Hasil untuk "Physical and theoretical chemistry"

R. T. Tung

D. Tasis, N. Tagmatarchis, A. Bianco et al.

U. Wille

F. Herrera, J. Owrutsky

This is a tutorial-style introduction to the field of molecular polaritons. We describe the basic physical principles and consequences of strong light-matter coupling common to molecular ensembles embedded in UV-visible or infrared cavities. Using a microscopic quantum electrodynamics formulation, we discuss the competition between the collective cooperative dipolar response of a molecular ensemble and local dynamical processes that molecules typically undergo, including chemical reactions. We highlight some of the observable consequences of this competition between local and collective effects in linear transmission spectroscopy, including the formal equivalence between quantum mechanical theory and the classical transfer matrix method, under specific conditions of molecular density and indistinguishability. We also overview recent experimental and theoretical developments on strong and ultrastrong coupling with electronic and vibrational transitions, with a special focus on cavity-modified chemistry and infrared spectroscopy under vibrational strong coupling. We finally suggest several opportunities for further studies that may lead to novel applications in chemical and electromagnetic sensing, energy conversion, optoelectronics, quantum control, and quantum technology.

Ling Zhang, Ke Jiang, Lifeng Yang et al.

Separation of acetylene from carbon dioxide remains a daunting challenge because of their very similar molecular sizes and physical properties. We herein report the first example of using copper(I)-alkynyl chemistry within an ultramicroporous MOF (CuI@UiO-66-(COOH)2) to achieve ultrahigh C2H2/CO2 separation selectivity. The anchored Cu(I) ions on the pore surfaces can specifically and strongly interact with C2H2 molecule through copper(I)-alkynyl π-complexation and thus rapidly adsorb large amount of C2H2 at low-pressure region, while effectively reduce CO2 uptake due to the small pore sizes. This material thus exhibits the record high C2H2/CO2 selectivity of 185 at ambient conditions, significantly higher than the previous benchmark ZJU-74a (36.5) and ATC-Cu (53.6). Theoretical calculations reveal that the unique π-complexation between Cu(I) and C2H2 mainly contributes to the ultrastrong C2H2 binding affinity and record selectivity. The exceptional separation performance was evidenced by breakthrough experiments for C2H2/CO2 gas mixtures. This work suggests a new perspective to functionalizing MOFs with copper(I)-alkynyl chemistry for highly selective separation of C2H2 over CO2.

Rahman Matee Ur, Abbas Ghazanfar, Hussain Syed Baqar et al.

Conventional solid oxide fuel cells (SOFCs) work at high operating temperatures (800–1,000°C). Lowering the operating temperature of SOFCs reduces the open-circuit voltage (OCV) and performance. Herein, a scheme was established to boost the voltage of the developed SOFC using a DC-DC voltage booster. The LTspice technique was used to develop a DC-DC booster, and the code was generated with a minimum of 0.7 V. For experimental evidence, BixAg1.00Fe1−x Zn2O7+δ (BAFZ oxide) materials were synthesized to investigate anodic properties. UV-vis and Fourier transform infrared spectroscopy techniques were used to determine the band gaps and functional groups. The vibrational modes of composite materials were studied via Raman spectroscopy. A slight peak shift toward a higher wavenumber was noted in the BAFZ oxide sample attributed to the addition of bismuth trioxide (Bi2O3). The conductivity was measured and found to be 1.2 S/cm at 600°C in a H2 atmosphere. Fuel cell performance was also measured in the temperature range of 400–620°C, and a maximum OCV of 1.1 V was achieved at 620°C. Finally, the boosted voltage was recorded at 2.2 V under the same circumstances using a DC-DC booster.

Shinya Kosaki, Naohiko Nakamura, Yoshiki Nakajima et al.

E. Cortes, Roland Grzeschik, S. A. Maier et al.

Masaya SUGIZAKI, Hisayoshi MATSUSHIMA, Mikito UEDA et al.

This study investigated the electrodeposition behavior of Al–Au alloys in AlCl3–NaCl–KCl molten salt containing AuCl at 443 K, and porous gold was formed by potential pulse electrolysis in the molten salt. The deposition/dissolution potential of Au in the molten salt was approximately 2.0 V vs. Al/Al(III). For the Al–Au alloy electrodeposits obtained by constant potential electrolysis, the Au concentration was less than 1 at% at potentials lower than 0.0 V. Then the Au concentration increased sharply to 84 at% at 0.0 V and increased gradually to 92 at% at 0.3 V and 98 at% at 0.9 V. Porous gold was formed by potential pulse electrolysis with repeated Al–Au alloys electrodeposition and Al dissolution. The specific surface area of the electrodeposits obtained by potential pulse electrolysis increased with decreasing frequency. The specific surface area of porous gold obtained in this experiment was up to 9.2 m2 g−1.

Antoine Marie, Abdallah Ammar, Pierre-Franccois Loos

We provide an in-depth examination of the $GW$ approximation of Green's function many-body perturbation theory by detailing both its theoretical and practical aspects in the realm of quantum chemistry. First, the quasiparticle context is introduced before delving into the derivation of Hedin's equations. From these, we explain how to derive the well-known $GW$ approximation of the self-energy. In a second time, we meticulously explain each step involved in a $GW$ calculation and what type of physical quantities can be computed. To illustrate its versatility, we consider two contrasting systems: the water molecule, a weakly correlated system, and the carbon dimer, a strongly correlated system. Each stage of the process is thoroughly detailed and explained alongside numerical results and illustrative plots. We hope that the contribution will facilitate the dissemination and democratization of Green's function-based formalisms within the computational and theoretical quantum chemistry community.

N. Benedek, M. Hayward

We review the theoretical, computational, and synthetic literature on hybrid improper ferroelectricity in layered perovskite oxides. Different ferroelectric mechanisms are described and compared, and their elucidation using theory and first-principles calculations is discussed. We also highlight the connections between crystal chemistry and the physical mechanisms of ferroelectricity. The experimental literature on hybrid improper ferroelectrics is surveyed, with a particular emphasis on cation-ordered double perovskites, Ruddlesden–Popper and Dion–Jacobson phases. We discuss preparative routes for synthesizing hybrid improper ferroelectrics in all three families and the conditions under which different phases can be stabilized. Finally, we survey some synthetic opportunities for expanding the family of hybrid improper ferroelectrics.

Shiori Fujimori, Y. Mizuhata, N. Tokitoh

The aromaticity and synthetic application of “heavy benzenes”, i.e., benzenes containing a heavier Group 14 element (Si, Ge, Sn, and Pb) in place of skeletal carbon, have been the targets of many theoretical and synthetic studies. Although the introduction of a sterically demanding substituent enabled us to synthesize and isolate heavy aromatic species as a stable compound by suppressing their high reactivity and tendency to polymerize, the existence of a protection group is an obstruction to the development of functional materials based on heavy aromatics. This review will delineate the most recent topics in the chemistry of heavy aromatics, i.e., the chemistry of “metallabenzenyl anions”, which are the heavier Group 14 element analogs of phenyl anions stabilized by taking advantage of charge repulsion instead of steric protection.

Chen Ke, Yang Xudong, Hao Rui et al.

Activation of peroxymonosulfate (PMS) to degrade persistent organic contaminants has received increasing attention in wastewater purification. In this study, Cu2O catalysts with different exposed crystal facets were prepared, characterized, and evaluated for acetaminophen (ACE) degradation through PMS activation. The experimental results showed that cubic Cu2O with {100} facets exhibited remarkable activity on ACE removal by PMS activation in wide pH range of 3–11. DFT calculations indicated that Cu2O-{100} displayed higher electron transfer efficiency and PMS adsorption ability, further improving PMS activation. The radicals quenching experiments and electron paramagnetic resonance (EPR) results illustrated that singlet oxygen (1O2) was dominant reactive oxidative species (ROSs) during oxidation reactions and the relevant generation pathways were distinctly elucidated. Finally, the possible PMS activation mechanisms were discussed for ACE degradation in a wide pH range. This study will provide new insights to disclose PMS-based advanced oxidation processes (AOPs), and offer a new approach for wastewater purification by non-radical reactions.

Lidan Xiao, Bing Yan, Boris F. Minaev

Intensity of transitions from the <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msup><mi>b</mi><mn>1</mn></msup><msubsup><mrow><mstyle mathsize="70%" displaystyle="true"><mo>∑</mo></mstyle></mrow><mi mathvariant="normal">g</mi><mo>+</mo></msubsup><mo> </mo></mrow></semantics></math></inline-formula> and <i>a</i>¹Δ_g states to the ground state <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msup><mi mathvariant="normal">X</mi><mn>3</mn></msup><msubsup><mrow><mstyle mathsize="70%" displaystyle="true"><mo>∑</mo></mstyle></mrow><mi mathvariant="normal">g</mi><mo>−</mo></msubsup><mo> </mo></mrow></semantics></math></inline-formula> in the near IR emission spectrum of the S₂ molecule has been calculated by the multireference configuration interaction method taking into account spin-orbit coupling (SOC). The intensity of the<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mo> </mo><msup><mi>b</mi><mn>1</mn></msup><msubsup><mrow><mstyle mathsize="70%" displaystyle="true"><mo>∑</mo></mstyle></mrow><mi mathvariant="normal">g</mi><mo>+</mo></msubsup></mrow></semantics></math></inline-formula> − <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msup><mrow><mrow><mo> </mo><mi mathvariant="normal">X</mi></mrow></mrow><mn>3</mn></msup><msubsup><mrow><mstyle mathsize="70%" displaystyle="true"><mo>∑</mo></mstyle></mrow><mrow><mi mathvariant="normal">g</mi><mo>,</mo><mi>M</mi><mi>s</mi><mo>=</mo><mo>±</mo><mn>1</mn></mrow><mo>−</mo></msubsup></mrow></semantics></math></inline-formula> transition is largely determined by the spin interaction with the electromagnetic wave, which comes from the zero-field splitting of the ground X multiplet and the SOC-induced mixing between <i>b</i> and <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msup><mi mathvariant="normal">X</mi><mn>3</mn></msup><msubsup><mrow><mstyle mathsize="70%" displaystyle="true"><mo>∑</mo></mstyle></mrow><mrow><mi mathvariant="normal">g</mi><mo>,</mo><mn>0</mn></mrow><mo>−</mo></msubsup></mrow></semantics></math></inline-formula> states. The Einstein coefficients for the experimentally detected 0−0, 0−1, 1−1 bands of the <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msup><mi>b</mi><mn>1</mn></msup><msubsup><mrow><mstyle mathsize="70%" displaystyle="true"><mo>∑</mo></mstyle></mrow><mi mathvariant="normal">g</mi><mo>+</mo></msubsup><mo>−</mo><msup><mi mathvariant="normal">X</mi><mn>3</mn></msup><msubsup><mrow><mstyle mathsize="70%" displaystyle="true"><mo>∑</mo></mstyle></mrow><mrow><mi mathvariant="normal">g</mi><mo>,</mo><mi>M</mi><mi>s</mi><mo>=</mo><mo>±</mo><mn>1</mn></mrow><mo>−</mo></msubsup></mrow></semantics></math></inline-formula> emission system are calculated in good agreement with observations. The Einstein coefficient of the <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msup><mi>a</mi><mn>1</mn></msup><msub><mo>∆</mo><mi mathvariant="normal">g</mi></msub><mo>−</mo><msup><mi mathvariant="normal">X</mi><mn>3</mn></msup><msubsup><mrow><mstyle mathsize="70%" displaystyle="true"><mo>∑</mo></mstyle></mrow><mrow><mi mathvariant="normal">g</mi><mo>,</mo><mi>M</mi><mi>s</mi><mo>=</mo><mo>±</mo><mn>1</mn></mrow><mo>−</mo></msubsup></mrow></semantics></math></inline-formula> magnetic dipole transition is very low, being equal to 0.0014 s⁻¹. Nonetheless, the weakest of all experimentally observed bands (the 0−0 band of the <i>a-X_Ms=</i>_±1 transition) qualitatively corresponds to this calculation. Most importantly, we provide many other IR bands for magnetic dipole <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msup><mi>b</mi><mn>1</mn></msup><msubsup><mrow><mstyle mathsize="70%" displaystyle="true"><mo>∑</mo></mstyle></mrow><mi mathvariant="normal">g</mi><mo>+</mo></msubsup></mrow></semantics></math></inline-formula> − <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msup><mrow><mrow><mo> </mo><mi mathvariant="normal">X</mi></mrow></mrow><mn>3</mn></msup><msubsup><mrow><mstyle mathsize="70%" displaystyle="true"><mo>∑</mo></mstyle></mrow><mrow><mi mathvariant="normal">g</mi><mo>,</mo><mi>M</mi><mi>s</mi><mo>=</mo><mo>±</mo><mn>1</mn></mrow><mo>−</mo></msubsup></mrow></semantics></math></inline-formula> and <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msup><mi>a</mi><mn>1</mn></msup><msub><mo>∆</mo><mi mathvariant="normal">g</mi></msub><mo>−</mo><msup><mi mathvariant="normal">X</mi><mn>3</mn></msup><msubsup><mrow><mstyle mathsize="70%" displaystyle="true"><mo>∑</mo></mstyle></mrow><mrow><mi mathvariant="normal">g</mi><mo>,</mo><mi>M</mi><mi>s</mi><mo>=</mo><mo>±</mo><mn>1</mn></mrow><mo>−</mo></msubsup></mrow></semantics></math></inline-formula> transitions, which could be experimentally observable in the S₂ transparency windows from a theoretical point of view. We hope that these results will contribute to the further experimental exploration of the magnetic infrared bands in the S₂ dimer.

Zhangrong Lou, P. Zhou

Abstract In this work, we explore the substituent effect, which is a tunable parameter for the excited-state intra-molecular proton transfer (ESIPT) process, on the photo-physical properties and ESIPT process of benzo[a]imidazo[5,1,2-cd]indolizines via theoretical methods. The calculations in geometric parameters, O–H stretching vibration frequencies, hydrogen bonding energies and energy curves along with the proton transfer path demonstrate the substitution exhibits different effects on the hydrogen bonding behaviors in the ground and excited state, thereby on the ESIPT process. In addition, the simulated absorption and emission spectra are in agreement well with the experimental results. Compared to those for the analogs bearing fluorine and methyl substitutions, the relatively higher quantum yield and the blue-shift emission wavelength of methoxy group substituted compound have been attributed to the less extent of charge transfer in the excited state.

Xuan Ma, Hui Chen, Lixing Cao et al.

Physical fatigue during exercise can be defined as an impairment of physical performance. Multiple factors have been found contributing to physical fatigue, including neurotransmitter-mediated defense action, insufficient energy supply, and induction of oxidative stress. These mechanistic findings provide a sound theoretical rationale for nutritional intervention since most of these factors can be modulated by nutrient supplementation. In this review, we summarize the current evidence regarding the functional role of nutrients supplementation in managing physical performance and propose the issues that need to be addressed for better utilization of nutritional supplementation approach to improve physical performance.

O.S. Guseva, O.V. Malyshkina, A.I. Ivanova et al.

We obtained and studied the samples of ceramics based on barium niobate and calcium niobate CaxBa1-xNb2O6 with different percentages of barium and calcium (x=1; 0,9; 0,8; 0,7; 0,6; 0,5; 0,4; 0,3; 0,2; 0,1 and 0). The effect of the sintering temperature on the structure and dielectric properties of ceramics has been investigated. One batch of the samples was sintered at a temperature of 1100°C, the second at 1250°C. We have shown that the sintering temperature of 1100°C is not enough to obtain good ferroelectric properties, and the process of grain recrystallization is not completed. According to studies of the elemental composition, in samples sintered at a temperature of 1250°C with the Ca content greater than 0,5, Ba atoms are not present in all grains, which also affects the course of the temperature dependences of the dielectric constant A sample with x=0,3 is distinguished by its dielectric properties.

Barberis, Elettra, Manfredi, Marcello, Marengo, Emilio et al.

The ink used by Volta in his scripts appears to be a very complex mixture. Our analysis of the eluates from the EVA diskettes (via GCXGC/TOFMS) has revealed the presence of more than 1800 unique metabolites. The ink thus appears to be a very complex combination of different ingredients, mainly consisting of tannins, vegetable oils and resins together with root and wood dyes. In particular, the presence of hydroxy and dihydroxyanthraquinones, as well as natural quinoids, evidenced the use of madder dyes from Rubiaceae as an important component of this ink. Natural quinoids, based on a 9, 10-anthraquinone skeleton, hydroquinone and anthrone derivatives, and even the specific marker of alizarin, indicate the use of the Rubia tinctorum. Additionally, the presence of several signals of fatty acids, saturated and unsaturated mono and dicarboxylic acids, as well as of the typical signals of Pinaceae resins substantiated the use of a vegetable oil and colophony. Several signals of cyclic monosaccharides suggested also the use of natural gum (Acacia Senegal also known as Arabic gum). It is known that Arabic gum, as well as linseed oil, were often employed as thickeners to increase the viscosity of the ink and to protect it from excess absorption of atmospheric oxygen. Curiously, we also found characteristic signals from alkaloids such as Dioncophyllin A and B, typical metabolites from tropical/exotic plants such as Triphyophyllum, Habropeltatum and Dioncophyllum. To our reckoning such an extensive array of ingredients in inks adopted over millennia has never been reported.

Roohangiz Morshedi, Mehdi Shahidi-Zandi, Maryam Kazemipour

Inhibition effects of pantoprazole drug on the under-deposit corrosion of carbon steel in 3.5% NaCl solution saturated with CO2 have been investigated by the techniques of potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The carbon steel electrode was covered with a layer of the silica sand to prepare the sand-covered electrode. The increase of the drug concentration led to an increase in the inhibition efficiency (IE) of carbon steel against under-deposit corrosion in the brine solution. The Langmuir isotherm can describe the adsorption behavior of pantoprazole on the surface of carbon steel. Measurements of potentiodynamic polarization indicated that pantoprazole is an anodic inhibitor. The effects of temperature on the under-deposit corrosion behavior of carbon steel were studied both in the absence and presence of pantoprazole drug. The enthalpy of the drug adsorption was obtained from the temperature dependence of the corrosion inhibition process. A reasonable agreement was observed between the IE values resulted from the potentiodynamic polarization and the EIS techniques.

Huancong Shi, Qiming Wu, linhua Jiang et al.

Antibiotic residues lead to serious environment pollution and provoke many health problems. Among all the antibiotics, Tetracycline hydrochloride (TC-HCl) in surface and drinking waters around the world has attracted widespread attention. Large-scale SnO2 with hollow microspheres were synthesized via one-step hydrothermal approach as a high-efficiency photocatalyst to degrade TC-HCl. These synthesized series of SnO2 materials with various molar ratios were characterized by XRD, SEM and EIS in terms of crystal structure, morphology, and electronic resistance. SnO2 hollow microspheres synthesized with SnCl2·2H2O to Na3C6H5O7·2H2O at the molar ratio of 1:4 showed the best photocatalytic degradation activity of TC-HCl under UV light illumination. The high photocatalytic property was considered to be benefit from the unique hollow microstructure, and the updated SnO2 hollow microspheres were good candidates for synthesis of composite photocatalysts in area of photo degradation, such as C3N4-SnO2, etc.