NiO_(x)as a hole transport material for inverted perovskite solar cells has received great attention owing to its high transparency,low fabrication temperature,and superior stability.However,the mismatched energy leve...NiO_(x)as a hole transport material for inverted perovskite solar cells has received great attention owing to its high transparency,low fabrication temperature,and superior stability.However,the mismatched energy levels and possible redox reactions at the NiO_(x)/perovskite interface severely limit the performance of NiO_(x) based inverted perovskite solar cells.Herein,we introduce a p-type self-assembled monolayer between NiO_(x)and perovskite layers to modify the interface and block the undesirable redox reaction between perovskite and NiO_(x)The selfassembled monolayer molecules all contain phosphoric acid function groups,which can be anchored onto the NiOr surface and passivate the surface defect.Moreover,the introduction of self-assembled monolayers can regulate the energy level structure of NiO_(x),reduce the interfacial band energy offset,and hence promote the hole transport from perovskite to NiO_(x)layer.Consequently,the device performance is significantly enhanced in terms of both power conversion efficiency and stability.展开更多
Polarons are widely considered to play a crucial role in the charge transport and photocatalytic performance of materials,but the mechanisms of their formation and the underlying driving factors remain a matter of con...Polarons are widely considered to play a crucial role in the charge transport and photocatalytic performance of materials,but the mechanisms of their formation and the underlying driving factors remain a matter of controversy.This study delves into the formation of polarons in different crystalline forms of TiO_(2) and their connection with the materials'structure.By employing density functional theory calculations with on-site Coulomb interaction correction(DFT+U),we provide a detailed analysis of the electronic polarization behavior in the anatase and rutile forms of TiO_(2).We focus on the polarization properties of defect-induced and photoexcited excess electrons on various TiO_(2) surfaces.The results reveal that the defect electrons can form small polarons on the anatase TiO_(2)(101)surface,while on the rutile TiO_(2)(110)surface,both small and large polarons(hybrid-state polarons)are formed.Photoexcited electrons are capable of forming both small and large polarons on the surfaces of both crystal types.The analysis indicates that the differences in polaron distribution are primarily determined by the intrinsic properties of the crystals;the structural and symmetry differences between anatase and rutile TiO_(2) lead to the distinct polaron behaviors.Further investigation suggests that the polarization behavior of defect electrons is also related to the arrangement of electron orbitals around the Ti atoms,while the polarization of photoexcited electrons is mainly facilitated by the lattice distortions.These findings elucidate the formation mechanisms of different types of polarons and may contribute to understanding the performance of TiO_(2)in different fields.展开更多
Metal⁃organic framework(MOF)MIL⁃101 and surface plasmon polariton(SPP)supported gold nanoparti⁃cles(Au NPs)hybrid systems were developed as a highly sensitive and reproducible surface⁃enhanced Raman scat⁃tering(SERS)d...Metal⁃organic framework(MOF)MIL⁃101 and surface plasmon polariton(SPP)supported gold nanoparti⁃cles(Au NPs)hybrid systems were developed as a highly sensitive and reproducible surface⁃enhanced Raman scat⁃tering(SERS)detection platform,in which a green electrostatic self⁃assembly technology was adopted to construct the substrate.In an aqueous solution,the electronegativity of the particles can be used to prepare the composite sub⁃strate without any surface modifier.Due to the enrichment capacity of MIL⁃101 and the electromagnetic enhance⁃ment from Au NPs,the well⁃designed MIL⁃101/Au composites possessed ultrahigh sensitivity with the detection limit of Rhodamine 6G(R6G)as low as 10^(-10) mol·L^(-1).Meanwhile,the substrate exhibits high stability,excellent reproduc⁃ibility,and recyclability.Additionally,the novel substrate can be explored for direct capture,and sensitively detect pesticide residues such as thiram.展开更多
The reduced ability of fatty acids to dissolve and disperse at low temperatures limits their effectiveness in winter applications.In this study,a green and environment-friendly reagent,polyethylene glycol 2000(PEG-200...The reduced ability of fatty acids to dissolve and disperse at low temperatures limits their effectiveness in winter applications.In this study,a green and environment-friendly reagent,polyethylene glycol 2000(PEG-2000),was used to evaluate its effect on the collecting performance of sodium oleate during scheelite flotation at low temperatures.The effect of PEG-2000 on the flotation of scheelite with the collector sodium oleate(NaOL)was studied by flotation tests,surface tension tests,infrared spectral analysis,and zeta potential measurements.Flotation tests showed that adding PEG-2000 can enhance the collecting ability of NaOL on scheelite at low temperature(5℃).The recovery of scheelite with the mixed collector of PEG-200 and NaOL is 4.39%higher than that with NaOL only.The surface tension tests,infrared spectral analysis and zeta potential measurements revealed that PEG-2000 and OL^(−)are co-adsorbed on the scheelite surface at low temperatures.The presence of PEG-2000 promoted the increase of the adsorption concentration of oleate ions(OL^(−))on the scheelite surface.The reason was that PEG-2000 has a shielding effect on the electrostatic repulsion between the OL^(−)groups,which changes the micellar configuration of OL^(−)in the solution system and makes the OL^(−)gather more tightly on the surface of scheelite,leading to the enhancement of its hydrophobicity.This discovery provides a reference for the development of collecting reagents for efficient flotation recovery of scheelite under low temperature environment.展开更多
To address the seismic face stability challenges encountered in urban and subsea tunnel construction,an efficient probabilistic analysis framework for shield tunnel faces under seismic conditions is proposed.Based on ...To address the seismic face stability challenges encountered in urban and subsea tunnel construction,an efficient probabilistic analysis framework for shield tunnel faces under seismic conditions is proposed.Based on the upper-bound theory of limit analysis,an improved three-dimensional discrete deterministic mechanism,accounting for the heterogeneous nature of soil media,is formulated to evaluate seismic face stability.The metamodel of failure probabilistic assessments for seismic tunnel faces is constructed by integrating the sparse polynomial chaos expansion method(SPCE)with the modified pseudo-dynamic approach(MPD).The improved deterministic model is validated by comparing with published literature and numerical simulations results,and the SPCE-MPD metamodel is examined with the traditional MCS method.Based on the SPCE-MPD metamodels,the seismic effects on face failure probability and reliability index are presented and the global sensitivity analysis(GSA)is involved to reflect the influence order of seismic action parameters.Finally,the proposed approach is tested to be effective by a engineering case of the Chengdu outer ring tunnel.The results show that higher uncertainty of seismic response on face stability should be noticed in areas with intense earthquakes and variation of seismic wave velocity has the most profound influence on tunnel face stability.展开更多
Polar surfaces are prevalent in metal oxides,the interactions between surface species with polar surfaces are different from those with non-polar surfaces,a thorough understanding of the interactions is key to regulat...Polar surfaces are prevalent in metal oxides,the interactions between surface species with polar surfaces are different from those with non-polar surfaces,a thorough understanding of the interactions is key to regulate the performance of heterogeneous catalysts.In this work,we delve into the interaction of Pt_(n)(n=1-4)with polar ZnO(0001)-Zn and ZnO(0001)-O,and the influence of the surface polarity on the electronic structures and reactivity of Pt_(n)by using density functional theory calculations.The results suggest distinct differences in electronic structures of two exposed terminations,leading to different interactions with Pt_(n).The interaction between Pt_(n)and two terminations not only stabilizes the surface and clusters through polar compensation,but also induces opposite charges on the cluster at two terminations.Remarkably,the Pearson correlation coefficient reveals the interdependency between the electronic states of Pt_(n)and its performance in terms of small molecule adsorption/activation.These observations demonstrate the crucial role of surface polarity in regulating the electronic states and catalytic performance of active sites,and offer a possible design principle for supported catalysts.展开更多
Precise control of the local environment and electronic state of the guest is an important method of controlling catalytic activity and reaction pathways.In this paper,guest Pd NPs were introduced into a series of hos...Precise control of the local environment and electronic state of the guest is an important method of controlling catalytic activity and reaction pathways.In this paper,guest Pd NPs were introduced into a series of host UiO-67 MOFs with different functional ligands and metal nodes,the microenvironment and local electronic structure of Pd is modulated by introducing bipyridine groups and changing metal nodes(Ce_(6)O_(6) or Zr_(6)O_(6)).The bipyridine groups not only promoted the dispersion Pd NPs,but also facilitated electron transfer between Pd and UiO-67 MOFs through the formation of Pd-N bridges.Compared with Zr6 clusters,the tunability and orbital hybridisation of the 4f electronic structure in the Ce_(6) clusters modulate the electronic structure of Pd through the construction of the Ce-O-Pd interfaces.The optimal catalyst Pd/UiO-67(Ce)-bpy presented excellent low-temperature activity towards dicyclopentadiene hydrogenation with a conversion of>99% and a selectivity of>99%(50℃,10 bar).The results show that the synergy of Ce-O-Pd and Pd-N promotes the formation of active Pd^(δ+),which not only enhances the adsorption of H_(2) and electron-rich C=C bonds,but also contributes to the reduction of proton migration distance and improves proton utilization efficiency.These results provide valuable insights for investigating the regulatory role of the host MOFs,the nature of host-guest interactions,and their correlation with catalytic performance.展开更多
A novel metasurface antenna consisting of 5×5 rectangular patch elements is presented.Thestructure with and without the central element are both analyzed by the Characteristic Mode Theory(CMT).The developed mutua...A novel metasurface antenna consisting of 5×5 rectangular patch elements is presented.Thestructure with and without the central element are both analyzed by the Characteristic Mode Theory(CMT).The developed mutually orthogonal principal modes of the optimized periodic patch structure areexcited by a center-feed dipole.A differential feeding network is employed to realize impedance matching.Prototype with profile height of 0.07λ_(0)(λ_(0)is the wavelength in free space at the lowest operatingfrequency)is fabricated and assembled to verify the simulation results.The measured results show that thereflectance coefficient of proposed matesurface antenna is less than-10 dB in the whole operating bandrange from 4.2 GHz to 5.5 GHz,a relative bandwidth of 26.8%is achieved,and the maximummeasured realized gain is more than 9 dBi with a maximum radiation efficiency of 90%.The designprovides a guideline on the application of characteristic modes(CMs)to radiation problems.展开更多
Secondary electron emission(SEE)has emerged as a critical issue in next-generation accelerators.Mitigating SEE on metal surfaces is crucial for enhancing the stability and emittance of particle accelerators while exte...Secondary electron emission(SEE)has emerged as a critical issue in next-generation accelerators.Mitigating SEE on metal surfaces is crucial for enhancing the stability and emittance of particle accelerators while extending their lifespan.This paper explores the application of laser-assisted water jet technology in constructing high-quality micro-trap structures on 316L stainless steel,a key material in accelerator manufacturing.The study systematically analyzes the impact of various parameters such as laser repetition frequency,pulse duration,average power,water jet pressure,repeat times,nozzle offset,focal position,offset distance between grooves,and processing speed on the surface morphology of stainless steel.The findings reveal that micro-groove depth increases with higher laser power but decreases with increasing water jet pressure and processing speed.Interestingly,repeat times have minimal effect on depth.On the other hand,micro-groove width increases with higher laser power and repeat times but decreases with processing speed.By optimizing these parameters,the researchers achieved high-quality pound sign-shaped trap structure with consistent dimensions.We tested the secondary electron emission coefficient of the"well"structure.The coefficient is reduced by 0.5 at most compared to before processing,effectively suppressing secondary electron emission.These results offer indispensable insights for the fabrication of micro-trap structures on material surfaces.Laser-assisted water jet technology demonstrates considerable potential in mitigating SEE on metal surfaces.展开更多
Silver nanoplates,with average thickness about 5 nm and average tunable size from 40 to 500 nm,were synthesized via a simple room-temperature solution-phase chemical reduction method in the presence of appropriate con...Silver nanoplates,with average thickness about 5 nm and average tunable size from 40 to 500 nm,were synthesized via a simple room-temperature solution-phase chemical reduction method in the presence of appropriate concentration of trisodium citrate and silver seeds.The optical in-plane dipole plasmon resonance bands of these silver plates could be tuned from 520 to 1100 nm.Control experiments were explored for understanding of the growth mechanism.It is found that both the amount of citrate ions and the small silver seeds added to the growth solution are the key to controlling the silver nanoplates without changing their thickness and crystal structure.Small silver seeds are found to play an important role in the formation of large thin silver nanoplates when poly(vinylpyrrolidone)(PVP) are used as capping agent.展开更多
The combat survivability is an essential factor to be considered in the development of recent military aircraft. Radar stealth and onboard electronic attack are two major techniques for the reduction of aircraft susce...The combat survivability is an essential factor to be considered in the development of recent military aircraft. Radar stealth and onboard electronic attack are two major techniques for the reduction of aircraft susceptibility. A tactical scenario for a strike mission is presented. The effect of aircraft radar cross section on the detection probability of a threat radar, as well as that of onboard jammer, are investigated. The guidance errors of radar guided surface to air missile and anti aircraft artillery, which are disturbed by radar cross section reduction or jammer radiated power and both of them are determined. The probability of aircraft kill given a single shot is calculated and finally the sortie survivability of an attack aircraft in a supposed hostile thread environment worked out. It is demonstrated that the survivability of a combat aircraft will be greatly enhanced by the combined radar stealth and onboard electronic attack, and the evaluation metho dology is effective and applicable.展开更多
Novel silver/silver molybdate(Ag/Ag2MoO4) composites with surface plasmon resonance(SPR)-enhanced photocatalytic performance were successfully fabricated via a facile one-pot hydrothermal route with the presence o...Novel silver/silver molybdate(Ag/Ag2MoO4) composites with surface plasmon resonance(SPR)-enhanced photocatalytic performance were successfully fabricated via a facile one-pot hydrothermal route with the presence of sodium dodecyl sulfate(SDS) in this study.The as prepared silver/silver molybdate(Ag/Ag2MoO4) composites were systematically characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM) and ultraviolet-visible diffuse reflectance absorption spectroscopy(DRS) in order to investigate their crystal structure,morphology and optical property as well.The photocatalytic activities of the composites were subsequently evaluated by their ability to degrade rhodamine B(RhB) under visible-light irradiation.Varies of controlled experiments were then carefully operated to gain a deep insight into the assembling of Ag/Ag2MoO4composites.It was found that preparation conditions such as pH,reaction time,and the amount of surfactant played important roles in the formation of composites with octahedral microstructures.And the composite obtained at 160 ℃ using 0.5 g of sodium dodecyl sulfate exhibited the highest photocatalytic performance under visible-light irradiation.Capture experiments were also conducted to clarify the function of different active species generated on the surface of Ag/Ag2MoO4during the photocatalytic process,in which both holes and ·OH radicals were found to play crucial role in photocatalytic removal of RhB under visible light irradiation.A possible photocatalytic mechanism of Ag/Ag2MoO4 was finally proposed on the basis of all the results to explain the higher photocatalytic activity of the octahedral Ag/Ag2MoO4 composites.It was inferred that the photoinduced "hot" electrons can quickly transfer from the Ag NPs to the conduction band of Ag2MoO4 and react with oxygen and H2O to generate a large quality of active radicals such as ·OH and ·O2^- because of the SPR effects.Besides,this SPR effects of Ag nanoparticles deposited on the surface of Ag2MoO4 can not only dramatically amplify its light absorption,especially in the visible region,but also promote the separation of photoexcited electron-hole pairs and effectively decrease electron-hole recombination.展开更多
Gemini quaternary ammonium salt surfactants, butane-a, co-bis(dimethyl dodeculammonium bromide) (BDDA) ethane-a, fl-bis(dimethyl dodeculammonium bromide) (EDDA) were adopted to comparatively study the flotatio...Gemini quaternary ammonium salt surfactants, butane-a, co-bis(dimethyl dodeculammonium bromide) (BDDA) ethane-a, fl-bis(dimethyl dodeculammonium bromide) (EDDA) were adopted to comparatively study the flotation behaviors of kaolinite, pyrophyllite and illite. It was found that three silicate minerals all exhibited good floatability with Gemini cationic surfactants as collectors over a wide pH range, while BDDA showed a stronger collecting power than EDDA. FTIR spectra and zeta potential analysis indicated that the mechanism of adsorption of Gemini collector molecules on three silicate minerals surfaces was almost identical for the electronic attraction and hydrogen bonds effect. The theoretically obtained results of density functional theory (DFT) at B3LYP/6-31G (d) level demonstrated the stronger collecting power of BDDA presented in the floatation test and zeta potential measurement.展开更多
Triangular Au-Ag framework nanostructures (TFN) were synthesized via a multi-step galvanic replacement reaction (MGRR) of single-crystalline triangular silver nanoplates in a chlorauric acid (HAuCl4) solution at...Triangular Au-Ag framework nanostructures (TFN) were synthesized via a multi-step galvanic replacement reaction (MGRR) of single-crystalline triangular silver nanoplates in a chlorauric acid (HAuCl4) solution at room temperature. The morphological, compositional, and crystal structural changes involved with reaction steps were analyzed by using transmission electron microscopy(TEM), energy-dispersive X-ray spectrometry (EDX), and X-ray diffraction. TEM combined with EDX and selected area electron diffraction confirmed the replacement of Ag with Au. The in-plane dipolar surface plasmon resonance (SPR) absorption band of the Ag nanoplates locating initially at around 700 nm gradually redshifted to 1 100 nm via a multi-stage replacement manner after 7 stages. The adding amount of HAuCl4 per stage influenced the average redshift value per stage, thus enabled a fine tuning of the in-plane dipolar band. A proposed formation mechanism of the original Ag nanoplates developing pores while growing Au nanoparticles covering this underlying structure at more reaction steps was confirmed by exploiting surface-enhanced Raman scattering (SERS).展开更多
With the significant discharge of antibiotic wastewater into the aquatic and terrestrial ecosystems, antibiotic pollution has become a serious problem and presents a hazardous risk to the environment. To address such ...With the significant discharge of antibiotic wastewater into the aquatic and terrestrial ecosystems, antibiotic pollution has become a serious problem and presents a hazardous risk to the environment. To address such issues, various investigations on the removal of antibiotics have been undertaken. Photocatalysis has received tremendous attention owing to its great potential in removing antibiotics from aqueous solutions via a green, economic, and effective process. However, such a technology employing traditional photocatalysts suffers from major drawbacks such as light absorption being restricted to the UV spectrum only and fast charge recombination. To overcome these issues, considerable effort has been directed towards the development of advanced visible light-driven photocatalysts. This mini review summarises recent research progress in the state-of-the-art design and fabrication of photocatalysts with visible-light response for photocatalytic degradation of antibiotic wastewater. Such design strategies involve the doping of metal and non-metal into ultraviolet light-driven photocatalysts, development of new semiconductor photocatalysts, construction of heterojunction photocatalysts, and fabrication of surface plasmon resonance-enhanced photocatalytic systems. Additionally, some perspectives on the challenges and future developments in the area of photocatalytic degradation of antibiotics are provided.展开更多
文摘NiO_(x)as a hole transport material for inverted perovskite solar cells has received great attention owing to its high transparency,low fabrication temperature,and superior stability.However,the mismatched energy levels and possible redox reactions at the NiO_(x)/perovskite interface severely limit the performance of NiO_(x) based inverted perovskite solar cells.Herein,we introduce a p-type self-assembled monolayer between NiO_(x)and perovskite layers to modify the interface and block the undesirable redox reaction between perovskite and NiO_(x)The selfassembled monolayer molecules all contain phosphoric acid function groups,which can be anchored onto the NiOr surface and passivate the surface defect.Moreover,the introduction of self-assembled monolayers can regulate the energy level structure of NiO_(x),reduce the interfacial band energy offset,and hence promote the hole transport from perovskite to NiO_(x)layer.Consequently,the device performance is significantly enhanced in terms of both power conversion efficiency and stability.
文摘Polarons are widely considered to play a crucial role in the charge transport and photocatalytic performance of materials,but the mechanisms of their formation and the underlying driving factors remain a matter of controversy.This study delves into the formation of polarons in different crystalline forms of TiO_(2) and their connection with the materials'structure.By employing density functional theory calculations with on-site Coulomb interaction correction(DFT+U),we provide a detailed analysis of the electronic polarization behavior in the anatase and rutile forms of TiO_(2).We focus on the polarization properties of defect-induced and photoexcited excess electrons on various TiO_(2) surfaces.The results reveal that the defect electrons can form small polarons on the anatase TiO_(2)(101)surface,while on the rutile TiO_(2)(110)surface,both small and large polarons(hybrid-state polarons)are formed.Photoexcited electrons are capable of forming both small and large polarons on the surfaces of both crystal types.The analysis indicates that the differences in polaron distribution are primarily determined by the intrinsic properties of the crystals;the structural and symmetry differences between anatase and rutile TiO_(2) lead to the distinct polaron behaviors.Further investigation suggests that the polarization behavior of defect electrons is also related to the arrangement of electron orbitals around the Ti atoms,while the polarization of photoexcited electrons is mainly facilitated by the lattice distortions.These findings elucidate the formation mechanisms of different types of polarons and may contribute to understanding the performance of TiO_(2)in different fields.
文摘Metal⁃organic framework(MOF)MIL⁃101 and surface plasmon polariton(SPP)supported gold nanoparti⁃cles(Au NPs)hybrid systems were developed as a highly sensitive and reproducible surface⁃enhanced Raman scat⁃tering(SERS)detection platform,in which a green electrostatic self⁃assembly technology was adopted to construct the substrate.In an aqueous solution,the electronegativity of the particles can be used to prepare the composite sub⁃strate without any surface modifier.Due to the enrichment capacity of MIL⁃101 and the electromagnetic enhance⁃ment from Au NPs,the well⁃designed MIL⁃101/Au composites possessed ultrahigh sensitivity with the detection limit of Rhodamine 6G(R6G)as low as 10^(-10) mol·L^(-1).Meanwhile,the substrate exhibits high stability,excellent reproduc⁃ibility,and recyclability.Additionally,the novel substrate can be explored for direct capture,and sensitively detect pesticide residues such as thiram.
基金Project(2023JJ10070)supported by the Hunan Provincial Outstanding Youth Fund,ChinaProjects(51974364,52074355,52304316)supported by the National Natural Science Foundation of China。
文摘The reduced ability of fatty acids to dissolve and disperse at low temperatures limits their effectiveness in winter applications.In this study,a green and environment-friendly reagent,polyethylene glycol 2000(PEG-2000),was used to evaluate its effect on the collecting performance of sodium oleate during scheelite flotation at low temperatures.The effect of PEG-2000 on the flotation of scheelite with the collector sodium oleate(NaOL)was studied by flotation tests,surface tension tests,infrared spectral analysis,and zeta potential measurements.Flotation tests showed that adding PEG-2000 can enhance the collecting ability of NaOL on scheelite at low temperature(5℃).The recovery of scheelite with the mixed collector of PEG-200 and NaOL is 4.39%higher than that with NaOL only.The surface tension tests,infrared spectral analysis and zeta potential measurements revealed that PEG-2000 and OL^(−)are co-adsorbed on the scheelite surface at low temperatures.The presence of PEG-2000 promoted the increase of the adsorption concentration of oleate ions(OL^(−))on the scheelite surface.The reason was that PEG-2000 has a shielding effect on the electrostatic repulsion between the OL^(−)groups,which changes the micellar configuration of OL^(−)in the solution system and makes the OL^(−)gather more tightly on the surface of scheelite,leading to the enhancement of its hydrophobicity.This discovery provides a reference for the development of collecting reagents for efficient flotation recovery of scheelite under low temperature environment.
基金Project([2018]3010)supported by the Guizhou Provincial Science and Technology Major Project,China。
文摘To address the seismic face stability challenges encountered in urban and subsea tunnel construction,an efficient probabilistic analysis framework for shield tunnel faces under seismic conditions is proposed.Based on the upper-bound theory of limit analysis,an improved three-dimensional discrete deterministic mechanism,accounting for the heterogeneous nature of soil media,is formulated to evaluate seismic face stability.The metamodel of failure probabilistic assessments for seismic tunnel faces is constructed by integrating the sparse polynomial chaos expansion method(SPCE)with the modified pseudo-dynamic approach(MPD).The improved deterministic model is validated by comparing with published literature and numerical simulations results,and the SPCE-MPD metamodel is examined with the traditional MCS method.Based on the SPCE-MPD metamodels,the seismic effects on face failure probability and reliability index are presented and the global sensitivity analysis(GSA)is involved to reflect the influence order of seismic action parameters.Finally,the proposed approach is tested to be effective by a engineering case of the Chengdu outer ring tunnel.The results show that higher uncertainty of seismic response on face stability should be noticed in areas with intense earthquakes and variation of seismic wave velocity has the most profound influence on tunnel face stability.
基金This work was financially supported by the National Natural Science Foundation of China(Nos.22303085,22102150 and 22172146)the Zhejiang Provincial Natural Science Foundation of China(LQ24B030014 andLQ21B030010).
文摘Polar surfaces are prevalent in metal oxides,the interactions between surface species with polar surfaces are different from those with non-polar surfaces,a thorough understanding of the interactions is key to regulate the performance of heterogeneous catalysts.In this work,we delve into the interaction of Pt_(n)(n=1-4)with polar ZnO(0001)-Zn and ZnO(0001)-O,and the influence of the surface polarity on the electronic structures and reactivity of Pt_(n)by using density functional theory calculations.The results suggest distinct differences in electronic structures of two exposed terminations,leading to different interactions with Pt_(n).The interaction between Pt_(n)and two terminations not only stabilizes the surface and clusters through polar compensation,but also induces opposite charges on the cluster at two terminations.Remarkably,the Pearson correlation coefficient reveals the interdependency between the electronic states of Pt_(n)and its performance in terms of small molecule adsorption/activation.These observations demonstrate the crucial role of surface polarity in regulating the electronic states and catalytic performance of active sites,and offer a possible design principle for supported catalysts.
文摘Precise control of the local environment and electronic state of the guest is an important method of controlling catalytic activity and reaction pathways.In this paper,guest Pd NPs were introduced into a series of host UiO-67 MOFs with different functional ligands and metal nodes,the microenvironment and local electronic structure of Pd is modulated by introducing bipyridine groups and changing metal nodes(Ce_(6)O_(6) or Zr_(6)O_(6)).The bipyridine groups not only promoted the dispersion Pd NPs,but also facilitated electron transfer between Pd and UiO-67 MOFs through the formation of Pd-N bridges.Compared with Zr6 clusters,the tunability and orbital hybridisation of the 4f electronic structure in the Ce_(6) clusters modulate the electronic structure of Pd through the construction of the Ce-O-Pd interfaces.The optimal catalyst Pd/UiO-67(Ce)-bpy presented excellent low-temperature activity towards dicyclopentadiene hydrogenation with a conversion of>99% and a selectivity of>99%(50℃,10 bar).The results show that the synergy of Ce-O-Pd and Pd-N promotes the formation of active Pd^(δ+),which not only enhances the adsorption of H_(2) and electron-rich C=C bonds,but also contributes to the reduction of proton migration distance and improves proton utilization efficiency.These results provide valuable insights for investigating the regulatory role of the host MOFs,the nature of host-guest interactions,and their correlation with catalytic performance.
文摘A novel metasurface antenna consisting of 5×5 rectangular patch elements is presented.Thestructure with and without the central element are both analyzed by the Characteristic Mode Theory(CMT).The developed mutually orthogonal principal modes of the optimized periodic patch structure areexcited by a center-feed dipole.A differential feeding network is employed to realize impedance matching.Prototype with profile height of 0.07λ_(0)(λ_(0)is the wavelength in free space at the lowest operatingfrequency)is fabricated and assembled to verify the simulation results.The measured results show that thereflectance coefficient of proposed matesurface antenna is less than-10 dB in the whole operating bandrange from 4.2 GHz to 5.5 GHz,a relative bandwidth of 26.8%is achieved,and the maximummeasured realized gain is more than 9 dBi with a maximum radiation efficiency of 90%.The designprovides a guideline on the application of characteristic modes(CMs)to radiation problems.
文摘Secondary electron emission(SEE)has emerged as a critical issue in next-generation accelerators.Mitigating SEE on metal surfaces is crucial for enhancing the stability and emittance of particle accelerators while extending their lifespan.This paper explores the application of laser-assisted water jet technology in constructing high-quality micro-trap structures on 316L stainless steel,a key material in accelerator manufacturing.The study systematically analyzes the impact of various parameters such as laser repetition frequency,pulse duration,average power,water jet pressure,repeat times,nozzle offset,focal position,offset distance between grooves,and processing speed on the surface morphology of stainless steel.The findings reveal that micro-groove depth increases with higher laser power but decreases with increasing water jet pressure and processing speed.Interestingly,repeat times have minimal effect on depth.On the other hand,micro-groove width increases with higher laser power and repeat times but decreases with processing speed.By optimizing these parameters,the researchers achieved high-quality pound sign-shaped trap structure with consistent dimensions.We tested the secondary electron emission coefficient of the"well"structure.The coefficient is reduced by 0.5 at most compared to before processing,effectively suppressing secondary electron emission.These results offer indispensable insights for the fabrication of micro-trap structures on material surfaces.Laser-assisted water jet technology demonstrates considerable potential in mitigating SEE on metal surfaces.
基金Project (10804101) supported by the National Nature Science Foundation of ChinaProject (2007CB815102) supported by the National Basic Research Program of ChinaProject (2007B08007) supported by the Science and Technology Development Foundation of Chinese Academy of Engineering Physics
文摘Silver nanoplates,with average thickness about 5 nm and average tunable size from 40 to 500 nm,were synthesized via a simple room-temperature solution-phase chemical reduction method in the presence of appropriate concentration of trisodium citrate and silver seeds.The optical in-plane dipole plasmon resonance bands of these silver plates could be tuned from 520 to 1100 nm.Control experiments were explored for understanding of the growth mechanism.It is found that both the amount of citrate ions and the small silver seeds added to the growth solution are the key to controlling the silver nanoplates without changing their thickness and crystal structure.Small silver seeds are found to play an important role in the formation of large thin silver nanoplates when poly(vinylpyrrolidone)(PVP) are used as capping agent.
文摘The combat survivability is an essential factor to be considered in the development of recent military aircraft. Radar stealth and onboard electronic attack are two major techniques for the reduction of aircraft susceptibility. A tactical scenario for a strike mission is presented. The effect of aircraft radar cross section on the detection probability of a threat radar, as well as that of onboard jammer, are investigated. The guidance errors of radar guided surface to air missile and anti aircraft artillery, which are disturbed by radar cross section reduction or jammer radiated power and both of them are determined. The probability of aircraft kill given a single shot is calculated and finally the sortie survivability of an attack aircraft in a supposed hostile thread environment worked out. It is demonstrated that the survivability of a combat aircraft will be greatly enhanced by the combined radar stealth and onboard electronic attack, and the evaluation metho dology is effective and applicable.
基金supported by Fundamental Research Funds for the Central Universities (2662014BQ061, 2015PY120, 2015PY047, 2016PY088)the National Natural Science Foundation of China (51572101, 21502059, 21607047)~~
文摘Novel silver/silver molybdate(Ag/Ag2MoO4) composites with surface plasmon resonance(SPR)-enhanced photocatalytic performance were successfully fabricated via a facile one-pot hydrothermal route with the presence of sodium dodecyl sulfate(SDS) in this study.The as prepared silver/silver molybdate(Ag/Ag2MoO4) composites were systematically characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM) and ultraviolet-visible diffuse reflectance absorption spectroscopy(DRS) in order to investigate their crystal structure,morphology and optical property as well.The photocatalytic activities of the composites were subsequently evaluated by their ability to degrade rhodamine B(RhB) under visible-light irradiation.Varies of controlled experiments were then carefully operated to gain a deep insight into the assembling of Ag/Ag2MoO4composites.It was found that preparation conditions such as pH,reaction time,and the amount of surfactant played important roles in the formation of composites with octahedral microstructures.And the composite obtained at 160 ℃ using 0.5 g of sodium dodecyl sulfate exhibited the highest photocatalytic performance under visible-light irradiation.Capture experiments were also conducted to clarify the function of different active species generated on the surface of Ag/Ag2MoO4during the photocatalytic process,in which both holes and ·OH radicals were found to play crucial role in photocatalytic removal of RhB under visible light irradiation.A possible photocatalytic mechanism of Ag/Ag2MoO4 was finally proposed on the basis of all the results to explain the higher photocatalytic activity of the octahedral Ag/Ag2MoO4 composites.It was inferred that the photoinduced "hot" electrons can quickly transfer from the Ag NPs to the conduction band of Ag2MoO4 and react with oxygen and H2O to generate a large quality of active radicals such as ·OH and ·O2^- because of the SPR effects.Besides,this SPR effects of Ag nanoparticles deposited on the surface of Ag2MoO4 can not only dramatically amplify its light absorption,especially in the visible region,but also promote the separation of photoexcited electron-hole pairs and effectively decrease electron-hole recombination.
基金Project(2013AA064102)supported by the High-tech Research and Development Program of ChinaProject(51004114)supported by the National Natural Science Foundation of China+1 种基金Project(2007B52)supported by the Foundation for the Author of National Excellent Doctoral Dissertation of ChinaProject(NCEP-08-0568)supported by the Program for New Century Excellent Talents in Chinese University
文摘Gemini quaternary ammonium salt surfactants, butane-a, co-bis(dimethyl dodeculammonium bromide) (BDDA) ethane-a, fl-bis(dimethyl dodeculammonium bromide) (EDDA) were adopted to comparatively study the flotation behaviors of kaolinite, pyrophyllite and illite. It was found that three silicate minerals all exhibited good floatability with Gemini cationic surfactants as collectors over a wide pH range, while BDDA showed a stronger collecting power than EDDA. FTIR spectra and zeta potential analysis indicated that the mechanism of adsorption of Gemini collector molecules on three silicate minerals surfaces was almost identical for the electronic attraction and hydrogen bonds effect. The theoretically obtained results of density functional theory (DFT) at B3LYP/6-31G (d) level demonstrated the stronger collecting power of BDDA presented in the floatation test and zeta potential measurement.
基金Project(10804101)supported by the National Natural Science Foundation of ChinaProject(2007CB815102)supported by the National Basic Research Program of ChinaProject(2007B08007)supported by the Science and Technology Development Foundation of Chinese Academy of Engineering Physics,China
文摘Triangular Au-Ag framework nanostructures (TFN) were synthesized via a multi-step galvanic replacement reaction (MGRR) of single-crystalline triangular silver nanoplates in a chlorauric acid (HAuCl4) solution at room temperature. The morphological, compositional, and crystal structural changes involved with reaction steps were analyzed by using transmission electron microscopy(TEM), energy-dispersive X-ray spectrometry (EDX), and X-ray diffraction. TEM combined with EDX and selected area electron diffraction confirmed the replacement of Ag with Au. The in-plane dipolar surface plasmon resonance (SPR) absorption band of the Ag nanoplates locating initially at around 700 nm gradually redshifted to 1 100 nm via a multi-stage replacement manner after 7 stages. The adding amount of HAuCl4 per stage influenced the average redshift value per stage, thus enabled a fine tuning of the in-plane dipolar band. A proposed formation mechanism of the original Ag nanoplates developing pores while growing Au nanoparticles covering this underlying structure at more reaction steps was confirmed by exploiting surface-enhanced Raman scattering (SERS).
基金supported by the National Natural Science Foundation of China(21421001,21276116,21477050,21301076,21303074)Natural Science Foundation of Jiangsu Province(BK20140530,BK20150482)+5 种基金China Postdoctoral Science Foundation(2015M570409)Chinese-German Cooperation Research Project(GZ1091)Program for High-Level Innovative and Entrepreneurial Talents in Jiangsu ProvinceProgram for New Century Excellent Talents in University(NCET-13-0835)Henry Fok Education Foundation(141068)Six Talents Peak Project in Jiangsu Province(XCL-025)~~
文摘With the significant discharge of antibiotic wastewater into the aquatic and terrestrial ecosystems, antibiotic pollution has become a serious problem and presents a hazardous risk to the environment. To address such issues, various investigations on the removal of antibiotics have been undertaken. Photocatalysis has received tremendous attention owing to its great potential in removing antibiotics from aqueous solutions via a green, economic, and effective process. However, such a technology employing traditional photocatalysts suffers from major drawbacks such as light absorption being restricted to the UV spectrum only and fast charge recombination. To overcome these issues, considerable effort has been directed towards the development of advanced visible light-driven photocatalysts. This mini review summarises recent research progress in the state-of-the-art design and fabrication of photocatalysts with visible-light response for photocatalytic degradation of antibiotic wastewater. Such design strategies involve the doping of metal and non-metal into ultraviolet light-driven photocatalysts, development of new semiconductor photocatalysts, construction of heterojunction photocatalysts, and fabrication of surface plasmon resonance-enhanced photocatalytic systems. Additionally, some perspectives on the challenges and future developments in the area of photocatalytic degradation of antibiotics are provided.