The development of photocatalysts to drive organic reactions is a frontier research topic. Organic polymers can be well tuned in terms of structural and photophysical properties and, therefore, constitute a promising class of photocatalysts in photoredox catalysis for organic synthesis. In this review article, we provide an overview of the concept of photoredox catalysis and recent developments in organic polymers as photocatalysts including porous organic polymers, graphitic carbon nitride, carbon dots, and polymer dots with adjustable reactivity that have undergone state-of-the-art advancement in different photoredox catalytic organic reactions.
{"title":"Visible-light photoredox catalysis with organic polymers","authors":"G. Kumar, B. Cai, S. Ott, H. Tian","doi":"10.1063/5.0123282","DOIUrl":"https://doi.org/10.1063/5.0123282","url":null,"abstract":"The development of photocatalysts to drive organic reactions is a frontier research topic. Organic polymers can be well tuned in terms of structural and photophysical properties and, therefore, constitute a promising class of photocatalysts in photoredox catalysis for organic synthesis. In this review article, we provide an overview of the concept of photoredox catalysis and recent developments in organic polymers as photocatalysts including porous organic polymers, graphitic carbon nitride, carbon dots, and polymer dots with adjustable reactivity that have undergone state-of-the-art advancement in different photoredox catalytic organic reactions.","PeriodicalId":72559,"journal":{"name":"Chemical physics reviews","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42525864","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Metal-organic frameworks (MOFs) are a class of crystalline porous coordination materials, which are assembled from inorganic nodes and organic linkers. Numerous applications, such as gas storage, molecule separation, catalysis, optical sensing, and charge transport, benefit from the outstanding properties of MOF materials. More advanced applications, e.g., in the electronics and optoelectronics area, demand homogeneous and monolithic MOF thin films. Recent studies demonstrated that surface-mounted MOFs (SURMOFs) are well suited to fulfill the requirements for the integration of MOFs into devices. As a crystalline thin-film material with tunable thickness, SURMOFs have been widely used in the optimization of chromophore stacking, electrical transport, stimuli-response, etc. The fabrication of SURMOFs is carried out employing a layer-by-layer (LbL) assembly technique, and it can yield MOF thin films with a well-defined orientation, tunable thickness, and editable crystalline heterostructure. We summarize the LbL assembly methods for SURMOF fabrication and the realization of advanced SURMOF architectures, including optical and electronic applications as well as the integration of photoactive SURMOFs and SURMOF-derived materials in technical devices. We conclude with a discussion of the challenges and prediction of the future of SURMOF materials.
{"title":"Layer-by-layer assembly of metal-organic framework thin films: Fabrication and advanced applications","authors":"Dong-Hui Chen, H. Gliemann, C. Wöll","doi":"10.1063/5.0135019","DOIUrl":"https://doi.org/10.1063/5.0135019","url":null,"abstract":"Metal-organic frameworks (MOFs) are a class of crystalline porous coordination materials, which are assembled from inorganic nodes and organic linkers. Numerous applications, such as gas storage, molecule separation, catalysis, optical sensing, and charge transport, benefit from the outstanding properties of MOF materials. More advanced applications, e.g., in the electronics and optoelectronics area, demand homogeneous and monolithic MOF thin films. Recent studies demonstrated that surface-mounted MOFs (SURMOFs) are well suited to fulfill the requirements for the integration of MOFs into devices. As a crystalline thin-film material with tunable thickness, SURMOFs have been widely used in the optimization of chromophore stacking, electrical transport, stimuli-response, etc. The fabrication of SURMOFs is carried out employing a layer-by-layer (LbL) assembly technique, and it can yield MOF thin films with a well-defined orientation, tunable thickness, and editable crystalline heterostructure. We summarize the LbL assembly methods for SURMOF fabrication and the realization of advanced SURMOF architectures, including optical and electronic applications as well as the integration of photoactive SURMOFs and SURMOF-derived materials in technical devices. We conclude with a discussion of the challenges and prediction of the future of SURMOF materials.","PeriodicalId":72559,"journal":{"name":"Chemical physics reviews","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44149619","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A single metal site incorporated in N-doped carbon (M/N/C) is a promising electrocatalyst. Here, we perform a computation investigation of the effect of electrolyte anion adsorption on the activity and stability of single-atom catalysts (MN4) with M as transition metal and p-block metal. The MN4 site on two different graphene structures (bulk graphene and graphene edge) is studied under electrochemical conditions for the oxygen reduction reaction (ORR) and the CO2 reduction reaction (CO2RR). Because of the two-dimensional nature of the catalyst, reaction intermediates and electrolyte ions can interact with both sides of the single-atom catalyst. As a result, the electrolyte anions compete with water and adsorbate on the single metal site, in some cases either poisoning or modifying the catalyst activity and thermodynamic stability. We find most electrolyte anions adsorbs on the single metal site under ORR conditions but not at the lower potentials for the CO2RR. Still, the adsorption of water and gas molecules can occur under CO2RR conditions. For example, under ORR conditions, the thermodynamic driving force of the *SO4-FeN4 site in the 0.1 M H2SO4 solution is about 0.47–0.56 eV lower than the *O-FeN4 site in water, depending on the local carbon structure. Additionally, the stabilization by electrolyte anions depends on the nature of the metal atom. Our study demonstrates the important role of electrolytes and the coordination environment for the activity and stability of the M/N/C catalyst.
N掺杂碳（M/N/C）中的单一金属位点是一种很有前途的电催化剂。在此，我们对电解质阴离子吸附对以M为过渡金属和p嵌段金属的单原子催化剂（MN4）的活性和稳定性的影响进行了计算研究。在氧还原反应（ORR）和CO2还原反应（CO2RR）的电化学条件下，研究了两种不同石墨烯结构（体石墨烯和石墨烯边缘）上的MN4位点。由于催化剂的二维性质，反应中间体和电解质离子可以与单原子催化剂的两侧相互作用。结果，电解质阴离子与水竞争，并在单个金属位点上吸附，在某些情况下毒害或改变催化剂活性和热力学稳定性。我们发现，在ORR条件下，大多数电解质阴离子吸附在单个金属位点上，但在CO2RR的较低电势下没有。尽管如此，水和气体分子的吸附可以在CO2RR条件下发生。例如，在ORR条件下，0.1 M H2SO4溶液中*SO4-FeN4位点的热力学驱动力约为0.47–0.56 eV低于水中的*O-FeN4位点。此外，电解质阴离子的稳定性取决于金属原子的性质。我们的研究证明了电解质和配位环境对M/N/C催化剂的活性和稳定性的重要作用。
{"title":"Effects of electrolyte anion adsorption on the activity and stability of single atom electrocatalysts","authors":"Tipaporn Patniboon, H. Hansen","doi":"10.1063/5.0125654","DOIUrl":"https://doi.org/10.1063/5.0125654","url":null,"abstract":"A single metal site incorporated in N-doped carbon (M/N/C) is a promising electrocatalyst. Here, we perform a computation investigation of the effect of electrolyte anion adsorption on the activity and stability of single-atom catalysts (MN4) with M as transition metal and p-block metal. The MN4 site on two different graphene structures (bulk graphene and graphene edge) is studied under electrochemical conditions for the oxygen reduction reaction (ORR) and the CO2 reduction reaction (CO2RR). Because of the two-dimensional nature of the catalyst, reaction intermediates and electrolyte ions can interact with both sides of the single-atom catalyst. As a result, the electrolyte anions compete with water and adsorbate on the single metal site, in some cases either poisoning or modifying the catalyst activity and thermodynamic stability. We find most electrolyte anions adsorbs on the single metal site under ORR conditions but not at the lower potentials for the CO2RR. Still, the adsorption of water and gas molecules can occur under CO2RR conditions. For example, under ORR conditions, the thermodynamic driving force of the *SO4-FeN4 site in the 0.1 M H2SO4 solution is about 0.47–0.56 eV lower than the *O-FeN4 site in water, depending on the local carbon structure. Additionally, the stabilization by electrolyte anions depends on the nature of the metal atom. Our study demonstrates the important role of electrolytes and the coordination environment for the activity and stability of the M/N/C catalyst.","PeriodicalId":72559,"journal":{"name":"Chemical physics reviews","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48658820","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The explosive growth of single-molecule techniques is transforming our understanding of biology, helping to develop new physics inspired by emergent biological processes, and leading to emerging areas of nanotechnology. Key biological and chemical processes can now be probed with new levels of detail, one molecule at a time, from the nanoscopic dynamics of nature's molecular machines to an ever-expanding range of exciting applications across multiple length and time scales. Their common feature is an ability to render the underlying distribution of molecular properties that ensemble averaging masks and to reveal new insights into complex systems containing spatial and temporal heterogeneity. Small fluorescent probes are among the most adaptable and versatile for single-molecule sensing applications because they provide high signal-to-noise ratios combined with excellent specificity of labeling when chemically attached to target biomolecules or embedded within a host material. In this review, we examine recent advances in probe designs, their utility, and applications and provide a practical guide to their use, focusing on the single-molecule detection of nucleic acids, proteins, carbohydrates, and membrane dynamics. We also present key challenges that must be overcome to perform successful single-molecule experiments, including probe conjugation strategies, identify tradeoffs and limitations for each probe design, showcase emerging applications, and discuss exciting future directions for the community.
{"title":"A guide to small fluorescent probes for single-molecule biophysics","authors":"M. Leake, S. Quinn","doi":"10.1063/5.0131663","DOIUrl":"https://doi.org/10.1063/5.0131663","url":null,"abstract":"The explosive growth of single-molecule techniques is transforming our understanding of biology, helping to develop new physics inspired by emergent biological processes, and leading to emerging areas of nanotechnology. Key biological and chemical processes can now be probed with new levels of detail, one molecule at a time, from the nanoscopic dynamics of nature's molecular machines to an ever-expanding range of exciting applications across multiple length and time scales. Their common feature is an ability to render the underlying distribution of molecular properties that ensemble averaging masks and to reveal new insights into complex systems containing spatial and temporal heterogeneity. Small fluorescent probes are among the most adaptable and versatile for single-molecule sensing applications because they provide high signal-to-noise ratios combined with excellent specificity of labeling when chemically attached to target biomolecules or embedded within a host material. In this review, we examine recent advances in probe designs, their utility, and applications and provide a practical guide to their use, focusing on the single-molecule detection of nucleic acids, proteins, carbohydrates, and membrane dynamics. We also present key challenges that must be overcome to perform successful single-molecule experiments, including probe conjugation strategies, identify tradeoffs and limitations for each probe design, showcase emerging applications, and discuss exciting future directions for the community.","PeriodicalId":72559,"journal":{"name":"Chemical physics reviews","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44194670","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Etienne Palos, Saswata Dasgupta, Eleftherios Lambros, F. Paesani
Density functional theory (DFT) has been applied to modeling molecular interactions in water for over three decades. The ubiquity of water in chemical and biological processes demands a unified understanding of its physics, from the single molecule to the thermodynamic limit and everything in between. Recent advances in the development of data-driven and machine-learning potentials have accelerated simulation of water and aqueous systems with DFT accuracy. However, anomalous properties of water in the condensed phase, where a rigorous treatment of both local and non-local many-body (MB) interactions is in order, are often unsatisfactory or partially missing in DFT models of water. In this review, we discuss the modeling of water and aqueous systems based on DFT and provide a comprehensive description of a general theoretical/computational framework for the development of data-driven many-body potentials from DFT reference data. This framework, coined MB-DFT, readily enables efficient many-body molecular dynamics (MD) simulations of small molecules, in both gas and condensed phases, while preserving the accuracy of the underlying DFT model. Theoretical considerations are emphasized, including the role that the delocalization error plays in MB-DFT potentials of water and the possibility to elevate DFT and MB-DFT to near-chemical-accuracy through a density-corrected formalism. The development of the MB-DFT framework is described in detail, along with its application in MB-MD simulations and recent extension to the modeling of reactive processes in solution within a quantum mechanics/MB molecular mechanics (QM/MB-MM) scheme, using water as a prototypical solvent. Finally, we identify open challenges and discuss future directions for MB-DFT and QM/MB-MM simulations in condensed phases.
{"title":"Data-driven many-body potentials from density functional theory for aqueous phase chemistry","authors":"Etienne Palos, Saswata Dasgupta, Eleftherios Lambros, F. Paesani","doi":"10.1063/5.0129613","DOIUrl":"https://doi.org/10.1063/5.0129613","url":null,"abstract":"Density functional theory (DFT) has been applied to modeling molecular interactions in water for over three decades. The ubiquity of water in chemical and biological processes demands a unified understanding of its physics, from the single molecule to the thermodynamic limit and everything in between. Recent advances in the development of data-driven and machine-learning potentials have accelerated simulation of water and aqueous systems with DFT accuracy. However, anomalous properties of water in the condensed phase, where a rigorous treatment of both local and non-local many-body (MB) interactions is in order, are often unsatisfactory or partially missing in DFT models of water. In this review, we discuss the modeling of water and aqueous systems based on DFT and provide a comprehensive description of a general theoretical/computational framework for the development of data-driven many-body potentials from DFT reference data. This framework, coined MB-DFT, readily enables efficient many-body molecular dynamics (MD) simulations of small molecules, in both gas and condensed phases, while preserving the accuracy of the underlying DFT model. Theoretical considerations are emphasized, including the role that the delocalization error plays in MB-DFT potentials of water and the possibility to elevate DFT and MB-DFT to near-chemical-accuracy through a density-corrected formalism. The development of the MB-DFT framework is described in detail, along with its application in MB-MD simulations and recent extension to the modeling of reactive processes in solution within a quantum mechanics/MB molecular mechanics (QM/MB-MM) scheme, using water as a prototypical solvent. Finally, we identify open challenges and discuss future directions for MB-DFT and QM/MB-MM simulations in condensed phases.","PeriodicalId":72559,"journal":{"name":"Chemical physics reviews","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44964396","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
D. Zigmantas, T. Polívka, P. Persson, V. Sundström
The invention of the laser in 1960 gave us the ruby laser, which generally produced chaotic pulses of light. Six years later, in 1966, a concept called passive mode-locking applied to neodymium-glass lasers produced reasonably well-behaving picosecond pulses. This triggered an intense activity, with respect to developing improved laser pulse sources, measurement techniques, and application to chemistry, physics, and biology. Initially, only ∼10 –ps-long pulses at a few wavelengths were available. Nevertheless, insight into the function of complex biological systems, like photosynthetic proteins, and molecules of chemical interest was gained in very early studies. Today, both duration and color of ultrashort pulses can be tuned to almost any value. This has of course opened up possibilities to study almost any atomic, molecular, or solid-state system and any dynamic process. This review focuses on the use of laser spectroscopy to investigate light energy conversion mechanisms in both natural photosynthesis and a topical selection of novel materials for solar energy conversion. More specifically, in photosynthesis we will review light harvesting and primary electron transfer; materials for solar energy conversion that we discuss include sensitized semiconductors (dye sensitized solar cells), polymer:fullerene and polymer:polymer bulk heterojunctions (organic solar cells), organometal halide perovskites, as well as molecular and hybrid systems for production of solar fuel and valuable chemicals. All these scientific areas, and in particular photosynthesis and the solar cell materials, have been extensively studied with ultrafast spectroscopy, resulting in a vast literature; a comprehensive review of the individual materials is, therefore, not feasible, and we will limit our discussion to work that we think has been of particular importance for understanding the function of the respective systems.
{"title":"Ultrafast laser spectroscopy uncovers mechanisms of light energy conversion in photosynthesis and sustainable energy materials","authors":"D. Zigmantas, T. Polívka, P. Persson, V. Sundström","doi":"10.1063/5.0092864","DOIUrl":"https://doi.org/10.1063/5.0092864","url":null,"abstract":"The invention of the laser in 1960 gave us the ruby laser, which generally produced chaotic pulses of light. Six years later, in 1966, a concept called passive mode-locking applied to neodymium-glass lasers produced reasonably well-behaving picosecond pulses. This triggered an intense activity, with respect to developing improved laser pulse sources, measurement techniques, and application to chemistry, physics, and biology. Initially, only ∼10 –ps-long pulses at a few wavelengths were available. Nevertheless, insight into the function of complex biological systems, like photosynthetic proteins, and molecules of chemical interest was gained in very early studies. Today, both duration and color of ultrashort pulses can be tuned to almost any value. This has of course opened up possibilities to study almost any atomic, molecular, or solid-state system and any dynamic process. This review focuses on the use of laser spectroscopy to investigate light energy conversion mechanisms in both natural photosynthesis and a topical selection of novel materials for solar energy conversion. More specifically, in photosynthesis we will review light harvesting and primary electron transfer; materials for solar energy conversion that we discuss include sensitized semiconductors (dye sensitized solar cells), polymer:fullerene and polymer:polymer bulk heterojunctions (organic solar cells), organometal halide perovskites, as well as molecular and hybrid systems for production of solar fuel and valuable chemicals. All these scientific areas, and in particular photosynthesis and the solar cell materials, have been extensively studied with ultrafast spectroscopy, resulting in a vast literature; a comprehensive review of the individual materials is, therefore, not feasible, and we will limit our discussion to work that we think has been of particular importance for understanding the function of the respective systems.","PeriodicalId":72559,"journal":{"name":"Chemical physics reviews","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44228421","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-12-01Epub Date: 2022-12-14DOI: 10.1063/5.0120888
Eleanor F Page, Marea J Blake, Grant A Foley, Tessa R Calhoun
Nature's seemingly controlled chaos in heterogeneous two-dimensional cell membranes stands in stark contrast to the precise, often homogeneous, environment in an experimentalist's flask or carefully designed material system. Yet cell membranes can play a direct role, or serve as inspiration, in all fields of biology, chemistry, physics, and engineering. Our understanding of these ubiquitous structures continues to evolve despite over a century of study largely driven by the application of new technologies. Here, we review the insight afforded by second harmonic generation (SHG), a nonlinear optical technique. From potential measurements to adsorption and diffusion on both model and living systems, SHG complements existing techniques while presenting a large exploratory space for new discoveries.
{"title":"Monitoring membranes: The exploration of biological bilayers with second harmonic generation.","authors":"Eleanor F Page, Marea J Blake, Grant A Foley, Tessa R Calhoun","doi":"10.1063/5.0120888","DOIUrl":"10.1063/5.0120888","url":null,"abstract":"<p><p>Nature's seemingly controlled chaos in heterogeneous two-dimensional cell membranes stands in stark contrast to the precise, often homogeneous, environment in an experimentalist's flask or carefully designed material system. Yet cell membranes can play a direct role, or serve as inspiration, in all fields of biology, chemistry, physics, and engineering. Our understanding of these ubiquitous structures continues to evolve despite over a century of study largely driven by the application of new technologies. Here, we review the insight afforded by second harmonic generation (SHG), a nonlinear optical technique. From potential measurements to adsorption and diffusion on both model and living systems, SHG complements existing techniques while presenting a large exploratory space for new discoveries.</p>","PeriodicalId":72559,"journal":{"name":"Chemical physics reviews","volume":"3 4","pages":"041307"},"PeriodicalIF":6.1,"publicationDate":"2022-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9756348/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"10767694","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Many chemical and physical systems show self-sustained oscillations that can be described by a set of nonlinear differential equations. The system enters oscillatory behavior by an intrinsic instability that leads to bifurcation. We analyze conducting systems that present oscillating response under application of external voltage or current. Phenomena like electrochemical corrosion and the spiking response of a biological neuron are well-known examples. These systems have applications in artificial neurons and synapses for neuromorphic computation. Their dynamical properties can be characterized by normal mode analysis of small expansion of the constituent nonlinear equations. The linearized model leads to the technique of ac frequency response impedance spectroscopy that can be obtained experimentally. We show a general description of two-variable systems formed by a combination of a fast variable (the voltage) and a slowing down internal variable, which produce a chemical inductor. A classification of bifurcations and stability is obtained in terms of the parameters of the intrinsic equivalent circuit including the case of a negative inductor. Thereafter, we describe a number of physical examples and establish the characterization of their properties: The electrocatalytic reaction with adsorbed intermediate species, an oscillating metal oxide memristor, and finally we discuss the signs of the equivalent circuit elements in the central model of neuroscience, the Hodgkin–Huxley model for an oscillating neuron.
{"title":"Negative inductor effects in nonlinear two-dimensional systems: Oscillatory neurons and memristors","authors":"J. Bisquert","doi":"10.1063/5.0124115","DOIUrl":"https://doi.org/10.1063/5.0124115","url":null,"abstract":"Many chemical and physical systems show self-sustained oscillations that can be described by a set of nonlinear differential equations. The system enters oscillatory behavior by an intrinsic instability that leads to bifurcation. We analyze conducting systems that present oscillating response under application of external voltage or current. Phenomena like electrochemical corrosion and the spiking response of a biological neuron are well-known examples. These systems have applications in artificial neurons and synapses for neuromorphic computation. Their dynamical properties can be characterized by normal mode analysis of small expansion of the constituent nonlinear equations. The linearized model leads to the technique of ac frequency response impedance spectroscopy that can be obtained experimentally. We show a general description of two-variable systems formed by a combination of a fast variable (the voltage) and a slowing down internal variable, which produce a chemical inductor. A classification of bifurcations and stability is obtained in terms of the parameters of the intrinsic equivalent circuit including the case of a negative inductor. Thereafter, we describe a number of physical examples and establish the characterization of their properties: The electrocatalytic reaction with adsorbed intermediate species, an oscillating metal oxide memristor, and finally we discuss the signs of the equivalent circuit elements in the central model of neuroscience, the Hodgkin–Huxley model for an oscillating neuron.","PeriodicalId":72559,"journal":{"name":"Chemical physics reviews","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46411227","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In the last 15 years, the attention dedicated to organic conjugated systems experienced outstanding growth because of the renewed interest in mechanisms involving triplet states such as singlet fission, thermally activated delayed fluorescence, and intersystem crossing enhanced phosphorescence. Photon upconversion via sensitized triplet–triplet annihilation ( sTTA) enables the conversion of low-energy photons into high-energy ones, and it has been proposed in multicomponent systems as an efficient managing strategy of non-coherent photons. This mechanism exploits the annihilation of two optically dark triplet states of emitter moieties to produce high-energy photons. The annihilating triplets are sensitized through Dexter energy transfer by a light-harvester, typically a conjugated molecule or a nanocrystal, so sTTA upconversion is usually performed in bi-component systems. The high yield observed at low excitation intensities stimulated thriving research in the field, leading to the development of a large family of fully organic and hybrid sTTA multicomponent upconverters. Here, we compare the evolution of these two families of systems with respect to the sTTA upconversion main figures of merit, highlighting the strengths and weaknesses of both approaches, according to the results reported in the literature. The data presented are also discussed in the perspective of future developments in the field, pointing out the challenges that are still to be faced for the technological use of the sTTA upconversion process.
{"title":"Sensitized triplet–triplet annihilation based photon upconversion in full organic and hybrid multicomponent systems","authors":"A. Ronchi, A. Monguzzi","doi":"10.1063/5.0112032","DOIUrl":"https://doi.org/10.1063/5.0112032","url":null,"abstract":"In the last 15 years, the attention dedicated to organic conjugated systems experienced outstanding growth because of the renewed interest in mechanisms involving triplet states such as singlet fission, thermally activated delayed fluorescence, and intersystem crossing enhanced phosphorescence. Photon upconversion via sensitized triplet–triplet annihilation ( sTTA) enables the conversion of low-energy photons into high-energy ones, and it has been proposed in multicomponent systems as an efficient managing strategy of non-coherent photons. This mechanism exploits the annihilation of two optically dark triplet states of emitter moieties to produce high-energy photons. The annihilating triplets are sensitized through Dexter energy transfer by a light-harvester, typically a conjugated molecule or a nanocrystal, so sTTA upconversion is usually performed in bi-component systems. The high yield observed at low excitation intensities stimulated thriving research in the field, leading to the development of a large family of fully organic and hybrid sTTA multicomponent upconverters. Here, we compare the evolution of these two families of systems with respect to the sTTA upconversion main figures of merit, highlighting the strengths and weaknesses of both approaches, according to the results reported in the literature. The data presented are also discussed in the perspective of future developments in the field, pointing out the challenges that are still to be faced for the technological use of the sTTA upconversion process.","PeriodicalId":72559,"journal":{"name":"Chemical physics reviews","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47547216","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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