In this paper,we use microwave reduction strategy to synthesize a new bi-functional sulfur host material at the service of cathode substrate for lithium-sulfur batteries(LSBs),the composite is made of hierarchical por...In this paper,we use microwave reduction strategy to synthesize a new bi-functional sulfur host material at the service of cathode substrate for lithium-sulfur batteries(LSBs),the composite is made of hierarchical porous carbon foam supported carbon-encapsulated chromium carbide nano-particles(Cr_(3)C_(2)@C/HPCF),in which the well-distributed conductive Cr_(3)C_(2) nano-particles can act as powerful chemical adsorbent and are effective in restraining the shuttle effect of lithium polysulfides(LiPSs).Test results show that the Cr_(3)C_(2)@C/HPCF based sulfur electrodes with 75 wt.%of sulfur exhibit a high initial discharging capacity of 1,321.1 mAh·g^(−1) at 0.1 C(3.5 mg·cm^(−2)),and a reversible capacity can still maintain stability at 1,002.1 mAh·g^(−1) after 150 cycles.Even increasing the areal sulfur loading to 4 mg·cm^(−2),the electrodes can still deliver an initial discharging capacity of 948.0 mAh·g^(−1) at 0.5 C with ultra-slow capacity decay rate of 0.075%per cycle during 500 cycles.Furthermore,the adsorption energy between the Cr_(3)C_(2) surface and LiPSs as well as theoretic analysis based on first-principles is also investigated.展开更多
In this paper, Fe30Pt70/Fe3O4 core/shell nanoparticles were synthesized by chemical routine and the layered polyethylenimine (PEI)-Fe30Pt70/Fe3O4 structure was constructed by molecule-mediated self-assembly techniqu...In this paper, Fe30Pt70/Fe3O4 core/shell nanoparticles were synthesized by chemical routine and the layered polyethylenimine (PEI)-Fe30Pt70/Fe3O4 structure was constructed by molecule-mediated self-assembly technique. The dimension of core/shell structured nanoparticles was that of 4nm core and 2 nm shell. After annealing under a flow of forming gas (50%Ar2+30%H2) for 1 h at or above 400℃, the iron oxide shell was reduced to Fe and diffused to Pt-rieh core, which leaded to the formation of L1. phase FePt at low temperature. The x-ray diffraction results and magnetic properties measurement showed that the chemical ordering temperature of Fe30Pt70/Fe3O4 core/shell nanoparticles assembly can be reduced to as low as 400℃. The sample annealed at 400℃ showed the eoereivity of 4KOe with the applied field of 1.5T. The core/shell structure was suggested to be an effective way to reduce the ordering temperature obviously.展开更多
LaF_3:Yb^(3 +),Er^(3 +) nanoparticles were successfully synthesized using solvothermal treatment,and LaF_3:Yb^(3 +),Er^(3 +) /SiO_2 core /shell nanoparticles were also prepared with reverse microemulsion technique.The...LaF_3:Yb^(3 +),Er^(3 +) nanoparticles were successfully synthesized using solvothermal treatment,and LaF_3:Yb^(3 +),Er^(3 +) /SiO_2 core /shell nanoparticles were also prepared with reverse microemulsion technique.The crystal structure,morphology and photoluminescence properties of as-prepared core /shell nanoparticles were investigated by X-ray diffraction,transmission electron microscopy and fluorescence spectrophotometer.The results showed that LaF_3:Yb^(3 +),Er^(3 +) nanoparticles are of hexagonal structure and SiO_2 shell is amorphous.The size of LaF_3:Yb^(3 +),Er^(3 +) nanoparticles is 13 nm and the LaF_3:Yb^(3 +),Er^(3 +) /SiO_2 nanoparticles present clearly a core /shell structure with 12 nm shell thickness.The solubility of LaF_3:Yb^(3 +),Er^(3 +) nanocrystals in water and the biocompatibility are both improved by the SiO_2 shell.The upconversion luminescence spectra suggested that the SiO_2 shell has small effect on the upconversion luminescence properties of the LaF_3:Yb^(3 +),Er^(3 +) nanocrystals.The core /shell structure LaF_3:Yb^(3 +),Er^(3 +) /SiO_2 nanoparticles are expected to be used in biological applications.展开更多
Rational construction of highly efficient and cheap bifunctional electrocatalysts to boost both oxygen evolution reaction(OER)and oxygen reduction reaction(ORR)is extremely essential for the wide application of rechar...Rational construction of highly efficient and cheap bifunctional electrocatalysts to boost both oxygen evolution reaction(OER)and oxygen reduction reaction(ORR)is extremely essential for the wide application of rechargeable metal-air battery.In this work,we design a core-shell structural catalyst of CoNi dual-metal embedded in nitrogen doped porous carbon(NPC,CoNi@NPC),which is developed via the pyrolysis of CoNiMOFs,assisting by mesoporous SiO_(2) to effectively inhibit the aggregation of metal sites.Consequently,the asprepared CoNi@NPC manifests good ORR activity with half-wave potential up to 0.77 V.Specifically,the CoNi@NPC gives a very low OER over-potential of merely 101 mV in 6 M KOH along with high stability,outperforming the commercial Pt/C-RuO_(2).Moreover,the home-made zinc air battery with CoNi@NPC air cathode demonstrates excellent stability over long-term charging–discharging test,and delivers the maximum power density of 224 mW cm^(-2).The enhanced high performance of CoNi@NPC bifunctional catalyst for both ORR and OER can be ascribed to its unique core-shell structure and strong synergistic effect between the dual-bimetal active sites and the heteroatom doped carbon.This work opens a new avenue for the rational design of nonprecious metal bifunctional catalysts for rechargeable metal-air battery.展开更多
Rupturing the alumina shell(shell-breaking)is a prerequisite for releasing energy from aluminum powder.Thermal stress overload in a high-temperature environment is an important factor in the rupture of the alumina she...Rupturing the alumina shell(shell-breaking)is a prerequisite for releasing energy from aluminum powder.Thermal stress overload in a high-temperature environment is an important factor in the rupture of the alumina shell.COMSOL Multiphysics was used to simulate and analyze the shell-breaking response of micron-scale aluminum particles with different particle sizes at 650℃in vacuum.The simulation results show that the thermal stability time and shell-breaking response time of 10μm–100μm aluminum particles are 0.15μs–11.44μs and 0.08μs–3.94μs,respectively.They also reveal the direct causes of shell breaking for aluminum particles with different particle sizes.When the particle size is less than 80μm,the shell-breaking response is a direct result of compressive stress overload.When the particle size is between80μm and 100μm,the shell-breaking response is a direct result of tensile stress overload.This article provides useful guidance for research into the energy release of aluminum powder.展开更多
The bind-free carbon cloth-supported electrodes hold the promises for high-performance electrochemical capacitors with high specific capacitance and good cyclic stability.Considering the close connection between their...The bind-free carbon cloth-supported electrodes hold the promises for high-performance electrochemical capacitors with high specific capacitance and good cyclic stability.Considering the close connection between their performance and the amount of carbon material loaded on the electrodes,in this work,NiCo_(2)O_(4) nanowires were firstly grown on the substrate of active carbon cloth to provide the necessary surface area in the longitudinal direction.Then,the quinone-rich nitrogen-doped carbon shell structure was formed around NiCo_(2)O_(4) nanowires,and the obtained composite was used as electrode for electric double layer capacitor.The results showed that the composite electrode displayed an area-specific capacitance of 1794 mF·cm^(-2) at the current density of 1 mA·cm^(-2).The assembled symmetric electric double layer capacitor achieved a high energy density of 6.55 mW·h·cm^(-3) at a power density of 180 mW·cm^(-3).The assembled symmetric capacitor exhibited a capacitance retention of 88.96%after 10000 charge/discharge cycles at the current density of 20 mA·cm^(-2).These results indicated the potentials in the preparation of the carbon electrode materials with high energy density and good cycling stability.展开更多
Advanced biomaterial-based strategies for treatment of peripheral nerve injury require precise control over both topological and biological cues for facilitating rapid and directed nerve regeneration.As a highly bioac...Advanced biomaterial-based strategies for treatment of peripheral nerve injury require precise control over both topological and biological cues for facilitating rapid and directed nerve regeneration.As a highly bioactive and tissue-specifc natural material,decellularized extracellular matrix(dECM)derived from peripheral nerves(decellularized nerve matrix,DNM)has drawn increasing attention in the feld of regenerative medicine,due to its outstanding capabilities in facilitating neurite outgrowth and remyelination.To induce and maintain sufcient topological guidance,electrospinning was conducted for fabrication of axially aligned nanofbers consisting of DNM and poly(ε-caprolactone)(PCL).Core–shell structured fbers were prepared by coaxial electrospinning using DNM as the shell and PCL as the core.Compared to the aligned electrospun fbers using preblended DNM/PCL,the core–shell structured fbers exhibited lower tensile strength,faster degradation,but considerable toughness for nerve guidance conduit preparation and relatively intact fbrous structure after long-term degradation.More importantly,the full DNM surface coverage of the aligned core–shell fbers efectively promoted axonal extension and Schwann cells migration.The DNM contents further triggered neurite bundling and myelin formation toward nerve fber maturation and functionalization.Herein,we not only pursue a multi-functional scafold design for nerve regeneration,a detailed comparison between core–shell structured and preblended electrospinning of DNM/PCL composites was also provided as an applicable paradigm for advanced tissue-engineered strategies using dECM-based biomaterials.展开更多
Crystalline Fe/MnO@C core–shell nanocapsules inlaid in porous amorphous carbon matrix(FMCA)was synthesized successfully with a novel confinement strategy.The heterogeneous Fe/MnO nanocrystals are with approximate sin...Crystalline Fe/MnO@C core–shell nanocapsules inlaid in porous amorphous carbon matrix(FMCA)was synthesized successfully with a novel confinement strategy.The heterogeneous Fe/MnO nanocrystals are with approximate single-domain size which gives rise to natural resonance in 2–18 GHz.The addition of MnO2 confines degree of graphitization catalyzed by iron and contributes to the formation of amorphous carbon.The heterogeneous materials composed of crystalline–amorphous structures disperse evenly and its density is significantly reduced on account of porous properties.Meanwhile,adjustable dielectric loss is achieved by interrupting Fe core aggregation and stacking graphene conductive network.The dielectric loss synergistically with magnetic loss endows the FMCA enhanced absorption.The optimal reflection loss(RL)is up to−45 dB,and the effective bandwidth(RL<−10 dB)is 5.0 GHz with 2.0 mm thickness.The proposed confinement strategy not only lays the foundation for designing high-performance microwave absorber,but also offers a general duty synthesis method for heterogeneous crystalline–amorphous composites with tunable composition in other fields.展开更多
Electrode material based on a novel core–shell structure consisting of NiCoS(NCS) solid fiber core and Mn S(MS) sheet shell(NCS@MS) in situ grown on carbon cloth(CC) has been successfully prepared by a simple...Electrode material based on a novel core–shell structure consisting of NiCoS(NCS) solid fiber core and Mn S(MS) sheet shell(NCS@MS) in situ grown on carbon cloth(CC) has been successfully prepared by a simple sulfurization-assisted hydrothermal method for high performance supercapacitor. The synthesized NiCoS@Mn S/CC electrode shows high capacitance of 1908.3 F gat a current density of 0.5 A gwhich is higher than those of NiCoSand Mn S at the same current density. A flexible all-solid-state asymmetric supercapacitor(ASC) is constructed by using NiCoS@Mn S/CC as positive electrode, active carbon/CC as negative electrode and KOH/poly(vinyl alcohol)(PVA) as electrolyte. The optimized ASC shows a maximum energy density of 23.3 Wh kgat 1 A g, a maximum power density of about7.5 kw kgat 10 A gand remarkable cycling stability. After 9000 cycles, the ASC still exhibited67.8% retention rate and largely unchanged charge/discharge curves. The excellent electrochemical properties are resulted from the novel core–shell structure of the NiCoS@Mn S/CC electrode, which possesses both high surface area for Faraday redox reaction and superior kinetics of charge transport. The NiCoS@Mn S/CC electrode shows a promising potential for energy storage applications in the future.展开更多
Two sets of(Mg,Y)-doped BaTiO_(3)samples were prepared to investigate the effects of the core/shell volumetric ratio on the dielectric-temperature behavior of BaTiO3:one set with samples of the same grain size but dif...Two sets of(Mg,Y)-doped BaTiO_(3)samples were prepared to investigate the effects of the core/shell volumetric ratio on the dielectric-temperature behavior of BaTiO3:one set with samples of the same grain size but different core sizes and the other with samples of the same core size but different shell thicknesses.The microstructural variation of the samples was characterized and their dielectric properties were measured.For both sets of samples,the temperature stability of the dielectric properties was generally improved with a reduction of the volumetric shell ratio regardless of the grain and core sizes.There existed,however,a limit of the reduction;for the studied range,shell thickness of one third of the core radius appeared to be an optimum thickness for the given amounts of dopants.It was concluded that the volumetric shell ratio should be optimized so as not to exceed a specific limit,for our case two thirds of the grain volume,to secure temperature stability of the dielectric properties of BaTiO_(3).展开更多
Elemental state matter-heteroatom-doped carbon composites are of great importance for the development of anode in lithium ion batteries(LIBs).In this article,metal–organic frameworks(MOFs)are adopted as precursor to ...Elemental state matter-heteroatom-doped carbon composites are of great importance for the development of anode in lithium ion batteries(LIBs).In this article,metal–organic frameworks(MOFs)are adopted as precursor to prepare Co composites via metallurgical pyrolysis under controllable conditions.The obtained nitrogen-doped porous carbon-Co nanocomposite possesses core–shell structure(Co@C–N).Co@C–N exhibits the best Li storage performances as anode active matter.After the 200th cycles at current density of 0.2 A g^(-1),a reversible capacity of 870 mAh g^(-1)is retained.A reversible capacity of 275 mAh g^(-1)still maintains with 5 A g^(-1).Co@C–N presents a high reversible capacity with excellent cycle stability.Considering the corresponding experimental and theoretical results,the Co0-based N-doped porous carbon composite is proposed to work as LIBs anode matter.These results provide a new design idea for electrode matters of metallic ion battery,and demonstrate that MOFs pyrolysis is an effective method for the construction of elemental state anode materials.展开更多
Sub-micron sized phenolic epoxy resin waterborne particles were prepared by phase inversion emulsification. Micro-phase separation occurred during the curing process at high temperature. The as-prepared samples posses...Sub-micron sized phenolic epoxy resin waterborne particles were prepared by phase inversion emulsification. Micro-phase separation occurred during the curing process at high temperature. The as-prepared samples possessed one glass transition temperature (Tg) and two exothermal processes during DSC heating scannings. After being thermally treated above the exothermal peak temperature, they possessed two glass transition temperatures with the disappearance of exothermal peaks, whilst a core/shell structure was formed. This was likely related with the outward diffusion of reactive oligomers to the outer layer of particles.展开更多
Conversion-type anode materials with a high charge storage capability generally su er from large volume expansion, poor electron conductivity, and sluggish metal ion transport kinetics. The electrode material describe...Conversion-type anode materials with a high charge storage capability generally su er from large volume expansion, poor electron conductivity, and sluggish metal ion transport kinetics. The electrode material described in this paper, namely cobalt sulphide nanoparticles encapsulated in carbon cages(Co9S8@NC), can circumvent these problems. This electrode material exhibited a reversible sodium-ion storage capacity of 705 mAh g^-1 at 100 mA g^-1 with an extraordinary rate capability and good cycling stability. Mechanistic study using the in situ transmission electron microscope technique revealed that the volumetric expansion of the Co9S8 nanoparticles is bu ered by the carbon cages, enabling a stable electrode–electrolyte interface. In addition, the carbon shell with high-content doped nitrogen significantly enhances the electron conductivity of the Co9S8@NC electrode material and provides doping-induced active sites to accommodate sodium ions. By integrating the Co9S8@NC as negative electrode with a cellulose-derived porous hard carbon/graphene oxide composite as positive electrode and 1 M NaPF6 in diglyme as the electrolyte, the sodium-ion capacitor full cell can achieve energy densities of 101.4 and 45.8 Wh kg^-1 at power densities of 200 and 10,000 W kg^-1, respectively.展开更多
Due to less interference in biological imaging,nanomaterials with second near-infrared(NIR-II)window(950–1700 nm)emission have received tremendous attention.However,no reports on NIR-Ⅱ electrochemiluminescence(ECL)i...Due to less interference in biological imaging,nanomaterials with second near-infrared(NIR-II)window(950–1700 nm)emission have received tremendous attention.However,no reports on NIR-Ⅱ electrochemiluminescence(ECL)imaging exist because of the lack of high-efficiency NIR-Ⅱ ECL luminophores.Herein,we designed and synthesized a NaYbF4@SiO_(2) core–shell nanoparticle for the first time.展开更多
Polystyrene/polyaniline core-shell structure microspheres were synthesized in the presence of poly(sodium 4-styrenesulfonate) as stabilizer and hydrochloric acid as dopant to improve the processibility of conducting...Polystyrene/polyaniline core-shell structure microspheres were synthesized in the presence of poly(sodium 4-styrenesulfonate) as stabilizer and hydrochloric acid as dopant to improve the processibility of conducting polyaniline. ARer the one-pot reacting process, the product was easily purified by washing with water. The polyaniline shell covering the polystyrene sphere surface was confirmed with FT-IR and X-ray photoelectron spectroscopy. The conductivity of the polyaniline-coated polystyrene particles was 0.0017 S/cm and increased to 0.1 S/cm after being doped in the HCI vapor. The morphology of the microspheres was characterized by TEM and SEM. The particles show a more uniform and smooth surface than previous particles.展开更多
The near-surface structure of the Pt-based alloy including the surface and subsurface structures is prominent to their electrocatalytic performance.Modulating the near-surface structure of PtCo intermetallics with sma...The near-surface structure of the Pt-based alloy including the surface and subsurface structures is prominent to their electrocatalytic performance.Modulating the near-surface structure of PtCo intermetallics with small particle size could efficiently optimize the binding force between Pt and oxygen and finally enhance its oxygen reduction reaction(ORR)performance.Here we simultaneously achieve the size controlling and surface modulation of intermetallic nanoparticles(NPs)in a weak-oxidative confined space with abundant uncoordinated oxygen atoms.1–2 atomic layers of concave Pt-rich surface were successfully constructed on 4 nm L1_(0)-PtCo core after removing Co–O species which is derived from the segregation of the subsurface Co to the surface induced by the uncoordinated oxygen atoms.Owing to the elaborate structure,PtCo-1000/C catalyst shows significant improvement in both activity(1.290 A∙mg_(Pt)^(−1)and 1.529 mA∙cm_(Pt)^(−2) at 0.9 V vs.reversible hydrogen electrode(RHE))and stability(85.2%of initial mass activity after accelerated degression tests(ADTs))even the production is scaled up to gram level.Density functional theory calculations suggest that the cave Pt site optimizes the protonation of*O,which finally boosts the ORR performance.展开更多
In this work,we proposed a novel strategy for the photocatalytic degradation of the target pollutants tetracycline(TC)and methylene blue(MB)using core–shell dual metal-organic frameworks(MOFs)composites.A series of m...In this work,we proposed a novel strategy for the photocatalytic degradation of the target pollutants tetracycline(TC)and methylene blue(MB)using core–shell dual metal-organic frameworks(MOFs)composites.A series of mesoporous composites MIL-53@UiO-66 were synthesized by solvent-thermal synthesis via coating UiO-66 on the surface of MIL-53.The results show that under the same degradation conditions,only 30 and 15 min are needed to degrade 93%of TC and 96%of MB in the photo-Fenton reaction system,respectively.The amorphous shell layer brings stronger adsorption to the catalyst.MIL-53@UiO-66 composites with equalizing Fermi level are formed to promote photon absorption and electron transfer.Meanwhile,the MIL-53@UiO-66 composites with excellent stability will be a promising catalyst for environmental remediation.展开更多
The synthesis of semiconductor nanocrystalline networks using weak capping ligands in aqueous media has been demonstrated.Carbohydrates,includingβ-cyclodextrin,D-(+)-glucose,D-glucosamine,lactobionic acid,sucrose,and...The synthesis of semiconductor nanocrystalline networks using weak capping ligands in aqueous media has been demonstrated.Carbohydrates,includingβ-cyclodextrin,D-(+)-glucose,D-glucosamine,lactobionic acid,sucrose,and starch were chosen as weak ligands to facilitate the formation of PbTe nanoparticle networks.The nanoparticle size,ranging from 5 nm to 30 nm,can be tuned by manipulating the temperature and concentration.Through a similar strategy,more complicated nanostructures including carbohydrate spheres@PbTe core-shell structures and Te@carbohydrate@PbTe multilayered submicron cables have been fabricated.This is a general approach which can be easily extended to the fabrication of other semiconductor networks,including PbSe and Bi2Te3 using carbohydrates and ethylenediaminetetraacetic acid(EDTA),respectively,as ligands.展开更多
The development of highly efficient and stable Pd-based catalysts is crucial to improve their sluggish oxygen reduction reaction(ORR)kinetics in acid media.To improve ORR activity and utilization efficiency of Pd,an i...The development of highly efficient and stable Pd-based catalysts is crucial to improve their sluggish oxygen reduction reaction(ORR)kinetics in acid media.To improve ORR activity and utilization efficiency of Pd,an ideal catalyst should have ORR-favorable chemical environment,optimized geometric structure,and long periods of operation.In this work,we first synthesize a novel trimetallic Au@PdPb core–shell catalyst consisting of PdPb alloy nano-layers grown on the surface of ultrathin Au nanowires(NWs)by a two-step water-bath method.The Au@PdPb NWs have the merits of anisotropic one-dimensional nanostructure,high utilization efficiency of Pd atoms and doping of Pb atoms.Because of the structural and multiple compositional advantages,Au@PdPb NWs exhibit remarkably enhanced ORR activity with a high haIf-wave potential(0.827 V),much better than those of commercial Pd black(0.788 V)and bimetallic Au@Pd NWs(0.803 V).Moreover,Au@PdPb NWs display better electrocatalytic stability for the ORR than those of Pd black and Au@Pd NWs.This study demonstrates the validity of our approach for deriving highly ORR-active Pd-based catalysts by modifying their structure and composition.展开更多
基金The authors appreciate support by the Natural Science Foundation of Anhui Province(No.1908085ME147)Projects of International Cooperation and Exchanges in Anhui Provincial Key Project of Research(No.202004b11020010)+2 种基金Shenzhen Basic Research Program(Nos.JCYJ20190808141611189,JCYJ20170818100134570,and JCYJ20160422091418366)Basic and applied basic research fund of Guangdong Province(No.2020A1515011018)we are grateful to Instrumental Analysis Center of Shenzhen University(Xili Campus)for the help with TEM,and thanks for technical support by Ceshigo Research Service Agency(www.ceshigo.com)for XAS,ACSTEM and DFT/MD.
文摘In this paper,we use microwave reduction strategy to synthesize a new bi-functional sulfur host material at the service of cathode substrate for lithium-sulfur batteries(LSBs),the composite is made of hierarchical porous carbon foam supported carbon-encapsulated chromium carbide nano-particles(Cr_(3)C_(2)@C/HPCF),in which the well-distributed conductive Cr_(3)C_(2) nano-particles can act as powerful chemical adsorbent and are effective in restraining the shuttle effect of lithium polysulfides(LiPSs).Test results show that the Cr_(3)C_(2)@C/HPCF based sulfur electrodes with 75 wt.%of sulfur exhibit a high initial discharging capacity of 1,321.1 mAh·g^(−1) at 0.1 C(3.5 mg·cm^(−2)),and a reversible capacity can still maintain stability at 1,002.1 mAh·g^(−1) after 150 cycles.Even increasing the areal sulfur loading to 4 mg·cm^(−2),the electrodes can still deliver an initial discharging capacity of 948.0 mAh·g^(−1) at 0.5 C with ultra-slow capacity decay rate of 0.075%per cycle during 500 cycles.Furthermore,the adsorption energy between the Cr_(3)C_(2) surface and LiPSs as well as theoretic analysis based on first-principles is also investigated.
基金Project supported by the National Natural Science Foundation of China (Grant No 50641006) and the Science Foundation of Education Commission of Beijing, China.
文摘In this paper, Fe30Pt70/Fe3O4 core/shell nanoparticles were synthesized by chemical routine and the layered polyethylenimine (PEI)-Fe30Pt70/Fe3O4 structure was constructed by molecule-mediated self-assembly technique. The dimension of core/shell structured nanoparticles was that of 4nm core and 2 nm shell. After annealing under a flow of forming gas (50%Ar2+30%H2) for 1 h at or above 400℃, the iron oxide shell was reduced to Fe and diffused to Pt-rieh core, which leaded to the formation of L1. phase FePt at low temperature. The x-ray diffraction results and magnetic properties measurement showed that the chemical ordering temperature of Fe30Pt70/Fe3O4 core/shell nanoparticles assembly can be reduced to as low as 400℃. The sample annealed at 400℃ showed the eoereivity of 4KOe with the applied field of 1.5T. The core/shell structure was suggested to be an effective way to reduce the ordering temperature obviously.
文摘LaF_3:Yb^(3 +),Er^(3 +) nanoparticles were successfully synthesized using solvothermal treatment,and LaF_3:Yb^(3 +),Er^(3 +) /SiO_2 core /shell nanoparticles were also prepared with reverse microemulsion technique.The crystal structure,morphology and photoluminescence properties of as-prepared core /shell nanoparticles were investigated by X-ray diffraction,transmission electron microscopy and fluorescence spectrophotometer.The results showed that LaF_3:Yb^(3 +),Er^(3 +) nanoparticles are of hexagonal structure and SiO_2 shell is amorphous.The size of LaF_3:Yb^(3 +),Er^(3 +) nanoparticles is 13 nm and the LaF_3:Yb^(3 +),Er^(3 +) /SiO_2 nanoparticles present clearly a core /shell structure with 12 nm shell thickness.The solubility of LaF_3:Yb^(3 +),Er^(3 +) nanocrystals in water and the biocompatibility are both improved by the SiO_2 shell.The upconversion luminescence spectra suggested that the SiO_2 shell has small effect on the upconversion luminescence properties of the LaF_3:Yb^(3 +),Er^(3 +) nanocrystals.The core /shell structure LaF_3:Yb^(3 +),Er^(3 +) /SiO_2 nanoparticles are expected to be used in biological applications.
基金supported by National Natural Science Foundation of China(21972017)the“Scientific and Technical Innovation Action Plan”Hong Kong,MacaoTaiwan Science&Technology Cooperation Project of Shanghai Science and Technology Committee(19160760600).
文摘Rational construction of highly efficient and cheap bifunctional electrocatalysts to boost both oxygen evolution reaction(OER)and oxygen reduction reaction(ORR)is extremely essential for the wide application of rechargeable metal-air battery.In this work,we design a core-shell structural catalyst of CoNi dual-metal embedded in nitrogen doped porous carbon(NPC,CoNi@NPC),which is developed via the pyrolysis of CoNiMOFs,assisting by mesoporous SiO_(2) to effectively inhibit the aggregation of metal sites.Consequently,the asprepared CoNi@NPC manifests good ORR activity with half-wave potential up to 0.77 V.Specifically,the CoNi@NPC gives a very low OER over-potential of merely 101 mV in 6 M KOH along with high stability,outperforming the commercial Pt/C-RuO_(2).Moreover,the home-made zinc air battery with CoNi@NPC air cathode demonstrates excellent stability over long-term charging–discharging test,and delivers the maximum power density of 224 mW cm^(-2).The enhanced high performance of CoNi@NPC bifunctional catalyst for both ORR and OER can be ascribed to its unique core-shell structure and strong synergistic effect between the dual-bimetal active sites and the heteroatom doped carbon.This work opens a new avenue for the rational design of nonprecious metal bifunctional catalysts for rechargeable metal-air battery.
基金the National Natural Science Foundation of China(Grant No.11802160)。
文摘Rupturing the alumina shell(shell-breaking)is a prerequisite for releasing energy from aluminum powder.Thermal stress overload in a high-temperature environment is an important factor in the rupture of the alumina shell.COMSOL Multiphysics was used to simulate and analyze the shell-breaking response of micron-scale aluminum particles with different particle sizes at 650℃in vacuum.The simulation results show that the thermal stability time and shell-breaking response time of 10μm–100μm aluminum particles are 0.15μs–11.44μs and 0.08μs–3.94μs,respectively.They also reveal the direct causes of shell breaking for aluminum particles with different particle sizes.When the particle size is less than 80μm,the shell-breaking response is a direct result of compressive stress overload.When the particle size is between80μm and 100μm,the shell-breaking response is a direct result of tensile stress overload.This article provides useful guidance for research into the energy release of aluminum powder.
基金the Natural Science Foundation of Shandong Province of China (Grant No.ZR2020MB024)for financially supporting this work.
文摘The bind-free carbon cloth-supported electrodes hold the promises for high-performance electrochemical capacitors with high specific capacitance and good cyclic stability.Considering the close connection between their performance and the amount of carbon material loaded on the electrodes,in this work,NiCo_(2)O_(4) nanowires were firstly grown on the substrate of active carbon cloth to provide the necessary surface area in the longitudinal direction.Then,the quinone-rich nitrogen-doped carbon shell structure was formed around NiCo_(2)O_(4) nanowires,and the obtained composite was used as electrode for electric double layer capacitor.The results showed that the composite electrode displayed an area-specific capacitance of 1794 mF·cm^(-2) at the current density of 1 mA·cm^(-2).The assembled symmetric electric double layer capacitor achieved a high energy density of 6.55 mW·h·cm^(-3) at a power density of 180 mW·cm^(-3).The assembled symmetric capacitor exhibited a capacitance retention of 88.96%after 10000 charge/discharge cycles at the current density of 20 mA·cm^(-2).These results indicated the potentials in the preparation of the carbon electrode materials with high energy density and good cycling stability.
基金The authors thank Dr.Hong Zhai for her technical support in material characterizationsThis work was funded by National Key R&D Program of China(No.2018YFC1106001)+2 种基金National Natural Science Foundation of China(51903255 and 52073314)The Key Areas Research and Development Program of Guangdong(2020B1111150003 and 2019B020235001)Science and Technology Program of Guangzhou City(201904010364).
文摘Advanced biomaterial-based strategies for treatment of peripheral nerve injury require precise control over both topological and biological cues for facilitating rapid and directed nerve regeneration.As a highly bioactive and tissue-specifc natural material,decellularized extracellular matrix(dECM)derived from peripheral nerves(decellularized nerve matrix,DNM)has drawn increasing attention in the feld of regenerative medicine,due to its outstanding capabilities in facilitating neurite outgrowth and remyelination.To induce and maintain sufcient topological guidance,electrospinning was conducted for fabrication of axially aligned nanofbers consisting of DNM and poly(ε-caprolactone)(PCL).Core–shell structured fbers were prepared by coaxial electrospinning using DNM as the shell and PCL as the core.Compared to the aligned electrospun fbers using preblended DNM/PCL,the core–shell structured fbers exhibited lower tensile strength,faster degradation,but considerable toughness for nerve guidance conduit preparation and relatively intact fbrous structure after long-term degradation.More importantly,the full DNM surface coverage of the aligned core–shell fbers efectively promoted axonal extension and Schwann cells migration.The DNM contents further triggered neurite bundling and myelin formation toward nerve fber maturation and functionalization.Herein,we not only pursue a multi-functional scafold design for nerve regeneration,a detailed comparison between core–shell structured and preblended electrospinning of DNM/PCL composites was also provided as an applicable paradigm for advanced tissue-engineered strategies using dECM-based biomaterials.
基金Supported by Program for the National Natural Science Foundation of China (Nos. 51577021 and U1704253)the Fundamental Research Funds for the Central Universities (DUT17GF107)
文摘Crystalline Fe/MnO@C core–shell nanocapsules inlaid in porous amorphous carbon matrix(FMCA)was synthesized successfully with a novel confinement strategy.The heterogeneous Fe/MnO nanocrystals are with approximate single-domain size which gives rise to natural resonance in 2–18 GHz.The addition of MnO2 confines degree of graphitization catalyzed by iron and contributes to the formation of amorphous carbon.The heterogeneous materials composed of crystalline–amorphous structures disperse evenly and its density is significantly reduced on account of porous properties.Meanwhile,adjustable dielectric loss is achieved by interrupting Fe core aggregation and stacking graphene conductive network.The dielectric loss synergistically with magnetic loss endows the FMCA enhanced absorption.The optimal reflection loss(RL)is up to−45 dB,and the effective bandwidth(RL<−10 dB)is 5.0 GHz with 2.0 mm thickness.The proposed confinement strategy not only lays the foundation for designing high-performance microwave absorber,but also offers a general duty synthesis method for heterogeneous crystalline–amorphous composites with tunable composition in other fields.
基金supported by the Grant-in-Aid for Scientific Research (KAKENHI) program, Japan (C, Grant Number 15K05597)Takahashi Industrial and Economic Research Foundation (Takahashi Grant Number 06-003-154)
文摘Electrode material based on a novel core–shell structure consisting of NiCoS(NCS) solid fiber core and Mn S(MS) sheet shell(NCS@MS) in situ grown on carbon cloth(CC) has been successfully prepared by a simple sulfurization-assisted hydrothermal method for high performance supercapacitor. The synthesized NiCoS@Mn S/CC electrode shows high capacitance of 1908.3 F gat a current density of 0.5 A gwhich is higher than those of NiCoSand Mn S at the same current density. A flexible all-solid-state asymmetric supercapacitor(ASC) is constructed by using NiCoS@Mn S/CC as positive electrode, active carbon/CC as negative electrode and KOH/poly(vinyl alcohol)(PVA) as electrolyte. The optimized ASC shows a maximum energy density of 23.3 Wh kgat 1 A g, a maximum power density of about7.5 kw kgat 10 A gand remarkable cycling stability. After 9000 cycles, the ASC still exhibited67.8% retention rate and largely unchanged charge/discharge curves. The excellent electrochemical properties are resulted from the novel core–shell structure of the NiCoS@Mn S/CC electrode, which possesses both high surface area for Faraday redox reaction and superior kinetics of charge transport. The NiCoS@Mn S/CC electrode shows a promising potential for energy storage applications in the future.
基金supported by the Samsung Electro-Mechanics Co.Ltd.through the Center for Advanced MLCC-Manufacturing Processes and also by the Priority Research Centers Program(Grant No.2012-048034)through the National Research Foundation of Korea(NRF)funded by the Ministry of Education,Science and Technology(MEST),Korea.
文摘Two sets of(Mg,Y)-doped BaTiO_(3)samples were prepared to investigate the effects of the core/shell volumetric ratio on the dielectric-temperature behavior of BaTiO3:one set with samples of the same grain size but different core sizes and the other with samples of the same core size but different shell thicknesses.The microstructural variation of the samples was characterized and their dielectric properties were measured.For both sets of samples,the temperature stability of the dielectric properties was generally improved with a reduction of the volumetric shell ratio regardless of the grain and core sizes.There existed,however,a limit of the reduction;for the studied range,shell thickness of one third of the core radius appeared to be an optimum thickness for the given amounts of dopants.It was concluded that the volumetric shell ratio should be optimized so as not to exceed a specific limit,for our case two thirds of the grain volume,to secure temperature stability of the dielectric properties of BaTiO_(3).
基金the National Natural Science Foundation of China(Nos.31530010 and 21401168)the Special Project of Guangdong Province to Introduce Innovation and Entrepreneurship Team(No.2016ZT06N467)is acknowledged.
文摘Elemental state matter-heteroatom-doped carbon composites are of great importance for the development of anode in lithium ion batteries(LIBs).In this article,metal–organic frameworks(MOFs)are adopted as precursor to prepare Co composites via metallurgical pyrolysis under controllable conditions.The obtained nitrogen-doped porous carbon-Co nanocomposite possesses core–shell structure(Co@C–N).Co@C–N exhibits the best Li storage performances as anode active matter.After the 200th cycles at current density of 0.2 A g^(-1),a reversible capacity of 870 mAh g^(-1)is retained.A reversible capacity of 275 mAh g^(-1)still maintains with 5 A g^(-1).Co@C–N presents a high reversible capacity with excellent cycle stability.Considering the corresponding experimental and theoretical results,the Co0-based N-doped porous carbon composite is proposed to work as LIBs anode matter.These results provide a new design idea for electrode matters of metallic ion battery,and demonstrate that MOFs pyrolysis is an effective method for the construction of elemental state anode materials.
基金This work was financially supported by the National Natural Science Foundation of China(No.20104008).
文摘Sub-micron sized phenolic epoxy resin waterborne particles were prepared by phase inversion emulsification. Micro-phase separation occurred during the curing process at high temperature. The as-prepared samples possessed one glass transition temperature (Tg) and two exothermal processes during DSC heating scannings. After being thermally treated above the exothermal peak temperature, they possessed two glass transition temperatures with the disappearance of exothermal peaks, whilst a core/shell structure was formed. This was likely related with the outward diffusion of reactive oligomers to the outer layer of particles.
基金supported by The Australian Research Council(ARC)under project FL170100101The University of Queensland for o ering UQI Scholarship
文摘Conversion-type anode materials with a high charge storage capability generally su er from large volume expansion, poor electron conductivity, and sluggish metal ion transport kinetics. The electrode material described in this paper, namely cobalt sulphide nanoparticles encapsulated in carbon cages(Co9S8@NC), can circumvent these problems. This electrode material exhibited a reversible sodium-ion storage capacity of 705 mAh g^-1 at 100 mA g^-1 with an extraordinary rate capability and good cycling stability. Mechanistic study using the in situ transmission electron microscope technique revealed that the volumetric expansion of the Co9S8 nanoparticles is bu ered by the carbon cages, enabling a stable electrode–electrolyte interface. In addition, the carbon shell with high-content doped nitrogen significantly enhances the electron conductivity of the Co9S8@NC electrode material and provides doping-induced active sites to accommodate sodium ions. By integrating the Co9S8@NC as negative electrode with a cellulose-derived porous hard carbon/graphene oxide composite as positive electrode and 1 M NaPF6 in diglyme as the electrolyte, the sodium-ion capacitor full cell can achieve energy densities of 101.4 and 45.8 Wh kg^-1 at power densities of 200 and 10,000 W kg^-1, respectively.
基金the National Natural Science Foundation of China(grant no.22034003)the Excellent Research Program of Nanjing University(no.ZYJH004).
文摘Due to less interference in biological imaging,nanomaterials with second near-infrared(NIR-II)window(950–1700 nm)emission have received tremendous attention.However,no reports on NIR-Ⅱ electrochemiluminescence(ECL)imaging exist because of the lack of high-efficiency NIR-Ⅱ ECL luminophores.Herein,we designed and synthesized a NaYbF4@SiO_(2) core–shell nanoparticle for the first time.
文摘Polystyrene/polyaniline core-shell structure microspheres were synthesized in the presence of poly(sodium 4-styrenesulfonate) as stabilizer and hydrochloric acid as dopant to improve the processibility of conducting polyaniline. ARer the one-pot reacting process, the product was easily purified by washing with water. The polyaniline shell covering the polystyrene sphere surface was confirmed with FT-IR and X-ray photoelectron spectroscopy. The conductivity of the polyaniline-coated polystyrene particles was 0.0017 S/cm and increased to 0.1 S/cm after being doped in the HCI vapor. The morphology of the microspheres was characterized by TEM and SEM. The particles show a more uniform and smooth surface than previous particles.
基金the National Natural Science Foundation of China(Nos.22279082 and 21908148)the Natural Science Foundation of Sichuan(No.2022NSFSC1247)。
文摘The near-surface structure of the Pt-based alloy including the surface and subsurface structures is prominent to their electrocatalytic performance.Modulating the near-surface structure of PtCo intermetallics with small particle size could efficiently optimize the binding force between Pt and oxygen and finally enhance its oxygen reduction reaction(ORR)performance.Here we simultaneously achieve the size controlling and surface modulation of intermetallic nanoparticles(NPs)in a weak-oxidative confined space with abundant uncoordinated oxygen atoms.1–2 atomic layers of concave Pt-rich surface were successfully constructed on 4 nm L1_(0)-PtCo core after removing Co–O species which is derived from the segregation of the subsurface Co to the surface induced by the uncoordinated oxygen atoms.Owing to the elaborate structure,PtCo-1000/C catalyst shows significant improvement in both activity(1.290 A∙mg_(Pt)^(−1)and 1.529 mA∙cm_(Pt)^(−2) at 0.9 V vs.reversible hydrogen electrode(RHE))and stability(85.2%of initial mass activity after accelerated degression tests(ADTs))even the production is scaled up to gram level.Density functional theory calculations suggest that the cave Pt site optimizes the protonation of*O,which finally boosts the ORR performance.
基金the funds awarded by the National Natural Science Foundation of China(Nos.21878017 and 51773012).
文摘In this work,we proposed a novel strategy for the photocatalytic degradation of the target pollutants tetracycline(TC)and methylene blue(MB)using core–shell dual metal-organic frameworks(MOFs)composites.A series of mesoporous composites MIL-53@UiO-66 were synthesized by solvent-thermal synthesis via coating UiO-66 on the surface of MIL-53.The results show that under the same degradation conditions,only 30 and 15 min are needed to degrade 93%of TC and 96%of MB in the photo-Fenton reaction system,respectively.The amorphous shell layer brings stronger adsorption to the catalyst.MIL-53@UiO-66 composites with equalizing Fermi level are formed to promote photon absorption and electron transfer.Meanwhile,the MIL-53@UiO-66 composites with excellent stability will be a promising catalyst for environmental remediation.
基金This work was supported by Toyota Motor Engineering and Manufacturing North America
文摘The synthesis of semiconductor nanocrystalline networks using weak capping ligands in aqueous media has been demonstrated.Carbohydrates,includingβ-cyclodextrin,D-(+)-glucose,D-glucosamine,lactobionic acid,sucrose,and starch were chosen as weak ligands to facilitate the formation of PbTe nanoparticle networks.The nanoparticle size,ranging from 5 nm to 30 nm,can be tuned by manipulating the temperature and concentration.Through a similar strategy,more complicated nanostructures including carbohydrate spheres@PbTe core-shell structures and Te@carbohydrate@PbTe multilayered submicron cables have been fabricated.This is a general approach which can be easily extended to the fabrication of other semiconductor networks,including PbSe and Bi2Te3 using carbohydrates and ethylenediaminetetraacetic acid(EDTA),respectively,as ligands.
基金supported by the Academic Research Fund(AcRF)Tier 1 Grant(No.RG105/19)from the Ministry of Education in Singapore,the National Natural Science Foundation of China(No.21875112)and the China Scholarship Council(No.201906090199).
文摘The development of highly efficient and stable Pd-based catalysts is crucial to improve their sluggish oxygen reduction reaction(ORR)kinetics in acid media.To improve ORR activity and utilization efficiency of Pd,an ideal catalyst should have ORR-favorable chemical environment,optimized geometric structure,and long periods of operation.In this work,we first synthesize a novel trimetallic Au@PdPb core–shell catalyst consisting of PdPb alloy nano-layers grown on the surface of ultrathin Au nanowires(NWs)by a two-step water-bath method.The Au@PdPb NWs have the merits of anisotropic one-dimensional nanostructure,high utilization efficiency of Pd atoms and doping of Pb atoms.Because of the structural and multiple compositional advantages,Au@PdPb NWs exhibit remarkably enhanced ORR activity with a high haIf-wave potential(0.827 V),much better than those of commercial Pd black(0.788 V)and bimetallic Au@Pd NWs(0.803 V).Moreover,Au@PdPb NWs display better electrocatalytic stability for the ORR than those of Pd black and Au@Pd NWs.This study demonstrates the validity of our approach for deriving highly ORR-active Pd-based catalysts by modifying their structure and composition.