We took Co_(0.2)Ni_(0.8)-MOF-74 with bimetallic synergistic effect as the basic material,and selected rare earth ions Ho,Gd,and Er with ion radii close to Co and Ni as the research objects for doping.The influence of ...We took Co_(0.2)Ni_(0.8)-MOF-74 with bimetallic synergistic effect as the basic material,and selected rare earth ions Ho,Gd,and Er with ion radii close to Co and Ni as the research objects for doping.The influence of rare earth ion doping amount and doping type on the eNRR performance of the catalyst was explored.The experimental results show that the ammonia yield rate and Faraday efficiency doped with Co_(0.2)Ni_(0.8)-MOF-0.5Ho are the highest,reaching 1.28×10^(-10)mol·s^(-1)·cm^(-2)/39.8%,which is higher than the1.12×10^(-10)mol·s^(-1)·cm^(-2)/32.2%of Co_(0.2)Ni_(0.8)-MOF-74,and is about 14.3%/23.7%higher than that without doping,respectively.And the stability of Co_(0.2)Ni_(0.8)-MOF-0.5 Ho is good(after 80 hours of continuous testing,the current density did not significantly decrease).This is mainly due to doping,which gives Co_(0.2)Ni_(0.8)-MOF-74 a larger specific surface area and catalytic active sites.The catalyst doped at the same time has more metal cation centers,which increases the electron density of the metal centers and enhances the corresponding eNRR performance.展开更多
We report a facile approach to water-dispersible polydiacetylene/rare earth ions nanocomposites with reversible thermochromism. The nanocomposites were prepared by doping rare earth ions Dy^3＋ or Sin^3＋ into layer-s...We report a facile approach to water-dispersible polydiacetylene/rare earth ions nanocomposites with reversible thermochromism. The nanocomposites were prepared by doping rare earth ions Dy^3＋ or Sin^3＋ into layer-structured 10,12-pentacosadiynoic acid （PCDA） nanopar- ticles to obtain PCDA/rare earth ions nanocomposites （PCDA-RE） and subsequently annealing PCDA-RE at the temperature slightly higher than the melting point of pure PCDA crystals, followed by topochemically polymerizing the annealed PCDA-RE. The polymerized PCDA-RE, i.e. poly（10,12-pentacosadiynoic acid）/rare earth ions nanocomposites （PDARE： PDA-Dy or PDA-Sm）, are largely reversible （PDA-Sm） or even completely reversible （PDA-Dy） in the thermochromism, while, without the doping, pure PDA is completely irreversible. It is confirmed that, PDA-RE are also layer-structured with a d-spacing of 5.4 nm, higher than the d-spacing of pure PDA （4.7 nm）. In PDA-RE, the rare earth ions form a layer in-between and interact strongly with the PDA bilayers, being responsible for the high degree or even the complete reversibility. This is the first example to make PDA completely reversible through the doping of rare earth ions; the annealing process is essential for the complete reversibility since it removes any defects in the structure.展开更多
TiO_2 sols modified by rare earth (RE) ions (Ce^(4+), Eu^(3+), or Nd^(3+))were prepared by coprecipitation-peptization method. The photocatalysis activity was studied byinvestigating the photodegradation effects of ac...TiO_2 sols modified by rare earth (RE) ions (Ce^(4+), Eu^(3+), or Nd^(3+))were prepared by coprecipitation-peptization method. The photocatalysis activity was studied byinvestigating the photodegradation effects of active brilliant red dye X-3B. It is found that TiO_2sols modified by Ce^(4+), Eu^(3+), or Nd^(3+) have the anatase crystalline structure, which areprepared at 70℃. All RE^(n+)-TiO_2 sol samples have uniform nanoparticles with similar morphology,which are homogenously distributed in aqueous colloidal systems. The particle sizes are 10, 8, and12 nm for Nd^(3+)-TiO_2, Eu^(3+)-TiO_2, and Ce^(4+)-TiO_2, respectively. The character of ultrafineand positive charge sol particles contributes to the good adsorption of X-3B dye molecule on thesurface of titania (about 30% X-3B adsorption amount). Experimental results exhibit thatRE^(n+)-TiO_2 sol photocatalysts have the capability to photodegrade X-3B under visible lightirradiation. Nd^(3+)-TiO_2 and Eu^(3+)-TiO_2 show higher photocatalytic activity than Ce^(4+)-TiO_2,which is due to the difference of standard redox potential of RE^(n+)/RE^((n-1)+). RE^(n+)-TiO_2sols demonstrate more excellent interfacial adsorption and photodegradation effects to X-3B thanP_(25) TiO_2 crystallites. Moreover, the degradation mechanism of X-3B is proposed as dyephotosensitization and electron scavenging by rare earth ions.展开更多
TiO2/V2O5 catalyst doped with rare earth ions was prepared by sol-gel method. Titanium tetrapropoxide and vanadium pentoxide were used as precursor of the composite catalyst and rare earth ions were used as dopant. Th...TiO2/V2O5 catalyst doped with rare earth ions was prepared by sol-gel method. Titanium tetrapropoxide and vanadium pentoxide were used as precursor of the composite catalyst and rare earth ions were used as dopant. The crystal phases, crystalline sizes, microstructure, absorption spectra of doped composite catalyst were studied by XRD, EDS, FT-IR and UV-Vis. Photoactivity of the prepared catalyst under ultraviolet irradiation were evaluated by degradation of methyl orange （MO） in aqueous solution. It is shown that the prepared catalyst is composed of anatase and futile. The rare earth ions are highly dispersed in composite catalyst. All the doped catalysts appear higher photocatalytic activity than TiO2/V2O5 catalyst and catalyst doped with Ce^4＋ present the best activity to MO.展开更多
Fast and sensitive detection of dilute rare earth species still represents a challenge for an on-site survey of new resources and evaluation of the economic value. In this work, a robust and low-cost protocol has been...Fast and sensitive detection of dilute rare earth species still represents a challenge for an on-site survey of new resources and evaluation of the economic value. In this work, a robust and low-cost protocol has been developed to analyze the concentration of rare earth ions using a smartphone camera. The success of this protocol relies on mesoporous silica nanoparticles(MSNs) with large-area negatively charged surfaces, on which the rare earth cations(e.g., Eu^(3+)) are efficiently adsorbed through electrostatic attraction to enable a ‘‘concentrating effect''. The initial adsorption rate is as fast as 4025 mg(g min)^(-1), and the adsorption capacity of Eu^(3+)ions in the MSNs is as high as 4730 mg g^(-1)(equivalent to ～41.2 M) at 70 °C. The concentrated Eu^(3+)ions in the MSNs can form a complex with a light sensitizer of 1,10-phenanthroline to significantly enhance the characteristic red emission of Eu^(3+)ions due to an ‘‘antenna effect'' that relies on the efficient energy transfer from the light sensitizer to the Eu^(3+)ions.The positive synergy of ‘‘concentrating effect'' and ‘‘antenna effect'' in the MSNs enables the analysis of rare earth ions in a wide dynamic range and with a detection limit down to ～80 nM even using a smartphone camera. Our results highlight the promise of the protocol in fieldwork for exploring valuable rare earth resources.展开更多
Well-ordered metal structures, i.e. arrays of nanosized tips on silver surface for studies of the luminescence enhancement of absorbed media with rare earth ions were used. These arrays were prepared by the metal evap...Well-ordered metal structures, i.e. arrays of nanosized tips on silver surface for studies of the luminescence enhancement of absorbed media with rare earth ions were used. These arrays were prepared by the metal evaporation on track membranes. Calculations of reso- nanee frequencies of tips regarded as semispheroids were done taking into account the interaction between dipoles of tips. They were used to discuss experimental results for media with Eu（NO3）3·6H2O salt basing on data for bulk silver dielectric function.展开更多
The limitation of the random walk theory of energy transfer between rare earth ions in crystals published in literatures is pointed out in this paper. A modified model, which can be used in any level of rare earth ion...The limitation of the random walk theory of energy transfer between rare earth ions in crystals published in literatures is pointed out in this paper. A modified model, which can be used in any level of rare earth ion concentration when the interaction between donor and acceptor is different from that between donors, is introduced. measured fluorescence lifetimes of Yb^3＋：YAl3（BO3）4 This model has been applied to analyze the with a series of Yb^3＋ concentrations.展开更多
The widely used energy transfer theory is a foundation of luminescence, in which the rates of Stokes and anti-Stokes processes have the same calculation formula. An improvement on the anti-Stokes energy transfer to ex...The widely used energy transfer theory is a foundation of luminescence, in which the rates of Stokes and anti-Stokes processes have the same calculation formula. An improvement on the anti-Stokes energy transfer to explain the fluorescence intensity reversal between the red and green fluorescence of Er（0.5）Yb（9.5）：FOV is reported in the present article. The range of the intensity reversal Z was measured to be 877. Dynamic processes for 16 levels were simulated. A coefficient, the improvement factor of the intensity ratio of Stokes to anti-Stokes processes in quantum Raman theory compared to classical Raman theory, is introduced to successfully describe the anti-Stokes energy transfer. A new method to calculate the distance between the rare earth ions, which is critical for the energy transfer calculation, is proposed. The validity of these important improvements is also proved by experiment.展开更多
The rare earth ion Yb^3+ doped Bi2WO6 photocatalysts were synthesized by hydrothermal method.Moreover,XRD,XPS,FESEM,TEM,Ramam,N2 adsorption-desorption isotherm measurements and UV-vis diffusion reflectance spectra wer...The rare earth ion Yb^3+ doped Bi2WO6 photocatalysts were synthesized by hydrothermal method.Moreover,XRD,XPS,FESEM,TEM,Ramam,N2 adsorption-desorption isotherm measurements and UV-vis diffusion reflectance spectra were used to characterize the Yb^3+ doped Bi2WO6 photocatalysts.The morphology,specific surface area,and pore volume distribution were greatly affected after Yb3+ ions doping.Photocatalytic performance of Bi2WO6 was effectively enhanced after Yb3+ ions doping,6% Yb^3+ doped Bi2WO6 had the best photocatalytic performance,and 96.2% Rhodamine B was degradated after irradiated 30 min,which was 1.29 times that of the pristine one.The enhanced photocatalytic performance was due to the increased specific surface area,decreased energy band gap and inhibition of photoelectron-hole recombination after Yb3+ ions doping.展开更多
In this paper,the influence of crystal-field on the Luminescence properties of Eu^(2+) in complex oxides are studied theoretically by using purely electrostatic model,the dependence of the 4f^65d levels on Eu-O bond d...In this paper,the influence of crystal-field on the Luminescence properties of Eu^(2+) in complex oxides are studied theoretically by using purely electrostatic model,the dependence of the 4f^65d levels on Eu-O bond distance is given.Quantum chemistry calculation shows that the splitting extent of 4f^65d energy band in cubic or in octahedral fields will be inversely proportional to R^5,where R is the distance of Eu^(2+) to oxygen ligand.The value of R affects slightly the location of the centre of 4f^65d energy band.According to the exper- imental spectrum data,we have discussed the influence of the host chemical composition,the replaced sites of Eu^(2+) and degree of covalency of Eu-O bond on luminescence properties of Eu^(2+).Some regularity of fluorescence spectrum was observed. In alkali-alkaline earth-phosphates,the splitting extent of 4f^65d band (△E) becomes smaller as the Eu-O bond distance (R) increases.In Na_(3-x)(PO_4)_(1-x)(SO_4)_x and Na_(2-x)CaSi_(1-x)P_xO_4 hosts,d-d emission peak of Eu^(2+) will shift to shorter wavelength with the increase of x's value. The crystal structure data show that Eu^(2+) in K_2Mg_2(SO_4)_3 is affected more strongly by crystal-field and covalancy than in KMgF_3,so K_2Mg_2(SO_4)_3:Eu^(2+) emits blue light (E_(em)~m=400nm) and KMgF_3:Eu^(2+) produces ultraviolet fluorescence.展开更多
The adsorption characteristics of rare earth ion La(Ⅲ) on Yunnan bowl tea surface from aqueous solution and effects of various surfactants on the adsorption were studied. It was found that Yunnan bowl tea can adsorb ...The adsorption characteristics of rare earth ion La(Ⅲ) on Yunnan bowl tea surface from aqueous solution and effects of various surfactants on the adsorption were studied. It was found that Yunnan bowl tea can adsorb strongly La(Ⅲ) and pH may affect drastically the adsorption amount of La(Ⅲ). The adsorption law of La(Ⅲ) on Yunnan bowl tea surface follows the Langmuir equation. The maximum adsorption amount of La(Ⅲ) can reach 15 mg·g (-1). A comprehensive adsorption model is suggested according to the experimental results.展开更多
It was observed that rare earth ions (Nd 3+, Sm 3+, Eu 3+, Gd 3+, Tb 3+) have significant quenching effects on the fluorescence of anticoagulation factor I (ACF I). The results of the fluorescence titra...It was observed that rare earth ions (Nd 3+, Sm 3+, Eu 3+, Gd 3+, Tb 3+) have significant quenching effects on the fluorescence of anticoagulation factor I (ACF I). The results of the fluorescence titration of ACF I with rare earth ions demonstrate that ACF I has two RE 3+-binding sites, and the rare earth ions and Ca 2+ bind to ACF I competitively in the two similar sites. The association constants K 1 and K 2 of ACF I with each rare earth ions (Nd 3+, Sm 3+, Eu 3+, Gd 3+, Tb 3+) are close to each other, which indicates the structural similarity of the two binding sites in ACF I. Although the ionic radii of Nd 3+, Sm 3+, Eu 3+, Gd 3+ and Tb 3+ are different, both their K 1 and K 2 are similar, respectively. This reveals the conformational flexibility of the two binding sites in ACF I, which offers a possibility for Ca 2+ to take play in the inducing conformational changes of ACF I and the promoting the binding of ACF I with activated coagulation factor X.展开更多
Improving the seepage of leaching solution in the ore body and strengthening the mass transfer process of rare earth ions during in-situ leaching are two critical methods to improve the leaching efficiency of rare ear...Improving the seepage of leaching solution in the ore body and strengthening the mass transfer process of rare earth ions during in-situ leaching are two critical methods to improve the leaching efficiency of rare earth.In this study,2 wt%MgSO_(4)solution was used for the indoor simulated column leaching experiment on rare earth samples and an electric field was applied at both ends of the samples.Then the effects of different intensities,initial application time and duration of the electric field on the rare earth leaching system and its mechanism were investigated.The results show that compared with the single MgSO_(4)solution leaching,applying an electric field with a strength of 6 V/cm can save the leaching time of 30 min and increase the flow velocity of the rare earth leachate by 26.98%.Under the optimal conditions of applying an electric field with a strength of 6 V/cm for 20 min to the leaching system after10 min of the rare earth leachate flowing out,the leaching efficiency of sample increases from 81.20% to 86.05% with the increase of 4.85%.The mechanism analysis shows that when a direct current electric field is applied to the rare earth leaching system,rare earth ions rapidly change from disorderly movement with the seepage into faster and directional movement.In addition,the seepage of the leaching solution is also improved due to the increase of the cross-sectional area of the seepage channel,the polarized water molecules migrate directionally by force from the negative pole,and the movement of the hydrogen is generated by the electrolytic water.More impo rtantly,based on the principle of in-situ leaching process,the layout of injection holes and deflector holes in this process provides a natural site for the electrode layout of the electric field.With the simple equipme nt and the ope ration,the rare earth leaching process with the applied electric field has high feasibility in industrial application.展开更多
Rare earth elements are indispensable raw materials for advanced aero-engines, special optical materials, and high-performance electronic products. With the development of the social economy, the global demand for rar...Rare earth elements are indispensable raw materials for advanced aero-engines, special optical materials, and high-performance electronic products. With the development of the social economy, the global demand for rare earth resources is increasing, and rare earths have become a key metal for the development of new industries and frontier technologies that are highly valued both at home and abroad. Ion-adsorbed rare earth ores are an important source of rare earths, so the efficient green leaching of ion-adsorbed rare earths is important. Researchers found that the selection of an efficient green leaching agent for ion-adsorbed rare earths is based on the zeta potential of tailing clay minerals in addition to leaching efficiency, and both zeta potential and leaching ion concentration are related to mineral acidity and alkalinity, and the pH of tailing water suspension is a direct indicator of environmental water quality requirements. Therefore, the efficiency of the leaching process is closely integrated with the environmental evaluation, and the characteristics and correlation of the changes in zeta potential, pH, conductivity and pollutant concentration of the pulp of clay mineral content during the leaching process of ore leaching and tailings aqueous electrolyte solution leaching are studied by evaluating the leaching system, and a set of correlation leaching efficiency and environmental impact evaluation method is established based on the results of the above analysis, which is of scientific development of ion adsorption rare earth resources. It has important theoretical significance and practical application value.展开更多
Single-phase multiferroic BiFeO3 and Bi（0.9）（La/Nd）（0.1）FeO3（doped with rare earth ions La-（3＋） and Nd-（3＋）） films grown on（111）-Pt/Ti/SiO2/Si substrate were prepared via sol-gel method and a subsequen...Single-phase multiferroic BiFeO3 and Bi（0.9）（La/Nd）（0.1）FeO3（doped with rare earth ions La-（3＋） and Nd-（3＋）） films grown on（111）-Pt/Ti/SiO2/Si substrate were prepared via sol-gel method and a subsequent rapid thermal process. The phase composition, microstructure, ferroelectric, dielectric, ferromagnetic properties were investigated, and meanwhile, the in-plane magnetoelectric（ME） coupling effects of the films were reported and studied for the first time in this work. Structural characterization by X-ray diffraction and scanning electron microscopy showed that both BiFeO3 and Bi（0.9）（La/Nd）（0.1）FeO3 exhabited a rhombohedral structure with（111） preferred orientation. The results of the physical properties indicated that the introduction of rare earth ions improved significantly the polarization, magnetization and dielectric properties than the undoped BiFeO3 crystals, and it enhanced effectively the in-plane ME coupling（the ME coupling coefficient αE increased from 0.13 in the pure BiFeO3 to 0.21 in Bi（0.9）La（0.1）FeO3 and 0.34 V/（Oe·cm） in Bi（0.9）Nd（0.1）FeO3）. The mechanism of these phenomena was investigated systematically.展开更多
Ca1-xRxCu3Ti4O12(R=La,Y,Gd;x=0,0.1,0.2,0.3) electronic ceramics were fabricated by conventional solid-state reaction method.The microstructure and dielectric properties as well as impedance behavior were carefully inv...Ca1-xRxCu3Ti4O12(R=La,Y,Gd;x=0,0.1,0.2,0.3) electronic ceramics were fabricated by conventional solid-state reaction method.The microstructure and dielectric properties as well as impedance behavior were carefully investigated.XRD results showed that the secondary phases with the general formula R2Ti2O7 existed at grain boundaries of rare earth doped ceramics,which inhibited abnormal grain growth.The dielectric constant decreased from 4×105 in pure CaCu3Ti4O12(CCTO) ceramics to 2×103 with rare earth doping....展开更多
In this work,15 types of rare earth(Re)ions,including Y^(3+),La^(3+),Ce^(3+),Pr^(3+),Nd^(3+),Sm^(3+),Eu^(3+),Gd^(3+),Tb^(3+),Dy^(3+),Ho^(3+),Er^(3+),Tm^(3+),Yb^(3+)and Lu^(3+)doped perovskite SrTiO_(3)powders were syn...In this work,15 types of rare earth(Re)ions,including Y^(3+),La^(3+),Ce^(3+),Pr^(3+),Nd^(3+),Sm^(3+),Eu^(3+),Gd^(3+),Tb^(3+),Dy^(3+),Ho^(3+),Er^(3+),Tm^(3+),Yb^(3+)and Lu^(3+)doped perovskite SrTiO_(3)powders were synthesized by solgel method.The influence of Re ions doping on the crystal structure,morphology and optical property as well as the photocatalytic activity for the photodegradation of rhodamine B(RhB)was investigated in detail when the synthesized Re ions doped SrTiO_(3)powders were served as catalysts.The presented results revealed that the crystal structure is invariable,whereas the morphology and the optical bandgap are variable for the resultant SrTiO_(3)powders when different Re ions were incorporated into the SrTiO_(3)lattice.The relatedness between the morphology,optical property and photocatalytic activity of the synthesized SrTiO_(3)catalysts doped with variable Re ions were analyzed deeply,providing an insight into the influence factors on the photocatalytic activity of catalysts.展开更多
Undoped and rare earth ions （Eu3＋, Ce3＋, Tb3＋） doped β-SrHPO4 nanomaterials were successfully prepared by a facile hydrothermal method. The crystal structure, morphology and luminescent properties were character...Undoped and rare earth ions （Eu3＋, Ce3＋, Tb3＋） doped β-SrHPO4 nanomaterials were successfully prepared by a facile hydrothermal method. The crystal structure, morphology and luminescent properties were characterized by X-ray powder diffraction （XRD）, scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, photoluminescence （PL） spectra and lumi- nescence decay curves. The results indicated that the tmdoped and rare earth ions doped SrHPO4 nanomaterials （the doping concen- tration was not above 7%） were well crystallized, with the same crystal structure （^-SrHPO4）. Nevertheless, the doping of rare earth ions could lead to the changing of morphology from nanoflakes to nanocrystals. Under the excitation of UV light, rare earth ions （Eu3＋, Ce3＋, Tb3＋） doped I3-SrHPO4 nanocrystals exhibited the characteristic emission of Eu3＋, Ce3＋ and Tb3＋ ions, respectively. The luminescence decay curves of [3-SrHPO4：Eu3＋ and D-SrHPO4：Ce3＋,Th3＋ nanocrystals conformed to the double exponential fluores- cence decay, and the average lifetimes were 1.14 and 4.12 ms, respectively. The luminescence decay curve of 13-SrHPO4：Ce3＋ was fitted into a single exponential function, and the lifetime was about 0.78 ns.展开更多
LiFe0.99RE0.01PO4/C cathode material was synthesized by solid-state reaction method using FeC2O4-2H2O, Li2CO3, NH4H2PO4, RE（NO3）3·nH2O as raw materials and glucose as a carbon source. The doping effects of rare...LiFe0.99RE0.01PO4/C cathode material was synthesized by solid-state reaction method using FeC2O4-2H2O, Li2CO3, NH4H2PO4, RE（NO3）3·nH2O as raw materials and glucose as a carbon source. The doping effects of rare earth ions, such as La3＋, Ce3＋, Nd3＋, on the structure and electrochemical properties of LiFePO4/C cathode material were systematically investigated. The as-prepared samples were characterized by means of X-ray diffraction （XRD）, scanning electron microscopy （SEM） and particle size analysis. The electrochemical properties were investigated in terms of constant-current charge/discharge cycling tests. The XRD results showed that the rare earth ions doping did not change the olivine structure of LiFePO4, and all the doped samples were of single-phase with high crystallinity. SEM and particle size analysis results showed that the doping of La3＋, Ce3＋ and Nds＋ led to the decrease of particle size. The electrochemical results exhibited that the doping of La3＋ and Ce3＋ could improve the high-rate capability of LiFePO4/C cathode material, among which, the material doped with 1% Ce3＋ exhibited the optimal electrochemical properties, whose specific discharge capacities could reach 128.9, 119.5 and 104.4 mAh/g at 1C, 2C and 5C rates, respectively.展开更多
Ytterbium and rare earth ions(RE=Y,Gd,La)codoped CaF_(2)-SrF_(2)single crystals(3 at%Yb,6 at%RE:CaF_(2)-SrF_(2))were fabricated by temperature gradient technology(TGT).All the space groups remain the same Fm3m as that...Ytterbium and rare earth ions(RE=Y,Gd,La)codoped CaF_(2)-SrF_(2)single crystals(3 at%Yb,6 at%RE:CaF_(2)-SrF_(2))were fabricated by temperature gradient technology(TGT).All the space groups remain the same Fm3m as that of Yb:CaF_(2)-SrF_(2).The lattice parameter a,unit cell volume V,as well as bond length of Ca/Sr-F and F-F increase in the sequence of rare-earth ions radius Y^(3+)<Gd^(3+)<La^(3+).The segregation coefficients of Yb ions are 0.87 in Yb,La:CaF_(2)-SrF_(2)and Yb,Gd:CaF_(2)-SrF_(2),which are larger than 0.85 in Yb,Y:CaF_(2)-SrF_(2)and 0.80 in Yb:CaF_(2)-SrF_(2).Absorption spectra in the range of 200 and 400 nm were analysed with Yb^(2+)contents.The absorption and emission cross-sections in the range of 900-1100 nm were determined together with fluorescence lifetime.The saturation pump density/Sat,minimum pump density/m in and gain cross-section were analysed.Yb,La:CaF_(2)-SrF_(2)has a relatively higher optical parameter(δem×t,0.52×10^(20)cm^(2)·ms),lower Isat(3.68 kW/cm^(2))and^min(0.50 kW/cm^(2))at 1038 nm indicating the potential application in high power laser.Low phonon energy of CaF_(2)-SrF_(2)is 302 cm^(-1)which is located between those of CaF_(2)and SrF_(2)as measured by Raman spectra.It is believed that ytterbium and rare earth ions(RE=Y^(3+),Cd^(3+),La^(3+))codoped CaF_(2)-SrF_(2)eutectic solid-solution is promising for high-power and wavelength-tunable solid-state lasers.展开更多
基金Funded by the Central Government Guides Local Funds for Scientific and Technological Development(No.2023ZYQ004)the Hunan Provincial Natural Science Foundation of China(No.2021JJ50036)the Hunan Provincial Key Research and Development Plan(No.2023GK2083)。
文摘We took Co_(0.2)Ni_(0.8)-MOF-74 with bimetallic synergistic effect as the basic material,and selected rare earth ions Ho,Gd,and Er with ion radii close to Co and Ni as the research objects for doping.The influence of rare earth ion doping amount and doping type on the eNRR performance of the catalyst was explored.The experimental results show that the ammonia yield rate and Faraday efficiency doped with Co_(0.2)Ni_(0.8)-MOF-0.5Ho are the highest,reaching 1.28×10^(-10)mol·s^(-1)·cm^(-2)/39.8%,which is higher than the1.12×10^(-10)mol·s^(-1)·cm^(-2)/32.2%of Co_(0.2)Ni_(0.8)-MOF-74,and is about 14.3%/23.7%higher than that without doping,respectively.And the stability of Co_(0.2)Ni_(0.8)-MOF-0.5 Ho is good(after 80 hours of continuous testing,the current density did not significantly decrease).This is mainly due to doping,which gives Co_(0.2)Ni_(0.8)-MOF-74 a larger specific surface area and catalytic active sites.The catalyst doped at the same time has more metal cation centers,which increases the electron density of the metal centers and enhances the corresponding eNRR performance.
基金V.ACKNOWLEDGEMENTSThisworkwassupportedbytheNationalNatu-ralScienceFoundationofChina（No.21334001andNo.91127030）.V. ACKNOWLEDGEMENTS This work was supported by the National Natu- ral Science Foundation of China （No.21334001 and No.91127030）.
文摘We report a facile approach to water-dispersible polydiacetylene/rare earth ions nanocomposites with reversible thermochromism. The nanocomposites were prepared by doping rare earth ions Dy^3＋ or Sin^3＋ into layer-structured 10,12-pentacosadiynoic acid （PCDA） nanopar- ticles to obtain PCDA/rare earth ions nanocomposites （PCDA-RE） and subsequently annealing PCDA-RE at the temperature slightly higher than the melting point of pure PCDA crystals, followed by topochemically polymerizing the annealed PCDA-RE. The polymerized PCDA-RE, i.e. poly（10,12-pentacosadiynoic acid）/rare earth ions nanocomposites （PDARE： PDA-Dy or PDA-Sm）, are largely reversible （PDA-Sm） or even completely reversible （PDA-Dy） in the thermochromism, while, without the doping, pure PDA is completely irreversible. It is confirmed that, PDA-RE are also layer-structured with a d-spacing of 5.4 nm, higher than the d-spacing of pure PDA （4.7 nm）. In PDA-RE, the rare earth ions form a layer in-between and interact strongly with the PDA bilayers, being responsible for the high degree or even the complete reversibility. This is the first example to make PDA completely reversible through the doping of rare earth ions; the annealing process is essential for the complete reversibility since it removes any defects in the structure.
基金This work was financially supported by the Hi-Tech Research and Development Program (863 Program) of China (No. 2002AA302304)the National Natural Science Foundation of China (No. 60121101)the Education Department Foundation of Jiangsu Province (JHOl-
文摘TiO_2 sols modified by rare earth (RE) ions (Ce^(4+), Eu^(3+), or Nd^(3+))were prepared by coprecipitation-peptization method. The photocatalysis activity was studied byinvestigating the photodegradation effects of active brilliant red dye X-3B. It is found that TiO_2sols modified by Ce^(4+), Eu^(3+), or Nd^(3+) have the anatase crystalline structure, which areprepared at 70℃. All RE^(n+)-TiO_2 sol samples have uniform nanoparticles with similar morphology,which are homogenously distributed in aqueous colloidal systems. The particle sizes are 10, 8, and12 nm for Nd^(3+)-TiO_2, Eu^(3+)-TiO_2, and Ce^(4+)-TiO_2, respectively. The character of ultrafineand positive charge sol particles contributes to the good adsorption of X-3B dye molecule on thesurface of titania (about 30% X-3B adsorption amount). Experimental results exhibit thatRE^(n+)-TiO_2 sol photocatalysts have the capability to photodegrade X-3B under visible lightirradiation. Nd^(3+)-TiO_2 and Eu^(3+)-TiO_2 show higher photocatalytic activity than Ce^(4+)-TiO_2,which is due to the difference of standard redox potential of RE^(n+)/RE^((n-1)+). RE^(n+)-TiO_2sols demonstrate more excellent interfacial adsorption and photodegradation effects to X-3B thanP_(25) TiO_2 crystallites. Moreover, the degradation mechanism of X-3B is proposed as dyephotosensitization and electron scavenging by rare earth ions.
基金Project supported by the National Natural Science Foundation of China (50571003)
文摘TiO2/V2O5 catalyst doped with rare earth ions was prepared by sol-gel method. Titanium tetrapropoxide and vanadium pentoxide were used as precursor of the composite catalyst and rare earth ions were used as dopant. The crystal phases, crystalline sizes, microstructure, absorption spectra of doped composite catalyst were studied by XRD, EDS, FT-IR and UV-Vis. Photoactivity of the prepared catalyst under ultraviolet irradiation were evaluated by degradation of methyl orange （MO） in aqueous solution. It is shown that the prepared catalyst is composed of anatase and futile. The rare earth ions are highly dispersed in composite catalyst. All the doped catalysts appear higher photocatalytic activity than TiO2/V2O5 catalyst and catalyst doped with Ce^4＋ present the best activity to MO.
基金supported by the start-up and OVPR seed Grant from Temple University
文摘Fast and sensitive detection of dilute rare earth species still represents a challenge for an on-site survey of new resources and evaluation of the economic value. In this work, a robust and low-cost protocol has been developed to analyze the concentration of rare earth ions using a smartphone camera. The success of this protocol relies on mesoporous silica nanoparticles(MSNs) with large-area negatively charged surfaces, on which the rare earth cations(e.g., Eu^(3+)) are efficiently adsorbed through electrostatic attraction to enable a ‘‘concentrating effect''. The initial adsorption rate is as fast as 4025 mg(g min)^(-1), and the adsorption capacity of Eu^(3+)ions in the MSNs is as high as 4730 mg g^(-1)(equivalent to ～41.2 M) at 70 °C. The concentrated Eu^(3+)ions in the MSNs can form a complex with a light sensitizer of 1,10-phenanthroline to significantly enhance the characteristic red emission of Eu^(3+)ions due to an ‘‘antenna effect'' that relies on the efficient energy transfer from the light sensitizer to the Eu^(3+)ions.The positive synergy of ‘‘concentrating effect'' and ‘‘antenna effect'' in the MSNs enables the analysis of rare earth ions in a wide dynamic range and with a detection limit down to ～80 nM even using a smartphone camera. Our results highlight the promise of the protocol in fieldwork for exploring valuable rare earth resources.
文摘Well-ordered metal structures, i.e. arrays of nanosized tips on silver surface for studies of the luminescence enhancement of absorbed media with rare earth ions were used. These arrays were prepared by the metal evaporation on track membranes. Calculations of reso- nanee frequencies of tips regarded as semispheroids were done taking into account the interaction between dipoles of tips. They were used to discuss experimental results for media with Eu（NO3）3·6H2O salt basing on data for bulk silver dielectric function.
基金the National Natural Science Foundation of China (Nos. 50590405)the Natural Science Foundation of Fujian Province (No. A0610031)
文摘The limitation of the random walk theory of energy transfer between rare earth ions in crystals published in literatures is pointed out in this paper. A modified model, which can be used in any level of rare earth ion concentration when the interaction between donor and acceptor is different from that between donors, is introduced. measured fluorescence lifetimes of Yb^3＋：YAl3（BO3）4 This model has been applied to analyze the with a series of Yb^3＋ concentrations.
基金Project supported by the National Natural Science Foundation of China (Grant No 10674019)
文摘The widely used energy transfer theory is a foundation of luminescence, in which the rates of Stokes and anti-Stokes processes have the same calculation formula. An improvement on the anti-Stokes energy transfer to explain the fluorescence intensity reversal between the red and green fluorescence of Er（0.5）Yb（9.5）：FOV is reported in the present article. The range of the intensity reversal Z was measured to be 877. Dynamic processes for 16 levels were simulated. A coefficient, the improvement factor of the intensity ratio of Stokes to anti-Stokes processes in quantum Raman theory compared to classical Raman theory, is introduced to successfully describe the anti-Stokes energy transfer. A new method to calculate the distance between the rare earth ions, which is critical for the energy transfer calculation, is proposed. The validity of these important improvements is also proved by experiment.
基金the National Natural Science Foundation of China(No.51662005)。
文摘The rare earth ion Yb^3+ doped Bi2WO6 photocatalysts were synthesized by hydrothermal method.Moreover,XRD,XPS,FESEM,TEM,Ramam,N2 adsorption-desorption isotherm measurements and UV-vis diffusion reflectance spectra were used to characterize the Yb^3+ doped Bi2WO6 photocatalysts.The morphology,specific surface area,and pore volume distribution were greatly affected after Yb3+ ions doping.Photocatalytic performance of Bi2WO6 was effectively enhanced after Yb3+ ions doping,6% Yb^3+ doped Bi2WO6 had the best photocatalytic performance,and 96.2% Rhodamine B was degradated after irradiated 30 min,which was 1.29 times that of the pristine one.The enhanced photocatalytic performance was due to the increased specific surface area,decreased energy band gap and inhibition of photoelectron-hole recombination after Yb3+ ions doping.
文摘In this paper,the influence of crystal-field on the Luminescence properties of Eu^(2+) in complex oxides are studied theoretically by using purely electrostatic model,the dependence of the 4f^65d levels on Eu-O bond distance is given.Quantum chemistry calculation shows that the splitting extent of 4f^65d energy band in cubic or in octahedral fields will be inversely proportional to R^5,where R is the distance of Eu^(2+) to oxygen ligand.The value of R affects slightly the location of the centre of 4f^65d energy band.According to the exper- imental spectrum data,we have discussed the influence of the host chemical composition,the replaced sites of Eu^(2+) and degree of covalency of Eu-O bond on luminescence properties of Eu^(2+).Some regularity of fluorescence spectrum was observed. In alkali-alkaline earth-phosphates,the splitting extent of 4f^65d band (△E) becomes smaller as the Eu-O bond distance (R) increases.In Na_(3-x)(PO_4)_(1-x)(SO_4)_x and Na_(2-x)CaSi_(1-x)P_xO_4 hosts,d-d emission peak of Eu^(2+) will shift to shorter wavelength with the increase of x's value. The crystal structure data show that Eu^(2+) in K_2Mg_2(SO_4)_3 is affected more strongly by crystal-field and covalancy than in KMgF_3,so K_2Mg_2(SO_4)_3:Eu^(2+) emits blue light (E_(em)~m=400nm) and KMgF_3:Eu^(2+) produces ultraviolet fluorescence.
文摘The adsorption characteristics of rare earth ion La(Ⅲ) on Yunnan bowl tea surface from aqueous solution and effects of various surfactants on the adsorption were studied. It was found that Yunnan bowl tea can adsorb strongly La(Ⅲ) and pH may affect drastically the adsorption amount of La(Ⅲ). The adsorption law of La(Ⅲ) on Yunnan bowl tea surface follows the Langmuir equation. The maximum adsorption amount of La(Ⅲ) can reach 15 mg·g (-1). A comprehensive adsorption model is suggested according to the experimental results.
文摘It was observed that rare earth ions (Nd 3+, Sm 3+, Eu 3+, Gd 3+, Tb 3+) have significant quenching effects on the fluorescence of anticoagulation factor I (ACF I). The results of the fluorescence titration of ACF I with rare earth ions demonstrate that ACF I has two RE 3+-binding sites, and the rare earth ions and Ca 2+ bind to ACF I competitively in the two similar sites. The association constants K 1 and K 2 of ACF I with each rare earth ions (Nd 3+, Sm 3+, Eu 3+, Gd 3+, Tb 3+) are close to each other, which indicates the structural similarity of the two binding sites in ACF I. Although the ionic radii of Nd 3+, Sm 3+, Eu 3+, Gd 3+ and Tb 3+ are different, both their K 1 and K 2 are similar, respectively. This reveals the conformational flexibility of the two binding sites in ACF I, which offers a possibility for Ca 2+ to take play in the inducing conformational changes of ACF I and the promoting the binding of ACF I with activated coagulation factor X.
基金Projects supported by the National Key R&D Program of China(2020YFC1909000)Self-deployed Projects of Ganjiang Innovation Academy,Chinese Academy of Sciences(E055A001,E055A002)+1 种基金Key Research Programs of the Chinese Academy of Sciences(ZDRW-CN-2021-3)National Natural Science Foundation of China(52174113,51874148)。
文摘Improving the seepage of leaching solution in the ore body and strengthening the mass transfer process of rare earth ions during in-situ leaching are two critical methods to improve the leaching efficiency of rare earth.In this study,2 wt%MgSO_(4)solution was used for the indoor simulated column leaching experiment on rare earth samples and an electric field was applied at both ends of the samples.Then the effects of different intensities,initial application time and duration of the electric field on the rare earth leaching system and its mechanism were investigated.The results show that compared with the single MgSO_(4)solution leaching,applying an electric field with a strength of 6 V/cm can save the leaching time of 30 min and increase the flow velocity of the rare earth leachate by 26.98%.Under the optimal conditions of applying an electric field with a strength of 6 V/cm for 20 min to the leaching system after10 min of the rare earth leachate flowing out,the leaching efficiency of sample increases from 81.20% to 86.05% with the increase of 4.85%.The mechanism analysis shows that when a direct current electric field is applied to the rare earth leaching system,rare earth ions rapidly change from disorderly movement with the seepage into faster and directional movement.In addition,the seepage of the leaching solution is also improved due to the increase of the cross-sectional area of the seepage channel,the polarized water molecules migrate directionally by force from the negative pole,and the movement of the hydrogen is generated by the electrolytic water.More impo rtantly,based on the principle of in-situ leaching process,the layout of injection holes and deflector holes in this process provides a natural site for the electrode layout of the electric field.With the simple equipme nt and the ope ration,the rare earth leaching process with the applied electric field has high feasibility in industrial application.
文摘Rare earth elements are indispensable raw materials for advanced aero-engines, special optical materials, and high-performance electronic products. With the development of the social economy, the global demand for rare earth resources is increasing, and rare earths have become a key metal for the development of new industries and frontier technologies that are highly valued both at home and abroad. Ion-adsorbed rare earth ores are an important source of rare earths, so the efficient green leaching of ion-adsorbed rare earths is important. Researchers found that the selection of an efficient green leaching agent for ion-adsorbed rare earths is based on the zeta potential of tailing clay minerals in addition to leaching efficiency, and both zeta potential and leaching ion concentration are related to mineral acidity and alkalinity, and the pH of tailing water suspension is a direct indicator of environmental water quality requirements. Therefore, the efficiency of the leaching process is closely integrated with the environmental evaluation, and the characteristics and correlation of the changes in zeta potential, pH, conductivity and pollutant concentration of the pulp of clay mineral content during the leaching process of ore leaching and tailings aqueous electrolyte solution leaching are studied by evaluating the leaching system, and a set of correlation leaching efficiency and environmental impact evaluation method is established based on the results of the above analysis, which is of scientific development of ion adsorption rare earth resources. It has important theoretical significance and practical application value.
基金Project supported by National Natural Science Foundation of China(51462003)Science Research Fund of Guizhou Province,China(2015-4006,2014-001,2014-7612)+1 种基金the Introduced Talents Funds of Guizhou University(2014-30)Master’s Innovation Funds of Guizhou University(2016065)
文摘Single-phase multiferroic BiFeO3 and Bi（0.9）（La/Nd）（0.1）FeO3（doped with rare earth ions La-（3＋） and Nd-（3＋）） films grown on（111）-Pt/Ti/SiO2/Si substrate were prepared via sol-gel method and a subsequent rapid thermal process. The phase composition, microstructure, ferroelectric, dielectric, ferromagnetic properties were investigated, and meanwhile, the in-plane magnetoelectric（ME） coupling effects of the films were reported and studied for the first time in this work. Structural characterization by X-ray diffraction and scanning electron microscopy showed that both BiFeO3 and Bi（0.9）（La/Nd）（0.1）FeO3 exhabited a rhombohedral structure with（111） preferred orientation. The results of the physical properties indicated that the introduction of rare earth ions improved significantly the polarization, magnetization and dielectric properties than the undoped BiFeO3 crystals, and it enhanced effectively the in-plane ME coupling（the ME coupling coefficient αE increased from 0.13 in the pure BiFeO3 to 0.21 in Bi（0.9）La（0.1）FeO3 and 0.34 V/（Oe·cm） in Bi（0.9）Nd（0.1）FeO3）. The mechanism of these phenomena was investigated systematically.
基金supported by the National Basic Research Program of China (973) (2007CB31407)Foundation for Innovative Research Groups of the NSFC (60721001)+1 种基金the Young Fund of Sichuan Province (08ZQ026-013)the National Natural Science Foundation of China (50972023, 50872078)
文摘Ca1-xRxCu3Ti4O12(R=La,Y,Gd;x=0,0.1,0.2,0.3) electronic ceramics were fabricated by conventional solid-state reaction method.The microstructure and dielectric properties as well as impedance behavior were carefully investigated.XRD results showed that the secondary phases with the general formula R2Ti2O7 existed at grain boundaries of rare earth doped ceramics,which inhibited abnormal grain growth.The dielectric constant decreased from 4×105 in pure CaCu3Ti4O12(CCTO) ceramics to 2×103 with rare earth doping....
基金financially supported by the National Natural Science Foundation of China(No.51777138)the Natural Science Foundation of Tianjin City(Nos.18JCZDJC99700,18JCYBJC87400 and 18JCQNJC73900)the Scientific Developing Foundation of Tianjin Education Commission(No.2018KJ130)。
文摘In this work,15 types of rare earth(Re)ions,including Y^(3+),La^(3+),Ce^(3+),Pr^(3+),Nd^(3+),Sm^(3+),Eu^(3+),Gd^(3+),Tb^(3+),Dy^(3+),Ho^(3+),Er^(3+),Tm^(3+),Yb^(3+)and Lu^(3+)doped perovskite SrTiO_(3)powders were synthesized by solgel method.The influence of Re ions doping on the crystal structure,morphology and optical property as well as the photocatalytic activity for the photodegradation of rhodamine B(RhB)was investigated in detail when the synthesized Re ions doped SrTiO_(3)powders were served as catalysts.The presented results revealed that the crystal structure is invariable,whereas the morphology and the optical bandgap are variable for the resultant SrTiO_(3)powders when different Re ions were incorporated into the SrTiO_(3)lattice.The relatedness between the morphology,optical property and photocatalytic activity of the synthesized SrTiO_(3)catalysts doped with variable Re ions were analyzed deeply,providing an insight into the influence factors on the photocatalytic activity of catalysts.
基金Project supported by the National Natural Science Foundation of China(211717921401218)+4 种基金the Excellent Youth Foundation of Henan Scientific Committee(134100510018)Program for Innovative Research Team(in Science and Technology)in University of Henan Province(14IRTSTHN009)Henan Province Key Discipline of Applied Chemistry(201218692)Innovation Scientists and Technicians Troop Construction Projects of Henan Province(2013259)Key Project of Henan Education Committee(13B150102)
文摘Undoped and rare earth ions （Eu3＋, Ce3＋, Tb3＋） doped β-SrHPO4 nanomaterials were successfully prepared by a facile hydrothermal method. The crystal structure, morphology and luminescent properties were characterized by X-ray powder diffraction （XRD）, scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, photoluminescence （PL） spectra and lumi- nescence decay curves. The results indicated that the tmdoped and rare earth ions doped SrHPO4 nanomaterials （the doping concen- tration was not above 7%） were well crystallized, with the same crystal structure （^-SrHPO4）. Nevertheless, the doping of rare earth ions could lead to the changing of morphology from nanoflakes to nanocrystals. Under the excitation of UV light, rare earth ions （Eu3＋, Ce3＋, Tb3＋） doped I3-SrHPO4 nanocrystals exhibited the characteristic emission of Eu3＋, Ce3＋ and Tb3＋ ions, respectively. The luminescence decay curves of [3-SrHPO4：Eu3＋ and D-SrHPO4：Ce3＋,Th3＋ nanocrystals conformed to the double exponential fluores- cence decay, and the average lifetimes were 1.14 and 4.12 ms, respectively. The luminescence decay curve of 13-SrHPO4：Ce3＋ was fitted into a single exponential function, and the lifetime was about 0.78 ns.
基金Technology Innovation Foundation Project for Outstanding Youth of Hebei Uninversity of Technology for financial support
文摘LiFe0.99RE0.01PO4/C cathode material was synthesized by solid-state reaction method using FeC2O4-2H2O, Li2CO3, NH4H2PO4, RE（NO3）3·nH2O as raw materials and glucose as a carbon source. The doping effects of rare earth ions, such as La3＋, Ce3＋, Nd3＋, on the structure and electrochemical properties of LiFePO4/C cathode material were systematically investigated. The as-prepared samples were characterized by means of X-ray diffraction （XRD）, scanning electron microscopy （SEM） and particle size analysis. The electrochemical properties were investigated in terms of constant-current charge/discharge cycling tests. The XRD results showed that the rare earth ions doping did not change the olivine structure of LiFePO4, and all the doped samples were of single-phase with high crystallinity. SEM and particle size analysis results showed that the doping of La3＋, Ce3＋ and Nds＋ led to the decrease of particle size. The electrochemical results exhibited that the doping of La3＋ and Ce3＋ could improve the high-rate capability of LiFePO4/C cathode material, among which, the material doped with 1% Ce3＋ exhibited the optimal electrochemical properties, whose specific discharge capacities could reach 128.9, 119.5 and 104.4 mAh/g at 1C, 2C and 5C rates, respectively.
基金Project supported by the National Natural Science Foundation of China(U1830104,61635012,61925508)CAS Interdisciplinary Innovation Team,National Key Research and Development Program of China(2016YFB0402101)+1 种基金Strategic Priority Program of Chinese Academy of Science(XDB16030000)Development of Science and Technology foundation of China Academy of Engineering and Physics(2019HEL05-2).
文摘Ytterbium and rare earth ions(RE=Y,Gd,La)codoped CaF_(2)-SrF_(2)single crystals(3 at%Yb,6 at%RE:CaF_(2)-SrF_(2))were fabricated by temperature gradient technology(TGT).All the space groups remain the same Fm3m as that of Yb:CaF_(2)-SrF_(2).The lattice parameter a,unit cell volume V,as well as bond length of Ca/Sr-F and F-F increase in the sequence of rare-earth ions radius Y^(3+)<Gd^(3+)<La^(3+).The segregation coefficients of Yb ions are 0.87 in Yb,La:CaF_(2)-SrF_(2)and Yb,Gd:CaF_(2)-SrF_(2),which are larger than 0.85 in Yb,Y:CaF_(2)-SrF_(2)and 0.80 in Yb:CaF_(2)-SrF_(2).Absorption spectra in the range of 200 and 400 nm were analysed with Yb^(2+)contents.The absorption and emission cross-sections in the range of 900-1100 nm were determined together with fluorescence lifetime.The saturation pump density/Sat,minimum pump density/m in and gain cross-section were analysed.Yb,La:CaF_(2)-SrF_(2)has a relatively higher optical parameter(δem×t,0.52×10^(20)cm^(2)·ms),lower Isat(3.68 kW/cm^(2))and^min(0.50 kW/cm^(2))at 1038 nm indicating the potential application in high power laser.Low phonon energy of CaF_(2)-SrF_(2)is 302 cm^(-1)which is located between those of CaF_(2)and SrF_(2)as measured by Raman spectra.It is believed that ytterbium and rare earth ions(RE=Y^(3+),Cd^(3+),La^(3+))codoped CaF_(2)-SrF_(2)eutectic solid-solution is promising for high-power and wavelength-tunable solid-state lasers.
