

Abstract

We present mass spectrometry results for reactions of protonated methanol clusters, (CH3OH)nH+. Mass spectra indicate a preference for association over condensation at our experimental conditions and are used in conjunction with computational methods to probe the reaction mechanisms involved. We find that the reaction for the protonated monomer with neutral methanol consists of two entrance complexes that are in equilibrium due to a very small barrier between them. Statistical modeling indicates that competition between proton transfer, condensation, and association are dictated by the depth of the proton-bound complex and the height of the SN2 transition state. For the reaction of the protonated dimer we determine condensation is not energetically favorable at thermal energies as a solvation effect raises the SN2 barrier. Geometries for protonated methanol clusters (CH3OH)nH+ up to n = 6 are also provided, which allow us to examine the role of entropy and hydrogen bonding in these structures.


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Titanium Dioxide-Molybdenum Disulfide for Photocatalytic Degradation of Methylene Blue

Publication date: Available online 21 June 2019

Source: Chemical Physics

Author(s): Olaniyan Ibukun, Prescott E. Evans, Peter A. Dowben, Hae Kyung Jeong

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Structural, optical and photocatalytic studies of Zn doped MoO<sub>3</sub> nanobelts

Publication date: Available online 21 June 2019

Source: Chemical Physics

Author(s): Amal L. Al-Otaibi, Taher Ghrib, ModyAlqahtani, Mody A. Alharbi, Ridha Hamdi, Imen Massoudi

Abstract

In this study, we report a synthesis of nanobelts-form zinc (Zn) doped molybdenum oxide (MoO3) with different weight percentages (2%, 3.3%, 4%, and 5%). The synthesized nanobelts grain size is of 45 nm. The preparation process and characterization techniques are presented in detail. Structural properties are studied by using the X-ray diffraction technique, scanning electron microscopy and transmission electron microscopy. The optical properties are investigated by using the Fourier transform infrared spectroscopy, UV–Vis reflectance spectra analysis, Raman spectroscopy, and fluorescence techniques. It was founded that Zn doping concentration highly influences the crystallographic structure where it passes from the insertion to the substitution alloys. The band gap decreases from 2.96 eV to 2.83 eV. The good structural and optical properties were obtained for the 5%Zn. The photocatalytic effect of the materials was studied for the pure and 5%Zn doped MoO3and it was denoted that Zn doping influences it highly.


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Phase equilibria in a microheterogeneous liquid–gas system: Gibbs capillary model

Publication date: Available online 21 June 2019

Source: Chemical Physics

Author(s): V.G. Baidakov

Abstract

A study has been made of the conditions of equilibrium and stability of microheterogeneous system of “a vapor bubble in liquid” and “a liquid droplet in vapor” type forming in the process of isothermal decay of a metastable or a labile state of a Lennard-Jones fluid located in a small-volume spherical cell with ‘tracking’ boundary conditions. Homogeneous phases are described by the equation of state of a Lennard-Jones fluid [V.G. Baidakov, J. Chem. Phys. 2016. 144. 074502]. It is shown that four types of equilibrium configurations of different stability may form at fixed values of the temperature, initial density and cell volume. Thus, as a result of the decay of a superheated liquid, in a small-volume cell there form configurations of “a vapor bubble in liquid” type and an “inverted” configuration of “a liquid droplet in vapor” type. Each of these configurations may be in a state of stable and unstable equilibrium. The dependence of thermodynamic parameters of a microheterogeneous system on the temperature, initial density and cell volume has been investigated. All calculations have been made in the approximation of independence of the surface tension of a disperse phase on its size.

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Spectroscopy of CdKr van der Waals complex using OODR process: New determination of the <math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si113.svg" class="math"><mrow><msup><mrow><mi>E</mi></mrow><mrow><mn>3</mn></mrow></msup><msubsup><mrow><mi mathvariant="normal">Σ</mi></mrow><mrow><mn>1</mn></mrow><mrow><mo>+</mo></mrow></msubsup><mo stretchy="false">(</mo><mn>5</mn><mi>s</mi><mn>6</mn><mi>s</mi><mspace width="0.12em"></mspace><msup><mrow></mrow><mrow><mn>3</mn></mrow></msup><msub><mrow><mi>S</mi></mrow><mrow><mn>1</mn></mrow></msub><mo stretchy="false">)</mo></mrow></math> Rydberg state potential

Publication date: Available online 19 June 2019

Source: Chemical Physics

Author(s): T. Urbańczyk, J. Koperski

Abstract

Comprehensive spectroscopic study of CdKr van der Waals complex in its Rydberg electronic energy state E3Σ1+(5s6s3S1), using OODR process from the ground X1Σ0+(5s21S0) state via the intermediate A30+(5s5p3P1) or B31(5s5p3P1) states, is presented. Detection of the E3Σ1+,υA30+,υ and E3Σ1+,υB31,υ transition frequencies with higher accuracy and spectrally narrower laser extends previous analyses and simulations of laser induced fluorescence (LIF) excitation spectra. Potential energy curve of the E3Σ1+state exhibits double-well structure with inner (deeper) E3Σ1in+ and outer (shallower) E3Σ1out+ wells. More reliable characterization of both wells using inversed perturbation approach (IPA) methodology is achieved.

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Application of decay- and evolution-associated spectra for molecular systems with spectral shifts or inherent inhomogeneities

Publication date: Available online 8 June 2019

Source: Chemical Physics

Author(s): Yakov Braver, Andrius Gelzinis, Jevgenij Chmeliov, Leonas Valkunas

Abstract

Decay- and evolution-associated spectra (DAS and EAS) are among the most popular methods for global analysis of time-resolved spectroscopy data. To interpret the obtained results in terms of a physical model, the system under consideration must satisfy several assumptions—spectral and temporal independence and lack of intrinsic disorder. In this work we study possible applicability of the DAS/EAS analysis for the time-resolved fluorescence spectra of several model systems, which fail to satisfy the required assumptions. We show that time-dependent spectral shifts can be distinguished by systematic comparison of DAS/EAS with different number of compartments. Somewhat unexpectedly, we demonstrate that DAS/EAS are rather robust for small systems even when they possess inherent disorder of excitation energy transfer or relaxation rates. In the case of larger molecular aggregates, the interpretation of DAS/EAS becomes much more ambiguous as the obtained results cannot be easily related to a physical kinetic and/or structural model.

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The effects of TMDD-PA concentration on roughness of Si &#60;110> and etching rate ratio of Si &#60;110>/&#60;111> in alkaline KOH solution

Publication date: Available online 5 June 2019

Source: Chemical Physics

Author(s): Chunlin Zhu, Qingbin Jiao, Xin Tan, Hao Hu, Bayanheshig

Abstract

High aspect ratio gratings (HARG) can be obtained by anisotropic etching of Si <110>/<111>. Usually isopropyl alcohol (IPA) is added to the solution in order to smooth Si <110> surface. However, the addition of IPA can reduce the etching rate ratio of Si <110>/<111>, which leads to a reduction of grating’s aspect ratio. The effects of another additive TMDD-PA (TMDD: IPA = 1: 1 in wt%) were discussed. The experimental data indicates that TMDD-PA behaves better than IPA when smoothing Si <110> surface, and etching rate ratio of Si <110>/<111> increases with the increasing concentration of TMDD-PA. Mechanism of IPA and TMDD-PA in etching were analyzed. Molecules of IPA and TMDD behave differently on Si surfaces, and they have different impacts on H2O molecules.

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Category: Current Chemistry Research

Last update: 28.03.2018.






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