A bound state formalism derived from a fermion-boson symmetric Lagrangian has been used to calculate the nucleon masses, the charge neutrality of the neutron, the magnetic moments and the electromagnetic form factor r...A bound state formalism derived from a fermion-boson symmetric Lagrangian has been used to calculate the nucleon masses, the charge neutrality of the neutron, the magnetic moments and the electromagnetic form factor ratios μpGEp/GMpand μnGEn/GMn. A quantitative description is obtained, assuming a mixing of a scalar bound state of 3(f f¯)fstructure with its corresponding vector (f f¯)fstate (f indicating massless elementary fermions). Only a few parameters are needed, mainly fixed by energy and momentum conservation. The nucleon stability is explained by an extra binding in the confinement potential, negative for electric and positive for magnetic binding of the proton, and opposite for the neutron. The stronger electric extra binding of the proton allows a decay of the neutron to proton and electron.展开更多
The massive vector bosons Z o, W ± and the scalar Higgs-boson H o assumed in weak interaction theory, but also the six quarks required in strong interactions are well understood in an alternative quantum field th...The massive vector bosons Z o, W ± and the scalar Higgs-boson H o assumed in weak interaction theory, but also the six quarks required in strong interactions are well understood in an alternative quantum field theory of fermions and bosons: Z o and W ± as well as all quark-antiquark states (here only the tt¯state is discussed) are described by bound states with scalar coupling between their massless constituents and have a structure similar to leptons. However, the scalar Higgs-boson H o corresponds to a state with vector coupling between the elementary constituents. Similar scalar states are expected also in the mass region of the mesons ω (0.782 GeV) - Υ ( 9.46 GeV). The underlying calculations can be run on line using the Web-address https://h2909473.stratoserver.net.展开更多
Both, the dilemma to find a quantum field theory consistent with Einstein’s law of relativity and the problem to describe existing particles as bound states of matter has been solved by calculating bound state matrix...Both, the dilemma to find a quantum field theory consistent with Einstein’s law of relativity and the problem to describe existing particles as bound states of matter has been solved by calculating bound state matrix elements from a dual fermion-boson Lagrangian. In this formalism, the fermion binding energies are compensated by boson energies, indicating that particles can be generated out of the vacuum. This yields quantitative solutions for various mesons ω (0.78 GeV) - Υ (9.46 GeV) and all leptons e, μ and τ, with uncertainties in the extracted properties of less than 1‰. For transparency, a Web-page with the address htpps://h2909473.stratoserver.net has been constructed, where all calculations can be run on line and also the underlying fortran source code can be inspected.展开更多
The direct one-step separation of polymer-grade C_(2)H_(4) from complex light hydrocarbon mixtures has high industrial significance but is very challenging.Herein,an ethylene-adsorption-weakening strategy is applied f...The direct one-step separation of polymer-grade C_(2)H_(4) from complex light hydrocarbon mixtures has high industrial significance but is very challenging.Herein,an ethylene-adsorption-weakening strategy is applied for precise regulation of the pore geometry of four tailor-made metal–organic frameworks(MOFs)with pillar-layered structures,dubbed TYUT-10/11/12/13.Based on its pore geometry design and functional group regulation,TYUT-12 exhibits exceptional selective adsorption selectivity toward C_(3)H_(8),C_(3)H_(6),C_(2)H_(6),C_(2)H_(2),and CO_(2) over C_(2)H_(4);its C_(2)H_(6)/C_(2)H_(4) adsorption selectivity reaches 4.56,surpassing the record value of 4.4 by Fe_(2)(O_(2))(dobdc)(dobdc^(4-)=2,5-dioxido-1,4-benzenedicarboxylate).The weak p–p stacking binding affinity toward C_(2)H_(4) in TYUT-12 is clearly demonstrated through a combination of neutron powder diffraction measurements and theoretical calculations.Breakthrough experiments demonstrate that C_(2)H_(4) can be directly obtained from binary,ternary,quaternary,and six-component light hydrocarbon mixtures with over 99.95%purity.展开更多
The ultrafast carrier relaxation processes in CdTe quantum dots are investigated by femtosecond fluorescence upconversion spectroscopy.Photo-excited hole relaxing to the edge of the forbidden gap takes a maximal time ...The ultrafast carrier relaxation processes in CdTe quantum dots are investigated by femtosecond fluorescence upconversion spectroscopy.Photo-excited hole relaxing to the edge of the forbidden gap takes a maximal time of ～ 1.6 ps with exciting at 400 nm,depending on the state of the photo-excited hole.The shallow trapped states and deep trap states in the forbidden gap are confirmed for CdTe quantum dots.In addition,Auger relaxation of trapped carriers is observed to occur with a time constant of ～ 5 ps.A schematic model of photodynamics is established based on the results of the spectroscopy studies.Our work demonstrates that femtosecond fluorescence up-conversion spectroscopy is a suitable and effective tool in studying the transportation and conversion dynamics of photon energy in a nanosystem.展开更多
Upconversion nanosensitizers have been widely considered to have important applications in the treatment of major diseases such as tumors and the utilization of solar energy.Majority of the efforts so far have been fo...Upconversion nanosensitizers have been widely considered to have important applications in the treatment of major diseases such as tumors and the utilization of solar energy.Majority of the efforts so far have been focused on improving the efficiency of energy transfer(ET)between upconversion nanoparticles(UCNPs)and the anchored sensitizers with premise that high ET efficiency will lead to high acceptor efficacy.This premise is,however,proved by our current work to be invalid for commonly used load.Interaction between adjacent sensitizing molecules was found to be critical which undermines the amount of excited monomer sensitizers and thus fades the efficacy.Here NaYF_(4):Yb^(3+),Er^(3+)UCNPs and rose bengal(RB)photosensitizer molecules were used as the model energy donors and acceptors,respectively.Contrary to monotonous increase of the ET efficiency from UCNPs to RB species with increasing RB loading,acceptor efficacy characterized by the reactive oxygen species,as well as the RB fluorescence,exhibits bizarre dependence on the RB loading.The underlying mechanism was well studied by the steady-state and time-resolved spectroscopy of a series of samples.RB aggregates are believed to be responsible for the severe deviation between the ET efficiency and acceptor efficacy.The conclusion was validated by in vitro test where the photodynamic therapy with the most monomer RB in UCNPs-RB nanosensitizers kills 35.8%more cells than that with the highest RB loading.This understanding sheds light on construction of new ET based nanosystems for broad applications,such as medicine,solar energy utilization and optical storage.展开更多
The removal of trace propyne(C_(3)H_(4))from propyne/propylene(C_(3)H_(4)/C_(3)H_(6))mixtures is a technical and challenging task during the production of polymer-grade propylene in view of their very similar size and...The removal of trace propyne(C_(3)H_(4))from propyne/propylene(C_(3)H_(4)/C_(3)H_(6))mixtures is a technical and challenging task during the production of polymer-grade propylene in view of their very similar size and physical properties.While some progress has been made,it is still very challenging to use some highly stable and commercially available porous materials via an energy-efficient adsorptive separation process.Herein,we report the ultrafine tuning of the pore apertures in type-A zeolites for the highly efficient removal of trace amounts of C_(3)H_(4)from C_(3)H_(4)/C_(3)H_(6)mixtures.The resulting ion-exchanged zeolite 5 A exhibits a large C_(3)H_(4)adsorption capacity(2.3 mmol g^(-1)under 10^(-4)MPa)and high C_(3)H_(4)/C_(3)H_(6)selectivity at room temperature,which were mainly attributed to the ultrafine-tuned pore size that selectively blocks C_(3)H_(6)molecules,while maintaining the stro ng adsorption of C_(3)H_(4)at low pressure region.High purity of C_(3)H_(6)(>99.9999%)can be directly obtained on this material under ambient conditions,as demonstrated by the experimental breakthrough curves obtained for both 1/99 and 0.1/99.9(V V)C_(3)H_(4)/C_(3)H_(6) mixtures.展开更多
Typically, a Lewis acid and a Lewis base can react with each other and form a classical Lewis adduct. The neutralization reaction can however be prevented by ligating the acid and base with bulky substituents and the ...Typically, a Lewis acid and a Lewis base can react with each other and form a classical Lewis adduct. The neutralization reaction can however be prevented by ligating the acid and base with bulky substituents and the resulting complex is known as a "frustrated Lewis pair"(FLP). Since the Lewis acid and base reactivity remains in the formed complex, FLPs can display interesting chemical activities, with promising applications in catalysis. For example, FLPs were shown to function as the first metal-free catalyst for molecular hydrogen activation. This, and other recent applications of FLPs, have opened a new thriving research field. In this short-review, we recapitulate the computational and experimental studies of the H_2 activation by FLPs. We discuss the thus-far uncovered mechanistic aspects, including pre-organization of FLPs,the reaction paths for the activation, the polarization of He H bond and other factors affecting the reactivity. We aim to provide a rather complete mechanistic picture of the H_2 activation by FLPs, which has been under debate for decades since the first discovery of FLPs. This review is meant as a starting point for future studies and a guideline for industrial applications.展开更多
The solid oxide electrolytic cell(SOEC)is one of the most promising energy conversion and storage devices,which could convert CO_(2) to CO with high Faradaic efficiency and production rate.However,the lack of active a...The solid oxide electrolytic cell(SOEC)is one of the most promising energy conversion and storage devices,which could convert CO_(2) to CO with high Faradaic efficiency and production rate.However,the lack of active and stable cathode materials impedes their practical applications.Here we focus on the promising perovskite oxide cathode material Sr_(2)Fe_(1.5)Mo_(0.5)O_(6)-σ,with the aim of understanding how A-atom stoichiometry and catalytic performance are linked.We find that increasing the strontium content in the perovskite improves the chemisorption of CO_(2) on its surface,forming a SrCO_(3) phase.This hinders the charge transfer and oxygen exchange processes.Simulta-neously,strontoium segregation to the cathode surface facilitates coking of the surface during CO_(2) electrolysis,which poisons the electrode.Consequently,a small number of Sr deficiencies are optimal for both electrochemical performance and long-term stability.Our results provide new insights for designing high-performance CO_(2) electrolysis cathode materials.展开更多
Industrial purification processes for ethylene from steam pyrolysis or cracking gases generally employ multiple energy-intensive steps to remove C_(2)H_(2),C_(2)H_(6),CO_(2),and C_(3) hydrocarbons.Designing multifunct...Industrial purification processes for ethylene from steam pyrolysis or cracking gases generally employ multiple energy-intensive steps to remove C_(2)H_(2),C_(2)H_(6),CO_(2),and C_(3) hydrocarbons.Designing multifunctional molecular separators that integrate multiple structural characteristics capable of removing several impurities simultaneously is highly desired but not yet realized.Here,we address this challenge using a custom-designed multifunctional,and industry-compatible ultramicroporous crystalline physisorbent(CALF-20)to purify C_(2)H_(4) from a seven-component cracking gas mixture(C_(2)H_(4),C_(2)H_(2),C_(2)H_(6),CO_(2),C_(3)H_(4),C_(3)H_(6),and C_(3)H8)by one-step separation with remarkable performance.Verified by breakthrough experiments,C_(2)H_(4)(>99.99%)can be recovered not only from binary C_(2)H_(6)/C_(2)H_(4)(50/50),ternary C_(2)H_(2)/C_(2)H_(4)/C_(2)H_(6)(33/33/33),and quaternary C_(2)H_(2)/C_(2)H_(4)/C_(2)H_(6)/CO_(2)(25/25/25/25)mixtures,but also from a typical seven-component gas cracking mixture of C_(2)H_(2)/C_(2)H_(4)/C_(2)H_(6)/CO_(2)/C_(3)H_(4)/C_(3)H_(6)/C_(3)H8(0.6/62/10/0.3/0.6/26/0.5),even at the high humidity of 74%.Notably,CALF-20 can be easily produced on the kilogram scale,showing great commercial application potential.Together with its framework flexibility and appropriate pore geometry,CALF-20 exhibits a sorbent-sorbate induced-fit behavior strengthening multiple specific recognition sites for the corresponding vips,validated by single-crystal X-ray diffraction study and molecular modeling.This work is the first example of using a single physisorbent to purify C_(2)H_(4) from a seven-component cracking gas mixture and opens an avenue to address complicated hydrocarbon mixture separation challenges.展开更多
Direct separation of Xe and Kr from air or used nuclear fuel(UNF)off-gas by means of porous adsorbents is of industrial importance but is a very challenging task.In this work,we show a robust metal-organic framework(M...Direct separation of Xe and Kr from air or used nuclear fuel(UNF)off-gas by means of porous adsorbents is of industrial importance but is a very challenging task.In this work,we show a robust metal-organic framework(MOF),namely ECUT-60,which renders not only high chemical stability,but also unique structure with multiple traps.This leads to the ultrahigh Xe adsorption capacity,exceeding most reported porous materials.Impressively,this MOF also enables high selectivity of Xe over Kr,CO2,O2,and N2,leading to the high-performance separation for trace quantitites of Xe/Kr from a simulated UNF reprocessing off-gas.The separation capability has been demonstrated by using dynamic breakthrough experiments,giving the record Xe uptake up to 70.4 mmol/kg and the production of 19.7 mmol/kg pure Xe.Consequently,ECUT-60 has promising potential in direct production of Xe from UNF off-gas or air.The separation mechanism,as unveiled by theoretical calculation,is attributed to the multiple traps in ECUT-60 that affords rigid restrict for Xe atom via van der Waals force.展开更多
The efficient separation of acetylene(C_(2)H_(2))from carbon dioxide(CO_(2))and CnH_(4)(n=1 and 2)to manufacture high purity C_(2)H_(2)and recover other light hydrocarbons is technologically important,while posing sig...The efficient separation of acetylene(C_(2)H_(2))from carbon dioxide(CO_(2))and CnH_(4)(n=1 and 2)to manufacture high purity C_(2)H_(2)and recover other light hydrocarbons is technologically important,while posing significant challenges.Herein,we reported a new TiF62−anion(TIFSIX)pillared metal-organic framework(MOF)ZNU-5(ZNU=Zhejiang Normal University)with ultramicropores for highly selective C_(2)H_(2)capture with low adsorption heat through gate opening based molecular sieving effect.ZNU-5 takes up a large amount of C_(2)H_(2)(128.6 cm^(3)/g)at 1.0 bar and 298 K but excludes CO_(2),CH_(4),and C_(2)H_(4).Such high capacity has never been realized in MOFs with molecular sieving.The breakthrough experiments further confirmed the highly selective C_(2)H_(2)separation performance from multi-component gas mixtures.3.3,2.8,and 2.2 mmol/g of C_(2)H_(2)is captured at ZNU-5 from equimolar C_(2)H_(2)/CO_(2),C_(2)H_(2)/CO_(2)/CH_(4),and C_(2)H_(2)/CO_(2)/CH_(4)/C_(2)H_(4)mixtures,respectively.Furthermore,2.6,2.0,and 1.5 mmol/g of>98%purity C_(2)H_(2)can be recycled from the desorption process.Combining high working capacity,low adsorption heat,as well as good recyclability,ZNU-5 is promising for C_(2)H_(2)purification.展开更多
Trivalent rare earth ions(Ln3+)have the unique elec-tronic configurations[Xe]4fn(n=0-14)and numerous energy levels,which endow rare earth luminescent mate-rials with many fascinating optical properties over a broad sp...Trivalent rare earth ions(Ln3+)have the unique elec-tronic configurations[Xe]4fn(n=0-14)and numerous energy levels,which endow rare earth luminescent mate-rials with many fascinating optical properties over a broad spectral region ranging from the ultraviolet(UV)to the near infrared(NIR);these include tunable atomic-like excitation/emission spectra,large Stokes/anti-Stokes shifts,long luminescent lifetimes,and excellent photostability1-4.展开更多
Developing advanced porous materials possessing both a high storage capacity and selectivity for acetylene(C_(2)H_(2))remains challenging but a sought-after endeavor.Herein we show a strategy involving synergic combin...Developing advanced porous materials possessing both a high storage capacity and selectivity for acetylene(C_(2)H_(2))remains challenging but a sought-after endeavor.Herein we show a strategy involving synergic combination of spatial confinement and commensurate stacking for enhanced C_(2)H_(2)storage and capture via maximizing the host–vip and vip–vip interactions.Two ultramicroporous metal-organic frameworks(MOFs),MIL-160 and MOF-303 are elaborately constructed to exhibit ultrahigh C_(2)H_(2)uptakes of 235 and 195 cm^(3)·g^(−1),respectively,due to the confinement effect of the suitable pore sizes and periodically dispersed molecular recognition sites.Specially,C_(2)H_(2)capacity of MIL-160 sets a new benchmark for C_(2)H_(2)storage.The exceptional separation performances of two materials for C_(2)H_(2)over both CO_(2)and ethylene(C_(2)H_(4)),which is rarely observed,outperform most of the benchmark materials for C_(2)H_(2)capture.We scrutinized the origins of ultrahigh C_(2)H_(2)loading in the confined channels via theoretical investigations.The superior separation efficiency for C_(2)H_(2)/CO_(2)and C_(2)H_(2)/C_(2)H_(4)mixtures with unprecedented C_(2)H_(2)trapping capacity(>200 L·kg^(−1))was further demonstrated by dynamic breakthrough experiments.展开更多
Separations of mixtures in fixed-bed adsorbers are influenced by factors such as(1)selectivity of adsorption,Sads,(2)diffusional time constants,Đi/rc 2,and(3)diffusion selectivity,Đ1/Đ2.In synergistic separations,intr...Separations of mixtures in fixed-bed adsorbers are influenced by factors such as(1)selectivity of adsorption,Sads,(2)diffusional time constants,Đi/rc 2,and(3)diffusion selectivity,Đ1/Đ2.In synergistic separations,intracrystalline diffusion of vip molecules serves to enhance the selectivities dictated by thermodynamics of mixture adsorption.In antisynergistic separations,intracrystalline diffusion serves to reverse the hierarchy of selectivities dictated by adsorption equilibrium.For both scenarios,the productivities of the desired product in fixed-bed operations are crucially dependent on diffusional time constants,Đi/rc 2;these need to be sufficiently low in order for diffusional influences to be effective.Also,the ratioĐ1/Đ2 should be large enough for manifestation of synergistic or antisynergistic influence.Both synergistic and antisynergistic separations have two common,distinguishing characteristics.Firstly,for transient uptake within crystals,the more mobile component attains supraequilibrium loadings during the initial stages of the transience.Such overshoots,signifying uphill diffusion,are engendered by the cross-coefficientsΓij(i≠j)of thermodynamic correction factors.Secondly,the component molar loadings,plotted in composition space,follow serpentine equilibration paths.If cross-coefficients are neglected,no overshoots in the loadings of the more mobile component are experienced,and the component loadings follow monotonous equilibration paths.The important takeaway message is that the modeling of mixture separations in fixed-bed adsorbers requires the use of the Maxwell−Stefan equations describing mixture diffusion employing chemical potential gradients as driving forces.展开更多
Internal hydroxyl impurity is known as one of the main detrimental factors affecting the upconversion(UC)efficiency of upconversion luminescence(UCL)nanomaterials.Different from surface"ligand-related emission qu...Internal hydroxyl impurity is known as one of the main detrimental factors affecting the upconversion(UC)efficiency of upconversion luminescence(UCL)nanomaterials.Different from surface"ligand-related emission quenching which can be effectively diminished by,e.g.,core"shell structure,internal hydroxyl is easy to be introduced in synthesis but difficult to be quantified and controlled.Therefore,it becomes an obstacle to fully understand the relevant UC mechanism and improve UC efficiency of nanomaterials.Here we report a progress in quantifying and large-range adjustment of the internal hydroxyl impurity in NaYF4 nanocrystals.By combining the spectroscopy study and model simulation,we have quantitatively unraveled the microscopic in teractions underlying UCL que nching between internal hydroxyl and the sensitizers and activators,respectively.Furthermore,the internal hydroxyl-involved UC dynamical process is interpreted with a vivid concept of"Survivor effect" i.e.;the shorter the migration path of an excited state,the larger the possibility of its surviving from hydroxyl-induced quenchi ng.Apart from the consist ent experimental results,this concept can be further evidenced by Monte Carlo simulation,which monitors the variation of energy migration step distribution before and after the hydroxyl introduction.The new quantitative insights shall promote the construction of highly efficient UC materials.展开更多
Separation of propane from natural gas is of great importance to industry.However,in light of size-based separation,there still lacks effective method to directly separate propane from natural gas,due to the comparabl...Separation of propane from natural gas is of great importance to industry.However,in light of size-based separation,there still lacks effective method to directly separate propane from natural gas,due to the comparable physical properties for these light alkanes(C1–C4)and the middle size of propane.In this work,we found that a new Th-metal-organic framework(MOF)could be an ideal solution for this issue.The Th-MOF takes UiO-66-type structure,but with the pocket sealed by six-fold imide groups;this not only precisely reduces the size of pocket to exactly match propane,but also enhances the host–vip interactions through multiple(C)H(^(δ+))∙∙∙(^(δ−))O(C)interactions.As a result,highly selective adsorption of propane over methane,ethane,and butane was observed,implying unique middle-size separation.The actual separation was confirmed by breakthrough experiments of simulated natural gas,confirming its superior application in direct separation of propane from natural gas.The separation mechanism,as unveiled by both theoretical calculation and comparative experiments,is due to the six-fold imide-sealed pocket that could effectively distinguish propane from other light alkanes through both size effect and host–vip interactions.展开更多
Upconversion is a process in which one photon is emitted upon absorption of several photons of lower energy. Potential applications include super resolution spectroscopy, high density data storage, anti-counterfeiting...Upconversion is a process in which one photon is emitted upon absorption of several photons of lower energy. Potential applications include super resolution spectroscopy, high density data storage, anti-counterfeiting and biological imaging and photo-induced therapy. Upconversion luminescence dynamics has long been believed to be determined solely by the emitting ions and their interactions with neighboring sensitizing ions. Recent research shows that this does not hold for nanostructures.The luminescence time behavior in the nanomaterials is confirmed seriously affected by the migration process of the excitation energy. This new fundamental insight is significant for the design of functional upconversion nanostructures. In this paper we review relevant theoretical and spectroscopic results and demonstrate how to tune the rise and decay profile of upconversion luminescence based on energy migration path modulation.展开更多
文摘A bound state formalism derived from a fermion-boson symmetric Lagrangian has been used to calculate the nucleon masses, the charge neutrality of the neutron, the magnetic moments and the electromagnetic form factor ratios μpGEp/GMpand μnGEn/GMn. A quantitative description is obtained, assuming a mixing of a scalar bound state of 3(f f¯)fstructure with its corresponding vector (f f¯)fstate (f indicating massless elementary fermions). Only a few parameters are needed, mainly fixed by energy and momentum conservation. The nucleon stability is explained by an extra binding in the confinement potential, negative for electric and positive for magnetic binding of the proton, and opposite for the neutron. The stronger electric extra binding of the proton allows a decay of the neutron to proton and electron.
文摘The massive vector bosons Z o, W ± and the scalar Higgs-boson H o assumed in weak interaction theory, but also the six quarks required in strong interactions are well understood in an alternative quantum field theory of fermions and bosons: Z o and W ± as well as all quark-antiquark states (here only the tt¯state is discussed) are described by bound states with scalar coupling between their massless constituents and have a structure similar to leptons. However, the scalar Higgs-boson H o corresponds to a state with vector coupling between the elementary constituents. Similar scalar states are expected also in the mass region of the mesons ω (0.782 GeV) - Υ ( 9.46 GeV). The underlying calculations can be run on line using the Web-address https://h2909473.stratoserver.net.
文摘Both, the dilemma to find a quantum field theory consistent with Einstein’s law of relativity and the problem to describe existing particles as bound states of matter has been solved by calculating bound state matrix elements from a dual fermion-boson Lagrangian. In this formalism, the fermion binding energies are compensated by boson energies, indicating that particles can be generated out of the vacuum. This yields quantitative solutions for various mesons ω (0.78 GeV) - Υ (9.46 GeV) and all leptons e, μ and τ, with uncertainties in the extracted properties of less than 1‰. For transparency, a Web-page with the address htpps://h2909473.stratoserver.net has been constructed, where all calculations can be run on line and also the underlying fortran source code can be inspected.
基金supported by National Key Research and Development Program of China(2022YFB3806800)National Natural Science Foundation of China(22278288 and 22090062).
文摘The direct one-step separation of polymer-grade C_(2)H_(4) from complex light hydrocarbon mixtures has high industrial significance but is very challenging.Herein,an ethylene-adsorption-weakening strategy is applied for precise regulation of the pore geometry of four tailor-made metal–organic frameworks(MOFs)with pillar-layered structures,dubbed TYUT-10/11/12/13.Based on its pore geometry design and functional group regulation,TYUT-12 exhibits exceptional selective adsorption selectivity toward C_(3)H_(8),C_(3)H_(6),C_(2)H_(6),C_(2)H_(2),and CO_(2) over C_(2)H_(4);its C_(2)H_(6)/C_(2)H_(4) adsorption selectivity reaches 4.56,surpassing the record value of 4.4 by Fe_(2)(O_(2))(dobdc)(dobdc^(4-)=2,5-dioxido-1,4-benzenedicarboxylate).The weak p–p stacking binding affinity toward C_(2)H_(4) in TYUT-12 is clearly demonstrated through a combination of neutron powder diffraction measurements and theoretical calculations.Breakthrough experiments demonstrate that C_(2)H_(4) can be directly obtained from binary,ternary,quaternary,and six-component light hydrocarbon mixtures with over 99.95%purity.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 11074003 and 20973001)the Key Program of Educational Commission of Anhui Province of China (Grant No. KJ2010A132)
文摘The ultrafast carrier relaxation processes in CdTe quantum dots are investigated by femtosecond fluorescence upconversion spectroscopy.Photo-excited hole relaxing to the edge of the forbidden gap takes a maximal time of ～ 1.6 ps with exciting at 400 nm,depending on the state of the photo-excited hole.The shallow trapped states and deep trap states in the forbidden gap are confirmed for CdTe quantum dots.In addition,Auger relaxation of trapped carriers is observed to occur with a time constant of ～ 5 ps.A schematic model of photodynamics is established based on the results of the spectroscopy studies.Our work demonstrates that femtosecond fluorescence up-conversion spectroscopy is a suitable and effective tool in studying the transportation and conversion dynamics of photon energy in a nanosystem.
基金Project supported by the National Natural Science Foundation of China(51972052,11604043,11604044,51772122,11674316)Scientific and Technological Developing Scheme of Jilin Province(20190201243JC)+5 种基金Science and Technology Research Project of Education Department of Jilin Province(JJKH20211275KJ)the Fundamental Research Funds for the Central Universities(2412019FZ033)the 111 Project(B13013)Netherlands Organization for Scientific Research in the framework of the Fund New Chemical Innovation(731.015.206)EU H2020-MSCA-ITN-ETN Action program,ISPIC(675743)EU H2020-MSCA-RISE Action program,CANCER(777682)。
文摘Upconversion nanosensitizers have been widely considered to have important applications in the treatment of major diseases such as tumors and the utilization of solar energy.Majority of the efforts so far have been focused on improving the efficiency of energy transfer(ET)between upconversion nanoparticles(UCNPs)and the anchored sensitizers with premise that high ET efficiency will lead to high acceptor efficacy.This premise is,however,proved by our current work to be invalid for commonly used load.Interaction between adjacent sensitizing molecules was found to be critical which undermines the amount of excited monomer sensitizers and thus fades the efficacy.Here NaYF_(4):Yb^(3+),Er^(3+)UCNPs and rose bengal(RB)photosensitizer molecules were used as the model energy donors and acceptors,respectively.Contrary to monotonous increase of the ET efficiency from UCNPs to RB species with increasing RB loading,acceptor efficacy characterized by the reactive oxygen species,as well as the RB fluorescence,exhibits bizarre dependence on the RB loading.The underlying mechanism was well studied by the steady-state and time-resolved spectroscopy of a series of samples.RB aggregates are believed to be responsible for the severe deviation between the ET efficiency and acceptor efficacy.The conclusion was validated by in vitro test where the photodynamic therapy with the most monomer RB in UCNPs-RB nanosensitizers kills 35.8%more cells than that with the highest RB loading.This understanding sheds light on construction of new ET based nanosystems for broad applications,such as medicine,solar energy utilization and optical storage.
基金financial support from the National Natural Science Foundation of China(21922810,21908153,21908155)program of Innovative Talents of Higher Education Institutions of Shanxithe supported by Cultivate Scientific Research Excellence Programs of Higher Education Institutions in Shanxi(CSREP)。
文摘The removal of trace propyne(C_(3)H_(4))from propyne/propylene(C_(3)H_(4)/C_(3)H_(6))mixtures is a technical and challenging task during the production of polymer-grade propylene in view of their very similar size and physical properties.While some progress has been made,it is still very challenging to use some highly stable and commercially available porous materials via an energy-efficient adsorptive separation process.Herein,we report the ultrafine tuning of the pore apertures in type-A zeolites for the highly efficient removal of trace amounts of C_(3)H_(4)from C_(3)H_(4)/C_(3)H_(6)mixtures.The resulting ion-exchanged zeolite 5 A exhibits a large C_(3)H_(4)adsorption capacity(2.3 mmol g^(-1)under 10^(-4)MPa)and high C_(3)H_(4)/C_(3)H_(6)selectivity at room temperature,which were mainly attributed to the ultrafine-tuned pore size that selectively blocks C_(3)H_(6)molecules,while maintaining the stro ng adsorption of C_(3)H_(4)at low pressure region.High purity of C_(3)H_(6)(>99.9999%)can be directly obtained on this material under ambient conditions,as demonstrated by the experimental breakthrough curves obtained for both 1/99 and 0.1/99.9(V V)C_(3)H_(4)/C_(3)H_(6) mixtures.
文摘Typically, a Lewis acid and a Lewis base can react with each other and form a classical Lewis adduct. The neutralization reaction can however be prevented by ligating the acid and base with bulky substituents and the resulting complex is known as a "frustrated Lewis pair"(FLP). Since the Lewis acid and base reactivity remains in the formed complex, FLPs can display interesting chemical activities, with promising applications in catalysis. For example, FLPs were shown to function as the first metal-free catalyst for molecular hydrogen activation. This, and other recent applications of FLPs, have opened a new thriving research field. In this short-review, we recapitulate the computational and experimental studies of the H_2 activation by FLPs. We discuss the thus-far uncovered mechanistic aspects, including pre-organization of FLPs,the reaction paths for the activation, the polarization of He H bond and other factors affecting the reactivity. We aim to provide a rather complete mechanistic picture of the H_2 activation by FLPs, which has been under debate for decades since the first discovery of FLPs. This review is meant as a starting point for future studies and a guideline for industrial applications.
基金financially supported by the National Natural Science Foundation of China(No.21975163)Natural Science Foundation of Guangdong Province of China(2020A1515011165)Shenzhen Sci-ence and Technology Program(No.KQTD20190929173914967)and(No.JCYJ20220818100004009)。
文摘The solid oxide electrolytic cell(SOEC)is one of the most promising energy conversion and storage devices,which could convert CO_(2) to CO with high Faradaic efficiency and production rate.However,the lack of active and stable cathode materials impedes their practical applications.Here we focus on the promising perovskite oxide cathode material Sr_(2)Fe_(1.5)Mo_(0.5)O_(6)-σ,with the aim of understanding how A-atom stoichiometry and catalytic performance are linked.We find that increasing the strontium content in the perovskite improves the chemisorption of CO_(2) on its surface,forming a SrCO_(3) phase.This hinders the charge transfer and oxygen exchange processes.Simulta-neously,strontoium segregation to the cathode surface facilitates coking of the surface during CO_(2) electrolysis,which poisons the electrode.Consequently,a small number of Sr deficiencies are optimal for both electrochemical performance and long-term stability.Our results provide new insights for designing high-performance CO_(2) electrolysis cathode materials.
基金supported by the National Natural Science Foundation of China(grant nos.22201304,22178378,and 22127812)the Science Foundation of China University of Petroleum-Beijing(grant nos.2462021QNXZ011 and 2462022YXZZ007).
文摘Industrial purification processes for ethylene from steam pyrolysis or cracking gases generally employ multiple energy-intensive steps to remove C_(2)H_(2),C_(2)H_(6),CO_(2),and C_(3) hydrocarbons.Designing multifunctional molecular separators that integrate multiple structural characteristics capable of removing several impurities simultaneously is highly desired but not yet realized.Here,we address this challenge using a custom-designed multifunctional,and industry-compatible ultramicroporous crystalline physisorbent(CALF-20)to purify C_(2)H_(4) from a seven-component cracking gas mixture(C_(2)H_(4),C_(2)H_(2),C_(2)H_(6),CO_(2),C_(3)H_(4),C_(3)H_(6),and C_(3)H8)by one-step separation with remarkable performance.Verified by breakthrough experiments,C_(2)H_(4)(>99.99%)can be recovered not only from binary C_(2)H_(6)/C_(2)H_(4)(50/50),ternary C_(2)H_(2)/C_(2)H_(4)/C_(2)H_(6)(33/33/33),and quaternary C_(2)H_(2)/C_(2)H_(4)/C_(2)H_(6)/CO_(2)(25/25/25/25)mixtures,but also from a typical seven-component gas cracking mixture of C_(2)H_(2)/C_(2)H_(4)/C_(2)H_(6)/CO_(2)/C_(3)H_(4)/C_(3)H_(6)/C_(3)H8(0.6/62/10/0.3/0.6/26/0.5),even at the high humidity of 74%.Notably,CALF-20 can be easily produced on the kilogram scale,showing great commercial application potential.Together with its framework flexibility and appropriate pore geometry,CALF-20 exhibits a sorbent-sorbate induced-fit behavior strengthening multiple specific recognition sites for the corresponding vips,validated by single-crystal X-ray diffraction study and molecular modeling.This work is the first example of using a single physisorbent to purify C_(2)H_(4) from a seven-component cracking gas mixture and opens an avenue to address complicated hydrocarbon mixture separation challenges.
基金supported by the National Natural Science Foundations of China(21966002 and 21871047)the Natural Science Foundation of Jiangxi Province(20181ACB20003)+1 种基金the Training Program for Academic and Technical Leaders of Major Disciplines in Jiangxi Province(20194BCJ22010)the Graduate Innovation Project of East China University of Technology(DHYC-202023)。
文摘Direct separation of Xe and Kr from air or used nuclear fuel(UNF)off-gas by means of porous adsorbents is of industrial importance but is a very challenging task.In this work,we show a robust metal-organic framework(MOF),namely ECUT-60,which renders not only high chemical stability,but also unique structure with multiple traps.This leads to the ultrahigh Xe adsorption capacity,exceeding most reported porous materials.Impressively,this MOF also enables high selectivity of Xe over Kr,CO2,O2,and N2,leading to the high-performance separation for trace quantitites of Xe/Kr from a simulated UNF reprocessing off-gas.The separation capability has been demonstrated by using dynamic breakthrough experiments,giving the record Xe uptake up to 70.4 mmol/kg and the production of 19.7 mmol/kg pure Xe.Consequently,ECUT-60 has promising potential in direct production of Xe from UNF off-gas or air.The separation mechanism,as unveiled by theoretical calculation,is attributed to the multiple traps in ECUT-60 that affords rigid restrict for Xe atom via van der Waals force.
基金support by the National Natural Science Foundation of China(No.21908193)Jinhua Industrial Key Project(No.2021A22648)+2 种基金S.D.acknowledged the financial support by the National Natural Science Foundation of China(No.21871231)the Special Funds for Basic Scientific Research of Zhejiang University(Nos.2019QNA3010 and K20210335)support by the National Natural Science Foundation of China(No.22205207).
文摘The efficient separation of acetylene(C_(2)H_(2))from carbon dioxide(CO_(2))and CnH_(4)(n=1 and 2)to manufacture high purity C_(2)H_(2)and recover other light hydrocarbons is technologically important,while posing significant challenges.Herein,we reported a new TiF62−anion(TIFSIX)pillared metal-organic framework(MOF)ZNU-5(ZNU=Zhejiang Normal University)with ultramicropores for highly selective C_(2)H_(2)capture with low adsorption heat through gate opening based molecular sieving effect.ZNU-5 takes up a large amount of C_(2)H_(2)(128.6 cm^(3)/g)at 1.0 bar and 298 K but excludes CO_(2),CH_(4),and C_(2)H_(4).Such high capacity has never been realized in MOFs with molecular sieving.The breakthrough experiments further confirmed the highly selective C_(2)H_(2)separation performance from multi-component gas mixtures.3.3,2.8,and 2.2 mmol/g of C_(2)H_(2)is captured at ZNU-5 from equimolar C_(2)H_(2)/CO_(2),C_(2)H_(2)/CO_(2)/CH_(4),and C_(2)H_(2)/CO_(2)/CH_(4)/C_(2)H_(4)mixtures,respectively.Furthermore,2.6,2.0,and 1.5 mmol/g of>98%purity C_(2)H_(2)can be recycled from the desorption process.Combining high working capacity,low adsorption heat,as well as good recyclability,ZNU-5 is promising for C_(2)H_(2)purification.
文摘Trivalent rare earth ions(Ln3+)have the unique elec-tronic configurations[Xe]4fn(n=0-14)and numerous energy levels,which endow rare earth luminescent mate-rials with many fascinating optical properties over a broad spectral region ranging from the ultraviolet(UV)to the near infrared(NIR);these include tunable atomic-like excitation/emission spectra,large Stokes/anti-Stokes shifts,long luminescent lifetimes,and excellent photostability1-4.
基金the National Natural Science Foundation of China(No.21868002)Dean Project of Guangxi Key Laboratory of Petrochemical Resource Processing and Process Intensification Technology(No.2021Z010).
文摘Developing advanced porous materials possessing both a high storage capacity and selectivity for acetylene(C_(2)H_(2))remains challenging but a sought-after endeavor.Herein we show a strategy involving synergic combination of spatial confinement and commensurate stacking for enhanced C_(2)H_(2)storage and capture via maximizing the host–vip and vip–vip interactions.Two ultramicroporous metal-organic frameworks(MOFs),MIL-160 and MOF-303 are elaborately constructed to exhibit ultrahigh C_(2)H_(2)uptakes of 235 and 195 cm^(3)·g^(−1),respectively,due to the confinement effect of the suitable pore sizes and periodically dispersed molecular recognition sites.Specially,C_(2)H_(2)capacity of MIL-160 sets a new benchmark for C_(2)H_(2)storage.The exceptional separation performances of two materials for C_(2)H_(2)over both CO_(2)and ethylene(C_(2)H_(4)),which is rarely observed,outperform most of the benchmark materials for C_(2)H_(2)capture.We scrutinized the origins of ultrahigh C_(2)H_(2)loading in the confined channels via theoretical investigations.The superior separation efficiency for C_(2)H_(2)/CO_(2)and C_(2)H_(2)/C_(2)H_(4)mixtures with unprecedented C_(2)H_(2)trapping capacity(>200 L·kg^(−1))was further demonstrated by dynamic breakthrough experiments.
文摘Separations of mixtures in fixed-bed adsorbers are influenced by factors such as(1)selectivity of adsorption,Sads,(2)diffusional time constants,Đi/rc 2,and(3)diffusion selectivity,Đ1/Đ2.In synergistic separations,intracrystalline diffusion of vip molecules serves to enhance the selectivities dictated by thermodynamics of mixture adsorption.In antisynergistic separations,intracrystalline diffusion serves to reverse the hierarchy of selectivities dictated by adsorption equilibrium.For both scenarios,the productivities of the desired product in fixed-bed operations are crucially dependent on diffusional time constants,Đi/rc 2;these need to be sufficiently low in order for diffusional influences to be effective.Also,the ratioĐ1/Đ2 should be large enough for manifestation of synergistic or antisynergistic influence.Both synergistic and antisynergistic separations have two common,distinguishing characteristics.Firstly,for transient uptake within crystals,the more mobile component attains supraequilibrium loadings during the initial stages of the transience.Such overshoots,signifying uphill diffusion,are engendered by the cross-coefficientsΓij(i≠j)of thermodynamic correction factors.Secondly,the component molar loadings,plotted in composition space,follow serpentine equilibration paths.If cross-coefficients are neglected,no overshoots in the loadings of the more mobile component are experienced,and the component loadings follow monotonous equilibration paths.The important takeaway message is that the modeling of mixture separations in fixed-bed adsorbers requires the use of the Maxwell−Stefan equations describing mixture diffusion employing chemical potential gradients as driving forces.
基金Dutch Research Council(NWO)in the framework of the Fund New Chemical Innovation under grant number 731.015.206EU H2020-MSCA-ITN-ETN Action program,ISPIC,under grant number 675743+2 种基金EU H2020-MSCA-RISE Action program,CANCER,under grant number 777682Natural Science Foundation of China(11674316,62075217,11874355,and 11874354)Beijing Institute of Technology Research Fund Program for Young Scholars.Quantum yield measureme nt was con ducted in the lab of Professor S.A.Bonnet at Leiden University.
文摘Internal hydroxyl impurity is known as one of the main detrimental factors affecting the upconversion(UC)efficiency of upconversion luminescence(UCL)nanomaterials.Different from surface"ligand-related emission quenching which can be effectively diminished by,e.g.,core"shell structure,internal hydroxyl is easy to be introduced in synthesis but difficult to be quantified and controlled.Therefore,it becomes an obstacle to fully understand the relevant UC mechanism and improve UC efficiency of nanomaterials.Here we report a progress in quantifying and large-range adjustment of the internal hydroxyl impurity in NaYF4 nanocrystals.By combining the spectroscopy study and model simulation,we have quantitatively unraveled the microscopic in teractions underlying UCL que nching between internal hydroxyl and the sensitizers and activators,respectively.Furthermore,the internal hydroxyl-involved UC dynamical process is interpreted with a vivid concept of"Survivor effect" i.e.;the shorter the migration path of an excited state,the larger the possibility of its surviving from hydroxyl-induced quenchi ng.Apart from the consist ent experimental results,this concept can be further evidenced by Monte Carlo simulation,which monitors the variation of energy migration step distribution before and after the hydroxyl introduction.The new quantitative insights shall promote the construction of highly efficient UC materials.
基金Fund of Jiangxi Province Key Laboratory of Synthetic Chemistry(No.JXSC202007)the Foundation of Jiangxi Educational Committee(No.GJJ200734)+4 种基金the Doctoral Scientific Research Start-up Foundation of East China University of Technology(No.DHBK2018044)the National Natural Science Foundation of China(Nos.21966002 and 21871047)the Training Program for Academic and Technical Leaders of Major Disciplines in Jiangxi Province(No.20194BCJ22010)the Fuzhou Youth Leading Talent Project(No.2020ED64)the Provincial College Students Innovation and Entrepreneurship Training Program(No.S202110405026).
文摘Separation of propane from natural gas is of great importance to industry.However,in light of size-based separation,there still lacks effective method to directly separate propane from natural gas,due to the comparable physical properties for these light alkanes(C1–C4)and the middle size of propane.In this work,we found that a new Th-metal-organic framework(MOF)could be an ideal solution for this issue.The Th-MOF takes UiO-66-type structure,but with the pocket sealed by six-fold imide groups;this not only precisely reduces the size of pocket to exactly match propane,but also enhances the host–vip interactions through multiple(C)H(^(δ+))∙∙∙(^(δ−))O(C)interactions.As a result,highly selective adsorption of propane over methane,ethane,and butane was observed,implying unique middle-size separation.The actual separation was confirmed by breakthrough experiments of simulated natural gas,confirming its superior application in direct separation of propane from natural gas.The separation mechanism,as unveiled by both theoretical calculation and comparative experiments,is due to the six-fold imide-sealed pocket that could effectively distinguish propane from other light alkanes through both size effect and host–vip interactions.
基金supported by the European Union MSCA-ITN-ETN Action Program,Image-Guided Surgery and Personalised Postoperative Immunotherapy to Improving Cancer Outcome(ISPIC)(Grant No.675743)the Netherlands Organisation for Scientific Research in the framework of the Fund New Chemical Innovation(Grant No.731.015.206)+2 种基金the European COST Action(Grant No.CM1403)the Joint Research Program between CAS of China and the Royal Netherlands Academy of Arts and Sciences(KNAW)Innovation Project of State Key Laboratory of Luminescence and Applications of China
文摘Upconversion is a process in which one photon is emitted upon absorption of several photons of lower energy. Potential applications include super resolution spectroscopy, high density data storage, anti-counterfeiting and biological imaging and photo-induced therapy. Upconversion luminescence dynamics has long been believed to be determined solely by the emitting ions and their interactions with neighboring sensitizing ions. Recent research shows that this does not hold for nanostructures.The luminescence time behavior in the nanomaterials is confirmed seriously affected by the migration process of the excitation energy. This new fundamental insight is significant for the design of functional upconversion nanostructures. In this paper we review relevant theoretical and spectroscopic results and demonstrate how to tune the rise and decay profile of upconversion luminescence based on energy migration path modulation.
