A formula was proved for computing the zeroth-order general Randic index of a hexagonal system to explore the correlation between the zeroth-order general Randic index and the π-electronic energy of a hexagonal syste...A formula was proved for computing the zeroth-order general Randic index of a hexagonal system to explore the correlation between the zeroth-order general Randic index and the π-electronic energy of a hexagonal system.As a consequence,the extremal hexagonal systems with minimum or maximum zeroth-order general Randic index were completely characterized.Moreover,by using the least-square fit method and regression analysis,a new and close relation was found between the zeroth-order general Randic index and the π-electronic energy of a hexagonal system.So the zeroth-order general Randic index is a good measure of the π-electronic energies for benzenoid hydrocarbons.展开更多
Making use of the adiabatic hyperspherical approach, we report a calculation for the energy spectrum of the ground and low-excited states of the confined helium atom in a spherical parabolic well. We find that the ene...Making use of the adiabatic hyperspherical approach, we report a calculation for the energy spectrum of the ground and low-excited states of the confined helium atom in a spherical parabolic well. We find that the energies of a spherical parabolic well are in good agreement with those of an impenetrable spherical box for the larger confined potential radius. However, the energy values of a spherical parabolic well are much lower than those of an impenetrable spherical box for small values of re. We also find that the confinement may cause accidental degeneracies between levels with different low-excited states and the inversion of the energy values.展开更多
Increasing the availability ofπ-electron in graphitic carbon nitride(g-C_(3)N_(4))can reduce the band gap and thus enhance the photocatalytic hydrogen(H_(2))generation activity upon exposure to visible light,However,...Increasing the availability ofπ-electron in graphitic carbon nitride(g-C_(3)N_(4))can reduce the band gap and thus enhance the photocatalytic hydrogen(H_(2))generation activity upon exposure to visible light,However,such strategy has not yet been largely applied to increase the H_(2)generation of g-C_(3)N_(4).Herein,we succes s fully increased the amount ofπ-electron in g-C_(3)N_(4)by incorporatingπ-electron-rich benzene rings through copolymerization of melamine and trimesic acid in air.The incorporation of benzene rings not only extends the light absorption of g-C_(3)N_(4)to 650 nm,but also improves the electrical conductivity due to delocalization ofπelectrons in benzene rings.As a result,a 3.4 times enhancement of photocatalytic H_(2)generation was achieved from the g-C_(3)N_(4)with benzene ring incorporation in comparing with that of pristine g-C_(3)N_(4).More interestingly,H_(2)generation still occurs under irradiation of the light ofλ≥490 nm,above the absorption edge of pristine g-C_(3)N_(4)(~460 nm),illustrating the positive effectiveness of incorporated benzene rings on enhancing the H_(2)generation capacity of g-C_(3)N_(4).The present work manifests the advantages of increasingπ-conjugated electrons on designing highly active g-C_(3)N_(4)photocatalysts.展开更多
Photocatalysis using polymeric carbon nitride(CN)materials is a constantly evolving field,where the variation of synthetic procedures allows the constant improvement of activity by tackling the intrinsic limitations o...Photocatalysis using polymeric carbon nitride(CN)materials is a constantly evolving field,where the variation of synthetic procedures allows the constant improvement of activity by tackling the intrinsic limitations of these materials(optical absorbance,specific surface area,charge migration,etc.).Amongst the possible photocatalytic reactions,the most popular application of CNs is the hydrogen evolution reaction(HER)from water.In this work,we design precisely-controlled carbon-doped porous CN rods with extended π-electron conjugation from supramolecular assemblies of melem and co-monomers,which partially substitute nitrogen for carbon atoms at the pyrimidine ring of the melem.Dense hydrogen bonds and good thermal stability of the melem-based supramolecular framework allow synthesizing a more ordered structure for improved charge migration;the control from the molecular level over the position of carbon-substituted nitrogen positions tailors the band alignment and photogenerated charge separation.The optimal photocatalyst shows an excellent HER rate(up to 10.16 mmol·h-1·g-1 under 100 W white light-emitting diode(LED)irradiation,with an apparent quantum efficiency of 20.0%at 405 nm,which is 23.2 times higher compared to a reference bulk CN).To fully harness the benefits of the developed metal-free CNs,selective oxidation reaction of aromatic alcohols is demonstrated with high conversion and selectivity.展开更多
In this work, an implicit analytic energy function for an electron in a many-center system is derived. The formalism is based on the concept of LCAO in the direct space and the representation of wave functions in the ...In this work, an implicit analytic energy function for an electron in a many-center system is derived. The formalism is based on the concept of LCAO in the direct space and the representation of wave functions in the momentum space. In principle, any order of accuracy can be accomplished by iteration. The implicit analytic energy function is discussed thoroughly with a presentation concerning its potential application to molecular problems which are related to the variation of bond angles and lengths.展开更多
P-glycoprotein(ABCB1)is the first discovered mammalian member of the large family of ATP binding cassette(ABC)transporters.It facilitates the movement of compounds(called allocrites)across membranes,using the energy o...P-glycoprotein(ABCB1)is the first discovered mammalian member of the large family of ATP binding cassette(ABC)transporters.It facilitates the movement of compounds(called allocrites)across membranes,using the energy of ATP binding and hydrolysis.Here,we review the thermodynamics of allocrite binding and the kinetics of ATP hydrolysis by ABCB1.In combination with our previous molecular dynamics simulations,these data lead to a new model for allocrite transport by ABCB1.In contrast to previous models,we take into account that the transporter was evolutionarily optimized to operate within a membrane,which dictates the nature of interactions.Hydrophobic interactions drive lipid-water partitioning of allocrites,the transport process’s first step.Weak dipolar interactions(including hydrogen bonding,π-π stacking,and π-cation interactions)drive allocrite recognition,binding,and transport by ABCB1 within the membrane.Increasing the lateral membrane packing density reduces allocrite partitioning but enhances dipolar interactions between allocrites and ABCB1.Allocrite flopping(or reorientation of the polar part towards the extracellular aqueous phase)occurs after hydrolysis of one ATP molecule and opening of ABCB1 at the extracellular side.Rebinding of ATP re-closes the transporter at the extracellular side and expels the potentially remaining allocrite into the membrane.The high sensitivity of the steady-state ATP hydrolysis rate to the nature and number of dipolar interactions,as well as to the dielectric constant of the membrane,points to a flopping process,which occurs to a large extent at the membrane-transporter interface.The proposed unidirectional ABCB1 transport cycle,driven by weak dipolar interactions,is consistent with membrane biophysics.展开更多
Development of organic semiconductors is one of the most intriguing and productive topics in material science and engineering. Many efforts have been made on the synthesis of aromatic building blocks such as benzene, ...Development of organic semiconductors is one of the most intriguing and productive topics in material science and engineering. Many efforts have been made on the synthesis of aromatic building blocks such as benzene, thiophene and pyrrole due to the facile preparation accompanied by the intrinsic environmental stability and relatively efficient properties of the resulting polymers. In the past, furan has been less explored in this field because of its high oxidation potential. Recently, furan has attracted obsession due to its weaker aromaticity, the greater solubilities of furan-containing π-conjugated polymers relative to other benzenoid systems and the accessibility of furan-based starting materials from renewable resources. This review elaborates the advancements of organic photovoltaic polymers containing furan building blocks. The uniqueness and advantages of furan-containing building blocks in semiconducting materials are also discussed.展开更多
Just as Tang and Jiang pointed out in ref. [1], the total π-electron energy E<sub>π</sub> of a conjugate molecule is of significance for understanding the stability and aromatic character of molecule or ...Just as Tang and Jiang pointed out in ref. [1], the total π-electron energy E<sub>π</sub> of a conjugate molecule is of significance for understanding the stability and aromatic character of molecule or the reaction route. They also proposed the expanded formula for evaluating E<sub>π</sub> by using molecular moment μ<sub>1</sub>.展开更多
Polymer dielectric is superior to its inorganic counterparts due to not only the low cost and intrinsic flexibility,but also the readily tunable dielectric constant,surface charge trap density,charge ejection and rele...Polymer dielectric is superior to its inorganic counterparts due to not only the low cost and intrinsic flexibility,but also the readily tunable dielectric constant,surface charge trap density,charge ejection and releasing ability and dipole moment,and all these properties play decisive roles in regulating the characteristic and performances of organic thin film transistors(OTFT).However,systematical studies on the relationship between structure and properties of polymeric dielectrics are rare.To this end,a series of polymeric dielectrics with well-defined linkages(ester or amide bonds)and predesigned pendant groups(alkyl-and aromatic-groups)are synthesized in high yields.Detailed studies show that the polyamide dielectrics exhibit higher dielectric constant,surface charge trapping density,and better charge storage capability than corresponding polyester dielectrics.Further,increasing theπelectron delocalization of the pendant groups generally benefits the charge storage property and transistor memory behavior.Theoretical calculation reveals that the hydrogen bonding between the linkage groups and the energy alignment between polymeric dielectric and semiconductor are responsible for the observed performance differences of OTFT with different polymeric dielectrics.These results may shine light on the design of polymeric dielectrics for OTFTs with different applications.展开更多
The conjugated polycycles show excellent optical and electrical properties that are suitable for application in various organic electronics.While most of attentions have been paid to polycycles having planar π-conjug...The conjugated polycycles show excellent optical and electrical properties that are suitable for application in various organic electronics.While most of attentions have been paid to polycycles having planar π-conjugated system,the curved polycycles seem amazing due to their unique physical and chemical features.The non-planar conjugated polycycles have been created with the geometries of bracelet,saddle,bowl,Mobius band,helicenes,etc.Among them,the bowl-shaped one is of growing interest owing to the multidiscipline applications such as synthetic intermediates for end-cap of carbon nanotube,coordination with metal ions,encapsulation of fullerenes,and fabrication of electronic devices.In this paper,we summarize the recent advances on the chemistry of the bowl-shaped conjugated polycycles,particularly on their synthesis and the further chemical modifications toward organic functional materials.展开更多
基金National Natural Science Foundation of China (No. 10901034)Chenguang Program of Shanghai Education Development Foundation,China (No. 2008CG40)
文摘A formula was proved for computing the zeroth-order general Randic index of a hexagonal system to explore the correlation between the zeroth-order general Randic index and the π-electronic energy of a hexagonal system.As a consequence,the extremal hexagonal systems with minimum or maximum zeroth-order general Randic index were completely characterized.Moreover,by using the least-square fit method and regression analysis,a new and close relation was found between the zeroth-order general Randic index and the π-electronic energy of a hexagonal system.So the zeroth-order general Randic index is a good measure of the π-electronic energies for benzenoid hydrocarbons.
基金Supported by the National Natural Science Foundation of China under Grant No 10475021, and the Natural Science Foundation of Guangdong Province under Grant No 04009519.
文摘Making use of the adiabatic hyperspherical approach, we report a calculation for the energy spectrum of the ground and low-excited states of the confined helium atom in a spherical parabolic well. We find that the energies of a spherical parabolic well are in good agreement with those of an impenetrable spherical box for the larger confined potential radius. However, the energy values of a spherical parabolic well are much lower than those of an impenetrable spherical box for small values of re. We also find that the confinement may cause accidental degeneracies between levels with different low-excited states and the inversion of the energy values.
基金financially supported by the National Natural Science Foundation of China(Nos.51872003 and 51572003)the University Natural Science Research Project of Anhui Province(No.KJ2017A299)+1 种基金the Anhui Provincial Natural Science Foundation(Nos.1908085J21 and 1908085QB83)the Research Start-up Fund of Anhui University(No.S020118002/011)。
文摘Increasing the availability ofπ-electron in graphitic carbon nitride(g-C_(3)N_(4))can reduce the band gap and thus enhance the photocatalytic hydrogen(H_(2))generation activity upon exposure to visible light,However,such strategy has not yet been largely applied to increase the H_(2)generation of g-C_(3)N_(4).Herein,we succes s fully increased the amount ofπ-electron in g-C_(3)N_(4)by incorporatingπ-electron-rich benzene rings through copolymerization of melamine and trimesic acid in air.The incorporation of benzene rings not only extends the light absorption of g-C_(3)N_(4)to 650 nm,but also improves the electrical conductivity due to delocalization ofπelectrons in benzene rings.As a result,a 3.4 times enhancement of photocatalytic H_(2)generation was achieved from the g-C_(3)N_(4)with benzene ring incorporation in comparing with that of pristine g-C_(3)N_(4).More interestingly,H_(2)generation still occurs under irradiation of the light ofλ≥490 nm,above the absorption edge of pristine g-C_(3)N_(4)(~460 nm),illustrating the positive effectiveness of incorporated benzene rings on enhancing the H_(2)generation capacity of g-C_(3)N_(4).The present work manifests the advantages of increasingπ-conjugated electrons on designing highly active g-C_(3)N_(4)photocatalysts.
基金grateful for the financial support from the National Natural Science Foundation of China(Nos.22078028 and 21978026)the Special Program for Introducing Foreign Talents of Changzhou(No.CQ20214032)+1 种基金the joint Israel Science Foundation-National Science Foundation of China(ISF-NSFC)(No.2969/19 and the ISF No.601/21)The authors thank Jonathan Tzadikov,Rotem Geva,Liel Abisdris,Junyi Li,and Ayelet Tashakory(Ben-Gurion University of the Negev)for technical support and Dr.Laurent Chabanne for fruitful discussion.
文摘Photocatalysis using polymeric carbon nitride(CN)materials is a constantly evolving field,where the variation of synthetic procedures allows the constant improvement of activity by tackling the intrinsic limitations of these materials(optical absorbance,specific surface area,charge migration,etc.).Amongst the possible photocatalytic reactions,the most popular application of CNs is the hydrogen evolution reaction(HER)from water.In this work,we design precisely-controlled carbon-doped porous CN rods with extended π-electron conjugation from supramolecular assemblies of melem and co-monomers,which partially substitute nitrogen for carbon atoms at the pyrimidine ring of the melem.Dense hydrogen bonds and good thermal stability of the melem-based supramolecular framework allow synthesizing a more ordered structure for improved charge migration;the control from the molecular level over the position of carbon-substituted nitrogen positions tailors the band alignment and photogenerated charge separation.The optimal photocatalyst shows an excellent HER rate(up to 10.16 mmol·h-1·g-1 under 100 W white light-emitting diode(LED)irradiation,with an apparent quantum efficiency of 20.0%at 405 nm,which is 23.2 times higher compared to a reference bulk CN).To fully harness the benefits of the developed metal-free CNs,selective oxidation reaction of aromatic alcohols is demonstrated with high conversion and selectivity.
文摘In this work, an implicit analytic energy function for an electron in a many-center system is derived. The formalism is based on the concept of LCAO in the direct space and the representation of wave functions in the momentum space. In principle, any order of accuracy can be accomplished by iteration. The implicit analytic energy function is discussed thoroughly with a presentation concerning its potential application to molecular problems which are related to the variation of bond angles and lengths.
基金Stiftung zur Forderung der biologischen Forschung,Basel,Switzerland.
文摘P-glycoprotein(ABCB1)is the first discovered mammalian member of the large family of ATP binding cassette(ABC)transporters.It facilitates the movement of compounds(called allocrites)across membranes,using the energy of ATP binding and hydrolysis.Here,we review the thermodynamics of allocrite binding and the kinetics of ATP hydrolysis by ABCB1.In combination with our previous molecular dynamics simulations,these data lead to a new model for allocrite transport by ABCB1.In contrast to previous models,we take into account that the transporter was evolutionarily optimized to operate within a membrane,which dictates the nature of interactions.Hydrophobic interactions drive lipid-water partitioning of allocrites,the transport process’s first step.Weak dipolar interactions(including hydrogen bonding,π-π stacking,and π-cation interactions)drive allocrite recognition,binding,and transport by ABCB1 within the membrane.Increasing the lateral membrane packing density reduces allocrite partitioning but enhances dipolar interactions between allocrites and ABCB1.Allocrite flopping(or reorientation of the polar part towards the extracellular aqueous phase)occurs after hydrolysis of one ATP molecule and opening of ABCB1 at the extracellular side.Rebinding of ATP re-closes the transporter at the extracellular side and expels the potentially remaining allocrite into the membrane.The high sensitivity of the steady-state ATP hydrolysis rate to the nature and number of dipolar interactions,as well as to the dielectric constant of the membrane,points to a flopping process,which occurs to a large extent at the membrane-transporter interface.The proposed unidirectional ABCB1 transport cycle,driven by weak dipolar interactions,is consistent with membrane biophysics.
基金financially supported by the National Natural Science Foundation of China(Nos.21574144,51273209 and 51411140244)Zhejiang Provincial Natural Science Foundation of China(No.LR16B040002)+1 种基金CAS Interdisciplinary Innovation Team and Ningbo Municipal Science and Technology Innovative Research Team(Nos.2015B11002 and 2016B10005)Ningbo Natural Science Foundation(No.2016A610277)
文摘Development of organic semiconductors is one of the most intriguing and productive topics in material science and engineering. Many efforts have been made on the synthesis of aromatic building blocks such as benzene, thiophene and pyrrole due to the facile preparation accompanied by the intrinsic environmental stability and relatively efficient properties of the resulting polymers. In the past, furan has been less explored in this field because of its high oxidation potential. Recently, furan has attracted obsession due to its weaker aromaticity, the greater solubilities of furan-containing π-conjugated polymers relative to other benzenoid systems and the accessibility of furan-based starting materials from renewable resources. This review elaborates the advancements of organic photovoltaic polymers containing furan building blocks. The uniqueness and advantages of furan-containing building blocks in semiconducting materials are also discussed.
文摘Just as Tang and Jiang pointed out in ref. [1], the total π-electron energy E<sub>π</sub> of a conjugate molecule is of significance for understanding the stability and aromatic character of molecule or the reaction route. They also proposed the expanded formula for evaluating E<sub>π</sub> by using molecular moment μ<sub>1</sub>.
基金supported by the start-up funding from FJIRSM-CASNational Natural Science foundation of China(51803214)。
文摘Polymer dielectric is superior to its inorganic counterparts due to not only the low cost and intrinsic flexibility,but also the readily tunable dielectric constant,surface charge trap density,charge ejection and releasing ability and dipole moment,and all these properties play decisive roles in regulating the characteristic and performances of organic thin film transistors(OTFT).However,systematical studies on the relationship between structure and properties of polymeric dielectrics are rare.To this end,a series of polymeric dielectrics with well-defined linkages(ester or amide bonds)and predesigned pendant groups(alkyl-and aromatic-groups)are synthesized in high yields.Detailed studies show that the polyamide dielectrics exhibit higher dielectric constant,surface charge trapping density,and better charge storage capability than corresponding polyester dielectrics.Further,increasing theπelectron delocalization of the pendant groups generally benefits the charge storage property and transistor memory behavior.Theoretical calculation reveals that the hydrogen bonding between the linkage groups and the energy alignment between polymeric dielectric and semiconductor are responsible for the observed performance differences of OTFT with different polymeric dielectrics.These results may shine light on the design of polymeric dielectrics for OTFTs with different applications.
基金the National Natural Science Foundation of China(Nos.21522203,21372111,and 21190034)State Key Laboratory of Applied Organic Chemistry for the financial support
文摘The conjugated polycycles show excellent optical and electrical properties that are suitable for application in various organic electronics.While most of attentions have been paid to polycycles having planar π-conjugated system,the curved polycycles seem amazing due to their unique physical and chemical features.The non-planar conjugated polycycles have been created with the geometries of bracelet,saddle,bowl,Mobius band,helicenes,etc.Among them,the bowl-shaped one is of growing interest owing to the multidiscipline applications such as synthetic intermediates for end-cap of carbon nanotube,coordination with metal ions,encapsulation of fullerenes,and fabrication of electronic devices.In this paper,we summarize the recent advances on the chemistry of the bowl-shaped conjugated polycycles,particularly on their synthesis and the further chemical modifications toward organic functional materials.