Journal Description
Physchem
Physchem
is an international, peer-reviewed, open access journal on science and technology in physical chemistry published quarterly online by MDPI.
- Open Access— free for readers, with article processing charges (APC) paid by authors or their institutions.
- High Visibility: indexed within Scopus and other databases.
- Rapid Publication: manuscripts are peer-reviewed and a first decision is provided to authors approximately 22.8 days after submission; acceptance to publication is undertaken in 6.5 days (median values for papers published in this journal in the second half of 2023).
- Recognition of Reviewers: APC discount vouchers, optional signed peer review, and reviewer names published annually in the journal.
Latest Articles
Role of N1-Domain, Linker, N2-Domain, and Latch in the Binding Activity and Stability of the Collagen-Binding Domain for the Collagen-Binding Protein Cbm from Streptococcus mutans
Physchem 2024, 4(2), 120-130; https://0-doi-org.brum.beds.ac.uk/10.3390/physchem4020009 - 12 Apr 2024
Abstract
A special type of Streptococcus mutans expressing collagen-binding proteins (CBPs), Cnm, and Cbm, on the cell surface has been shown to be highly pathogenic. It is believed that S. mutans with CBPs that has entered the blood vessel attaches to collagen molecules exposed
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A special type of Streptococcus mutans expressing collagen-binding proteins (CBPs), Cnm, and Cbm, on the cell surface has been shown to be highly pathogenic. It is believed that S. mutans with CBPs that has entered the blood vessel attaches to collagen molecules exposed from the damaged blood vessel, inhibiting aggregation by platelets and increasing bleeding. Therefore, it is crucial to understand the molecular characteristic features of CBPs to protect against and cure S. mutans-related diseases. In this work, we highlighted the Cbm/collagen-binding domain (CBD) and examined its binding ability and thermal stability using its domain/region exchange variants in more detail. The CBD comprises the N1-domain, a linker, N2-domain, and a latch (N1–N2~), where the latch interacts with the N1-domain to form a β-sheet. The collagen-binding activity of the Cbm/CBD domain/region exchange variants was investigated using ELISA. Binding assays demonstrated that the N-domain_linker_N-domain composition is necessary for collagen binding as previously reported, newly that the latch is involved in binding through the β-sheet with the N1-domain when the N1-domain is present at the N-terminal position, and that the N2-domain is particularly important for collagen binding at both the N- and C-terminal positions. Thermal denaturation experiments newly revealed that the linker and latch bound to the N-domain contribute to N-domain stabilization but have no effect on the N-domain_linker_N-domain molecule, which contains two N-domains. It has also been shown that the N-terminal N2-domain destabilizes the N-domain_linker_N-domain structure. The results of this study will contribute to the rapid detection of CBP, development of CBP-targeted therapies, and application of CBPs to protein engineering using their collagen-binding ability.
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(This article belongs to the Section Biophysical Chemistry)
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Phosphatidylinositol-4,5-biphosphate (PIP2)-Dependent Thermoring Basis for Cold-Sensing of the Transient Receptor Potential Melastatin-8 (TRPM8) Biothermometer
by
Guangyu Wang
Physchem 2024, 4(2), 106-119; https://0-doi-org.brum.beds.ac.uk/10.3390/physchem4020008 - 26 Mar 2024
Abstract
The menthol sensor transient receptor potential melastatin-8 (TRPM8) can be activated by cold and, thus, serves as a biothermometer in a primary afferent sensory neuron for innocuous-to-noxious cold detection. However, the precise structural origins of specific temperature thresholds and sensitivity have remained elusive.
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The menthol sensor transient receptor potential melastatin-8 (TRPM8) can be activated by cold and, thus, serves as a biothermometer in a primary afferent sensory neuron for innocuous-to-noxious cold detection. However, the precise structural origins of specific temperature thresholds and sensitivity have remained elusive. Here, a grid thermodynamic model was employed, to examine if the temperature-dependent noncovalent interactions found in the 3-dimensional (3D) structures of thermo-gated TRPM8 could assemble into a well-organized fluidic grid-like mesh network, featuring the constrained grids as the thermorings for cold-sensing in response to PIP2, Ca2+ and chemical agents. The results showed that the different interactions of TRPM8 with PIP2 during the thermal incubation induced the formation of the biggest grids with distinct melting temperature threshold ranges. Further, the overlapped threshold ranges between open and pre-open closed states were required for initial cold activation with the matched thermo-sensitivity and the decrease in the systematic thermal instability. Finally, the intact anchor grid near the lower gate was important for channel opening with the active selectivity filter. Thus, PIP2-dependent thermorings in TRPM8 may play a pivotal role in cold sensing.
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(This article belongs to the Section Theoretical and Computational Chemistry)
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Open AccessArticle
Ground-State Tautomerism and Excited-State Proton Transfer in 7-Hydroxy-4-methyl-8-((phenylimino)methyl)-2H-chromen-2-one as a Potential Proton Crane
by
Daniela Nedeltcheva-Antonova and Liudmil Antonov
Physchem 2024, 4(1), 91-105; https://doi.org/10.3390/physchem4010007 - 11 Mar 2024
Abstract
The tautomerism in the title compound as a potential long-range proton transfer (PT) switch has been studied by using the DFT and TD-DFT approaches. The data show that in aprotic solvents, the enol tautomer dominates, while the increase in the content of the
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The tautomerism in the title compound as a potential long-range proton transfer (PT) switch has been studied by using the DFT and TD-DFT approaches. The data show that in aprotic solvents, the enol tautomer dominates, while the increase in the content of the keto tautomer (short-range PT) rises as a function of polarity of the solvent. In ethanol, due to specific solute–solvent stabilization through intermolecular hydrogen bonding, a substantial amount of the keto forms exists in solution. The irradiation leads to two competitive processes in the excited state, namely ESIPT and trans/cis isomerization around the azomethine bond as in other structurally similar Schiff bases. The studied compound is not suitable for bistable tautomeric switching, where long-range PT occurs, due to the difficult enolization of the coumarin carbonyl group.
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(This article belongs to the Section Experimental and Computational Spectroscopy)
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Effect of Molecular Architecture of Surface-Active Organosilicon Macromers on Their Colloidal Properties in Relation to Heterophasic Radical Polymerization of Styrene and Methyl Methacrylate
by
Valeriy Borisovich Gostenin, Anton Mikhailovich Shulgin, Irina Sergeevna Shikhovtseva, Alexandra Alexandrovna Kalinina, Inessa Alexandrovna Gritskova and Vitaliy Pavlovich Zubov
Physchem 2024, 4(1), 78-90; https://0-doi-org.brum.beds.ac.uk/10.3390/physchem4010006 - 23 Feb 2024
Abstract
The effects of the molecular architecture of water-insoluble organosilicon polymerizable surfactant macromers (SAMs) on their colloidal-chemical characteristics and on their efficiency in heterophase radical polymerization of styrene and methyl methacrylate were studied. It was shown that despite considerable differences in the structure of
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The effects of the molecular architecture of water-insoluble organosilicon polymerizable surfactant macromers (SAMs) on their colloidal-chemical characteristics and on their efficiency in heterophase radical polymerization of styrene and methyl methacrylate were studied. It was shown that despite considerable differences in the structure of three synthesized oligomers (linear α,ω-dipropylmethacrylatepolydimethylsiloxane with a number of repeated siloxane units n = 20—l-SAM; branched γ-methacryloxypropyl containing dimethylsiloxane oligomer—b-SAM; and “spherical” oligo-(γ-methacryloxypropyl)silsesquioxane—s-SAM), the colloidal-chemical characteristics (interfacial tension, layer thickness, adsorption, etc.) were rather similar. In particular, they all form “thick” multimolecular adsorption layers on the toluene–water interphase. All three SAMs were shown to act as effective colloidal stabilizers in heterophase radical polymerization of styrene and methyl methacrylate, which resulted in one-step preparation of large (0.5–1.5 µm) polymer particles with narrow particle size distribution. The obtained results are consistent with the published data on the use of water-insoluble polymerizable oligomers of various chemical structures on the heterophase radical polymerization. The use of these colloidal stabilizers may be considered as an effective way to obtain stable suspensions with large particles and narrow particle size distribution.
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(This article belongs to the Section Surface Science)
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Open AccessArticle
Synthesis of Periclase Phase (MgO) from Colloidal Cassava Starch Suspension, Dual Application: Cr(III) Removal and Pigment Reuse
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Nayara Balaba, Julia de O. Primo, Anne R. Sotiles, Silvia Jaerger, Dienifer F. L. Horsth, Carla Bittencourt and Fauze J. Anaissi
Physchem 2024, 4(1), 61-77; https://0-doi-org.brum.beds.ac.uk/10.3390/physchem4010005 - 04 Feb 2024
Abstract
This study aimed to synthesize magnesium oxide (MgO) using a colloidal starch method for two primary purposes: the removal of chromium (III) ions from synthetic wastewater and the subsequent use of the chromium-containing material as synthetic inorganic pigments (SIPs) in commercial paints. The
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This study aimed to synthesize magnesium oxide (MgO) using a colloidal starch method for two primary purposes: the removal of chromium (III) ions from synthetic wastewater and the subsequent use of the chromium-containing material as synthetic inorganic pigments (SIPs) in commercial paints. The synthesis used to obtain the oxide (St-MgO) is a promising method for using plants, such as cassava, as green fuels due to their abundance, low cost, and non-toxicity. With this, the oxide showed greater porosity and alkalinity, compared to commercial magnesium oxide (Cm-MgO). The MgO samples were subjected to structural characterization using XRD and FTIR, surface area and pore volume study by B.E.T. and SEM, and chemical composition by ICP-OES and thermogravimetric analysis (TGA). The crystalline periclase phase was identified for both samples, but the brucite phase was shown to be a secondary phase for the commercial sample. After the removal of chromium ions, the brucite crystalline phase became the majority phase for the samples, regardless of the concentration of ions removed. The pigments were characterized by color measurements and discussed in terms of colorimetric parameters using the CIELab method and electron spectroscopy (VIS-NIR). This study also evaluated the colorimetric stability of green pigments in aggressive environments (acidic and alkaline) over a 240 h exposure period, demonstrating minimal color difference. This study aims to develop materials for the decontamination of wastewater containing chromium and its reuse as a synthetic inorganic pigment, using an innovative and sustainable synthesis method.
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(This article belongs to the Section Solid-State Chemistry and Physics)
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Open AccessArticle
Atomistic Modeling of Spinel Oxide Particle Shapes and Reshaping under OER Conditions
by
Öyküm N. Avcı, Luca Sementa and Alessandro Fortunelli
Physchem 2024, 4(1), 43-60; https://0-doi-org.brum.beds.ac.uk/10.3390/physchem4010004 - 10 Jan 2024
Abstract
The surface configurations of the low-index facets of a set of spinel oxides are investigated using DFT+U calculations to derive surface energies and predict equilibrium nanoparticle shapes via the Wulff construction. Two very different conditions are investigated, corresponding to application either in heterogeneous
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The surface configurations of the low-index facets of a set of spinel oxides are investigated using DFT+U calculations to derive surface energies and predict equilibrium nanoparticle shapes via the Wulff construction. Two very different conditions are investigated, corresponding to application either in heterogeneous catalysis or in electrocatalysis. First, the bare stoichiometric surfaces of NiFe2O4, CoFe2O4, NiCo2O4, and ZnCo2O4 spinels are studied to model their use as high-temperature oxidation catalysts. Second, focusing attention on the electrochemical oxygen evolution reaction (OER) and on the CoFe2O4 inverse spinel as the most promising OER catalyst, we generate surface configurations by adsorbing OER intermediates and, in an innovative study, we recalculate surface energies taking into account adsorption and environmental conditions, i.e., applied electrode potential and O2 pressure. We predict that under OER operating conditions, (111) facets are dominant in CoFe2O4 nanoparticle shapes, in fair agreement with microscopy measurements. Importantly, in the OER case, we predict a strong dependence of nanoparticle shape upon O2 pressure. Increasing O2 pressure increases the size of the higher-index (111) and (110) facets at the expense of the (001) more catalytically active facet, whereas the opposite occurs at low O2 pressure. These predictions should be experimentally verifiable and help define the optimal OER operative conditions.
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(This article belongs to the Section Theoretical and Computational Chemistry)
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X-ray and Nuclear Spectroscopies to Reveal the Element-Specific Oxidation States and Electronic Spin States for Nanoparticulated Manganese Cyanidoferrates and Analogs
by
Hongxin Wang, Songping D. Huang, Anthony T. Young, Stephen P. Cramer, Yoshitaka Yoda and Lei Li
Physchem 2024, 4(1), 25-42; https://0-doi-org.brum.beds.ac.uk/10.3390/physchem4010003 - 25 Dec 2023
Abstract
In this publication, the potential non-gadolinium magnetic resonant imaging agent—nanoparticulate K2Mn[Fe(CN)6]—its comparison sample KFe[Co(CN)6], as well as their reference samples were measured and analyzed using Mn, Co and Fe L-edge X-ray absorption spectroscopy (L XAS). From the
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In this publication, the potential non-gadolinium magnetic resonant imaging agent—nanoparticulate K2Mn[Fe(CN)6]—its comparison sample KFe[Co(CN)6], as well as their reference samples were measured and analyzed using Mn, Co and Fe L-edge X-ray absorption spectroscopy (L XAS). From the information obtained, we conclude that K2Mn[Fe (CN)6] has a high spin (hs)-Mn(II) and a low spin (ls)-Fe(II), while KFe[Co(CN)6] has an hs-Fe(II) and an ls-Co(III). In these Prussian blue (PB) analog structures, the L XAS analysis also led to the conclusion that the hs-Mn(II) in K2Mn[Fe(CN)6] or the hs-Fe(II) in KFe[Co(CN)6] bonds to the N in the [M(CN)6]4−/3− ions (where M = Fe(II) or Co(III)), while the ls-Fe(II) in K2Mn[Fe(CN)6] or the ls-Co(III) in KFe[Co(CN)6] bonds to the C in the [M(CN)6]4−/3− ion, suggesting the complexed metalloligand [Mn(II) or Fe(II)] occupies the N-bound site in PB. Then, nuclear resonant vibrational spectroscopy (NRVS) was used to confirm the results from the L XAS measurements: the Mn(II), Eu(III), Gd(III), Fe(II) cations complexed by [M(CN)6]n−-metalloligand all take the N-bound site in PB-like structures. Our NRVS studies also prove that iron in the K2Mn[Fe(CN)6] compound has a 2+ oxidation state and is surrounded by the C donor atoms in the [M(CN)6]n− ions.
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(This article belongs to the Section Nanoscience)
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Open AccessReview
Green Materials for Gel Formulation: Recent Advances, Main Features and Applications
by
Maria Eduarda B. C. Souza and Camila G. Pereira
Physchem 2024, 4(1), 3-24; https://0-doi-org.brum.beds.ac.uk/10.3390/physchem4010002 - 23 Dec 2023
Abstract
Biogels (hydrogels, oleogels, and bigels) are structured systems used as delivery vehicles for bioactive substances. The objective of this study was to provide an updated view of green materials used as biogels, discussing the different aspects related to their formulation. An overview of
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Biogels (hydrogels, oleogels, and bigels) are structured systems used as delivery vehicles for bioactive substances. The objective of this study was to provide an updated view of green materials used as biogels, discussing the different aspects related to their formulation. An overview of the application possibilities of these gels in different areas, such as food, cosmetics, pharmaceuticals, and medicine, is reported. Furthermore, an evaluation of the profile of studies using biogels was carried out in the last decades (1980–2023), showing the advances in knowledge about these materials in different application domains. Additionally, a consideration of future demands regarding studies involving biogels from a technological and process engineering point of view is highlighted.
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(This article belongs to the Section Biophysical Chemistry)
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Open AccessEditorial
Two Years of PhysChem: Current Status and Future Developments
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Sergei Manzhos, Jacinto Sa and Vincenzo Barone
Physchem 2024, 4(1), 1-2; https://0-doi-org.brum.beds.ac.uk/10.3390/physchem4010001 - 21 Dec 2023
Abstract
Two years ago, PhysChem was launched as a new physical chemistry journal publishing original research articles, reviews and perspectives, and communications focusing on physics-based description of chemical phenomena and their applications [...]
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Simulations of Lattice Vibrations in a One-Dimensional Triatomic Network
by
Romualdo Alejandro Ferreyra and Alfredo Juan
Physchem 2023, 3(4), 440-450; https://0-doi-org.brum.beds.ac.uk/10.3390/physchem3040028 - 05 Dec 2023
Abstract
Using equivalent electrical circuits (EEC) is not common practice in several areas of physical chemistry. The phonon concept is used in solid-state works but much less frequently in branches of chemistry. Lattice vibration phenomena present a high complexity when solving equations in real
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Using equivalent electrical circuits (EEC) is not common practice in several areas of physical chemistry. The phonon concept is used in solid-state works but much less frequently in branches of chemistry. Lattice vibration phenomena present a high complexity when solving equations in real systems. We present here a methodology that crosses disciplines and uses EEC that can be analyzed and solved using freely downloaded computer codes. To test our idea, we started with a one-dimensional lattice dynamics problem with two and three masses. The initial mechanical model is numerically solved, and then an equivalent circuit is solved in the framework of electrical network theory through the formalism of transfer function. Our lattice model is also solved using circuit analysis software. We found the dispersion relationship and the band gaps between acoustical and optical branches. The direct solution of a mechanical model gives the correct answers, however, the electrical analogue could give only a partial solution because the software was not designed to be converted into an analogue simulator. Due to the finite size of the circuit elements, the number of computed frequencies is less than those expected for two unit cells and right for eight. On the other hand, by using a huge number of electrical components, the network behaves like a low-pass filter, filtering higher frequencies.
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(This article belongs to the Section Solid-State Chemistry and Physics)
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Open AccessArticle
Irradiation of ZnPPIX Complexed with Bovine β-Lactoglobulin Causes Chemical Modifications and Conformational Changes of the Protein
by
Abdullah Albalawi, Omar Castillo, Michael L. Denton, John Michael Rickman, Gary D. Noojin and Lorenzo Brancaleon
Physchem 2023, 3(4), 411-439; https://0-doi-org.brum.beds.ac.uk/10.3390/physchem3040027 - 29 Nov 2023
Abstract
Photosensitization of proteins mediated by chromophores is a mechanism commonly employed by nature and mimicked in a broad array of laboratory research and applications. Nature has evolved specialized complexes of proteins and photosensitizers (PS) that assemble to form photoreceptor proteins (PRP). These are
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Photosensitization of proteins mediated by chromophores is a mechanism commonly employed by nature and mimicked in a broad array of laboratory research and applications. Nature has evolved specialized complexes of proteins and photosensitizers (PS) that assemble to form photoreceptor proteins (PRP). These are used by many organisms in diverse processes, such as energy conversion, protection against photodamage, etc. The same concept has been used in laboratory settings for many applications, such as the stimulation of neurons or the selective depletion of proteins in a signaling pathway. A key issue in laboratory settings has been the relationship between the photooxidation of proteins and conformational changes in host proteins. For several years, we have been interested in creating non-native PRP using porphyrin PS. In this study, we investigated the self-assembled complex between zinc protoporphyrin IX (ZnPPIX) and bovine β-lactoglobulin (BLG) as a model of non-native PRP. Since BLG undergoes a significant conformational transition near physiological pH, the study was carried out at acidic (pH 5) and alkaline (pH 9) conditions where the two conformations are respectively prevalent. We employed a series of steady-state and time-resolved optical spectroscopies as well as gel electrophoresis to experimentally characterize the photosensitization mechanisms and their effect on the host protein. Our results show that ZnPPIX prompts light-dependent modifications of BLG, which appear to be much more significant at alkaline pH. The modifications seem to be driven by photooxidation of amino acid residues that do not lead to the formation of cross-links or protein fragmentation.
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(This article belongs to the Section Photophysics, Photochemistry and Photobiology)
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Open AccessReview
Kinetics and Timescales in Bio–Nano Interactions
by
André F. Lima and Alioscka A. Sousa
Physchem 2023, 3(4), 385-410; https://0-doi-org.brum.beds.ac.uk/10.3390/physchem3040026 - 28 Oct 2023
Abstract
Engineered nanoparticles (NPs) have the potential to revolutionize disease diagnostics and treatment. However, NP interactions with proteins in biological fluids complicate their in vivo control. These interactions often lead to the formation of protein coronas around the NP surface, shaping NP fate and
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Engineered nanoparticles (NPs) have the potential to revolutionize disease diagnostics and treatment. However, NP interactions with proteins in biological fluids complicate their in vivo control. These interactions often lead to the formation of protein coronas around the NP surface, shaping NP fate and behavior within biological systems. To harness the full potential of NPs in biomedical applications, it is therefore essential to gain a comprehensive understanding of their interactions with proteins. Within this context, it must be recognized that traditional equilibrium-based descriptions of NP–protein interactions, which encompass parameters like equilibrium binding affinity and corona composition, do not provide sufficient detail to predict NP behavior in vivo. This limitation arises because the open in vivo system is a nonequilibrium state characterized by constantly changing concentrations and dynamic regulation of biological processes. In light of these considerations, this review explores the kinetics and timescales of NP–protein interactions, discussing their relevance, fundamental concepts, measurement techniques, typical ranges of association and dissociation rate constants, and dynamics of protein corona formation and dissociation. The review concludes by outlining potential areas for further research and development in this field.
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(This article belongs to the Section Biophysical Chemistry)
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Open AccessReview
Carbon-Based Materials for Energy Storage Devices: Types and Characterization Techniques
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Freddy Escobar-Teran, Hubert Perrot and Ozlem Sel
Physchem 2023, 3(3), 355-384; https://0-doi-org.brum.beds.ac.uk/10.3390/physchem3030025 - 13 Sep 2023
Abstract
The urgent need for efficient energy storage devices (supercapacitors and batteries) has attracted ample interest from scientists and researchers in developing materials with excellent electrochemical properties. Electrode material based on carbon, transition metal oxides, and conducting polymers (CPs) has been used. Among these
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The urgent need for efficient energy storage devices (supercapacitors and batteries) has attracted ample interest from scientists and researchers in developing materials with excellent electrochemical properties. Electrode material based on carbon, transition metal oxides, and conducting polymers (CPs) has been used. Among these materials, carbon has gained wide attention in Electrochemical double-layer capacitors (EDLC) due to its variable morphology of pores and structural properties as well as its remarkable electrical and mechanical properties. In this context, the present review article summarizes the history of supercapacitors and the basic function of these devices, the type of carbon electrode materials, and the different strategies to improve the performance of these devices. In addition, we present different approaches to studying the charging mechanism of these devices through different electrochemical techniques existing in the literature, since a deeper understanding of the interfacial charge storage mechanisms is also crucial in the elaboration and performance of the electrode material. We make a comparison of the different techniques and present their advantages and challenges. Taking these advances into account, we consider that the coupling between two methods/techniques provides a better understanding of the charge storage mechanisms in energy storage devices.
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(This article belongs to the Special Issue Advances in Carbon and Nanomaterials)
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Open AccessArticle
Capture and Reaction of CO2 and H2 Catalyzed by a Complex of Coronene: A Computational Study
by
Luis G. Guillén, Lioudmila Fomina and Roberto Salcedo
Physchem 2023, 3(3), 342-354; https://0-doi-org.brum.beds.ac.uk/10.3390/physchem3030024 - 22 Aug 2023
Abstract
An organometallic complex of coronene (Cor) and chromium (Cr) was designed and used as a catalyst in a simulated process in which a CO2 molecule is captured, activated, and then reacts with a hydrogen molecule (H2) to yield formic acid
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An organometallic complex of coronene (Cor) and chromium (Cr) was designed and used as a catalyst in a simulated process in which a CO2 molecule is captured, activated, and then reacts with a hydrogen molecule (H2) to yield formic acid (HCOOH). The structural characteristics and local aromaticity are due to the similarity in the binding scheme with the bis(benzene)chromium (Cr-Bz2). Such a molecular fragment, referred to here as a “Clar’s site”, involves a single chromium atom that binds to CO2 by transferring electron density through backdonation. Therefore, the capture of CO2 outside the Cr3-Cor2 complex allows for the carrying out of a hydrogenation process that involves the breaking of one of the C−O bonds, the double addition of hydrogen, the formation of HCOOH and its release, regenerating the structure of the Cr3-Cor2 complex. The thermodynamic and kinetic results of this reaction are analyzed, as well as the nature of the orbitals and the relevant interactions of this process. This work explores a new concept for the creation of single atom catalysts (SACs), taking advantage of the high electron density around the metallic center and the sandwich architecture, having shown that it can perform the catalytic reduction of CO2.
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(This article belongs to the Section Theoretical and Computational Chemistry)
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Open AccessFeature PaperReview
Electronically Excited States of Free Radicals
by
Igor V. Khudyakov
Physchem 2023, 3(3), 332-341; https://0-doi-org.brum.beds.ac.uk/10.3390/physchem3030023 - 07 Aug 2023
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Formation of the excited doublet (D) and quartet (Q) states of free radicals under their photoexcitation is discussed. The relative positions of the D and Q states are compared to the positions of the photoexcited states of organic molecules (Jablonsky diagram). A number
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Formation of the excited doublet (D) and quartet (Q) states of free radicals under their photoexcitation is discussed. The relative positions of the D and Q states are compared to the positions of the photoexcited states of organic molecules (Jablonsky diagram). A number of representative cases of the excited states of free radicals detected by their transient absorption or emission are presented. A special case of the population having the lowest Q state in some radicals is discussed. A spin–statistical factor in the reactions of Q and D is debated.
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Open AccessArticle
Examining the Hydration Behavior of Aqueous Calcium Chloride (CaCl2) Solution via Atomistic Simulations
by
Lida Yan and Ganesh Balasubramanian
Physchem 2023, 3(3), 319-331; https://0-doi-org.brum.beds.ac.uk/10.3390/physchem3030022 - 05 Aug 2023
Abstract
Equilibrium molecular dynamics simulations are performed to examine the hydration behavior of Ca2+ and Cl− across a wide range of salt concentrations (from 1 wt.% to 60 wt.% CaCl2) in an aqueous solution. The predicted radial distribution functions (RDFs)
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Equilibrium molecular dynamics simulations are performed to examine the hydration behavior of Ca2+ and Cl− across a wide range of salt concentrations (from 1 wt.% to 60 wt.% CaCl2) in an aqueous solution. The predicted radial distribution functions (RDFs) and coordination numbers (CNs) of Ca2+–water, Cl−–water, and Ca2+–Cl− agree with the previous studies conducted at concentrations below the solubility limit at room temperature. The hydration limit of aqueous calcium chloride solution is identified at 10 wt.% CaCl2 as the CNs remain constant below it. Beyond the bulk solubility limit ~44.7 wt.% CaCl2, a noticeable decrease in the CN of Cl− and water is recorded, implying the saturation of the solution. The solvating water molecules decrease with increasing salt concentration, which can be attributed to the growth in the number of ion pairs.
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(This article belongs to the Section Theoretical and Computational Chemistry)
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Open AccessArticle
Association, Conformational Rearrangements and the Reverse Process of Aggregates Dissociation during Apomyoglobin Amyloid Formation
by
Victor Marchenkov, Vitaly Balobanov, Mariya Majorina, Nelly Ilyina, Ivan Kashparov, Anatoly Glukhov, Natalya Ryabova and Natalya Katina
Physchem 2023, 3(3), 304-318; https://0-doi-org.brum.beds.ac.uk/10.3390/physchem3030021 - 24 Jul 2023
Abstract
Amyloid formation is linked with serious human diseases that are currently incurable. Usually, in the study of amyloid aggregation, the description of the protein’s association is in focus. Whereas the mechanism of the cross-β-structure formation, and the presence of aggregation reversibility, remain insufficiently
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Amyloid formation is linked with serious human diseases that are currently incurable. Usually, in the study of amyloid aggregation, the description of the protein’s association is in focus. Whereas the mechanism of the cross-β-structure formation, and the presence of aggregation reversibility, remain insufficiently explored. In this work, the kinetics of amyloid aggregation of apomyoglobin (ApoMb) have been studied using thioflavin fluorescence, electron microscopy, and non-denaturing electrophoresis. An analysis of the concentration dependence of the aggregation rates allows the conclusion that ApoMb amyloid formation includes the stages of conformational rearrangements in the aggregates, followed by their association and the fibril formation. The study of the mutant variants aggregation kinetics showed that the association rate is determined by the amino acids’ hydrophobicity, while the rate of conformational rearrangements is affected by the localization of the substitution. An unexpected result was the discovery that ApoMb amyloid formation is reversible, and under native-like conditions, the amyloid can dissociate, producing monomers. A consequence of the reversibility of amyloid aggregation is the presence of the monomer after aggregation completion. Since the aggregation reversibility indicates the possibility of dissociation of already formed fibrils, presented data and approaches can be useful in finding ways for amyloid diseases treatment.
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(This article belongs to the Section Biophysical Chemistry)
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Open AccessArticle
Micromagnetic Approach to the Metastability of a Magnetite Nanoparticle and Specific Loss Power as Function of the Easy-Axis Orientation
by
Nathaly Roa and Johans Restrepo
Physchem 2023, 3(3), 290-303; https://0-doi-org.brum.beds.ac.uk/10.3390/physchem3030020 - 10 Jul 2023
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Magnetic nanoparticles (MNPs) have attracted a great interest in nanomedical research. MNPs exhibit many important properties. In particular, magnetic hyperthermia for selective killing of cancer cells is one of them. In hyperthermia treatment, MNPs act as nano-heaters when they are under the influence
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Magnetic nanoparticles (MNPs) have attracted a great interest in nanomedical research. MNPs exhibit many important properties. In particular, magnetic hyperthermia for selective killing of cancer cells is one of them. In hyperthermia treatment, MNPs act as nano-heaters when they are under the influence of an alternating magnetic field (AMF). In this work, micromagnetic simulations have been used to investigate the magnetization dynamics of a single-domain nanoparticle of magnetite in an external AMF. Special attention is paid to the circumstances dealing with a dynamic phase transition (DPT). Moreover, we focus on the influence of the orientation of the magnetic easy-axis of the MNP on the dynamic magnetic properties. For amplitudes of the external AMF above a certain critical value, the system is not able to follow the magnetic field and it is found in a dynamically ordered phase, whereas for larger amplitudes, the state corresponds to a dynamically disordered phase and the magnetization follows the external AMF. Our results suggest that the way the order-disorder DPT takes place and both the metastable lifetime as well as the specific loss power (SLP) are strongly dependent on the interplay between the orientation of the magnetic easy-axis and the amplitude of the external AMF.
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Assessing Quantum Calculation Methods for the Account of Ligand Field in Lanthanide Compounds
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Ana Maria Toader, Bogdan Frecus, Corneliu Ioan Oprea and Maria Cristina Buta
Physchem 2023, 3(2), 270-289; https://0-doi-org.brum.beds.ac.uk/10.3390/physchem3020019 - 16 Jun 2023
Cited by 1
Abstract
We obtained thorough insight into the capabilities of various computational methods to account for the ligand field (LF) regime in lanthanide compounds, namely, a weakly perturbed ionic body and quasidegenerate orbital multiplets. The LF version of the angular overlap model (AOM) was considered.
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We obtained thorough insight into the capabilities of various computational methods to account for the ligand field (LF) regime in lanthanide compounds, namely, a weakly perturbed ionic body and quasidegenerate orbital multiplets. The LF version of the angular overlap model (AOM) was considered. We intentionally took very simple idealized systems, the hypothetical [TbF]2+, [TbF2]+ and [Tb(O2NO)]2+, in order to explore the details overlooked in applications on complex realistic systems. We examined the 4f and 5d orbital functions in connection to f–f and f–d transitions in the frame of the two large classes of quantum chemical methods: wave function theory (WFT) and density functional theory (DFT). WFT methods are better suited to the LF paradigm. In lanthanide compounds, DFT faces intrinsic limitations because of the frequent occurrence of quasidegenerate ground states. Such difficulties can be partly encompassed by the nonstandard control of orbital occupation schemes. Surprisingly, we found that the simplest crystal field electrostatic approximation, reconsidered with modern basis sets, works well for LF parameters in ionic lanthanide systems. We debated the largely overlooked holohedrization effect that inserts artificial inversion symmetry into standard LF Hamiltonians.
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(This article belongs to the Section Theoretical and Computational Chemistry)
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Pt and Pd Nanoparticle Crystallization in the Sol-Gel-Derived Thin SiO2 Films
by
Nadezhda Gubanova, Vasilii Matveev, Elena Grebenshchikova, Demid Kirilenko, Yana Sazonova and Olga Shilova
Physchem 2023, 3(2), 259-269; https://0-doi-org.brum.beds.ac.uk/10.3390/physchem3020018 - 15 Jun 2023
Abstract
The crystallization and distribution the features of Pt, Pd and Pt/Pd nanoparticles in spin-on glass SiO2 films were studied within a wide range of the dopant concentrations in silica sol (from 10 to 80 mol.% Pt, Pd or Pt/Pd per 100 mol.%
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The crystallization and distribution the features of Pt, Pd and Pt/Pd nanoparticles in spin-on glass SiO2 films were studied within a wide range of the dopant concentrations in silica sol (from 10 to 80 mol.% Pt, Pd or Pt/Pd per 100 mol.% Si). The grazing incidence X-ray diffraction (GIXRD) characterization revealed that the formation of 4–8 nm sized crystalline Pt, Pd and Pt/Pd nanoparticles in SiO2 films began at the dopant concentrations of at least 10 mol.% Pt and/or Pd per 100 mol.% Si. The nanoparticles obtained from sols with the lower Pt, Pd or Pt/Pd concentrations were characterized by an amorphous structure. The dopants distribution over the film thickness (~21–47 nm) was studied using X-ray reflectometry. The effect of the dopant concentration, spin-coating modes and heat treatment temperature on the film thickness was characterized. When only one of the dopants (Pt or Pd) was introduced into the silica sol, the resulting nanoparticles were preferentially localized close to the film surface. When dopants were used together, the Pt/Pd nanoparticles were distributed more evenly.
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(This article belongs to the Section Nanoscience)
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