Europium oxyhydroxide crystals were synthesized by the flux method. The as-grown crystals were transparent and had a plate-like shape with natural flat surfaces. The powder XRD data were refined by assuming a monoclin...Europium oxyhydroxide crystals were synthesized by the flux method. The as-grown crystals were transparent and had a plate-like shape with natural flat surfaces. The powder XRD data were refined by assuming a monoclinic structure of the space group P21/m and lattice parameters of a=0.4346 nm, b=0.3744 nm, c=0.6107 nm, and β=108.62°. The magnetic susceptibility of the EuOOH crystals exhibited typical Van Vleck temperature-independent paramagnetism below 120 K. The calculated susceptibility, based on Van Vleck＇s theory, agreed with the experimental data to some extent, with the coupling constant λ=458±10 K. The experimental results were in close agreement with the results calculated using a modified formula with λ=505±2 K and a constant term C=4.6×10^-4 emu/（mol·Oe）.展开更多
In the present work, the total magnetization in superconducting state is separated into critical state and paramagnetic components in terms of an H（x）-dependent magnetic flux density. Utilizing this model, we reprod...In the present work, the total magnetization in superconducting state is separated into critical state and paramagnetic components in terms of an H（x）-dependent magnetic flux density. Utilizing this model, we reproduce successfully M-H curves measured by Sandu et al. [Phys. Rev. B 74 （2006） 184511] and Sandu et al. [J. Supercond. Incorp. Novel Magn. 17 （2004） 701] for different forms of Jc.展开更多
Zn0.98Cu0.020 powders are prepared by the sol-gel method. A small number of CuO impurity phases are observed by the x-ray diffraction, indicating the solubility of Cu in ZnO is less than 2 at.%. The Zn0.98Cu0.020 powd...Zn0.98Cu0.020 powders are prepared by the sol-gel method. A small number of CuO impurity phases are observed by the x-ray diffraction, indicating the solubility of Cu in ZnO is less than 2 at.%. The Zn0.98Cu0.020 powders exhibit diamagnetism at 300 K and paramagnetism at 5 K. After subtracting the diamagnetic contribution of ZnO bulk and the paramagnetic contribution of defects, Cu ions exhibit weak paramagnetism. By codoping Cu with Co or Mn in ZnO, only paramagnetism is observed at room temperature.展开更多
Ultrasmall near-monodisperse Ba2ErF7 nanocrystals with average crystal size 9.6 nm were synthesized with solvothermal method. The X-ray diffraction （XRD） and transmission electron microscopy （TEM） assays reveal th...Ultrasmall near-monodisperse Ba2ErF7 nanocrystals with average crystal size 9.6 nm were synthesized with solvothermal method. The X-ray diffraction （XRD） and transmission electron microscopy （TEM） assays reveal that the as-synthesized Ba2ErF7 nanocrystals are of the cubic structure with the cell parameter of 5.943 A, instead of the reported orthorhombic and tetragonal structure. Two emission bands originated from 2Hwj4H3/2 → 4F5/2 and 4F9/2 ----＋ 4115,2 of Er3＋ can be observed under a 980 nm laser excitation. The magnetic mass susceptibility of the as-synthesized BazErF7 nanocrystals reaches 4.293 × 10-5 emu g-1 Oe-1.展开更多
Aim To investigate a new method for synthesis of an Immobilized-Metal Affinity Chromatography(IMAC) adsorbent with superparamagnetism(Fe3O4/SiO2-GPTMS-Asp-Co).Method The magnetic microspheres were synthesized in situ ...Aim To investigate a new method for synthesis of an Immobilized-Metal Affinity Chromatography(IMAC) adsorbent with superparamagnetism(Fe3O4/SiO2-GPTMS-Asp-Co).Method The magnetic microspheres were synthesized in situ modification and the transmission electron microscope,field emission scanning electron microscopy,X-ray diffractometer,energy spectrometer and vibrating sample magnetometer were used to characterize the appearance,particle size distribution,phase composition,chemical constituents and magnetic properties of silica magnetic microspheres(MMS).Results The silica MMS prepared by reverse microemulsions exhibit a superior core-shell structure.The size distribution of the microspheres varies from between 100 nm to 200 nm and the main phase of microspheres is amorphous SiO2 and spinel Fe3O4.The microspheres retain superparamagnetism and can be used as biomaterials.Conclusion The result indicates that the IMAC adsorbent we prepared has outstanding advantages in the separation of the natural products proteins from the crude bacterial lysate,such as simple operation,high selectivity and capacity.展开更多
In a route boiling water served as reaction medium, a stoichiometric amount of rare-earth compound and fluoride are put into this system to form a-NaYF4：Yb, Er nuclei. Then prepared sample is heated at elevated tempe...In a route boiling water served as reaction medium, a stoichiometric amount of rare-earth compound and fluoride are put into this system to form a-NaYF4：Yb, Er nuclei. Then prepared sample is heated at elevated temperature to improve the fluorescence intensity, and next a NaGdF4 shell grows on the surface of NaYF4 nuclei. NaYF4：Yb,ErlNaGdF4 core-shell structured upconversion nanoparticles （CSUCNPs） have been successfully synthesized by above route. The use of boiling water decreases the cubic-to-hexagonal phase transition temperature of NaYF4：Yb,Er to 350℃ and increases its upconversion （UC） luminescence intensity. A heterogeneous NaGdF4 epitaxially growing on the surface of Ln^3＋-doped NaYF4 not only improves UC luminescence, but also creates a paramagnetic shell, which can be used as contrast agents in magnetic resonance imaging （MRI）o The solution of CSUCNPs shows bright green UC fluorescence under the excitation at 980 nm in a power density only about 50 mW.cm-2. A broad spectrum with a dominant resonance at g of about 2 is observed by the electron paramagnetic resonance （EPR） spectrum of CSUCNPs. Above properties suggest that the obtained CSUCNPs could be potential candidates for dual-mode optical/magnetic bioapplications.展开更多
Liquid-liquid phase separation(LLPS)of proteins and nucleic acids is a common phenomenon in cells that underlies the formation of membraneless organelles.Although the macroscopic behavior of biomolecular coacervates h...Liquid-liquid phase separation(LLPS)of proteins and nucleic acids is a common phenomenon in cells that underlies the formation of membraneless organelles.Although the macroscopic behavior of biomolecular coacervates has been elucidated by microscopy,the detailed dynamic properties of proteins/peptides during the LLPS process remain poorly characterized.Here,site-directed spin labeling-electron paramagnetic resonance(SDSL-EPR)spectroscopy was employed to characterize the dynamic properties of a minimal model LLPS system consisting of positively charged peptides and RNA.The degree of phase separation,indicated by broadening of the EPR spectrum of the spin-labeled peptide due to slow molecular tumbling,was monitored by EPR.In addition,three distinct populations with varying molecular motion during LLPS,featuring different spectral lineshapes,were identified.These populations included a fast motion component(Ⅰ),a slower motion component(Ⅱ)associated with peptides in the dispersed phase and an immobile component(Ⅲ)observed in the dense phase.With gradual titration of the peptides to RNA,the EPR spectrum gradually shifted,refiecting changes in the populations of the components.Together,SDSL-EPR method not only provides new insights into the dynamic behavior of biomolecules during LLPS,but also offers a sensitive method for biomolecular phase separation processes at the molecular level.展开更多
The development of organic frameworks with radical skeletons is desired.In this study,we report the development of a novel two-dimensional radical halogen-bonded organic framework(XOF).The radical monomer,benzimidazol...The development of organic frameworks with radical skeletons is desired.In this study,we report the development of a novel two-dimensional radical halogen-bonded organic framework(XOF).The radical monomer,benzimidazole triphenylmethyl(BTTM),was synthesized through the coupling of TTM radicals with benzimidazole.Initially,the benzimidazole units were coordinated with Ag^(+)ions to create a[N···Ag···N]^(+)framework.Subsequently,the addition of iodine led to the in situ replacement of Ag^(+)with I^(+)ions,forming[N···I···N]^(+)linkers and resulting in the creation of the XOF structure.The resulting XOF-HBTTM and XOF-BTTM structures demonstrated good-crystallinity,confirmed by PXRD,HR-TEM,SEAD,and SAXS analyses.EPR measurements confirmed the preservation of radical characteristics within the XOF framework.Furthermore,SQUID measurements indicated that XOF-BTTM exhibits spin moments of S=1/2 at 2 K,with a saturated magnetization strength peaking at 4.10 emu/g,a notable enhancement compared to 1.87 emu/g for the BTTM monomer.This improvement in magnetism is attributed to the extended spin density distribution and the presence of[N···I···N]^(+)interactions,as suggested by DFT calculations.Additionally,the radical XOF-BTTM exhibited significantly enhanced electrical conductivity,reaching up to 1.30×10^(-4)S/cm,which is two orders of magnitude higher than that of XOF-HBTTM.This increased conductivity is linked to a reduced HOMO-LUMO gap,higher carrier density,and the incorporation of triphenylmethyl radicals within the framework.This research highlights the potential of benzimidazolyl motifs in constructing functional XOFs and advances our understanding of radical organic frameworks.展开更多
Dialysis plays a crucial role in the purification of nanomaterials but its impact on the structural properties of carbon nanomaterials was never investigated.Herein,a carbon-based nanomaterial generated electrochemica...Dialysis plays a crucial role in the purification of nanomaterials but its impact on the structural properties of carbon nanomaterials was never investigated.Herein,a carbon-based nanomaterial generated electrochemically in potassium phosphate buffer,was characterized before and after dialysis against pure water.It is shown that dialysis affects the size of the carbon domains,structural organization,surface functionalization,oxidation degree of carbon,and grade of amorphicity.Accordingly,dialysis drives the nanomaterial organization from discrete roundish carbon domains,with sizes ranging from 70 to 160 nm,towards linear stacking structures of small nanoparticles(<15 nm).In parallel,alcohol and ether(epoxide)surface groups evolve into more oxidized carbon groups(e.g.,ketone and ester groups).Investigation of the as-prepared nanomaterial by electron paramagnetic resonance(EPR)revealed a resonance signal consistent with carbon-oxygen centred radicals.Additionally,this study brings to light the selective affinity of the carbon nanomaterial under study to capture Na^(+)ions,a property greatly enhanced by the dialysis process,and its high ability to trap oxygen,particularly before dialysis.These findings open new perspectives for the application of carbon-based nanomaterials and raise awareness of the importance of structural changes that can occur during the purification of carbon-based nanomaterials.展开更多
This work revisits the temperature dependence of^(1)H paramagnetic shift in nickelocene as a potential nuclear magnetic resonance(NMR)thermometer under fast magic angle spinning(MAS)rate.Surprisingly,an abnormal tempe...This work revisits the temperature dependence of^(1)H paramagnetic shift in nickelocene as a potential nuclear magnetic resonance(NMR)thermometer under fast magic angle spinning(MAS)rate.Surprisingly,an abnormal temperature dependence of^(1)H paramagnetic shift has been observed.In addition to a 1/T dependence term,a 1/T^(2)dependence term must be included to correctly describe the curvature behavior of the δ^(1)H-T correlation under fast MAS rate.展开更多
Bacterial small laccases(SLAC) are promising industrial biocatalysts due to their ability to oxidize a broad range of substrates with exceptional thermostability and tolerance for alkaline p H. Electron transfer betwe...Bacterial small laccases(SLAC) are promising industrial biocatalysts due to their ability to oxidize a broad range of substrates with exceptional thermostability and tolerance for alkaline p H. Electron transfer between substrate, copper centers, and O2is one of the key steps in the catalytic turnover of SLAC. However, limited research has been conducted on the electron transfer pathway of SLAC and SLAC-catalyzed reactions, hindering further engineering of SLAC to produce tunable biocatalysts for novel applications. Herein, the combinational use of electron paramagnetic resonance(EPR) and ultraviolet-visible(UV-vis) spectroscopic methods coupled with redox titration were employed to monitor the electron transfer processes and obtain further insights into the electron transfer pathway in SLAC. The reduction potentials for type 1 copper(T1Cu), type 2 copper(T2Cu) and type 3copper(T3Cu) were determined to be 367 ± 2 mV, 378 ± 5 m V and 403 ± 2 mV,respectively. Moreover, the reduction potential of a selected substrate of SLAC, hydroquinone(HQ), was determined to be 288 mV using cyclic voltammetry(CV). In this way, an electron transfer pathway was identified based on the reduction potentials. Specifically,electrons are transferred from HQ to T1Cu, then to T2Cu and T3Cu, and finally to O2.Furthermore, superhyperfine splitting observed via EPR during redox titration indicated a modification in the covalency of T2Cu upon electron uptake, suggesting a conformational alteration in the protein environment surrounding the copper sites, which could potentially influence the reduction potential of the copper sites during catalytic processes. The results presented here not only provide a comprehensive method for analyzing the electron transfer pathway in metalloenzymes through reduction potential measurements, but also offer valuable insights for further engineering and directed evolution studies of SLAC in the aim for biotechnological and industrial applications.展开更多
The effects of Fe2O3 content on the microstructure and mechanical properties of the CaO-Al2O3-SiO2 system were investigated by differential thermal analysis（DTA）, X-ray diffraction（XRD）, scanning electron microsc...The effects of Fe2O3 content on the microstructure and mechanical properties of the CaO-Al2O3-SiO2 system were investigated by differential thermal analysis（DTA）, X-ray diffraction（XRD）, scanning electron microscopy（SEM）, electron spin resonance（ESR）, and Mssbauer spectroscopy. The results show that the addition of Fe2O3 does not affect the main crystalline phase in the prepared glasses, but it reduces the crystallisation peak temperature, increases the crystallisation activation energy, and reduces the crystal granularity. The ESR results indicate that Fe2O3 can promote crystallization, as it leads to the phase separation of the CaO-Al2O3-SiO2 system due to axial distortion. Moreover, Fe2O3 alters the network structure of the CaO-Al2O3-SiO2 system, allowing Fe3＋ to enter octahedral sites that exhibit higher symmetry than tetrahedral sites. All of these factors are favourable to increasing the bending strength. The Mssbauer results reveal that there are two types of coordination for both Fe3＋ and Fe2＋ and the bending strength of the CaO-Al2O3-SiO2 system increases with the amount of six-coordinate Fe3＋. The increasing interaction between Fe3＋ and Fe2＋ can also enhance the bending strength of the CaO-Al2O3-SiO2 system. The microhardness of the CaO-Al2O3-SiO2 system was determined to be HV 896.9 and the bending strength to be 217 MPa under the heat treatment conditions of nucleation temperature of 700 °C and nucleation time of 2 h, crystallization temperature of 910 °C and crystallization time of 3 h.展开更多
Zn1-xMnxO nanorods and Zn1-2xMnxLixO nano-particles were synthesized by solvothermal method at 160℃. X-ray diffraction and Raman results showed that Mn ions were well incorporated into the ZnO matrix. No magnetic hys...Zn1-xMnxO nanorods and Zn1-2xMnxLixO nano-particles were synthesized by solvothermal method at 160℃. X-ray diffraction and Raman results showed that Mn ions were well incorporated into the ZnO matrix. No magnetic hysteresis were found in the magnetization curves. The hyperfine structures were observed in electron spin resonance spectra, indicating no ferromagnetic interaction between substituted Mn ions. The co-doping of Li can only change the morphology not the magnetic properties.展开更多
In this study,high entropy metallic glasses(HEMGs)were developed through a combination of concepts for designing metallic glasses(main element+transition metal+metalloid element)and high-entropy alloys(more than five ...In this study,high entropy metallic glasses(HEMGs)were developed through a combination of concepts for designing metallic glasses(main element+transition metal+metalloid element)and high-entropy alloys(more than five elements,each element having an atomic concentration between 5 at.%and 35 at.%).The developed metallic glass alloys are composed of Co-Fe-Ni main elements,transition metals(Cr,Mo)and metalloid elements(C,B).Moreover,the present work reports the thermal,mechanical and magnetic properties of(CoFeNi)(50)(CrMo)(50-x)(CB)x alloys with x=20,25,30.The developed as-spun HEMGs exhibit typical paramagnetic properties even for a high amount of ferromagnetic elements(Co,Fe,and Ni)and have high elastic modulus(103–160 GPa)and hardness(14–27 GPa),thus possessing mechanical properties similar to well-known Co-based metallic glasses(Co-Cr-Mo-C-B system).In addition,some of the bulk samples prepared with a diameter of 2 mm form bulk metallic glasses with a high compressive strength around 3.5 GPa.The mechanisms determining the stability of the supercooled liquid,as well as the paramagnetic and mechanical properties for the developed non-equiatomic HEMGs,are discussed.展开更多
At low temperature and under weak magnetic field, non-interacting Fermi gases reveal both Pauli paramagnetism and Landau diamagnetism, and the magnitude of the diamagnetic susceptibility is 1/3 of that of the paramagn...At low temperature and under weak magnetic field, non-interacting Fermi gases reveal both Pauli paramagnetism and Landau diamagnetism, and the magnitude of the diamagnetic susceptibility is 1/3 of that of the paramagnetic one. When the temperature is finite and the magnetic field is also finite, we demonstrate that the paramagnetism and diamagnetism start to deviate from the ratio 1/3. For understanding the magnetic properties of an ideal Fermi gas at quite low temperature and under quite weak magnetic field, we work out explicitly the third-order magnetic susceptibility in three cases, from intrinsic spin, orbital motion and in total. An interesting property is in third-order magnetic susceptibilities: when viewing individually, they are both diamagnetic, but in total it is paramagnetic.展开更多
A simple and rapid strategy to construct laccase biosensor for determination of catechol was investigated. Magnetic multiwalled carbon nanotubes (MMCNT) which possess excellent capability of electron transfer were pre...A simple and rapid strategy to construct laccase biosensor for determination of catechol was investigated. Magnetic multiwalled carbon nanotubes (MMCNT) which possess excellent capability of electron transfer were prepared by chemical coprecipitation method. Scanning electron microscope (SEM) and vibrating sample magnetometer (VSM) were used to identify its surfacetopography and magnetization, respectively. Laccase was immobilized on the MMCNT modified magnetic carbon paste electrode by the aid of chitosan/silica (CS) hybrid membrane. Using current-time detection method, the biosensor shows a linear response related to the concentration of catechol in the range from 10-7 to 0.165×10-3 mol/L. The corresponding detection limit is 3.34×10-8 mol/L based on signal-to-noise ratios (S/N) ≥3 under the optimized conditions. In addition, its response current retains 90% of the original after being stored for 45 d. The results indicate that this proposed strategy can be expected to develop other enzyme-based biosensors.展开更多
The finite-temperature Pauli paramagnetic susceptibility of a three-dimensional ideal anyon gas obeying Haldane fractional exclusion statistics is studied analytically.Different from the result of an ideal Fermi gas,t...The finite-temperature Pauli paramagnetic susceptibility of a three-dimensional ideal anyon gas obeying Haldane fractional exclusion statistics is studied analytically.Different from the result of an ideal Fermi gas,the susceptibility of an ideal anyon gas depends on a statistical factor g in Haldane statistics model.The low-temperature and high-temperature behaviors of the susceptibility are investigated in detail.The Pauli paramagnetic susceptibility of the two-dimensional ideal anyons is also derived.It is found that the reciprocal of the susceptibility has the similar factorizable property which is exhibited in some thermodynamic quantities in two dimensions.展开更多
CdGd2 （WO4）4 -δ single crystal was grown using the Czochralski＇s method. The crystal structure was tetragonal seheelite with lattice parameters a = b = 0.5203 nm and c = 1. 1359 nm. There were vacancies of （WO4）...CdGd2 （WO4）4 -δ single crystal was grown using the Czochralski＇s method. The crystal structure was tetragonal seheelite with lattice parameters a = b = 0.5203 nm and c = 1. 1359 nm. There were vacancies of （WO4）^2- , therefore, there were some Gd^2＋ ions. Langevin paramagnetism and anisotropy were observed from the δ-T curves at room temperature. The susceptibility X//was 3.5018×10^-3, and X⊥ was 3.4403× 10^-2. The anisotropy was also observed in the electron spin resonance （ESR） experiments. The anisotropic Land6 factors were g//= 2. 1333 and g~ = 2. 8411. The direction of easy magnetization was in the α-b plane. Anisotropic paramagnetic Curie constants C//and C⊥ were not only related to macroscopic a that was observed through the experiment, but were also related to J⊥ and J//, which were the microscopic quantum numbers of the Gd^2＋ and Gd^3｜ ions. Based on the detailed analyses, the proportion of 36.8% of Gd^3＋ ions to 63.2% of Gd^2＋ ions in the Gd ions of the CdGd2（WO4）4-δ crystal was calculated, and δ was 0.638 in the single crystal.展开更多
The present study involves co-precipitation method to grow un-doped and Zr-doped bismuth iron oxide with x_（Zr）=0.10–0.30. The molar solutions of ferric chloride（FeCl_3）, zirconyle chloride（ZrOCl_2）, and bismut...The present study involves co-precipitation method to grow un-doped and Zr-doped bismuth iron oxide with x_（Zr）=0.10–0.30. The molar solutions of ferric chloride（FeCl_3）, zirconyle chloride（ZrOCl_2）, and bismuth chloride（BiCl_3） are prepared in distilled water, and are allowed to react with sodium hydroxide（Na OH）. The synthesized powders are then converted into pellets, which are sintered at 500℃ for two hours in a muffle furnace. X-ray diffraction（XRD） shows multi-phase formation in un-doped and Zr doped samples. Scanning electron microscope（SEM） depicts layered structure at low Zr concentration x_（Zr）= 0.10, while uniform surface with smaller grains and voids is observed at x_（Zr）= 0.20, but at x_（Zr）= 0.30, cracks and voids become prominent. The ferromagnetic nature of the un-doped sample is observed by vibrating sample magnetometer（VSM）, while paramagnetic behavior appears due to Zr doping. The ferromagnetism in un-doped sample is lost by Zr doping, which is due to the formation of additional Fe–O–Zr bonds that induce paramagnetic behavior.展开更多
By using inorganic Fe3O4 nanoparticles of different content as nucleation sites, PAn-Fe3O4 nanorods were successfully synthesized through a simple, conventional, and inexpensive one-step in-situ polymerization method....By using inorganic Fe3O4 nanoparticles of different content as nucleation sites, PAn-Fe3O4 nanorods were successfully synthesized through a simple, conventional, and inexpensive one-step in-situ polymerization method. The TEM images revealed the size and morphology of the resultant nanocomposite. The EDS pattern confirmed the existence of Fe3O4 in the composite. The FT-IR spectral analysis confirmed the formation of PAn encapsulated Fe3O4 nanocomposite. With the content of Fe3O4 increasing, the conductivity of the nanocomposites gradually decreases, meanwhile, the saturation magnetization increases and reveals a super paramagnetic behavior. With controllable electrical, magnetic, and electromagnetic properties, the well-prepared nanocomposites may have the potential applications in chemical sensors, catalysis, microwave absorbing, and electro-magneto-rheological fluids, etc.展开更多
基金Project supported by Japan Society for the Promotion of Science(JSPS)KAKENHI Grants(21560696,24560827)
文摘Europium oxyhydroxide crystals were synthesized by the flux method. The as-grown crystals were transparent and had a plate-like shape with natural flat surfaces. The powder XRD data were refined by assuming a monoclinic structure of the space group P21/m and lattice parameters of a=0.4346 nm, b=0.3744 nm, c=0.6107 nm, and β=108.62°. The magnetic susceptibility of the EuOOH crystals exhibited typical Van Vleck temperature-independent paramagnetism below 120 K. The calculated susceptibility, based on Van Vleck＇s theory, agreed with the experimental data to some extent, with the coupling constant λ=458±10 K. The experimental results were in close agreement with the results calculated using a modified formula with λ=505±2 K and a constant term C=4.6×10^-4 emu/（mol·Oe）.
文摘In the present work, the total magnetization in superconducting state is separated into critical state and paramagnetic components in terms of an H（x）-dependent magnetic flux density. Utilizing this model, we reproduce successfully M-H curves measured by Sandu et al. [Phys. Rev. B 74 （2006） 184511] and Sandu et al. [J. Supercond. Incorp. Novel Magn. 17 （2004） 701] for different forms of Jc.
基金supported by the National Natural Science Foundation of China (Grant No. 50802041)the National Key Projects for Basic Research of China (Grant No. 2010CB923404)Southeast University
文摘Zn0.98Cu0.020 powders are prepared by the sol-gel method. A small number of CuO impurity phases are observed by the x-ray diffraction, indicating the solubility of Cu in ZnO is less than 2 at.%. The Zn0.98Cu0.020 powders exhibit diamagnetism at 300 K and paramagnetism at 5 K. After subtracting the diamagnetic contribution of ZnO bulk and the paramagnetic contribution of defects, Cu ions exhibit weak paramagnetism. By codoping Cu with Co or Mn in ZnO, only paramagnetism is observed at room temperature.
文摘Ultrasmall near-monodisperse Ba2ErF7 nanocrystals with average crystal size 9.6 nm were synthesized with solvothermal method. The X-ray diffraction （XRD） and transmission electron microscopy （TEM） assays reveal that the as-synthesized Ba2ErF7 nanocrystals are of the cubic structure with the cell parameter of 5.943 A, instead of the reported orthorhombic and tetragonal structure. Two emission bands originated from 2Hwj4H3/2 → 4F5/2 and 4F9/2 ----＋ 4115,2 of Er3＋ can be observed under a 980 nm laser excitation. The magnetic mass susceptibility of the as-synthesized BazErF7 nanocrystals reaches 4.293 × 10-5 emu g-1 Oe-1.
文摘Aim To investigate a new method for synthesis of an Immobilized-Metal Affinity Chromatography(IMAC) adsorbent with superparamagnetism(Fe3O4/SiO2-GPTMS-Asp-Co).Method The magnetic microspheres were synthesized in situ modification and the transmission electron microscope,field emission scanning electron microscopy,X-ray diffractometer,energy spectrometer and vibrating sample magnetometer were used to characterize the appearance,particle size distribution,phase composition,chemical constituents and magnetic properties of silica magnetic microspheres(MMS).Results The silica MMS prepared by reverse microemulsions exhibit a superior core-shell structure.The size distribution of the microspheres varies from between 100 nm to 200 nm and the main phase of microspheres is amorphous SiO2 and spinel Fe3O4.The microspheres retain superparamagnetism and can be used as biomaterials.Conclusion The result indicates that the IMAC adsorbent we prepared has outstanding advantages in the separation of the natural products proteins from the crude bacterial lysate,such as simple operation,high selectivity and capacity.
基金Acknowledgements Authors would like to acknowledge the National Natural Science Foundation of China （NSFC, Grant No. 51361009）, the International Joint Project of Hainan Province （Grant No. KJHZ2014-19）, the Postgraduate Innovative Project of Hainan Province in 2015 （Grant No. Hys2015-24） and the Postgraduate Practice ＆ Innovation Projects of Hainan University in 2015 for financial support. The Instrumental Analysis Center of Hainan University is also acknowledged here.
文摘In a route boiling water served as reaction medium, a stoichiometric amount of rare-earth compound and fluoride are put into this system to form a-NaYF4：Yb, Er nuclei. Then prepared sample is heated at elevated temperature to improve the fluorescence intensity, and next a NaGdF4 shell grows on the surface of NaYF4 nuclei. NaYF4：Yb,ErlNaGdF4 core-shell structured upconversion nanoparticles （CSUCNPs） have been successfully synthesized by above route. The use of boiling water decreases the cubic-to-hexagonal phase transition temperature of NaYF4：Yb,Er to 350℃ and increases its upconversion （UC） luminescence intensity. A heterogeneous NaGdF4 epitaxially growing on the surface of Ln^3＋-doped NaYF4 not only improves UC luminescence, but also creates a paramagnetic shell, which can be used as contrast agents in magnetic resonance imaging （MRI）o The solution of CSUCNPs shows bright green UC fluorescence under the excitation at 980 nm in a power density only about 50 mW.cm-2. A broad spectrum with a dominant resonance at g of about 2 is observed by the electron paramagnetic resonance （EPR） spectrum of CSUCNPs. Above properties suggest that the obtained CSUCNPs could be potential candidates for dual-mode optical/magnetic bioapplications.
基金supported by the National Natural Science Foundation of China(No.21927814)the National Key Research and Development Program of China(Nos.2019YFA0405600,2019YFA0706900,2021YFA1200104,2022YFC3400500)+2 种基金the Strategic Priority Research Program of Chinese Academy of Sciences(Nos.XDB0540200,XDB37040201)Plans for Major Provincial Science&Technology Projects(No.202303a07020004)the Youth Innovation Promotion Association,CAS(No.2022455)。
文摘Liquid-liquid phase separation(LLPS)of proteins and nucleic acids is a common phenomenon in cells that underlies the formation of membraneless organelles.Although the macroscopic behavior of biomolecular coacervates has been elucidated by microscopy,the detailed dynamic properties of proteins/peptides during the LLPS process remain poorly characterized.Here,site-directed spin labeling-electron paramagnetic resonance(SDSL-EPR)spectroscopy was employed to characterize the dynamic properties of a minimal model LLPS system consisting of positively charged peptides and RNA.The degree of phase separation,indicated by broadening of the EPR spectrum of the spin-labeled peptide due to slow molecular tumbling,was monitored by EPR.In addition,three distinct populations with varying molecular motion during LLPS,featuring different spectral lineshapes,were identified.These populations included a fast motion component(Ⅰ),a slower motion component(Ⅱ)associated with peptides in the dispersed phase and an immobile component(Ⅲ)observed in the dense phase.With gradual titration of the peptides to RNA,the EPR spectrum gradually shifted,refiecting changes in the populations of the components.Together,SDSL-EPR method not only provides new insights into the dynamic behavior of biomolecules during LLPS,but also offers a sensitive method for biomolecular phase separation processes at the molecular level.
基金supported by National Natural Science Foundation of China(Nos.22371218,21702153,52270070 and21801194)Natural Science Foundation of Zhejiang Province(No.LR22B020001)+1 种基金Wuhan Science and Technology Bureau(No.whkxjsj009)the support of the Core Facility of Wuhan University and the Large-scale Instrument and Equipment Sharing Foundation of Wuhan University。
文摘The development of organic frameworks with radical skeletons is desired.In this study,we report the development of a novel two-dimensional radical halogen-bonded organic framework(XOF).The radical monomer,benzimidazole triphenylmethyl(BTTM),was synthesized through the coupling of TTM radicals with benzimidazole.Initially,the benzimidazole units were coordinated with Ag^(+)ions to create a[N···Ag···N]^(+)framework.Subsequently,the addition of iodine led to the in situ replacement of Ag^(+)with I^(+)ions,forming[N···I···N]^(+)linkers and resulting in the creation of the XOF structure.The resulting XOF-HBTTM and XOF-BTTM structures demonstrated good-crystallinity,confirmed by PXRD,HR-TEM,SEAD,and SAXS analyses.EPR measurements confirmed the preservation of radical characteristics within the XOF framework.Furthermore,SQUID measurements indicated that XOF-BTTM exhibits spin moments of S=1/2 at 2 K,with a saturated magnetization strength peaking at 4.10 emu/g,a notable enhancement compared to 1.87 emu/g for the BTTM monomer.This improvement in magnetism is attributed to the extended spin density distribution and the presence of[N···I···N]^(+)interactions,as suggested by DFT calculations.Additionally,the radical XOF-BTTM exhibited significantly enhanced electrical conductivity,reaching up to 1.30×10^(-4)S/cm,which is two orders of magnitude higher than that of XOF-HBTTM.This increased conductivity is linked to a reduced HOMO-LUMO gap,higher carrier density,and the incorporation of triphenylmethyl radicals within the framework.This research highlights the potential of benzimidazolyl motifs in constructing functional XOFs and advances our understanding of radical organic frameworks.
基金FCT(Portugal's Foundation for Science and Technology)for financial support through the CQ-VR(UIDB/00616/2020,UIDP/00616/2020),CQE/Institute of Molecular Sciences(UIBD/00100/2020,UIPD/00100/2020 and LA/P/0056/2020),Institute for Bioengineering and Biosciences-iBB/Associate Laboratory Institute for Health and Bioeconomy-i4HB(UIDB/04565/2020,UIDP/04565/2020,and LA/P/0140/2020)FCT,MCTES,ESF,and EU through the individual research Ph.D.for the Ph.D.scholarship(SFRH/BD/138425/2018)+1 种基金FCT for funding through the Scientific Employment Stimulus—Institutional Call(Ref.CEECINST/00136/2021)the EPSRC funded National Research Facility(EP/W014521/1)。
文摘Dialysis plays a crucial role in the purification of nanomaterials but its impact on the structural properties of carbon nanomaterials was never investigated.Herein,a carbon-based nanomaterial generated electrochemically in potassium phosphate buffer,was characterized before and after dialysis against pure water.It is shown that dialysis affects the size of the carbon domains,structural organization,surface functionalization,oxidation degree of carbon,and grade of amorphicity.Accordingly,dialysis drives the nanomaterial organization from discrete roundish carbon domains,with sizes ranging from 70 to 160 nm,towards linear stacking structures of small nanoparticles(<15 nm).In parallel,alcohol and ether(epoxide)surface groups evolve into more oxidized carbon groups(e.g.,ketone and ester groups).Investigation of the as-prepared nanomaterial by electron paramagnetic resonance(EPR)revealed a resonance signal consistent with carbon-oxygen centred radicals.Additionally,this study brings to light the selective affinity of the carbon nanomaterial under study to capture Na^(+)ions,a property greatly enhanced by the dialysis process,and its high ability to trap oxygen,particularly before dialysis.These findings open new perspectives for the application of carbon-based nanomaterials and raise awareness of the importance of structural changes that can occur during the purification of carbon-based nanomaterials.
基金supported by grants from the National Natural Science Foundation of China(Nos.22172049,22272055).
文摘This work revisits the temperature dependence of^(1)H paramagnetic shift in nickelocene as a potential nuclear magnetic resonance(NMR)thermometer under fast magic angle spinning(MAS)rate.Surprisingly,an abnormal temperature dependence of^(1)H paramagnetic shift has been observed.In addition to a 1/T dependence term,a 1/T^(2)dependence term must be included to correctly describe the curvature behavior of the δ^(1)H-T correlation under fast MAS rate.
基金supported by the National Natural Science Foundation of China (21825703, 21927814)the National Key R&D Program of China (2019YFA0405600, 2019YFA0706900, 2021YFA1200104, 2022YFC3400500)+3 种基金the Strategic Priority Research Program of Chinese Academy of Sciences (XDB0540200, XDB37040201)Plans for Major Provincial Science&Technology Projects (202303a07020004)Basic Research Program Based on Major Scientific Infrastructures,CAS (JZHKYPT-2021-05)the Youth Innovation Promotion Association,CAS (2022455)
文摘Bacterial small laccases(SLAC) are promising industrial biocatalysts due to their ability to oxidize a broad range of substrates with exceptional thermostability and tolerance for alkaline p H. Electron transfer between substrate, copper centers, and O2is one of the key steps in the catalytic turnover of SLAC. However, limited research has been conducted on the electron transfer pathway of SLAC and SLAC-catalyzed reactions, hindering further engineering of SLAC to produce tunable biocatalysts for novel applications. Herein, the combinational use of electron paramagnetic resonance(EPR) and ultraviolet-visible(UV-vis) spectroscopic methods coupled with redox titration were employed to monitor the electron transfer processes and obtain further insights into the electron transfer pathway in SLAC. The reduction potentials for type 1 copper(T1Cu), type 2 copper(T2Cu) and type 3copper(T3Cu) were determined to be 367 ± 2 mV, 378 ± 5 m V and 403 ± 2 mV,respectively. Moreover, the reduction potential of a selected substrate of SLAC, hydroquinone(HQ), was determined to be 288 mV using cyclic voltammetry(CV). In this way, an electron transfer pathway was identified based on the reduction potentials. Specifically,electrons are transferred from HQ to T1Cu, then to T2Cu and T3Cu, and finally to O2.Furthermore, superhyperfine splitting observed via EPR during redox titration indicated a modification in the covalency of T2Cu upon electron uptake, suggesting a conformational alteration in the protein environment surrounding the copper sites, which could potentially influence the reduction potential of the copper sites during catalytic processes. The results presented here not only provide a comprehensive method for analyzing the electron transfer pathway in metalloenzymes through reduction potential measurements, but also offer valuable insights for further engineering and directed evolution studies of SLAC in the aim for biotechnological and industrial applications.
基金Project(50974090)supported by the National Natural Science Foundation of ChinaProjects(JCYJ20140418182819155,JCYJ20130329113849606)supported by the Shenzhen Dedicated Funding of Strategic Emerging Industry Development Program,China
文摘The effects of Fe2O3 content on the microstructure and mechanical properties of the CaO-Al2O3-SiO2 system were investigated by differential thermal analysis（DTA）, X-ray diffraction（XRD）, scanning electron microscopy（SEM）, electron spin resonance（ESR）, and Mssbauer spectroscopy. The results show that the addition of Fe2O3 does not affect the main crystalline phase in the prepared glasses, but it reduces the crystallisation peak temperature, increases the crystallisation activation energy, and reduces the crystal granularity. The ESR results indicate that Fe2O3 can promote crystallization, as it leads to the phase separation of the CaO-Al2O3-SiO2 system due to axial distortion. Moreover, Fe2O3 alters the network structure of the CaO-Al2O3-SiO2 system, allowing Fe3＋ to enter octahedral sites that exhibit higher symmetry than tetrahedral sites. All of these factors are favourable to increasing the bending strength. The Mssbauer results reveal that there are two types of coordination for both Fe3＋ and Fe2＋ and the bending strength of the CaO-Al2O3-SiO2 system increases with the amount of six-coordinate Fe3＋. The increasing interaction between Fe3＋ and Fe2＋ can also enhance the bending strength of the CaO-Al2O3-SiO2 system. The microhardness of the CaO-Al2O3-SiO2 system was determined to be HV 896.9 and the bending strength to be 217 MPa under the heat treatment conditions of nucleation temperature of 700 °C and nucleation time of 2 h, crystallization temperature of 910 °C and crystallization time of 3 h.
基金This work was supported by the National Natural Science Foundation of China （No.50702060）.
文摘Zn1-xMnxO nanorods and Zn1-2xMnxLixO nano-particles were synthesized by solvothermal method at 160℃. X-ray diffraction and Raman results showed that Mn ions were well incorporated into the ZnO matrix. No magnetic hysteresis were found in the magnetization curves. The hyperfine structures were observed in electron spin resonance spectra, indicating no ferromagnetic interaction between substituted Mn ions. The co-doping of Li can only change the morphology not the magnetic properties.
基金supported by the Technology Innovation Program(No.10063052,Development of advanced nano-micron coating material and coated cutting tool for Hard-to-Cut)funded By Ministry of Trade,Industry and Energy(MOTIE,Korea)+1 种基金the Basic Research Laboratory Program through the Ministry of Education of the Republic of Korea(No.2019R1A4A1026125)support through the European Research Council under the Advanced Grant“INTERLHYB”—Next Generation of Complex Metallic Materials in Intelligent Hybrid Structures”(No.ERC-2013-ADG-340025)is gratefully acknowledged。
文摘In this study,high entropy metallic glasses(HEMGs)were developed through a combination of concepts for designing metallic glasses(main element+transition metal+metalloid element)and high-entropy alloys(more than five elements,each element having an atomic concentration between 5 at.%and 35 at.%).The developed metallic glass alloys are composed of Co-Fe-Ni main elements,transition metals(Cr,Mo)and metalloid elements(C,B).Moreover,the present work reports the thermal,mechanical and magnetic properties of(CoFeNi)(50)(CrMo)(50-x)(CB)x alloys with x=20,25,30.The developed as-spun HEMGs exhibit typical paramagnetic properties even for a high amount of ferromagnetic elements(Co,Fe,and Ni)and have high elastic modulus(103–160 GPa)and hardness(14–27 GPa),thus possessing mechanical properties similar to well-known Co-based metallic glasses(Co-Cr-Mo-C-B system).In addition,some of the bulk samples prepared with a diameter of 2 mm form bulk metallic glasses with a high compressive strength around 3.5 GPa.The mechanisms determining the stability of the supercooled liquid,as well as the paramagnetic and mechanical properties for the developed non-equiatomic HEMGs,are discussed.
基金Supported by National Natural Science Foundation of China under Grant No.11675051
文摘At low temperature and under weak magnetic field, non-interacting Fermi gases reveal both Pauli paramagnetism and Landau diamagnetism, and the magnitude of the diamagnetic susceptibility is 1/3 of that of the paramagnetic one. When the temperature is finite and the magnetic field is also finite, we demonstrate that the paramagnetism and diamagnetism start to deviate from the ratio 1/3. For understanding the magnetic properties of an ideal Fermi gas at quite low temperature and under quite weak magnetic field, we work out explicitly the third-order magnetic susceptibility in three cases, from intrinsic spin, orbital motion and in total. An interesting property is in third-order magnetic susceptibilities: when viewing individually, they are both diamagnetic, but in total it is paramagnetic.
基金Project(IRT0719) supported by the Program for Changjiang Scholars and Innovative Research Team in University, ChinaProjects (50978088, 51039001) supported by the National Natural Science Foundation of China+3 种基金Project(2009FJ1010) supported by the Hunan Key Scientific Research Program, ChinaProject(10JJ7005) supported by the Natural Science Foundation of Hunan Province, ChinaProjects(CX2009B080, CX2010B157) supported by the Hunan Provincial Innovation Foundation For PostgraduateProject supported by the Fundamental Research Funds for the Central Universities, Hunan University, China
文摘A simple and rapid strategy to construct laccase biosensor for determination of catechol was investigated. Magnetic multiwalled carbon nanotubes (MMCNT) which possess excellent capability of electron transfer were prepared by chemical coprecipitation method. Scanning electron microscope (SEM) and vibrating sample magnetometer (VSM) were used to identify its surfacetopography and magnetization, respectively. Laccase was immobilized on the MMCNT modified magnetic carbon paste electrode by the aid of chitosan/silica (CS) hybrid membrane. Using current-time detection method, the biosensor shows a linear response related to the concentration of catechol in the range from 10-7 to 0.165×10-3 mol/L. The corresponding detection limit is 3.34×10-8 mol/L based on signal-to-noise ratios (S/N) ≥3 under the optimized conditions. In addition, its response current retains 90% of the original after being stored for 45 d. The results indicate that this proposed strategy can be expected to develop other enzyme-based biosensors.
基金Supported by the National Natural Science Foundation of China under Grant Nos. 11275082 and 11178001
文摘The finite-temperature Pauli paramagnetic susceptibility of a three-dimensional ideal anyon gas obeying Haldane fractional exclusion statistics is studied analytically.Different from the result of an ideal Fermi gas,the susceptibility of an ideal anyon gas depends on a statistical factor g in Haldane statistics model.The low-temperature and high-temperature behaviors of the susceptibility are investigated in detail.The Pauli paramagnetic susceptibility of the two-dimensional ideal anyons is also derived.It is found that the reciprocal of the susceptibility has the similar factorizable property which is exhibited in some thermodynamic quantities in two dimensions.
基金Project supported by the National Natural Science Foundation of China (69977005)
文摘CdGd2 （WO4）4 -δ single crystal was grown using the Czochralski＇s method. The crystal structure was tetragonal seheelite with lattice parameters a = b = 0.5203 nm and c = 1. 1359 nm. There were vacancies of （WO4）^2- , therefore, there were some Gd^2＋ ions. Langevin paramagnetism and anisotropy were observed from the δ-T curves at room temperature. The susceptibility X//was 3.5018×10^-3, and X⊥ was 3.4403× 10^-2. The anisotropy was also observed in the electron spin resonance （ESR） experiments. The anisotropic Land6 factors were g//= 2. 1333 and g~ = 2. 8411. The direction of easy magnetization was in the α-b plane. Anisotropic paramagnetic Curie constants C//and C⊥ were not only related to macroscopic a that was observed through the experiment, but were also related to J⊥ and J//, which were the microscopic quantum numbers of the Gd^2＋ and Gd^3｜ ions. Based on the detailed analyses, the proportion of 36.8% of Gd^3＋ ions to 63.2% of Gd^2＋ ions in the Gd ions of the CdGd2（WO4）4-δ crystal was calculated, and δ was 0.638 in the single crystal.
文摘The present study involves co-precipitation method to grow un-doped and Zr-doped bismuth iron oxide with x_（Zr）=0.10–0.30. The molar solutions of ferric chloride（FeCl_3）, zirconyle chloride（ZrOCl_2）, and bismuth chloride（BiCl_3） are prepared in distilled water, and are allowed to react with sodium hydroxide（Na OH）. The synthesized powders are then converted into pellets, which are sintered at 500℃ for two hours in a muffle furnace. X-ray diffraction（XRD） shows multi-phase formation in un-doped and Zr doped samples. Scanning electron microscope（SEM） depicts layered structure at low Zr concentration x_（Zr）= 0.10, while uniform surface with smaller grains and voids is observed at x_（Zr）= 0.20, but at x_（Zr）= 0.30, cracks and voids become prominent. The ferromagnetic nature of the un-doped sample is observed by vibrating sample magnetometer（VSM）, while paramagnetic behavior appears due to Zr doping. The ferromagnetism in un-doped sample is lost by Zr doping, which is due to the formation of additional Fe–O–Zr bonds that induce paramagnetic behavior.
基金Funded by National Natural Science Foundation of China(No.10974148)Sub-project of State Key Development Program of Basic Research of China(Nos. 2009CB939704 and 2009CB939705)
文摘By using inorganic Fe3O4 nanoparticles of different content as nucleation sites, PAn-Fe3O4 nanorods were successfully synthesized through a simple, conventional, and inexpensive one-step in-situ polymerization method. The TEM images revealed the size and morphology of the resultant nanocomposite. The EDS pattern confirmed the existence of Fe3O4 in the composite. The FT-IR spectral analysis confirmed the formation of PAn encapsulated Fe3O4 nanocomposite. With the content of Fe3O4 increasing, the conductivity of the nanocomposites gradually decreases, meanwhile, the saturation magnetization increases and reveals a super paramagnetic behavior. With controllable electrical, magnetic, and electromagnetic properties, the well-prepared nanocomposites may have the potential applications in chemical sensors, catalysis, microwave absorbing, and electro-magneto-rheological fluids, etc.
