Molecular catalysts for H2-evolution are of interest for their integration into light-harvesting complexes for photocatalytic water splitting.Here,we report the meso-tetra(4-carboxyphenyl)porphine[(TCPP)Pt^(Ⅱ)]comple...Molecular catalysts for H2-evolution are of interest for their integration into light-harvesting complexes for photocatalytic water splitting.Here,we report the meso-tetra(4-carboxyphenyl)porphine[(TCPP)Pt^(Ⅱ)]complex as a molecular H2-evolving photocatalyst using chloranilic acid(CA)as a sacrificial electron donor,the choice of which is critical to the stability of the photocatalyst.When triethanolamine was used,[(TCPP)Pt^(Ⅱ)]decomposed to form Pt nanoparticles.Density functional theory calculations together with evidence from electrochemical and spectroscopic analyses suggested that the catalysis was possibly initiated by a proton-coupled electron transfer(PCET)to form[(TCPP)Pt^(Ⅰ)]-N-H,followed by another electron injection and protonation to form a[(TCPP)Pt^(Ⅱ)-hydride]-N-H intermediate that can release H2.As the whole catalytic cycle involves the injection of multiple electrons,a light-harvesting network should be helpful by providing multiple photo-induced electrons.Thus,we integrated this molecular catalyst into a light-harvesting metal-organic framework to boost its activity by~830 times.This work presents a mechanistic study of the photocatalytic H2 evolution and energy transfer and highlights the importance of a light-harvesting network for multiple electron injections.展开更多
To date, few reports have been concerned with the physical properties of the liquid phases of imidazoles and benzimidazoles- potential starting materials for a great number of ionic liquids. Prior research has indicat...To date, few reports have been concerned with the physical properties of the liquid phases of imidazoles and benzimidazoles- potential starting materials for a great number of ionic liquids. Prior research has indicated that alkylimidazole solvents exhibit different, and potentially advantageous physical properties, when compared to corresponding imidazolium-based ionic liquids. Given that even the most fundamental physical properties of alkylimidazole solvents have only recently been reported, there is still a lack of data for other relevant imidazole derivatives, including benzimidazoles. In this work, we have synthesized a se- ries of eight 1-n-alkylbenzimidazoles, with chain lengths ranging from ethyl to dodecyl, all of which exist as neat liquids at ambient temperature. Their densities and viscosities have been determined as functions of both temperature and molecular weight. Alkylbenzimidazoles have been found to exhibit viscosities that are more similar to imidazolium-based ILs than al- kylimidazoles, owed to a large contribution to viscosity from the presence of a fused ring system. Solubilities of CO2 and SO2, two species of concern in the emission of coal-fired power generation, were determined for selected alkylbenzimidazoles to understand what effects a fused ring system might have on gas solubility. For both gases, alkylbenzimidazoles were deter- mined to experience physical, non-chemically reactive, interactions. The solubility of CO2 in alkylbenzimidazoles is 10%-30% less than observed for corresponding ILs and alkylimidazoles. 1-butylbenzimidazole was found to readily absorb at least 0.333 gram SO2 per gram at low pressure and ambient temperature, which could be readily desorbed under an N： flush, a behavior more similar to imidazolium-based ILs than alkylimidazoles. Thus, we find that as solvents for gas separations, benzimidazoles share characteristics with both ILs and alkylimidazoles.展开更多
We investigate the structure,trapping,and diffusion behaviors of helium(He) at vacancy in a Fe single crystal using first-principles simulations.Vacancy with more space can provide the lower electron density region fo...We investigate the structure,trapping,and diffusion behaviors of helium(He) at vacancy in a Fe single crystal using first-principles simulations.Vacancy with more space can provide the lower electron density region for He binding in comparison with intrinsic Fe,causing He to diffuse into the vacancy inner easily.We provide the quantitative microscopic studies related to the atomic-level thermo-kinetic trapping processes.Moreover,such physical viewpoint can be applied to other vacancy-like defects such as vacancy clusters,void and grain boundaries which can open a space with reduced electron density region to increase He binding in metals and metal alloys.展开更多
This paper reports a cell trapping and patterning method using dielectric-pattern-assisted negative dielectrophoresis (dnDEP) that can achieve high-density cell arrays and complicated cell patterns.The dnDEP device co...This paper reports a cell trapping and patterning method using dielectric-pattern-assisted negative dielectrophoresis (dnDEP) that can achieve high-density cell arrays and complicated cell patterns.The dnDEP device consists of two planar metal electrodes and a patterned dielectric layer sandwiched in-between.The dielectric patterns generate non-uniform electric fields when an ac voltage is applied on the two electrodes,and the interaction of polarizable cells and the non-uniform electric fields imposes negative DEP forces on the cells,pushing them to the patterns in the dielectric layer.Using this dnDEP device,human lymphoma cells were successfully patterned in high-density microwell arrays and stellate structures.Thanks to the three-dimensional configuration and the small distance between the electrodes,cell trapping and patterning can be implemented with a voltage of 10 V.This dnDEP device has the advantages of simple configuration,low actuating voltage,and the compatibility with high conductivity physiological media for cell culturing.展开更多
文摘Molecular catalysts for H2-evolution are of interest for their integration into light-harvesting complexes for photocatalytic water splitting.Here,we report the meso-tetra(4-carboxyphenyl)porphine[(TCPP)Pt^(Ⅱ)]complex as a molecular H2-evolving photocatalyst using chloranilic acid(CA)as a sacrificial electron donor,the choice of which is critical to the stability of the photocatalyst.When triethanolamine was used,[(TCPP)Pt^(Ⅱ)]decomposed to form Pt nanoparticles.Density functional theory calculations together with evidence from electrochemical and spectroscopic analyses suggested that the catalysis was possibly initiated by a proton-coupled electron transfer(PCET)to form[(TCPP)Pt^(Ⅰ)]-N-H,followed by another electron injection and protonation to form a[(TCPP)Pt^(Ⅱ)-hydride]-N-H intermediate that can release H2.As the whole catalytic cycle involves the injection of multiple electrons,a light-harvesting network should be helpful by providing multiple photo-induced electrons.Thus,we integrated this molecular catalyst into a light-harvesting metal-organic framework to boost its activity by~830 times.This work presents a mechanistic study of the photocatalytic H2 evolution and energy transfer and highlights the importance of a light-harvesting network for multiple electron injections.
基金supported by ION Engineering, LLCUnited States Department of Energy-National Energy Technology Laboratory(DE-FE00005799)the National Science Foundation Research Experiences for Undergraduates Program (EEC-1062705)
文摘To date, few reports have been concerned with the physical properties of the liquid phases of imidazoles and benzimidazoles- potential starting materials for a great number of ionic liquids. Prior research has indicated that alkylimidazole solvents exhibit different, and potentially advantageous physical properties, when compared to corresponding imidazolium-based ionic liquids. Given that even the most fundamental physical properties of alkylimidazole solvents have only recently been reported, there is still a lack of data for other relevant imidazole derivatives, including benzimidazoles. In this work, we have synthesized a se- ries of eight 1-n-alkylbenzimidazoles, with chain lengths ranging from ethyl to dodecyl, all of which exist as neat liquids at ambient temperature. Their densities and viscosities have been determined as functions of both temperature and molecular weight. Alkylbenzimidazoles have been found to exhibit viscosities that are more similar to imidazolium-based ILs than al- kylimidazoles, owed to a large contribution to viscosity from the presence of a fused ring system. Solubilities of CO2 and SO2, two species of concern in the emission of coal-fired power generation, were determined for selected alkylbenzimidazoles to understand what effects a fused ring system might have on gas solubility. For both gases, alkylbenzimidazoles were deter- mined to experience physical, non-chemically reactive, interactions. The solubility of CO2 in alkylbenzimidazoles is 10%-30% less than observed for corresponding ILs and alkylimidazoles. 1-butylbenzimidazole was found to readily absorb at least 0.333 gram SO2 per gram at low pressure and ambient temperature, which could be readily desorbed under an N： flush, a behavior more similar to imidazolium-based ILs than alkylimidazoles. Thus, we find that as solvents for gas separations, benzimidazoles share characteristics with both ILs and alkylimidazoles.
基金supported by the National Natural Science Foundation of China (Grant No. 51101135)the Natural Science Foundation of Shandong (Grant No. ZR2010AM002)
文摘We investigate the structure,trapping,and diffusion behaviors of helium(He) at vacancy in a Fe single crystal using first-principles simulations.Vacancy with more space can provide the lower electron density region for He binding in comparison with intrinsic Fe,causing He to diffuse into the vacancy inner easily.We provide the quantitative microscopic studies related to the atomic-level thermo-kinetic trapping processes.Moreover,such physical viewpoint can be applied to other vacancy-like defects such as vacancy clusters,void and grain boundaries which can open a space with reduced electron density region to increase He binding in metals and metal alloys.
基金supported in part by the National Natural Science Foundation of China (Grant No. 60871006)
文摘This paper reports a cell trapping and patterning method using dielectric-pattern-assisted negative dielectrophoresis (dnDEP) that can achieve high-density cell arrays and complicated cell patterns.The dnDEP device consists of two planar metal electrodes and a patterned dielectric layer sandwiched in-between.The dielectric patterns generate non-uniform electric fields when an ac voltage is applied on the two electrodes,and the interaction of polarizable cells and the non-uniform electric fields imposes negative DEP forces on the cells,pushing them to the patterns in the dielectric layer.Using this dnDEP device,human lymphoma cells were successfully patterned in high-density microwell arrays and stellate structures.Thanks to the three-dimensional configuration and the small distance between the electrodes,cell trapping and patterning can be implemented with a voltage of 10 V.This dnDEP device has the advantages of simple configuration,low actuating voltage,and the compatibility with high conductivity physiological media for cell culturing.
