Lithium sulfide(Li_(2)S)is widely regarded as the next-generation cathode material for rechargeable batteries due to its satisfactory theoretical capacity and excellent compatibility with lithium-free anodes.However,t...Lithium sulfide(Li_(2)S)is widely regarded as the next-generation cathode material for rechargeable batteries due to its satisfactory theoretical capacity and excellent compatibility with lithium-free anodes.However,the large-scale applications of Li_(2)S cathodes are limited by the shuttle effect of soluble intermediate lithium polysulfides(LiPSs)and the sluggish redox kinetics of the interconversion between Li_(2)S and sulfur(S).Herein,we report novel nitrogen-doped carbon nanoflakes in-situ embedded with WN-Ni_(2)P heterostructures(WN-Ni_(2)P@NCN)as a multifunctional host to promote the cycling performance and reaction kinetics of Li_(2)S.After loading Li_(2)S,the WNNi_(2)P@NCN/Li_(2)S exhibits stable reversible capacity of 597mAh g^(-1)at 0.5 A g^(-1)over 150 cycles,and superior cycling stability over 800 cycles.The high reversible capacities,excellent cycling properties and superior reaction kinetics of WN-Ni_(2)P@NCN/Li_(2)S are attributed to the strong LiPSs fixation,remarkable catalytic activation and high electronic/ionic conductivity of the WN-Ni_(2)P@NCN framework,confirmed by the experiment and the density function theory calculation results.This work offers a new strategy for designing heterostructure nanoflakes with metal nitride and metal phosphide to facilitate the applications of advanced lithium-sulfur batteries.展开更多
The memory behavior in liquid crystals(LCs)that is characterized by low cost,large area,high speed,and high-density memory has evolved from a mere scientific curiosity to a technology that is being applied in a variet...The memory behavior in liquid crystals(LCs)that is characterized by low cost,large area,high speed,and high-density memory has evolved from a mere scientific curiosity to a technology that is being applied in a variety of commodities.In this study,we utilized molybdenum disulfide(MoS_(2))nanoflakes as the vip in a homotropic LCs host to modulate the overall memory effect of the hybrid.It was found that the MoS₂nanoflakes within the LCs host formed agglomerates,which in turn resulted in an accelerated response of the hybrids to the external electric field.However,this process also resulted in a slight decrease in the threshold voltage.Additionally,it was observed that MoS₂nanoflakes in a LCs host tend to align homeotropically under an external electric field,thereby accelerating the refreshment of the memory behavior.The incorporation of a mass fraction of 0.1%2μm MoS₂nanoflakes into the LCs host was found to significantly reduce the refreshing memory behavior in the hybrid to 94.0 s under an external voltage of 5 V.These findings illustrate the efficacy of regulating the rate of memory behavior for a variety of potential applications.展开更多
A series of N-doped carbon materials(NCs)were synthesized by using biomass citric acid and dicyandiamide as renewable raw materials via a facile onestep pyrolysis method. The characterization of microstructural featur...A series of N-doped carbon materials(NCs)were synthesized by using biomass citric acid and dicyandiamide as renewable raw materials via a facile onestep pyrolysis method. The characterization of microstructural features shows that the NCs samples are composed of few-layered graphene-like nanoflakes with controlled in situ N doping, which is attributed to the confined pyrolysis of citric acid within the interlayers of the dicyandiamide-derived g-C_3N_4 with high nitrogen contents. Evidently, the pore volumes of the NCs increased with the increasing content of dicyandiamide in the precursor. Among these samples, the NCs nanoflakes prepared with the citric acid/dicyandiamide mass ratio of 1:6, NC-6,show the highest N content of ~6.2 at%, in which pyridinic and graphitic N groups are predominant. Compared to the commercial Pt/C catalyst, the as-prepared NC-6 exhibits a small negative shift of ~66 mV at the half-wave potential, demonstrating excellent electrocatalytic activity in the oxygen reduction reaction. Moreover, NC-6 also shows better long-term stability and resistance to methanol crossover compared to Pt/C. The efficient and stable performance are attributed to the graphene-like microstructure and high content of pyridinic and graphitic doped nitrogen in the sample, which creates more active sites as well as facilitating charge transfer due to the close four-electron reaction pathway. The superior electrocatalytic activity coupled with the facile synthetic method presents a new pathway to cost-effective electrocatalysts for practical fuel cells or metal–air batteries.展开更多
A binder-free Ni3S2 electrode was prepared directly on a graphene-coated Ni foam （G/Ni） substrate through surface sulfiding of substrate using thiourea as the sulfur source in this work. The Ni3S2 showed a flower-li...A binder-free Ni3S2 electrode was prepared directly on a graphene-coated Ni foam （G/Ni） substrate through surface sulfiding of substrate using thiourea as the sulfur source in this work. The Ni3S2 showed a flower-like morphology and was uniformly distributed on the G/Ni surface. The flower-like Ni3S2 was composed of cross-arrayed nanoflakes with a diameter and a thickness of 1-2 μm and -50 nm, re- spectively. The free space in the flowers and the thin feature of Ni3S2 buffered the volume changes and relieved mechanical strain during re- peated cycling. The intimate contact with the Ni substrate and the fixing effect of graphene maintained the structural stability of the Ni3S2 electrode during cycling. The G/Ni-supported Ni3S2 maintained a reversible capacity of 250 mAh·g^-1 after 100 cycles at 50 mA·g^-1, demon- strating the good cycling stability as a result of the unique microstructure of this electrode material.展开更多
Herein, high-quality n-ZnO film layer on c-sapphire and well-crystallized tetragonal p-BiOCl nanoflakes on Cu foil are prepared, respectively. According to the absorption spectra, the bandgaps of n-ZnO and p-BiOCl are...Herein, high-quality n-ZnO film layer on c-sapphire and well-crystallized tetragonal p-BiOCl nanoflakes on Cu foil are prepared, respectively. According to the absorption spectra, the bandgaps of n-ZnO and p-BiOCl are confirmed as ~3.3 and~3.5 eV, respectively. Subsequently, a p-BiOCl/n-ZnO heterostructural photodetector is constructed after a facile mechanical bonding and post annealing process. At –5 V bias, the photocurrent of the device under 350 nm irradiation is ~800 times higher than that in dark, which indicates its strong UV light response characteristic. However, the on/off ratio of In–ZnO–In photodetector is ~20 and the Cu–BiOCl–Cu photodetector depicts very weak UV light response. The heterostructure device also shows a short decay time of 0.95 s, which is much shorter than those of the devices fabricated from pure ZnO thin film and BiOCl nanoflakes. The p-BiOCl/n-ZnO heterojunction photodetector provides a promising pathway to multifunctional UV photodetectors with fast response, high signal-to-noise ratio, and high selectivity.展开更多
Rational design of advanced cost-effective electrocatalysts is vital for the development of water electrolysis. Herein, we report a novel binder-free efficient CoS@CoOcore/shell electrocatalysts for oxygen evolution r...Rational design of advanced cost-effective electrocatalysts is vital for the development of water electrolysis. Herein, we report a novel binder-free efficient CoS@CoOcore/shell electrocatalysts for oxygen evolution reaction（OER） via a combined hydrothermal-sulfurization method. The sulfurized net-like CoSnanoflakes are strongly anchored on the CoOnanowire core forming self-supported binder-free core/shell electrocatalysts. Positive advantages including larger active surface area of CoSnanoflakes,and reinforced structural stability are achieved in the CoS@CoOcore/shell arrays. The OER performances of the CoS@CoOcore/shell arrays are thoroughly tested and enhanced electrocatalytic performance with lower over-potential(260 m V at 20 m A cm) and smaller Tafel slopes（56 mV dec-1） as well as long-term durability are demonstrated in alkaline medium. Our proposed core/shell smart design may provide a new way to construct other advanced binder-free electrocatalysts for applications in electrochemical catalysis.展开更多
SmCo6.6Nb0.4 nanoflakes with TbCu7 structure were successfully prepared by surfactant-assisted high energy ball milling （SA-HEBM） with heptane and oleic acid as milling medium. The microstructure, crystal structure ...SmCo6.6Nb0.4 nanoflakes with TbCu7 structure were successfully prepared by surfactant-assisted high energy ball milling （SA-HEBM） with heptane and oleic acid as milling medium. The microstructure, crystal structure and magnetic properties were stud- ied by scanning electron microscopy, X-ray diffraction, and vibrating sample magnetometer, respectively. The effects of ball milling time on the c-axis crystallographic alignment and coercivity of the nanoflakes were systematically investigated. The research showed that the nanoflakes had an average thickness of 100 nm, an average diameter of 1 μm, with an aspect ratio as high as 100. As the ball milling time increased from 2 to 8 h, the reflection peaks intensity ratio I（002y/I（10l）, which indicated the degree of c-axis crystal texture of the SmCo6.6Nbo.4 phase, increased first, reached a peak at 4 h, and then decreased. Meanwhile, the coercivity of the nanoflakes also increased first, reached a peak at 13.86 kOe for 4 h, and then decreased.展开更多
BiIO4 nanoflakes were successfully prepared through a facile hydrothermal method. The as-prepared BiIO4 was characterized by scanning electron microscope(SEM), high-resolution transmission electron microscopy(HRTEM), ...BiIO4 nanoflakes were successfully prepared through a facile hydrothermal method. The as-prepared BiIO4 was characterized by scanning electron microscope(SEM), high-resolution transmission electron microscopy(HRTEM), X-ray diffraction(XRD), energy-dispersive spectroscopy(EDS) and ultraviolet visible diffuse reflectance spectroscopy. BiIO4 nanoflakes showed excellent photocatalytic activity for the degradation of phenol solution under simulated solar irradiation. The influence of synthesis temperature on the morphology, size and photocatalytic performance of BiIO4 was investigated. BiIO4 prepared under 140 ℃ exhibited the highest removal rate of phenol under simulated solar light irradiation. In addition, the parametric studies such as the effect of catalyst loading and phenol solution pH were carried out to optimize the reaction conditions. The active species trapping experiment demonstrated that h+ and ·OH are the major active species during the photocatalytic process.展开更多
SnS2 nanoflakes were successfully synthesized via a simple hydrothermal process. The as-prepared SnS2 samples were characterized by X-ray diffraction（XRD）, scanning electron microscopy（SEM）, nitrogen adsorption-de...SnS2 nanoflakes were successfully synthesized via a simple hydrothermal process. The as-prepared SnS2 samples were characterized by X-ray diffraction（XRD）, scanning electron microscopy（SEM）, nitrogen adsorption-desorption isotherms, and UV-vis diffuse reflectance spectroscopy（DRS）. The photocatalytic activities of the as-prepared SnS2 nanoflakes under visible light irradiation（λ〉420 nm） were evaluated by the degradation of rhodamine B（Rh B）. The effect of hydrothermal temperatures on the photocatalytic efficiency of as-prepared SnS2 nanoflakes was investigated. The experimental result showed that SnS2 nanoflakes synthesized at the temprature of 160 o had higher photocatalytic efficiency and good photocatalytic stability.展开更多
We investigated the thickness effect on the photophysics and charge carrier kinetics of graphitic carbon nitride nanoflakes （g-CNN） by using ultraviolet visible diffuse reflectance spectroscopy, atomic force microsc...We investigated the thickness effect on the photophysics and charge carrier kinetics of graphitic carbon nitride nanoflakes （g-CNN） by using ultraviolet visible diffuse reflectance spectroscopy, atomic force microscopy, femtosecond transient absorption spectroscopy, and picosecond time-correlated single photon counting measurement. For the first time, we found that g-CNN displays a layer-dependent indirect bandgap and layer-dependent charge carrier kinetics.展开更多
We reported an effective method to synthesize In2S3 and Cu-doped In2S3 two-dimensional ultrathin nanoflakes by the hydrothermal method through tuning the Cu/In molar ratio. The transmission electron microscope images ...We reported an effective method to synthesize In2S3 and Cu-doped In2S3 two-dimensional ultrathin nanoflakes by the hydrothermal method through tuning the Cu/In molar ratio. The transmission electron microscope images showed that the products had ultrathin flake-like shape with wrinkling and rolling. The X-ray diffraction patterns indicated the crystal phase of nanoflakes was varied from β-In2S3 to tetragonal-Cu InS2 as the Cu/In molar ratio was increased. The In2S3 nanoflakes exhibited absorption band at 450 nm, while new absorption peaks in turn appeared at 550 nm and 670 nm as the Cu/In molar ratio was increased. In addition, the two-dimensional ultrathin nanoflakes exhibited intense photocurrent response.展开更多
We perform first-principles calculations and coherent laser-matter interaction analyses to investigate the laser-induced ultrafast spin flip on graphene nanoflakes(GNFs)with transition metal elements attached on the b...We perform first-principles calculations and coherent laser-matter interaction analyses to investigate the laser-induced ultrafast spin flip on graphene nanoflakes(GNFs)with transition metal elements attached on the boundary[TM&GNFs(TM=Fe,Co,Ni)].It is shown that the spin-flip process on TM&GNFs is highly influenced by the involved element species and the position attached to the nanoflakes.Furthermore,taking Ni&GNF as an example,the first-principles tensile test predicts that the variation of the C-Ni bond length plays an important role in the spin density distribution,especially for the low-lying magnetic states,and can therefore dominate the spin-flip processes.The fastest spin-flip scenario is achieved within 80 fs in a Ni&GNF structure under 10%tensile strain along the C-Ni bond.The local deformation modulation of spin flip provides the precursory guidance for further study of ultrafast magnetization control in GNFs,which could lead to potential applications in future integrated straintronic devices.展开更多
The effect of microforging on the processing of nanocrystalline FeSiB alloy flakes was studied in terms of microstructure and magnetic properties. The flakes microforged from amorphous precursor showed submicron thick...The effect of microforging on the processing of nanocrystalline FeSiB alloy flakes was studied in terms of microstructure and magnetic properties. The flakes microforged from amorphous precursor showed submicron thicknesses with the crystal size of about 15 nrn. The crystallite size during microforging was primarily determined by plastic deformation rather than fracturing and agglomeration. Unlike the general trend of coercivity reduction with annealing, the coercivity of the nanocrystalline flakes was slightly increased with increasing annealing temperature, which can be explained with the diffusion anisotropy of the magnetic moments resulting from the formation of Fe-atoms pairs. The magnetic rernanence （Mr） of the planar nanocrystalline flakes was measured to be about 26% of the saturation magnetization （Ms）, a significant increase from 2% of the initial amorphous precursor.展开更多
PrCo5 nanoflakes with strong texture and high coercivity of 8.15 kOe were prepared by surfactant-assisted ball milling with heat-treated starting powder. The thickness and length of the as-milled nanoflakes are mainly...PrCo5 nanoflakes with strong texture and high coercivity of 8.15 kOe were prepared by surfactant-assisted ball milling with heat-treated starting powder. The thickness and length of the as-milled nanoflakes are mainly in the ranges of 50–100 nm and 0.5–3 μm, respectively. The x-ray diffraction patterns demonstrate that the heat treatment can increase the single phase and crystallinity of the PrCo5 compound, and combined with the demagnetization curves, indicate that the single phase and crystallinity are important for preparing high-coercivity and strong-textured rare earth permanent magnetic nanoflakes. In addition, the coercivity mechanism of the as-milled PrCo5 nanoflakes is studied by the angle dependence of coercivity for an aligned sample and the field dependence of coercivity, isothermal（IRM） and dc demagnetizing（DCD）remanence curves for an unaligned sample. The results indicate that the coercivity is dominated by co-existing mechanisms of pinning and nucleation. Furthermore, exchange coupling and dipolar coupling also co-exist in the sample.展开更多
A distant-neighbor quantum-mechanical method is used to study the nonlinear optical wave mixing in graphene nanoflakes(GNFs),including sum-and difference-frequency generation,as well as four-wave mixing.Our analysis s...A distant-neighbor quantum-mechanical method is used to study the nonlinear optical wave mixing in graphene nanoflakes(GNFs),including sum-and difference-frequency generation,as well as four-wave mixing.Our analysis shows that molecular-scale GNFs support quantum plasmons in the visible spectrum region,and significant enhancement of nonlinear optical wave mixing is achieved.Specifically,the second-and third-order wave-mixing polarizabilities of GNFs are dramatically enhanced,provided that one(or more) of the input or output frequencies coincide with a quantum plasmon resonance.Moreover,by embedding a cavity into hexagonal GNFs,we show that one can break the structural inversion symmetry and enable otherwise forbidden second-order wave mixing,which is found to be enhanced by the quantum plasmon resonance too.This study reveals that the molecular-sized graphene could be used in the quantum regime for nanoscale nonlinear optical devices and ultrasensitive molecular sensors.展开更多
Adsorption of 1,3,5-triphenylbenzene （TPB） molecules on Cu（100） surface is studied using ultraviolet photo- electron spectroscopy （UPS） and density functional theory （DFT） calculations. Researches on the botto...Adsorption of 1,3,5-triphenylbenzene （TPB） molecules on Cu（100） surface is studied using ultraviolet photo- electron spectroscopy （UPS） and density functional theory （DFT） calculations. Researches on the bottom-up fabrication of graphene nanoflakes （GNFs） with TPB as a precursor on the Cu（100） surface are carried out based on UPS and DFT calculations. Three emission features d, e and f originating from the TPB molecules are located at 3.095, 7.326 and 9.349 eV below the Fermi level, respectively. With the increase of TPB coverage on the Cu（100） substrate, the work function decreases due to the formation of interfacial dipoles and charge （electron） rearrangement at the TPB/Cu（100） interface. Upon the formation of GNFs, five emission characteristic peaks of g, h, i, j and k originating from the GNFs are located at 1.100, 3.529, 6.984, 8.465 and 9.606eV below the Fermi level, respectively. Angle resolved ultraviolet photoelectron spectroscopy （ARUPS） and DFT calculations indicate that TPB molecules adopt a lying-down configuration with their molecular plane nearly parallel to the Cu（100） substrate at the monolayer stage. At the same time, the lying-down configuration for the GNFs on the Cu（100） surface is also unveiled by ARUPS and DFT calculations.展开更多
Oxygen vacancy plays vital roles in regulating the electronic and charge distribution of the oxygen deficient materials.Herein,abundant oxygen vacancies are created during assembling the two-dimensional(2D)ultra-thin ...Oxygen vacancy plays vital roles in regulating the electronic and charge distribution of the oxygen deficient materials.Herein,abundant oxygen vacancies are created during assembling the two-dimensional(2D)ultra-thin Bi_(2)MoO_(6) nanoflakes into three dimensional(3D)Bi_(2)MoO_(6) nanospheres,resulting in significantly improved performance for photocatalytical conversion of CO_(2) into liquid hydrocarbons.The increased performance is contributed by two primary sites,namely the abundant oxygen vacancy and the exposed molybdenum(Mo)atom induced by oxygen-migration,as revealed by the theoretical calculation.The oxygen vacancy(Ov)and uncovered Mo atom serving as dual binding sites for trapping CO_(2) molecules render the synchronous fixation-reduction process,resulting in the decline of activation energy for CO_(2) reduction from 2.15 eV on bulk Bi_(2)MoO_(6) to 1.42 eV on Ov-rich Bi_(2)MoO_(6).Such a striking decrease in the activation energy induces the efficient selective generation of liquid hydrocarbons,especially the methanol(C_(2)H_(5) OH)and ethanol(CH_(3) OH).The yields of CH_(3) OH and C_(2)H_(5) OH over the optimal Ov-Bi_(2)MoO_(6) is high up to 106.5 and 10.3μmol g^(-1) respectively,greatly outperforming that on the Bulk-Bi_(2)MoO_(6).展开更多
30-50 wt.%graphite nanoflakes(GNFs)/6061Al matrix composites were fabricated via spark plasma sintering(SPS)at 610℃.The effects of the sintering pressure and GNF content on the microstructure and properties of the co...30-50 wt.%graphite nanoflakes(GNFs)/6061Al matrix composites were fabricated via spark plasma sintering(SPS)at 610℃.The effects of the sintering pressure and GNF content on the microstructure and properties of the composites were investigated.The results indicated that interfacial reactions were inhibited during SPS because no Al4C3 was detected.Moreover,the agglomeration of the GNFs increased,and the distribution orientation of the GNFs decreased with increasing the GNF content.The relative density,bending strength,and coefficient of thermal expansion(CTE)of the composites decreased,while the thermal conductivity(TC)in the X−Y direction increased.As the sintering pressure increased,the GNFs deagglomerated and were distributed preferentially in the X−Y direction,which increased the relative density,bending strength and TC,and decreased the CTE of the composites.The 50wt.%GNFs/6061Al matrix composite sintered at 610℃ under 55 MPa demonstrated the best performance,i.e.,bending strength of 72 MPa,TC and CTE(RT−100℃)of 254 W/(m·K)and 8.5×10^(−6)K^(−1)in the X−Y direction,and 55 W/(m·K)and 9.7×10^(−6)K^(−1)in the Z direction,respectively.展开更多
Oxygen evolution reaction(OER)is the dominant step for plenty of energy conversion and storage technologies.However,the OER suffers from sluggish kinetics and high overpotential due to its complex 4‐electron/proton t...Oxygen evolution reaction(OER)is the dominant step for plenty of energy conversion and storage technologies.However,the OER suffers from sluggish kinetics and high overpotential due to its complex 4‐electron/proton transfer mechanism.Thus,developing efficient electrocatalysts is particularly urgent to accelerate OER catalysis but still remains a great challenge.Herein,we have synthesized the novel cobalt molybdate nanoflakes(CoMoO_(4)‐O_(v)‐n@GF)with adjustable oxygen vacancies contents by in situ constructing CoMoO_(4) nanoflakes on graphite felt(GF)and annealing treatment under the reduction atmosphere.The best‐performing CoMoO_(4)‐O_(v)‐2@GF with optimal oxygen vacancies content shows splendid electrocatalytic performance with the low overpotential(296 mV at 10 mA cm^(‒2))and also small Tafel slope(62.4 mV dec^(‒1))in alkaline solution,which are comparable to those of the RuO_(2)@GF.The experimental and the density functional theory calculations results reveal that the construction of optimal oxygen vacancies in CoMoO_(4) can expose more active sites,narrow the band‐gap to increase the electrical conductivity,and modulate the free energy of the OER‐related intermediates to accelerate OER kinetics,thus improving its intrinsic activity.展开更多
We study the spin-resolved transport in a two-terminal graphene nanoflake device with a Rashba spinorbit coupling region in the center of the device. The Green's function method is applied to the system and the sp...We study the spin-resolved transport in a two-terminal graphene nanoflake device with a Rashba spinorbit coupling region in the center of the device. The Green's function method is applied to the system and the spin transmission probability and the spin polarization in x, y, and z directions are calculated. It is found that the components of the spin polarization are antisymmetric functions of Fermi energy, which oscillate and decay to the zero with increasing the energy for all values of the Rashba strength. It is shown that by tuning the Rashba strength via a gate voltage and/or changing the size of the system, it is possible to control the sign and magnitude of the spin polarization. The system represented here is a typical candidate for full electrical spintronic devices based on the carbon materials that are used for spin filtration.展开更多
基金financially supported by the National Key R&D Program of China(No.2022YFB2502000)the National Natural Science Foundation of China(Nos.51902079,52072342,52377216 and 52102324)+3 种基金Anhui Provincial Natural Science Foundation(Nos.2008085QE271 and 2208085ME108)Excellent Research and Innovation Team of Anhui Universities(No.2022AH010096)Natural Science Research Project for Anhui Universities(No.2024AH051519)Hefei Institutes of Physical Science,Chinese Academy of Sciences Director's Fund(Nos.BJPY2023B04,YZJJ-GGZX-2022-01 and YZJJ202102)
文摘Lithium sulfide(Li_(2)S)is widely regarded as the next-generation cathode material for rechargeable batteries due to its satisfactory theoretical capacity and excellent compatibility with lithium-free anodes.However,the large-scale applications of Li_(2)S cathodes are limited by the shuttle effect of soluble intermediate lithium polysulfides(LiPSs)and the sluggish redox kinetics of the interconversion between Li_(2)S and sulfur(S).Herein,we report novel nitrogen-doped carbon nanoflakes in-situ embedded with WN-Ni_(2)P heterostructures(WN-Ni_(2)P@NCN)as a multifunctional host to promote the cycling performance and reaction kinetics of Li_(2)S.After loading Li_(2)S,the WNNi_(2)P@NCN/Li_(2)S exhibits stable reversible capacity of 597mAh g^(-1)at 0.5 A g^(-1)over 150 cycles,and superior cycling stability over 800 cycles.The high reversible capacities,excellent cycling properties and superior reaction kinetics of WN-Ni_(2)P@NCN/Li_(2)S are attributed to the strong LiPSs fixation,remarkable catalytic activation and high electronic/ionic conductivity of the WN-Ni_(2)P@NCN framework,confirmed by the experiment and the density function theory calculation results.This work offers a new strategy for designing heterostructure nanoflakes with metal nitride and metal phosphide to facilitate the applications of advanced lithium-sulfur batteries.
文摘The memory behavior in liquid crystals(LCs)that is characterized by low cost,large area,high speed,and high-density memory has evolved from a mere scientific curiosity to a technology that is being applied in a variety of commodities.In this study,we utilized molybdenum disulfide(MoS_(2))nanoflakes as the vip in a homotropic LCs host to modulate the overall memory effect of the hybrid.It was found that the MoS₂nanoflakes within the LCs host formed agglomerates,which in turn resulted in an accelerated response of the hybrids to the external electric field.However,this process also resulted in a slight decrease in the threshold voltage.Additionally,it was observed that MoS₂nanoflakes in a LCs host tend to align homeotropically under an external electric field,thereby accelerating the refreshment of the memory behavior.The incorporation of a mass fraction of 0.1%2μm MoS₂nanoflakes into the LCs host was found to significantly reduce the refreshing memory behavior in the hybrid to 94.0 s under an external voltage of 5 V.These findings illustrate the efficacy of regulating the rate of memory behavior for a variety of potential applications.
基金the financial support from the National Key Research and Development Program of China (2016YFB0700204)Natural Science Foundation of Jiangsu Province (No. BK20140472)+2 种基金NSFC (51602332, 51502327)Science and Technology Commission of Shanghai Municipality (15520720400, 15YF1413800, 14DZ2261203, 16DZ2260603)One Hundred Talent Plan of Chinese Academy of Sciences
文摘A series of N-doped carbon materials(NCs)were synthesized by using biomass citric acid and dicyandiamide as renewable raw materials via a facile onestep pyrolysis method. The characterization of microstructural features shows that the NCs samples are composed of few-layered graphene-like nanoflakes with controlled in situ N doping, which is attributed to the confined pyrolysis of citric acid within the interlayers of the dicyandiamide-derived g-C_3N_4 with high nitrogen contents. Evidently, the pore volumes of the NCs increased with the increasing content of dicyandiamide in the precursor. Among these samples, the NCs nanoflakes prepared with the citric acid/dicyandiamide mass ratio of 1:6, NC-6,show the highest N content of ~6.2 at%, in which pyridinic and graphitic N groups are predominant. Compared to the commercial Pt/C catalyst, the as-prepared NC-6 exhibits a small negative shift of ~66 mV at the half-wave potential, demonstrating excellent electrocatalytic activity in the oxygen reduction reaction. Moreover, NC-6 also shows better long-term stability and resistance to methanol crossover compared to Pt/C. The efficient and stable performance are attributed to the graphene-like microstructure and high content of pyridinic and graphitic doped nitrogen in the sample, which creates more active sites as well as facilitating charge transfer due to the close four-electron reaction pathway. The superior electrocatalytic activity coupled with the facile synthetic method presents a new pathway to cost-effective electrocatalysts for practical fuel cells or metal–air batteries.
基金financially supported by the Scientific and Technological Project of State Grid Corporation of China
文摘A binder-free Ni3S2 electrode was prepared directly on a graphene-coated Ni foam （G/Ni） substrate through surface sulfiding of substrate using thiourea as the sulfur source in this work. The Ni3S2 showed a flower-like morphology and was uniformly distributed on the G/Ni surface. The flower-like Ni3S2 was composed of cross-arrayed nanoflakes with a diameter and a thickness of 1-2 μm and -50 nm, re- spectively. The free space in the flowers and the thin feature of Ni3S2 buffered the volume changes and relieved mechanical strain during re- peated cycling. The intimate contact with the Ni substrate and the fixing effect of graphene maintained the structural stability of the Ni3S2 electrode during cycling. The G/Ni-supported Ni3S2 maintained a reversible capacity of 250 mAh·g^-1 after 100 cycles at 50 mA·g^-1, demon- strating the good cycling stability as a result of the unique microstructure of this electrode material.
基金supported by the National Natural Science Foundation of China (Grant No. 61705043, 51872050 and11811530065)the National Key Research and Development Program of China (Grant No. 2017YFA0204600)+2 种基金the Natural Science Foundation of Jiangsu Province (No. BK20160568)National Postdoctoral Science Foundation of China (Grant No.2017M611411, 2018M640338, 2018T110344 and2019T120299)the Ministry of Education Joint Fund for Equipment Pre-Research (6141A02033241)。
文摘Herein, high-quality n-ZnO film layer on c-sapphire and well-crystallized tetragonal p-BiOCl nanoflakes on Cu foil are prepared, respectively. According to the absorption spectra, the bandgaps of n-ZnO and p-BiOCl are confirmed as ~3.3 and~3.5 eV, respectively. Subsequently, a p-BiOCl/n-ZnO heterostructural photodetector is constructed after a facile mechanical bonding and post annealing process. At –5 V bias, the photocurrent of the device under 350 nm irradiation is ~800 times higher than that in dark, which indicates its strong UV light response characteristic. However, the on/off ratio of In–ZnO–In photodetector is ~20 and the Cu–BiOCl–Cu photodetector depicts very weak UV light response. The heterostructure device also shows a short decay time of 0.95 s, which is much shorter than those of the devices fabricated from pure ZnO thin film and BiOCl nanoflakes. The p-BiOCl/n-ZnO heterojunction photodetector provides a promising pathway to multifunctional UV photodetectors with fast response, high signal-to-noise ratio, and high selectivity.
基金supported by the National Natural Science Foundation of China (grant no. 51728204, 51772272 and 51502263)Qianjiang Talents Plan D (grant. no. QJD1602029)+2 种基金the Startup Foundation for Hundred-Talent Program of Zhejiang Universitysupport by the Program for Innovative Research Team in University of Ministry of Education of China (IRT13037)the Key Science and Technology Innovation Team of Zhejiang Province (2010R50013)
文摘Rational design of advanced cost-effective electrocatalysts is vital for the development of water electrolysis. Herein, we report a novel binder-free efficient CoS@CoOcore/shell electrocatalysts for oxygen evolution reaction（OER） via a combined hydrothermal-sulfurization method. The sulfurized net-like CoSnanoflakes are strongly anchored on the CoOnanowire core forming self-supported binder-free core/shell electrocatalysts. Positive advantages including larger active surface area of CoSnanoflakes,and reinforced structural stability are achieved in the CoS@CoOcore/shell arrays. The OER performances of the CoS@CoOcore/shell arrays are thoroughly tested and enhanced electrocatalytic performance with lower over-potential(260 m V at 20 m A cm) and smaller Tafel slopes（56 mV dec-1） as well as long-term durability are demonstrated in alkaline medium. Our proposed core/shell smart design may provide a new way to construct other advanced binder-free electrocatalysts for applications in electrochemical catalysis.
基金Project supported by the National High Technology Research and Development Program of China(2010AA03A402)the National Major Fundamental Research Program of China,Ministry of Science and Technology China(2010CB934600)the State Key Lab of Advanced Metals and Materials(2011-ZD02)
文摘SmCo6.6Nb0.4 nanoflakes with TbCu7 structure were successfully prepared by surfactant-assisted high energy ball milling （SA-HEBM） with heptane and oleic acid as milling medium. The microstructure, crystal structure and magnetic properties were stud- ied by scanning electron microscopy, X-ray diffraction, and vibrating sample magnetometer, respectively. The effects of ball milling time on the c-axis crystallographic alignment and coercivity of the nanoflakes were systematically investigated. The research showed that the nanoflakes had an average thickness of 100 nm, an average diameter of 1 μm, with an aspect ratio as high as 100. As the ball milling time increased from 2 to 8 h, the reflection peaks intensity ratio I（002y/I（10l）, which indicated the degree of c-axis crystal texture of the SmCo6.6Nbo.4 phase, increased first, reached a peak at 4 h, and then decreased. Meanwhile, the coercivity of the nanoflakes also increased first, reached a peak at 13.86 kOe for 4 h, and then decreased.
基金supported by the National Natural Science Foundation of China(No.21273034)Fuzhou Science and Technology Project(No.2017-G-90)the project of Fujian Provincial Department of Education(No.JAT170390)
文摘BiIO4 nanoflakes were successfully prepared through a facile hydrothermal method. The as-prepared BiIO4 was characterized by scanning electron microscope(SEM), high-resolution transmission electron microscopy(HRTEM), X-ray diffraction(XRD), energy-dispersive spectroscopy(EDS) and ultraviolet visible diffuse reflectance spectroscopy. BiIO4 nanoflakes showed excellent photocatalytic activity for the degradation of phenol solution under simulated solar irradiation. The influence of synthesis temperature on the morphology, size and photocatalytic performance of BiIO4 was investigated. BiIO4 prepared under 140 ℃ exhibited the highest removal rate of phenol under simulated solar light irradiation. In addition, the parametric studies such as the effect of catalyst loading and phenol solution pH were carried out to optimize the reaction conditions. The active species trapping experiment demonstrated that h+ and ·OH are the major active species during the photocatalytic process.
基金Funded by the National Natural Science Foundation of China(No.U1304520)the Education Department of Henan Province(2013GGJS-185)
文摘SnS2 nanoflakes were successfully synthesized via a simple hydrothermal process. The as-prepared SnS2 samples were characterized by X-ray diffraction（XRD）, scanning electron microscopy（SEM）, nitrogen adsorption-desorption isotherms, and UV-vis diffuse reflectance spectroscopy（DRS）. The photocatalytic activities of the as-prepared SnS2 nanoflakes under visible light irradiation（λ〉420 nm） were evaluated by the degradation of rhodamine B（Rh B）. The effect of hydrothermal temperatures on the photocatalytic efficiency of as-prepared SnS2 nanoflakes was investigated. The experimental result showed that SnS2 nanoflakes synthesized at the temprature of 160 o had higher photocatalytic efficiency and good photocatalytic stability.
基金Financial supports by the National Natural Science Foundation of China (No. 21373269)the Fundamental Research Funds for the Central Universities and the Research Funds of Renmin University of China(No. 10XNJ047)
文摘We investigated the thickness effect on the photophysics and charge carrier kinetics of graphitic carbon nitride nanoflakes （g-CNN） by using ultraviolet visible diffuse reflectance spectroscopy, atomic force microscopy, femtosecond transient absorption spectroscopy, and picosecond time-correlated single photon counting measurement. For the first time, we found that g-CNN displays a layer-dependent indirect bandgap and layer-dependent charge carrier kinetics.
基金Supported by the National Key Research&Development Program of China(2017YFA0303402)the Large-Scale Instrument and Equipment Sharing Foundation of Wuhan University
文摘We reported an effective method to synthesize In2S3 and Cu-doped In2S3 two-dimensional ultrathin nanoflakes by the hydrothermal method through tuning the Cu/In molar ratio. The transmission electron microscope images showed that the products had ultrathin flake-like shape with wrinkling and rolling. The X-ray diffraction patterns indicated the crystal phase of nanoflakes was varied from β-In2S3 to tetragonal-Cu InS2 as the Cu/In molar ratio was increased. The In2S3 nanoflakes exhibited absorption band at 450 nm, while new absorption peaks in turn appeared at 550 nm and 670 nm as the Cu/In molar ratio was increased. In addition, the two-dimensional ultrathin nanoflakes exhibited intense photocurrent response.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11872309,12172293,and 11504223)the Natural Science Basic Research Plan in Shaanxi Province,China(Grant No.2020JM-120)the Program of China Scholarships Council(Grant No.201906295029).
文摘We perform first-principles calculations and coherent laser-matter interaction analyses to investigate the laser-induced ultrafast spin flip on graphene nanoflakes(GNFs)with transition metal elements attached on the boundary[TM&GNFs(TM=Fe,Co,Ni)].It is shown that the spin-flip process on TM&GNFs is highly influenced by the involved element species and the position attached to the nanoflakes.Furthermore,taking Ni&GNF as an example,the first-principles tensile test predicts that the variation of the C-Ni bond length plays an important role in the spin density distribution,especially for the low-lying magnetic states,and can therefore dominate the spin-flip processes.The fastest spin-flip scenario is achieved within 80 fs in a Ni&GNF structure under 10%tensile strain along the C-Ni bond.The local deformation modulation of spin flip provides the precursory guidance for further study of ultrafast magnetization control in GNFs,which could lead to potential applications in future integrated straintronic devices.
基金supported by INHA Technical College under a 2010-Research Grant
文摘The effect of microforging on the processing of nanocrystalline FeSiB alloy flakes was studied in terms of microstructure and magnetic properties. The flakes microforged from amorphous precursor showed submicron thicknesses with the crystal size of about 15 nrn. The crystallite size during microforging was primarily determined by plastic deformation rather than fracturing and agglomeration. Unlike the general trend of coercivity reduction with annealing, the coercivity of the nanocrystalline flakes was slightly increased with increasing annealing temperature, which can be explained with the diffusion anisotropy of the magnetic moments resulting from the formation of Fe-atoms pairs. The magnetic rernanence （Mr） of the planar nanocrystalline flakes was measured to be about 26% of the saturation magnetization （Ms）, a significant increase from 2% of the initial amorphous precursor.
基金Project supported by the National Basic Research Program of China(Grant No.2014CB643702)the National Natural Science Foundation of China(Grant No.51401235)Beijing Natural Science Foundation,China(Grant No.2152034)
文摘PrCo5 nanoflakes with strong texture and high coercivity of 8.15 kOe were prepared by surfactant-assisted ball milling with heat-treated starting powder. The thickness and length of the as-milled nanoflakes are mainly in the ranges of 50–100 nm and 0.5–3 μm, respectively. The x-ray diffraction patterns demonstrate that the heat treatment can increase the single phase and crystallinity of the PrCo5 compound, and combined with the demagnetization curves, indicate that the single phase and crystallinity are important for preparing high-coercivity and strong-textured rare earth permanent magnetic nanoflakes. In addition, the coercivity mechanism of the as-milled PrCo5 nanoflakes is studied by the angle dependence of coercivity for an aligned sample and the field dependence of coercivity, isothermal（IRM） and dc demagnetizing（DCD）remanence curves for an unaligned sample. The results indicate that the coercivity is dominated by co-existing mechanisms of pinning and nucleation. Furthermore, exchange coupling and dipolar coupling also co-exist in the sample.
基金Project supported by the National Natural Science Foundation of China(Grant No.11947007)the Natural Science Foundation of Guangdong Province,China(Grant No.2019A1515011499)the Department of Education of Guangdong Province,China(Grant No.2019KTSCX087)。
文摘A distant-neighbor quantum-mechanical method is used to study the nonlinear optical wave mixing in graphene nanoflakes(GNFs),including sum-and difference-frequency generation,as well as four-wave mixing.Our analysis shows that molecular-scale GNFs support quantum plasmons in the visible spectrum region,and significant enhancement of nonlinear optical wave mixing is achieved.Specifically,the second-and third-order wave-mixing polarizabilities of GNFs are dramatically enhanced,provided that one(or more) of the input or output frequencies coincide with a quantum plasmon resonance.Moreover,by embedding a cavity into hexagonal GNFs,we show that one can break the structural inversion symmetry and enable otherwise forbidden second-order wave mixing,which is found to be enhanced by the quantum plasmon resonance too.This study reveals that the molecular-sized graphene could be used in the quantum regime for nanoscale nonlinear optical devices and ultrasensitive molecular sensors.
基金Supported by the National Basic Research Program of China under Grant No 2011CB921903the Scientific Research Fund of Zhejiang Provincial Education Department under Grant Nos Y201121234 and LQ12F04001
文摘Adsorption of 1,3,5-triphenylbenzene （TPB） molecules on Cu（100） surface is studied using ultraviolet photo- electron spectroscopy （UPS） and density functional theory （DFT） calculations. Researches on the bottom-up fabrication of graphene nanoflakes （GNFs） with TPB as a precursor on the Cu（100） surface are carried out based on UPS and DFT calculations. Three emission features d, e and f originating from the TPB molecules are located at 3.095, 7.326 and 9.349 eV below the Fermi level, respectively. With the increase of TPB coverage on the Cu（100） substrate, the work function decreases due to the formation of interfacial dipoles and charge （electron） rearrangement at the TPB/Cu（100） interface. Upon the formation of GNFs, five emission characteristic peaks of g, h, i, j and k originating from the GNFs are located at 1.100, 3.529, 6.984, 8.465 and 9.606eV below the Fermi level, respectively. Angle resolved ultraviolet photoelectron spectroscopy （ARUPS） and DFT calculations indicate that TPB molecules adopt a lying-down configuration with their molecular plane nearly parallel to the Cu（100） substrate at the monolayer stage. At the same time, the lying-down configuration for the GNFs on the Cu（100） surface is also unveiled by ARUPS and DFT calculations.
基金financially supported by the National Natural Science Foundation of China(Grants 52072165,52070092,51662031)。
文摘Oxygen vacancy plays vital roles in regulating the electronic and charge distribution of the oxygen deficient materials.Herein,abundant oxygen vacancies are created during assembling the two-dimensional(2D)ultra-thin Bi_(2)MoO_(6) nanoflakes into three dimensional(3D)Bi_(2)MoO_(6) nanospheres,resulting in significantly improved performance for photocatalytical conversion of CO_(2) into liquid hydrocarbons.The increased performance is contributed by two primary sites,namely the abundant oxygen vacancy and the exposed molybdenum(Mo)atom induced by oxygen-migration,as revealed by the theoretical calculation.The oxygen vacancy(Ov)and uncovered Mo atom serving as dual binding sites for trapping CO_(2) molecules render the synchronous fixation-reduction process,resulting in the decline of activation energy for CO_(2) reduction from 2.15 eV on bulk Bi_(2)MoO_(6) to 1.42 eV on Ov-rich Bi_(2)MoO_(6).Such a striking decrease in the activation energy induces the efficient selective generation of liquid hydrocarbons,especially the methanol(C_(2)H_(5) OH)and ethanol(CH_(3) OH).The yields of CH_(3) OH and C_(2)H_(5) OH over the optimal Ov-Bi_(2)MoO_(6) is high up to 106.5 and 10.3μmol g^(-1) respectively,greatly outperforming that on the Bulk-Bi_(2)MoO_(6).
基金financial support from the International Science&Technology Cooperation Program of China(No.2014DFA50860)。
文摘30-50 wt.%graphite nanoflakes(GNFs)/6061Al matrix composites were fabricated via spark plasma sintering(SPS)at 610℃.The effects of the sintering pressure and GNF content on the microstructure and properties of the composites were investigated.The results indicated that interfacial reactions were inhibited during SPS because no Al4C3 was detected.Moreover,the agglomeration of the GNFs increased,and the distribution orientation of the GNFs decreased with increasing the GNF content.The relative density,bending strength,and coefficient of thermal expansion(CTE)of the composites decreased,while the thermal conductivity(TC)in the X−Y direction increased.As the sintering pressure increased,the GNFs deagglomerated and were distributed preferentially in the X−Y direction,which increased the relative density,bending strength and TC,and decreased the CTE of the composites.The 50wt.%GNFs/6061Al matrix composite sintered at 610℃ under 55 MPa demonstrated the best performance,i.e.,bending strength of 72 MPa,TC and CTE(RT−100℃)of 254 W/(m·K)and 8.5×10^(−6)K^(−1)in the X−Y direction,and 55 W/(m·K)and 9.7×10^(−6)K^(−1)in the Z direction,respectively.
文摘Oxygen evolution reaction(OER)is the dominant step for plenty of energy conversion and storage technologies.However,the OER suffers from sluggish kinetics and high overpotential due to its complex 4‐electron/proton transfer mechanism.Thus,developing efficient electrocatalysts is particularly urgent to accelerate OER catalysis but still remains a great challenge.Herein,we have synthesized the novel cobalt molybdate nanoflakes(CoMoO_(4)‐O_(v)‐n@GF)with adjustable oxygen vacancies contents by in situ constructing CoMoO_(4) nanoflakes on graphite felt(GF)and annealing treatment under the reduction atmosphere.The best‐performing CoMoO_(4)‐O_(v)‐2@GF with optimal oxygen vacancies content shows splendid electrocatalytic performance with the low overpotential(296 mV at 10 mA cm^(‒2))and also small Tafel slope(62.4 mV dec^(‒1))in alkaline solution,which are comparable to those of the RuO_(2)@GF.The experimental and the density functional theory calculations results reveal that the construction of optimal oxygen vacancies in CoMoO_(4) can expose more active sites,narrow the band‐gap to increase the electrical conductivity,and modulate the free energy of the OER‐related intermediates to accelerate OER kinetics,thus improving its intrinsic activity.
基金University of Kashan for supporting this work by Grant No.463821/03
文摘We study the spin-resolved transport in a two-terminal graphene nanoflake device with a Rashba spinorbit coupling region in the center of the device. The Green's function method is applied to the system and the spin transmission probability and the spin polarization in x, y, and z directions are calculated. It is found that the components of the spin polarization are antisymmetric functions of Fermi energy, which oscillate and decay to the zero with increasing the energy for all values of the Rashba strength. It is shown that by tuning the Rashba strength via a gate voltage and/or changing the size of the system, it is possible to control the sign and magnitude of the spin polarization. The system represented here is a typical candidate for full electrical spintronic devices based on the carbon materials that are used for spin filtration.
