Long-range perturbations of water structure and dynamics by the biomolecules are subject of great interests due to their potential role in biomolecular recognition. In this article, we examine the local and long-range orientational structure of water molecules surrounding the proteins with different total charges (+8, 0 and -8) both with and without the presence of physiological salt environment. A prominent population of In-oriented water molecules is observed at the first hydration shell of the proteins, irrespective of their total charges. Starting from third hydration layer, water molecules report mainly the total charge of the respective protein. This long-range ordering persists up to even ninth hydration layer without physiological salt environment and vanishes beyond the fifth hydration shell at physiological salt environment. Long-range orientational orderings around different types of surface atoms of a protein show particularly rich and heterogeneous behaviours. When the surface atom’s charge and protein’s total charge are opposite, a clear signature of tug-of-war is demonstrated in the long-range orientational ordering of water molecules. While the water reports surface atom’s charge at lower distances, water molecules at longer distances reports total charge of the protein with a crossover around 10 Å. This phenomena persist even in the presence of physiological salt environment. The evidence of destructive/constructive superposition of water-mediated orientation waves originating from two individual proteins with similar/opposite total charges is also demonstrated here. These results are important in entangling long-range water-mediated recognition phenomena among biomolecules (protein-protein, protein-ligand, protein-DNA, etc).
{"title":"Evaluating long-range orientational ordering of water around proteins: Signature of a tug-of-war scenario","authors":"Subhabrata Hazra, Biman Jana","doi":"10.1039/d4cp04451g","DOIUrl":"https://doi.org/10.1039/d4cp04451g","url":null,"abstract":"Long-range perturbations of water structure and dynamics by the biomolecules are subject of great interests due to their potential role in biomolecular recognition. In this article, we examine the local and long-range orientational structure of water molecules surrounding the proteins with different total charges (+8, 0 and -8) both with and without the presence of physiological salt environment. A prominent population of In-oriented water molecules is observed at the first hydration shell of the proteins, irrespective of their total charges. Starting from third hydration layer, water molecules report mainly the total charge of the respective protein. This long-range ordering persists up to even ninth hydration layer without physiological salt environment and vanishes beyond the fifth hydration shell at physiological salt environment. Long-range orientational orderings around different types of surface atoms of a protein show particularly rich and heterogeneous behaviours. When the surface atom’s charge and protein’s total charge are opposite, a clear signature of tug-of-war is demonstrated in the long-range orientational ordering of water molecules. While the water reports surface atom’s charge at lower distances, water molecules at longer distances reports total charge of the protein with a crossover around 10 Å. This phenomena persist even in the presence of physiological salt environment. The evidence of destructive/constructive superposition of water-mediated orientation waves originating from two individual proteins with similar/opposite total charges is also demonstrated here. These results are important in entangling long-range water-mediated recognition phenomena among biomolecules (protein-protein, protein-ligand, protein-DNA, etc).","PeriodicalId":99,"journal":{"name":"Physical Chemistry Chemical Physics","volume":"22 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-01-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143020736","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Rens Kamphorst, Maximilian F. Theisen, Ankur D. Bordoloi, Samir Salameh, Gabrie M. H. Meesters, J. Ruud van Ommen
The fractal structure of aggregates consisting of primary nanoparticles naturally arises during their synthesis. While typically considered to be a fully stochastic process, we suspect long-range interactions, in particular van der Waals forces, to induce an active pull on particles, altering the clustering process. Using an off-grid 3D model, we show that an active pull decreases the density and fractal dimension of formed clusters. These findings could not be reproduced by 2D models, which underestimate screening effects. Additionally, we determined the range within which van der Waals forces dominate the aggregation process.
{"title":"On the structure of nanoparticle clusters: effects of long-range interactions","authors":"Rens Kamphorst, Maximilian F. Theisen, Ankur D. Bordoloi, Samir Salameh, Gabrie M. H. Meesters, J. Ruud van Ommen","doi":"10.1039/d4cp04235b","DOIUrl":"https://doi.org/10.1039/d4cp04235b","url":null,"abstract":"The fractal structure of aggregates consisting of primary nanoparticles naturally arises during their synthesis. While typically considered to be a fully stochastic process, we suspect long-range interactions, in particular van der Waals forces, to induce an active pull on particles, altering the clustering process. Using an off-grid 3D model, we show that an active pull decreases the density and fractal dimension of formed clusters. These findings could not be reproduced by 2D models, which underestimate screening effects. Additionally, we determined the range within which van der Waals forces dominate the aggregation process.","PeriodicalId":99,"journal":{"name":"Physical Chemistry Chemical Physics","volume":"31 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-01-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142990828","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The Rashba effect in a nonmagnetic condensed-matter system is described by the reduction of point-group symmetries. The inversion, two-fold rotation, and reflection symmetries transforming the wavevector k to −k are identified as the origin of a degenerate state according to the time-reversal symmetry. The lack of these symmetries in a bulk system or the breaking of these in a surface system is then identified as the origin of a nondegenerate state. The surface systems Au(111), Au(110), and W(110) are assessed. The bulk system BiTeI is demonstrated for the existence of a nondegenerate state on the basis of first-principles calculations. The related issues of the heterostructure GaAs/AlGaAs and the spin Hall effect are also presented.
{"title":"Rashba effect originates from the reduction of point-group symmetries","authors":"Koshi Okamura","doi":"10.1039/d4cp04601c","DOIUrl":"https://doi.org/10.1039/d4cp04601c","url":null,"abstract":"The Rashba effect in a nonmagnetic condensed-matter system is described by the reduction of point-group symmetries. The inversion, two-fold rotation, and reflection symmetries transforming the wavevector <strong>k</strong> to −<strong>k</strong> are identified as the origin of a degenerate state according to the time-reversal symmetry. The lack of these symmetries in a bulk system or the breaking of these in a surface system is then identified as the origin of a nondegenerate state. The surface systems Au(111), Au(110), and W(110) are assessed. The bulk system BiTeI is demonstrated for the existence of a nondegenerate state on the basis of first-principles calculations. The related issues of the heterostructure GaAs/AlGaAs and the spin Hall effect are also presented.","PeriodicalId":99,"journal":{"name":"Physical Chemistry Chemical Physics","volume":"19 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-01-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142990825","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The success of halide perovskites in the field of optoelectronics has sparked extensive exploration of perovskite-type compounds, including antiperovskites and perovskite derivatives. Recently, a class of antiperovskite derivatives, X3MA3, has been proposed as potential photovoltaic absorbers. These antiperovskite derivatives share a similar crystal structure with perovskites, featuring a corner-sharing octahedral framework. In this work, we employed first-principles calculations to investigate the evolution of the structural and optoelectronic properties of four antiperovskite derivatives X3AsCl3 (X = Mg, Ca, Sr, Ba) under hydrostatic pressures ranging from 0 to 4 GPa. Our results show that these properties change linearly with pressure, with the structure and electronic properties of Ba3AsCl3 being particularly sensitive to pressure. At 4 GPa, its band gap and lattice constant decrease by 0.37 eV and 0.251 Å, respectively. Notably, Ba3AsCl3 achieves a high theoretical conversion efficiency exceeding 30% under moderate pressure. Our research suggests that Ba3AsCl3 may be a promising candidate for future optoelectronic devices, particularly under compressed epitaxial strain.
{"title":"Pressure-Dependent Optoelectronic Properties of Antiperovskite Derivatives X3AsCl3 (X = Mg, Ca, Sr, Ba): A First-Principles Study","authors":"Tao Hu, Changhe Wu, Mingjun Li, Hao Qu, Xin Luo, Yihao Hou, Shichang Li, Shengnan Duan, Dengfeng Li, Gang Tang, Chunbao Feng","doi":"10.1039/d4cp03619k","DOIUrl":"https://doi.org/10.1039/d4cp03619k","url":null,"abstract":"The success of halide perovskites in the field of optoelectronics has sparked extensive exploration of perovskite-type compounds, including antiperovskites and perovskite derivatives. Recently, a class of antiperovskite derivatives, X3MA3, has been proposed as potential photovoltaic absorbers. These antiperovskite derivatives share a similar crystal structure with perovskites, featuring a corner-sharing octahedral framework. In this work, we employed first-principles calculations to investigate the evolution of the structural and optoelectronic properties of four antiperovskite derivatives X3AsCl3 (X = Mg, Ca, Sr, Ba) under hydrostatic pressures ranging from 0 to 4 GPa. Our results show that these properties change linearly with pressure, with the structure and electronic properties of Ba3AsCl3 being particularly sensitive to pressure. At 4 GPa, its band gap and lattice constant decrease by 0.37 eV and 0.251 Å, respectively. Notably, Ba3AsCl3 achieves a high theoretical conversion efficiency exceeding 30% under moderate pressure. Our research suggests that Ba3AsCl3 may be a promising candidate for future optoelectronic devices, particularly under compressed epitaxial strain.","PeriodicalId":99,"journal":{"name":"Physical Chemistry Chemical Physics","volume":"9 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-01-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142990827","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We report a computational study of the gas-phase and water-mediated mechanisms for the oxidation of carbonyl sulfide (OCS) by the hydroxyl radical. To achieve reliable results, we employ a dual-level strategy within interpolated single-point energies (VTST-ISPE) at the CCSD(T)/aug-cc-pVTZ//M06-2X/aug-cc-pVTZ level of theory. In the gas-phase mechanism, we have determined the rate constants by Kinetic Monte Carlo simulation in the interval of temperatures of 250–550 K. The calculated rate constant, at room temperature, is 4.86 × 10−16 cm3 molecule−1 s−1, in agreement with experimental measurement: 6.00±4.00 × 10−16 cm3 molecule−1 s−1 [M. T. Leu and R. H. Smith, J. Phys. Chem., 1981, 85, 2570-2575]. The water-mediated mechanism, a more complex process than the gas-phase, revealed six reaction pathways. The application of the pre-equilibrium model allowed us to determine termolecular thermal rate constants. Considering the concentrations of water as a function of the relative humidity at 0 km altitude, we estimated effective rate constants. The magnitude of the rate coefficients for this mechanism suggested a negligible effect of the water in the OCS + OH reaction.
{"title":"Gas-phase and water-mediated mechanisms for the OCS + OH reaction","authors":"Joel Leitão Nascimento, Tiago Vinicius Alves","doi":"10.1039/d4cp04549a","DOIUrl":"https://doi.org/10.1039/d4cp04549a","url":null,"abstract":"We report a computational study of the gas-phase and water-mediated mechanisms for the oxidation of carbonyl sulfide (OCS) by the hydroxyl radical. To achieve reliable results, we employ a dual-level strategy within interpolated single-point energies (VTST-ISPE) at the CCSD(T)/aug-cc-pVTZ//M06-2X/aug-cc-pVTZ level of theory. In the gas-phase mechanism, we have determined the rate constants by Kinetic Monte Carlo simulation in the interval of temperatures of 250–550 K. The calculated rate constant, at room temperature, is 4.86 × 10−16 cm3 molecule−1 s−1, in agreement with experimental measurement: 6.00±4.00 × 10−16 cm3 molecule−1 s−1 [M. T. Leu and R. H. Smith, J. Phys. Chem., 1981, 85, 2570-2575]. The water-mediated mechanism, a more complex process than the gas-phase, revealed six reaction pathways. The application of the pre-equilibrium model allowed us to determine termolecular thermal rate constants. Considering the concentrations of water as a function of the relative humidity at 0 km altitude, we estimated effective rate constants. The magnitude of the rate coefficients for this mechanism suggested a negligible effect of the water in the OCS + OH reaction.","PeriodicalId":99,"journal":{"name":"Physical Chemistry Chemical Physics","volume":"57 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-01-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142990826","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Molecular dynamics simulations were conducted on mixtures of ionic liquid (IL) and alcohols, specifically methanol, ethanol, and 1-propanol. Two different ILs, [Mmim][MeSO4] and [Bmim][MeSO4], were used at varying alcohol mole fractions to investigate the impact of alkyl chain length of cation, alcohol type, and alcohol concentration on different structural and dynamic properties. The unique characteristics of the ILs were observed due to the varying polarity of solvents and the creation of diverse local environments surrounding the ILs. The alcohol weakens the hydrogen bond network of the IL. A better anion-cation packing was observed for [Mmim][MeSO4]-alcohol than for [Bmim][MeSO4]-alcohol mixtures. The free volume and clustering of alcohol molecules in [Mmim][MeSO4]-alcohol mixtures were stronger than those in [Bmim][MeSO4]-alcohol mixtures; these effects were stronger for mixtures containing longer-chain alcohols. Alcohol accelerates the dynamics of IL, examined in terms of the anion/cation diffusion coefficients, dynamics of ion-pair formation/rupture, and dynamics of hydrogen bond formed between anion-cation. This effect is more pronounced for mixtures of ILs with shorter-chain alcohols. These findings are consistent with the results on the structural perturbations in ILs in the presence of alcohol, i.e., weakening of hydrogen bond network in ILs upon addition of (shorter-chain) alcohols to the ILs, and reduced alcohol clustering.
{"title":"Molecular dynamics simulation of the structure and dynamics in mixtures of ionic liquids and alcohols","authors":"Farkhondeh Mozaffari","doi":"10.1039/d4cp03215b","DOIUrl":"https://doi.org/10.1039/d4cp03215b","url":null,"abstract":"Molecular dynamics simulations were conducted on mixtures of ionic liquid (IL) and alcohols, specifically methanol, ethanol, and 1-propanol. Two different ILs, [Mmim][MeSO4] and [Bmim][MeSO4], were used at varying alcohol mole fractions to investigate the impact of alkyl chain length of cation, alcohol type, and alcohol concentration on different structural and dynamic properties. The unique characteristics of the ILs were observed due to the varying polarity of solvents and the creation of diverse local environments surrounding the ILs. The alcohol weakens the hydrogen bond network of the IL. A better anion-cation packing was observed for [Mmim][MeSO4]-alcohol than for [Bmim][MeSO4]-alcohol mixtures. The free volume and clustering of alcohol molecules in [Mmim][MeSO4]-alcohol mixtures were stronger than those in [Bmim][MeSO4]-alcohol mixtures; these effects were stronger for mixtures containing longer-chain alcohols. Alcohol accelerates the dynamics of IL, examined in terms of the anion/cation diffusion coefficients, dynamics of ion-pair formation/rupture, and dynamics of hydrogen bond formed between anion-cation. This effect is more pronounced for mixtures of ILs with shorter-chain alcohols. These findings are consistent with the results on the structural perturbations in ILs in the presence of alcohol, i.e., weakening of hydrogen bond network in ILs upon addition of (shorter-chain) alcohols to the ILs, and reduced alcohol clustering.","PeriodicalId":99,"journal":{"name":"Physical Chemistry Chemical Physics","volume":"26 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-01-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142990830","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The structural stability of the energetic material 2,2',4,4',6,6'-hexanitrostilbene (trans-HNS) under high pressure is critical for optimizing its detonation performance and low sensitivity. However, its structural response to external pressure has not been sufficiently investigated. In this study, high-pressure single-crystal X-ray diffraction data of trans-HNS demonstrate that the sample exhibits pronounced anisotropic strain, demonstrating an unusual negative linear compressibility (NLC) along the c axis, with a coefficient of -4.4(5) TPa-1 within the range of 0.1 MPa to ~2.90 GPa. The expansion of the c axis is attributed to significant reorientations of the HNS molecules towards the bc plane within the herringbone network. Subsequently, the NLC reverts to the PLC under further compression due to the limited space within the lattice, which restricts the reorientations of irregularly shaped HNS molecules. The enhanced CH∙∙∙O intermolecular contacts facilitate the rotations of the -NO₂ nitro groups relative to the phenyl rings, as demonstrated by the conformational changes observed in the HNS molecules through Raman spectroscopy measurements. In addition, the band gap of the sample gradually decreases, reducing by ~8.8% in the range of 0.1 MPa and 10.01 GPa. However, the sample could not be returned to its initial state once the pressure exceeded 10 GPa, which is most likely due to the occurrence of a chemical reaction or amorphization. Our results indicate that the NLC behavior may present in a wide range of unexamined herringbone-type energetic molecular crystals with different molecular structures.
{"title":"Negative linear compressibility and structural stability of the energetic material trans-hexanitrostilbene under pressure","authors":"Xinglong Deng, Dong Li, Boyang Fu, Yu Liu, Weilong He, Shourui Li, Weizhao Cai","doi":"10.1039/d4cp04470c","DOIUrl":"https://doi.org/10.1039/d4cp04470c","url":null,"abstract":"The structural stability of the energetic material 2,2',4,4',6,6'-hexanitrostilbene (trans-HNS) under high pressure is critical for optimizing its detonation performance and low sensitivity. However, its structural response to external pressure has not been sufficiently investigated. In this study, high-pressure single-crystal X-ray diffraction data of trans-HNS demonstrate that the sample exhibits pronounced anisotropic strain, demonstrating an unusual negative linear compressibility (NLC) along the c axis, with a coefficient of -4.4(5) TPa-1 within the range of 0.1 MPa to ~2.90 GPa. The expansion of the c axis is attributed to significant reorientations of the HNS molecules towards the bc plane within the herringbone network. Subsequently, the NLC reverts to the PLC under further compression due to the limited space within the lattice, which restricts the reorientations of irregularly shaped HNS molecules. The enhanced CH∙∙∙O intermolecular contacts facilitate the rotations of the -NO₂ nitro groups relative to the phenyl rings, as demonstrated by the conformational changes observed in the HNS molecules through Raman spectroscopy measurements. In addition, the band gap of the sample gradually decreases, reducing by ~8.8% in the range of 0.1 MPa and 10.01 GPa. However, the sample could not be returned to its initial state once the pressure exceeded 10 GPa, which is most likely due to the occurrence of a chemical reaction or amorphization. Our results indicate that the NLC behavior may present in a wide range of unexamined herringbone-type energetic molecular crystals with different molecular structures.","PeriodicalId":99,"journal":{"name":"Physical Chemistry Chemical Physics","volume":"13 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-01-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142990832","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
There has been a significant recent surge in the number of studies interrogating chiral molecules in the gas phase using photoelectron circular dichroism (PECD) and related techniques. These investigations have revealed new fundamental insights into the structure and dynamics of chiral species and, furthermore, have the potential to revolutionize the field of chiral analysis for more practical and industrial applications. As it has been just over 20 years since the first PECD imaging experiments were demonstrated – and 10 years since the last dedicated general perspective article on the topic – a new overview now seems extremely timely. This article will introduce PECD to the general reader and give a synopsis of developments in the field, focusing particularly on the last decade, where the use of multiphoton ionization schemes has brought PECD to a wider experimental audience. We will discuss the novel applications of the general methodology and highlight the challenges that must be overcome to fully cement PECD and adjacent techniques as powerful chiral analysis probes.
{"title":"Two decades of imaging photoelectron circular dichroism: from first principles to future perspectives","authors":"Chris Sparling, Dave Townsend","doi":"10.1039/d4cp03770g","DOIUrl":"https://doi.org/10.1039/d4cp03770g","url":null,"abstract":"There has been a significant recent surge in the number of studies interrogating chiral molecules in the gas phase using photoelectron circular dichroism (PECD) and related techniques. These investigations have revealed new fundamental insights into the structure and dynamics of chiral species and, furthermore, have the potential to revolutionize the field of chiral analysis for more practical and industrial applications. As it has been just over 20 years since the first PECD imaging experiments were demonstrated – and 10 years since the last dedicated general perspective article on the topic – a new overview now seems extremely timely. This article will introduce PECD to the general reader and give a synopsis of developments in the field, focusing particularly on the last decade, where the use of multiphoton ionization schemes has brought PECD to a wider experimental audience. We will discuss the novel applications of the general methodology and highlight the challenges that must be overcome to fully cement PECD and adjacent techniques as powerful chiral analysis probes.","PeriodicalId":99,"journal":{"name":"Physical Chemistry Chemical Physics","volume":"30 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-01-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142990822","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Anna Yu. Solovyova, Elena Grokhotova, Alexey Olegovich Ivanov, Ekaterina Alexandrovna Elfimova
This work is devoted to the study of the static magnetization of immobilized multi-core particles (MCPs) and their ensembles. These objects model aggregates of superparamagnetic nanoparticles that are taken up by biological cells and subsequently used, for example, as magnetoactive agents for cell imaging. In this study, we derive an analytical formula that allows us to predict the static magnetization of MCPs consisting of immobilized granules, in which the magnetic moment rotates freely via the N'{e}el mechanism. The formula takes into account intergranule dipole-dipole interactions at the level of pair correlations and is suitable for determining the magnetization of MCPs with any structure. The theory is tested using Monte Carlo computer simulations on a series of MCP samples with 4 and 7 superparamagnetic granules. The results demonstrate that the formulas accurately describe the magnetization of MCPs with the intergranule dipolar coupling constant $lambda leq 2$. We propose a method for determining the magnetization of an ensemble of non-interacting immobilized MCPs with interacting granules by identifying this system with an ensemble of single-core immobilized non-interacting superparamagnetic particles for which the effective magnetic anisotropy parameter is determined. The results obtained in this work represent a significant step towards predicting the magnetic response of MCPs in biological media, such as biological cells.
{"title":"Magnetization of immobilized multi-core particles with varying internal structures","authors":"Anna Yu. Solovyova, Elena Grokhotova, Alexey Olegovich Ivanov, Ekaterina Alexandrovna Elfimova","doi":"10.1039/d4cp03995e","DOIUrl":"https://doi.org/10.1039/d4cp03995e","url":null,"abstract":"This work is devoted to the study of the static magnetization of immobilized multi-core particles (MCPs) and their ensembles. These objects model aggregates of superparamagnetic nanoparticles that are taken up by biological cells and subsequently used, for example, as magnetoactive agents for cell imaging. In this study, we derive an analytical formula that allows us to predict the static magnetization of MCPs consisting of immobilized granules, in which the magnetic moment rotates freely via the N'{e}el mechanism. The formula takes into account intergranule dipole-dipole interactions at the level of pair correlations and is suitable for determining the magnetization of MCPs with any structure. The theory is tested using Monte Carlo computer simulations on a series of MCP samples with 4 and 7 superparamagnetic granules. The results demonstrate that the formulas accurately describe the magnetization of MCPs with the intergranule dipolar coupling constant $lambda leq 2$. We propose a method for determining the magnetization of an ensemble of non-interacting immobilized MCPs with interacting granules by identifying this system with an ensemble of single-core immobilized non-interacting superparamagnetic particles for which the effective magnetic anisotropy parameter is determined. The results obtained in this work represent a significant step towards predicting the magnetic response of MCPs in biological media, such as biological cells.","PeriodicalId":99,"journal":{"name":"Physical Chemistry Chemical Physics","volume":"37 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-01-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142990829","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In this study, we investigate the adsorption properties of CO, NH₃, and NO gases on Ti₃C₂O₂ MXene surfaces through density functional theory (DFT) calculations. A comprehensive analysis of the adsorption preferences, electronic properties, work function (φ), sensitivity (S), and recovery time (τ) was conducted, focusing on the effects of biaxial strain (ε) ranging from -2% to 4%. At free strain, toxic gases can adsorb onto the Ti₃C₂O₂ surface, with adsorption energies (Ead) of -0.096 eV (CO), -0.344 eV (NH₃), and -0.349 eV (NO), indicating moderate interactions between NH₃, NO and the Ti₃C₂O₂ surface, while CO displays weaker physisorption. Electron density difference (EDD) and electron localization function (ELF) analyses underscore the electron transfer mechanisms, supporting the enhanced sensitivity of Ti₃C₂O₂ for NH₃ and NO detection. The influence of ε on gas adsorption behaviour was also studied, demonstrating that tensile strain enhances NH₃ adsorption (Ead = -0.551 eV at ε = 4%), while NO exhibits an inverse trend under compressive strain (Ead = -0.403 eV at ε = -2%). The S based on a change rate of φ was evaluated to be around 12% and 6% for NH₃ and NO, respectively within the calculated strain range, indicating sufficient detection capability. Additionally, the τ for NH₃ and NO detection was computed. At 0% strain and 300 K, the τ values for NH₃ and NO are in the microsecond range, suggesting that detecting these gases under normal conditions poses a challenge. However, strain-tuned Ti₃C₂O₂ and lowered temperature enhance gas sensing performance, with increased τ values at tensile strain for NH₃ and compressive strain for NO. These results suggest that Ti₃C₂O₂ MXene, when tuned with biaxial strain, is a promising candidate for detecting NH₃ and NO at low to room temperatures.
在这项研究中，我们通过密度泛函理论（DFT）计算研究了CO、NH₃和NO气体在Ti₃C₂O₂MXene表面的吸附特性。综合分析了吸附偏好、电子性质、功函数（φ）、灵敏度(S)和恢复时间（τ），重点研究了-2% ~ 4%范围内双轴应变（ε）的影响。在自由应变下，有毒气体可以吸附在Ti₃C₂O₂表面，其吸附能（Ead）为-0.096 eV （CO）、-0.344 eV （NH₃）和-0.349 eV (NO)，表明NH₃、NO与Ti₃C₂O₂表面的相互作用适中，而CO的物理吸附作用较弱。电子密度差（EDD）和电子定位函数（ELF）分析强调了电子转移机制，支持Ti₃C₂O₂对NH₃和NO检测的灵敏度提高。研究了ε对气体吸附行为的影响，表明拉伸应变增强NH₃的吸附（ε = 4%时Ead = -0.551 eV），而压缩应变增强NH₃的吸附（ε = -2%时Ead = -0.403 eV）。在计算的应变范围内，基于φ变化率的S对NH₃和NO分别约为12%和6%，表明有足够的检测能力。此外，计算了NH₃和NO检测的τ。在0%应变和300 K下，NH₃和NO的τ值在微秒范围内，这表明在正常条件下检测这些气体是一个挑战。然而，应变调整的Ti₃C₂O₂和降低的温度增强了气敏性能，NH₃的拉伸应变τ值和NO的压缩应变τ值都增加了。这些结果表明，当用双轴应变调谐时，Ti₃C₂O₂MXene是在低温到室温下检测NH₃和NO的有希望的候选者。
{"title":"Enhanced NH₃ and NO Sensing Performance of Ti₃C₂O₂ MXene by Biaxial Strain: Insights from First-Principles Calculations","authors":"Satchakorn Khammuang, Kantaphong Wongphen, Tanveer Hussain, Komsilp Kotmool","doi":"10.1039/d4cp04127e","DOIUrl":"https://doi.org/10.1039/d4cp04127e","url":null,"abstract":"In this study, we investigate the adsorption properties of CO, NH₃, and NO gases on Ti₃C₂O₂ MXene surfaces through density functional theory (DFT) calculations. A comprehensive analysis of the adsorption preferences, electronic properties, work function (φ), sensitivity (S), and recovery time (τ) was conducted, focusing on the effects of biaxial strain (ε) ranging from -2% to 4%. At free strain, toxic gases can adsorb onto the Ti₃C₂O₂ surface, with adsorption energies (Ead) of -0.096 eV (CO), -0.344 eV (NH₃), and -0.349 eV (NO), indicating moderate interactions between NH₃, NO and the Ti₃C₂O₂ surface, while CO displays weaker physisorption. Electron density difference (EDD) and electron localization function (ELF) analyses underscore the electron transfer mechanisms, supporting the enhanced sensitivity of Ti₃C₂O₂ for NH₃ and NO detection. The influence of ε on gas adsorption behaviour was also studied, demonstrating that tensile strain enhances NH₃ adsorption (Ead = -0.551 eV at ε = 4%), while NO exhibits an inverse trend under compressive strain (Ead = -0.403 eV at ε = -2%). The S based on a change rate of φ was evaluated to be around 12% and 6% for NH₃ and NO, respectively within the calculated strain range, indicating sufficient detection capability. Additionally, the τ for NH₃ and NO detection was computed. At 0% strain and 300 K, the τ values for NH₃ and NO are in the microsecond range, suggesting that detecting these gases under normal conditions poses a challenge. However, strain-tuned Ti₃C₂O₂ and lowered temperature enhance gas sensing performance, with increased τ values at tensile strain for NH₃ and compressive strain for NO. These results suggest that Ti₃C₂O₂ MXene, when tuned with biaxial strain, is a promising candidate for detecting NH₃ and NO at low to room temperatures.","PeriodicalId":99,"journal":{"name":"Physical Chemistry Chemical Physics","volume":"46 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-01-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142990831","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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