Active multiple tuned mass dampers （referred to as AMTMD）, which consist of several active tuned mass dampers （ATMDs） with identical stiffness and damping coefficients but varying mass and control force, have rece...Active multiple tuned mass dampers （referred to as AMTMD）, which consist of several active tuned mass dampers （ATMDs） with identical stiffness and damping coefficients but varying mass and control force, have recently been proposed to suppress undesirable oscillations of structures under ground acceleration. It has been shown that the AMTMD can remarkably improve the performance of multiple tuned mass dampers （MTMDs） and is also more effective in reducing structure oscillation than single ATMDs. Notwithstanding this, good performance of AMTMD （including a single ATMD illustrated from frequency-domain analysis） may not necessarily translate into a good seismic reduction behavior in the time-domain. To investigate these phenomena, a three-story steel structure model controlled by AMTMD with three ATMDs was implemented in SIMULINK and subjected to several historical earthquakes. Likewise, the structure under consideration was assumed to have uncertainty of stiffness, such as 4-15% of its initial stiffness, in the numerical simulations. The optimum design parameters of the AMTMD were obtained in the frequency-domain by implementing the minimization of the minimum values of the maximum dynamic magnification factors （DMF） of general structures with AMTMD. For comparison purposes, response analysis of the same structure with a single ATMD was also performed. The numerical analysis and comparison show that the AMTMD generally renders better effectiveness when compared with a single ATMD for structures subjected to historical earthquakes. In particular, the AMTMD can improve the effectiveness of a single ATMD for a structure with an uncertainty of stiffness of 4-15% of its initial stiffness.展开更多
Cost-effective atomically dispersed Fe-N-P-C complex catalysts are promising to catalyze the oxygen reduction reaction(ORR)and replace Pt catalysts in fuel cells and metal-air batteries.However,it remains a challenge ...Cost-effective atomically dispersed Fe-N-P-C complex catalysts are promising to catalyze the oxygen reduction reaction(ORR)and replace Pt catalysts in fuel cells and metal-air batteries.However,it remains a challenge to increase the number of atomically dispersed active sites on these catalysts.Here we report a highly efficient impregnation-pyrolysis method to prepare effective ORR electrocatalysts with large amount of atomically dispersed Fe active sites from biomass.Two types of active catalyst centers were identified,namely atomically dispersed Fe sites and Fe_(x)P particles.The ORR rate of the atomically dispersed Fe sites is three orders of magnitude higher than it of Fe_(x)P particles.A linear correlation between the amount of the atomically dispersed Fe and the ORR activity was obtained,revealing the major contribution of the atomically dispersed Fe to the ORR activity.The number of atomically dispersed Fe increases as the Fe loading increased and reaching the maximum at 1.86 wt%Fe,resulting in the maximum ORR rate.Optimized Fe-N-P-C complex catalyst was used as the cathode catalyst in a homemade Zn-air battery and good performance of an energy density of 771 Wh kgZn^(-1),a power density of 92.9 m W cm^(-2) at 137 m A cm^(-2) and an excellent durability were exhibited.展开更多
Advanced oxidation processes(AOPs)governed by peroxide activation to produce highly oxidative active species have been extensively explored for environmental remediation.Nevertheless,the low diffusion rates,inadequate...Advanced oxidation processes(AOPs)governed by peroxide activation to produce highly oxidative active species have been extensively explored for environmental remediation.Nevertheless,the low diffusion rates,inadequate interactions of the reactants,and limited active site exposure hinder treatment efficiency.Porous carbocatalysts with high specific surface area,tunable pore size,and programmable active sites demonstrate outstanding performance in activating diverse types of peroxides to generate active species for treatment of aqueous organic pollutants.The pore-rich structures enhance reaction kinetics for peroxide activation by facilitating diffusion of the reactants and their interactions.Additionally,the structural flexibility of porous structures favors the accommodation of highly dispersed metal species and allows for precise tuning of the microenvironment around the active sites,which further enhances the catalytic activity.This review critically summarizes the recent research progress in the applications of engineered porous carbocatalysts for peroxide activation and outlines the prevailing pore construction methods in carbocatalysts.Moreover,engineering strategies to regulate the mass transfer efficiency and fine-tune the microenvironment around the active sites are systematically addressed to enhance their catalytic peroxide activation performances.Challenges and future research opportunities pertaining to the design,optimization,mechanistic investigation,and practical application of porous carbocatalysts in peroxide activation are also proposed.展开更多
Formic acid(FA)dehydrogenation was investigated over several arene-ruthenium catalysts with various imidazolyl-,thiophenyl-and furyl-based ligands.The catalyst with an N-((1H-imidazol-2-yl)methyl)propan-2-amine ligand...Formic acid(FA)dehydrogenation was investigated over several arene-ruthenium catalysts with various imidazolyl-,thiophenyl-and furyl-based ligands.The catalyst with an N-((1H-imidazol-2-yl)methyl)propan-2-amine ligand(Ru/L7)outperformed other catalysts in FA dehydrogenation at 90℃ in water.Furthermore,the developed process was scaled up by a factor of 10 without any loss in activity.Remarkably,Ru/L7 exhibited high robustness and long-term durability during reusability over 79 catalytic runs,achieving very high turnovers per Ru,releasing 37.6 L of gas(H_(2) and CO_(2))with a productivity rate of 15660 L(H_(2)+CO_(2))molRu−1 h^(−1)(∼7 gH_(2) gRu^(−1) h^(−1)).Advantageously,the Ru/L7 catalyst also promoted CO_(2)hydrogenation to formate at 80℃.Mechanistic insights were gained through KIE studies and via the identification of several catalytic intermediates involved in various steps of catalytic FA dehydrogenation and CO_(2)hydrogenation under catalytic and controlled reaction conditions.展开更多
Li-rich layered transition metal oxides are one of the most promising cathode materials for their high energy density.However,the cathodes usually suffer from severe potential dropping and capacity fading during cycli...Li-rich layered transition metal oxides are one of the most promising cathode materials for their high energy density.However,the cathodes usually suffer from severe potential dropping and capacity fading during cycling,which are associated with the surface oxygen release and accompanied by cation densification and structural collapse.Herein,an integrative approach of simultaneous constructing uniform 3d Fe-ion doping in the transition metal layer and Li-rich Li_(5)FeO_(4) shell to grab the oxygen and prevent interfacial side reactions is proposed.The introduction of Fe induces higher redox potential and stronger 3 d Fe-O_(2)p covalent bond,triggering reversible anionic redox via a reductive coupling mechanism.And the delithiated product of Li-rich Li_(5)FeO_(4) not only acts as a protective layer alleviating the side reactions but also enhances the surface kinetic property.With the benefit of promoted reversibility of oxygen redox and enhanced surface stability,the cathode exhibits high reversible capacity and superior cycle performance.Density function theory calculation indicates that the O_(2)p non-bonding state in the cathode incorporated with Fe sits at a lower energy band,resulting in higher energy storage voltage and improved oxygen stability.Consequently,the modified cathode exhibits a discharge specific capacity of 307 m A h g^(-1)(1 C=250 m A g^(-1)),coulombic efficiency of 82.09%in the initial cycle at 0.1 C and 88.34%capacity retention after 100 cycles at 1 C.The work illustrates a strategy that could simultaneously enhance oxygen redox reversibility and interface stability by constructing lattice bond coordination and delithiation induced protective layer to develop Li-rich materials with high reversible capacity and long lifespan.展开更多
Exceptional points(EPs)have been extensively explored in mechanical,acoustic,plasmonic,and photonic systems.However,little is known about the role of EPs in tailoring the dynamic tunability of optical devices.A specif...Exceptional points(EPs)have been extensively explored in mechanical,acoustic,plasmonic,and photonic systems.However,little is known about the role of EPs in tailoring the dynamic tunability of optical devices.A specific type of EPs known as chiral EPs has recently attracted much attention for controlling the flow of light and for building sensors with better responsivity.A recently demonstrated route to chiral EPs via lithographically defined symmetric Mie scatterers on the rim of resonators has not only provided the much-needed mechanical stability for studying chiral EPs,but also helped reduce losses originating from nanofabrication imperfections,facilitating the in-situ study of chiral EPs and their contribution to the dynamics and tunability of resonators.Here,we use asymmetric Mie scatterers to break the rotational symmetry of a microresonator,to demonstrate deterministic thermal tuning across a chiral EP,and to demonstrate EP-mediated chiral optical nonlinear response and efficient electro-optic tuning.Our results indicate asymmetric electro-optic modulation with up to 17 dB contrast at GHz and CMOS-compatible voltage levels.Such wafer-scale nano-manufacturing of chiral electro-optic modulators and the chiral EP-tailored tunning may facilitate new micro-resonator functionalities in quantum information processing,electromagnetic wave control,and optical interconnects.展开更多
Hyperbolic polaritons are known to exist in materials with extreme anisotropy,exhibiting exotic optical properties that enable a plethora of unusual phenomena in the fields of polaritonics and photonics.However,achiev...Hyperbolic polaritons are known to exist in materials with extreme anisotropy,exhibiting exotic optical properties that enable a plethora of unusual phenomena in the fields of polaritonics and photonics.However,achieving simultaneous low-dimensionality,high-speed controllability,and on-demand reconfigurability of the polaritons remains unexplored despite their excellent potential in light-matter interactions,photonic integrated circuits,and optoelectronic devices.Here,we propose a metasurface approach to integrating artificially engineered electromagnetic anisotropy with fast-controllable electronic elements,offering a new route to realize active topological polaritons.Experiments showcase the proposed reconfigurable metasurface can support real-time transitions of designer polaritons from elliptical to flat,and then to hyperbolic and circular isofrequency contours.Correspondingly,the in-plane surface wavefront undergoes the transitions from convex to collimating,concave,and eventually back to convex.By exploiting the topological variations in polariton dispersions,we observe intriguing phenomena of controllable field canalization and tunable planar focusing.Furthermore,we report the concept of a planar reconfigurable integrated polariton circuit by spatially tailoring the distributions of polariton isofrequency contours,unveiling rich dispersion engineering possibilities and active control capabilities.We may provide an inspiring platform for developing planar active plasmonic devices with potential applications in subdiffraction-resolution imaging,sensing,and information processing.展开更多
We report here a theoretical study on 34 transition metal doped two-dimensional GaPS_(4) catalysts,denoted as transition metal transition metal@VS-GaPS_(4).Among them,the Pt@V_(S1)-GaPS_(4) single-atom catalyst is fou...We report here a theoretical study on 34 transition metal doped two-dimensional GaPS_(4) catalysts,denoted as transition metal transition metal@VS-GaPS_(4).Among them,the Pt@V_(S1)-GaPS_(4) single-atom catalyst is found to be stable with an ORR/OER overpotential of 0.59/0.41 V.Under the guidance of a volcano map,further biaxial strain engineering is adopted to tune the activity of Pt@V_(S1)-GaPS_(4) to the top of the volcano.The overpotentials of the OER/ORR are decreased to 0.37/0.33 V by applying a 3%tensile strain.Our results prove that Pt@V_(S1)-GaPS_(4) is an excellent candidate for OER/ORR bifunctional electro-catalysis.Moreover,bond angles and the highest occupied orbitals of the doped transition metal atoms can be used as descriptors to explain the underlying strain tunability mechanism.The machine learning method further predicts that the number of d electrons,the bond length and electronegativity are three main descriptors to determine the catalytic activity.展开更多
Interfacial charge transfer and active sites play important roles in the performance of heterogeneousphotocatalysts. Reticular chemistry in covalent organic frameworks (COFs) allows the construction of isomericarchite...Interfacial charge transfer and active sites play important roles in the performance of heterogeneousphotocatalysts. Reticular chemistry in covalent organic frameworks (COFs) allows the construction of isomericarchitectures made of different donor and acceptor monomers for tuning the charge transferdynamics and active sites. Herein, five D-A dual-pore COFs were prepared from the reaction of naphthalene-2,6-diamine (electron donor) with different tetraaldehyde electron acceptors. Experimental resultsdisclosed that linker engineering, by changing the conjugation systems using heteroatoms of benzooxadiazole,benzothiadiazole, benzoselenadiazole, naphthothiadiazole, and naphthoselenadiazole, tuned theelectron-accepting capacity of the corresponding D-A COFs. Among the five samples, the naphthothiadiazole-derived COF demonstrated optimal charge transfer and active sites, exhibiting the highest hydrogenevolution rate of ca. 35 mmol g^(-1) h^(-1) in the presence of 3 wt% Pt under visible-light irradiation(>420 nm). This work illustrates linker engineering as a strategy for the simultaneous adjustment of interfacialcharge transfer and active sites to enhance the hydrogen generation efficiency, offering new vigorto develop the COF photocatalysts on the basis of reticular synthesis.展开更多
The main bottleneck of electrolytic water for hydrogen production in alkaline media is the oxygen evolution reaction(OER)involving four-electron transfer.Designing highly efficient OER catalysts is attractive to accel...The main bottleneck of electrolytic water for hydrogen production in alkaline media is the oxygen evolution reaction(OER)involving four-electron transfer.Designing highly efficient OER catalysts is attractive to accelerate this process.Monoclinic oxides have gained enormous interest as promising candidates for electrocatalysis due to their low cost and abundant storage.The introduction of transition metals into metal oxides to tune the electronic structure of active sites is regarded as one of the promising methods for enhancing OER performance.Herein,we designed a Fe_(2)(MoO_(4))_(3) catalyst by a spray pyrolysis strategy and enhanced the OER performance of Fe_(2)(MoO_(4))_(3) with Co doping,which displayed a low overpotential of 273 mV to drive 10 mA cm^(2).The octahedral Fe site engineering leads to higher reaction kinetics and more active site exposure.Density functional theory(DFT)calculations further revealed that the introduction of Co can reduce the energy barrier for the OER process and weaken the absorption of*-O.This work provides a new insight into the fabrication of monoclinic oxide electrocatalysts for OERs in alkaline media.展开更多
Integrated high-linearity modulators are crucial for high dynamic-range microwave photonic(MWP)systems.Conventional linearization schemes usually involve the fine tuning of radio-frequency(RF)power distribution,which ...Integrated high-linearity modulators are crucial for high dynamic-range microwave photonic(MWP)systems.Conventional linearization schemes usually involve the fine tuning of radio-frequency(RF)power distribution,which is rather inconvenient for practical applications and can hardly be implemented on the integrated photonics chip.In this paper,we propose an elegant scheme to linearize a silicon-based modulator in which the active tuning of RF power is eliminated.The device consists of two carrier-depletion-based Mach-Zehnder modulators(MZMs),which are connected in series by a 1×2 thermal optical switch(OS).The OS is used to adjust the ratio between the modulation depths of the two sub-MZMs.Under a proper ratio,the complementary third-order intermodulation distortion(IMD3)of the two sub-MZMs can effectively cancel each other out.The measured spurious-free dynamic ranges for IMD3 are 131,127,118,110,and 109 d B·Hz^(6∕7)at frequencies of 1,10,20,30,and 40 GHz,respectively,which represent the highest linearities ever reached by the integrated modulator chips on all available material platforms.展开更多
We experimentally demonstrate an ultra-thin plasmonic optical rotator in the visible regime that induces a polarization rotation that is continuously tunable and switchable by an external magnetic field.The rotator is...We experimentally demonstrate an ultra-thin plasmonic optical rotator in the visible regime that induces a polarization rotation that is continuously tunable and switchable by an external magnetic field.The rotator is a magneto-plasmonic hybrid structure consisting of a magneto-optical EuSe slab and a one-dimensional plasmonic gold grating.At low temperatures,EuSe possesses a large Verdet constant and exhibits Faraday rotation,which does not saturate over a regime of several Tesla.By combining these properties with plasmonic Faraday rotation enhancement,a large tuning range of the polarization rotation of up to 8.4° for a film thickness of 220 nm is achieved.Furthermore,through experiments and simulations,we demonstrate that the unique dispersion properties of the structure enable us to tailor the wavelengths of the tunable polarization rotation to arbitrary spectral positions within the transparency window of the magneto-optical slab.The demonstrated concept might lead to important,highly integrated,non-reciprocal,photonic devices for light modulation,optical isolation,and magnetic field optical sensing.The simple fabrication of EuSe nanostructures by physical vapor deposition opens the way for many potentially interesting magneto-plasmonic systems and three-dimensional magneto-optical metamaterials.展开更多
This paper presents a low power tunable active inductor and RF band pass filter suitable for multiband RF front end circuits. The active inductor circuit uses the PMOS cascode structure as the negative transconductor ...This paper presents a low power tunable active inductor and RF band pass filter suitable for multiband RF front end circuits. The active inductor circuit uses the PMOS cascode structure as the negative transconductor of a gyrator to reduce the noise voltage. Also, this structure provides possible negative resistance to reduce the inductor loss with wide inductive bandwidth and high resonance frequency. The RF band pass filter is realized using the proposed active inductor with suitable input and output buffer stages. The tuning of the center frequency for multiband operation is achieved through the controllable current source. The designed active inductor and RF band pass filter are simulated in 180 nm and 45 nm CMOS process using the Synopsys HSPICE simulation tool and their performances are compared. The parameters, such as resonance frequency, tuning capability, noise and power dissipation, are analyzed for these CMOS technologies and discussed. The design of a third order band pass filter using an active inductor is also presented.展开更多
文摘Active multiple tuned mass dampers （referred to as AMTMD）, which consist of several active tuned mass dampers （ATMDs） with identical stiffness and damping coefficients but varying mass and control force, have recently been proposed to suppress undesirable oscillations of structures under ground acceleration. It has been shown that the AMTMD can remarkably improve the performance of multiple tuned mass dampers （MTMDs） and is also more effective in reducing structure oscillation than single ATMDs. Notwithstanding this, good performance of AMTMD （including a single ATMD illustrated from frequency-domain analysis） may not necessarily translate into a good seismic reduction behavior in the time-domain. To investigate these phenomena, a three-story steel structure model controlled by AMTMD with three ATMDs was implemented in SIMULINK and subjected to several historical earthquakes. Likewise, the structure under consideration was assumed to have uncertainty of stiffness, such as 4-15% of its initial stiffness, in the numerical simulations. The optimum design parameters of the AMTMD were obtained in the frequency-domain by implementing the minimization of the minimum values of the maximum dynamic magnification factors （DMF） of general structures with AMTMD. For comparison purposes, response analysis of the same structure with a single ATMD was also performed. The numerical analysis and comparison show that the AMTMD generally renders better effectiveness when compared with a single ATMD for structures subjected to historical earthquakes. In particular, the AMTMD can improve the effectiveness of a single ATMD for a structure with an uncertainty of stiffness of 4-15% of its initial stiffness.
基金The financial supports from Department of Chemical Engineeringthe support from China Scholarship Council(CSC)for his study at NTNU。
文摘Cost-effective atomically dispersed Fe-N-P-C complex catalysts are promising to catalyze the oxygen reduction reaction(ORR)and replace Pt catalysts in fuel cells and metal-air batteries.However,it remains a challenge to increase the number of atomically dispersed active sites on these catalysts.Here we report a highly efficient impregnation-pyrolysis method to prepare effective ORR electrocatalysts with large amount of atomically dispersed Fe active sites from biomass.Two types of active catalyst centers were identified,namely atomically dispersed Fe sites and Fe_(x)P particles.The ORR rate of the atomically dispersed Fe sites is three orders of magnitude higher than it of Fe_(x)P particles.A linear correlation between the amount of the atomically dispersed Fe and the ORR activity was obtained,revealing the major contribution of the atomically dispersed Fe to the ORR activity.The number of atomically dispersed Fe increases as the Fe loading increased and reaching the maximum at 1.86 wt%Fe,resulting in the maximum ORR rate.Optimized Fe-N-P-C complex catalyst was used as the cathode catalyst in a homemade Zn-air battery and good performance of an energy density of 771 Wh kgZn^(-1),a power density of 92.9 m W cm^(-2) at 137 m A cm^(-2) and an excellent durability were exhibited.
基金supports from the National Natural Science Foundation of China(Nos.22478426 and 22278436)Young Elite Scientists Sponsorship Program by BAST(No.1101020370359)Science Foundation of China University of Petroleum,Beijing(No.2462021QNXZ009)。
文摘Advanced oxidation processes(AOPs)governed by peroxide activation to produce highly oxidative active species have been extensively explored for environmental remediation.Nevertheless,the low diffusion rates,inadequate interactions of the reactants,and limited active site exposure hinder treatment efficiency.Porous carbocatalysts with high specific surface area,tunable pore size,and programmable active sites demonstrate outstanding performance in activating diverse types of peroxides to generate active species for treatment of aqueous organic pollutants.The pore-rich structures enhance reaction kinetics for peroxide activation by facilitating diffusion of the reactants and their interactions.Additionally,the structural flexibility of porous structures favors the accommodation of highly dispersed metal species and allows for precise tuning of the microenvironment around the active sites,which further enhances the catalytic activity.This review critically summarizes the recent research progress in the applications of engineered porous carbocatalysts for peroxide activation and outlines the prevailing pore construction methods in carbocatalysts.Moreover,engineering strategies to regulate the mass transfer efficiency and fine-tune the microenvironment around the active sites are systematically addressed to enhance their catalytic peroxide activation performances.Challenges and future research opportunities pertaining to the design,optimization,mechanistic investigation,and practical application of porous carbocatalysts in peroxide activation are also proposed.
基金the financial support from IIT Indore,CSIR(01(3045)/21/EMR-II)DST(CRG/2021/000504).
文摘Formic acid(FA)dehydrogenation was investigated over several arene-ruthenium catalysts with various imidazolyl-,thiophenyl-and furyl-based ligands.The catalyst with an N-((1H-imidazol-2-yl)methyl)propan-2-amine ligand(Ru/L7)outperformed other catalysts in FA dehydrogenation at 90℃ in water.Furthermore,the developed process was scaled up by a factor of 10 without any loss in activity.Remarkably,Ru/L7 exhibited high robustness and long-term durability during reusability over 79 catalytic runs,achieving very high turnovers per Ru,releasing 37.6 L of gas(H_(2) and CO_(2))with a productivity rate of 15660 L(H_(2)+CO_(2))molRu−1 h^(−1)(∼7 gH_(2) gRu^(−1) h^(−1)).Advantageously,the Ru/L7 catalyst also promoted CO_(2)hydrogenation to formate at 80℃.Mechanistic insights were gained through KIE studies and via the identification of several catalytic intermediates involved in various steps of catalytic FA dehydrogenation and CO_(2)hydrogenation under catalytic and controlled reaction conditions.
基金funded by the project from the national natural science foundation of China(21805018 and 21878195)the applied basic research project of Sichuan science and technology department(2020YJ0134)the everest scientific research program of chengdu university of technology。
文摘Li-rich layered transition metal oxides are one of the most promising cathode materials for their high energy density.However,the cathodes usually suffer from severe potential dropping and capacity fading during cycling,which are associated with the surface oxygen release and accompanied by cation densification and structural collapse.Herein,an integrative approach of simultaneous constructing uniform 3d Fe-ion doping in the transition metal layer and Li-rich Li_(5)FeO_(4) shell to grab the oxygen and prevent interfacial side reactions is proposed.The introduction of Fe induces higher redox potential and stronger 3 d Fe-O_(2)p covalent bond,triggering reversible anionic redox via a reductive coupling mechanism.And the delithiated product of Li-rich Li_(5)FeO_(4) not only acts as a protective layer alleviating the side reactions but also enhances the surface kinetic property.With the benefit of promoted reversibility of oxygen redox and enhanced surface stability,the cathode exhibits high reversible capacity and superior cycle performance.Density function theory calculation indicates that the O_(2)p non-bonding state in the cathode incorporated with Fe sits at a lower energy band,resulting in higher energy storage voltage and improved oxygen stability.Consequently,the modified cathode exhibits a discharge specific capacity of 307 m A h g^(-1)(1 C=250 m A g^(-1)),coulombic efficiency of 82.09%in the initial cycle at 0.1 C and 88.34%capacity retention after 100 cycles at 1 C.The work illustrates a strategy that could simultaneously enhance oxygen redox reversibility and interface stability by constructing lattice bond coordination and delithiation induced protective layer to develop Li-rich materials with high reversible capacity and long lifespan.
基金supported by the Defense Advanced Research Projects Agency(N660012114034)H.L.acknowledges the scholarship provided by the Republic of Korea Navy(ROK Nawy)+1 种基金The design and fabrication of the micro-heater and chiral MRR are supported by AFOSR(FA9550-18-1-0300)S.K.O.acknowledges the Air Force Offce of Scientific Research(AFOSR)Multi-University Research Initiative(FA9550-21-1-0202)and AFOSR(FA9550-18-1-0235)。
文摘Exceptional points(EPs)have been extensively explored in mechanical,acoustic,plasmonic,and photonic systems.However,little is known about the role of EPs in tailoring the dynamic tunability of optical devices.A specific type of EPs known as chiral EPs has recently attracted much attention for controlling the flow of light and for building sensors with better responsivity.A recently demonstrated route to chiral EPs via lithographically defined symmetric Mie scatterers on the rim of resonators has not only provided the much-needed mechanical stability for studying chiral EPs,but also helped reduce losses originating from nanofabrication imperfections,facilitating the in-situ study of chiral EPs and their contribution to the dynamics and tunability of resonators.Here,we use asymmetric Mie scatterers to break the rotational symmetry of a microresonator,to demonstrate deterministic thermal tuning across a chiral EP,and to demonstrate EP-mediated chiral optical nonlinear response and efficient electro-optic tuning.Our results indicate asymmetric electro-optic modulation with up to 17 dB contrast at GHz and CMOS-compatible voltage levels.Such wafer-scale nano-manufacturing of chiral electro-optic modulators and the chiral EP-tailored tunning may facilitate new micro-resonator functionalities in quantum information processing,electromagnetic wave control,and optical interconnects.
基金supported by the National Natural Science Foundation of China(NSFC)(Grant Nos.62271243 and 62071215)the Fundamental Research Funds for the Central Universities+2 种基金the Jiangsu Provincial Key Research and Development Program(Grant No.BE2023084)the Priority Academic Program Development of Jiangsu Higher Education Institutionsthe Jiangsu Provincial Key Laboratory of Advanced Manipulating Technique of Electromagnetic Wave
文摘Hyperbolic polaritons are known to exist in materials with extreme anisotropy,exhibiting exotic optical properties that enable a plethora of unusual phenomena in the fields of polaritonics and photonics.However,achieving simultaneous low-dimensionality,high-speed controllability,and on-demand reconfigurability of the polaritons remains unexplored despite their excellent potential in light-matter interactions,photonic integrated circuits,and optoelectronic devices.Here,we propose a metasurface approach to integrating artificially engineered electromagnetic anisotropy with fast-controllable electronic elements,offering a new route to realize active topological polaritons.Experiments showcase the proposed reconfigurable metasurface can support real-time transitions of designer polaritons from elliptical to flat,and then to hyperbolic and circular isofrequency contours.Correspondingly,the in-plane surface wavefront undergoes the transitions from convex to collimating,concave,and eventually back to convex.By exploiting the topological variations in polariton dispersions,we observe intriguing phenomena of controllable field canalization and tunable planar focusing.Furthermore,we report the concept of a planar reconfigurable integrated polariton circuit by spatially tailoring the distributions of polariton isofrequency contours,unveiling rich dispersion engineering possibilities and active control capabilities.We may provide an inspiring platform for developing planar active plasmonic devices with potential applications in subdiffraction-resolution imaging,sensing,and information processing.
基金supported by the National Natural Science Foundation of China(Grant No.12164009)which is received by Xuefei Liu+1 种基金the Guizhou Science and Technology Foundation-ZK[2022]General 308,which is received by Xuefei Liuand the Graduate Research Fund Project of Guizhou Province(YJSKYJJ[2021]088),which is received by Tianyun Liu.
文摘We report here a theoretical study on 34 transition metal doped two-dimensional GaPS_(4) catalysts,denoted as transition metal transition metal@VS-GaPS_(4).Among them,the Pt@V_(S1)-GaPS_(4) single-atom catalyst is found to be stable with an ORR/OER overpotential of 0.59/0.41 V.Under the guidance of a volcano map,further biaxial strain engineering is adopted to tune the activity of Pt@V_(S1)-GaPS_(4) to the top of the volcano.The overpotentials of the OER/ORR are decreased to 0.37/0.33 V by applying a 3%tensile strain.Our results prove that Pt@V_(S1)-GaPS_(4) is an excellent candidate for OER/ORR bifunctional electro-catalysis.Moreover,bond angles and the highest occupied orbitals of the doped transition metal atoms can be used as descriptors to explain the underlying strain tunability mechanism.The machine learning method further predicts that the number of d electrons,the bond length and electronegativity are three main descriptors to determine the catalytic activity.
基金supported by the Natural Science Foundation of China(No.22261132512,22235001,22175020,and 22131005)Xiaomi Young Scholar Program,and University of Science and Technology Beijing.
文摘Interfacial charge transfer and active sites play important roles in the performance of heterogeneousphotocatalysts. Reticular chemistry in covalent organic frameworks (COFs) allows the construction of isomericarchitectures made of different donor and acceptor monomers for tuning the charge transferdynamics and active sites. Herein, five D-A dual-pore COFs were prepared from the reaction of naphthalene-2,6-diamine (electron donor) with different tetraaldehyde electron acceptors. Experimental resultsdisclosed that linker engineering, by changing the conjugation systems using heteroatoms of benzooxadiazole,benzothiadiazole, benzoselenadiazole, naphthothiadiazole, and naphthoselenadiazole, tuned theelectron-accepting capacity of the corresponding D-A COFs. Among the five samples, the naphthothiadiazole-derived COF demonstrated optimal charge transfer and active sites, exhibiting the highest hydrogenevolution rate of ca. 35 mmol g^(-1) h^(-1) in the presence of 3 wt% Pt under visible-light irradiation(>420 nm). This work illustrates linker engineering as a strategy for the simultaneous adjustment of interfacialcharge transfer and active sites to enhance the hydrogen generation efficiency, offering new vigorto develop the COF photocatalysts on the basis of reticular synthesis.
基金This study is supported by the Fundamental Research Funds for the Central Universities(2020XZZX002-07).This study is also supported by Major Scientific Project of Zhejiang Lab(2020MC0AD01).This work is also supported by the Natural Science Foundation of China(No.21776248 and 21676246)and the Zhejiang Provincial Natural Science Foundation of China(No.LR17B060003).
文摘The main bottleneck of electrolytic water for hydrogen production in alkaline media is the oxygen evolution reaction(OER)involving four-electron transfer.Designing highly efficient OER catalysts is attractive to accelerate this process.Monoclinic oxides have gained enormous interest as promising candidates for electrocatalysis due to their low cost and abundant storage.The introduction of transition metals into metal oxides to tune the electronic structure of active sites is regarded as one of the promising methods for enhancing OER performance.Herein,we designed a Fe_(2)(MoO_(4))_(3) catalyst by a spray pyrolysis strategy and enhanced the OER performance of Fe_(2)(MoO_(4))_(3) with Co doping,which displayed a low overpotential of 273 mV to drive 10 mA cm^(2).The octahedral Fe site engineering leads to higher reaction kinetics and more active site exposure.Density functional theory(DFT)calculations further revealed that the introduction of Co can reduce the energy barrier for the OER process and weaken the absorption of*-O.This work provides a new insight into the fabrication of monoclinic oxide electrocatalysts for OERs in alkaline media.
基金National Natural Science Foundation of China(62305303,62205164)Science and Technology Plan Project of Zhejiang(2022C01108)。
文摘Integrated high-linearity modulators are crucial for high dynamic-range microwave photonic(MWP)systems.Conventional linearization schemes usually involve the fine tuning of radio-frequency(RF)power distribution,which is rather inconvenient for practical applications and can hardly be implemented on the integrated photonics chip.In this paper,we propose an elegant scheme to linearize a silicon-based modulator in which the active tuning of RF power is eliminated.The device consists of two carrier-depletion-based Mach-Zehnder modulators(MZMs),which are connected in series by a 1×2 thermal optical switch(OS).The OS is used to adjust the ratio between the modulation depths of the two sub-MZMs.Under a proper ratio,the complementary third-order intermodulation distortion(IMD3)of the two sub-MZMs can effectively cancel each other out.The measured spurious-free dynamic ranges for IMD3 are 131,127,118,110,and 109 d B·Hz^(6∕7)at frequencies of 1,10,20,30,and 40 GHz,respectively,which represent the highest linearities ever reached by the integrated modulator chips on all available material platforms.
基金We gratefully acknowledge the funding by DFG(SPP1391,FOR730,and GI 269/11-1),BMBF(FARADAY,FKZ 13N12443)MWK,Baden-Wurttemberg Stiftung and ERC(ComplexPlas)JYC and DD also acknowledge support from Carl-Zeiss-Stiftung.
文摘We experimentally demonstrate an ultra-thin plasmonic optical rotator in the visible regime that induces a polarization rotation that is continuously tunable and switchable by an external magnetic field.The rotator is a magneto-plasmonic hybrid structure consisting of a magneto-optical EuSe slab and a one-dimensional plasmonic gold grating.At low temperatures,EuSe possesses a large Verdet constant and exhibits Faraday rotation,which does not saturate over a regime of several Tesla.By combining these properties with plasmonic Faraday rotation enhancement,a large tuning range of the polarization rotation of up to 8.4° for a film thickness of 220 nm is achieved.Furthermore,through experiments and simulations,we demonstrate that the unique dispersion properties of the structure enable us to tailor the wavelengths of the tunable polarization rotation to arbitrary spectral positions within the transparency window of the magneto-optical slab.The demonstrated concept might lead to important,highly integrated,non-reciprocal,photonic devices for light modulation,optical isolation,and magnetic field optical sensing.The simple fabrication of EuSe nanostructures by physical vapor deposition opens the way for many potentially interesting magneto-plasmonic systems and three-dimensional magneto-optical metamaterials.
文摘This paper presents a low power tunable active inductor and RF band pass filter suitable for multiband RF front end circuits. The active inductor circuit uses the PMOS cascode structure as the negative transconductor of a gyrator to reduce the noise voltage. Also, this structure provides possible negative resistance to reduce the inductor loss with wide inductive bandwidth and high resonance frequency. The RF band pass filter is realized using the proposed active inductor with suitable input and output buffer stages. The tuning of the center frequency for multiband operation is achieved through the controllable current source. The designed active inductor and RF band pass filter are simulated in 180 nm and 45 nm CMOS process using the Synopsys HSPICE simulation tool and their performances are compared. The parameters, such as resonance frequency, tuning capability, noise and power dissipation, are analyzed for these CMOS technologies and discussed. The design of a third order band pass filter using an active inductor is also presented.
