Showing papers on "Ion published in 2013"
TL;DR: Various fundamental studies that have been conducted to understand structural and volumetric changes, stress evolution, mechanical properties, and fracture behavior of nanostructured Si anodes for lithium-ion batteries are reviewed and the reaction process of Si is compared to other novel anode materials.
Abstract: Alloying anodes such as silicon are promising electrode materials for next-generation high energy density lithium-ion batteries because of their ability to reversibly incorporate a high concentration of Li atoms. However, alloying anodes usually exhibit a short cycle life due to the extreme volumetric and structural changes that occur during lithium insertion/extraction; these transformations cause mechanical fracture and exacerbate side reactions. To solve these problems, there has recently been significant attention devoted to creating silicon nanostructures that can accommodate the lithiation-induced strain and thus exhibit high Coulombic efficiency and long cycle life. In parallel, many experiments and simulations have been conducted in an effort to understand the details of volumetric expansion, fracture, mechanical stress evolution, and structural changes in silicon nanostructures. The fundamental materials knowledge gained from these studies has provided guidance for designing optimized Si electrode structures and has also shed light on the factors that control large-volume change solid-state reactions. In this paper, we review various fundamental studies that have been conducted to understand structural and volumetric changes, stress evolution, mechanical properties, and fracture behavior of nanostructured Si anodes for lithium-ion batteries and compare the reaction process of Si to other novel anode materials.
1,134 citations
01 Sep 2013-Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms
TL;DR: The SRIM (formerly TRIM) Monte Carlo simulation code is widely used to compute a number of parameters relevant to ion beam implantation and ion beam processing of materials as discussed by the authors.
Abstract: The SRIM (formerly TRIM) Monte Carlo simulation code is widely used to compute a number of parameters relevant to ion beam implantation and ion beam processing of materials. It also has the capability to compute a common radiation damage exposure unit known as atomic displacements per atom (dpa). Since dpa is a standard measure of primary radiation damage production, most researchers who employ ion beams as a tool for inducing radiation damage in materials use SRIM to determine the dpa associated with their irradiations. The use of SRIM for this purpose has been evaluated and comparisons have been made with an internationally-recognized standard definition of dpa, as well as more detailed atomistic simulations of atomic displacement cascades. Differences between the standard and SRIM-based dpa are discussed and recommendations for future usage of SRIM in radiation damage studies are made. In particular, it is recommended that when direct comparisons between ion and neutron data are intended, the Kinchin–Pease option of SRIM should be selected.
1,097 citations
TL;DR: This work investigates effects of anion vacancies in monolayer transition metal dichalcogenides as two-dimensional (2D) semiconductors where the vacancies density is controlled by α-particle irradiation or thermal-annealing and finds a new, sub-bandgap emission peak as well as increase in overall photoluminescence intensity as a result of the vacancy generation.
Abstract: Point defects in semiconductors can trap free charge carriers and localize excitons. The interaction between these defects and charge carriers becomes stronger at reduced dimensionalities, and is expected to greatly influence physical properties of the hosting material. We investigated effects of anion vacancies in monolayer transition metal dichalcogenides as two-dimensional (2D) semiconductors where the vacancies density is controlled bya-particle irradiation or thermal-annealing. We found a new, sub-bandgap emission peak as well as increase in overall photoluminescence intensity as a result of the vacancy generation. Interestingly, these effects are absent when measured in vacuum. We conclude that in opposite to conventional wisdom, optical quality at room temperature cannot be used as criteria to assess crystal quality of the 2D semiconductors. Our results not only shed light on defect and exciton physics of 2D semiconductors, but also offer a new route toward tailoring optical properties of 2D semiconductors by defect engineering.
940 citations
TL;DR: This work systematically designed LJ parameters for 24 +2 metal (M(II) cations to reproduce different experimental properties appropriate for the Lorentz-Berthelot combining rules and PME simulations to represent the best possible compromise that can be achieved using the nonbonded model for the ions in combination with simple water models.
Abstract: Metal ions play significant roles in biological systems. Accurate molecular dynamics (MD) simulations on these systems require a validated set of parameters. Although there are more detailed ways to model metal ions, the nonbonded model, which employs a 12–6 Lennard-Jones (LJ) term plus an electrostatic potential, is still widely used in MD simulations today due to its simple form. However, LJ parameters have limited transferability due to different combining rules, various water models, and diverse simulation methods. Recently, simulations employing a Particle Mesh Ewald (PME) treatment for long-range electrostatics have become more and more popular owing to their speed and accuracy. In the present work, we have systematically designed LJ parameters for 24 +2 metal (M(II)) cations to reproduce different experimental properties appropriate for the Lorentz–Berthelot combining rules and PME simulations. We began by testing the transferability of currently available M(II) ion LJ parameters. The results showe...
499 citations
TL;DR: In this article, three metal-organic frameworks (MOFs) of the UiO-68 network topology were prepared using the amino-TPDC or TPDC bridging ligands containing orthogonal phosphorylurea groups, and investigated for sorption of uranium from water and artificial seawater.
Abstract: Three metal–organic frameworks (MOFs) of the UiO-68 network topology were prepared using the amino-TPDC or TPDC bridging ligands containing orthogonal phosphorylurea groups (TPDC is p,p′-terphenyldicarboxylic acid), and investigated for sorption of uranium from water and artificial seawater. The stable and porous phosphorylurea-derived MOFs were shown to be highly efficient in sorbing uranyl ions, with saturation sorption capacities as high as 217 mg U g−1 which is equivalent to binding one uranyl ion for every two sorbent groups. Coordination modes between uranyl groups and simplified phosphorylurea motifs were investigated by DFT calculations, revealing a thermodynamically favorable monodentate binding of two phosphorylurea ligands to one uranyl ion. Convergent orientation of phosphorylurea groups at appropriate distances inside the MOF cavities is believed to facilitate their cooperative binding with uranyl ions. This work represents the first application of MOFs as novel sorbents to extract actinide elements from aqueous media.
484 citations
TL;DR: Inspired by the natural microalgae with its special features, this work develops a green and facile biotemplating method to fabricate monodisperse MnO/C microspheres for lithium-ion batteries, which will extend the scope of biOTemplating synthesis for exploring other functional materials in various structure-dependent applications such as catalysis, gas sensing, and energy storage.
Abstract: Hollow porous micro/nanostructures with high surface area and shell permeability have attracted tremendous attention. Particularly, the synthesis and structural tailoring of diverse hollow porous materials is regarded as a crucial step toward the realization of high-performance electrode materials, which has several advantages including a large contact area with electrolyte, a superior structural stability, and a short transport path for Li+ ions. Meanwhile, owing to the inexpensive, abundant, environmentally benign, and renewable biological resources provided by nature, great efforts have been devoted to understand and practice the biotemplating technology, which has been considered as an effective strategy to achieve morphology-controllable materials with structural specialty, complexity, and related unique properties. Herein, we are inspired by the natural microalgae with its special features (easy availability, biological activity, and carbon sources) to develop a green and facile biotemplating method...
483 citations
TL;DR: In this paper, the capacity of nano-sized Na2Ti3O7 was investigated from both thermodynamic and kinetic aspects, and a zero-current overpotential related to thermodynamic factors was observed for both nano-and micro-sized nano-nodes.
Abstract: Layered sodium titanium oxide, Na2Ti3O7, is synthesized by a solid-state reaction method as a potential anode for sodium-ion batteries. Through optimization of the electrolyte and binder, the microsized Na2Ti3O7 electrode delivers a reversible capacity of 188 mA h g(-1) in 1 M NaFSI/PC electrolyte at a current rate of 0.1C in a voltage range of 0.0-3.0 V, with sodium alginate as binder. The average Na storage voltage plateau is found at ca. 0.3 V vs. Na+/Na, in good agreement with a first-principles prediction of 0.35 V. The Na storage properties in Na2Ti3O7 are investigated from thermodynamic and kinetic aspects. By reducing particle size, the nanosized Na2Ti3O7 exhibits much higher capacity, but still with unsatisfied cyclic properties. The solid-state interphase layer on Na2Ti3O7 electrode is analyzed. A zero-current overpotential related to thermodynamic factors is observed for both nano- and microsized Na2Ti3O7. The electronic structure, Na+ ion transport and conductivity are investigated by the combination of first-principles calculation and electrochemical characterizations. On the basis of the vacancy-hopping mechanism, a quasi-3D energy favorable trajectory is proposed for Na2Ti3O7. The Na+ ions diffuse between the TiO6 octahedron layers with pretty low activation energy of 0.186 eV.
447 citations
440 citations
TL;DR: By a novel in situ chemical vapor deposition, activated N-doped hollow carbon-nanotube/carbon-nanofiber composites are prepared having a superhigh specific Brunauer–Emmett–Teller (BET) surface area and total pore volume, which makes it a superior anode material for a Li-ion battery.
Abstract: By a novel in situ chemical vapor deposition, activated N-doped hollow carbon-nanotube/carbon-nanofiber composites are prepared having a superhigh specific Brunauer–Emmett–Teller (BET) surface area of 1840 m(2) g(–1) and a total pore volume of 121 m(3) g(–1) As an anode, this material has a reversible capacity of ~1150 mAh g(–1) at 01 A g(–1) (027 C) after 70 cycles At 8 A g(–1) (215 C), a capacity of ~320 mAh g(–1) fades less than 20% after 3500 cycles, which makes it a superior anode material for a Li-ion battery
407 citations
TL;DR: In this article, the EPR and temperature-programmed reduction (TPR) results were used to identify the locations of the Cu2+ ion locations and the reaction kinetics of the NH3-SCR reaction.
397 citations
TL;DR: LiMnPO4 cathodes have been investigated in both native and substituted forms along with carbon coating synthesized by various synthetic techniques as mentioned in this paper, and the results are compared with previous literature values.
Abstract: Development of an eco-friendly, low cost and high energy density (∼700 W h kg−1) LiMnPO4 cathode material became attractive due to its high operating voltage ∼4.1 V vs. Li falling within the electrochemical stability window of conventional electrolyte solutions and offers more safety features due to the presence of a strong P–O covalent bond. The vacancy formation energy for LiMnPO4 was 0.19 eV higher than that for LiFePO4, resulting in a 10−3 times-diluted complex concentration, which represents the main difference between the kinetics in the initial stage of charging of two olivine materials. This review highlights the overview of current research activities on LiMnPO4 cathodes in both native and substituted forms along with carbon coating synthesized by various synthetic techniques. Further, carbon coated LiMnPO4 was also prepared by a solid-state approach and the obtained results are compared with previous literature values. The challenges and the need for further research to realize the full performance of LiMnPO4 cathodes are described in detail.
TL;DR: The results indicate that ionic liquids screen charged surfaces through the formation of both bound (Stern) and diffuse electric double layers, where the diffuse double layer is comprised of effectively dissociated ionic liquid ions.
Abstract: We combine direct surface force measurements with thermodynamic arguments to demonstrate that pure ionic liquids are expected to behave as dilute weak electrolyte solutions, with typical effective dissociated ion concentrations of less than 0.1% at room temperature. We performed equilibrium force–distance measurements across the common ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([C4mim][NTf2]) using a surface forces apparatus with in situ electrochemical control and quantitatively modeled these measurements using the van der Waals and electrostatic double-layer forces of the Derjaguin–Landau–Verwey–Overbeek theory with an additive repulsive steric (entropic) ion–surface binding force. Our results indicate that ionic liquids screen charged surfaces through the formation of both bound (Stern) and diffuse electric double layers, where the diffuse double layer is comprised of effectively dissociated ionic liquid ions. Additionally, we used the energetics of thermally dissociating ions in a dielectric medium to quantitatively predict the equilibrium for the effective dissociation reaction of [C4mim][NTf2] ions, in excellent agreement with the measured Debye length. Our results clearly demonstrate that, outside of the bound double layer, most of the ions in [C4mim][NTf2] are not effectively dissociated and thus do not contribute to electrostatic screening. We also provide a general, molecular-scale framework for designing ionic liquids with significantly increased dissociated charge densities via judiciously balancing ion pair interactions with bulk dielectric properties. Our results clear up several inconsistencies that have hampered scientific progress in this important area and guide the rational design of unique, high–free-ion density ionic liquids and ionic liquid blends.
TL;DR: In this paper, a high performance graphene oxide-doped ion gel (P(VDF-HFP)-EMIMBF4-GO gel) is prepared by exploiting copolymer (poly(vinylidene fluoride-hexafluoro propylene), P(HFP)) as the polymer matrix, ionic liquid (1-ethyl-3-methylimidazolium tetrafluoroborate, EMIMBF 4) as the supporting electrolyte, and GO as the ionic conducting promoter.
Abstract: A high-performance graphene oxide (GO)-doped ion gel (P(VDF-HFP)-EMIMBF4-GO gel) is prepared by exploiting copolymer (poly(vinylidene fluoride-hexafluoro propylene), P(VDF-HFP)) as the polymer matrix, ionic liquid (1-ethyl-3-methylimidazolium tetrafluoroborate, EMIMBF4) as the supporting electrolyte, and GO as the ionic conducting promoter. This GO-doped ion gel demonstrates significantly improved ionic conductivity compared with that of pure ion gel without the addition of GO, due to the homogeneously distributed GO as a 3D network throughout the GO-doped ion gel by acting like a ion “highway” to facilitate the ion transport. With the incorporation of only a small amount of GO (1 wt%) in ion gel, there has been a dramatic improvement in ionic conductivity of about 260% compared with that of pure ion gel. In addition, the all-solid-state supercapacitor is fabricated and measured at room temperature using the GO-doped ion gel as gel polymer electrolyte, which demonstrates more superior electrochemical performance than the all-solid-state supercapacitor with pure ion gel and the conventional supercapacitor with neat EMIMBF4, in the aspect of smaller internal resistance, higher capacitance performance, and better cycle stability. These excellent performances are due to the high ionic conductivity, excellent compatibility with carbon electrodes, and long-term stability of the GO-doped ion gel.
TL;DR: It is shown from both simulations and experiments that zwitterion functionalized carbon nanotubes (CNTs) can be used to construct highly efficient desalination membranes and theoretical predictions indicate that an ideal CNT/polymer membrane having a loading of 20 wt % CNTs would have a maximum flux of about 20000 GFD at the conditions of the authors' experiments.
Abstract: We have shown from both simulations and experiments that zwitterion functionalized carbon nanotubes (CNTs) can be used to construct highly efficient desalination membranes. Our simulations predicted that zwitterion functional groups at the ends of CNTs allow a high flux of water, while rejecting essentially all ions. We have synthesized zwitterion functionalized CNT/polyamide nanocomposite membranes with varying loadings of CNTs and assessed these membranes for water desalination. The CNTs within the polyamide layer were partially aligned through a high-vacuum filtration step during membrane synthesis. Addition of zwitterion functionalized CNTs into a polyamide membrane increased both the flux of water and the salt rejection ratio. The flux of water was found to increase by more than a factor of 4, from 6.8 to 28.7 GFD (gallons per square foot per day), as the fraction of CNTs was increased from 0 to 20 wt %. Importantly, the ion rejection ratio increased slightly from 97.6% to 98.6%. Thus, the nanotubes ...
TL;DR: This work uses first-principles simulations to demonstrate that the currently accepted picture of proton diffusion is in need of revision, and shows that proton and hydroxide diffusion occurs through periods of intense activity involving concerted proton hopping followed by periods of rest.
Abstract: The diffusion of protons through water is understood within the framework of the Grotthuss mechanism, which requires that they undergo structural diffusion in a stepwise manner throughout the water network. Despite long study, this picture oversimplifies and neglects the complexity of the supramolecular structure of water. We use first-principles simulations and demonstrate that the currently accepted picture of proton diffusion is in need of revision. We show that proton and hydroxide diffusion occurs through periods of intense activity involving concerted proton hopping followed by periods of rest. The picture that emerges is that proton transfer is a multiscale and multidynamical process involving a broader distribution of pathways and timescales than currently assumed. To rationalize these phenomena, we look at the 3D water network as a distribution of closed directed rings, which reveals the presence of medium-range directional correlations in the liquid. One of the natural consequences of this feature is that both the hydronium and hydroxide ion are decorated with proton wires. These wires serve as conduits for long proton jumps over several hydrogen bonds.
TL;DR: It is discovered that the marine flavobacterium Krokinobacter eikastus possesses two rhodopsins, the first, KR1, being a prototypical proton pump, while the second, KR2, pumps sodium ions outward.
Abstract: Light-driven proton-pumping rhodopsins are widely distributed in many microorganisms. They convert sunlight energy into proton gradients that serve as energy source of the cell. Here we report a new functional class of a microbial rhodopsin, a light-driven sodium ion pump. We discover that the marine flavobacterium Krokinobacter eikastus possesses two rhodopsins, the first, KR1, being a prototypical proton pump, while the second, KR2, pumps sodium ions outward. Rhodopsin KR2 can also pump lithium ions, but converts to a proton pump when presented with potassium chloride or salts of larger cations. These data indicate that KR2 is a compatible sodium ion-proton pump, and spectroscopic analysis showed it binds sodium ions in its extracellular domain. These findings suggest that light-driven sodium pumps may be as important in situ as their proton-pumping counterparts.
TL;DR: In this article, the authors used 2D and 3D hybrid (kinetic ions - fluid electrons) simulations to investigate particle acceleration and magnetic field amplification at nonrelativistic astrophysical shocks.
Abstract: We use 2D and 3D hybrid (kinetic ions - fluid electrons) simulations to investigate particle acceleration and magnetic field amplification at non-relativistic astrophysical shocks. We show that diffusive shock acceleration operates for quasi-parallel configurations (i.e., when the background magnetic field is almost aligned with the shock normal) and, for large sonic and Alfv\'enic Mach numbers, produces universal power-law spectra proportional to p^(-4), where p is the particle momentum. The maximum energy of accelerated ions increases with time, and it is only limited by finite box size and run time. Acceleration is mainly efficient for parallel and quasi-parallel strong shocks, where 10-20% of the bulk kinetic energy can be converted to energetic particles, and becomes ineffective for quasi-perpendicular shocks. Also, the generation of magnetic turbulence correlates with efficient ion acceleration, and vanishes for quasi-perpendicular configurations. At very oblique shocks, ions can be accelerated via shock drift acceleration, but they only gain a factor of a few in momentum, and their maximum energy does not increase with time. These findings are consistent with the degree of polarization and the morphology of the radio and X-ray synchrotron emission observed, for instance, in the remnant of SN 1006. We also discuss the transition from thermal to non-thermal particles in the ion spectrum (supra-thermal region), and we identify two dynamical signatures peculiar of efficient particle acceleration, namely the formation of an upstream precursor and the alteration of standard shock jump conditions.
TL;DR: In this paper, the effect of replacing lattice O atoms with B, C, N, or F dopants, or to include the same atoms in interstitial positions has been considered.
TL;DR: The multi-ion selectivity filter of the CaVAb model establishes a structural framework for understanding the mechanisms of ion selectivity and conductance by vertebrate CaV channels and supports a 'knock-off' mechanism of ion permeation through a stepwise-binding process.
Abstract: Voltage-gated calcium (CaV) channels catalyse rapid, highly selective influx of Ca 21 into cells despite a 70-fold higher extracellular concentration of Na 1 .H ow CaV channels solve this fundamental biophysical problem remains unclear. Here we report physiological and crystallographic analyses of a calcium selectivity filter constructed in the homotetrameric bacterial NaV channel NaVAb. Our results reveal interactions of hydrated Ca 21 with two high-affinity Ca 21 -binding sites followed by a third lower-affinity site that would coordinate Ca 21 as it moves inward. At the selectivity filter entry, Site 1 is formed by four carboxyl side chains, which have a critical role in determining Ca 21 selectivity. Four carboxyls plus four backbone carbonyls form Site 2, which is targeted by the blocking cations Cd 21 and Mn 21 , with single occupancy. The lower-affinity Site 3 is formed by four backbone carbonyls alone, which mediate exit into the central cavity. This pore architecture suggests a conduction pathway involving transitions between two main states with one or two hydrated Ca 21 ions bound in the selectivity filter and supports a ‘knock-off’ mechanism of ion permeation through a stepwisebinding process. The multi-ion selectivity filter of our CaVAb model establishes a structural framework for understanding the mechanisms of ion selectivity and conductance by vertebrate CaV channels.
TL;DR: In contrast to the lithiation of SnO2 significantly less dislocation plasticity was seen ahead of the sodiation front, highlighting the critical role of ionic size and electronic structure of different ionic species on the charge/discharge rate and failure mechanisms in these batteries.
Abstract: Nonlithium metals such as sodium have attracted wide attention as a potential charge carrying ion for rechargeable batteries. Using in situ transmission electron microscopy in combination with density functional theory calculations, we probed the structural and chemical evolution of SnO2 nanowire anodes in Na-ion batteries and compared them quantitatively with results from Li-ion batteries (Huang, J. Y.; et al. Science 2010, 330, 1515−1520). Upon Na insertion into SnO2, a displacement reaction occurs, leading to the formation of amorphous NaxSn nanoparticles dispersed in Na2O matrix. With further Na insertion, the NaxSn crystallized into Na15Sn4 (x = 3.75). Upon extraction of Na (desodiation), the NaxSn transforms to Sn nanoparticles. Associated with the dealloying, pores are found to form, leading to a structure of Sn particles confined in a hollow matrix of Na2O. These pores greatly increase electrical impedance, therefore accounting for the poor cyclability of SnO2. DFT calculations indicate that Na+ d...
TL;DR: In this article, high-temperature analyses of the desodiated state NaFeP2O7 showed an irreversible phase transition from triclinic (P1) to the ground state monoclinic polymorph above 560 °C.
Abstract: Vying for newer sodium-ion chemistry for rechargeable batteries, Na2FeP2O7 pyrophosphate has been recently unveiled as a 3 V high-rate cathode. In addition to its low cost and promising electrochemical performance, here we demonstrate Na2FeP2O7 as a safe cathode with high thermal stability. Chemical/electrochemical desodiation of this insertion compound has led to the discovery of a new polymorph of NaFeP2O7. High-temperature analyses of the desodiated state NaFeP2O7 show an irreversible phase transition from triclinic (P1) to the ground state monoclinic (P21/c) polymorph above 560 °C. It demonstrates high thermal stability, with no thermal decomposition and/or oxygen evolution until 600 °C, the upper limit of the present investigation. This high operational stability is rooted in the stable pyrophosphate (P2O7)4– anion, which offers better safety than other phosphate-based cathodes. It establishes Na2FeP2O7 as a safe cathode candidate for large-scale economic sodium-ion battery applications.
TL;DR: Low lying excited states of the fullerene anion promote a faster charge separation in organic solar cells containing fullerenes derivatives as electron acceptor as well as alternative electron acceptors.
Abstract: Low lying excited states of the fullerene anion promote a faster charge separation in organic solar cells containing fullerene derivatives as electron acceptors. Alternative electron acceptors, not based on fullerenes but that share the same property, can be easily designed. On the other hand, it is unlikely for a generic electron acceptor to replicate this fullerene characteristic by chance.
TL;DR: An air-stable star-shaped CoIICoIII3 complex with only one paramagnetic Co(II) ion in the D3 coordination environment has been synthesized from a chiral Schiff base ligand as mentioned in this paper.
Abstract: An air-stable star-shaped CoIICoIII3 complex with only one paramagnetic Co(II) ion in the D3 coordination environment has been synthesized from a chiral Schiff base ligand. Magnetic studies revealed that this complex exhibits slow magnetic relaxation in the absence of an applied dc field, which is one of the main characteristics of single-molecule magnets (SMMs). The relaxation barrier is as high as 109 K, which is quite large among transition-metal ion-based SMMs. The complex represents the first example of zero-field SMM behavior in a mononuclear six oxygen-coordinate Co(II) complex.
TL;DR: In this paper, a review on the wavelengths of all five 4f-5d transitions for Ce3+ in 150 different inorganic compounds (fluorides, chlorides, bromides, iodides, oxides, sulfides, selenides, nitrides) is presented.
TL;DR: A review of the optical properties of Mn4+ ions in a number of host lattices is presented in this article, where a simple criterion is proposed, which can effectively and easily describe ionicity/covalency of the Mn4-doped crystals.
TL;DR: In this paper, the synthesis of phase pure CuO nanoparticles by controlled pyrolysis of Cu-based MOF was reported and the performance of half-cell assembly was evaluated.
TL;DR: It is shown, through a critical review of the archival literature, that this model provides new insights on the assignment of the luminescence spectra and the related interpretation of the spectroscopic behaviors.
Abstract: A model is introduced to predict the energy of metal-to-metal charge-transfer transitions in oxide compounds containing Bi3+ ions and d0 or d10 metals (Mn+). The model takes into account the structural characteristics of the host lattices, the anion relaxation resulting from Bi3+ doping, and the electronegativities and coordination numbers of the Bi3+ and Mn+ ions in the compounds. It is shown, through a critical review of the archival literature, that this model provides new insights on the assignment of the luminescence spectra and the related interpretation of the spectroscopic behaviors.
TL;DR: It is concluded that efficient SMMs could be obtained in complexes combining strongly anisotropic and isotropic metal ions with large angular momentum rather than in polynuclear compounds involving stronglyAnisotropic ions only.
Abstract: The key characteristic of single-molecule magnets (SMMs) is the anisotropy-induced blocking barrier, which should be as efficient as possible, i.e., to be able to provide long magnetic relaxation times at elevated temperatures. The strategy for the design of efficient SMMs on the basis of transition-metal complexes such as Mn12Ac is well established, which is not the case of complexes involving strongly anisotropic metal ions such as cobalt(II) and lanthanides (Ln). While strong intraionic anisotropy in the latter allows them to block the magnetization already in mononuclear complexes, the presence of several such ions in a complex does not result automatically in more efficient SMMs. Here, the magnetic blocking in the series of isostructural 3d–4f complexes CoII–LnIII–CoII, Ln = Gd, Tb, and Dy, is analyzed using an originally developed ab initio based approach for the investigation of blocking barriers. The theoretical analysis allows one to explain the counterintuitive result that the Co–Gd–Co complex i...
TL;DR: The bioinspired ion pump should find widespread applicability in active transportation-controlling smart nanofluidic devices, efficient energy conversions, and seawater desalinization, and open the way to design and develop novel bioinspired intelligent artificial nanochannel materials.
Abstract: Bioinspired artificial functional nanochannels for intelligent molecular and ionic transport control at the nanoscale have wide potential applications in nanofluidics, energy conversion, and biosensors. Although various smart passive ion transport properties of ion channels have been artificially realized, it is still hugely challenging to achieve high level intelligent ion transport features in biological ion pumps. Here we show a unique bioinspired single ion pump based on a cooperative pH response double-gate nanochannel, whose gates could be opened and closed alternately/simultaneously under symmetric/asymmetric pH environments. With the stimulation of the double-gate nanochannel by continuous switching of the symmetric/asymmetric pH stimuli, the bioinspired system systematically realized three key ionic transport features of biological ion pumps, including an alternating gates ion pumping process under symmetric pH stimuli, transformation of the ion pump into an ion channel under asymmetric pH stimul...
TL;DR: In this article, the role of metal nanoparticles for the extra capacity of transition metal oxides (MOs) was investigated, and Fe3O4@C and Fe@C monodispersed hierarchical core-shell microspheres were designed and adopted as the case study.
Abstract: The conversion reaction mechanism has widely been accepted in interpreting and evaluating the lithium storage capability of transition metal oxides (MOs). However, this mechanism cannot well explain the phenomenon of the extra capacity which exists in almost all MO materials and attracts much attention. Up to now, the extra capacity phenomenon has generally been ascribed to the reversible conversion of polymeric gel-like films. However, the essential role of metal nanoparticles in this process has not been systematically investigated. To further illustrate the role of metal nanoparticles for the extra capacity, Fe3O4@C and Fe@C monodispersed hierarchical core–shell microspheres were designed and adopted as the case study. Naturally Fe3O4@C composites exhibited a large Li storage capacity beyond its theoretical value. However, Fe@C microspheres, which are usually regarded to be inert for lithium storage, still presented a certain electrochemical capacity. Fe nanoparticles might serve as electrocatalysts for the reversible conversion of some components of solid electrolyte interface films, and bring extra capacity to Fe3O4 and electrochemical capacity to Fe. This study can enlighten us for the exploiting of advanced active materials and electrolytes for Li ion batteries, and new energy storage devices.