The detrimental“shuttle effect”of lithium polysulfides(LiPSs)together with sluggish multi-order reaction kinetics are the main drawbacks hindering lithium-sulfur(Li-S)batteries from commercial success.Here,we first ...The detrimental“shuttle effect”of lithium polysulfides(LiPSs)together with sluggish multi-order reaction kinetics are the main drawbacks hindering lithium-sulfur(Li-S)batteries from commercial success.Here,we first propose the implementability of layered rare-earth hydroxides(LREHs)in Li-S batteries to optimize electrochemical performance.In this work,a two-dimensional(2D)rare-earth-based composite constructed by the layered gadolinium hydroxy chloride[Gd_(2)(OH)_(5)(H_(2)O)_(n)]Cl nanoplates(LGdH NPs)and graphene oxide(GO)was designed as a sulfur immobilizer for Li-S batteries.Combining the experimental results and density functional theory(DFT)calculations,it is revealed that the LGdH@GO composite not only provides a strong anchoring of the intermediates during cycling,but also acts as an effective catalyst to accelerate the liquid-solid conversion of polysulfides.The Li-S batteries assembled by LGdH@GO modified separators delivered a superior rate performance with a specific capacity of 605.34 mAh/g at 5 C,as well as excellent cycle stability with a decay rate of 0.087%over 500 cycles at 2 C.This study provided a deep understanding of the mechanism to suppress the“shuttle effect”by the LREHs,and a guide to design effective functional interlayers for high-performance Li-S batteries with excellent electrocatalytic activity.展开更多
This review article compiles the recent achievements made in layered rare-earth (RE) hydroxide (LRH), including controlled crystallization, structural and morphological features, anion exchange, nanosheet exfoliation,...This review article compiles the recent achievements made in layered rare-earth (RE) hydroxide (LRH), including controlled crystallization, structural and morphological features, anion exchange, nanosheet exfoliation, and application in the field of luminescence for both the Ln2(OH)5(Ax-)1/x·nH2O (251-LRH) and Ln2(OH)4(Ax-)2/x·nH2O (241-LRH) phases. The luminescent properties of the LRHs themselves, the oxide, oxysulfate, and oxysulfide phosphors derived from the LRHs via controlled calcination, and the highly oriented transparent phosphor films of enhanced luminescence and/or novel emission features are summarized.展开更多
We highlighted the flexibility of using unstructured mesh together with the local refinement by a resistivity model with complicated topography. The effect of topography is emphasized. Based on this, we calculated a s...We highlighted the flexibility of using unstructured mesh together with the local refinement by a resistivity model with complicated topography. The effect of topography is emphasized. Based on this, we calculated a specific class of layered models and found that the accuracy is not always satisfactory by utilizing the standard approach. As an improvement, we employed the layered earth as the reference model to calculate the wavenumbers. The comparison demonstrates that the accuracy is considerably improved by using this enhanced approach.展开更多
The design and fabrication of rare earth ions incorporated into the inorganic/organic hybrid materials have attracted growing attention for seeking improved optical properties and photofunctional performances.In this ...The design and fabrication of rare earth ions incorporated into the inorganic/organic hybrid materials have attracted growing attention for seeking improved optical properties and photofunctional performances.In this paper,a novel hybrid composite based on the layered rare earth hydroxides was successfully prepared by the ion-exchange and intercalation chemical process.The rare earth elements in the composite contain gadolinium(Gd)and europium(Eu)and the molar ratio of Gd to Eu is kept constant at 1.9:0.1.Organic sodium dodecyl sulfonate and dye coumarin-3-carboxyllc acid are simultaneously incorporated into the layered rare earth hydroxides as supporting agent and light-harvesting antenna,respectively.The resulting hybrid layered rare earth hydroxides exhibit the enlarged interlayer distance with about 2.60 nm,and the chemical composition was confirmed through X-ray diffraction,carbon,hydrogen and nitrogen(CHN)elemental analysis,infrared spectroscopy,and thermogravimetric analysis.The layered solid compound shows the characteristic red emission corresponding to the^(5)D_(0)→^(7)F_(2)transition of Eu^(3+)ion,and the luminescence intensity of the optimized compound is greatly enhanced as compared to its corresponding nitrate and the hybrid composite without the introduction of dye molecule.The hybrid layered rare earth hydroxides can be exfoliated into bright colloidal solution,which show superior recognition capability to Cu^(2+)ion with the distinct luminescence quenching.The large quenching constant(1.4×10^(4)L/mol)and low detection limit(0.35μmol/L)are achieved for Cu^(2+)ion,implying a"turn-off"fluorescent sensor for Cu^(2+)detection.Moreover,a transparent film was prepared based on the colloidal solution and displays the typical red emission in folded shape.The new hybrid compound with enhanced luminescence and excellent photofunctional performances is expected to be applied in the fields of fluorescent sensing and flexible optical devices.展开更多
This paper discusses use of approximations and the Integral Mean Value Theorem to show that 6 coefficients approximately describe the distortions of near surface inhomogeneities on the MT field of a horizontally layer...This paper discusses use of approximations and the Integral Mean Value Theorem to show that 6 coefficients approximately describe the distortions of near surface inhomogeneities on the MT field of a horizontally layered earth model. When these 6 coefficients are considered together with those of the magnetic field of a horizontally layered earth model,the analytic and approximate wave impedance equations can be derived for the MT response of a horizontally layered earth model with near-surface 2-D and 3-D inhomogeneities. These approximate wave impedance equations are used with inverted MT data for 2-D and 3-D forward modelling. Although these 6 coefficients cannot be determined before inversion,initial estimates can be used. The 6 coefficients and the asistivity and thickness of each layer of a horizontally layered earth can be obtained by using published inversion methods. The 6 coefficients give important informaion (depths and resistivities) on the near-surface inhomogenelties.The authors inverted 2-D and 3-D theoretical models for Fast Approximate Inversion of Magnetotelluric (FAIMT) data for a horizontally layered earth with near-surface inhomogeneities compares favorably with traditional invrsion methods, especially for inverting regional or basin structures. This method simplifies computation and gives a reasonable 1 -D geological model with fewer nonuniquenas problems.展开更多
The rational design of photocatalyst that can effectively reduce CO_(2) under visible light(l>400 nm),and simultaneously precise control of the products syngas(CO/H2)ratio is highly desirable for the Fischer-Tropsc...The rational design of photocatalyst that can effectively reduce CO_(2) under visible light(l>400 nm),and simultaneously precise control of the products syngas(CO/H2)ratio is highly desirable for the Fischer-Tropsch reaction.In this work,we synthesized a series of CeO_(2)-decorated layered double hydroxides(LDHs,Ce-x)samples for photocatalytic CO_(2) reduction.It was found that the selectivity and productivity of CO and H_(2) from photoreduction of CO_(2) in conjunction with Ru-complex as photosensitizer performed an obvious“volcano-like”trend,with the highest point at Ce-0.15 and the CO/H_(2) ratio can be widely tunable from 1/7.7 to 1/1.3.Furthermore,compared with LDH,Ce-0.15 also drove photocatalytic CO_(2) to syngas under 600 nm irradiation.It implied that an optimum amount of CeO_(2) modifying LDH promoted the photoreduction of CO_(2) to syngas.This report gives the way to fully utilize the rare earth elements and provides a promising route to enhance the photo-response ability and charge injection efficiency of LDH-based photocatalysts in the synthesis of syngas with a tunable ratio under visible light irradiation.展开更多
A switched-mode unit used in electric locomotive generates a strong high frequency conducted electromagnetic interference (EMI),which radiates electromagnetic energy through railway lines.Evaluation of magnetic field ...A switched-mode unit used in electric locomotive generates a strong high frequency conducted electromagnetic interference (EMI),which radiates electromagnetic energy through railway lines.Evaluation of magnetic field using analytical technique based on contour integral is presented,in order to assess the electromagnetic environment around a high-speed railway.Actual railway multiconductor finitely long overhead lines are represented by an infinitely long single line above two-layered earth,whose characteristic is different from homogeneous earth.Owing to the constraint of the GB/T 24338-2009 and the high frequency investigated (a few MHz),only the magnetic fields are examined.The magnetic fields consist of four components:the direct wave,the ideal reflected wave or image wave,the trapped surface wave,and the lateral wave.The calculation results proved that due to the presence of the trapped surface wave,the magnetic field of the observer point on the interface is strongly influenced,when the line is on or closed to the interface.展开更多
We demonstrate the fabrication of a novel magnetic nanohybrid involving the drug molecule 5 aminolevulinic acid(5-ALA)intercalated Gd-Eu layered rare-earth hydroxide(LRH)coated on magnesium ferrite particles(MgFe2O4)....We demonstrate the fabrication of a novel magnetic nanohybrid involving the drug molecule 5 aminolevulinic acid(5-ALA)intercalated Gd-Eu layered rare-earth hydroxide(LRH)coated on magnesium ferrite particles(MgFe2O4).The structure,thermostability,morphology,luminescence properties,cytotoxic effect and magnetism are investigated.The 5-ALA intercalated composite may correspond to a monolayered vertical arrangement,and the thermal stability of organics is enhanced after intercalation.The LRH precursor shows red emission of Eu^3+and the maximum emission peak of the composite is at 451 nm,corresponding to the blue emission.The detection of drug molecules can be realized through the change of luminescence.The magnetic nanohybrid shows strong magnetic sensitivity,which provides an easy and efficient way to separate 5-ALA-MgFe2O4@LGd0.95H:Eu0.05 particles from a sol or a suspension system and to carry drugs to targeted locations under an external magnetic field.The cytotoxic effect of MgFe2O4@LRH is observed with a sulforhodamine B(SRB)colorimetric assay,which has low cytotoxic effects on selected cells.The fabrication of novel bifunctional drug carriers based on LRH with magnetic and fluorescent properties has potential applications in drug detection and drug delivery.展开更多
基金supported by National Science Foundation for Youths of China(Nos.22209184 and 22109163)。
文摘The detrimental“shuttle effect”of lithium polysulfides(LiPSs)together with sluggish multi-order reaction kinetics are the main drawbacks hindering lithium-sulfur(Li-S)batteries from commercial success.Here,we first propose the implementability of layered rare-earth hydroxides(LREHs)in Li-S batteries to optimize electrochemical performance.In this work,a two-dimensional(2D)rare-earth-based composite constructed by the layered gadolinium hydroxy chloride[Gd_(2)(OH)_(5)(H_(2)O)_(n)]Cl nanoplates(LGdH NPs)and graphene oxide(GO)was designed as a sulfur immobilizer for Li-S batteries.Combining the experimental results and density functional theory(DFT)calculations,it is revealed that the LGdH@GO composite not only provides a strong anchoring of the intermediates during cycling,but also acts as an effective catalyst to accelerate the liquid-solid conversion of polysulfides.The Li-S batteries assembled by LGdH@GO modified separators delivered a superior rate performance with a specific capacity of 605.34 mAh/g at 5 C,as well as excellent cycle stability with a decay rate of 0.087%over 500 cycles at 2 C.This study provided a deep understanding of the mechanism to suppress the“shuttle effect”by the LREHs,and a guide to design effective functional interlayers for high-performance Li-S batteries with excellent electrocatalytic activity.
基金This work was supported in part by the National Natural Science Foundation of China，the Fundamental Research Funds for the Central Universities
文摘This review article compiles the recent achievements made in layered rare-earth (RE) hydroxide (LRH), including controlled crystallization, structural and morphological features, anion exchange, nanosheet exfoliation, and application in the field of luminescence for both the Ln2(OH)5(Ax-)1/x·nH2O (251-LRH) and Ln2(OH)4(Ax-)2/x·nH2O (241-LRH) phases. The luminescent properties of the LRHs themselves, the oxide, oxysulfate, and oxysulfide phosphors derived from the LRHs via controlled calcination, and the highly oriented transparent phosphor films of enhanced luminescence and/or novel emission features are summarized.
基金supported by the National High Technology Research and Development Program of China (863 Program) (No. 2007AA06Z134)the National Natural Science Foundation of China (No. 40874072)
文摘We highlighted the flexibility of using unstructured mesh together with the local refinement by a resistivity model with complicated topography. The effect of topography is emphasized. Based on this, we calculated a specific class of layered models and found that the accuracy is not always satisfactory by utilizing the standard approach. As an improvement, we employed the layered earth as the reference model to calculate the wavenumbers. The comparison demonstrates that the accuracy is considerably improved by using this enhanced approach.
基金Project supported by the National Natural Science Foundation of China(51972097)。
文摘The design and fabrication of rare earth ions incorporated into the inorganic/organic hybrid materials have attracted growing attention for seeking improved optical properties and photofunctional performances.In this paper,a novel hybrid composite based on the layered rare earth hydroxides was successfully prepared by the ion-exchange and intercalation chemical process.The rare earth elements in the composite contain gadolinium(Gd)and europium(Eu)and the molar ratio of Gd to Eu is kept constant at 1.9:0.1.Organic sodium dodecyl sulfonate and dye coumarin-3-carboxyllc acid are simultaneously incorporated into the layered rare earth hydroxides as supporting agent and light-harvesting antenna,respectively.The resulting hybrid layered rare earth hydroxides exhibit the enlarged interlayer distance with about 2.60 nm,and the chemical composition was confirmed through X-ray diffraction,carbon,hydrogen and nitrogen(CHN)elemental analysis,infrared spectroscopy,and thermogravimetric analysis.The layered solid compound shows the characteristic red emission corresponding to the^(5)D_(0)→^(7)F_(2)transition of Eu^(3+)ion,and the luminescence intensity of the optimized compound is greatly enhanced as compared to its corresponding nitrate and the hybrid composite without the introduction of dye molecule.The hybrid layered rare earth hydroxides can be exfoliated into bright colloidal solution,which show superior recognition capability to Cu^(2+)ion with the distinct luminescence quenching.The large quenching constant(1.4×10^(4)L/mol)and low detection limit(0.35μmol/L)are achieved for Cu^(2+)ion,implying a"turn-off"fluorescent sensor for Cu^(2+)detection.Moreover,a transparent film was prepared based on the colloidal solution and displays the typical red emission in folded shape.The new hybrid compound with enhanced luminescence and excellent photofunctional performances is expected to be applied in the fields of fluorescent sensing and flexible optical devices.
文摘This paper discusses use of approximations and the Integral Mean Value Theorem to show that 6 coefficients approximately describe the distortions of near surface inhomogeneities on the MT field of a horizontally layered earth model. When these 6 coefficients are considered together with those of the magnetic field of a horizontally layered earth model,the analytic and approximate wave impedance equations can be derived for the MT response of a horizontally layered earth model with near-surface 2-D and 3-D inhomogeneities. These approximate wave impedance equations are used with inverted MT data for 2-D and 3-D forward modelling. Although these 6 coefficients cannot be determined before inversion,initial estimates can be used. The 6 coefficients and the asistivity and thickness of each layer of a horizontally layered earth can be obtained by using published inversion methods. The 6 coefficients give important informaion (depths and resistivities) on the near-surface inhomogenelties.The authors inverted 2-D and 3-D theoretical models for Fast Approximate Inversion of Magnetotelluric (FAIMT) data for a horizontally layered earth with near-surface inhomogeneities compares favorably with traditional invrsion methods, especially for inverting regional or basin structures. This method simplifies computation and gives a reasonable 1 -D geological model with fewer nonuniquenas problems.
基金This research was supported by the National Natural Science Foundation of China(Grant Nos.U1707603,21878008,21625101,U1507102,21922801)Beijing Natural Science Foundation(Nos.2182047,2202036)the Fundamental Research Funds for the Central Universities(Nos.XK1802-6,XK1902,12060093063,2312018RC07).
文摘The rational design of photocatalyst that can effectively reduce CO_(2) under visible light(l>400 nm),and simultaneously precise control of the products syngas(CO/H2)ratio is highly desirable for the Fischer-Tropsch reaction.In this work,we synthesized a series of CeO_(2)-decorated layered double hydroxides(LDHs,Ce-x)samples for photocatalytic CO_(2) reduction.It was found that the selectivity and productivity of CO and H_(2) from photoreduction of CO_(2) in conjunction with Ru-complex as photosensitizer performed an obvious“volcano-like”trend,with the highest point at Ce-0.15 and the CO/H_(2) ratio can be widely tunable from 1/7.7 to 1/1.3.Furthermore,compared with LDH,Ce-0.15 also drove photocatalytic CO_(2) to syngas under 600 nm irradiation.It implied that an optimum amount of CeO_(2) modifying LDH promoted the photoreduction of CO_(2) to syngas.This report gives the way to fully utilize the rare earth elements and provides a promising route to enhance the photo-response ability and charge injection efficiency of LDH-based photocatalysts in the synthesis of syngas with a tunable ratio under visible light irradiation.
基金Project supported by the National Natural Science Foundation of China(Nos.50877070 and 51105331)the Technological Research and Development Programs of the Ministry of Chinese Railways(Nos.2009J006-L and 2010J011-E)
文摘A switched-mode unit used in electric locomotive generates a strong high frequency conducted electromagnetic interference (EMI),which radiates electromagnetic energy through railway lines.Evaluation of magnetic field using analytical technique based on contour integral is presented,in order to assess the electromagnetic environment around a high-speed railway.Actual railway multiconductor finitely long overhead lines are represented by an infinitely long single line above two-layered earth,whose characteristic is different from homogeneous earth.Owing to the constraint of the GB/T 24338-2009 and the high frequency investigated (a few MHz),only the magnetic fields are examined.The magnetic fields consist of four components:the direct wave,the ideal reflected wave or image wave,the trapped surface wave,and the lateral wave.The calculation results proved that due to the presence of the trapped surface wave,the magnetic field of the observer point on the interface is strongly influenced,when the line is on or closed to the interface.
基金supported by the Youth Top-notch Talent Training Program for Universities and Colleges under Beijing Municipality(CIT&TCD201804035)the National Natural Science Foun-dation of China(Grant No.21601016)+1 种基金the Project of Construction of Innovative Teams and Teacher Career Development for Universities and Colleges under Beiing Municipality(IDHT20180508)the Construc-tion of Scientific Research Platform(2018XK002).
文摘We demonstrate the fabrication of a novel magnetic nanohybrid involving the drug molecule 5 aminolevulinic acid(5-ALA)intercalated Gd-Eu layered rare-earth hydroxide(LRH)coated on magnesium ferrite particles(MgFe2O4).The structure,thermostability,morphology,luminescence properties,cytotoxic effect and magnetism are investigated.The 5-ALA intercalated composite may correspond to a monolayered vertical arrangement,and the thermal stability of organics is enhanced after intercalation.The LRH precursor shows red emission of Eu^3+and the maximum emission peak of the composite is at 451 nm,corresponding to the blue emission.The detection of drug molecules can be realized through the change of luminescence.The magnetic nanohybrid shows strong magnetic sensitivity,which provides an easy and efficient way to separate 5-ALA-MgFe2O4@LGd0.95H:Eu0.05 particles from a sol or a suspension system and to carry drugs to targeted locations under an external magnetic field.The cytotoxic effect of MgFe2O4@LRH is observed with a sulforhodamine B(SRB)colorimetric assay,which has low cytotoxic effects on selected cells.The fabrication of novel bifunctional drug carriers based on LRH with magnetic and fluorescent properties has potential applications in drug detection and drug delivery.
