Kinds Of Cations Research Articles

Synergistic regulation of chloride anion recognition using a triple-functional sites receptor with two different cationic effectors.

The synergistic regulation of the multi-functional sites on one receptor molecule with different cationic effectors for anion recognition is scarce to be well understood from the experiment and theory. In this work, a new anion receptor with three functional zones including ether hole, biurea and double bipyridine groups (EUPR) is designed expecting to enhance the chloride anion recognition together with a rational synthesis path being proposed based on four simple and mature organic reaction steps. The conformational structures of the designed receptor EUPR and the binding behaviors for three kinds of ions (Cl-, Na+, and Ag+) are deeply investigated by using density functional theoretical calculations. It is found that Cl- binding via the hydrogen bond interaction can be significantly enhanced and synergistically regulated by the two kinds of cations and the corresponding conformational changes of receptor EUPR. Especially, the conformational pre-organization of receptor caused by the encapsulation of sodium ion into ether hole is benefit to the binding for Cl- in both thermodynamics and kinetics. Na+ binding, in turn, can ever be enhanced by chloride anion, whereas it seems that Ag+ binding cannot always be enhanced by chloride anion, reflecting an electrical complementary matching and mutual enhancement effect for different counter ions. Moreover, solvent effect calculations indicate that EUPR may be an ideal candidate structure for Cl- recognition by strategy of counter ion enhancement in water. Additionally, a visual study of intermolecular noncovalent interaction (NCI) and molecular electrostatic potential (ESP) are used for the analysis on the nature of interactions between receptor and bound ions.

Yb0.5Ca0.75Si7.5Al4.5O1.5N14.5 α-SiAlON ceramics: A hard material with low thermal conductivity

High hardness is desirable for thermal insulation materials in various applications to improve wear resistance. However, hard materials like diamond, Si3N4, and SiC are often accompanied by high thermal conductivity, due to their strong covalent bonds and high Young’s modulus, which increase sound velocity and benefit heat transportation. How to achieve concurrent high hardness and low thermal conductivity remains a challenge in thermal insulation materials. In this work, we report (Yb+Ca) co-doped α-SiAlON (Yb0.5Ca0.75Si7.5Al4.5O1.5N14.5, a solid solution of α-Si3N4) with a low thermal conductivity of 3.4 W/(m·K) and a hardness of 18.1 GPa at 25℃. The thermal conductivity of α-SiAlONs co-doped by (Yb+Nd/Lu) were also studied, and we found that phonon scattering could be significantly increased only when there was a remarkable difference in cation mass and radius between the co-doping cations, like that between Yb3+ and Ca2+. Additionally, high-entropy α-SiAlONs co-doped by five kinds of cations were studied (e.g., Nd0.1Gd0.1Dy0.1Er0.1Yb0.1Si9.5Al2.5ON15), and we found that the high-entropy strategy is not so effective in pursuing low thermal conductivity in α-SiAlONs. The contribution of different phonon scattering mechanisms in the α-SiAlONs was discussed based on inverse thermal diffusivity. Compared with most other ceramics (e.g., 8YSZ and rare-metal zirconates) with low thermal conductivity, (Yb+Ca) co-doped α-SiAlON has a lower bulk density, higher hardness, and higher toughness, which makes it a potential candidate material for applications requiring both thermal insulation and good mechanical properties.

Determining anisotropic reactive facet of ilmenite photocatalyst with Hubbard U assisted density functional theory

Findings on favorable charge-transfer pathways have been challenged for the enhancing catalytic reaction because electrical and optical efficiency are influenced by the interfacial/surface environment on the crystal structure. Herein, the electric and optical peculiarities of ATiO3 ilmenite catalyst are investigated for the anisotropic charge pathways by density functional theory framework with Hubbard U (DFT + U). The uncertainty for the best Hubbard U is simulated for the lattice parameters and band gaps in ATiO3. Our simulation corrected by Hubbard U = 10 eV shows the best reliability for ATiO3 involving 30 atoms as a basis at constant ilmenite structure and concluded that Perdew-Burke-Ernzerhof functional performance overcomes the deficiency of standard local density approximation functionals. Anisotropic carrier mobility in the Brillouin zone is compared with DFT + U on A-site cation effects. Among the representative three kinds of cations, our result shows that NiTiO3 exhibits a good optical absorption performance with the dielectric function and absorption coefficient in the visible light range, especially along the b3 direction which facilitates the separation of photogenerated electron-hole pairs at the top side of the shape. Our computational approach suggests a high reactive crystal facet of transition metal oxide contributing to the viable approach for the efficient catalytic reaction.

Molecular dynamics study on the impacts of cations in sea salt aerosol on transport performance of Nafion Membranes for PEMFCs in marine application

The application of polymer electrolyte membrane fuel cells (PEMFCs) in marine industry receives a widespread attention, due to the severe emission regulations. However, cationic contaminants in sea salt aerosol have detrimental effects on the transport performance of polymer electrolyte membranes, which are the core components of PEMFCs. In this study, the effects of K+ and Mg2+ in marine atmosphere on the transport performance of Nafion 117 membranes were evaluated by molecular dynamics simulations. Moreover, the influence of temperature is considered for the first time. The mean square displacements are used to evaluate the diffusion coefficients of water molecules (H2O) and hydronium ions (H3O+). In addition, the effect mechanisms are analyzed using radial distribution functions, water clusters distribution and relative concentration distribution. Results show that the diffusion of H3O+ and H2O is significantly weakened by K+ and Mg2+. Moreover, the impact of Mg2+ is more serious. The difference in the influence of these two kinds of cations on the transport performance of Nafion membranes is discussed by hydrated radius, hydration degree of cations, and the interaction between cations and sulfonic groups. The diffusion coefficients increase significantly with the increase of temperature. The increase of the temperature can also increase the interaction between the cations and the sulfonic groups. In contrast, the interaction between the sulfonic groups and water molecules is decreased.

Synthesis and characterization of novel ionic liquids based on imidazolium for acid corrosion inhibition of aluminum: Experimental, spectral, and computational study

Three newly ionic liquids namely, 1-bnzyl-2-methyl-3-octyl-1H-imidazol-3-ium bromide, 1-bnzyl-3-decyl-2-methyl-1H-imidazol-3-ium bromide, and 1-bnzyl-3-dodecyl-2-methyl-1H-imidazol-3-ium bromide are synthesized and their chemical structures characterized via different spectra techniques (FT-IR, elemental analysis,and 1H NMR). The corrosion inhibition of newly ionic liquids was evaluated on aluminum alloy in 1 M HCl at varied exposure temperatures (298–318 K) and varied concentrations via various experimental and theoretical methods for example mass loss, electrochemical, spectral, and computational calculations. The results illustrate that these types of ionic liquids inhibit corrosion of aluminum in acid solution with maximum inhibition efficiency was reached 83.2 % at 298 K. The inhibition efficiency increases with the addition of zinc sulfate which has a synergistic impact which was reached to 92.7%. Also, the concentration of ionic liquids and the kind of cation have an impact on the obtained results. The existence of these inhibitors in the acidic solution improves the charge transfer resistance and lessens the double-layer capacitance. The Langmuir adsorption isotherm governs the adsorption of these inhibitors' molecules on the aluminum alloy surface, and they behave as mixed-type inhibitors. The outputs reveal that the computational calculations match the experimental data rather well.

Osmotic Pressure and Diffusion of Ions in Charged Nanopores.

The transport of ions and water in nanopores is of interest for a number of natural and technological processes. Due to their practically identical long straight cylindrical pores, nanoporous track-etched membranes are suitable materials for investigation of its mechanisms. This communication reports on simultaneous measurements of osmotic pressure and salt diffusion with a 24 nm pore track-etched membrane. Due to the use of dilute electrolyte solutions (1–4 mM KCl and LiCl), this pore size was commensurate with the Debye screening length. Advanced interpretation of experimental results using a full version of the space-charge model has revealed that osmotic pressure and salt diffusion can be quantitatively correlated with electrostatic interactions of ions with charged nanopore walls. The surface-charge density is shown to increase with electrolyte concentration in agreement with the mechanism of deprotonation of weakly acidic surface groups. Moreover, a lack of significant surface-charge dependence on the kind of cation (K+ or Li+) demonstrates that binding of salt counterions does not play a major role in this system.

Tuning the structure of pyridinolate-based functional ionic liquids for highly efficient SO2 absorption

A series of pyridinolate anion-functional ionic liquids (ILs) containing different kinds of cations were designed and prepared, including tri-n-hexyltetradecylphosphonium [P66614], tri-n-butylethylphosphonium [P4442], and 1,1,3,3-tetramethylguandinium [TMG] cations and pyridinolate [PyO] anions with different N positions. Densities and viscosities at different temperatures were measured because of their importance for the absorption of SO2. Effect of different structures on the absorption of SO2 was studied, including the type and the alkyl chain length of cations, and the N positions of [PyO] anions (2-, 3-, and 4-). Additionally, effects of SO2 concentration and temperature for absorption were investigated. Especially, up to 6.00 and 2.53 mol SO2 per mole IL could be obtained by [P66614][4-PyO] at 1 bar and 0.1 bar of SO2, respectively, when absorptions performed at 20 °C. The results indicate that (1) the aprotic cations weakened the cation⋯anion interaction and resulted in the released active sites on the anions, and (2) N position has an influence on charge distribution of [PyO] anions and resulted in the tunable absorption of SO2. Reversible SO2 absorption and [P66614][4-PyO] regeneration could be performed several times without losing efficiency. Furthermore, the mechanism of absorption was studied through FT-IR and NMR methods and the results showed that the absorption of SO2 by [P66614][4-PyO] includes physisorption and chemisorption.

Growth Performance and Antioxidative Response of Chlorella pyrenoidesa, Dunaliella salina, and Anabaena cylindrica to Four Kinds of Ionic Liquids

Ionic liquids are widely used for lipid and pigment extractions from microalgae. It is possible that ionic liquids are discharged into environments. The evaluation of growth performance and antioxidative response of ionic liquids to microalgae is helpful to explore the stress regulation mechanism and investigate possible environmental risk. Ionic liquids induce production of reactive oxygen species (ROS) to microalgae. These oxidative stresses are possible from cations, anions, and salinity. In this study, the growth inhibitions of [BMIM]Br, [BMIM]Cl, [EMIM]Cl, and [EMIM]EtOSO3 to Anabaena cylindrica, Chlorella pyrenoidesa, and Dunaliella salina were evaluated. It was interesting that Br- and two kinds of cations, [BMIM] and [EMIM], had significant effects on growth inhibitions of these microalgae. IC50 values of these ionic liquids for A. cylindrica, C. pyrenoidesa, and D. salina were also estimated based on the results of growth inhibitions. It was proved that [EMIM]Cl is relatively harmless to C. pyrenoidesa and D. salina, and [EMIM]EtOSO3 is relatively or practically harmless to C. pyrenoidesa. [BMIM]Br and [BMIM]Cl are practically harmless to A. cylindrica and C. pyrenoidesa, and relatively harmless to D. salina. More than 0.8 g/L [EMIM]EtOSO3 led to bleaching of both A. cylindrica and D. salina at 48 h which was shown that the anion, EtOSO3-, had higher inhibition to A. cylindrica and D. salina than Cl-. In addition, high concentration of ionic liquids led to reductions of chlorophyll content in these three kinds of microalgae, increase of ROS levels and malondialdehyde contents for most of the cases. High concentration of ionic liquids also increased the activities of superoxide dismutase in three kinds of microalgae. There were positive correlations between ROS levels or MDA content, and inhibitions ratios of these ionic liquids to microalgae except [EMIM]Cl to A. cylindrica. These antioxidant enzymes were beneficial for reducing the ROS induced by ionic liquids.

ϒ-Li3PO4-Type Solid Electrolytes in Li4GeO4-Li4SiO4-Li3VO4 Quasi-Ternary System with High Lithium Ionic Conductivity

Lithium superionic conductors (LISICONs) are promising materials to realize high safety, high energy all-solid-state lithium-ion batteries. Through a dual-cation-substitution strategy, we designed ternary solid solutions of Ge-Si-V derivatives with a γ-Li3PO4-type structure in the Li4GeO4-Li4SiO4-Li3VO4 quasi-ternary system, and the relationship among their compositions, phase formation, and ionic conductivity was analyzed. The samples were fabricated through a solid-state reaction at 1173 K. The crystalline phase of the samples was identified through X-ray diffraction (XRD). The crystal structure was elucidated with Rietveld refinement of Synchrotron X-ray diffraction data. The morphologies and elemental distributions of the synthesized samples were examined through scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). The ionic conductivities of the synthesized samples at various temperatures were determined by AC impedance spectroscopy. An all-solid-state battery using the discovered LISICON material was fabricated in an Ar-filled glovebox. The positive and negative electrodes were composed of a mixture of LiNbO3-coated LiCoO2 with Li10GeP2S12 and Li-In metal, respectively. A charge-discharge test was conducted between 1.9 and 3.6 V at an applied current of 0.03 mA cm−1 (0.05 C rate) at 373 K. This study determined the phase-formation regions in the Li4GeO4-Li4SiO4-Li3VO4 quasi-ternary system and demonstrated relatively high ionic conductivity of the γ-Li3PO4-type phase structures.A high conductivity with low activation energy was achieved in ternary compositions compared to that in any binary system. The bulk ionic conductivity of 5.8 × 10−5 S cm−1 at 298 K was obtained for Li3.55(Ge0.45Si0.10V0.45)O4 with a low activation energy of 0.37 eV. Li3.55(Ge0.45Si0.10V0.45)O4 maintained high ionic conduction property (~10−5 S cm−1) even for the total conductivity (sum of bulk and grain-boundary contributions). Ionic conductivity of the Li4GeO4-Li4SiO4-Li3VO4 system was visualized along with the phase-identification results, as shown in the provided figure. In this color contour map (Fig. 1), relatively high ionic conductivity is confirmed around the γ-Li3PO4-type phase area (the region around sample #9); Li3VO4, Li4SiO4, and Li4GeO4 solid solutions or their mixture exhibited low ionic conductivity. Compared to any binary composition system (i.e., Li-X-Y-O), the existing tie line between the corner of this triangular ternary composition system (i.e., Li-X-Y-Z-O) has a higher ionic conductivity. Particularly, the ionic conductivity of Li3.55(Ge0.45Si0.10V0.45)O4 at #9 is slightly higher than that of Li3.6(Ge0.6V0.4)O4, which is the composition showing the highest ionic conductivity reported to date of LISICONs in the binary systems. Besides, the activation energy of Li3.55(Ge0.45Si0.10V0.45)O4 was much lower than that of Li3.6(Ge0.6V0.4)O4. The activation energy decreased by ~17.8% compared with that of the Li3.6(Ge0.6V0.4)O4 (0.45 eV). Therefore, the novel material-search concept (more complex composition) is one of the positive directions for developing the LISICON-type ionic conductors. The absolute value of 5.8 × 10−5 S cm−1 exceeded that of the reported ternary material in the Li4GeO4-Li4PO4-Li3VO4 system (5.1 × 10−5 S cm−1) (ACS Appl. Energy Mater. 2 (2019) 6608–6615). In other words, the ionic conductivity of the discovered material is higher than that of all the practically existing LISICONs, including the ternary systems. Further optimization in the ternary system or a more complex composition system could be a promising way for the subsequent material search.The high ionic conductivity property (σ) was achieved by reducing the activation energy (E a) and increasing the pre-exponential factor (σ0) through dual doping, which determines the σ value as described in the Arrhenius equation: σT = σ0exp(−E a/kBT). Li3.55(Ge0.45Si0.10V0.45)O4 functioned as a solid electrolyte in an all-solid-state cell, indicating the features of a pure lithium ionic conductor without electronic conduction. The LISICON oxide prepared via a cold-press functioned as a solid-electrolyte separator similar to sulfide solid electrolytes in all-solid-state batteries without high-temperature sintering. This demonstration could be the first step to developing room-temperature-LISICONs-based all-solid-state lithium ionic batteries. This work verified that the dual-cation-substitution strategy is beneficial for compositional and structural optimization, affording enhanced ion-conducting properties. Additionally, the substitution of more kinds of cations with larger radii into LISICONs is proposed; further enhancement in ionic conductivity could be expected in the case of the LISICON with a larger lattice size. Ternary LISICON systems using cations with larger ionic radii (e.g., Al3+, Ga3+) are an attractive candidate for future research. Figure 1

Localization and steric effect of the lone electron pair of the tellurium Te4+cation and other cations of thep-block elements. A systematic study

A simple method has been developed based on pure geometrical concepts to localize lone pairs (LPs) of cations of thep-block elements and model their steric effect. The method was applied to 1185 structures containing LP cations in 2439 non-equivalent positions. For oxide crystal structures, it is observed that, going from bottom left to top right in the periodic table, LPs move away from the cation core and decrease in size. For a given kind of cation M*, the LP radius increases linearly with the M*–LP distance, the smallest rate being observed for Tl+and the largest for Cl5+. The influence of the anion type was also studied in the case of the Te4+cation. Overall, the same trends were observed. The smallest Te–LP distances and LP radii are found for anions of large size and small charge.

Piperidinium and Pyrrolidinium Ionic Liquids as Precursors in the Synthesis of New Platinum Catalysts for Hydrosilylation

Six new air-stable anionic platinum complexes were synthesized in simple reactions of piperidinium [BMPip]Cl or pyrrolidinium [BMPyrr]Cl ionic liquids with platinum compounds ([Pt(cod)Cl2] or K2[PtCl6]). All these compounds were subjected to isolation and spectrometric characterization using NMR and ESI-MS techniques. Furthermore, the determination of melting points and thermal stability of the above derivatives was performed with the use of thermogravimetric analysis. The catalytic performance of the synthesized complexes was tested in hydrosilylation of 1-octene and allyl glycidyl ether with 1,1,1,3,5,5,5-heptamethyltrisiloxane. The study has shown that they have high catalytic activity and are insoluble in the reaction medium which enabled them to isolate and reuse them in consecutive catalytic cycles. The most active complex [BMPip]2[PtCl6] makes it possible to conduct at least 10 catalytic runs without losing activity which makes it an attractive alternative not only to commonly used homogeneous catalysts, but also to heterogeneous catalysts for hydrosilylation processes. The activity of the studied catalysts is also affected by the kind of anion and, to some extent, the kind of cation.

Impact of Divalent Cations on the Rheology of Cellulose Nanofibrils

Cellulose nanofibrils (CNFs) hydrogels have been used in various applications due to their ability to form gels via entanglement networks in water. In this study, the rheological properties of CNF gel with various concentrations of divalent cations (Mg<SUP>2+</SUP>, Ca<SUP>2+</SUP>, and Ba<SUP>2+</SUP>) are investigated using a rheometer (MCR 102, Anton Paar, Austria). The addition of divalent cations significantly increased the viscosity, storage modulus, and loss modulus as the concentration of cation increased from 100 to 8,000 ppm that contributed to the formation of stronger gels. This phenomenon indicates that higher cation concentration leads to fibril aggregation and a stiffened network. However, when an excessive amount of cations (10,000 ppm) is added, the CNF starts to coagulate and lose strength. Compared to Ca<SUP>2+</SUP> and Ba<SUP>2+</SUP>, Mg<SUP>2+</SUP> has a greater effect on hydrogel strength at 100 ppm, and thus exhibited maximum strength at 5,000 ppm. The maximum strength of Ca<SUP>2+</SUP> occurred at 8,000 ppm, and Ca<SUP>2+</SUP> produced the strongest gel (Mg<SUP>2+</SUP> and Ba<SUP>2+</SUP> were second and third, respectively) between 500 and 1,000 ppm. Ba<SUP>2+</SUP> produced the highest-strength gel with the maximum strength achieved at 8,000 ppm. The impact of divalent ions on the rheological properties of CNF strongly correlated with the kind of cation used and the cation concentration.

Polar magnetic oxides from chemical ordering: A new class of multiferroics

Combining ferroelectricity and magnetism in the same material remains a challenge because it involves complex crystal chemistry and stringent symmetry requirements. In conventional ferroelectrics, the polarization arises from the second-order Jahn–Teller effect associated with cations of d0 or s2 lone pair electronic configuration. In contrast, the magnetism arises from cations with partially filled d or f electrons. Materials that incorporate these two kinds of cations in different crystallographic sites exhibit multiferroic properties but with weak coupling between magnetism and ferroelectricity. On the other hand, a strong cross-coupling occurs in some materials, where specific spin structures induce weak ferroelectricity below the magnetic ordering temperature. In this article, we discuss a new class of multiferroics where the polar distortion results from chemical ordering. These polar oxides are mainly pyroelectric in the entire temperature range and exhibit magnetoelectric coupling below the magnetic ordering temperatures.

Energetic double salts based on 4,4′,5,5′-tetranitro-2,2′-biimidazolate

In the past few decades, energetic salts have been a growing interest in the development of new energetic materials, and a series of new energetic salts were synthesized. The traditional energetic salts are designed or synthesized by selecting one kind of anion and one kind of cation, thereby limiting the numbers of high energetic salts. In this paper, to increase the numbers of energetic salts, double salts based on 4, 4′, 5, 5′-tetranitro-2, 2′-biimidazolate (TNBI) were designed and their physical properties were accurately calculated, and one of the designed double salt of ammonium triaminoguanidinium 4, 4′, 5, 5′-tetranitro-2, 2′-biimidazolate ([A][TAG][TNBI]) was further synthesized and fully characterized. These studies not only provides a new way to design specific compounds, but also obtained some good high energy density materials with the detonation pressures ranging from 24.18 to 29.08 GPa, detonation velocities ranging from 7966 to 8637 m/s.

First fluorescence sensor for simultaneously detecting three kinds of IIB elements (Zn2+, Cd2+ and Hg2+) based on aggregation-induced emission

This work report the first AIE-based fluorescence sensor that can simultaneously detect three kinds of IIB elements (Zn2+, Cd2+ and Hg2+) in aqueous media. The thiourea-bridging bis-tetraphenylethylene (Bis-TPE) was synthesized by the condensation reaction of formyltetraphenylethylene and bis-thiosemicarbazide derivative in 82 % yield. Due to the AIE effect in the aqueous medium, the long-wavelength fluorescence was observed at 500–526 nm. It displayed high selective Zn2+-sensing ability with red-to-green fluorescence change, selective Cd2+-sensing ability with red-to-yellow fluorescence change and selective Hg2+-sensing ability with fluorescence enhancement, respectively. Moreover, it could detect simultaneously Zn2+, Cd2+ and Hg2+ in the mixed solution of these three kinds of cations by the fluorescence change with the assistance of Cl− and ATP. The sensing mechanism was confirmed as 1:1 stoichiometric ratio between host and guest. The detection limits were as low as 8.22×10-8 M, 2.36×10-7 M and 3.43×10-8 M for Zn2+, Cd2+ and Hg2+, respectively. These sensing abilities were applied as test strips for detecting Zn2+, Cd2+ and Hg2+, and were used for living cell imaging, implying a high efficient and simple method for analyzing trace IIB elements (Zn2+, Cd2+ and Hg2+) simultaneously in complex environments and living bodies.

Application of the Hybrid-Ion Battery Concept to Selected Oxide Systems

The success of Li-ion batteries led to a steady growth of applications that rely on this energy storage technology. However, the non-abundancy of necessary resources requires the establishment of successor technologies such as Na- or Mg-ion batteries. Both are still missing a breakthrough due to a variety of issues. Recently, the concept of hybrid batteries, which is based on a combined operation of two kinds of cations, has been proposed, bridging the gap between lithium and post-lithium energy storage [1]. Its main idea is to restrict chemical processes of one cation type to only one electrode while the other cation type takes part in processes on the other electrode. This results in the replacement or significant reduction of lithium amounts in a battery. Focusing on Li+, Na+ and Mg2+ ions as charge carriers, three types of hybrid batteries can be considered as Mg-Li, Mg-Na and Na-Li batteries. Currently, the main challenges are the search of a suitable electrolyte system compatible with both anodes and cathodes, as well as obtaining acceptable long-term cycling behavior, which is influenced strongly by many factors such as different SEI compositions. We studied different types of hybrid batteries with non-aqueous dual salt electrolytes using well-known electrode materials like Li4Ti5O12, TiNb2O7, LiFePO4 and LiV3O8 with the aim to evaluate issues concerning individual materials as well as general correlations referring to the certain type of a hybrid system. For example, we investigated LiV3O8 cathodes in mixed Na-Li electrolytes and found structural changes and the electrochemical behavior to be strongly influenced by the Li/Na ratio (Fig. 1). By obtaining higher capacities than in pure Na-ion batteries and better cycling behavior than in Li-ion batteries, we demonstrated that this concept represents a good compromise between these battery types. However, observed lithium plating on sodium anodes seems to be a general weakness of the hybrid Na-Li battery for the given electrolyte compositions, which has to be overcome [2]. Mg-Li batteries were studied using TiNb2O7 and Li4Ti5O12 operating at intermediate potentials that yielded promising results (Fig.2). A careful examination of structural evolution and the composition in a subsurface region revealed Li+ selectivity for bulk intercalation while Mg2+ is restricted to the anodic reaction. When aiming at higher voltages, electrolytes capable of depositing and stripping Mg become either unstable or reactive towards non-inert current collectors, but the applicability of LiFePO4 and LiV3O8 in dual salt electrolytes using special setups could be demonstrated. For the Mg-Na combination, we studied layered sodium oxides in a broad voltage range, and showed capability of desodiation of the layered structures and anodical deposition of Mg. However, the reverse reaction occurs at significantly lower discharge potentials with a large polarization. Figure 1

A dual-channel sensor containing multiple nitrogen heterocycles for the selective detection of Cu2+, Hg2+ and Zn2+ in same solvent system by different mechanism.

A molecule 3 containing multiple nitrogen heterocycles has been designed and synthesized. The systematical studies on sensing behaviors of compound 3 in DMSO/H2O by fluorescent and UV–vis absorption spectra indicate that this molecule shows the selectivity to Cu2+, Hg2+ and Zn2+ by dual-channels. Compound 3 shows significant fluorescence quenching to both Cu2+ and Hg2+ but with a red-shift for Hg2+, and only for Zn2+ there are fluorescence colorimetric and ratiometric changes. Furthermore, the absorption spectrum of 3 to Cu2+ also exhibits ratiometric change with the color change of solution from colorless to yellow, while no similar response to Hg2+ and Zn2+. These changes can be recognized via naked eyes. Three kinds of different mechanism have been convincingly proposed through ESI-Mass, 1H NMR titration, FT-IR spectra and DFT calculation. The suitable pH range of sensor 3 to Cu2+, Hg2+, Zn2+ has been determined to be 5.1–13.3, 6.9–11.2, 5.1–12.2, respectively. And time response experiments show that, as a fast-responsive fluorescent sensor for three kinds of cations, it can be used for the real-time analysis of Hg2+. Particularly, the reversible detection of Cu2+ in 5 cycles indicates that sensor 3 is expected to be a molecular logic gate for Cu2+.

Understanding of structures, dynamics, and hydrogen bonds of imidazolium-based ionic liquid mixture from molecular dynamics simulation

Here we employ molecular dynamics simulation to study structures, dynamics, and hydrogen bonds of the imidazolium-based ionic liquid mixture, which consists of equimolar [Emim][BF4] and [Bmim][BF4]. Our simulation results demonstrate that the imidazolium rings of both different cations almost show identical structures with [BF4]− anions regardless of the alkyl chain length. Meanwhile, both kinds of cations almost display the same association/dissociation dynamics with anions. By comparison, the order of diffusion speed is [Emim]+ > [Bmim]+ > [BF4]− while that of rotation speed is [BF4]− > [Emim]+ > [Bmim]+ in the ionic liquid mixture. By analyzing the average numbers of hydrogen bonds (HBs) and the relevant HB dynamics between cations and anions, we find that [Bmim]+ cations have more and stronger HBs with anions than [Emim]+ cations, which should be partly responsible for slower diffusion and rotation of [Bmim]+ cations than those of [Emim]+ cations. Therefore, this simulation study provides a molecular-level understanding of the role of alkyl chain and HB on the relevant structure and dynamics properties in the imidazolium-based ionic liquid mixture.

Structure and dynamics of microbial fuel cell catalyst layer

Molecular dynamics method is used to investigate the mass transfer rules of reactants H3O+ and O2 in the cathode catalyst layer in the presence of five kinds of cations (Na+, K+, NH4+, Mg2+, Ca2+) in the microbial fuel cell solution environment. Structural characteristics of the catalyst layer Pt/C substrate/Nafion/solution three-phase interface are also analyzed. The results show that the transport mechanism and pathway of H3O+ in the catalyst layer are similar to those of monovalent cations (Na+, K+, NH4+). The minimum diffusion coefficient of H3O+ appears in the presence of K+. On the other hand, H3O+ mainly transport inside the water clusters in the presence of divalent cations (Mg2+, Ca2+). The diffusion law of metal cations (K+> Na+> Mg2+> Ca2+) is still applicable in the catalyst layer containing Nafion ionomer and unaffected by cation concentration. In general, the higher concentration of O2 molecules in the main part of the Nafion phase and the farther distribution from the carbon substrate cause a larger O2 diffusion coefficient. Moreover, the O2 transport pathways in the main part of the Nafion phase are along the Nafion hydrophilic/hydrophobic phase interface and inside the hydrophobic phase. In the presence of Ca2+, the concentration of O2 near the Pt particles is the highest. These O2 molecules tend to adsorb on the surface of Pt particles with small size. Thus, the catalyst utilization rate is high. In addition, Ca2+ has a strong cross-linking effect on the sulfonic acid groups from different Nafion molecules, which helps to enhance the stability of the catalyst layer.

Perovskite solar cells passivated by distorted two-dimensional structure

Hybrid perovskites are a series of solution-processable materials for photovoltaic devices. To achieve better performance and stability, interface passivation is an effective method. So far, the most commonly used passivators are organic amines, which can tailor perovskite into a lower-dimensional structure (Ruddlesden-Popper perovskite). Here, we select a biimizole (BIM) molecule as a new passivator for perovskite. The BIM based single layer perovskite has a more rigid structure. And multi-layered structure cannot be formed due to large lattice mismatching and structural rigidity. By inducing the excess MAI (methanaminium iodide) into the lattice, the layered structure is maintained, and half of the BIM molecules are replaced by MA (methylamine). The mixed layered structure is distorted, because of the difference in size between two kinds of cations. We then investigate passivation effect of BIM on perovskite solar cells. By carefully controlling the feed ratio in precursor solutions, we fabricate solar cells with different passivation structures. We find that the introduction of BIM can cause &lt;i&gt;V&lt;/i&gt;&lt;sub&gt;oc&lt;/sub&gt; to increase generally, indicating that MAPbI&lt;sub&gt;3&lt;/sub&gt; is well passivated. The peak at 7.5° and 15° in X-ray diffraction pattern are corresponding to a two-dimensional (2D) phase with a shorter layer distance. There are no peaks at lower degrees, so that no multi-layered structure is formed in the film either. We suppose that a dual-phase 2D-3D (where 3D represents three-dimensional) structure is formed in the perovskite film. To explain the passivation effect of the two 2D structures, we investigate their lattice matching towards MAPbI&lt;sub&gt;3&lt;/sub&gt;. The distorted 2D structure is well matched with (110) face of o-MAPbI&lt;sub&gt;3&lt;/sub&gt;, and the mismatching rate is lower 1% in the two directions. On the other hand, the BIM based 2D structure cannot well match with (–110) face of o-MAPbI&lt;sub&gt;3&lt;/sub&gt;, nor with (001) face of c-MAPbI&lt;sub&gt;3&lt;/sub&gt;. We also consider that the less rigidity of distorted structure contributes to better passivation. As a result, we achieve a BIM passivated perovskite solar cell with a power conversion efficiency up to 14%. This work paves a new way to the interface engineering of perovskite solar cells.