Although there are numerous optical spectroscopy techniques and methods that have been used to extract the fundamental bandgap of a semiconductor,most of them belong to one of these three approaches:(1)the excitonic a...Although there are numerous optical spectroscopy techniques and methods that have been used to extract the fundamental bandgap of a semiconductor,most of them belong to one of these three approaches:(1)the excitonic absorption,(2)modulation spectroscopy,and(3)the most widely used Tauc-plot.The excitonic absorption is based on a many-particle theory,which is physically the most correct approach,but requires more stringent crystalline quality and appropriate sample preparation and experimental implementation.The Tauc-plot is based on a single-particle theo⁃ry that neglects the many-electron effects.Modulation spectroscopy analyzes the spectroscopy features in the derivative spectrum,typically,of the reflectance and transmission under an external perturbation.Empirically,the bandgap ener⁃gy derived from the three approaches follow the order of E_(ex)>E_(MS)>E_(TP),where three transition energies are from exci⁃tonic absorption,modulation spectroscopy,and Tauc-plot,respectively.In principle,defining E_(g) as the single-elec⁃tron bandgap,we expect E_(g)>E_(ex),thus,E_(g)>E_(TP).In the literature,E_(TP) is often interpreted as E_(g),which is conceptual⁃ly problematic.However,in many cases,because the excitonic peaks are not readily identifiable,the inconsistency be⁃tween E_(g) and E_(TP) becomes invisible.In this brief review,real world examples are used(1)to illustrate how excitonic absorption features depend sensitively on the sample and measurement conditions;(2)to demonstrate the differences between E_(ex),E_(MS),and E_(TP) when they can be extracted simultaneously for one sample;and(3)to show how the popular⁃ly adopted Tauc-plot could lead to misleading results.Finally,it is pointed out that if the excitonic absorption is not ob⁃servable,the modulation spectroscopy can often yield a more useful and reasonable bandgap than Tauc-plot.展开更多
Conjugated microporous polymers(CMPs) with tunable bandgaps have attracted increasing attention for photocatalytic hydrogen evolution. However, the synthesis of CMPs usually needs expensive metal-based catalysts. Here...Conjugated microporous polymers(CMPs) with tunable bandgaps have attracted increasing attention for photocatalytic hydrogen evolution. However, the synthesis of CMPs usually needs expensive metal-based catalysts. Herein, we report a metal-free synthetic route to fabricate pyridyl conjugated microporous polymers(PCMPs) via a condensed polymerization between aldehyde and aryl ketone monomers. The PCMPs show widely tunable specific surface areas(347–418 m^(2)/g), which were controlled via changing the used monomers. The PCMPs synthesized using monomers of dialdehyde and diacetylbenzene(diacetylpyridine) in the presence of pyridine exhibited the highest visible-light driven hydrogen evolution rate(9.56 μmol/h). These novel designed PCMPs provide wide adaptability to current materials designed for high-performance photocatalysts in different applications.展开更多
The concept of local resonance phononic crystals proposed in recent years provides a new chance for theoretical and technical breakthroughs in the structural vibration reduction.In this paper,a novel sandwich-like pla...The concept of local resonance phononic crystals proposed in recent years provides a new chance for theoretical and technical breakthroughs in the structural vibration reduction.In this paper,a novel sandwich-like plate model with local resonator to acquire specific low-frequency bandgaps is proposed.The core layer of the present local resonator is composed by the simply supported overhanging beam,linear spring and mass block,and well connected with the upper and lower surface panels.The simply supported overhanging beam is free at right end,and an additional linear spring is added at the left end.The wave equation is established based on the Hamilton principle,and the bending wave bandgap is further obtained.The theoretical results are verified by the COMSOL finite element software.The bandgaps and vibration characteristics of the local resonance sandwich-like plate are studied in detail.The factors which could have effects on the bandgap characteristics,such as the structural damping,mass of vibrator,position of vibrator,bending stiffness of the beam,and the boundary conditions of the sandwich-like plates,are analyzed.The result shows that the stopband is determined by the natural frequency of the resonator,the mass ratio of the resonator,and the surface panel.It shows that the width of bandgap is greatly affected by the damping ratio of the resonator.Finally,it can also be found that the boundary conditions can affect the isolation efficiency.展开更多
Many ionocovalent oxide materials are either semiconducting or insulating in nature.One of the most im- portant quantities characterising these materials,therefore,is the bandgap energy.The thermodynamic ap- proaches ...Many ionocovalent oxide materials are either semiconducting or insulating in nature.One of the most im- portant quantities characterising these materials,therefore,is the bandgap energy.The thermodynamic ap- proaches to the bandgaps of oxides are briefly described and some interracial phenomena with oxides are pres- ented.The standard electrode potentials of oxide electrodes and the heterogeneous catalytic behaviours of the oxides as well as the wetting and adhesion in liquid metal/oxide systems can be closely related to the bandgap energies of the oxides.The interfacial phenomena involving the ionocovalent oxides are associated with the electronic processes.展开更多
The narrow attenuation bands of traditional marine structures have long been a challenge in mitigating water waves.In this paper,a metastructure(MS)composed of floating periodic pontoons is proposed for broadband wate...The narrow attenuation bands of traditional marine structures have long been a challenge in mitigating water waves.In this paper,a metastructure(MS)composed of floating periodic pontoons is proposed for broadband water wave attenuation.The interaction of surface gravity waves with the MS is investigated using linear wave theory.The potential solutions of water waves by the MS with a finite array are developed by using the eigenfunction expansion matching method(EEMM),and the band structure of the MS is calculated by the transfer matrix method(TMM),in which the evanescent modes of waves are considered.The solution is verified against the existing numerical result for a special case.Based on the present solution,the association between Bragg resonance reflection and Bloch bandgaps is examined,the effects of pontoon geometry are analyzed,and the comparison between floating MS and bottom-mounted periodic structures is conducted.A computational fluid dynamics(CFD)model is further developed to assess the structures in practical fluid environments,and the floating MS presents excellent wave attenuation performance.The study presented here may provide a promising solution for protecting the coast and offshore structures.展开更多
A gradient metamaterial with varying-stiffness local resonators is proposed to open the multiple bandgaps and further form a broad fusion bandgap.First,three local resonators with linearly increasing stiffness are per...A gradient metamaterial with varying-stiffness local resonators is proposed to open the multiple bandgaps and further form a broad fusion bandgap.First,three local resonators with linearly increasing stiffness are periodically attached to the spring-mass chain to construct the gradient metamaterial.The dispersion relation is then derived based on Bloch's theorem to reveal the fusion bandgap theoretically.The dynamic characteristic of the finite spring-mass chain is investigated to validate the fusion of multiple bandgaps.Finally,the effects of the design parameters on multiple bandgaps are discussed.The results show that the metamaterial with a non-uniform stiffness gradient pattern is capable of opening a broad fusion bandgap and effectively attenuating the longitudinal waves within a broad frequency region.展开更多
One-dimensional photonic crystals (1D PhCs) have a unique ability to control the propagation of light waves, however certain classes of 1D oxides remain relatively unexplored for use as PhCs. Specifically, there has n...One-dimensional photonic crystals (1D PhCs) have a unique ability to control the propagation of light waves, however certain classes of 1D oxides remain relatively unexplored for use as PhCs. Specifically, there has not been a comparative study of the three different 1D PhC structures to compare the influence of layer thickness, number, and refractive index on the ability of the PhCs to control light transmission. Herein, we use the transfer matrix method (TMM) to theoretically examine the transmission of 1D PhCs composed of layers of TiO<sub>2</sub>/SiO<sub>2</sub>, TiO<sub>2</sub>/SnO<sub>2</sub>, SiO<sub>2</sub>/SnO<sub>2</sub>, and combinations of the three with various top and bottom layer thicknesses to cover a substantial region of the electromagnetic spectrum (UV to NIR). With increasing layer numbers for TiO<sub>2</sub>/SiO<sub>2</sub> and SiO<sub>2</sub>/SnO<sub>2</sub>, the edges became sharper and wider and the photonic bandgap width increased. Moreover, we demonstrated that PhCs with significantly thick TiO<sub>2</sub>/SiO<sub>2</sub> layers had a high transmittance for a wide bandgap, allowing for wide-band optical filter applications. These different PhC architectures could enable a variety of applications, depending on the properties needed.展开更多
Applying distinctive designs to mechanical metamaterials is an effective way to achieve bandgap generation,widening and movement.In this paper,the bandgaps of metamaterials are tailored through the unique design of be...Applying distinctive designs to mechanical metamaterials is an effective way to achieve bandgap generation,widening and movement.In this paper,the bandgaps of metamaterials are tailored through the unique design of bending,folding,and twisting units and applied to the vibration-damping design of a marine water pump base.It is found that the bending operation generates a new complete bandgap and significantly enlarges the directional bandgap in the low-frequency region;the folding operation expands the directional bandgap in the high-frequency region;and the twisting operation generates and broadens the directional bandgap in the mid-frequency region.The application of the negative Poisson’s ratio star-shaped metamaterial(NPRSM)cell,with a 60°bending angle,to vibration damping in a meta-material ship pump base is presented.The new base achieved vibration attenuation of 43.435 dB and 60.282 dB over the bandgap ranges of 517.95 Hz-668.36 Hz and 916.98 Hz-965.03 Hz,respectively.In addition,the weight of the new base was reduced by 36.19% compared to the conventional pump base,which is merely capable of bearing loads.This study provides an innovative design method for broadband vibration isolation and demonstrates the promising future of mechanical metamaterials in practical engineering applications.展开更多
Since opening sizable bandgaps in bilayer graphene （BLG） was proven possible, BLG has attracted considerable attention as a promising high-mobility candidate material for many electronic and optoelectronic applicati...Since opening sizable bandgaps in bilayer graphene （BLG） was proven possible, BLG has attracted considerable attention as a promising high-mobility candidate material for many electronic and optoelectronic applications. However, the bandgaps observed in the transport experiments reported in the literature are far smaller than both the theoretical predictions and the bandgaps extracted from optical measurements. In this study, we investigate the factors preventing the formation of large bandgaps and demonstrate that a -200-meV transport bandgap can be opened in BLG by scaling the gate dielectric and employing a ribbon channel to suppress the percolative transport. This is the largest transport bandgap that has been achieved in BLG to date.展开更多
This paper studies the bandgap characteristics of a locally resonant metamaterial beam with time delays.The dispersion relations are addressed based on transfer matrix method.The governing equations of motion of the b...This paper studies the bandgap characteristics of a locally resonant metamaterial beam with time delays.The dispersion relations are addressed based on transfer matrix method.The governing equations of motion of the beam in the frequency domain are given according to spectral element method.The amplitude-frequency responses of the forced beam are determined by solving linear algebraic equations.The obtained results show that the time-delayed feedback control has great relationships with the location,width and number of the bandgaps.It is interesting that the time delay can change the direction of the movement of the bandgap and give rise to the generation of multiple bandgaps.The influences of different combinations of control parameters on the bandgap properties are shown,such as broadening effects.展开更多
To address the increasing demand for massive data storage and processing,brain-inspired neuromorphic comput-ing systems based on artificial synaptic devices have been actively developed in recent years.Among the vario...To address the increasing demand for massive data storage and processing,brain-inspired neuromorphic comput-ing systems based on artificial synaptic devices have been actively developed in recent years.Among the various materials inves-tigated for the fabrication of synaptic devices,silicon carbide(SiC)has emerged as a preferred choices due to its high electron mobility,superior thermal conductivity,and excellent thermal stability,which exhibits promising potential for neuromorphic applications in harsh environments.In this review,the recent progress in SiC-based synaptic devices is summarized.Firstly,an in-depth discussion is conducted regarding the categories,working mechanisms,and structural designs of these devices.Subse-quently,several application scenarios for SiC-based synaptic devices are presented.Finally,a few perspectives and directions for their future development are outlined.展开更多
This paper introduces a high-precision bandgap reference(BGR)designed for battery management systems(BMS),fea-turing an ultra-low temperature coefficient(TC)and line sensitivity(LS).The BGR employs a current-mode sche...This paper introduces a high-precision bandgap reference(BGR)designed for battery management systems(BMS),fea-turing an ultra-low temperature coefficient(TC)and line sensitivity(LS).The BGR employs a current-mode scheme with chopped op-amps and internal clock generators to eliminate op-amp offset.A low dropout regulator(LDO)and a pre-regula-tor enhance output driving and LS,respectively.Curvature compensation enhances the TC by addressing higher-order nonlinear-ity.These approaches,effective near room temperature,employs trimming at both 20 and 60°C.When combined with fixed cur-vature correction currents,it achieves an ultra-low TC for each chip.Implemented in a CMOS 180 nm process,the BGR occu-pies 0.548 mm²and operates at 2.5 V with 84μA current draw from a 5 V supply.An average TC of 2.69 ppm/℃ with two-point trimming and 0.81 ppm/℃ with multi-point trimming are achieved over the temperature range of-40 to 125℃.It accommo-dates a load current of 1 mA and an LS of 42 ppm/V,making it suitable for precise BMS applications.展开更多
Acceptor-donor-acceptor(A-D-A)type molecules,of which the novel non-fused azacyclic end-group pyrazoli-nones were modified with chlorine substitution on the phenyl ring,were synthesized.The non-fused azacyclic end-gro...Acceptor-donor-acceptor(A-D-A)type molecules,of which the novel non-fused azacyclic end-group pyrazoli-nones were modified with chlorine substitution on the phenyl ring,were synthesized.The non-fused azacyclic end-group py-razolinones have the advantages of simple synthesis steps,low cost and environmental friendliness,compared to the classical end-group dicyanomethyleneindianone.The properties of the synthesized A-D-A type molecules with non-fused azacyclic end groups were characterized by theoretical calculation,UV-vis absorption,cyclic voltammetry,X-ray diffraction and space charge limited current.It is shown that the strong UV-vis absorptions of the synthesized A-D-A type molecules are located in the wavelength range of 500~700 nm,with a moderate band gap of nearly 1.7 eV.At the same time,the influence of end-group chlorination on the properties of A-D-A type molecules was compared and explored.It is proven that this kind of A-D-A type molecule with non-fused azacyclic end groups has the potential to be applied as interfacial modified layer of the active layer in perovskite solar cell devices.展开更多
This study introduces a comprehensive theoretical framework for accurately calculating the electronic band-structure of strained long-wavelength InAs/GaSb type-Ⅱsuperlattices.Utilizing an eight-band k·p Hamilto⁃...This study introduces a comprehensive theoretical framework for accurately calculating the electronic band-structure of strained long-wavelength InAs/GaSb type-Ⅱsuperlattices.Utilizing an eight-band k·p Hamilto⁃nian in conjunction with a scattering matrix method,the model effectively incorporates quantum confinement,strain effects,and interface states.This robust and numerically stable approach achieves exceptional agreement with experimental data,offering a reliable tool for analyzing and engineering the band structure of complex multi⁃layer systems.展开更多
The wide band gap characteristics of gallium oxide make it very suitable for the preparation of solar-blind ultra-violet photodetectors.The responsivity of ultraviolet photodetectors based on thin films is often low.H...The wide band gap characteristics of gallium oxide make it very suitable for the preparation of solar-blind ultra-violet photodetectors.The responsivity of ultraviolet photodetectors based on thin films is often low.However,nanomaterials have excellent photoelectric properties in device applications due to the high stability brought by high specific surface area and high crystal quality.Here,we successfully depositedβ-Ga_(2)O_(3) nanopores on the double-pass ordered porous AAO tem-plate by PLD.The porous AAO template is used as the growth space of nanomaterials,and the gallium oxide material is filled into the pores of the template to form a nanotube structure.By optimizing the preparation process,the relationship be-tween the performance of gallium oxide nanopores and the growth time was studied in depth.With the increase of growth time,the responsivity of the detector was improved.The rise timeτr=0.7 s,the decay timeτ_(d)=1.3 s,and the responsivity reached 4.63 mA·W^(-1),which was higher than 2.24 mA·W^(-1)of the responsivity of silicon-based gallium oxide nanorods.展开更多
Reducing the vibration transmission in beams is of significant interest,as beams are among the most widely used basic structures in numerous practical engineering applications.However,achieving broadband suppression o...Reducing the vibration transmission in beams is of significant interest,as beams are among the most widely used basic structures in numerous practical engineering applications.However,achieving broadband suppression of multi-polarization low-frequency vibration in beams presents a challenge.This study proposes a single-phase multi-resonant metabeam,which consists of a host beam with subwavelength arrays of tunable local resonators.These resonators exhibit adjustable multi-polarization resonant modes that strongly couple with the host beam,enabling simultaneous suppression of multi-type waves over a broad frequency range.The theoretical analysis demonstrates that under the fixed total added-mass ratio(γ_(total)=1.5),the tailored frequency spacing(δ=25-50 Hz)and the controlled loss factor(η=0.03–0.07)act synergistically to broaden bandgaps through resonant zone overlapping and attenuation peak smoothing.The experimental validation with monolithic three-dimensional(3D)-printed specimens confirms the efficacy of this design in multi-polarization vibration control within a deepsubwavelength bandgap,opening a new avenue for designing multi-polarization vibration suppression structures.展开更多
Low energy-storage density and inferior thermal stability are a long-term obstacle to the advancement of pulse power devices.Herein,these concerns are addressed by improving bandgap and fabricating polar nanoregions,a...Low energy-storage density and inferior thermal stability are a long-term obstacle to the advancement of pulse power devices.Herein,these concerns are addressed by improving bandgap and fabricating polar nanoregions,and the superior high efficiency of~86.7%,excellent thermal stability of~2%(31-160℃)and energy density of~6.8 J·cm^(-3)are achieved in Bi_(0.5)Na_(0.5)TiO_(3)-La_(0.1)Sr_(0.8)TiO_(3)-δ-NaNbO_(3)ceramics.The high breakdown strength(460 kV·cm^(-1))is ascribed to the broadened bandgap and refined grain.Slim ferroelectric loops originate from the construction of polar nanoregions(PNRs)in a pseudocubic matrix,and transmission electron microscope and piezoelectric force microscope measurements reveal the occurrence of PNRs.The phase-field stimulation and UV-Vis spectrophotometer measurement reveal that the increased grain boundary density and bandgap are beneficial for promoting breakdown strength.The strategy provides an efficient path to prepare Bi_(0.5)Na_(0.5)TiO_(3)La_(0.1)Sr_(0.8)TiO_(3)-δ-based ceramics with superior efficiency,high energy density and outstanding thermal stability.展开更多
With the acceleration of urbanization,environmental vibration and noise pollution have become increasingly severe,and traditional vibration and noise reduction technologies are insufficient to meet current vibration c...With the acceleration of urbanization,environmental vibration and noise pollution have become increasingly severe,and traditional vibration and noise reduction technologies are insufficient to meet current vibration control requirements.This study,based on locally resonant theory,designed a novel local resonance periodic block(LRPB).Using the plane wave expansion method(PWEM)and the finite element method(FEM),this study investigated the bandgap characteristics,formation mechanisms,and vibration and acoustic performance of an LRPB under different periodic structures and material selection.The vibration reduction and noise reduction performance of LRPB has been validated through the Qingdao metro project.The research results show that the LRPB is superior to other periodic structures in terms of wide bandgap.Furthermore,configuring soft scatterer material,increasing the unit size,enhancing the material filling rate,and adopting a honeycomb arrangement can effectively reduce bandgap frequency.In structural design,non-high symmetry demonstrates greater advantages.In a study of a subway tunnel,the LRPB demonstrated superior vibration and noise mitigation performance compared to wave impeding block(WIB),thereby demonstrating potential for use in the field of vibration and noise reduction with regard to structures.展开更多
Lead-tin(Pb-Sn)perovskites with an ideal bandgap of 1.34-1.40 eV show great promise in perovskite solar cells(PSCs).Recently,to address the environmental pollution and Sn^(2+)oxidation problems of dimethyl sulfoxide,m...Lead-tin(Pb-Sn)perovskites with an ideal bandgap of 1.34-1.40 eV show great promise in perovskite solar cells(PSCs).Recently,to address the environmental pollution and Sn^(2+)oxidation problems of dimethyl sulfoxide,methylammonium acetate(MAAc)ionic liquid has been developed as an alternative to fabricate ideal bandgap MAPb_(0.7)Sn_(0.3)I_(3)(1.36 eV)film via hot-casting in air.However,the spontaneous crystallization of Pb-Sn perovskite initiated by heat-induced supersaturation is fast and random,setting critical challenges in regulating crystal growth during the film-forming process.Herein,a lattice activation strategy is developed to control the crystallization dynamics of MAPb_(0.7)Sn_(0.3)I_(3)in MAAc to produce films with micrometer-sized grains in air.FA is shown to activate the crystal lattice that facilitates the formation of intermediates and balances the crystal growth of MAPb_(0.7)Sn_(0.3)I_(3),producing films with a grain size of 2.78±0.17μm.Furthermore,4-fluoro-phenethylammonium and phenethylammonium are adopted to passivate the defects in the film and promote the energy level alignment at the top interface,respectively.The optimized PSC device achieved an efficiency of 18.24%with a short-circuit current of 29.84 mA/cm^(2),which are both the highest values in 1.36 eV Pb-Sn PSCs to date.Notably,the unencapsulated devices show excellent storage and air stability under various conditions.展开更多
Hydrogenated two-dimensional(2D)materials have gained significant attention due to their tunable properties,which can be engineered through various functionalization techniques.This review discusses hydrogenated Xenes...Hydrogenated two-dimensional(2D)materials have gained significant attention due to their tunable properties,which can be engineered through various functionalization techniques.This review discusses hydrogenated Xenes,a new class of fully hydrogenated mono-elemental 2D materials,including graphane,germanane,silicane,and stanane.Hydrogenation enhances the properties of Xenes,making them transparent,mechanically strong,electrically conductive,and rare.These materials off er a unique combination of characteristics that make them highly desirable for a variety of advanced applications in energy storage,organic electronics,and optoelectronics.Xenes such as silicane and germanane are semiconductors with tunable bandgaps,making them ideal for use in transistors,logic circuits,and sensors.Their electronic and optical properties can be finely adjusted,allowing them to be used in high-performance devices like LEDs,solar cells,and photodetectors.Furthermore,hydrogenated Xenes show potential in applications like batteries,supercapacitors,hydrogen storage,piezoelectricity,and biosensing,owing to their high surface area and versatility.This review also explores the impact of various hydrogenation techniques,including plasma treatment,wet chemical methods,and electrochemical hydrogenation,on the electronic,mechanical,thermal,optical,and magnetic properties of these materials.Advanced characterization techniques,such as X-ray absorption spectroscopy(XANES),have provided valuable insights into the electronic structure and bonding environments of these materials.Finally,the paper highlights the challenges and limitations of hydrogenation,including structural instability and environmental concerns,while discussing the future prospects and advancements needed to harness the full potential of hydrogenated 2D materials.This review serves as a comprehensive resource for researchers aiming to explore the applications of hydrogenated Xenes in next-generation technologies.展开更多
基金Supported by Bissell Distinguished Professor Endowment Fund at UNC-Charlotte。
文摘Although there are numerous optical spectroscopy techniques and methods that have been used to extract the fundamental bandgap of a semiconductor,most of them belong to one of these three approaches:(1)the excitonic absorption,(2)modulation spectroscopy,and(3)the most widely used Tauc-plot.The excitonic absorption is based on a many-particle theory,which is physically the most correct approach,but requires more stringent crystalline quality and appropriate sample preparation and experimental implementation.The Tauc-plot is based on a single-particle theo⁃ry that neglects the many-electron effects.Modulation spectroscopy analyzes the spectroscopy features in the derivative spectrum,typically,of the reflectance and transmission under an external perturbation.Empirically,the bandgap ener⁃gy derived from the three approaches follow the order of E_(ex)>E_(MS)>E_(TP),where three transition energies are from exci⁃tonic absorption,modulation spectroscopy,and Tauc-plot,respectively.In principle,defining E_(g) as the single-elec⁃tron bandgap,we expect E_(g)>E_(ex),thus,E_(g)>E_(TP).In the literature,E_(TP) is often interpreted as E_(g),which is conceptual⁃ly problematic.However,in many cases,because the excitonic peaks are not readily identifiable,the inconsistency be⁃tween E_(g) and E_(TP) becomes invisible.In this brief review,real world examples are used(1)to illustrate how excitonic absorption features depend sensitively on the sample and measurement conditions;(2)to demonstrate the differences between E_(ex),E_(MS),and E_(TP) when they can be extracted simultaneously for one sample;and(3)to show how the popular⁃ly adopted Tauc-plot could lead to misleading results.Finally,it is pointed out that if the excitonic absorption is not ob⁃servable,the modulation spectroscopy can often yield a more useful and reasonable bandgap than Tauc-plot.
基金supported by the National Natural Science Foundation of China (Nos. 52103024, 52073046, 51873036 and51673039)the Program of Shanghai Academic Research Leader(No. 21XD1420200)+5 种基金the Shanghai Shuguang Program (No. 19SG28)the Chang Jiang Scholar Program (No. Q2019152)the Shanghai Pujiang Talent Program (No. 20PJ1400600)the Shanghai Natural Science Foundation (Nos. 22ZR1401600 and 19ZR1470900)the Fundamental Research Funds for the Central Universities(No. 2232021D-01)the Fundamental Research Funds for the Central Universities and Graduate Student Innovation Fund of Donghua University (No. CUSF-DH-D-2019024)。
文摘Conjugated microporous polymers(CMPs) with tunable bandgaps have attracted increasing attention for photocatalytic hydrogen evolution. However, the synthesis of CMPs usually needs expensive metal-based catalysts. Herein, we report a metal-free synthetic route to fabricate pyridyl conjugated microporous polymers(PCMPs) via a condensed polymerization between aldehyde and aryl ketone monomers. The PCMPs show widely tunable specific surface areas(347–418 m^(2)/g), which were controlled via changing the used monomers. The PCMPs synthesized using monomers of dialdehyde and diacetylbenzene(diacetylpyridine) in the presence of pyridine exhibited the highest visible-light driven hydrogen evolution rate(9.56 μmol/h). These novel designed PCMPs provide wide adaptability to current materials designed for high-performance photocatalysts in different applications.
基金the National Natural Science Foundation of China(Nos.11872127,11832002,11732005)Qin Xin Talents Cultivation Program of Beijing Information Science and Technology University(No.QXTCP A201901)the Project High-Level Innovative Team Building Plan for Beijing Municipal Colleges and Universities(No.IDHT20180513)。
文摘The concept of local resonance phononic crystals proposed in recent years provides a new chance for theoretical and technical breakthroughs in the structural vibration reduction.In this paper,a novel sandwich-like plate model with local resonator to acquire specific low-frequency bandgaps is proposed.The core layer of the present local resonator is composed by the simply supported overhanging beam,linear spring and mass block,and well connected with the upper and lower surface panels.The simply supported overhanging beam is free at right end,and an additional linear spring is added at the left end.The wave equation is established based on the Hamilton principle,and the bending wave bandgap is further obtained.The theoretical results are verified by the COMSOL finite element software.The bandgaps and vibration characteristics of the local resonance sandwich-like plate are studied in detail.The factors which could have effects on the bandgap characteristics,such as the structural damping,mass of vibrator,position of vibrator,bending stiffness of the beam,and the boundary conditions of the sandwich-like plates,are analyzed.The result shows that the stopband is determined by the natural frequency of the resonator,the mass ratio of the resonator,and the surface panel.It shows that the width of bandgap is greatly affected by the damping ratio of the resonator.Finally,it can also be found that the boundary conditions can affect the isolation efficiency.
文摘Many ionocovalent oxide materials are either semiconducting or insulating in nature.One of the most im- portant quantities characterising these materials,therefore,is the bandgap energy.The thermodynamic ap- proaches to the bandgaps of oxides are briefly described and some interracial phenomena with oxides are pres- ented.The standard electrode potentials of oxide electrodes and the heterogeneous catalytic behaviours of the oxides as well as the wetting and adhesion in liquid metal/oxide systems can be closely related to the bandgap energies of the oxides.The interfacial phenomena involving the ionocovalent oxides are associated with the electronic processes.
基金Project supported by the National Natural Science Foundation of China(No.12272128)the Natural Science Foundation of Jiangsu Province of China(No.BK20243019)。
文摘The narrow attenuation bands of traditional marine structures have long been a challenge in mitigating water waves.In this paper,a metastructure(MS)composed of floating periodic pontoons is proposed for broadband water wave attenuation.The interaction of surface gravity waves with the MS is investigated using linear wave theory.The potential solutions of water waves by the MS with a finite array are developed by using the eigenfunction expansion matching method(EEMM),and the band structure of the MS is calculated by the transfer matrix method(TMM),in which the evanescent modes of waves are considered.The solution is verified against the existing numerical result for a special case.Based on the present solution,the association between Bragg resonance reflection and Bloch bandgaps is examined,the effects of pontoon geometry are analyzed,and the comparison between floating MS and bottom-mounted periodic structures is conducted.A computational fluid dynamics(CFD)model is further developed to assess the structures in practical fluid environments,and the floating MS presents excellent wave attenuation performance.The study presented here may provide a promising solution for protecting the coast and offshore structures.
基金supported by the National Natural Science Foundation of China(Nos.12122206,52175125,12272129,12304309,and 12302039)the Zhejiang Provincial Natural Science Foundation of China(No.LQ24A020006)+1 种基金the Hong Kong Scholars Program of China(No.XJ2022012)the Natural Science Foundation of Hunan Province of China(No.2024JJ4004)。
文摘A gradient metamaterial with varying-stiffness local resonators is proposed to open the multiple bandgaps and further form a broad fusion bandgap.First,three local resonators with linearly increasing stiffness are periodically attached to the spring-mass chain to construct the gradient metamaterial.The dispersion relation is then derived based on Bloch's theorem to reveal the fusion bandgap theoretically.The dynamic characteristic of the finite spring-mass chain is investigated to validate the fusion of multiple bandgaps.Finally,the effects of the design parameters on multiple bandgaps are discussed.The results show that the metamaterial with a non-uniform stiffness gradient pattern is capable of opening a broad fusion bandgap and effectively attenuating the longitudinal waves within a broad frequency region.
文摘One-dimensional photonic crystals (1D PhCs) have a unique ability to control the propagation of light waves, however certain classes of 1D oxides remain relatively unexplored for use as PhCs. Specifically, there has not been a comparative study of the three different 1D PhC structures to compare the influence of layer thickness, number, and refractive index on the ability of the PhCs to control light transmission. Herein, we use the transfer matrix method (TMM) to theoretically examine the transmission of 1D PhCs composed of layers of TiO<sub>2</sub>/SiO<sub>2</sub>, TiO<sub>2</sub>/SnO<sub>2</sub>, SiO<sub>2</sub>/SnO<sub>2</sub>, and combinations of the three with various top and bottom layer thicknesses to cover a substantial region of the electromagnetic spectrum (UV to NIR). With increasing layer numbers for TiO<sub>2</sub>/SiO<sub>2</sub> and SiO<sub>2</sub>/SnO<sub>2</sub>, the edges became sharper and wider and the photonic bandgap width increased. Moreover, we demonstrated that PhCs with significantly thick TiO<sub>2</sub>/SiO<sub>2</sub> layers had a high transmittance for a wide bandgap, allowing for wide-band optical filter applications. These different PhC architectures could enable a variety of applications, depending on the properties needed.
文摘Applying distinctive designs to mechanical metamaterials is an effective way to achieve bandgap generation,widening and movement.In this paper,the bandgaps of metamaterials are tailored through the unique design of bending,folding,and twisting units and applied to the vibration-damping design of a marine water pump base.It is found that the bending operation generates a new complete bandgap and significantly enlarges the directional bandgap in the low-frequency region;the folding operation expands the directional bandgap in the high-frequency region;and the twisting operation generates and broadens the directional bandgap in the mid-frequency region.The application of the negative Poisson’s ratio star-shaped metamaterial(NPRSM)cell,with a 60°bending angle,to vibration damping in a meta-material ship pump base is presented.The new base achieved vibration attenuation of 43.435 dB and 60.282 dB over the bandgap ranges of 517.95 Hz-668.36 Hz and 916.98 Hz-965.03 Hz,respectively.In addition,the weight of the new base was reduced by 36.19% compared to the conventional pump base,which is merely capable of bearing loads.This study provides an innovative design method for broadband vibration isolation and demonstrates the promising future of mechanical metamaterials in practical engineering applications.
文摘Since opening sizable bandgaps in bilayer graphene （BLG） was proven possible, BLG has attracted considerable attention as a promising high-mobility candidate material for many electronic and optoelectronic applications. However, the bandgaps observed in the transport experiments reported in the literature are far smaller than both the theoretical predictions and the bandgaps extracted from optical measurements. In this study, we investigate the factors preventing the formation of large bandgaps and demonstrate that a -200-meV transport bandgap can be opened in BLG by scaling the gate dielectric and employing a ribbon channel to suppress the percolative transport. This is the largest transport bandgap that has been achieved in BLG to date.
文摘This paper studies the bandgap characteristics of a locally resonant metamaterial beam with time delays.The dispersion relations are addressed based on transfer matrix method.The governing equations of motion of the beam in the frequency domain are given according to spectral element method.The amplitude-frequency responses of the forced beam are determined by solving linear algebraic equations.The obtained results show that the time-delayed feedback control has great relationships with the location,width and number of the bandgaps.It is interesting that the time delay can change the direction of the movement of the bandgap and give rise to the generation of multiple bandgaps.The influences of different combinations of control parameters on the bandgap properties are shown,such as broadening effects.
基金supported by the Natural Science Foundation of Zhejiang Province(Grant No.LQ24F040007)the National Natural Science Foundation of China(Grant No.U22A2075)the Opening Project of State Key Laboratory of Polymer Materials Engineering(Sichuan University)(Grant No.sklpme2024-1-21).
文摘To address the increasing demand for massive data storage and processing,brain-inspired neuromorphic comput-ing systems based on artificial synaptic devices have been actively developed in recent years.Among the various materials inves-tigated for the fabrication of synaptic devices,silicon carbide(SiC)has emerged as a preferred choices due to its high electron mobility,superior thermal conductivity,and excellent thermal stability,which exhibits promising potential for neuromorphic applications in harsh environments.In this review,the recent progress in SiC-based synaptic devices is summarized.Firstly,an in-depth discussion is conducted regarding the categories,working mechanisms,and structural designs of these devices.Subse-quently,several application scenarios for SiC-based synaptic devices are presented.Finally,a few perspectives and directions for their future development are outlined.
基金supported by the National Natural Science Foundation of China(NSFC)under grant No.62204235。
文摘This paper introduces a high-precision bandgap reference(BGR)designed for battery management systems(BMS),fea-turing an ultra-low temperature coefficient(TC)and line sensitivity(LS).The BGR employs a current-mode scheme with chopped op-amps and internal clock generators to eliminate op-amp offset.A low dropout regulator(LDO)and a pre-regula-tor enhance output driving and LS,respectively.Curvature compensation enhances the TC by addressing higher-order nonlinear-ity.These approaches,effective near room temperature,employs trimming at both 20 and 60°C.When combined with fixed cur-vature correction currents,it achieves an ultra-low TC for each chip.Implemented in a CMOS 180 nm process,the BGR occu-pies 0.548 mm²and operates at 2.5 V with 84μA current draw from a 5 V supply.An average TC of 2.69 ppm/℃ with two-point trimming and 0.81 ppm/℃ with multi-point trimming are achieved over the temperature range of-40 to 125℃.It accommo-dates a load current of 1 mA and an LS of 42 ppm/V,making it suitable for precise BMS applications.
文摘Acceptor-donor-acceptor(A-D-A)type molecules,of which the novel non-fused azacyclic end-group pyrazoli-nones were modified with chlorine substitution on the phenyl ring,were synthesized.The non-fused azacyclic end-group py-razolinones have the advantages of simple synthesis steps,low cost and environmental friendliness,compared to the classical end-group dicyanomethyleneindianone.The properties of the synthesized A-D-A type molecules with non-fused azacyclic end groups were characterized by theoretical calculation,UV-vis absorption,cyclic voltammetry,X-ray diffraction and space charge limited current.It is shown that the strong UV-vis absorptions of the synthesized A-D-A type molecules are located in the wavelength range of 500~700 nm,with a moderate band gap of nearly 1.7 eV.At the same time,the influence of end-group chlorination on the properties of A-D-A type molecules was compared and explored.It is proven that this kind of A-D-A type molecule with non-fused azacyclic end groups has the potential to be applied as interfacial modified layer of the active layer in perovskite solar cell devices.
文摘This study introduces a comprehensive theoretical framework for accurately calculating the electronic band-structure of strained long-wavelength InAs/GaSb type-Ⅱsuperlattices.Utilizing an eight-band k·p Hamilto⁃nian in conjunction with a scattering matrix method,the model effectively incorporates quantum confinement,strain effects,and interface states.This robust and numerically stable approach achieves exceptional agreement with experimental data,offering a reliable tool for analyzing and engineering the band structure of complex multi⁃layer systems.
文摘The wide band gap characteristics of gallium oxide make it very suitable for the preparation of solar-blind ultra-violet photodetectors.The responsivity of ultraviolet photodetectors based on thin films is often low.However,nanomaterials have excellent photoelectric properties in device applications due to the high stability brought by high specific surface area and high crystal quality.Here,we successfully depositedβ-Ga_(2)O_(3) nanopores on the double-pass ordered porous AAO tem-plate by PLD.The porous AAO template is used as the growth space of nanomaterials,and the gallium oxide material is filled into the pores of the template to form a nanotube structure.By optimizing the preparation process,the relationship be-tween the performance of gallium oxide nanopores and the growth time was studied in depth.With the increase of growth time,the responsivity of the detector was improved.The rise timeτr=0.7 s,the decay timeτ_(d)=1.3 s,and the responsivity reached 4.63 mA·W^(-1),which was higher than 2.24 mA·W^(-1)of the responsivity of silicon-based gallium oxide nanorods.
基金Project supported by the National Natural Science Foundation of China(No.51875569)。
文摘Reducing the vibration transmission in beams is of significant interest,as beams are among the most widely used basic structures in numerous practical engineering applications.However,achieving broadband suppression of multi-polarization low-frequency vibration in beams presents a challenge.This study proposes a single-phase multi-resonant metabeam,which consists of a host beam with subwavelength arrays of tunable local resonators.These resonators exhibit adjustable multi-polarization resonant modes that strongly couple with the host beam,enabling simultaneous suppression of multi-type waves over a broad frequency range.The theoretical analysis demonstrates that under the fixed total added-mass ratio(γ_(total)=1.5),the tailored frequency spacing(δ=25-50 Hz)and the controlled loss factor(η=0.03–0.07)act synergistically to broaden bandgaps through resonant zone overlapping and attenuation peak smoothing.The experimental validation with monolithic three-dimensional(3D)-printed specimens confirms the efficacy of this design in multi-polarization vibration control within a deepsubwavelength bandgap,opening a new avenue for designing multi-polarization vibration suppression structures.
基金supported by the National Natural Science Foundation of China(Nos.12364015 and 52176072)the Five-Year Action Plan for Shccig-Qinling Program and Key Project of Hubei Province Key Research and Development Plan(No.2021BCA140)+4 种基金the Industry and Education Combination Innovation Platform of Intelligent Manufacturing and Graduate Joint Training Base at Guizhou University(No.2020-520000-83-01-324061)the National Key Research and Development Plan(No.2022YFF0706500)Guizhou University Natural Science Special(special post)Research Fund(No.(2023)17)Guizhou Engineering Research Center for Smart Services(No.2203-520102-04-04-298868)the Construction of Science and Technology Platform of Guiyang(No.[2023]7-3).
文摘Low energy-storage density and inferior thermal stability are a long-term obstacle to the advancement of pulse power devices.Herein,these concerns are addressed by improving bandgap and fabricating polar nanoregions,and the superior high efficiency of~86.7%,excellent thermal stability of~2%(31-160℃)and energy density of~6.8 J·cm^(-3)are achieved in Bi_(0.5)Na_(0.5)TiO_(3)-La_(0.1)Sr_(0.8)TiO_(3)-δ-NaNbO_(3)ceramics.The high breakdown strength(460 kV·cm^(-1))is ascribed to the broadened bandgap and refined grain.Slim ferroelectric loops originate from the construction of polar nanoregions(PNRs)in a pseudocubic matrix,and transmission electron microscope and piezoelectric force microscope measurements reveal the occurrence of PNRs.The phase-field stimulation and UV-Vis spectrophotometer measurement reveal that the increased grain boundary density and bandgap are beneficial for promoting breakdown strength.The strategy provides an efficient path to prepare Bi_(0.5)Na_(0.5)TiO_(3)La_(0.1)Sr_(0.8)TiO_(3)-δ-based ceramics with superior efficiency,high energy density and outstanding thermal stability.
基金Natural Science Foundation of China under Grant No.42277130Natural Science Foundation of Shandong Province under Grant No.ZR2021ME144。
文摘With the acceleration of urbanization,environmental vibration and noise pollution have become increasingly severe,and traditional vibration and noise reduction technologies are insufficient to meet current vibration control requirements.This study,based on locally resonant theory,designed a novel local resonance periodic block(LRPB).Using the plane wave expansion method(PWEM)and the finite element method(FEM),this study investigated the bandgap characteristics,formation mechanisms,and vibration and acoustic performance of an LRPB under different periodic structures and material selection.The vibration reduction and noise reduction performance of LRPB has been validated through the Qingdao metro project.The research results show that the LRPB is superior to other periodic structures in terms of wide bandgap.Furthermore,configuring soft scatterer material,increasing the unit size,enhancing the material filling rate,and adopting a honeycomb arrangement can effectively reduce bandgap frequency.In structural design,non-high symmetry demonstrates greater advantages.In a study of a subway tunnel,the LRPB demonstrated superior vibration and noise mitigation performance compared to wave impeding block(WIB),thereby demonstrating potential for use in the field of vibration and noise reduction with regard to structures.
基金financially supported by the Natural Science Foundation of China(52372226,52202300,62288102,62350013,52303325)National Key Research and Development Program of China(2023YFB3608900)+5 种基金the Postdoctoral Fellowship Program ofthe China postdoctoral Science Foundation(CPSF)(Grant GZC20233506)the China Postdoctoral Science Foundation(Grant2024M764252)the Natural Science Foundation of Chongqing China(2023NSCQ-MSX0097)Guangdong Basic and Applied Basic Research Foundation(2024A1515010918)Shenzhen Science and Technology Program(Grant JCYJ20240813150819026)the Fundamental Research Funds for the Central Universities。
文摘Lead-tin(Pb-Sn)perovskites with an ideal bandgap of 1.34-1.40 eV show great promise in perovskite solar cells(PSCs).Recently,to address the environmental pollution and Sn^(2+)oxidation problems of dimethyl sulfoxide,methylammonium acetate(MAAc)ionic liquid has been developed as an alternative to fabricate ideal bandgap MAPb_(0.7)Sn_(0.3)I_(3)(1.36 eV)film via hot-casting in air.However,the spontaneous crystallization of Pb-Sn perovskite initiated by heat-induced supersaturation is fast and random,setting critical challenges in regulating crystal growth during the film-forming process.Herein,a lattice activation strategy is developed to control the crystallization dynamics of MAPb_(0.7)Sn_(0.3)I_(3)in MAAc to produce films with micrometer-sized grains in air.FA is shown to activate the crystal lattice that facilitates the formation of intermediates and balances the crystal growth of MAPb_(0.7)Sn_(0.3)I_(3),producing films with a grain size of 2.78±0.17μm.Furthermore,4-fluoro-phenethylammonium and phenethylammonium are adopted to passivate the defects in the film and promote the energy level alignment at the top interface,respectively.The optimized PSC device achieved an efficiency of 18.24%with a short-circuit current of 29.84 mA/cm^(2),which are both the highest values in 1.36 eV Pb-Sn PSCs to date.Notably,the unencapsulated devices show excellent storage and air stability under various conditions.
基金partially supported by the financial supports from Aaivalayam-DIRAC,Indiathe Science and Technology Development Fund(Nos.007/2017/A1 and 132/2017/A3),Macao Special Administration Region(SAR),China+2 种基金National Natural Science Fund(Nos.61875138,61435010,and 6181101252)Science and Technology Innovation Commission of the Shenzhen(Nos.KQTD2015032416270,JCYJ20150625103619275,and JCYJ20170811093453105)research funding from the Ministry of Science and Higher Education of the Russian Federation(Ural Federal University project within the Priority 2030 Program)。
文摘Hydrogenated two-dimensional(2D)materials have gained significant attention due to their tunable properties,which can be engineered through various functionalization techniques.This review discusses hydrogenated Xenes,a new class of fully hydrogenated mono-elemental 2D materials,including graphane,germanane,silicane,and stanane.Hydrogenation enhances the properties of Xenes,making them transparent,mechanically strong,electrically conductive,and rare.These materials off er a unique combination of characteristics that make them highly desirable for a variety of advanced applications in energy storage,organic electronics,and optoelectronics.Xenes such as silicane and germanane are semiconductors with tunable bandgaps,making them ideal for use in transistors,logic circuits,and sensors.Their electronic and optical properties can be finely adjusted,allowing them to be used in high-performance devices like LEDs,solar cells,and photodetectors.Furthermore,hydrogenated Xenes show potential in applications like batteries,supercapacitors,hydrogen storage,piezoelectricity,and biosensing,owing to their high surface area and versatility.This review also explores the impact of various hydrogenation techniques,including plasma treatment,wet chemical methods,and electrochemical hydrogenation,on the electronic,mechanical,thermal,optical,and magnetic properties of these materials.Advanced characterization techniques,such as X-ray absorption spectroscopy(XANES),have provided valuable insights into the electronic structure and bonding environments of these materials.Finally,the paper highlights the challenges and limitations of hydrogenation,including structural instability and environmental concerns,while discussing the future prospects and advancements needed to harness the full potential of hydrogenated 2D materials.This review serves as a comprehensive resource for researchers aiming to explore the applications of hydrogenated Xenes in next-generation technologies.
