Markus Bauer, Raphaela Post, Luis Ignacio Domenianni, Peter Vöhringer
The binding of carbon dioxide to a transition metal is a complex phenomenon that involves a major redistribution of electron density between the metal center and the triatomic ligand. The chemical reduction of the ligand reveals itself unambiguously by an angular distortion of the CO2-molecule as a result of the occupation of an anti-bonding π-orbital and a shift of its antisymmetric stretching vibration, ν3, to lower wavenumbers. Here, we generate a carbon dioxide complex of the heavier group-10 metal, platinum, by ultrafast electronic excitation and cleavage of CO2 from the photolabile oxalate precursor, oxaliplatin, and monitored the ensuing primary dynamics with ultrafast mid-infrared spectroscopy. A neutral and thermally relaxed CO2-molecule is detected in the ν3-region within 5 ps after impulsive excitation with 266 nm light. Concurrently, an induced absorption peaking at 1717 cm─1 is observed, which is distinctly up-shifted relative to the oxalate stretching bands of the precursor and which resembles the C=O stretching absorption of organic ketones. Accompanying density functional theory suggests that the 1717 cm─1-absorption arises from a Pt-CO2 product complex featuring a side-on binding mode, which can indeed be regarded as a ketone ; specifically, as the metalla-α-lactone, 1-oxa-3-platinacyclopropan-2-one.
{"title":"Photoinduced formation of a platina-α-lactone – a carbon dioxide complex of platinum. Insights from femtosecond mid-infrared spectroscopy","authors":"Markus Bauer, Raphaela Post, Luis Ignacio Domenianni, Peter Vöhringer","doi":"10.1039/d4cp03840a","DOIUrl":"https://doi.org/10.1039/d4cp03840a","url":null,"abstract":"The binding of carbon dioxide to a transition metal is a complex phenomenon that involves a major redistribution of electron density between the metal center and the triatomic ligand. The chemical reduction of the ligand reveals itself unambiguously by an angular distortion of the CO2-molecule as a result of the occupation of an anti-bonding π-orbital and a shift of its antisymmetric stretching vibration, ν3, to lower wavenumbers. Here, we generate a carbon dioxide complex of the heavier group-10 metal, platinum, by ultrafast electronic excitation and cleavage of CO2 from the photolabile oxalate precursor, oxaliplatin, and monitored the ensuing primary dynamics with ultrafast mid-infrared spectroscopy. A neutral and thermally relaxed CO2-molecule is detected in the ν3-region within 5 ps after impulsive excitation with 266 nm light. Concurrently, an induced absorption peaking at 1717 cm─1 is observed, which is distinctly up-shifted relative to the oxalate stretching bands of the precursor and which resembles the C=O stretching absorption of organic ketones. Accompanying density functional theory suggests that the 1717 cm─1-absorption arises from a Pt-CO2 product complex featuring a side-on binding mode, which can indeed be regarded as a ketone ; specifically, as the metalla-α-lactone, 1-oxa-3-platinacyclopropan-2-one.","PeriodicalId":99,"journal":{"name":"Physical Chemistry Chemical Physics","volume":"17 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142968508","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}
Ai-Qun Pan, Xichun Liu, Hui Han, Shu-Qin Gao, Ying-Wu Lin
Globin X is a newly discovered member of the globin family, where its structure and function are not fully understood. In this study, we performed protein modelling studies using Alphafold3 and molecular dynamics simulations, which suggested that the protein adopts a typical globin fold, with the formation of a potential disulfide bond of Cys65 and Cys141. To elucidate the role of this unique disulfide in protein structure and stability, we constructed a double mutant of C65S/C141S by mutating the two cysteine residues to serine. As suggested by protein mass, ultraviolet-visible (UV-Vis) and circular dichroism (CD) spectroscopy analyses, the potential disulfide bond has minimal effect on the overall protein structure, but its absence reduces the protein stability. Electron paramagnetic resonance (EPR) analysis also revealed an increase in the proportion of high-spin state heme iron, which accelerates the rate of heme degradation in reaction with H2O2. This study highlights the critical role of the Cys65-Cys141 in maintaining the stability of globin X and the bis-His heme coordination state, providing insights into the structure-function relationship of the newly discovered globin.
{"title":"Disruption of a potential disulfide bond of Cys65-Cys141 on the structure and stability of globin X from zebrafish","authors":"Ai-Qun Pan, Xichun Liu, Hui Han, Shu-Qin Gao, Ying-Wu Lin","doi":"10.1039/d4cp04253k","DOIUrl":"https://doi.org/10.1039/d4cp04253k","url":null,"abstract":"Globin X is a newly discovered member of the globin family, where its structure and function are not fully understood. In this study, we performed protein modelling studies using Alphafold3 and molecular dynamics simulations, which suggested that the protein adopts a typical globin fold, with the formation of a potential disulfide bond of Cys65 and Cys141. To elucidate the role of this unique disulfide in protein structure and stability, we constructed a double mutant of C65S/C141S by mutating the two cysteine residues to serine. As suggested by protein mass, ultraviolet-visible (UV-Vis) and circular dichroism (CD) spectroscopy analyses, the potential disulfide bond has minimal effect on the overall protein structure, but its absence reduces the protein stability. Electron paramagnetic resonance (EPR) analysis also revealed an increase in the proportion of high-spin state heme iron, which accelerates the rate of heme degradation in reaction with H2O2. This study highlights the critical role of the Cys65-Cys141 in maintaining the stability of globin X and the bis-His heme coordination state, providing insights into the structure-function relationship of the newly discovered globin.","PeriodicalId":99,"journal":{"name":"Physical Chemistry Chemical Physics","volume":"4 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142968561","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}
Santhosh K. Matam, Lotfi Boudjema, Matthew G. Quesne, James D. Taylor, C. Richard A. Catlow
Methanol adsorption isotherms of fresh f-ZSM-5 and steamed s-ZSM-5 (Si/Al ≈ 40) are investigated experimentally at room temperature under equilibrium and by grand canonical Monte Carlo (GCMC) simulations with the aim of understanding the adsorption capacity, geometry and sites as a function of steam treatment (at 573 K for 24 h). Methanol adsorption energies calculated by GCMC are complemented by density functional theory (DFT) employing both periodic and quantum mechanics/molecular mechanics (QM/MM) techniques. Physical and textural properties of f-ZSM-5 and s-ZSM-5 are characterised by diffuse reflectance infrared Fourier transformed spectroscopy (DRIFTS) and N2-physisorption, which form a basis to construct models for f-ZSM-5 and s-ZSM-5 to simulate methanol adsorption isotherms by GCMC. Both Brønsted and silanol hydroxyls are observed in f-ZSM-5 and s-ZSM-5 by DRIFTS; however, these species, especially Brønsted species, decreased considerably upon steam treatment in s-ZSM-5 due to dealumination. Although the total pore volume and mesoporosity increased in s-ZSM-5 as compared in f-ZSM-5, the total surface area (375 m2 g−1) of the steamed zeolite is lower than the fresh zeolite (416 m2 g−1) due to pore plugging caused by partial dislodgement of framework Al on steam treatment. Implications of the steam treatment on the methanol adsorption capacity of the zeolites are reflected in the experimental methanol adsorption isotherms, collected (in the pressure range between 0 and 12 kPa) at room temperature under equilibrium, which find that the overall methanol uptake is lower for s-ZSM-5 than for f-ZSM-5. The GCMC simulations show that the nature, location and distribution of acidic hydroxyls determine the methanol adsorption capacity, geometry and hence the isotherm profiles of f-ZSM-5 and s-ZSM-5. The GCMC simulations provide insight into the different adsorption sites and their reactivity towards methanol which paves the way not only to describe the isotherms of f-ZSM-5 and s-ZSM-5 but also offers a means to understand better the deactivation of ZSM-5 by steam (leading to dealumination) and subtle differences in surface adsorbed species on ZSM-5 procured from different sources.
{"title":"A complementary experimental and computational study on methanol adsorption isotherms of H-ZSM-5","authors":"Santhosh K. Matam, Lotfi Boudjema, Matthew G. Quesne, James D. Taylor, C. Richard A. Catlow","doi":"10.1039/d4cp03761h","DOIUrl":"https://doi.org/10.1039/d4cp03761h","url":null,"abstract":"Methanol adsorption isotherms of fresh f-ZSM-5 and steamed s-ZSM-5 (Si/Al ≈ 40) are investigated experimentally at room temperature under equilibrium and by grand canonical Monte Carlo (GCMC) simulations with the aim of understanding the adsorption capacity, geometry and sites as a function of steam treatment (at 573 K for 24 h). Methanol adsorption energies calculated by GCMC are complemented by density functional theory (DFT) employing both periodic and quantum mechanics/molecular mechanics (QM/MM) techniques. Physical and textural properties of f-ZSM-5 and s-ZSM-5 are characterised by diffuse reflectance infrared Fourier transformed spectroscopy (DRIFTS) and N<small><sub>2</sub></small>-physisorption, which form a basis to construct models for f-ZSM-5 and s-ZSM-5 to simulate methanol adsorption isotherms by GCMC. Both Brønsted and silanol hydroxyls are observed in f-ZSM-5 and s-ZSM-5 by DRIFTS; however, these species, especially Brønsted species, decreased considerably upon steam treatment in s-ZSM-5 due to dealumination. Although the total pore volume and mesoporosity increased in s-ZSM-5 as compared in f-ZSM-5, the total surface area (375 m<small><sup>2</sup></small> g<small><sup>−1</sup></small>) of the steamed zeolite is lower than the fresh zeolite (416 m<small><sup>2</sup></small> g<small><sup>−1</sup></small>) due to pore plugging caused by partial dislodgement of framework Al on steam treatment. Implications of the steam treatment on the methanol adsorption capacity of the zeolites are reflected in the experimental methanol adsorption isotherms, collected (in the pressure range between 0 and 12 kPa) at room temperature under equilibrium, which find that the overall methanol uptake is lower for s-ZSM-5 than for f-ZSM-5. The GCMC simulations show that the nature, location and distribution of acidic hydroxyls determine the methanol adsorption capacity, geometry and hence the isotherm profiles of f-ZSM-5 and s-ZSM-5. The GCMC simulations provide insight into the different adsorption sites and their reactivity towards methanol which paves the way not only to describe the isotherms of f-ZSM-5 and s-ZSM-5 but also offers a means to understand better the deactivation of ZSM-5 by steam (leading to dealumination) and subtle differences in surface adsorbed species on ZSM-5 procured from different sources.","PeriodicalId":99,"journal":{"name":"Physical Chemistry Chemical Physics","volume":"48 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142975329","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}
Vishva Jeet Anand, Vivek Kumar, Amit Kumar, Pradeep Kumar
The present work employs CCSD(T)/CBS//M06-2X/aug-cc-pVTZ level of theory to investigate the effect of a water monomer (WM) and dimer (WD) on the oxidation of nitrous acid (HONO) by Criegee intermediate (CH 2 OO). The present work suggests that similar to the uncatalyzed path, water catalyzed reaction can also proceed via two paths, i.e., the oxygen atom transfer (OAT) and the hydrogen atom transfer (HAT) path. In addition, here also, the HAT path dominates over OAT path. Besides, our study suggests that the rate of the water catalyzed reaction of the Crigee intermediate and HONO can be more than an order of magnitude higher than the corresponding uncatalyzed reaction.
{"title":"Water as a catalyst in the reaction of nitrous acid (HONO) and Criegee intermediate (CH 2 OO)","authors":"Vishva Jeet Anand, Vivek Kumar, Amit Kumar, Pradeep Kumar","doi":"10.1039/d4cp04117h","DOIUrl":"https://doi.org/10.1039/d4cp04117h","url":null,"abstract":"The present work employs CCSD(T)/CBS//M06-2X/aug-cc-pVTZ level of theory to investigate the effect of a water monomer (WM) and dimer (WD) on the oxidation of nitrous acid (HONO) by Criegee intermediate (CH 2 OO). The present work suggests that similar to the uncatalyzed path, water catalyzed reaction can also proceed via two paths, i.e., the oxygen atom transfer (OAT) and the hydrogen atom transfer (HAT) path. In addition, here also, the HAT path dominates over OAT path. Besides, our study suggests that the rate of the water catalyzed reaction of the Crigee intermediate and HONO can be more than an order of magnitude higher than the corresponding uncatalyzed reaction.","PeriodicalId":99,"journal":{"name":"Physical Chemistry Chemical Physics","volume":"21 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142968384","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 excellent optical and electronic properties of halide perovskite materials have attracted researchers to investigate this particular field. However, the instability in ambient conditions and toxicity of materials like lead have given some setbacks to commercial use. To overcome these issues, perovskite-inspired materials with less toxic and excellent air-stable materials are being studied. Double perovskite materials are one of the perovskite materials. In this study, we have synthesized air-stable double perovskite Cs2CuBiBr6 using a solution process approach. The characterization of the material revealed that it has excellent crystallinity and high stability. The material shows excellent optical and electronic properties. It can be used in resistive memory devices. It shows stable current-voltage characteristics and analog switching. The ion migration through the active layer and accumulation of charge near the electrode region are the reasons behind the resistive switching.
{"title":"Air-stable Double Halide Perovskite Cs2CuBiBr6: Synthesis and Memristor Application","authors":"Atanu Betal, Anupam Chetia, Dibyajyoti Saikia, Krishnendu Karmakar, Ganesh Bera, Neha V Dambhare, Arup Kumar Rath, Satyajit Sahu","doi":"10.1039/d4cp04639k","DOIUrl":"https://doi.org/10.1039/d4cp04639k","url":null,"abstract":"The excellent optical and electronic properties of halide perovskite materials have attracted researchers to investigate this particular field. However, the instability in ambient conditions and toxicity of materials like lead have given some setbacks to commercial use. To overcome these issues, perovskite-inspired materials with less toxic and excellent air-stable materials are being studied. Double perovskite materials are one of the perovskite materials. In this study, we have synthesized air-stable double perovskite Cs2CuBiBr6 using a solution process approach. The characterization of the material revealed that it has excellent crystallinity and high stability. The material shows excellent optical and electronic properties. It can be used in resistive memory devices. It shows stable current-voltage characteristics and analog switching. The ion migration through the active layer and accumulation of charge near the electrode region are the reasons behind the resistive switching.","PeriodicalId":99,"journal":{"name":"Physical Chemistry Chemical Physics","volume":"87 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142968514","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}
Juan Cui, Huan Zheng, Miao Zheng, Huajie Song, Yu Yang
Strain engineering is an effective method to modulate the electronic properties of two-dimensional materials. In this study, we theoretically studied the carrier mobility of the PdAs2 monolayer under different biaxial tensile strains based on the state-of-the-art electron–phonon coupling theory. We observe that the carrier mobility is largely enhanced for both n-type and p-type PdAs2 monolayers. The electron mobility experiences a rapid increase under tensile strain over 2% and can reach 670 cm2 V−1 s−1 under 4% strain, which is higher than common 2D semiconductors. The rapid increase of electron mobility originates from the ordering change of the conduction bands and the suppressed interband scattering. Our study highlights the role of electron–phonon coupling in the electron transport and provides new insights into the optimization of carrier mobility.
{"title":"Enhanced carrier mobility in strain-engineered PdAs2 monolayer boosted by suppressing interband scattering","authors":"Juan Cui, Huan Zheng, Miao Zheng, Huajie Song, Yu Yang","doi":"10.1039/d4cp04157g","DOIUrl":"https://doi.org/10.1039/d4cp04157g","url":null,"abstract":"Strain engineering is an effective method to modulate the electronic properties of two-dimensional materials. In this study, we theoretically studied the carrier mobility of the PdAs<small><sub>2</sub></small> monolayer under different biaxial tensile strains based on the state-of-the-art electron–phonon coupling theory. We observe that the carrier mobility is largely enhanced for both n-type and p-type PdAs<small><sub>2</sub></small> monolayers. The electron mobility experiences a rapid increase under tensile strain over 2% and can reach 670 cm<small><sup>2</sup></small> V<small><sup>−1</sup></small> s<small><sup>−1</sup></small> under 4% strain, which is higher than common 2D semiconductors. The rapid increase of electron mobility originates from the ordering change of the conduction bands and the suppressed interband scattering. Our study highlights the role of electron–phonon coupling in the electron transport and provides new insights into the optimization of carrier mobility.","PeriodicalId":99,"journal":{"name":"Physical Chemistry Chemical Physics","volume":"29 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142968511","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}
Yun Dong, Bo Shi, Yi Tao, Xinyi Tang, Jinguang Wang, Futian Yang, Yifan Liu
Previous researchers have conducted extensive investigations on the impact of various working conditions on fatigue damage. However, further research is still needed to understand the underlying mechanism of how the excitation frequency of cyclic loading affects the fatigue life. This article systematically discloses the phononic origin of atomic scale fatigue resonance, focusing on a single-layer molybdenum disulfide (SL MoS2) as prototypical material. We first devise a method to initiate free vibration in SL MoS2 system by applying an initial condition, enabling the measurement of its natural vibration period and calculation of natural frequency. When excitation frequency matches natural frequency and its harmonics, primary and sub-harmonic resonances occur, leading to a notable decrease in fatigue life. Moreover, when the excitation frequency approaches but has not yet reached the natural frequency, the beat vibration phenomenon occurs, characterized by periodic changes of amplitude. The excitation amplitude and frequency exert pivotal influences on determining the vibration amplitude and the onset of vibration instability. Finally, the phonon behaviors across varying excitation frequencies and different fatigue stages are investigated. During resonances, excited phonons are not only distributed at the excitation frequency, but also at the harmonics of natural frequency. This resonance effect causes a significant amplification of lattice vibrations, accompanied by more phonons being excited, resulting in a faster entry into the vibrational instability stage. Our study offers valuable insights into regulating fatigue performance of nanomaterials, thus playing a significant guiding role in the application of nanomaterials.
{"title":"Phononic origin of resonance in atomic scale fatigue of MoS2","authors":"Yun Dong, Bo Shi, Yi Tao, Xinyi Tang, Jinguang Wang, Futian Yang, Yifan Liu","doi":"10.1039/d4cp04262j","DOIUrl":"https://doi.org/10.1039/d4cp04262j","url":null,"abstract":"Previous researchers have conducted extensive investigations on the impact of various working conditions on fatigue damage. However, further research is still needed to understand the underlying mechanism of how the excitation frequency of cyclic loading affects the fatigue life. This article systematically discloses the phononic origin of atomic scale fatigue resonance, focusing on a single-layer molybdenum disulfide (SL MoS2) as prototypical material. We first devise a method to initiate free vibration in SL MoS2 system by applying an initial condition, enabling the measurement of its natural vibration period and calculation of natural frequency. When excitation frequency matches natural frequency and its harmonics, primary and sub-harmonic resonances occur, leading to a notable decrease in fatigue life. Moreover, when the excitation frequency approaches but has not yet reached the natural frequency, the beat vibration phenomenon occurs, characterized by periodic changes of amplitude. The excitation amplitude and frequency exert pivotal influences on determining the vibration amplitude and the onset of vibration instability. Finally, the phonon behaviors across varying excitation frequencies and different fatigue stages are investigated. During resonances, excited phonons are not only distributed at the excitation frequency, but also at the harmonics of natural frequency. This resonance effect causes a significant amplification of lattice vibrations, accompanied by more phonons being excited, resulting in a faster entry into the vibrational instability stage. Our study offers valuable insights into regulating fatigue performance of nanomaterials, thus playing a significant guiding role in the application of nanomaterials.","PeriodicalId":99,"journal":{"name":"Physical Chemistry Chemical Physics","volume":"68 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142968513","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}
A theory of singlet fission in carotenoid dimers is presented which aims to explain the mechanism behind the creation of two uncorrelated triplets. Following the excitation of a carotenoid chain “bright” n1B+u state, there is ultrafast internal conversion to the intrachain “dark” 11B−u triplet-pair state. This strongly exchange-coupled state evolves into a pair of triplets on separate chains and spin-decoheres to form a pair of single, unentangled triplets, corresponding to complete singlet fission. The simulated EPR spectrum for parallel lycopene monomers in a dimer (i.e., H-aggregate) shows a distinct spectral signal due to the residual exchange coupling between the triplet-pairs on seperate carotenoid chains.
{"title":"Singlet fission in carotenoid dimers – the role of the exchange and dipolar interactions","authors":"Alexandru G. Ichert, William Barford","doi":"10.1039/d4cp04445b","DOIUrl":"https://doi.org/10.1039/d4cp04445b","url":null,"abstract":"A theory of singlet fission in carotenoid dimers is presented which aims to explain the mechanism behind the creation of two uncorrelated triplets. Following the excitation of a carotenoid chain “bright” <em>n</em><small><sup>1</sup></small>B<small><sup>+</sup></small><small><sub>u</sub></small> state, there is ultrafast internal conversion to the intrachain “dark” 1<small><sup>1</sup></small>B<small><sup>−</sup></small><small><sub>u</sub></small> triplet-pair state. This strongly exchange-coupled state evolves into a pair of triplets on separate chains and spin-decoheres to form a pair of single, unentangled triplets, corresponding to complete singlet fission. The simulated EPR spectrum for parallel lycopene monomers in a dimer (<em>i.e.</em>, H-aggregate) shows a distinct spectral signal due to the residual exchange coupling between the triplet-pairs on seperate carotenoid chains.","PeriodicalId":99,"journal":{"name":"Physical Chemistry Chemical Physics","volume":"6 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142968504","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}
Deep eutectic solvents (DESs) have emerged as solubilizing media of intense interest due partly to their easily tailorable physicochemical properties. Extensive H-bonding between the constituents in a two-constituent system is the major driving force for the formation of the DES. Addition of ethanolamine (ETA), a compound having H-bonding capabilities, to the DESs composed of a terpene [menthol (Men) or thymol (Thy)] and a fatty acid [n-decanoic acid (DA)] results in unprecedented increase in dynamic viscosity due to the extensive rearrangement in the H-bonding network and other interactions within the system while the liquid mixture still behaves as a Newtonian fluid. For the non-DA DES constituted of Men and Thy this behavior is not observed. Visual color appearance, density and electrical conductivity measurements, UV-Vis and FTIR absorbance, differential scanning calorimetry, and empirical Kamlet-Taft parameters of the ETA-added DA-based DESs reveal the microstructural changes effectively. Cybotactic regions of the fluorescence microfluidity probes [1,3-bis(1-pyrenyl)propane - an intramolecular excimer forming probe as well as perylene and 1,6-diphenylhexatriene - well-established anisotropy probes] also manifest the unprecedented increase in the viscosity of the DA-based DES system upon ETA addition. The carboxylic acid functionality of the DA plays a crucial role in bringing microstructural changes within the system as ETA is added. Physicochemical properties of DES systems can be effectively manipulated by not only changing the constituents and their compositions, but also by judicious addition of a co-solute/co-solvent. The work offers easy and efficient way to favorably tailor the properties of interest of these environmentally-benign media.
{"title":"Ethanolamine-mediated microstructural transitions within terpenoid- and fatty acid-based deep eutectic solvents","authors":"Anjali Anjali, Siddharth Pandey","doi":"10.1039/d4cp03878a","DOIUrl":"https://doi.org/10.1039/d4cp03878a","url":null,"abstract":"Deep eutectic solvents (DESs) have emerged as solubilizing media of intense interest due partly to their easily tailorable physicochemical properties. Extensive H-bonding between the constituents in a two-constituent system is the major driving force for the formation of the DES. Addition of ethanolamine (ETA), a compound having H-bonding capabilities, to the DESs composed of a terpene [menthol (Men) or thymol (Thy)] and a fatty acid [n-decanoic acid (DA)] results in unprecedented increase in dynamic viscosity due to the extensive rearrangement in the H-bonding network and other interactions within the system while the liquid mixture still behaves as a Newtonian fluid. For the non-DA DES constituted of Men and Thy this behavior is not observed. Visual color appearance, density and electrical conductivity measurements, UV-Vis and FTIR absorbance, differential scanning calorimetry, and empirical Kamlet-Taft parameters of the ETA-added DA-based DESs reveal the microstructural changes effectively. Cybotactic regions of the fluorescence microfluidity probes [1,3-bis(1-pyrenyl)propane - an intramolecular excimer forming probe as well as perylene and 1,6-diphenylhexatriene - well-established anisotropy probes] also manifest the unprecedented increase in the viscosity of the DA-based DES system upon ETA addition. The carboxylic acid functionality of the DA plays a crucial role in bringing microstructural changes within the system as ETA is added. Physicochemical properties of DES systems can be effectively manipulated by not only changing the constituents and their compositions, but also by judicious addition of a co-solute/co-solvent. The work offers easy and efficient way to favorably tailor the properties of interest of these environmentally-benign media.","PeriodicalId":99,"journal":{"name":"Physical Chemistry Chemical Physics","volume":"76 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142968507","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}
Sebastian Speer, Sven Jovanovic, Alexandre Merlen, Francesco Bartoli, Kiran Kiran, Niklas Lennart Wolf, Andre Karl, Eva Jodat, Rüdiger-A Eichel
The study of degradation behavior for electrocatalysts in an industrial context calls for rapid and efficient analysis methods. Optical methods like Raman spectroscopy fulfil these requirements and are thus predestined for this purpose. However, the iridium utilized in proton exchange membrane electrolysis (PEMEL) is Raman inactive in its metallic state. This work demonstrates the high oxidation sensitivity of iridium and its utilization in analysis of catalyst materials. Laser induced oxidation Raman spectroscopy (LIORS) is established as a novel method for qualitative, chemical and structural analysis of iridium catalysts. Differences in particle sizes of iridium powders drastically change oxidation sensitivity. Oxidation of the iridium powders to IrO2 occurred at a laser power density of 0.47 ± 0.06 mWμm-2 for the 850 μm powder and at 0.12 ± 0.06 mWμm-2 and 0.019 ± 0.015 mWμm-2 for the 50 μm and 0.7-0.9 μm powders respectively. LIORS was utilized to assess possible deterioration of an iridium electrocatalyst due to operation in electrolysis. The operated electrocatalyst exhibited higher oxidation sensitivity, suggesting smaller iridium particle size due to catalyst dissolution. Peak shifts of the IrO2 signal were utilized to assess differences in transformation temperatures. The operated electrocatalyst showed transformation to IrO2 at lower temperature (8 cm-1 redshift) relative to the pristine catalyst (10 cm-1 redshift), demonstrating that pre-oxidation of the iridium to amorphous IrOx during electrolysis diminishes the energy barrier needed for IrO2 formation. Thus, LIORS can be utilized as a straightforward screening method for the analysis of iridium electrocatalysts in the industrial application of PEMEL.
{"title":"Laser induced oxidation Raman spectroscopy as analysis tool for iridium-based oxygen evolution catalysts","authors":"Sebastian Speer, Sven Jovanovic, Alexandre Merlen, Francesco Bartoli, Kiran Kiran, Niklas Lennart Wolf, Andre Karl, Eva Jodat, Rüdiger-A Eichel","doi":"10.1039/d4cp03592e","DOIUrl":"https://doi.org/10.1039/d4cp03592e","url":null,"abstract":"The study of degradation behavior for electrocatalysts in an industrial context calls for rapid and efficient analysis methods. Optical methods like Raman spectroscopy fulfil these requirements and are thus predestined for this purpose. However, the iridium utilized in proton exchange membrane electrolysis (PEMEL) is Raman inactive in its metallic state. This work demonstrates the high oxidation sensitivity of iridium and its utilization in analysis of catalyst materials. Laser induced oxidation Raman spectroscopy (LIORS) is established as a novel method for qualitative, chemical and structural analysis of iridium catalysts. Differences in particle sizes of iridium powders drastically change oxidation sensitivity. Oxidation of the iridium powders to IrO<small><sub>2</sub></small> occurred at a laser power density of 0.47 ± 0.06 mWμm<small><sup>-2</sup></small> for the 850 μm powder and at 0.12 ± 0.06 mWμm<small><sup>-2</sup></small> and 0.019 ± 0.015 mWμm<small><sup>-2</sup></small> for the 50 μm and 0.7-0.9 μm powders respectively. LIORS was utilized to assess possible deterioration of an iridium electrocatalyst due to operation in electrolysis. The operated electrocatalyst exhibited higher oxidation sensitivity, suggesting smaller iridium particle size due to catalyst dissolution. Peak shifts of the IrO<small><sub>2</sub></small> signal were utilized to assess differences in transformation temperatures. The operated electrocatalyst showed transformation to IrO<small><sub>2</sub></small> at lower temperature (8 cm<small><sup>-1</sup></small> redshift) relative to the pristine catalyst (10 cm<small><sup>-1</sup></small> redshift), demonstrating that pre-oxidation of the iridium to amorphous IrO<small><sub>x</sub></small> during electrolysis diminishes the energy barrier needed for IrO<small><sub>2</sub></small> formation. Thus, LIORS can be utilized as a straightforward screening method for the analysis of iridium electrocatalysts in the industrial application of PEMEL.","PeriodicalId":99,"journal":{"name":"Physical Chemistry Chemical Physics","volume":"1 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142968510","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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