{"title":"Peculiar Hydrogen-Bond Structure, Physical Properties and Function of Interfacial Water Molecules Elucidated by Nonlinear Laser Spectroscopy","authors":"T. Sugimoto","doi":"10.3175/molsci.14.a0112","DOIUrl":"https://doi.org/10.3175/molsci.14.a0112","url":null,"abstract":"","PeriodicalId":19105,"journal":{"name":"Molecular Science","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83715286","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}
Heterogeneous systems consisting with nanomaterials (hereafter referred to as nanointerface systems) are exten-sively investigated in relation to interests in batteries, photo-and electro-catalysts, solar cells, and optoelectronic devices. To efficiently design these functional materials, it is required to obtain atomic-scale insights into the response mechanism to light and voltage bias. However, first-principles theoretical studies on nanointerface systems under light and voltage bias have been scarcely performed because of two problems. Firstly, a huge computational cost is needed to calculate a nanointerface system with a first-principles computational method. Secondly, it is difficult to theoretically describe electronic structure explicitly considering light and voltage bias. In this review, we report the recent progress in our theoretical and computational studies on nanointerface systems. The optical response of various systems such as a gold-thiolate nanocluster and a MoS 2 -graphene heterostructure has been simulated using a first-principles computational method for carrying out massively parallel calculations of photoexcited electron dynamics. The computational results have been analyzed with theoretical formulas for revealing the role of the interface region in the optical response. We have also developed an original theoretical method for investigating electrode systems. The developed method has been used to elucidate the mechanism of the electronic structure change inherent in nanointerface systems by applying bias voltage, which causes the electronic charging and generates the electric field from a gate electrode.
{"title":"Theoretical Study on Response of Nanointerface Systems to Light and Voltage Bias","authors":"K. Iida","doi":"10.3175/molsci.14.a0110","DOIUrl":"https://doi.org/10.3175/molsci.14.a0110","url":null,"abstract":"Heterogeneous systems consisting with nanomaterials (hereafter referred to as nanointerface systems) are exten-sively investigated in relation to interests in batteries, photo-and electro-catalysts, solar cells, and optoelectronic devices. To efficiently design these functional materials, it is required to obtain atomic-scale insights into the response mechanism to light and voltage bias. However, first-principles theoretical studies on nanointerface systems under light and voltage bias have been scarcely performed because of two problems. Firstly, a huge computational cost is needed to calculate a nanointerface system with a first-principles computational method. Secondly, it is difficult to theoretically describe electronic structure explicitly considering light and voltage bias. In this review, we report the recent progress in our theoretical and computational studies on nanointerface systems. The optical response of various systems such as a gold-thiolate nanocluster and a MoS 2 -graphene heterostructure has been simulated using a first-principles computational method for carrying out massively parallel calculations of photoexcited electron dynamics. The computational results have been analyzed with theoretical formulas for revealing the role of the interface region in the optical response. We have also developed an original theoretical method for investigating electrode systems. The developed method has been used to elucidate the mechanism of the electronic structure change inherent in nanointerface systems by applying bias voltage, which causes the electronic charging and generates the electric field from a gate electrode.","PeriodicalId":19105,"journal":{"name":"Molecular Science","volume":"61 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83805968","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}
Understanding of the electronic structure and photoexcited state dynamics at well-prepared layered functional materials on substrates is essentially important in order to precisely design and control the future electronic or optical nanodevices. I have been so far engaged in this research field experimentally from the view point of molecular science, where the electronic states and dynamics at nanoscale functional films fabricated with organic molecules and/or nanocluster superatoms are investigated by probing photoelectrons, combining with a femtosecond light source and with a nanocluster deposition system. In this account, firstly, I show the electronic structures and photoexcited state dynamics at two-dimensional (2D) molecular monolayer systems of alkanethiolate self-assembled monolayers by two-photon photoemission spectroscopy which clarifies novel ultrafast phenomena characteristic to the 2D assembly of the functional molecules. Secondly, I present the visualization of local photoexcited states in the organic films by changing the probe system into two-photon photoelectron emission microscopy. Finally, the electronic states and chemical properties of nanocluster superatoms as a new class of functional nanomaterials are explained, which are non-destructively landed onto the substrates.
{"title":"Study on Electron Dynamics at Nanoscale Functional Films","authors":"M. Shibuta","doi":"10.3175/molsci.13.a0105","DOIUrl":"https://doi.org/10.3175/molsci.13.a0105","url":null,"abstract":"Understanding of the electronic structure and photoexcited state dynamics at well-prepared layered functional materials on substrates is essentially important in order to precisely design and control the future electronic or optical nanodevices. I have been so far engaged in this research field experimentally from the view point of molecular science, where the electronic states and dynamics at nanoscale functional films fabricated with organic molecules and/or nanocluster superatoms are investigated by probing photoelectrons, combining with a femtosecond light source and with a nanocluster deposition system. In this account, firstly, I show the electronic structures and photoexcited state dynamics at two-dimensional (2D) molecular monolayer systems of alkanethiolate self-assembled monolayers by two-photon photoemission spectroscopy which clarifies novel ultrafast phenomena characteristic to the 2D assembly of the functional molecules. Secondly, I present the visualization of local photoexcited states in the organic films by changing the probe system into two-photon photoelectron emission microscopy. Finally, the electronic states and chemical properties of nanocluster superatoms as a new class of functional nanomaterials are explained, which are non-destructively landed onto the substrates.","PeriodicalId":19105,"journal":{"name":"Molecular Science","volume":"43 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88163188","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}
Finding transition states are important for analyzing chemical reactions, but revealing the reaction dynamics can be also essential in understanding many realistic reactions. For instance, recent experiments have shed light on the importance of protein’s heterogeneous dynamics in the native state and during function, and ultrafast dynamics in photo-triggered chemical reactions have been studied over decades. However, most efforts in theoretical studies have been devoted to characterizing transition states and calculating ensemble-averaged properties, e.g. free energy profi les, whereas the dynamics have been of less focus. In this account, we review our recent efforts toward revealing the dynamics of reactions under diverse conditions from the theoretical perspective. We discuss three cases, i.e. photo-isomerization reaction in gas phase, and protein folding and enzyme catalysis in condensed phase. The key in these studies has been to shed light on the individual events occurring during reactions, rather than focusing only on the characteristic states and ensemble averages. These studies show that dynamics play a fundamental role in all three cases, and demonstrate how the dynamics analyses can deepen our understanding of the reactions under various conditions.
{"title":"Theoretical Study of Reaction Dynamics in Gas and Condensed Phases","authors":"Toshifumi Mori","doi":"10.3175/molsci.13.a0106","DOIUrl":"https://doi.org/10.3175/molsci.13.a0106","url":null,"abstract":"Finding transition states are important for analyzing chemical reactions, but revealing the reaction dynamics can be also essential in understanding many realistic reactions. For instance, recent experiments have shed light on the importance of protein’s heterogeneous dynamics in the native state and during function, and ultrafast dynamics in photo-triggered chemical reactions have been studied over decades. However, most efforts in theoretical studies have been devoted to characterizing transition states and calculating ensemble-averaged properties, e.g. free energy profi les, whereas the dynamics have been of less focus. In this account, we review our recent efforts toward revealing the dynamics of reactions under diverse conditions from the theoretical perspective. We discuss three cases, i.e. photo-isomerization reaction in gas phase, and protein folding and enzyme catalysis in condensed phase. The key in these studies has been to shed light on the individual events occurring during reactions, rather than focusing only on the characteristic states and ensemble averages. These studies show that dynamics play a fundamental role in all three cases, and demonstrate how the dynamics analyses can deepen our understanding of the reactions under various conditions.","PeriodicalId":19105,"journal":{"name":"Molecular Science","volume":"42 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77035094","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":"Organic Functional Materials Based on Molecular Motion in the Condensed Phases","authors":"T. Takeda","doi":"10.3175/molsci.13.a0102","DOIUrl":"https://doi.org/10.3175/molsci.13.a0102","url":null,"abstract":"","PeriodicalId":19105,"journal":{"name":"Molecular Science","volume":"19 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78883714","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}
Development of novel molecular materials has been a central issue in molecular science. In this study, we have successfully developed a new type of molecular conductor, where the π -electrons in the conducting layers are coupled to hydrogen dynamics in hydrogen bonds. This unique feature has enabled us to control the π -electron structures and properties by using the hydrogen dynamics. In this paper, the synthesis, structures, and properties of this new type of molecular conductor are summarized, especially focusing on the H/D isotope effect, phase transition behavior, and pressure and electric-field effects.
{"title":"Development of Novel Molecular Conductors with Hydrogen Dynamics","authors":"A. Ueda","doi":"10.3175/molsci.13.a0103","DOIUrl":"https://doi.org/10.3175/molsci.13.a0103","url":null,"abstract":"Development of novel molecular materials has been a central issue in molecular science. In this study, we have successfully developed a new type of molecular conductor, where the π -electrons in the conducting layers are coupled to hydrogen dynamics in hydrogen bonds. This unique feature has enabled us to control the π -electron structures and properties by using the hydrogen dynamics. In this paper, the synthesis, structures, and properties of this new type of molecular conductor are summarized, especially focusing on the H/D isotope effect, phase transition behavior, and pressure and electric-field effects.","PeriodicalId":19105,"journal":{"name":"Molecular Science","volume":"6 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90180452","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 surfaces are a playground for heterogeneous reactions including catalysis and electrochemistry. They also serve as a template for thin film growth and an electrode in various devices. Thus, metal surfaces are important in both fundamental and applied sciences. This review presents two topics regarding the structure and dynamics of adsorbates on metal surfaces probed with sum frequency generation (SFG) spectroscopy. First, the directional orientation of water molecules in the ice crystalline thin film grown on a Pt(111) surface is described. Heterodyne detection of SFG makes it possible to determine the direction of water at the metal surface: they are preferentially oriented such that one of hydrogen atoms is directed toward the metal surface. This directional configuration propagates in the bulk of ice crystalline film through hydrogen bond network. Second, the ultrafast dynamics in the early stage of photo-stimulated desorption of CO on Cu(100) is described. Here the heterodyne detection of SFG is employed in pump-and-probe measurements. The phase and amplitude of SFG optical field obtained with this method are used for retrieving the perturbed free induction decay of CO stretch vibration polarization. This allows us to probe adsorbate dynamics leading to desorption induced by irradiation of an intense pump pulse. The ultrafast dynamics of adsorbates are the manifesta-tion of coupling between hot electrons in metal and frustrated motions of CO at the surface, which provide a clue for understanding nonadiabatic processes accompanying adsorbate motions, which are ubiquitous in metal and at its surface.
{"title":"Structure and Dynamics of Adsorbates on Metal Surfaces Investigated with Nonlinear Optical Spectroscopy","authors":"Y. Matsumoto","doi":"10.3175/molsci.13.a0107","DOIUrl":"https://doi.org/10.3175/molsci.13.a0107","url":null,"abstract":"Metal surfaces are a playground for heterogeneous reactions including catalysis and electrochemistry. They also serve as a template for thin film growth and an electrode in various devices. Thus, metal surfaces are important in both fundamental and applied sciences. This review presents two topics regarding the structure and dynamics of adsorbates on metal surfaces probed with sum frequency generation (SFG) spectroscopy. First, the directional orientation of water molecules in the ice crystalline thin film grown on a Pt(111) surface is described. Heterodyne detection of SFG makes it possible to determine the direction of water at the metal surface: they are preferentially oriented such that one of hydrogen atoms is directed toward the metal surface. This directional configuration propagates in the bulk of ice crystalline film through hydrogen bond network. Second, the ultrafast dynamics in the early stage of photo-stimulated desorption of CO on Cu(100) is described. Here the heterodyne detection of SFG is employed in pump-and-probe measurements. The phase and amplitude of SFG optical field obtained with this method are used for retrieving the perturbed free induction decay of CO stretch vibration polarization. This allows us to probe adsorbate dynamics leading to desorption induced by irradiation of an intense pump pulse. The ultrafast dynamics of adsorbates are the manifesta-tion of coupling between hot electrons in metal and frustrated motions of CO at the surface, which provide a clue for understanding nonadiabatic processes accompanying adsorbate motions, which are ubiquitous in metal and at its surface.","PeriodicalId":19105,"journal":{"name":"Molecular Science","volume":"15 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88255500","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":"Temperature Effect on the Microscopic Hydrogen-Bond Networks Investigated from the Viewpoint of the Gas-Phase Molecular Cluster","authors":"H. Ishikawa","doi":"10.3175/MOLSCI.12.A0101","DOIUrl":"https://doi.org/10.3175/MOLSCI.12.A0101","url":null,"abstract":"","PeriodicalId":19105,"journal":{"name":"Molecular Science","volume":"95 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80657858","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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