The catalytic oxidation of HMF involves a cascading reaction with multiple intermediate products,making it crucial to enhance the oriented adsorption capacity of specific functional groups for accelerating the entire ...The catalytic oxidation of HMF involves a cascading reaction with multiple intermediate products,making it crucial to enhance the oriented adsorption capacity of specific functional groups for accelerating the entire process.To achieve the efficient selective oxidation of HMF to FDCA,a series of NiCo_(2)O_(4)catalysts with different morphologies,such as flaky,echinoids,pompon and corolla,were prepared and characterized by XRD,SEM,TEM,BET,XPS,and FTIR.Among the four catalysts,flaky NiCo_(2)O_(4)exhibited the most excellent catalytic activity and stability,with a FDCA yield of 60.1%within 12 h at 80℃without alkali participation.The excellent performance of flaky NiCo_(2)O_(4)catalyst is attributed to the oxygen vacancies and acid sites generated by the exposed(400)facets.The oxygen vacancies and acid sites on the catalyst surface can precisely adsorb-CHO and-CH_(2)-OH of HMF,respectively,and this synergistic effect promotes the efficient production of FDCA.This work is of great significance for fundamentally study the effect of micro-topography or crystal-plane reaction properties on surfaces.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
Two Gd_(2)complexes,namely[Gd_(2)(dbm)_(2)(HL_(1))_(2)(CH_(3)OH)_(2)]·4CH_(3)OH(1)and[Gd_(2)(dbm)_(2)(L_(2))_(2)(CH_(3)OH)_(2)]·2CH_(3)OH(2),where H_(3)L_(1)=(Z)-N'-[4-(diethylamino)-2-hydroxybenzylidene...Two Gd_(2)complexes,namely[Gd_(2)(dbm)_(2)(HL_(1))_(2)(CH_(3)OH)_(2)]·4CH_(3)OH(1)and[Gd_(2)(dbm)_(2)(L_(2))_(2)(CH_(3)OH)_(2)]·2CH_(3)OH(2),where H_(3)L_(1)=(Z)-N'-[4-(diethylamino)-2-hydroxybenzylidene]-2-hydroxyacetohydrazide,H_(2)L_(2)=(E)-N'-(5-bromo-2-hydroxy-3-methoxybenzylidene)nicotinohydrazide,Hdbm=dibenzoylmethane,have been constructed by adopting the solvothermal method.Structural characterization unveils that both complexes 1 and 2 are constituted by two Gd^(3+)ions,two dbm-ions,two CH_(3)OH molecules,and two polydentate Schiff-base ligands(HL_(1)^(2-)or L_(2)^(2-)).In addition,complex 1 contains four free methanol molecules,whereas complex 2 harbors two free methanol molecules.By investigating the interactions between complexes 1 and 2 and four types of bacteria(Bacillus subtilis,Escherichia coli,Staphylococcus aureus,Candida albicans),it was found that both complexes 1 and 2 exhibited potent antibacte-rial activities.The interaction mechanisms between the ligands H_(3)L_(1),H_(2)L_(2),complexes 1 and 2,and calf thymus DNA(CT-DNA)were studied using ultraviolet-visible spectroscopy,fluorescence titration,and cyclic voltammetry.The results demonstrated that both complexes 1 and 2 can intercalate into CT-DNA molecules,thereby inhibiting bacterial proliferation to achieve the antibacterial effects.CCDC:2401116,1;2401117,2.展开更多
As an ultrathin wide-bandgap(WBG)material,CaNb_(2)O_(6)exhibits excellent optical and electrical properties.Particularly,its highly asymmetric crystal structure provides new opportunities for designing novel nanodevic...As an ultrathin wide-bandgap(WBG)material,CaNb_(2)O_(6)exhibits excellent optical and electrical properties.Particularly,its highly asymmetric crystal structure provides new opportunities for designing novel nanodevices with directional functionality.However,due to the significant challenges in applying conventional techniques to nanoscale samples,the in-plane anisotropy of CaNb_(2)O_(6)has still remained unexplored.Here,we leverage the resonant nanoelectromechanical systems(NEMS)platform to successfully quantify both the mechanical and thermal anisotropies in such an ultrathin WBG crystal.Specifically,by measuring the dynamic response in both spectral and spatial domains,we determine the anisotropic Young’s modulus of CaNb_(2)O_(6)as E_(Y(a))=70.42 GPa and EY(b)=116.2 GPa.By further expanding this technique to cryogenic temperatures,we unveil the anisotropy in thermal expansion coefficients as α_((a))=13.4 ppm·K^(-1),α(b)=2.9 ppm·K^(-1).Interestingly,through thermal strain engineering,we successfully modulate the mode sequence and achieve a crossing of(1×2)-(2×1)modes with perfect degeneracy.Our study provides guidelines for future CaNb_(2)O_(6)nanodevices with additional degrees of freedom and new device functions.展开更多
We report the magnetic and transport properties of EuBi_(2) single crystal. EuBi_(2) exhibits complex magnetic behavior at low temperatures. In both the in-plane and out-of-plane directions, three antiferromagnetic(AF...We report the magnetic and transport properties of EuBi_(2) single crystal. EuBi_(2) exhibits complex magnetic behavior at low temperatures. In both the in-plane and out-of-plane directions, three antiferromagnetic(AFM) transitions have been observed at T_(N1)~18.9 K, T_(N2)~7.0 K, and T_(N3)~3.1 K. Among them, the transitions at T_(N2) and T_(N3) represent the canted AFM orders with ferromagnetic components. As the magnetic field increases, the transition at T_(N3) is rapidly suppressed to disappearance. However, the transitions at T_(N1) and T_(N2) persist until high fields and their signatures can also be reflected in the resistivity and specific heat. Above the magnetic transition temperature T_(N1), the resistivity of EuBi_(2) increases linearly with temperature, exhibiting the strange-metal behavior. In the magnetically ordered region below T_(N1), EuBi_(2) exhibits the weak antilocalization(WAL) effect and large magnetoresistance(475% at 1.8 K and 14 T). It is suggested that the magnetic ordering significantly enhances the spin–orbital coupling interaction and induces the WAL effect.展开更多
Birefringent crystals play an irreplaceable role in optical systems by adjusting the polarization state of light in optical devices.This work successfully synthesized a new thiophosphate phase ofβ-Pb_(3)P_(2)S_(8)thr...Birefringent crystals play an irreplaceable role in optical systems by adjusting the polarization state of light in optical devices.This work successfully synthesized a new thiophosphate phase ofβ-Pb_(3)P_(2)S_(8)through the high-temperature solid-state spontaneous crystallization method.Different from the cubicα-Pb_(3)P_(2)S_(8),theβ-Pb_(3)P_(2)S_(8)crystallizes in the orthorhombic Pbcn space group.Notably,β-Pb_(3)P_(2)S_(8)shows a large band gap of 2.37 e V in lead-based chalcogenides,wide infrared transparent window(2.5-15μm),and excellent thermal stability.Importantly,the experimental birefringence shows the largest value of0.26@550 nm in chalcogenides,even larger than the commercialized oxide materials.The Barder charge analysis result indicates that the exceptional birefringence effect is mainly from the Pb^(2+)and S^(2-)in the[Pb S_n]polyhedrons.Meanwhile,the parallelly arranged polyhedral layers could improve the structural anisotropic.Therefore,this work supports a new method for designing chalcogenides with exceptional birefringence effect in the infrared region.展开更多
The transition of cobalt ions located at tetrahedral sites will produce strong absorption in the visible and nearinfrared regions,and is expected to work in a passively Q-switched solid-state laser at the eye-safe wav...The transition of cobalt ions located at tetrahedral sites will produce strong absorption in the visible and nearinfrared regions,and is expected to work in a passively Q-switched solid-state laser at the eye-safe wavelength of 1.5μm.In this study,Co^(2+)ions were introduced into the wide bandgap semiconductor material ZnGa_(2)O_(4),and large-sized and high-quality Co^(2+)-doped ZnGa_(2)O_(4)crystals with a volume of about 20 cm^(3)were grown using the vertical gradient freeze(VGF)method.Crystal structure and optical properties were analyzed using X-ray powder diffraction(XRD),X-ray photoelectron spectroscopy(XPS),and absorption spectroscopy.XRD results show that the Co^(2+)-doped ZnGa_(2)O_(4)crystal has a pure spinel phase without impurity phases and the rocking curve full width at half maximum(FWHM)is only 58 arcsec.The concentration of Co^(2+)in Co^(2+)-doped ZnGa_(2)O_(4)crystals was determined to be 0.2 at.%by the energy dispersive X-ray spectroscopy.The optical band gap of Co^(2+)-doped ZnGa_(2)O_(4)crystals is 4.44 eV.The optical absorption spectrum for Co^(2+)-doped ZnGa_(2)O_(4)reveals a prominent visible absorption band within 550−670 nm and a wide absorption band spanning from 1100 to 1700 nm.This suggests that the Co^(2+)ions have substituted the Zn^(2+)ions,which are typically tetrahedrally coordinated,within the lattice structure of ZnGa_(2)O_(4).The visible region's absorption peak and the near-infrared broad absorption band are ascribed to the^(4)A_(2)(4F)→^(4)T_(1)(4P)and 4A2(4F)→^(4)T_(1)(4F)transitions,respectively.The optimal ground state absorption cross section was determined to be 3.07×10^(−19)cm^(2)in ZnGa_(2)O_(4),a value that is comparatively large within the context of similar materials.This finding suggests that ZnGa_(2)O_(4)is a promising candidate for use in near-infrared passive Q-switched solid-state lasers.展开更多
Photocatalytic ozonation holds promise for advanced water purification,yet its development has been hindered by a limited understanding of ozone activation mechanisms and its related photogenerated electron transfer d...Photocatalytic ozonation holds promise for advanced water purification,yet its development has been hindered by a limited understanding of ozone activation mechanisms and its related photogenerated electron transfer dynamics.Herein,we employed in-situ DRIFTS and Raman spectroscopy to elucidate the distinct adsorption and activation behaviors of ozone(O_(3))on the{001}and{110}crystal facets of Bi_(2)O_(2)CO_(3)(BOC)nanosheets.BOC-{001}demonstrates superior photocatalytic ozonation performance,with 85%phenol mineralization and excellent durability,significantly outperforming the 53%mineralization rate of BOC-{110}.This enhanced activity is attributed to non-dissociative ozone adsorption and favorable adsorption energy over{001}facet,which facilitate the one-electron O_(3) reduction pathway.Furthermore,crystal facet engineering strengthens the built-in electric field,promoting exciton dissociation and the generation of localized charge carriers.The synergistic effects of optimized electron availability and ozone adsorption significantly boost the production of reactive oxygen species.These findings provide a deeper understanding of the critical roles of O_(3) adsorption and electron transfer in radical generation,which could provide some guidance for the strategic development of highly effective photocatalytic ozonation catalysts.展开更多
The phase composition and microstructure of alkaline vanadium slag were characterized using scanning electron microscopy and energy-dispersive X-ray spectroscopy(SEM-EDS)and X-ray diffraction(XRD).A crystallization mo...The phase composition and microstructure of alkaline vanadium slag were characterized using scanning electron microscopy and energy-dispersive X-ray spectroscopy(SEM-EDS)and X-ray diffraction(XRD).A crystallization model of spinel was established to calculate the effects of basicity(the mass ratio of CaO to SiO_(2))and P_(2)O_(5) on crystal growth rates and precipitation patterns.Based on the crystal size distribution(CSD)theory,the size distribution and growth mechanisms of spinel crystals in alkaline vanadium slag at different temperatures were investigated.The results revealed that,at a cooling rate of 5 K/min,the mean grain size of spinel increased from 12.77 to 21.52μm as the temperature decreased from 1748 to 1598 K,with spinel growth being controlled by the interface.At 1548 K,the spinel particle size reached 31.04μm,indicating a supply-controlled growth mechanism as the temperature decreased from 1598 to 1548 K.Increased P_(2)O_(5) content hindered the crystal growth,while an increase in basicity promoted nucleation and growth.Furthermore,MnCr_(2)O_(4) preferentially crystallized and grew in alkaline vanadium slag.展开更多
As an extreme physical condition,high pressure serves as a potent means to substantially modify the interatomic distances and bonding patterns within condensed matter,thereby enabling the macroscopic manipulation of m...As an extreme physical condition,high pressure serves as a potent means to substantially modify the interatomic distances and bonding patterns within condensed matter,thereby enabling the macroscopic manipulation of material properties.We employed the CALYPSO method to predict the stable structures of RbB_(2)C_(4)across the pressure range from 0 GPa to 100 GPa and investigated its physical properties through first-principles calculations.Specially,we found four novel structures,namely,P6_(3)/mcm-,Amm2-,P1-,and I4/mmm-RbB_(2)C_(4).Under pressure conditions,electronic structure calculations reveal that all of them exhibit metallic characteristics.The calculation results of formation enthalpy show that the P6_(3)/mcm structure can be synthesized within the pressure range of 0–40 GPa.Specially,the Amm2,P1,and I4/mmm structures can be synthesized above 4 GPa,6 GPa,10 GPa,respectively.Moreover,the estimated Vickers hardness value of I4/mmm-RbB_(2)C_(4)compound is 47 GPa,suggesting that it is a superhard material.Interestingly,this study uncovers the continuous transformation of the crystal structure of RbB_(2)C_(4)from a layered configuration to folded and tubular forms,ultimately attaining a stabilized cage-like structure under the pressure span of 0–100 GPa.The application of pressure offers a formidable impetus for the advancement and innovation in condensed matter physics,facilitating the exploration of novel states and functions of matter.展开更多
The(010)-oriented substrates of β-Ga_(2)O_(3) are endowed with the maximum thermal conductivity and fastest homoepi-taxial rate,which is the preferred substrate direction for high-power devices.However,the size of(01...The(010)-oriented substrates of β-Ga_(2)O_(3) are endowed with the maximum thermal conductivity and fastest homoepi-taxial rate,which is the preferred substrate direction for high-power devices.However,the size of(010)plane wafer is critically limited by die in the commercial edge-defined film-fed growth(EFG)method.It is difficult to grow the β-Ga_(2)O_(3) crystal with(010)principal face due to the(100)and(001)are cleavage planes.Here,the 2-inch diameter(010)principal-face β-Ga_(2)O_(3) sin-gle crystal is successfully designed and grown by improved EFG method.Unlike previous reported techniques,the single crys-tals are pulled with[001]direction,and in this way the(010)wafers can be obtained from the principal face.In our experi-ments,tree-like defects(TLDs)in(010)principal-face bulk crystals are easy to generate.The relationship between stability of growth interface and origin of TLDs are thoroughly discussed.The TLDs are successfully eliminated by optimizing growth condi-tions.The high crystalline quality of(010)-oriented substrates are comprehensive demonstrated by full width at half maximum(FWHM)with 50.4 arcsec,consistent orientation arrangement of(010)plane,respectively.This work shows that the(010)-ori-ented substrates can be obtained by EFG method,predicting the commercial prospects of large-scale(010)-oriented β-Ga_(2)O_(3) substrates.展开更多
Energy shortages and global warming are driving the focus on the greenhouse gases CH_(4)and CO_(2).The main reason why dry reforming of methane(DRM)has yet to be industrialized is its catalytic tendency to deactivate ...Energy shortages and global warming are driving the focus on the greenhouse gases CH_(4)and CO_(2).The main reason why dry reforming of methane(DRM)has yet to be industrialized is its catalytic tendency to deactivate due to carbon deposition or sintering.Single-atom Ni/CeO_(2)catalysts with suitable metalsupport interactions may provide a new strategy for developing highly active and coking-resistant nickel-based catalysts.In this work,we investigated the properties of the catalytic models of singleatom Ni loaded on CeO_(2)(111),CeO_(2)(110)and CeO_(2)(100),as well as their catalytic DRM performance with the density functional theory method(DFT).The interaction of CeO_(2)with different low-index crystal planes and single-atom Ni can be explained by the anchoring effect of surface O ions on Ni.Adsorption energies,growth patterns of Ni clusters,and migration studies of Ni atoms all indicate that the CeO_(2)(100)surface has the strongest anchoring effect on isolated Ni atoms,followed by the CeO_(2)(110)surface,with the CeO_(2)(111)surface being the weakest,Methane activation studies have shown that the activation ability of Ni_(1)/CeO_(2)(110)for methane strongly depends on the coordination environment of Ni,By contrast,methane activation by Ni on Ni_(1)/CeO_(2)(111)exhibits better activity and stability.Moreover,the Ni—CeO_(2)interaction correlates well with the DRM reaction performance.Interactions that are too strong anchor Ni atoms well but are not optimal for DRM activity.Ni_(1)/CeO_(2)(110)has relatively moderate interactions,promotes the^(*)CH_(4)→^(*)CH process,and has good resistance to carbon deposition.The metalsupport interaction-DRM reactivity(or stability)relationship is vital for the design of"super"highactivity and high-stability DRM catalysts.展开更多
Large-sized （～2 inch, 50.8 mm） γ-LiAlO2 single crystal has been grown by conventional Czochralski （Cz） method, but the crystal has a milky, dendriform center. The samples taken from transparent and milky parts w...Large-sized （～2 inch, 50.8 mm） γ-LiAlO2 single crystal has been grown by conventional Czochralski （Cz） method, but the crystal has a milky, dendriform center. The samples taken from transparent and milky parts were ground and examined by X-ray diffraction. All diffraction peaks could be indexed in γ-LiAlO2. The crystal quality was characterized by X-ray rocking curve. The full-width at half-maximum （FWHM） values are 116.9 and 132.0 arcsec for transparent and milky parts, respectively. The vapor transport equilibrium （VTE） technique was introduced to modify the crystal quality. After 1000℃/48 h, 1100℃/48 h, 1200℃/48 h VTE processes, the FWHM values dropped to 44.2 and 55.2 arcsec for transparent and milky part, respectively. The optical transmission of transparent part was greatly enhanced from 85% to 90%, and transmission of milky part from 75% to 80% in the range of 190~1900 nm at room temperature. When the VTE temperature was raised to 1300℃, the sample cracked and FWHM values of transparent and milky parts were increased to 55.2 and 80.9 arcsec, respectively. By combining Cz technique with VTE technique, large-sized and high quality γ-LiAlO2 crystal can be obtained.展开更多
A promising series of Ho_(y)Nd_(x)Pb_((1-x-y))F_2(x = 0, 0.01, 0.02, 0.03, 0.04;y = 0.02) crystals was grown by the Bridgman method. The influence of the Nd^(3+)ions concentration on mid-infrared(~2.0, ~2.9 and ~3.9 ...A promising series of Ho_(y)Nd_(x)Pb_((1-x-y))F_2(x = 0, 0.01, 0.02, 0.03, 0.04;y = 0.02) crystals was grown by the Bridgman method. The influence of the Nd^(3+)ions concentration on mid-infrared(~2.0, ~2.9 and ~3.9 μm)fluorescence emissions of Ho^(3+)ions in the PbF_(2) crystal excited by 808 nm laser diode was investigated in this work. The energy transfer mechanism between Nd^(3+)ions and Ho~(3+)ions under different concentrations of the Nd^(3+)ions was systematically analyzed. The results show that the Nd^(3+)ions have good sensitization and deactivation effect on the Ho^(3+)ions to stimulate the mid-infrared fluorescence emissions. The experimental analysis proves that the sensitization efficiency of the Nd^(3+)ions is relatively stable at around 93.45% with varying Nd^(3+)-doping concentrations. Concentration dependence studies indicate that the concentration of the Nd^(3+)ions has significant influence on mid-infrared emissions.When the doping concentration of the Nd^(3+)ions is up to 2.0 at%, the intensity of ~2.0, ~2.9 and ~3.9 μm emissions all reach the maximum. The output characteristics of a 3.9 μm laser are simulated, and it is found that with the increase of the Nd^(3+)-doping concentration, the peak power, pulse width, and peak energy all meet the trend of first increasing and then decreasing, and Ho_(0.02)Nd_(0.02)Pb_(0.96)F_(2) crystal displays the best performance. All the results show that the Nd^(3+)/Ho^(3+)co-doped PbF_(2) crystals might act as a useful optical medium for mid-infrared laser applications.展开更多
Ni/TiO_(2) catalyst is widely employed for photo-driven DRM reaction while the influence of crystal structure of TiO_(2) remains unclear.In this work,the rutile/anatase ratio in supports was successfully controlled by...Ni/TiO_(2) catalyst is widely employed for photo-driven DRM reaction while the influence of crystal structure of TiO_(2) remains unclear.In this work,the rutile/anatase ratio in supports was successfully controlled by varying the calcination temperature of anatase-TiO_(2).Structural characterizations revealed that a distinct TiO_(x) coating on the Ni nanoparticles(NPs)was evident for Ni/TiO_(2)-700 catalyst due to strong metal-support interaction.It is observed that the TiOx overlayer gradually disappeared as the ratio of rutile/anatase increased,thereby enhancing the exposure of Ni active sites.The exposed Ni sites enhanced visible light absorption and boosted the dissociation capability of CH4,which led to the much elevated catalytic activity for Ni/TiO_(2)-950 in which rutile dominated.Therefore,the catalytic activity of solar-driven DRM reaction was significantly influenced by the rutile/anatase ratio.Ni/TiO_(2)-950,characterized by a predominant rutile phase,exhibited the highest DRM reactivity,with remarkable H_(2) and CO production rates reaching as high as 87.4 and 220.2 mmol/(g·h),respectively.These rates were approximately 257 and 130 times higher,respectively,compared to those obtained on Ni/TiO_(2)-700 with anatase.This study suggests that the optimization of crystal structure of TiO_(2) support can effectively enhance the performance of photothermal DRM reaction.展开更多
As a promising anode material for magnesium ion rechargeable batteries,magnesium metavanadate(MgV_(2)O_(6))has attracted considerable research interest in recent years.A MgV_(2)O_(6)sample was synthesized via a facile...As a promising anode material for magnesium ion rechargeable batteries,magnesium metavanadate(MgV_(2)O_(6))has attracted considerable research interest in recent years.A MgV_(2)O_(6)sample was synthesized via a facile solid-state reaction by multistep-firing stoichiometric mixtures of MgO and V2O5 powder under an air atmosphere.The solid-state phase transition fromα-MgV_(2)O_(6)toβ-MgV_(2)O_(6)occurred at 841 K and the enthalpy change was 4.37±0.04 kJ/mol.The endothermic effect at 1014 K and the enthalpy change was 26.54±0.26 kJ/mol,which is related to the incongruent melting ofβ-MgV_(2)O_(6).In situ XRD was performed to investigate phase transition of the as-prepared MgV_(2)O_(6)at high temperatures.The cell parameters obtained by Rietveld refinement indicated that it crystallizes in a monoclinic system with the C2/m space group,and the lattice parameters of a=9.280 A°,b=3.501 A°,c=6.731 A°,β=111.76°.The solid-state phase transition fromα-MgV_(2)O_(6)toβ-MgV_(2)O_(6)was further studied by thermal kinetics,indicating that this process is controlled first by a fibril-like mechanism and then by a spherulitic-type mechanism with an increasing heating rate.Additionally,the enthalpy change of MgV_(2)O_(6)at high temperatures was measured utilizing the drop calorimetry,heat capacity was calculated and given as:Cp=208.3+0.03583T-4809000T^(−2)(298-923 K)(J mol^(−1)K^(−1)),the high-temperature heat capacity can be used to calculate Gibbs free energy of MgV_(2)O_(6)at high temperatures.展开更多
基金supported by the Swedish Energy Agency(P47500-1)the National Key R&D Program of China(2020YFA0710200)+2 种基金the National Natural Science Foundation of China(22378401 and U22A20416)the financial support from STINT(CH2019-8287)financial support from the European Union and Swedish Energy Agency(P2020-90066).
文摘The catalytic oxidation of HMF involves a cascading reaction with multiple intermediate products,making it crucial to enhance the oriented adsorption capacity of specific functional groups for accelerating the entire process.To achieve the efficient selective oxidation of HMF to FDCA,a series of NiCo_(2)O_(4)catalysts with different morphologies,such as flaky,echinoids,pompon and corolla,were prepared and characterized by XRD,SEM,TEM,BET,XPS,and FTIR.Among the four catalysts,flaky NiCo_(2)O_(4)exhibited the most excellent catalytic activity and stability,with a FDCA yield of 60.1%within 12 h at 80℃without alkali participation.The excellent performance of flaky NiCo_(2)O_(4)catalyst is attributed to the oxygen vacancies and acid sites generated by the exposed(400)facets.The oxygen vacancies and acid sites on the catalyst surface can precisely adsorb-CHO and-CH_(2)-OH of HMF,respectively,and this synergistic effect promotes the efficient production of FDCA.This work is of great significance for fundamentally study the effect of micro-topography or crystal-plane reaction properties on surfaces.
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.
文摘Two Gd_(2)complexes,namely[Gd_(2)(dbm)_(2)(HL_(1))_(2)(CH_(3)OH)_(2)]·4CH_(3)OH(1)and[Gd_(2)(dbm)_(2)(L_(2))_(2)(CH_(3)OH)_(2)]·2CH_(3)OH(2),where H_(3)L_(1)=(Z)-N'-[4-(diethylamino)-2-hydroxybenzylidene]-2-hydroxyacetohydrazide,H_(2)L_(2)=(E)-N'-(5-bromo-2-hydroxy-3-methoxybenzylidene)nicotinohydrazide,Hdbm=dibenzoylmethane,have been constructed by adopting the solvothermal method.Structural characterization unveils that both complexes 1 and 2 are constituted by two Gd^(3+)ions,two dbm-ions,two CH_(3)OH molecules,and two polydentate Schiff-base ligands(HL_(1)^(2-)or L_(2)^(2-)).In addition,complex 1 contains four free methanol molecules,whereas complex 2 harbors two free methanol molecules.By investigating the interactions between complexes 1 and 2 and four types of bacteria(Bacillus subtilis,Escherichia coli,Staphylococcus aureus,Candida albicans),it was found that both complexes 1 and 2 exhibited potent antibacte-rial activities.The interaction mechanisms between the ligands H_(3)L_(1),H_(2)L_(2),complexes 1 and 2,and calf thymus DNA(CT-DNA)were studied using ultraviolet-visible spectroscopy,fluorescence titration,and cyclic voltammetry.The results demonstrated that both complexes 1 and 2 can intercalate into CT-DNA molecules,thereby inhibiting bacterial proliferation to achieve the antibacterial effects.CCDC:2401116,1;2401117,2.
基金supported by the National Key R&D Program of China(2022YFB3203600)the National Natural Science Foundation of China(Grant Nos.T2325007,62450003,62401104,62404029,U21A20459,62250073,61774029,and U23A20570)+1 种基金the China Postdoctoral Science Foundation(Grant Nos.GZB20230107 and GZB20240109)the Natural Science Foundation of Sichuan Province(Grant Nos.2024NSFSC1430 and 2024NSFSC1408).
文摘As an ultrathin wide-bandgap(WBG)material,CaNb_(2)O_(6)exhibits excellent optical and electrical properties.Particularly,its highly asymmetric crystal structure provides new opportunities for designing novel nanodevices with directional functionality.However,due to the significant challenges in applying conventional techniques to nanoscale samples,the in-plane anisotropy of CaNb_(2)O_(6)has still remained unexplored.Here,we leverage the resonant nanoelectromechanical systems(NEMS)platform to successfully quantify both the mechanical and thermal anisotropies in such an ultrathin WBG crystal.Specifically,by measuring the dynamic response in both spectral and spatial domains,we determine the anisotropic Young’s modulus of CaNb_(2)O_(6)as E_(Y(a))=70.42 GPa and EY(b)=116.2 GPa.By further expanding this technique to cryogenic temperatures,we unveil the anisotropy in thermal expansion coefficients as α_((a))=13.4 ppm·K^(-1),α(b)=2.9 ppm·K^(-1).Interestingly,through thermal strain engineering,we successfully modulate the mode sequence and achieve a crossing of(1×2)-(2×1)modes with perfect degeneracy.Our study provides guidelines for future CaNb_(2)O_(6)nanodevices with additional degrees of freedom and new device functions.
基金Project supported by the National Key Research and Development Program of China (Grant No. 2023YFA1406500)the National Natural Science Foundation of China (Grant Nos. 12474098, 12274388, 12174361, 12404191, 52102333, 12404043, and 12204004)the Natural Science Foundation of Anhui Province (Grant No. 2408085QA024)。
文摘We report the magnetic and transport properties of EuBi_(2) single crystal. EuBi_(2) exhibits complex magnetic behavior at low temperatures. In both the in-plane and out-of-plane directions, three antiferromagnetic(AFM) transitions have been observed at T_(N1)~18.9 K, T_(N2)~7.0 K, and T_(N3)~3.1 K. Among them, the transitions at T_(N2) and T_(N3) represent the canted AFM orders with ferromagnetic components. As the magnetic field increases, the transition at T_(N3) is rapidly suppressed to disappearance. However, the transitions at T_(N1) and T_(N2) persist until high fields and their signatures can also be reflected in the resistivity and specific heat. Above the magnetic transition temperature T_(N1), the resistivity of EuBi_(2) increases linearly with temperature, exhibiting the strange-metal behavior. In the magnetically ordered region below T_(N1), EuBi_(2) exhibits the weak antilocalization(WAL) effect and large magnetoresistance(475% at 1.8 K and 14 T). It is suggested that the magnetic ordering significantly enhances the spin–orbital coupling interaction and induces the WAL effect.
基金supported in part by the National Natural Science Foundation of China(No.52102218)the National Key Research and Development Program of China(No.2020YFA0710303)+2 种基金the Fujian Science&Technology Innovation Laboratory for Op-toelectronic Information of China(No.2021ZZ127)the Minjiang Scholar Professorship(No.GXRC-21004)the Natural Science Foundation of Fujian Province of China(No.2021J01594)。
文摘Birefringent crystals play an irreplaceable role in optical systems by adjusting the polarization state of light in optical devices.This work successfully synthesized a new thiophosphate phase ofβ-Pb_(3)P_(2)S_(8)through the high-temperature solid-state spontaneous crystallization method.Different from the cubicα-Pb_(3)P_(2)S_(8),theβ-Pb_(3)P_(2)S_(8)crystallizes in the orthorhombic Pbcn space group.Notably,β-Pb_(3)P_(2)S_(8)shows a large band gap of 2.37 e V in lead-based chalcogenides,wide infrared transparent window(2.5-15μm),and excellent thermal stability.Importantly,the experimental birefringence shows the largest value of0.26@550 nm in chalcogenides,even larger than the commercialized oxide materials.The Barder charge analysis result indicates that the exceptional birefringence effect is mainly from the Pb^(2+)and S^(2-)in the[Pb S_n]polyhedrons.Meanwhile,the parallelly arranged polyhedral layers could improve the structural anisotropic.Therefore,this work supports a new method for designing chalcogenides with exceptional birefringence effect in the infrared region.
基金the support by the fund of the National Key Research and Development Program of China (Grant No. 2024YFA1208800)National Natural Science Foundation of China (NSFC) (Grant No. U23A20358)+2 种基金Natural Science Foundation of Shandong Province (Grant Nos. ZR2023ZD05 and 2022TSGC2120)the Shenzhen Fundamental Research Program (Grant No. GJHZ20220913142605011)Xiaomi Foundation/Xiaomi Young Talents Program
文摘The transition of cobalt ions located at tetrahedral sites will produce strong absorption in the visible and nearinfrared regions,and is expected to work in a passively Q-switched solid-state laser at the eye-safe wavelength of 1.5μm.In this study,Co^(2+)ions were introduced into the wide bandgap semiconductor material ZnGa_(2)O_(4),and large-sized and high-quality Co^(2+)-doped ZnGa_(2)O_(4)crystals with a volume of about 20 cm^(3)were grown using the vertical gradient freeze(VGF)method.Crystal structure and optical properties were analyzed using X-ray powder diffraction(XRD),X-ray photoelectron spectroscopy(XPS),and absorption spectroscopy.XRD results show that the Co^(2+)-doped ZnGa_(2)O_(4)crystal has a pure spinel phase without impurity phases and the rocking curve full width at half maximum(FWHM)is only 58 arcsec.The concentration of Co^(2+)in Co^(2+)-doped ZnGa_(2)O_(4)crystals was determined to be 0.2 at.%by the energy dispersive X-ray spectroscopy.The optical band gap of Co^(2+)-doped ZnGa_(2)O_(4)crystals is 4.44 eV.The optical absorption spectrum for Co^(2+)-doped ZnGa_(2)O_(4)reveals a prominent visible absorption band within 550−670 nm and a wide absorption band spanning from 1100 to 1700 nm.This suggests that the Co^(2+)ions have substituted the Zn^(2+)ions,which are typically tetrahedrally coordinated,within the lattice structure of ZnGa_(2)O_(4).The visible region's absorption peak and the near-infrared broad absorption band are ascribed to the^(4)A_(2)(4F)→^(4)T_(1)(4P)and 4A2(4F)→^(4)T_(1)(4F)transitions,respectively.The optimal ground state absorption cross section was determined to be 3.07×10^(−19)cm^(2)in ZnGa_(2)O_(4),a value that is comparatively large within the context of similar materials.This finding suggests that ZnGa_(2)O_(4)is a promising candidate for use in near-infrared passive Q-switched solid-state lasers.
文摘Photocatalytic ozonation holds promise for advanced water purification,yet its development has been hindered by a limited understanding of ozone activation mechanisms and its related photogenerated electron transfer dynamics.Herein,we employed in-situ DRIFTS and Raman spectroscopy to elucidate the distinct adsorption and activation behaviors of ozone(O_(3))on the{001}and{110}crystal facets of Bi_(2)O_(2)CO_(3)(BOC)nanosheets.BOC-{001}demonstrates superior photocatalytic ozonation performance,with 85%phenol mineralization and excellent durability,significantly outperforming the 53%mineralization rate of BOC-{110}.This enhanced activity is attributed to non-dissociative ozone adsorption and favorable adsorption energy over{001}facet,which facilitate the one-electron O_(3) reduction pathway.Furthermore,crystal facet engineering strengthens the built-in electric field,promoting exciton dissociation and the generation of localized charge carriers.The synergistic effects of optimized electron availability and ozone adsorption significantly boost the production of reactive oxygen species.These findings provide a deeper understanding of the critical roles of O_(3) adsorption and electron transfer in radical generation,which could provide some guidance for the strategic development of highly effective photocatalytic ozonation catalysts.
基金supported by the National Natural Science Foundation of China(No.51974047)the Natural Science Foundation of Chongqing,China(No.cstc2022ycjh-bgzxm0003)the Large Instrument Foundation of Chongqing University,China(No.202303150239)。
文摘The phase composition and microstructure of alkaline vanadium slag were characterized using scanning electron microscopy and energy-dispersive X-ray spectroscopy(SEM-EDS)and X-ray diffraction(XRD).A crystallization model of spinel was established to calculate the effects of basicity(the mass ratio of CaO to SiO_(2))and P_(2)O_(5) on crystal growth rates and precipitation patterns.Based on the crystal size distribution(CSD)theory,the size distribution and growth mechanisms of spinel crystals in alkaline vanadium slag at different temperatures were investigated.The results revealed that,at a cooling rate of 5 K/min,the mean grain size of spinel increased from 12.77 to 21.52μm as the temperature decreased from 1748 to 1598 K,with spinel growth being controlled by the interface.At 1548 K,the spinel particle size reached 31.04μm,indicating a supply-controlled growth mechanism as the temperature decreased from 1598 to 1548 K.Increased P_(2)O_(5) content hindered the crystal growth,while an increase in basicity promoted nucleation and growth.Furthermore,MnCr_(2)O_(4) preferentially crystallized and grew in alkaline vanadium slag.
基金Project supported by the Jilin Provincial Science and Technology Development Joint Fund Project(Grant No.YDZJ202201ZYTS581)supported by the Scientific and Technological Research Project of Jilin Provincial Education Department(Grant No.JJKH20240077KJ).
文摘As an extreme physical condition,high pressure serves as a potent means to substantially modify the interatomic distances and bonding patterns within condensed matter,thereby enabling the macroscopic manipulation of material properties.We employed the CALYPSO method to predict the stable structures of RbB_(2)C_(4)across the pressure range from 0 GPa to 100 GPa and investigated its physical properties through first-principles calculations.Specially,we found four novel structures,namely,P6_(3)/mcm-,Amm2-,P1-,and I4/mmm-RbB_(2)C_(4).Under pressure conditions,electronic structure calculations reveal that all of them exhibit metallic characteristics.The calculation results of formation enthalpy show that the P6_(3)/mcm structure can be synthesized within the pressure range of 0–40 GPa.Specially,the Amm2,P1,and I4/mmm structures can be synthesized above 4 GPa,6 GPa,10 GPa,respectively.Moreover,the estimated Vickers hardness value of I4/mmm-RbB_(2)C_(4)compound is 47 GPa,suggesting that it is a superhard material.Interestingly,this study uncovers the continuous transformation of the crystal structure of RbB_(2)C_(4)from a layered configuration to folded and tubular forms,ultimately attaining a stabilized cage-like structure under the pressure span of 0–100 GPa.The application of pressure offers a formidable impetus for the advancement and innovation in condensed matter physics,facilitating the exploration of novel states and functions of matter.
基金support by the fund of the National Natural Science Foundation of China(NSFC)(Grant No.U23A20358,51932004)Key-Area Research and Development Program of Guangdong Province(Grant No.2020B010174002)+3 种基金Natural Science Foundation of Shandong Province(Grant No.ZR2023ZD05,2022TSGC2120)the Shenzhen Fundamental Research Program(Grant No.GJHZ20220913142605011)the 111 Project 2.0(Grant No.BP2018013)Laboratory Construction and Management Research Project of Shandong University(Grant No.sy20233203)。
文摘The(010)-oriented substrates of β-Ga_(2)O_(3) are endowed with the maximum thermal conductivity and fastest homoepi-taxial rate,which is the preferred substrate direction for high-power devices.However,the size of(010)plane wafer is critically limited by die in the commercial edge-defined film-fed growth(EFG)method.It is difficult to grow the β-Ga_(2)O_(3) crystal with(010)principal face due to the(100)and(001)are cleavage planes.Here,the 2-inch diameter(010)principal-face β-Ga_(2)O_(3) sin-gle crystal is successfully designed and grown by improved EFG method.Unlike previous reported techniques,the single crys-tals are pulled with[001]direction,and in this way the(010)wafers can be obtained from the principal face.In our experi-ments,tree-like defects(TLDs)in(010)principal-face bulk crystals are easy to generate.The relationship between stability of growth interface and origin of TLDs are thoroughly discussed.The TLDs are successfully eliminated by optimizing growth condi-tions.The high crystalline quality of(010)-oriented substrates are comprehensive demonstrated by full width at half maximum(FWHM)with 50.4 arcsec,consistent orientation arrangement of(010)plane,respectively.This work shows that the(010)-ori-ented substrates can be obtained by EFG method,predicting the commercial prospects of large-scale(010)-oriented β-Ga_(2)O_(3) substrates.
基金Project supported by the Major Science and Technology Projects in Yunnan Province(202302AG050005)。
文摘Energy shortages and global warming are driving the focus on the greenhouse gases CH_(4)and CO_(2).The main reason why dry reforming of methane(DRM)has yet to be industrialized is its catalytic tendency to deactivate due to carbon deposition or sintering.Single-atom Ni/CeO_(2)catalysts with suitable metalsupport interactions may provide a new strategy for developing highly active and coking-resistant nickel-based catalysts.In this work,we investigated the properties of the catalytic models of singleatom Ni loaded on CeO_(2)(111),CeO_(2)(110)and CeO_(2)(100),as well as their catalytic DRM performance with the density functional theory method(DFT).The interaction of CeO_(2)with different low-index crystal planes and single-atom Ni can be explained by the anchoring effect of surface O ions on Ni.Adsorption energies,growth patterns of Ni clusters,and migration studies of Ni atoms all indicate that the CeO_(2)(100)surface has the strongest anchoring effect on isolated Ni atoms,followed by the CeO_(2)(110)surface,with the CeO_(2)(111)surface being the weakest,Methane activation studies have shown that the activation ability of Ni_(1)/CeO_(2)(110)for methane strongly depends on the coordination environment of Ni,By contrast,methane activation by Ni on Ni_(1)/CeO_(2)(111)exhibits better activity and stability.Moreover,the Ni—CeO_(2)interaction correlates well with the DRM reaction performance.Interactions that are too strong anchor Ni atoms well but are not optimal for DRM activity.Ni_(1)/CeO_(2)(110)has relatively moderate interactions,promotes the^(*)CH_(4)→^(*)CH process,and has good resistance to carbon deposition.The metalsupport interaction-DRM reactivity(or stability)relationship is vital for the design of"super"highactivity and high-stability DRM catalysts.
文摘Large-sized （～2 inch, 50.8 mm） γ-LiAlO2 single crystal has been grown by conventional Czochralski （Cz） method, but the crystal has a milky, dendriform center. The samples taken from transparent and milky parts were ground and examined by X-ray diffraction. All diffraction peaks could be indexed in γ-LiAlO2. The crystal quality was characterized by X-ray rocking curve. The full-width at half-maximum （FWHM） values are 116.9 and 132.0 arcsec for transparent and milky parts, respectively. The vapor transport equilibrium （VTE） technique was introduced to modify the crystal quality. After 1000℃/48 h, 1100℃/48 h, 1200℃/48 h VTE processes, the FWHM values dropped to 44.2 and 55.2 arcsec for transparent and milky part, respectively. The optical transmission of transparent part was greatly enhanced from 85% to 90%, and transmission of milky part from 75% to 80% in the range of 190~1900 nm at room temperature. When the VTE temperature was raised to 1300℃, the sample cracked and FWHM values of transparent and milky parts were increased to 55.2 and 80.9 arcsec, respectively. By combining Cz technique with VTE technique, large-sized and high quality γ-LiAlO2 crystal can be obtained.
基金Project supported by the National Natural Science Foundation of China(51972149,51872307,61935010,51702124)Key-Area Research and Development Program of Guangdong Province(2020B090922006)。
文摘A promising series of Ho_(y)Nd_(x)Pb_((1-x-y))F_2(x = 0, 0.01, 0.02, 0.03, 0.04;y = 0.02) crystals was grown by the Bridgman method. The influence of the Nd^(3+)ions concentration on mid-infrared(~2.0, ~2.9 and ~3.9 μm)fluorescence emissions of Ho^(3+)ions in the PbF_(2) crystal excited by 808 nm laser diode was investigated in this work. The energy transfer mechanism between Nd^(3+)ions and Ho~(3+)ions under different concentrations of the Nd^(3+)ions was systematically analyzed. The results show that the Nd^(3+)ions have good sensitization and deactivation effect on the Ho^(3+)ions to stimulate the mid-infrared fluorescence emissions. The experimental analysis proves that the sensitization efficiency of the Nd^(3+)ions is relatively stable at around 93.45% with varying Nd^(3+)-doping concentrations. Concentration dependence studies indicate that the concentration of the Nd^(3+)ions has significant influence on mid-infrared emissions.When the doping concentration of the Nd^(3+)ions is up to 2.0 at%, the intensity of ~2.0, ~2.9 and ~3.9 μm emissions all reach the maximum. The output characteristics of a 3.9 μm laser are simulated, and it is found that with the increase of the Nd^(3+)-doping concentration, the peak power, pulse width, and peak energy all meet the trend of first increasing and then decreasing, and Ho_(0.02)Nd_(0.02)Pb_(0.96)F_(2) crystal displays the best performance. All the results show that the Nd^(3+)/Ho^(3+)co-doped PbF_(2) crystals might act as a useful optical medium for mid-infrared laser applications.
基金The project was supported by the National Key R&D Program of China(2021YFF0500702)Natural Science Foundation of Shanghai(22JC1404200)+3 种基金Program of Shanghai Academic/Technology Research Leader(20XD1404000)Natural Science Foundation of China(U22B20136,22293023)Science and Technology Major Project of Inner Mongolia(2021ZD0042)the Youth Innovation Promotion Association of CAS。
文摘Ni/TiO_(2) catalyst is widely employed for photo-driven DRM reaction while the influence of crystal structure of TiO_(2) remains unclear.In this work,the rutile/anatase ratio in supports was successfully controlled by varying the calcination temperature of anatase-TiO_(2).Structural characterizations revealed that a distinct TiO_(x) coating on the Ni nanoparticles(NPs)was evident for Ni/TiO_(2)-700 catalyst due to strong metal-support interaction.It is observed that the TiOx overlayer gradually disappeared as the ratio of rutile/anatase increased,thereby enhancing the exposure of Ni active sites.The exposed Ni sites enhanced visible light absorption and boosted the dissociation capability of CH4,which led to the much elevated catalytic activity for Ni/TiO_(2)-950 in which rutile dominated.Therefore,the catalytic activity of solar-driven DRM reaction was significantly influenced by the rutile/anatase ratio.Ni/TiO_(2)-950,characterized by a predominant rutile phase,exhibited the highest DRM reactivity,with remarkable H_(2) and CO production rates reaching as high as 87.4 and 220.2 mmol/(g·h),respectively.These rates were approximately 257 and 130 times higher,respectively,compared to those obtained on Ni/TiO_(2)-700 with anatase.This study suggests that the optimization of crystal structure of TiO_(2) support can effectively enhance the performance of photothermal DRM reaction.
基金supported by the National Key R&D Program of China(2018YFC1900500)the Graduate Scientific Research and Innovation Foundation of Chongqing,China(Grant No.CYB20002).
文摘As a promising anode material for magnesium ion rechargeable batteries,magnesium metavanadate(MgV_(2)O_(6))has attracted considerable research interest in recent years.A MgV_(2)O_(6)sample was synthesized via a facile solid-state reaction by multistep-firing stoichiometric mixtures of MgO and V2O5 powder under an air atmosphere.The solid-state phase transition fromα-MgV_(2)O_(6)toβ-MgV_(2)O_(6)occurred at 841 K and the enthalpy change was 4.37±0.04 kJ/mol.The endothermic effect at 1014 K and the enthalpy change was 26.54±0.26 kJ/mol,which is related to the incongruent melting ofβ-MgV_(2)O_(6).In situ XRD was performed to investigate phase transition of the as-prepared MgV_(2)O_(6)at high temperatures.The cell parameters obtained by Rietveld refinement indicated that it crystallizes in a monoclinic system with the C2/m space group,and the lattice parameters of a=9.280 A°,b=3.501 A°,c=6.731 A°,β=111.76°.The solid-state phase transition fromα-MgV_(2)O_(6)toβ-MgV_(2)O_(6)was further studied by thermal kinetics,indicating that this process is controlled first by a fibril-like mechanism and then by a spherulitic-type mechanism with an increasing heating rate.Additionally,the enthalpy change of MgV_(2)O_(6)at high temperatures was measured utilizing the drop calorimetry,heat capacity was calculated and given as:Cp=208.3+0.03583T-4809000T^(−2)(298-923 K)(J mol^(−1)K^(−1)),the high-temperature heat capacity can be used to calculate Gibbs free energy of MgV_(2)O_(6)at high temperatures.
