E. Alsaç, Nataraju Bodappa, Alexander W. H. Whittingham, Yutong Liu, Adriana C. de Lazzari, Rodney D. L. Smith
Heterogeneous electrocatalytic reactions are believed to occur at a minority of coordination sites through a series of elementary reactions that are balanced by minor equilibria. These features mask changes in reaction sites, making it challenging to directly identify and analyze reaction sites or intermediates while studying reaction mechanisms. Systematic perturbations of a reaction system often yield systematic changes in material properties and behavior. Correlations between measurable changes in parameters describing the structure and behavior, therefore, serve as powerful tools for distinguishing active reaction sites. This review explores structure–property correlations that have advanced understanding of behavior and reaction mechanisms in heterogeneous electrocatalysis. It covers correlations that have advanced understanding of the contributions of the local reaction environment to reactivity, of structure and bonding within solid-state materials, of geometric or mechanical strain in bonding environments, and of the impact of structural defects. Such correlations can assist researchers in developing next generation catalysts by establishing catalyst design principles and gaining control over reaction mechanisms.
{"title":"Structure–property correlations for analysis of heterogeneous electrocatalysts","authors":"E. Alsaç, Nataraju Bodappa, Alexander W. H. Whittingham, Yutong Liu, Adriana C. de Lazzari, Rodney D. L. Smith","doi":"10.1063/5.0058704","DOIUrl":"https://doi.org/10.1063/5.0058704","url":null,"abstract":"Heterogeneous electrocatalytic reactions are believed to occur at a minority of coordination sites through a series of elementary reactions that are balanced by minor equilibria. These features mask changes in reaction sites, making it challenging to directly identify and analyze reaction sites or intermediates while studying reaction mechanisms. Systematic perturbations of a reaction system often yield systematic changes in material properties and behavior. Correlations between measurable changes in parameters describing the structure and behavior, therefore, serve as powerful tools for distinguishing active reaction sites. This review explores structure–property correlations that have advanced understanding of behavior and reaction mechanisms in heterogeneous electrocatalysis. It covers correlations that have advanced understanding of the contributions of the local reaction environment to reactivity, of structure and bonding within solid-state materials, of geometric or mechanical strain in bonding environments, and of the impact of structural defects. Such correlations can assist researchers in developing next generation catalysts by establishing catalyst design principles and gaining control over reaction mechanisms.","PeriodicalId":72559,"journal":{"name":"Chemical physics reviews","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42906765","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}
{"title":"The chemical landscape of Chemical Physics Reviews","authors":"F. Castellano","doi":"10.1063/5.0059231","DOIUrl":"https://doi.org/10.1063/5.0059231","url":null,"abstract":"","PeriodicalId":72559,"journal":{"name":"Chemical physics reviews","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-06-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1063/5.0059231","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49580498","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}
This review focuses on molecular ensemble junctions in which the individual molecules of a monolayer each span two electrodes. This geometry favors quantum mechanical tunneling as the dominant mechanism of charge transport, which translates perturbances on the scale of bond lengths into nonlinear electrical responses. The ability to affect these responses at low voltages and with a variety of inputs, such as de/protonation, photon absorption, isomerization, oxidation/reduction, etc., creates the possibility to fabricate molecule-scale electronic devices that augment; extend; and, in some cases, outperform conventional semiconductor-based electronics. Moreover, these molecular devices, in part, fabricate themselves by defining single-nanometer features with atomic precision via self-assembly. Although these junctions share many properties with single-molecule junctions, they also possess unique properties that present a different set of problems and exhibit unique properties. The primary trade-off of ensemble junctions is complexity for functionality; disordered molecular ensembles are significantly more difficult to model, particularly atomistically, but they are static and can be incorporated into integrated circuits. Progress toward useful functionality has accelerated in recent years, concomitant with deeper scientific insight into the mediation of charge transport by ensembles of molecules and experimental platforms that enable empirical studies to control for defects and artifacts. This review separates junctions by the trade-offs, complexity, and sensitivity of their constituents; the bottom electrode to which the ensembles are anchored and the nature of the anchoring chemistry both chemically and with respect to electronic coupling; the molecular layer and the relationship among electronic structure, mechanism of charge transport, and electrical output; and the top electrode that realizes an individual junction by defining its geometry and a second molecule–electrode interface. Due to growing interest in and accessibility of this interdisciplinary field, there is now sufficient variety in each of these parts to be able to treat them separately. When viewed this way, clear structure–function relationships emerge that can serve as design rules for extracting useful functionality.
{"title":"Charge transport through molecular ensembles: Recent progress in molecular electronics","authors":"Yuru Liu, Xinkai Qiu, Saurabh Soni, R. Chiechi","doi":"10.1063/5.0050667","DOIUrl":"https://doi.org/10.1063/5.0050667","url":null,"abstract":"This review focuses on molecular ensemble junctions in which the individual molecules of a monolayer each span two electrodes. This geometry favors quantum mechanical tunneling as the dominant mechanism of charge transport, which translates perturbances on the scale of bond lengths into nonlinear electrical responses. The ability to affect these responses at low voltages and with a variety of inputs, such as de/protonation, photon absorption, isomerization, oxidation/reduction, etc., creates the possibility to fabricate molecule-scale electronic devices that augment; extend; and, in some cases, outperform conventional semiconductor-based electronics. Moreover, these molecular devices, in part, fabricate themselves by defining single-nanometer features with atomic precision via self-assembly. Although these junctions share many properties with single-molecule junctions, they also possess unique properties that present a different set of problems and exhibit unique properties. The primary trade-off of ensemble junctions is complexity for functionality; disordered molecular ensembles are significantly more difficult to model, particularly atomistically, but they are static and can be incorporated into integrated circuits. Progress toward useful functionality has accelerated in recent years, concomitant with deeper scientific insight into the mediation of charge transport by ensembles of molecules and experimental platforms that enable empirical studies to control for defects and artifacts. This review separates junctions by the trade-offs, complexity, and sensitivity of their constituents; the bottom electrode to which the ensembles are anchored and the nature of the anchoring chemistry both chemically and with respect to electronic coupling; the molecular layer and the relationship among electronic structure, mechanism of charge transport, and electrical output; and the top electrode that realizes an individual junction by defining its geometry and a second molecule–electrode interface. Due to growing interest in and accessibility of this interdisciplinary field, there is now sufficient variety in each of these parts to be able to treat them separately. When viewed this way, clear structure–function relationships emerge that can serve as design rules for extracting useful functionality.","PeriodicalId":72559,"journal":{"name":"Chemical physics reviews","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1063/5.0050667","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42541078","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}
Austin D C Miller, Harun F Ozbakir, Arnab Mukherjee
Calcium ions represent one of the key second messengers accompanying neural activity and synaptic signaling. Accordingly, dynamic imaging of calcium fluctuations in living organisms represents a cornerstone technology for discovering neural mechanisms that underlie memory, determine behavior, and modulate emotional states as well as how these mechanisms are perturbed by neurological disease and brain injury. While optical technologies are well established for high resolution imaging of calcium dynamics, physical limits on light penetration hinder their application for whole-brain imaging in intact vertebrates. Unlike optics, magnetic resonance imaging (MRI) enables noninvasive large-scale imaging across vertebrates of all sizes. This has motivated the development of several sensors that leverage innovative physicochemical mechanisms to sensitize MRI contrast to intracellular and extracellular changes in calcium. Here, we review the current state-of-the-art in MRI-based calcium sensors, focusing on fundamental aspects of sensor performance, in vivo applications, and challenges related to sensitivity. We also highlight how innovations at the intersection of reporter gene technology and gene delivery open potential opportunities for mapping calcium activity in genetically targeted cells, complementing the benefits of small molecule probes and nanoparticle sensors.
{"title":"Calcium-responsive contrast agents for functional magnetic resonance imaging.","authors":"Austin D C Miller, Harun F Ozbakir, Arnab Mukherjee","doi":"10.1063/5.0041394","DOIUrl":"https://doi.org/10.1063/5.0041394","url":null,"abstract":"<p><p>Calcium ions represent one of the key second messengers accompanying neural activity and synaptic signaling. Accordingly, dynamic imaging of calcium fluctuations in living organisms represents a cornerstone technology for discovering neural mechanisms that underlie memory, determine behavior, and modulate emotional states as well as how these mechanisms are perturbed by neurological disease and brain injury. While optical technologies are well established for high resolution imaging of calcium dynamics, physical limits on light penetration hinder their application for whole-brain imaging in intact vertebrates. Unlike optics, magnetic resonance imaging (MRI) enables noninvasive large-scale imaging across vertebrates of all sizes. This has motivated the development of several sensors that leverage innovative physicochemical mechanisms to sensitize MRI contrast to intracellular and extracellular changes in calcium. Here, we review the current state-of-the-art in MRI-based calcium sensors, focusing on fundamental aspects of sensor performance, <i>in vivo</i> applications, and challenges related to sensitivity. We also highlight how innovations at the intersection of reporter gene technology and gene delivery open potential opportunities for mapping calcium activity in genetically targeted cells, complementing the benefits of small molecule probes and nanoparticle sensors.</p>","PeriodicalId":72559,"journal":{"name":"Chemical physics reviews","volume":"2 2","pages":"021301"},"PeriodicalIF":0.0,"publicationDate":"2021-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1063/5.0041394","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"39075924","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}
G. Paternó, A. Ross, S. Pietralunga, S. Normani, Nicholas Dalla Vedova, Jakkarin Limwongyut, Gaia Bondelli, L. Moscardi, G. Bazan, F. Scotognella, G. Lanzani
Silver, in the form of nanostructures, is widely employed as an antimicrobial agent. The origin of the biocidal mechanism has been elucidated in the last decades, originating from silver cation release due to oxidative dissolution followed by cellular uptake of silver ions, a process that causes a severe disruption of bacterial metabolism, leading to eradication. Despite the large body of work addressing the effects of nanosilver shape/size on the antibacterial mechanism and on the (bio)physical chemistry pathways that drive bacterial eradication, little effort has been devoted to the investigation of nanostructured silver plasmon response upon interaction with bacteria. We investigate the bacteria-induced changes of the plasmonic response of silver nanoplates after exposure to the bacterial model Escherichia coli. Ultrafast pump-probe measurements indicate that the dramatic changes on particle size/shape and crystallinity, which likely stem from a bacteria-induced oxidative dissolution process, translate into a clear modification of the plasmonic response. Specifically, exposure to bacteria causes a decrease in the electron–phonon coupling time and an increase in lattice-environment coupling time, effects explained by an increase in the free electron density and amorphization of the silver particles. Coherent oscillations that are observed in pristine silver are completely damped in contaminated samples, which can be attributed again to amorphization of the nanoplates at the surface and an increase in polydispersivity of particle geometries. This study opens innovative avenues in the biophysics of bio-responsive materials, with the aim of providing reliable biophysical signatures of the interaction of plasmonic materials with complex biological environments.
{"title":"The impact of bacteria exposure on the plasmonic response of silver nanostructured surfaces","authors":"G. Paternó, A. Ross, S. Pietralunga, S. Normani, Nicholas Dalla Vedova, Jakkarin Limwongyut, Gaia Bondelli, L. Moscardi, G. Bazan, F. Scotognella, G. Lanzani","doi":"10.1063/5.0042547","DOIUrl":"https://doi.org/10.1063/5.0042547","url":null,"abstract":"Silver, in the form of nanostructures, is widely employed as an antimicrobial agent. The origin of the biocidal mechanism has been elucidated in the last decades, originating from silver cation release due to oxidative dissolution followed by cellular uptake of silver ions, a process that causes a severe disruption of bacterial metabolism, leading to eradication. Despite the large body of work addressing the effects of nanosilver shape/size on the antibacterial mechanism and on the (bio)physical chemistry pathways that drive bacterial eradication, little effort has been devoted to the investigation of nanostructured silver plasmon response upon interaction with bacteria. We investigate the bacteria-induced changes of the plasmonic response of silver nanoplates after exposure to the bacterial model Escherichia coli. Ultrafast pump-probe measurements indicate that the dramatic changes on particle size/shape and crystallinity, which likely stem from a bacteria-induced oxidative dissolution process, translate into a clear modification of the plasmonic response. Specifically, exposure to bacteria causes a decrease in the electron–phonon coupling time and an increase in lattice-environment coupling time, effects explained by an increase in the free electron density and amorphization of the silver particles. Coherent oscillations that are observed in pristine silver are completely damped in contaminated samples, which can be attributed again to amorphization of the nanoplates at the surface and an increase in polydispersivity of particle geometries. This study opens innovative avenues in the biophysics of bio-responsive materials, with the aim of providing reliable biophysical signatures of the interaction of plasmonic materials with complex biological environments.","PeriodicalId":72559,"journal":{"name":"Chemical physics reviews","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1063/5.0042547","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48088051","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}
S. Maiti, M. van der Laan, D. Poonia, P. Schall, S. Kinge, L. Siebbeles
In conventional solar cell semiconductor materials (predominantly Si) photons with energy higher than the band gap initially generate hot electrons and holes, which subsequently cool down to the band edge by phonon emission. Due to the latter process, the energy of the charge carriers in excess of the band gap is lost as heat and does not contribute to the conversion of solar to electrical power. If the excess energy is more than the band gap it can in principle be utilized through a process known as carrier multiplication (CM) in which a single absorbed photon generates two (or more) pairs of electrons and holes. Thus, through CM the photon energy above twice the band gap enhances the photocurrent of a solar cell. In this review, we discuss recent progress in CM research in terms of fundamental understanding, emergence of new materials for efficient CM, and CM based solar cell applications. Based on our current understanding, the CM threshold can get close to the minimal value of twice the band gap in materials where a photon induces an asymmetric electronic transition from a deeper valence band or to a higher conduction band. In addition, the material must have a low exciton binding energy and high charge carrier mobility, so that photoexcitation leads directly to the formation of free charges that can readily be extracted at external electrodes of a photovoltaic device. Percolative networks of coupled PbSe quantum dots, Sn/Pb based halide perovskites, and transition metal dichalcogenides such as MoTe2 fulfill these requirements to a large extent. These findings point towards promising prospects for further development of new materials for highly efficient photovoltaics.
{"title":"Emergence of new materials for exploiting highly efficient carrier multiplication in photovoltaics","authors":"S. Maiti, M. van der Laan, D. Poonia, P. Schall, S. Kinge, L. Siebbeles","doi":"10.1063/5.0025748","DOIUrl":"https://doi.org/10.1063/5.0025748","url":null,"abstract":"In conventional solar cell semiconductor materials (predominantly Si) photons with energy higher than the band gap initially generate hot electrons and holes, which subsequently cool down to the band edge by phonon emission. Due to the latter process, the energy of the charge carriers in excess of the band gap is lost as heat and does not contribute to the conversion of solar to electrical power. If the excess energy is more than the band gap it can in principle be utilized through a process known as carrier multiplication (CM) in which a single absorbed photon generates two (or more) pairs of electrons and holes. Thus, through CM the photon energy above twice the band gap enhances the photocurrent of a solar cell. In this review, we discuss recent progress in CM research in terms of fundamental understanding, emergence of new materials for efficient CM, and CM based solar cell applications. Based on our current understanding, the CM threshold can get close to the minimal value of twice the band gap in materials where a photon induces an asymmetric electronic transition from a deeper valence band or to a higher conduction band. In addition, the material must have a low exciton binding energy and high charge carrier mobility, so that photoexcitation leads directly to the formation of free charges that can readily be extracted at external electrodes of a photovoltaic device. Percolative networks of coupled PbSe quantum dots, Sn/Pb based halide perovskites, and transition metal dichalcogenides such as MoTe2 fulfill these requirements to a large extent. These findings point towards promising prospects for further development of new materials for highly efficient photovoltaics.","PeriodicalId":72559,"journal":{"name":"Chemical physics reviews","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-08-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1063/5.0025748","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41467552","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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