The construction of heterojunction photocatalysts for efficiently utilizing solar energy has attracted considerable attention to solve the energy crisis and reduce environmental pollution.In this study,we use the ener...The construction of heterojunction photocatalysts for efficiently utilizing solar energy has attracted considerable attention to solve the energy crisis and reduce environmental pollution.In this study,we use the energy released from an easily-occurred exothermic chemical reaction to serve as the drive force to trigger the formation of Cd S and C_(3)N_(4) nanocomposites which are successfully fabricated with cadmium nitrate and thiourea without addition of any solvents and protection of inert gas at initial temperature,a little higher than the melting point of thiourea.The as-prepared Cd S/C_(3)N_(4) materials exhibit high efficiency for photocatalytic hydrogen evolution reaction(HER)with the HER rate as high as 15,866μmol/(g·hr)under visible light irradiation(λ>420 nm),which is 89 and 9 times those of pristine C_(3)N_(4) and Cd S,respectively.Also,the apparent quantum efficiency(AQE)of Cd S/C_(3)N_(4)–1:2–200–2(Cd S/C_(3)N_(4)–1:2–200–2 means the ratio of Cd to S is 1:2 and the reaction temperature is set at 200℃ for two hours)reaches 3.25%atλ=420±15 nm.After irradiated for more than 24 hr,the HER efficiencies of Cd S/C_(3)N_(4) do not exhibit any attenuation.The DFT calculation suggests that the charge difference causes an internal electric field from C_(3)N_(4) pointing to Cd S,which can more effectively promote the transfer of photogenerated electrons from Cd S to C_(3)N_(4).Therefore,most HER should occur on C_(3)N_(4) surface where photogenerated electrons accumulate,which largely protects Cd S from photo-corrosion.展开更多
Organic-inorganic nanojunctions can result in a selective scattering of charge carrier depending on their energy, which leads to a simultaneous increase in the Seebeck coefficient S and the power factor. In this work,...Organic-inorganic nanojunctions can result in a selective scattering of charge carrier depending on their energy, which leads to a simultaneous increase in the Seebeck coefficient S and the power factor. In this work, the nanojunction is successfully employed at the organic-inorganic semiconductor interface of polyparaphenylene （PPP） and Zn1-xAgxO nanoparticles through the sol-gel method. The presence of nanoinclusions PPP in Zno.gAgoa 0 matrix is found to be effective in improving the figure of merit （ZT） by the dual effects of an increase in the power factor consistent with the heterojunetion effect and a reduction in thermal conductivity. Zno.gAgo.10/0.1 wt% PPP exhibits a maximum figure of merit, i.e., ZT= 0.22.展开更多
We show that a current-carrying coherent electron conductor can be treated as an effective bosonic energy reservoir involving different types of electron–hole pair excitations.For weak electron–boson coupling,hybrid...We show that a current-carrying coherent electron conductor can be treated as an effective bosonic energy reservoir involving different types of electron–hole pair excitations.For weak electron–boson coupling,hybrid energy transport between nonequilibrium electrons and bosons can be described by a Landauer-like formula.This allows for unified account of a variety of heat transport problems in hybrid electron–boson systems.As applications,we study the non-reciprocal heat transport between electrons and bosons,thermoelectric current from a cold-spot,and electronic cooling of the bosons.Our unified framework provides an intuitive way of understanding hybrid energy transport between electrons and bosons in their weak coupling limit.It opens the way of nonequilibrium reservoir engineering for efficient energy control between different quasi-particles at the nanoscale.展开更多
Two-dimensional porous nanosheet heterostructure materials,which combine the advantages of both architecture and components,are expected to feature a significant photocatalytic performance toward CO_(2) conversion int...Two-dimensional porous nanosheet heterostructure materials,which combine the advantages of both architecture and components,are expected to feature a significant photocatalytic performance toward CO_(2) conversion into useful fuels.Herein,we provide a facile strategy for fabricating sulfur-doped C_(3)N_(4) porous nanosheets with embedded SnO_(2)-SnS_(2) nanojunctions(S-C_(3)N_(4)/SnO_(2)-SnS_(2))via liquid impregnation-pyrolysis and subsequent sulfidation treatment using a layered supramolecular structure as the precursor of C_(3)N_(4).A hexagonal layered supramolecular structure was first prepared as the precursor of C_(3)N_(4).Then Sn^(4+) ions were intercalated into the supramolecular interlayers through the liquid impregnation method.The subsequent annealing treatment in air simultaneously realized the fabrication and efficient exfoliation of layered C_(3)N_(4) porous nanosheets.Moreover,SnO_(2) nanoparticles were formed and embedded in situ in the porous C_(3)N_(4) nanosheets.In the following sulfidation process under a nitrogen atmosphere,sulfur powder can react with SnO_(2) nanoparticles to form SnO_(2)-SnS_(2) nanojunctions.As expected,the exfoliation of sulfur-doped C_(3)N_(4) porous nanosheets and ternary heterostructure construction could be simultaneously achieved in this work.Sulfur-doped C_(3)N_(4) porous nanosheets with embedded SnO_(2)-SnS_(2) nanojunctions featured abundant active sites,enhanced visible light absorption,and efficient interfacial charge transfer.As expected,the optimized S-C_(3)N_(4)/SnO_(2)-SnS_(2) achieved a much higher gas-phase photocatalytic CO_(2) reduction performance with high yields of CO(21.68μmol g^(−1)h^(−1))and CH_(4)(22.09μmol g^(−1)h^(−1))compared with the control C_(3)N_(4),C_(3)N_(4)/SnO_(2),and S-C_(3)N_(4)/SnS_(2) photocatalysts.The selectivity of CH_(4) reached 80.30%.Such a promising synthetic strategy can be expected to inspire the design of other robust C_(3)N_(4)-based porous nanosheet heterostructures for a broad range of applications.展开更多
Highly oriented multiple boron nanowire nanojunctions with unilateral feather- like morphology were first successfully prepared using a radio-frequency magnetron sputtering method. The branched boron nano-feathers alw...Highly oriented multiple boron nanowire nanojunctions with unilateral feather- like morphology were first successfully prepared using a radio-frequency magnetron sputtering method. The branched boron nano-feathers always nucleate and grow on the same sidewall of the stems, and align in parallel to form multiple T- and/or Y-type nanojunctions. The diameters of the branches and the stems are in the range of 20—40 and 60—80 nm, respectively. The thinner branches and thicker stems of the boron nanowires self-assembled into large-scale, highly ordered arrays on various substrates. During the formation and self-assembly of the arrays, no template or catalyst was needed. We believe that the approach presented here can be used to fabricate heterostructures with bottom-up assembly of a wide variety of one-dimensional nanostructures via the rational design of targets and the proper control of the experimental conditions.展开更多
Calcium signals determine, for example, smooth muscle contraction and changes in gene expression. How calcium signals select for these processes is enigmatic. We build on the "panjunctional sarcoplasmic reticulum...Calcium signals determine, for example, smooth muscle contraction and changes in gene expression. How calcium signals select for these processes is enigmatic. We build on the "panjunctional sarcoplasmic reticulum" hypothesis, describing our view that different calcium pumps and release channels, with different kinetics and affinities for calcium, are strategically positioned within nanojunctions of the SR and help demarcate their respective cytoplasmic nanodomains. SERCA2 b and Ry R1 are preferentially targeted to the sarcoplasmic reticulum(SR) proximal to the plasma membrane(PM), i.e., to the superficial buffer barrier formed by PM-SR nanojunctions, and support vasodilation. In marked contrast, SERCA2 a may be entirely restricted to the deep, perinuclear SR and may supply calcium to this sub-compartment in support of vasoconstriction. Ry R3 is also preferentially targeted to the perinuclear SR, where its clusters associate with lysosome-SR nanojunctions. The distribution of Ry R2 is more widespread and extends from this region to the wider cell. Therefore, perinuclear Ry R3 s most likely support the initiation of global calcium waves at L-SR junctions, which subsequently propagate by calcium-induced calcium release via Ry R2 in order to elicit contraction. Data also suggest that unique SERCA and Ry R are preferentially targeted to invaginations of the nuclear membrane. Site- and function-specific calcium signals may thus arise to modulate stimulus-response coupling and transcriptional cascades.展开更多
基金supported by National Key Research and Development Program of China(No.2016YFA0203100)the National Natural Science Foundation of China(Nos.21537004,21777169,and 21621064)the Beijing Municipal Natural Science Foundation(No.8202046)。
文摘The construction of heterojunction photocatalysts for efficiently utilizing solar energy has attracted considerable attention to solve the energy crisis and reduce environmental pollution.In this study,we use the energy released from an easily-occurred exothermic chemical reaction to serve as the drive force to trigger the formation of Cd S and C_(3)N_(4) nanocomposites which are successfully fabricated with cadmium nitrate and thiourea without addition of any solvents and protection of inert gas at initial temperature,a little higher than the melting point of thiourea.The as-prepared Cd S/C_(3)N_(4) materials exhibit high efficiency for photocatalytic hydrogen evolution reaction(HER)with the HER rate as high as 15,866μmol/(g·hr)under visible light irradiation(λ>420 nm),which is 89 and 9 times those of pristine C_(3)N_(4) and Cd S,respectively.Also,the apparent quantum efficiency(AQE)of Cd S/C_(3)N_(4)–1:2–200–2(Cd S/C_(3)N_(4)–1:2–200–2 means the ratio of Cd to S is 1:2 and the reaction temperature is set at 200℃ for two hours)reaches 3.25%atλ=420±15 nm.After irradiated for more than 24 hr,the HER efficiencies of Cd S/C_(3)N_(4) do not exhibit any attenuation.The DFT calculation suggests that the charge difference causes an internal electric field from C_(3)N_(4) pointing to Cd S,which can more effectively promote the transfer of photogenerated electrons from Cd S to C_(3)N_(4).Therefore,most HER should occur on C_(3)N_(4) surface where photogenerated electrons accumulate,which largely protects Cd S from photo-corrosion.
基金Supported by the National Natural Science Foundation of China under Grant Nos 51476095 and 51206103the Innovation Program of Shanghai Municipal Education Commission under Grant No 13YZ128the Program for Professor of Special Appointment(Eastern Scholar) at Shanghai Institutions of Higher Learning
文摘Organic-inorganic nanojunctions can result in a selective scattering of charge carrier depending on their energy, which leads to a simultaneous increase in the Seebeck coefficient S and the power factor. In this work, the nanojunction is successfully employed at the organic-inorganic semiconductor interface of polyparaphenylene （PPP） and Zn1-xAgxO nanoparticles through the sol-gel method. The presence of nanoinclusions PPP in Zno.gAgoa 0 matrix is found to be effective in improving the figure of merit （ZT） by the dual effects of an increase in the power factor consistent with the heterojunetion effect and a reduction in thermal conductivity. Zno.gAgo.10/0.1 wt% PPP exhibits a maximum figure of merit, i.e., ZT= 0.22.
基金Project supported by the National Key Research and Development Program of China(Grant No.2017YFA0403501)the National Natural Science Foundation of China(Grant No.21873033)the Program for HUST Academic Frontier Youth Team。
文摘We show that a current-carrying coherent electron conductor can be treated as an effective bosonic energy reservoir involving different types of electron–hole pair excitations.For weak electron–boson coupling,hybrid energy transport between nonequilibrium electrons and bosons can be described by a Landauer-like formula.This allows for unified account of a variety of heat transport problems in hybrid electron–boson systems.As applications,we study the non-reciprocal heat transport between electrons and bosons,thermoelectric current from a cold-spot,and electronic cooling of the bosons.Our unified framework provides an intuitive way of understanding hybrid energy transport between electrons and bosons in their weak coupling limit.It opens the way of nonequilibrium reservoir engineering for efficient energy control between different quasi-particles at the nanoscale.
基金supported by the National Natural Science Foundation of China(22072037 and 51772079)the Natural Science Foundation of Heilongjiang Province of China(LH2020B018)。
文摘Two-dimensional porous nanosheet heterostructure materials,which combine the advantages of both architecture and components,are expected to feature a significant photocatalytic performance toward CO_(2) conversion into useful fuels.Herein,we provide a facile strategy for fabricating sulfur-doped C_(3)N_(4) porous nanosheets with embedded SnO_(2)-SnS_(2) nanojunctions(S-C_(3)N_(4)/SnO_(2)-SnS_(2))via liquid impregnation-pyrolysis and subsequent sulfidation treatment using a layered supramolecular structure as the precursor of C_(3)N_(4).A hexagonal layered supramolecular structure was first prepared as the precursor of C_(3)N_(4).Then Sn^(4+) ions were intercalated into the supramolecular interlayers through the liquid impregnation method.The subsequent annealing treatment in air simultaneously realized the fabrication and efficient exfoliation of layered C_(3)N_(4) porous nanosheets.Moreover,SnO_(2) nanoparticles were formed and embedded in situ in the porous C_(3)N_(4) nanosheets.In the following sulfidation process under a nitrogen atmosphere,sulfur powder can react with SnO_(2) nanoparticles to form SnO_(2)-SnS_(2) nanojunctions.As expected,the exfoliation of sulfur-doped C_(3)N_(4) porous nanosheets and ternary heterostructure construction could be simultaneously achieved in this work.Sulfur-doped C_(3)N_(4) porous nanosheets with embedded SnO_(2)-SnS_(2) nanojunctions featured abundant active sites,enhanced visible light absorption,and efficient interfacial charge transfer.As expected,the optimized S-C_(3)N_(4)/SnO_(2)-SnS_(2) achieved a much higher gas-phase photocatalytic CO_(2) reduction performance with high yields of CO(21.68μmol g^(−1)h^(−1))and CH_(4)(22.09μmol g^(−1)h^(−1))compared with the control C_(3)N_(4),C_(3)N_(4)/SnO_(2),and S-C_(3)N_(4)/SnS_(2) photocatalysts.The selectivity of CH_(4) reached 80.30%.Such a promising synthetic strategy can be expected to inspire the design of other robust C_(3)N_(4)-based porous nanosheet heterostructures for a broad range of applications.
基金This work was partly supported by the National Natural Science Foundation of China(Grant No.10374078).
文摘Highly oriented multiple boron nanowire nanojunctions with unilateral feather- like morphology were first successfully prepared using a radio-frequency magnetron sputtering method. The branched boron nano-feathers always nucleate and grow on the same sidewall of the stems, and align in parallel to form multiple T- and/or Y-type nanojunctions. The diameters of the branches and the stems are in the range of 20—40 and 60—80 nm, respectively. The thinner branches and thicker stems of the boron nanowires self-assembled into large-scale, highly ordered arrays on various substrates. During the formation and self-assembly of the arrays, no template or catalyst was needed. We believe that the approach presented here can be used to fabricate heterostructures with bottom-up assembly of a wide variety of one-dimensional nanostructures via the rational design of targets and the proper control of the experimental conditions.
基金supported by the British Heart Foundation(29885)
文摘Calcium signals determine, for example, smooth muscle contraction and changes in gene expression. How calcium signals select for these processes is enigmatic. We build on the "panjunctional sarcoplasmic reticulum" hypothesis, describing our view that different calcium pumps and release channels, with different kinetics and affinities for calcium, are strategically positioned within nanojunctions of the SR and help demarcate their respective cytoplasmic nanodomains. SERCA2 b and Ry R1 are preferentially targeted to the sarcoplasmic reticulum(SR) proximal to the plasma membrane(PM), i.e., to the superficial buffer barrier formed by PM-SR nanojunctions, and support vasodilation. In marked contrast, SERCA2 a may be entirely restricted to the deep, perinuclear SR and may supply calcium to this sub-compartment in support of vasoconstriction. Ry R3 is also preferentially targeted to the perinuclear SR, where its clusters associate with lysosome-SR nanojunctions. The distribution of Ry R2 is more widespread and extends from this region to the wider cell. Therefore, perinuclear Ry R3 s most likely support the initiation of global calcium waves at L-SR junctions, which subsequently propagate by calcium-induced calcium release via Ry R2 in order to elicit contraction. Data also suggest that unique SERCA and Ry R are preferentially targeted to invaginations of the nuclear membrane. Site- and function-specific calcium signals may thus arise to modulate stimulus-response coupling and transcriptional cascades.
