In order to realize the tunable performance of a frequency selective surface （FSS）, a new unit cell is designed in this paper by properly adding two metal shorts to the ring slot. Based on the spectral-domain method...In order to realize the tunable performance of a frequency selective surface （FSS）, a new unit cell is designed in this paper by properly adding two metal shorts to the ring slot. Based on the spectral-domain method, the frequency responses of the FSS structure with two shorts per slot ring are analysed for both the horizontal and the vertical polarizations at the normal incidence. It is demonstrated that the presence of the metal shorts does not affect the resonant frequency of the horizontally polarized wave but doubles the resonant frequency of the vertically polarized wave. Therefore based on the analysis of the novel transmission properties, a new approach to adjusting the resonant frequency by rotating the FSS screen 90° is presented in this paper.展开更多
Non-enzyme glucose sensors constructed using transition metal oxides present several advantages such as their low cost,high stability,and high sensitivity.Herein,a kind of porous nanosphere-stacking CuO structure has ...Non-enzyme glucose sensors constructed using transition metal oxides present several advantages such as their low cost,high stability,and high sensitivity.Herein,a kind of porous nanosphere-stacking CuO structure has been synthesized by optimizing the thermal decomposition atmosphere,which was derived from Cu-metal-organic framework(Cu-MOF)microrods.Such hierarchical CuO structures,with controllable porosity and adjustable surface area,are efficient catalytic materials for glucose sensing.Benefiting from structural advantages,the obtained porous hierarchical CuO nanospheres exhibit enhanced sensing performance compared to hierarchical CuO clusters.Based on CuO,the effects of surface and morphology on the sensing performance of glucose are also discussed.The sensitivity of CuO porous hierarchically nanospheres for glucose is found to be 1806.1μA cm^(-2)mM^(−1)in the wide linear range of 0-6.535 mM with a low detection limit(S/N=3)of 0.15μM.Glucose detection in artificial saliva is then performed,which shows excellent capability in the low concentration range(5μM-1.165 mM)for noninvasive sensing performance.The sensor also demonstrates a good recovery in real saliva.The novel MOF-templated CuO hierarchical nanospheres are expected to be effective sensing materials for developing non-enzyme and non-invasive glucose sensors.展开更多
In this paper, we have shown that perfect absorption at terahertz frequencies can be achieved by using a composite structure where graphene is coated on one-dimensional photonic crystal(1 DPC) separated by a dielectri...In this paper, we have shown that perfect absorption at terahertz frequencies can be achieved by using a composite structure where graphene is coated on one-dimensional photonic crystal(1 DPC) separated by a dielectric. Due to the excitation of optical Tamm states(OTSs) at the interface between the graphene and 1 DPC, a strong absorption phenomenon occurs induced by the coupling of the incident light and OTSs. Although the perfect absorption produced by a metal–distributed Bragg reflector structure has been researched extensively, it is generally at a fixed frequency and not tunable. Here, we show that the perfect absorption at terahertz frequency not only can be tuned to different frequencies but also exhibits a high absorption over a wide angle range. In addition,the absorption of the proposed structure is insensitive to the polarization, and multichannel absorption can berealized by controlling the thickness of the top layer.展开更多
Graphene-based surface plasmon waveguides(SPWs) show high confinement well beyond the diffraction limit at terahertz frequencies. By combining a graphene SPW and nonlinear material, we propose a novel graphene/AlGaAs ...Graphene-based surface plasmon waveguides(SPWs) show high confinement well beyond the diffraction limit at terahertz frequencies. By combining a graphene SPW and nonlinear material, we propose a novel graphene/AlGaAs SPW structure for terahertz wave difference frequency generation(DFG) under near-infrared pumps.The composite waveguide, which supports single-mode operation at terahertz frequencies and guides two pumps by a high-index-contrast AlGaAs∕Al Oxstructure, can confine terahertz waves tightly and realize good mode field overlap of three waves. The phase-matching condition is satisfied via artificial birefringence in an AlGaAs∕Al Ox waveguide together with the tunability of graphene, and the phase-matching terahertz wave frequency varies from 4 to 7 THz when the Fermi energy level of graphene changes from 0.848 to 2.456 eV. Based on the coupled-mode theory, we investigate the power-normalized conversion efficiency for the tunable terahertz wave DFG process by using the finite difference method under continuous wave pumps, where the tunable bandwidth can reach 2 THz with considerable conversion efficiency. To exploit the high peak powers of pulses, we also discuss optical pulse evolutions for pulse-pumped terahertz wave DFG processes.展开更多
The optical conductivity of single layer graphene (SLG) can be significantly and reversibly modified when the Fermi level is tuned by electrical gating. However, so far this interesting property has rarely been applie...The optical conductivity of single layer graphene (SLG) can be significantly and reversibly modified when the Fermi level is tuned by electrical gating. However, so far this interesting property has rarely been applied to free-space two-dimensional (2D) photonic devices because the surface-incident absolute absorption of SLG is limited to 1%–2%. No significant change in either reflectance or transmittance would be observed even if SLG is made transparent upon gating. To achieve significantly enhanced surface-incident optical absorption in SLG in a device structure that also allows gating, here we embed SLG in an optical slot-antenna-coupled cavity (SAC) framework, simultaneously enhancing SLG absorption by up to 20 times and potentially enabling electrical gating of SLG as a step towards tunable 2D photonic surfaces. This framework synergistically integrates near-field enhancement induced by ultrahigh refractive index semimetal slot-antenna with broadband resonances in visible and infrared regimes, ~ 3 times more effective than a vertical cavity structure alone. An example of this framework consists of self-assembled, close-packed Sn nanodots separated by ~ 10 nm nanogaps on a SLG/SiO2/Al stack, which dramatically increases SLG optical absorption to 10%-25% at λ = 600–1,900 nm. The enhanced SLG absorption spectrum can also be controlled by the insulator thickness. For example, SLG embedded in this framework with a 150 nm-thick SiO2 insulating layer displays a distinctive red color in contrast to its surrounding regions without SLG on the same sample under white light illumination. This opens a potential path towards gate-tunable spectral reflectors. Overall, this work initiates a new approach towards tunable 2D photonic surfaces.展开更多
A highly stretchable plasmonic structure composed of a monolayer array of metal-capped colloidal spheres on an elastomeric substrate has been fabricated using simple and inexpensive self-assembly and transfer-printing...A highly stretchable plasmonic structure composed of a monolayer array of metal-capped colloidal spheres on an elastomeric substrate has been fabricated using simple and inexpensive self-assembly and transfer-printing techniques.This composite structure supports coupled surface plasmons whose wavelengths are sensitive to the arrangement of the metal-capped colloidal spheres.Upon stretching,the lattice of metal-capped colloidal spheres will be deformed,leading to a large wavelength shift of surface plasmon resonances and simultaneously an obvious color change.This stretchable plasmonic structure offers a promising approach to tune surface plasmon resonances and might be exploited in realizing flexible plasmonic devices with tunability of mechanical strain.展开更多
The wettability of catalyst plays an important role in regulating catalytic performance in heterogenous catalysis because the microenvironment around the catalytic sites directly determines the mass transfer process o...The wettability of catalyst plays an important role in regulating catalytic performance in heterogenous catalysis because the microenvironment around the catalytic sites directly determines the mass transfer process of reactants.Inspired by gas trapped on the surface of subaquatic spiders,amphiphilic micro-organohydrogels with tunable surface wettabilities were developed by anchoring various alkane chains onto a poly(2-(dimethylamino)ethyl methacrylate)(p(DMAEMA))hydrophilic microgel network.Palladium nanoparticles(Pd NPs)were encapsulated in amphiphilic microgels(amphiphilic Pd@M)to catalyze hydrogenation reaction,achieving higher activities than pristine monohydrophilic Pd@M composite.The underwater oleophilicity and aerophilicity of Pd@M composites were quantified by oil/gas adhesion measurements and computational simulations.The higher amphiphilic catalytic activities are attributed to the formation of a gas-oil-solid reaction interface on the catalyst surfaces,allowing rapid transport of H2 and organic substrates through water to the Pd catalytic sites.Additionally,amphiphilic Pd@M composites also exhibit more superior catalytic performance in multi-substrates reaction.展开更多
MXene-based films have been intensively explored for construction of piezoresistive flexible pressure sensors owing to their excellent mechanical and electrical properties.High pressure sensitivity relies on pre-moldi...MXene-based films have been intensively explored for construction of piezoresistive flexible pressure sensors owing to their excellent mechanical and electrical properties.High pressure sensitivity relies on pre-molding a flexible substrate,or regulating the micromorphology of MXene sheets,to obtain a micro-structured surface.However,the two avenues usually require complicated and time-consuming microfabrication or wet chemical processing,and are limited to non-adjustable topographicelectrical(topo-electro)properties.Herein,we propose a lithographic printing inspired in-situ transfer(LIPIT)strategy to fabricate MXene-ink films(MIFs).In LIPIT,MIFs not only inherit ridge-and-valley microstructure from paper substrate,but also achieve localized topo-electro tunability by programming ink-writing patterns and cycles.The MIF-based flexible pressure sensor with periodical topo-electro gradient exhibits remarkably boosted sensitivity in a wide sensing range(low detection limit of 0.29 Pa and working range of 100 kPa).The MIF sensor demonstrates versatile applicability in both subtle and vigorous pressuresensing fields,ranging from pulse wave extraction and machine learning-assisted surface texture recognition to piano-training glove(PT-glove)for piano learning.The LIPIT is quick,low-cost,and compatible with free ink/substrate combinations,which promises a versatile toolbox for designing functional MXene films with tailored morphological-mechanical-electrical properties for extended application scenarios.展开更多
基金Project supported by the National Natural Science Foundation of China (Grant No. 61172012)
文摘In order to realize the tunable performance of a frequency selective surface （FSS）, a new unit cell is designed in this paper by properly adding two metal shorts to the ring slot. Based on the spectral-domain method, the frequency responses of the FSS structure with two shorts per slot ring are analysed for both the horizontal and the vertical polarizations at the normal incidence. It is demonstrated that the presence of the metal shorts does not affect the resonant frequency of the horizontally polarized wave but doubles the resonant frequency of the vertically polarized wave. Therefore based on the analysis of the novel transmission properties, a new approach to adjusting the resonant frequency by rotating the FSS screen 90° is presented in this paper.
基金supported by the National Key R&D Program of China[2018YFB1501203,2018YFB1501205]National Natural Science Foundation of China[51971068,51871065,51671062,51863005,51462006,51801041 and U1501242]+1 种基金Guangxi Natural Science Foundation[2017AD23029,2017JJB150085,2014GXNSFAA118319,and 2014GXNAFDA118005]Guangxi Bagui Scholar Foundation,Guangxi Talent Xiaogaodi Project and the study abroad program for the graduate student of Guilin University of Electronic Technology[YXYJ2900].
文摘Non-enzyme glucose sensors constructed using transition metal oxides present several advantages such as their low cost,high stability,and high sensitivity.Herein,a kind of porous nanosphere-stacking CuO structure has been synthesized by optimizing the thermal decomposition atmosphere,which was derived from Cu-metal-organic framework(Cu-MOF)microrods.Such hierarchical CuO structures,with controllable porosity and adjustable surface area,are efficient catalytic materials for glucose sensing.Benefiting from structural advantages,the obtained porous hierarchical CuO nanospheres exhibit enhanced sensing performance compared to hierarchical CuO clusters.Based on CuO,the effects of surface and morphology on the sensing performance of glucose are also discussed.The sensitivity of CuO porous hierarchically nanospheres for glucose is found to be 1806.1μA cm^(-2)mM^(−1)in the wide linear range of 0-6.535 mM with a low detection limit(S/N=3)of 0.15μM.Glucose detection in artificial saliva is then performed,which shows excellent capability in the low concentration range(5μM-1.165 mM)for noninvasive sensing performance.The sensor also demonstrates a good recovery in real saliva.The novel MOF-templated CuO hierarchical nanospheres are expected to be effective sensing materials for developing non-enzyme and non-invasive glucose sensors.
基金National Natural Science Foundation of China(NSFC)(51806001,61490713,61505111)Natural Science Foundation of Guangdong Province(2015A030313549)+3 种基金China Postdoctoral Science Foundation(2016M602509)Science and Technology Planning Project of Guangdong Province(2016B050501005)Science and Technology Project of Shenzhen(JCYJ20150324141711667)Natural Science Foundation of SZU(827-000051,827-000052,827-000059)
文摘In this paper, we have shown that perfect absorption at terahertz frequencies can be achieved by using a composite structure where graphene is coated on one-dimensional photonic crystal(1 DPC) separated by a dielectric. Due to the excitation of optical Tamm states(OTSs) at the interface between the graphene and 1 DPC, a strong absorption phenomenon occurs induced by the coupling of the incident light and OTSs. Although the perfect absorption produced by a metal–distributed Bragg reflector structure has been researched extensively, it is generally at a fixed frequency and not tunable. Here, we show that the perfect absorption at terahertz frequency not only can be tuned to different frequencies but also exhibits a high absorption over a wide angle range. In addition,the absorption of the proposed structure is insensitive to the polarization, and multichannel absorption can berealized by controlling the thickness of the top layer.
基金National Natural Science Foundation of China(NSFC)(11547187,11405073,61405073)Shandong Provincial Key R&D Program(2017CXGC0416)
文摘Graphene-based surface plasmon waveguides(SPWs) show high confinement well beyond the diffraction limit at terahertz frequencies. By combining a graphene SPW and nonlinear material, we propose a novel graphene/AlGaAs SPW structure for terahertz wave difference frequency generation(DFG) under near-infrared pumps.The composite waveguide, which supports single-mode operation at terahertz frequencies and guides two pumps by a high-index-contrast AlGaAs∕Al Oxstructure, can confine terahertz waves tightly and realize good mode field overlap of three waves. The phase-matching condition is satisfied via artificial birefringence in an AlGaAs∕Al Ox waveguide together with the tunability of graphene, and the phase-matching terahertz wave frequency varies from 4 to 7 THz when the Fermi energy level of graphene changes from 0.848 to 2.456 eV. Based on the coupled-mode theory, we investigate the power-normalized conversion efficiency for the tunable terahertz wave DFG process by using the finite difference method under continuous wave pumps, where the tunable bandwidth can reach 2 THz with considerable conversion efficiency. To exploit the high peak powers of pulses, we also discuss optical pulse evolutions for pulse-pumped terahertz wave DFG processes.
基金This work has been sponsored by National Science Foundation under the collaborative research awards#1509272 and#1509197We thank Dr.Christopher Levey from Thayer school of Engineering at Dartmouth College for helpful discussionsWe greatly appreciate the advanced characterization instruments of the Electron Microscope Facility at Dartmouth College and the materials processing instruments of the Micro-System Technology Lab at MIT.
文摘The optical conductivity of single layer graphene (SLG) can be significantly and reversibly modified when the Fermi level is tuned by electrical gating. However, so far this interesting property has rarely been applied to free-space two-dimensional (2D) photonic devices because the surface-incident absolute absorption of SLG is limited to 1%–2%. No significant change in either reflectance or transmittance would be observed even if SLG is made transparent upon gating. To achieve significantly enhanced surface-incident optical absorption in SLG in a device structure that also allows gating, here we embed SLG in an optical slot-antenna-coupled cavity (SAC) framework, simultaneously enhancing SLG absorption by up to 20 times and potentially enabling electrical gating of SLG as a step towards tunable 2D photonic surfaces. This framework synergistically integrates near-field enhancement induced by ultrahigh refractive index semimetal slot-antenna with broadband resonances in visible and infrared regimes, ~ 3 times more effective than a vertical cavity structure alone. An example of this framework consists of self-assembled, close-packed Sn nanodots separated by ~ 10 nm nanogaps on a SLG/SiO2/Al stack, which dramatically increases SLG optical absorption to 10%-25% at λ = 600–1,900 nm. The enhanced SLG absorption spectrum can also be controlled by the insulator thickness. For example, SLG embedded in this framework with a 150 nm-thick SiO2 insulating layer displays a distinctive red color in contrast to its surrounding regions without SLG on the same sample under white light illumination. This opens a potential path towards gate-tunable spectral reflectors. Overall, this work initiates a new approach towards tunable 2D photonic surfaces.
基金This work was supported by the National Program on Key Basic Research Project(973 Program)(Grant Nos.2007CB613200 and 2006CB921700)The research of J.Z.and X.H.L.is further supported by the National Natural Science Foundation of China(NSFC)and the Shanghai Science and Technology Commission.
文摘A highly stretchable plasmonic structure composed of a monolayer array of metal-capped colloidal spheres on an elastomeric substrate has been fabricated using simple and inexpensive self-assembly and transfer-printing techniques.This composite structure supports coupled surface plasmons whose wavelengths are sensitive to the arrangement of the metal-capped colloidal spheres.Upon stretching,the lattice of metal-capped colloidal spheres will be deformed,leading to a large wavelength shift of surface plasmon resonances and simultaneously an obvious color change.This stretchable plasmonic structure offers a promising approach to tune surface plasmon resonances and might be exploited in realizing flexible plasmonic devices with tunability of mechanical strain.
基金We acknowledge the National Natural Science Funds for Distinguished Young Scholar(No.21725401)the National Key Technologies R&D Program of China(No.2017YFA0207800)+2 种基金the China Scholarship Council(CSC,No.201606025097),the 111 project(No.B14009)the Chinese Postdoctoral Science Foundation(Nos.2017M620012 and 2019M650434)the Fundamental Research Funds for the Central Universities.
文摘The wettability of catalyst plays an important role in regulating catalytic performance in heterogenous catalysis because the microenvironment around the catalytic sites directly determines the mass transfer process of reactants.Inspired by gas trapped on the surface of subaquatic spiders,amphiphilic micro-organohydrogels with tunable surface wettabilities were developed by anchoring various alkane chains onto a poly(2-(dimethylamino)ethyl methacrylate)(p(DMAEMA))hydrophilic microgel network.Palladium nanoparticles(Pd NPs)were encapsulated in amphiphilic microgels(amphiphilic Pd@M)to catalyze hydrogenation reaction,achieving higher activities than pristine monohydrophilic Pd@M composite.The underwater oleophilicity and aerophilicity of Pd@M composites were quantified by oil/gas adhesion measurements and computational simulations.The higher amphiphilic catalytic activities are attributed to the formation of a gas-oil-solid reaction interface on the catalyst surfaces,allowing rapid transport of H2 and organic substrates through water to the Pd catalytic sites.Additionally,amphiphilic Pd@M composites also exhibit more superior catalytic performance in multi-substrates reaction.
基金supported by the National Natural Science Foundation of China(Nos.62122080,62261136551,and 52203365)the Natural Science Foundation of Shanghai(Nos.22ZR1481700 and 22dz1205000)the Shanghai Pujiang Program(No.21PJ1414800).
文摘MXene-based films have been intensively explored for construction of piezoresistive flexible pressure sensors owing to their excellent mechanical and electrical properties.High pressure sensitivity relies on pre-molding a flexible substrate,or regulating the micromorphology of MXene sheets,to obtain a micro-structured surface.However,the two avenues usually require complicated and time-consuming microfabrication or wet chemical processing,and are limited to non-adjustable topographicelectrical(topo-electro)properties.Herein,we propose a lithographic printing inspired in-situ transfer(LIPIT)strategy to fabricate MXene-ink films(MIFs).In LIPIT,MIFs not only inherit ridge-and-valley microstructure from paper substrate,but also achieve localized topo-electro tunability by programming ink-writing patterns and cycles.The MIF-based flexible pressure sensor with periodical topo-electro gradient exhibits remarkably boosted sensitivity in a wide sensing range(low detection limit of 0.29 Pa and working range of 100 kPa).The MIF sensor demonstrates versatile applicability in both subtle and vigorous pressuresensing fields,ranging from pulse wave extraction and machine learning-assisted surface texture recognition to piano-training glove(PT-glove)for piano learning.The LIPIT is quick,low-cost,and compatible with free ink/substrate combinations,which promises a versatile toolbox for designing functional MXene films with tailored morphological-mechanical-electrical properties for extended application scenarios.
