Valence Structure Research Articles

Is the bonding cumulenic or polyacetylenic in nonatetraynylidene?

To answer the entitled question, the equilibrium geometry of the linear triplet ground electronic state X∼3Σg- of nonatetraynylidene (1), HC9H, has been theoretically investigated at various levels of theory. The relative energies, optimal geometry parameters, expectation values of S2, rotational constant, spin densities, and harmonic vibrational frequencies with respect to both restricted open-shell Hartree-Fock (ROHF) and unrestricted HF (UHF) at different levels are examined. The methods employed are HF Self-Consistent Field (SCF), Møller-Plesset perturbation level of theory until second-order (MP2), coupled-cluster singles and doubles (CCSD), and CCSD with perturbative triple excitations (CCSD(T)). Correlation consistent polarized valence double and triple zeta (cc-pVXZ; X=D and T) basis sets are used in all calculations and frozen-core approximation is utilized in all post-SCF calculations. Population analysis of the spin densities at CC levels suggest that several valence structures are possible for 1 implying more polyacetylenic character rather than the cumulenic biradical.

X-ray powder diffraction, spectroscopic study, dielectric properties and thermal analysis of new doped compound TiGa0.67Te2.33O8

A novel mixed valence tellurium oxide, TiGa0.67Te2.33O8, was synthesized and its crystal structure determined using the X-ray powder diffraction technique. The obtained oxide was found to crystallize in a cubic unit-cell, Ia3¯ space group, with the lattice parameter a = 10.9557(1) Å. Rietveld refinement of the structure led to ultimate confidence factors Rp = 7.63 and Rwp = 6.71. This structure was based on slabs containing groups of (Te/Ga)O4 joined by the metal cations Ti4+. The structure analysis showed a cation ordering of Te4+ and Te6+ yielding a TiGa2/3Te7/3O8 formula. The IR and RAMAN spectra confirmed the presence of the TiO6 and (Te/Ga)O4 groups. The dielectric anomalies observed at 500 K were attributed to the mixed valence structure, arising from the mixed-valence Te6+/Te4+. We detected only one peak in thermal behavior by the DTA/TG analysis; which implied a melting reaction.

Layered SnS versus SnS2: Valence and Structural Implications on Electrochemistry and Clean Energy Electrocatalysis

Despite the far-reaching applications of layered Sn chalcogenides to date, their electrochemistry and electrochemical and electrocatalytic properties remain a mystery. The bulk of current research highlights promising uses of layered Sn chalcogenides with limited discourse on the relevance of Sn valency or crystal structures to their properties. We therefore examine the electrochemistry of orthorhombic SnS and hexagonal SnS2, and determine the implications to their electrocatalytic applications, namely, oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER). Higher inherent electroactivity has been demonstrated in SnS2 as indicated by three distinct cathodic signals juxtaposed with a broad reduction peak in the largely electro-inactive SnS. In addition, SnS2 exhibits a faster heterogeneous electron transfer (HET) rate than SnS, though both are of less-than-sterling showing when compared to the glassy carbon (GC) electrode in terms of current intensity. The ...

Effect of Local Structural Changes on Rate Capability of LiNi0.5Mn1.5O4-d Cathode Material for Lithium Ion Batteries

Due to its high working voltage (4.7 V vs. Li/Li+ for Ni2+/Ni4+ redox couple), high theoretical capacity (147 mAh/g), and inherent cyclic stability (no Jahn-Teller distortion from Mn3+), LiNi0.5Mn1.5O4 is a promising cathode material for the practical application in high energy density lithium ion batteries [1-3]. The cation ordering, the degree of presence of Mn3+ in the spinel structure is regarded as an important factor influencing the electrochemical properties of LiNi0.5Mn1.5O4. Especially, at high current densities, the better electrochemical performance was obtained in the disordered spinel, resulted from the higher electronic conductivity and lithium ion diffusivity [4,5]. With a simply strategy of cooling rate, the degree of ordering in disordered spinel LiNi0.5Mn1.5O4-δ structure is controlled at 0.5 oC/min for slow cooled spinel and at 5 oC/min for fast cooled spinel. From XRD and FTIR analyses and charge/discharge profiles, it is confirmed that the fast cooled spinel develops more disordered structure than the slow cooled spinel, retaining more oxygen vacancies and more abundant Mn3+. Moreover, through in situ XRD analysis, the more disordered spinel follows the extended solid-solution reaction in favor of Li+ transport, which results in an improved rate capability [6,7]. But, the local structure information of interesting atoms without a destructive interference which can arise from long-range structural order is highly related to the electrochemical performance. Therefore, the examination in local structural variations of interesting atoms is essential for understanding their electrochemical properties. X-ray absorption spectroscopy (XAS) is generally applied to examine the valence and local structure variations of an interesting atom within short-range order. In this work, we investigate local structural changes in the vicinity of Mn and Ni cations at various C-rates by using ex situ XAS analysis and quantify the structural changes by fitting a theoretical model to the extended X-ray absorption fine structure data. This finding will propose that a change of structural distortion can be another platform to understand the enhanced Li+ transport in the disordered spinel and offer valuable guidance for developing LiNi0.5Mn1.5O4, a promising cathode material, for the practical application in high energy density lithium ion batteries. More detailed discussion will be presented at the PRIME 2016 meeting. [1] X. Liu, D. Li, Q. Mo, X. Guo, X. Yang, G. Chen, S. Zhong, J. Alloys Compd. 609 (2014) 54–59. [2] X.-W. Gao, Y.-F. Deng, D. Wexler, G.-H. Chen, S.-L. Chou, H.-K. Liu, Z.-C. Shi, J.-Z. Wang, J. Mater. Chem. A. 3 (2015) 404–411. [3] H. Xia, Y.S. Meng, L. Lu, G. Ceder, J. Electrochem. Soc. 154 (2007) A737–A743. [4] S. Choi, J. Yoon, S. Muhammad, W.-S. Yoon, J. Electrochem. Sci. Technol. 4 (2013) 34–40. [5] M. Kunduraci, J.F. Al-Sharab, G.G. Amatucci, Chem. Mater. 18 (2006) 3585–3592. [6] J. Zheng, J. Xiao, X. Yu, L. Kovarik, M. Gu, F. Omenya, X. Chen, X.-Q. Yang, J. Liu, G.L. Graff, M.S. Whittingham, J.-G. Zhang, Phys. Chem. Chem. Phys. 14 (2012) 13515–13521. [7] H. Duncan, B. Hai, M. Leskes, C.P. Grey, G. Chen, Chem. Mater. 26 (2014) 5374–5382.

Meson/baryon/tetraquark supersymmetry from superconformal algebra and light-front holography

Superconformal algebra leads to remarkable connections between the masses of mesons and baryons of the same parity — supersymmetric relations between the bosonic and fermionic bound states of QCD. Supercharges connect the mesonic eigenstates to their baryonic superpartners, where the mesons have internal angular momentum one unit higher than the baryons: [Formula: see text] The dynamics of the superpartner hadrons also match; for example, the power-law fall-off of the form factors are the same for the mesonic and baryonic superpartners, in agreement with twist counting rules. An effective supersymmetric light-front Hamiltonian for hadrons composed of light quarks can be constructed by embedding superconformal quantum mechanics into AdS space. This procedure also generates a spin–spin interaction between the hadronic constituents. A specific breaking of conformal symmetry inside the graded algebra determines a unique quark-confining light-front potential for light hadrons in agreement with the soft-wall AdS/QCD approach and light-front holography. Only one mass parameter [Formula: see text] appears; it sets the confinement mass scale, a universal value for the slope of all Regge trajectories, the nonzero mass of the proton and other hadrons in the chiral limit, as well as the length scale which underlies their structure. The mass for the pion eigenstate vanishes in the chiral limit. When one includes the constituent quark masses using the Feynman–Hellman theorem, the predictions are consistent with the empirical features of the light-quark hadronic spectra. Our analysis can be consistently applied to the excitation spectra of the [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text] meson families as well as to the [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text] baryons. We also predict the existence of tetraquarks which are degenerate in mass with baryons with the same angular momentum. The mass-squared of the light hadrons can be expressed in a universal and frame-independent decomposition of contributions from the constituent kinetic energy, the confinement potential, and spin–spin contributions. We also predict features of hadron dynamics, including hadronic light-front wave functions, distribution amplitudes, form factors, valence structure functions and vector meson electroproduction phenomenology. The mass scale [Formula: see text] can be connected to the parameter [Formula: see text] in the QCD running coupling by matching the nonperturbative dynamics, as described by the light-front holographic approach to the perturbative QCD regime. The result is an effective coupling defined at all momenta. The matching of the high and low momentum-transfer regimes determines a scale [Formula: see text] proportional to [Formula: see text] which sets the interface between perturbative and nonperturbative hadron dynamics. The use of [Formula: see text] to resolve the factorization scale uncertainty for structure functions and distribution amplitudes, in combination with the scheme-independent Principle of Maximal Conformality (PMC) procedure for setting renormalization scales, can greatly improve the precision of perturbative QCD predictions.

Using Synchrotron Radiation to Study Li-Ion Batteries

X-Ray Absorption Spectroscopy (XAS) is a powerful tool, which can be used to study the atomic local structure as well as oxidation state during battery cycling. Hence, XAS can be used to provide detailed atomic information for improvement of materials design.Here we present in situ XAS results for Li2FeSiO4 and Li2.2Fe0.9SiO4, promising cathode materials for lithium-ion batteries. It provides a low cost solution and is considered as a safe electrode material for future electric transportation, as the Si–O bond provides stability similar to the P – O bond in LiFePO4 compounds. In theory, it is possible to remove two Li ions from Li2FeSiO4, by utilizing both Fe+2/Fe+3 and the Fe+3/Fe+4 redox couples and, thus, producing a higher capacity than 166 mAhg-1 for one Li ion. Although capacities greater than 200 mAhg-1 it has yet to be clarified whether it was due to Fe+4 formation or electrolyte degradation. The aim was to establish the valence and local structure of Fe during charge and discharge. The valence state changes between Fe+2 and Fe+3, with no evidence of Fe+4 before the onset of electrolyte degradation. There is a reversible contraction and extension of the Fe–O bond lengths during cycling while the Fe-Si distance remains constant, which underlines the stability of the Li2FeSiO4 material. The same observations apply to Li2.2Fe0.9SiO4 cathode material indicating that changing the stoichiometry does not provide any additional structural stability.1 1. A.W. Brownrigg, G. Mountjoy, A.V. Chadwick, M. Alfredsson, W. Bras, J. Billaud, A.R. Armstrong, P.G. Bruce, R. Dominko and E.M. Kelder, J. of Mater. Chem. A, 2015, 3, 7314-7322

Mapping Emotion Terms into Affective Space

Abstract. Recent empirical work on the semantics of emotion terms across many different cultures and languages, using a theoretical componential approach, suggested that four dimensions are needed to parsimoniously describe the semantic space of the emotion domain as reflected in emotion terms ( Fontaine, Scherer, Roesch, & Ellsworth, 2007 ; Fontaine, Scherer, & Soriano, 2013 ). In addition to valence, power, and arousal, a novelty dimension was discovered that mostly differentiated surprise from other emotions. Here, we further explore the existence and nature of the fourth dimension in semantic emotion space using a much larger and much more representative set of emotion terms. A group of 156 participants each rated 10 out of a set of 80 French emotion terms with respect to semantic meaning. The meaning of an emotion term was evaluated with respect to 68 emotion features representing the appraisal, action tendency, bodily reaction, expression, and feeling components of the emotion process. A principal component analysis confirmed the four-dimensional valence, power, arousal, and novelty structure. Moreover, this larger and much more representative set of emotion terms revealed that the novelty dimension not only differentiates surprise terms from other emotion terms, but also identifies substantial variation within the fear and joy emotion families.

Development and validation of a Self-esteem Contingency Questionnaire for Adolescents

Self-esteem (SE) contingency refers to the extent to which one's level of self-esteem depends on meeting certain internal or external criteria and has been identified as a psychological risk factor. Addressing limitations of existing SE contingency questionnaires, we developed a domain-specific situation-response questionnaire for adolescents that (1) measures SE contingency in domains which are considered important for adolescents, based on multidimensional self-concept models, and (2) includes balanced numbers of positive and negative items per domain, allowing to distinguish between upward and downward contingencies. The current findings support the reliability and validity of the new 24-item questionnaire in a sample of high school students (N=599, age range 15–22). Confirmatory factor analyses supported the 4 (domains)×2 (valence) structure of our questionnaire and its convergent and discriminant validity was established. Finally, external validity was supported by finding the expected associations with psychological control and depressive symptoms.

Enhanced intrinsic permittivity and bulk response in Y2/3Cu3Ti4+xO12 ceramics

Considering the contribution of the mixed valence structure of Ti3+ and Ti4+ to the semiconductivity of grain, compositions with the formula of Y2/3Cu3Ti4+xO12 were designed and prepared. The dielectric bulk responses of Y2/3Cu3Ti4+xO12 ceramics were explored in detail. Changing Ti stoichiometry gives rise to an increase of the intrinsic permittivity. Y2/3Cu3Ti3.925O12 ceramic exhibits a higher intrinsic permittivity of ~120 at 60MHz than that of pure Y2/3Cu3Ti4O12 ceramics (87 at 60MHz). Additionally, the activation energies of bulk responses are significantly enhanced by changing Ti stoichiometry, which is closely linked with the increase of Ti3+/Ti4+.

Constructing Ru/TiO2 Heteronanostructures Toward Enhanced Photocatalytic Water Splitting via a RuO2/TiO2 Heterojunction and Ru/TiO2 Schottky Junction

Photocatalysts based on metallic Ru and RuO2 dual co‐catalysts modified TiO2 nanobelts (NBs) are constructed through a wet‐impregnation reduction method with post thermal oxidation. The samples are characterized carefully and their photocatalytic activities for the half reactions of water splitting as well as full water splitting are evaluated systematically under solar light irradiation. The detailed characterizations and analyses clearly reveal the formation of a Schottky junction at the Ru‐TiO2 interface and of RuO2/TiO2 heterojunctions. The results of the photocatalytic tests show that both Ru and RuO2 can improve the photocatalytic activity for H2/O2 evolution and water splitting. Moreover, the photocatalytic activity of the TiO2 NBs can be further enhanced by co‐modification with dual Ru and RuO2 co‐catalysts. The RuO2/TiO2 heterojunction improves the transfer of the photogenerated holes from the TiO2 to the RuO2, where water can be oxidized by the holes to evolve O2, and the Ru/TiO2 Schottky junction promotes the transfer of photogenerated electrons from the TiO2 NBs to the metallic Ru for proton reduction into H2. These two processes are involved in the overall water splitting. This work provides an important reference for designing highly efficient photocatalysts for water splitting through loading of dual co‐catalysts containing the same element but with different valence structures.

The Antimicrobial Properties of Silver Nanoparticles in Bacillus subtilis Are Mediated by Released Ag+ Ions.

The superior antimicrobial properties of silver nanoparticles (Ag NPs) are well-documented, but the exact mechanisms underlying Ag-NP microbial toxicity remain the subject of intense debate. Here, we show that Ag-NP concentrations as low as 10 ppm exert significant toxicity against Bacillus subtilis, a beneficial bacterium ubiquitous in the soil. Growth arrest and chromosomal DNA degradation were observed, and flow cytometric quantification of propidium iodide (PI) staining also revealed that Ag-NP concentrations of 25 ppm and above increased membrane permeability. RedoxSensor content analysis and Phag-GFP expression analysis further indicated that reductase activity and cytosolic protein expression decreased in B. subtilis cells treated with 10–50 ppm of Ag NPs. We conducted X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) analyses to directly clarify the valence and fine structure of Ag atoms in B. subtilis cells placed in contact with Ag NPs. The results confirmed the Ag species in Ag NP-treated B. subtilis cells as Ag2O, indicating that Ag-NP toxicity is likely mediated by released Ag+ ions from Ag NPs, which penetrate bacterial cells and are subsequently oxidized intracellularly to Ag2O. These findings provide conclusive evidence for the role of Ag+ ions in Ag-NP microbial toxicity, and suggest that the impact of inappropriately disposed Ag NPs to soil and water ecosystems may warrant further investigation.

Solid solution strengthening of hexagonal titanium alloys: Restoring forces and stacking faults calculated from first principles

The solid solution strengthening of α-Ti was investigated in respect of dislocation nucleation and dissociation in all four active glide modes. A series of Ti+X alloys (X = Al, Sn, V, Zr and O) was selected to analyze the impact of solute valence structure (Al, Sn – p type elements, V, Zr – d type elements) and lattice site (interstitial O) on the mechanisms responsible for variation of mechanical properties. The computational procedure relied on the generalized stacking fault energy (GSFE) concept combined with the nudged elastic band method that enables full atomic relaxation and determination of the true, minimum energy GSFE path. Additionally, various concentrations of solutes and their distance to the glide plane were considered as well. Our study revealed a strong, nonlinear influence of X position on GSFE and migration of O atoms during the crystal slip. These new phenomena allowed one to determine three solution strengthening mechanisms: (I) hindrance of <a> prismatic dislocation emission and reconfiguration of 1/3 <112¯0> screw dislocation cores (p type solutes), (II) hindrance of <a> prismatic dislocation emission (V) and SFE reduction in other modes (both d type solutes) and (III) suppression of dislocation nucleation in all modes caused by O. We found that the stacking faults formed by the single partial dislocations have a thickness of few atomic layers and exhibit a highly non-uniform structure. Their ability to accommodate the lattice deformation introduced by solute elements greatly affects the stacking fault energies of the α-Ti alloys.

Magnesium oxide as a heterogeneous catalyst support

AbstractResearchers normally consider MgO as a promising high-surface-area heterogeneous catalyst support, additive, and promoter for many kinds of chemical reactions due to its certain properties, including stoichiometry and composition, cation valence, redox properties, acid-base character, and crystal and electronic structure. The presence of MgO as a support catalyst also modifies the electronic state of the overall catalytic performance by electron transfer between the native catalyst and MgO as support. The influence is clarified by alteration of acid-base properties of the catalyst-supported MgO. Meanwhile, the method, chemical composition, and condition in the preparation of MgO are the important factors affecting its surface and catalytic properties. Therefore, MgO with a high surface area and nanocrystalline structure has encouraging applications for some reactions, including as dry reforming, dehydrohalogenation, oxidative dehydrogenation of butane, nonoxidative dehydrogenation of ethylbenzene, decomposition of CCl

Examining the electrical and chemical properties of reduced graphene oxide with varying annealing temperatures in argon atmosphere

Graphene oxide flakes were successfully fabricated and deposited as a film onto a silicon substrate. A series of these samples were annealed at various temperatures under a low pressure argon environment. The valence structure of the surface is examined using ultraviolet photoelectron spectroscopy whilst the chemical nature of the surface is examined using X-ray photoelectron spectroscopy. The sheet resistance was measured to document the performance changes with variation in electronic and chemical nature of the surface. It was found that increasing the annealing temperature increased the 2p π content leading to a better conductivity and reduction in sheet resistance.

Effect of a Surface Area and a d‐Band Oxidation State on the Activity and Stability of RuOx Electrocatalysts for Oxygen Evolution Reaction

It is widely recognized that RuO2 is the best electrocatalysts for oxygen evolution reaction (OER) in water splitting in acidic media. In this study, we investigated the effect of a surface area and a d‐band oxidation state on the activity and the stability of RuO x electrocatalysts for OER. We synthesized RuO x thin film on glassy carbon electrode by the radio frequency magnetic sputtering and controlled the deposition temperature to vary the surface morphology and the electronic structure. In particular, we obtained a precise d‐band valence structure by using the synchrotron beam. A higher surface area and a more stable Ru4+ state were obtained at a lower deposition temperature owing to a smaller grain size and a lower oxidation state, respectively. As a result, the order of activity and stability is clearly consistent with that of surface area and stable Ru4+ state (RuO x &gt; RuO x 200 &gt; RuO x 400 &gt; RuO x 600). Hence, we suggest that the surface area and the Ru d‐band oxidation state should be carefully controlled in the synthesis process in order to enhance the activity and the stability of RuO x electrocatalysts for OER.

In-Situ Synchrotron XANES Study of Iron Oxyfluoride As Cathode Material in Lithium Ion Batteries

Iron oxyfluoride (FeOF) was recently found to be a conversion type cathode material for lithium ion batteries because of its high theoretical capacity[1] (885mAh). Rutile structure FeOF was both environmental friendly and economic which is promising to be put into market. During the charge and discharge process, the valence of iron changes from 3+ to 0 which means that it can deliver 3 electrons. Although there were a lot of work done by researchers on FeOF cathode, the cyclability of this cathode was still too poor[2]. In-situ pair distribution function (PDF) was performed on FeOF batteries by Wiadereck et.al[3]. However, more valance and local structure evolution was yet to be revealed. In order to increase the cycle life of FeOF, it is very important to clearly elucidate the failure mechanism by clearly understand the atom environment in real-time during the cycling. Synchrotron X-ray near-edge structure (XANES) could be very helpful to illustrate the local structure and state of charge of the element we are interested in[4]. With the help of XANES, we can apply in-situ characterization of FeOF cathode to better elucidate real-time local structure and valence change at different state of charge (SOC) and depth of discharge (DOD) in order to better illustrate the mechanism of the iron ion evolution and FeOF failure mechanism. In this study, FeOF was prepared in our lab and mixed with carbon black, PVDF and NMP to form a uniform slurry. The cathode was prepared by coating the slurry on aluminum foil. The in-situ test coin cell was assembled by FeOF cathode, Celgard separator and lithium foil anode and was sealed in our home-made coin cell shell. K-edge of Fe was measured during the in-situ characterization to observe the valence change and local structure evolution during the discharge and charge process between the voltage range of 4V and 1V. The in-situ XANES spectrum was plotted in Fig.1. From 0% DOD to around 50% DOD, the K-edge shifted to low energy direction and then shifted back to high energy direction. This phenomenon indicated that there were two different mechanism during discharge process. To better analyze the in-situ XANES data, the contour plot and the charge/discharge profile were shown in Fig.2. The XANES and charge/discharge profile correlated with each other very well. At the beginning of discharge process, the K-edge shifted towards low energy direction and the intensity increased gradually, which means this is a Li+intercalation process. At the end of the discharge process, the K-edge shifted back to the high energy direction and there was a sharp intensity change which corresponding to the conversion process. Similar conversion and deintercalation process could be observed at the beginning and end of the charge process respectively. In conclusion, by applying in-situ XANES technic, we clearly visualize the valence and local structure evolution mechanism during real working condition and got our preliminary conclusion that the charge/discharge process of FeOF battery contains two typical process. Li+ intercalation occurs at high voltage range and conversion process occurs at lower voltage range. Reference [1] A. Kitajou, H. Komatsu, R. Nagano, S. Okada, Synthesis of FeOF using roll-quenching method and the cathode properties for lithium-ion battery, Journal of Power Sources, 243 (2013) 494-498. [2] N. Pereira, F. Badway, M. Wartelsky, S. Gunn, G.G. Amatucci, Iron Oxyfluorides as High Capacity Cathode Materials for Lithium Batteries, Journal of The Electrochemical Society, 156 (2009) A407-A416. [3] K.M. Wiaderek, O.J. Borkiewicz, E. Castillo-Martínez, R. Robert, N. Pereira, G.G. Amatucci, C.P. Grey, P.J. Chupas, K.W. Chapman, Comprehensive Insights into the Structural and Chemical Changes in Mixed-Anion FeOF Electrodes by Using Operando PDF and NMR Spectroscopy, Journal of the American Chemical Society, 135 (2013) 4070-4078. [4] A.N. Mansour, P.H. Smith, W.M. Baker, M. Balasubramanian, J. McBreen, In situ XAS investigation of the oxidation state and local structure of vanadium in discharged and charged V2O5 aerogel cathodes, Electrochimica Acta, 47 (2002) 3151-3161. Figure 1

Electronic and surface properties of Ga-doped In2O3 ceramics

The limit of solubility of Ga2O3 in the cubic bixbyite In2O3 phase was established by X-ray diffraction and Raman spectroscopy to correspond to replacement of around 6% of In cations by Ga for samples prepared at 1250°C. Density functional theory calculations suggest that Ga substitution should lead to widening of the bulk bandgap, as expected from the much larger gap of Ga2O3 as compared to In2O3. However both diffuse reflectance spectroscopy and valence band X-ray photoemission reveal an apparent narrowing of the gap with Ga doping. It is tentatively concluded that this anomaly arises from introduction of Ga+ surface lone pair states at the top of the valence band and structure at the top of the valence band in Ga-segregated samples is assigned to these lone pair states. In addition photoemission reveals a broadening of the valence band edge. Core X-ray photoemission spectra and low energy ion scattering spectroscopy both reveal pronounced segregation of Ga to the ceramic surface, which may be linked to both relief of strain in the bulk and the preferential occupation of surface sites by lone pair cations. Surprisingly Ga segregation is not accompanied by the development of chemically shifted structure in Ga 2p core XPS associated with Ga+. However experiments on ion bombarded Ga2O3, where a shoulder at the top edge of the valence band spectra provide a clear signature of Ga+ at the surface, show that the chemical shift between Ga+ and Ga3+ is too small to be resolved in Ga 2p core level spectra. Thus the failure to observe chemically shifted structure associated with Ga+ is not inconsistent with the proposal that band gap narrowing is associated with lone pair states at surfaces and interfaces.

Chemical Components, Mercury Coordination Structure and Micro-Morphology of Tibetan Medicine Zuotai

In order to reveal the chemical substance basis of pharmacodynamic effects of Zuotai, energy dispersive spectrometry of X-ray (EDX), X-ray fluorescence spectroscopy (XRF), synchrotron radiation X-ray absorption fine structure (SR-XAFS), X-ray diffraction (XRD), scanning electron microscope (SEM) and atomic force microscope (AFM) were used to analyze the elements, the chemical valence and local structure of mercury, and the chemical phase composition and micro-morphology of Zuotai. EDX and XRF analysis shows that the main elements in Zuotai are Hg and S, with some other minor elements, such as 0, Fe, Al, Cu, K, Ag, Ca, Mg etc. SR-XAFS analysis shows that: the oxidation state of mercury in Zuotai is divalence, its neighbor atoms are S, and its coordination number is four. XRD assay found that β-HgS (cubic, F-43m 216) and S8 (orthorhombic, Fddd 70) are the main phase compositions in Zuotai. Besides, it also has a small amount of C (hexagonal, P63/mmc 194), Fel.05 S0.95 (hexagonal, P63/mmc 194), Cu6S6 (hexagonal, P63/mmc 194), Cu1.8 S (cubic, F-43m 216) and so on. And it was found that the crystallinity of Zuotai is about 59%, and the amorphous morphology substance in it is about 41%. SEM and AFM detection suggests that Zuotai is a kind of ancient micro-nano drug, and its particle size is mainly in the range of 100-600 nm, even less than 100 nm, which commonly further aggregate into several to 30 µm loose amorphous particles. In summary, the present study elucidated physicochemical characterization(elements composition, coordination information of mercury, phase composition and micro-morphology) of Zuotai, and it will play a positive role in promoting the interpretation of this mysterious drug.

Recycling application of Li-MnO₂ batteries as rechargeable lithium-air batteries.

The ever-increasing consumption of a huge quantity of lithium batteries, for example, Li-MnO2 cells, raises critical concern about their recycling. We demonstrate herein that decayed Li-MnO2 cells can be further utilized as rechargeable lithium-air cells with admitted oxygen. We further investigated the effects of lithiated manganese dioxide on the electrocatalytic properties of oxygen-reduction and oxygen-evolution reactions (ORR/OER). The catalytic activity was found to be correlated with the composition of Li(x)MnO2 electrodes (0<x<1) generated in situ in aprotic Li-MnO2 cells owing to tuning of the Mn valence and electronic structure. In particular, modestly lithiated Li(0.50)MnO2 exhibited superior performance with enhanced round-trip efficiency (ca. 76%), high cycling ability (190 cycles), and high discharge capacity (10,823 mA h g(carbon)(-1)). The results indicate that the use of depleted Li-MnO2 batteries can be prolonged by their application as rechargeable lithium-air batteries.

Recycling Application of Li–MnO2 Batteries as Rechargeable Lithium–Air Batteries

AbstractThe ever‐increasing consumption of a huge quantity of lithium batteries, for example, Li–MnO2 cells, raises critical concern about their recycling. We demonstrate herein that decayed Li–MnO2 cells can be further utilized as rechargeable lithium–air cells with admitted oxygen. We further investigated the effects of lithiated manganese dioxide on the electrocatalytic properties of oxygen‐reduction and oxygen‐evolution reactions (ORR/OER). The catalytic activity was found to be correlated with the composition of LixMnO2 electrodes (0&lt;x&lt;1) generated in situ in aprotic Li–MnO2 cells owing to tuning of the Mn valence and electronic structure. In particular, modestly lithiated Li0.50MnO2 exhibited superior performance with enhanced round‐trip efficiency (ca. 76 %), high cycling ability (190 cycles), and high discharge capacity (10 823 mA h gcarbon−1). The results indicate that the use of depleted Li–MnO2 batteries can be prolonged by their application as rechargeable lithium–air batteries.