Negative ion photoelectron spectroscopy of N2O− and (N2O)−2

We have recorded the photoelectron spectra of the gas phase negative ions N₂O⁻ and (N₂O)₂⁻ both of which were prepared in a nozzle ion source. The shift between the maxima of the two spectra is interpreted in terms of the dissociation energy of the dimer ion.     

Thermal stability of ZrO2–SiO2 aerogel modified by Fe(III) ion

ZrO₂–SiO₂ aerogel modified by Fe(III) ion was prepared and the stability of the samples under high temperature was investigated. The structure and properties of modified aerogels were characterized by N₂ adsorption–desorption, FT-IR, XRD and TEM. The samples still contain a specific surface area about 228 m²/g after 1,000 °C 0.5 h calcinations. The inhibition of ZrO₂ particle growth is attributed to the Fe(III) ion modified aerogel surface, which strongly retards the ZrO₂ tetragonal phase transformation as well.     

Ab Initio rovibrational spectrum of the NaH2 + ion–quadrupole complex

The electronic and rovibrational structure of (¹A₁) NaH₂ ⁺ has been investigated using a relativistically-corrected, all-electron coupled-cluster with singles, doubles and perturbative triples (CCSD(T)) ansatz. For the electronic ground state this ansatz yielded equilibrium Na–H bond lengths (R _e ) of 2.4208 Å and an equilibrium H–Na–H bond angle (θ_e) of 17.8°. An analytical potential energy surface (PES) was embedded in the rovibrational Hamiltonian. The PES was constructed using 118 CCSD(T) points and exhibited a residual error of 1.2 cm^?1. The rovibrational Hamiltonian was diagonalised using variational techniques. The vibrational and rovibrational eigenvectors were assigned using a configuration weight scheme in terms of normal modes and the Mulliken assignment scheme, respectively. For the ground vibrational state of (¹A₁) NaH₂ ⁺, the vibration-averaged bond lengths 〈R〉 and angle 〈θ〉 were 2.4995 Å and 17.1°, respectively. The ab initio (¹A₁) NaH₂ ⁺ PES yielded a dissociation energy (D ₀) value of 10.3 kJ mol^?1, which is in excellent agreement with the experimental value of 10.3 ± 0.8 kJ mol^?1 (Bushnell et al. in J Phys Chem 98:2044, 1994). An analytical dipole moment surface was constructed using 90 CCSD(T) points. Rovibrational spectra of (¹A₁) NaH₂ ⁺, (¹A′) NaHD⁺ and (¹A₁) NaD₂ ⁺ for v ≤ 10, J ≤ 5 were constructed using rovibrational transition moment matrix elements calculated in a novel manner that employs the analytical dipole moment surface (DMS). The rovibrational structure of the Na⁺–H₂ v _HH = 1 ← v _HH = 0 band was calculated and compared to that of Li⁺–H₂.     

The electronic structure of the SbF2−5 ion and isoelectronic species

The electronic structure of the SbF²⁻₅ion and the isoelectronic species TeF⁻₅, IF₅ and XeF⁺₅ are calculated using the Discrete Variational X_α-method (DVM-X_α). The nature of chemical Bonding is analysed in terms of a Mulliken population scheme. The factors leading to geometrical distortions of the SbF²⁻₅ coordination polyhedron are discussed. The results of calculations cast doubts on the validity of the assumption that the geometry of the anion is influenced by the lone pair.     

Effects of BaCl_2 on slow vacuolar ion channels on radish by patch-clamp

Effects of BaCl2 on slow vacuolar ion channels on radish by patch-clamp YANG Pin (杨 频) & ZHANG Liping (张丽平) Institute of Molecular Science, Shanxi University, Taiyuan 030006, China Correspondence should be addressed to Yang Pin (email: yangpin@sxu.edu.cn)     

What determines MALDI ion yields? A molecular dynamics study of ion loss mechanisms

Ion recombination in matrix-assisted laser desorption/ionization (MALDI) is as important as any ion formation process in determining the quantity of ions observed but has received comparatively little attention. Molecular dynamics simulations are used here to investigate some models for recombination, including a Langevin-type model, a soft threshold model and a tunneling model. The latter was found to be superior due to its foundations in a widespread physical phenomenon, and its lack of excessive sensitivity to parameter choice. Tunneling recombination in the Marcus inverted region may be a major reason why MALDI is a viable analytical method, by allowing ion formation to exceed ion loss on the time scale of the plume expansion. Ion velocities, photoacoustic transients and pump-probe measurements might be used to investigate the role of recombination in different MALDI matrices, and to select new matrices.     

Real-time 2D separation by LC × differential ion mobility hyphenated to mass spectrometry

The liquid chromatography–mass spectrometry (LC-MS) analysis of complex samples such as biological fluid extracts is widespread when searching for new biomarkers as in metabolomics. The success of this hyphenation resides in the orthogonality of both separation techniques. However, there are frequent cases where compounds are co-eluting and the resolving power of mass spectrometry (MS) is not sufficient (e.g., isobaric compounds and interfering isotopic clusters). Different strategies are discussed to solve these cases and a mixture of eight compounds (i.e., bromazepam, chlorprothixene, clonapzepam, fendiline, flusilazol, oxfendazole, oxycodone, and pamaquine) with identical nominal mass (i.e., m/z 316) is taken to illustrate them. Among the different approaches, high-resolution mass spectrometry or liquid chromatography (i.e., UHPLC) can easily separate these compounds. Another technique, mostly used with low resolving power MS analyzers, is differential ion mobility spectrometry (DMS), where analytes are gas-phase separated according to their size-to-charge ratio. Detailed investigations of the addition of different polar modifiers (i.e., methanol, ethanol, and isopropanol) into the transport gas (nitrogen) to enhance the peak capacity of the technique were carried out. Finally, a complex urine sample fortified with 36 compounds of various chemical properties was analyzed by real-time 2D separation LC×DMS-MS(/MS). The addition of this orthogonal gas-phase separation technique in the LC-MS(/MS) hyphenation greatly improved data quality by resolving composite MS/MS spectra, which is mandatory in metabolomics when performing database generation and search.     

2D polyaniline with exchangeable interlayer fluid for fast and stable volumetric dual ion storage

Two-dimensional(2D) layered materials are widely applied in energy devices including lithium-ion battery and supercapacitor due to their unique properties,such as tunable interlayer structure,numerous active sites,large aspect ratio versatile interlayer chemistry.In this work,2D layered tungstate acidlinked polyaniline(TALP) presented a fluid-in-solid structure,which allowed facile exchange of the interlayer fluid from moisture to conventional Li⁺ containing electrolyte.With fast and stable dual ion storage(Li⁺ and PF₆^-),TALP demonstrates high-rate volumetric capacity(39 mAh cm_-3 at 2000 mA g^-1) and good stability(2000 cycles at 200 mA g^-1) within the working potential window of 1.5-4.5 V versus Li⁺/Li.     

β-MnO2 with proton conversion mechanism in rechargeable zinc ion battery

Rechargeable aqueous zinc ion battery(RAZIB)is a promising energy storage system due to its high safety,and high capacity.Among them,manganese oxides with low cost and low toxicity have drawn much attention.However,the under-debate proton reaction mechanism and unsatisfactory electrochemical performance limit their applications.Nanorod b-MnO₂ synthesized by hydrothermal method is used to investigate the reaction mechanism.As cathode materials for RAZIB,the Zn//b-MnO₂ delivers 355 mA h g^-1(based on cathode mass)at0.1 A g^-1,and retain 110 mA h g^-1 after 1000 cycles at 0.2 A g^-1.Different from conventional zinc ion insertion/extraction mechanism,the proton conversion and Mn ion dissolution/deposition mechanism of b-MnO₂ is proposed by analyzing the evolution of phase,structure,morphology,and element of b-MnO₂ electrode,the pH change of electrolyte and the determination of intermediate phase MnO OH.Zinc ion,as a kind of Lewis acid,also provides protons through the formation of ZHS in the proton reaction process.This study of reaction mechanism provides a new perspective for the development of Zn//MnO₂ battery chemistry.     

Gallium-based anodes for alkali metal ion batteries

Alkali metal ion batteries(AMIBs)are playing an irreplaceable part in the energy revolution,due to their intrinsic advantages of large capacity/power density and abundance of alkali metal ions in the earth’s crust.Despite their great promise,the inborn deficiencies of commercial graphite and other anodes being researched so far call for the quest of better alternatives that exhibit all-round performance with the balance of energy/power density and cycling stability.Gallium-based materials,with impressive capacity utilization and self-healing ability,provide an anticipated solution to this conundrum.In this review,an overview on the recent progress of gallium-based anodes and their storage mechanism is presented.The current strategies used as engineering solutions to meet the scientific challenges ahead are discussed,in addition to the insightful outlook for possible future study.     

Negative ion photoelectron spectroscopy of teo−

We have recorded the photoelectron spectrum of Te0⁻ using a hot-cathode discharge ion source and a negative ion photoelectron spectrometer. The adiabatic electron affinity of TeO is determined to be 1.697±0.022 eV. The negative ion parameters determined in this work are: (w_e″(TeO⁻) = 690 ± 80 cm⁻¹, r_e″(TeO⁻) = 1.884 ± 0.028 Å. and D_o     

Field asymmetric waveform ion mobility spectrometry studies of proteins: Dipole alignment in ion mobility spectrometry?

Approaches to separation and characterization of ions based on their mobilities in gases date back to the 1960s. Conventional ion mobility spectrometry (IMS) measures the absolute mobility, and field asymmetric waveform IMS (FAIMS) exploits the difference between mobilities at high and low electric fields. However, in all previous IMS and FAIMS experiments ions experienced an essentially free rotation; thus the separation was based on the orientationally averaged cross-sections Omega(avg) between ions and buffer gas molecules. Virtually all large ions are permanent electric dipoles that will be oriented by a sufficiently strong electric field. Under typical FAIMS conditions this will occur for dipole moments >400 D, found for many macroions including most proteins above approximately 30 kDa. Mobilities of aligned dipoles depend on directional cross-sections Omega(dir) (rather than Omega(avg)), which should have a major effect on FAIMS separation parameters. Here we report the FAIMS behavior of electrospray-ionization-generated ions for 10 proteins up to approximately 70 kDa. Those above 29 kDa exhibit a strong increase of mobility at high field, which is consistent with predicted ion dipole alignment. This effect expands the useful FAIMS separation power by an order of magnitude, allowing separation of up to approximately 10(2) distinct protein conformers and potentially revealing information about Omega(dir) and ion dipole moment that is of utility for structural characterization. Possible approaches to extending dipole alignment to smaller ions are discussed.     

Tropylium ion mediated α-cyanation of amines

Tropylium ion mediated α-cyanation of amines is described. Even in the presence of KCN, tropylium ion is capable of oxidizing various amine substrates, and the resulting iminium ions undergo salt metathesis with cyanide ion to produce aminonitriles. The byproducts of this transformation are simply cycloheptatriene, a volatile hydrocarbon, and water-soluble potassium tetrafluoroborate. Thirteen total substrates are shown for the α-cyanation procedure, including a gram scale synthesis of 17β-cyanosparteine. In addition, a tropylium ion mediated oxidative aza-Cope rearrangement is demonstrated.     

Reactions involving fluoride ion. Part 37. ‘Proton Sponge’ hydrofluoride as a fluoride ion donor

‘Proton Sponge’ hydrofluoride has been prepared and is totally soluble in acetonitrile; this system has been used to generate carbanions from hexafluoropropene and to form carbon-fluorine bonds by reaction with both 2,4,6-trichloropyrimidine and benzoyl chloride.     

Effect of the porosity of PS–DVB-copolymers on ion chromatographic behavior in inverse size-exclusion and ion chromatography

Small and highly pressure-stable PS-DVB copolymers of different porosity had been prepared by a two-step swelling procedure which enabled variation of diluent composition, an important characteristic affecting the porosity. The polymers were characterized by inverse size-exclusion chromatography and scanning electron microscopy. Subsequent chloromethylation and amination resulted in anion exchangers suitable for ion chromatography.The pore volume and the pore-size distribution is substantially affected by the fraction of the solvens component in the diluent. It was apparent from scanning electron microscopy that surface structure and the size of the polymer particles was not affected by diluent composition. The functionalization process led to a decrease in pore volume. The pore-size distribution remained unchanged during functionalization, which can be explained in terms of partial closing of all pore sizes. The chromatographic efficiency of the functionalized polymers in ion chromatography was highly dependent on diluent composition and the extent of functionalization was determined by the total pore volume.The composition of the diluent is an excellent tool for optimization of polymers used for the synthesis of surface-functionalized anion exchangers.     

Bioadsorption and ion exchange of Cr3+ and Pb2+ solutions with algae

Heavy metals can be removed from effluents and recovered using physico-chemical mechanisms as biosorption processes. In this work “Arribada” seaweed biomass was employed to assess its biosorptive capacity for the chromium (Cr³⁺) and lead (Pb²⁺) cations that usually are present in waste waters of plating industries. Equilibrium and kinetic experiments were conducted in a mixed reactor on a batch basis. Biosorption equilibrium and fluid-solid mass transfer constants data were analyzed through the concept of ion exchange sorption isotherm. The respective equilibrium exchange constants (K _eqCr=173.42, K _eqPb=58.86) and volumetric mass transfer coefficients ((k _mCr a)′=1.13×10⁻³ s⁻¹, (k _mPb a)′=0.89×10⁻³ s⁻¹) were employed for the dynamic analysis of Cr and Pb sorption in a fixed-bed flow-through sorption column. The breakthrough curves obtained for both metals were compared with the predicted values by the heterogeneous model (K _eqCr=171.29, K _eqPb=60.14; k _mCr a=7.81×10⁻² s⁻¹, k _mPb a=2.43×10⁻² s⁻¹), taking into account the mass transfer process. The results suggest that these algae may be employed in a metal removal/recovery process at low cost. An erratum to this article can be found at     

Synthesis of γ-LiV2O5 nanorods as a high-performance cathode for Li ion battery

One-dimension γ-LiV₂O₅ nanorods were synthesized using VO₂(B) nanorods as precursor in this study. The as-prepared material is characterized by X-ray diffraction, X-ray photoelectron spectrometry, Fourier-transform infrared, transmission electron microscopy (TEM), cyclic voltammetry, and charge–discharge cycling test. TEM results show that LiV₂O₅ nanorods are 90–250 nm in diameter. The nanorods deliver a maximum discharge capacity of 284.3 mAh g^?1 at 15 mA g^?1 and 270.2 mAh g^?1 is maintained at the 15th cycle. Good rate performance is also observed with the discharge capacity of 250.1 and 202.6 mAh g^?1 at 50 and 300 mA g^?1, respectively. The capacity retention at 300 mA g^?1 is 84.2% over 50 cycles. The Li⁺ diffusion coefficient of LiV₂O₅ is calculated to be 10^-10–10^?9 cm² s^?1. It is demonstrated that the nanorod morphology could greatly facilitate to shorten lithium ion diffusion pathways and increase the contact area between active material and electrolyte, resulting in high capacity and rate performance for LiV₂O₅.     

Study of ion transport across an amphoteric ion exchange membrane — general transport properties of a simple electrolyte

Basic electrochemical properties of an amphoteric ion-exchange membrane (1.0—PA—29), in which almost equal numbers of cationic and anionic sites are distributed homogeneously over the functionalized polymer networks, were studied for a variety of concentration-cell systems. Unlike the usual uniform ion-exchange membrane, potentiometric permselectivities were demonstrated even for ions of the same charge, as shown by the result that distinctive potential responses were observed for a series of alkali metal chloride, sodium salt, and tetra-alkylammonium chloride systems. The sequence of membrane permeabilities to cations and anions calculated from the electrochemical data could well be correlated to the sequence of the hydrated radii of the respective ions. So the potentiometric responses to any electrolyte system can be predicted from the permeability data or hydrated radius values of individual cations and anions. The present results suggest that the homogeneous amphoteric ion-exchange membrane functions effectively as an ion sieve, sifting out the sizes of permeating hydrated cations and anions.     

The distonic ion ·CH2CH2CH+OH,keto ion CH3CH2CH=O +·, enol ion CH3CH=CHOH+·, and related C3H6O+· radical cations. Stabilities and isomerization proclivities studied by dissociation and neutralization-reionization

Metastable ion decompositions, collision-activated dissociation (CAD), and neutralization-reionization mass spectrometry are utilized to study the unimolecular chemistry of distonic ion ^·CH₂CH₂CH^?OH (2^+·) and its enol-keto tautomers CH₃CH=CHOH^?· (1 ^+·) and CH₃CH₂CH=O ^+· (3^+·). The major fragmentation of metastable 1^+·–3^+· is H^· loss to yield the propanoyl cation, CH₃CH₂C≡O⁺. This reaction remains dominant upon collisional activation, although now some isomeric CH₂=CH-CH⁺ OH is coproduced from all three precursors. The CAD and neutralization-reionization (⁺NR⁺) spectra of keto ion 3 ^+· are substantially different from those of tautomers 2^+· and 1^+·. Hence, 3^+· without sufficient energy for decomposition (i. e. , “stable” 3^+·) does not isomerize to the ther-modynamically more stable ions 2^+· or 1^+·, and the 1,4-H rearrangement H-CH₂CH₂CH=O^+·(3 ^+·) → CH₂CH₂CH⁺ O-H (2 ^+·) must require an appreciable critical energy. Although the fragment ion abundances in the ⁺ NR ⁺ (and CAD) spectra of 1 ^+· and 2 ^+· are similar, the relative and absolute intensities of the survivor ions (recovered C₃H₆O^+· ions in the ⁺NR⁺ spectra) are markedly distinct and independent of the internal energy of 1 ^+· and 2 ^+·. Furthermore, 1 ^+· and 2 ^+· show different MI spectra. Based on these data, distonic ion 2 ^+· does not spontaneously rearrange to enol ion 1 ^+· (which is the most stable C₃H₆O^+· of CCCO connectivity) and, therefore, is separated from it by an appreciable barrier. In contrast, the molecular ions of cyclopropanol (4 ^+·) and allyl alcohol (5 ^+·) isomerize readily to 2 ^+·, via ring opening and 1,2-H^? shift, respectively. The sample found to generate the purest 2 ^+· is α-hydroxy-γ-butyrolactone. Several other precursors that would yield 2 ^+· by a least-motion reaction cogenerate detectable quantities of enol ion 1 ^+·, or the enol ion of acetone (CH₂=C(CH₃)OH^+·, 6 ^+·), or methyl vinyl ether ion (CH₃OCH=CH ₂ ^+· , 7 ^+·). Ion 6 ^+· is coproduced from samples that contain the —CH₂—CH(OH)—CH₂— substructure, whereas 7 ^+· is coproduced from compounds with methoxy substituents. Compared to CAD, metastable ion characteristics combined with neutralization-reionization allow for a superior differentiation of the ions studied.     

He 2++ molecular ion in a strong time-dependent magnetic field: a current-density functional study

The He molecular ion exposed to a strong ultrashort time‐dependent (TD) magnetic field of the order of 10⁹ G is investigated through a quantum fluid dynamics (QFD) and current‐density functional theory (CDFT) based approach using vector exchange‐correlation (XC) potential and energy density functional that depend not only on the electronic charge‐density but also on the current density. The TD‐QFD‐CDFT computations are performed in a parallel internuclear‐axis and magnetic field‐axis configuration at the field‐free equilibrium internuclear separation R = 1.3 au with the field‐strength varying between 0 and 10¹¹ G. The TD behavior of the exchange‐ and correlation energy of the He is analyzed and compared with that obtained using a [B‐TD‐QFD‐density functional theory (DFT)] approach based on the conventional TD‐DFT under similar computational constraints but using only scalar XC potential and energy density functional dependent on the electronic charge‐density alone. The CDFT based approach yields TD exchange‐ and correlation energy and TD electronic charge‐density significantly different from that obtained using the conventional TD‐DFT based approach, particularly, at typical magnetic field strengths and during a typical time period of the TD field. This peculiar behavior of the CDFT‐based approach is traced to the TD current‐density dependent vector XC potential, which can induce nonadiabatic effects causing retardation of the oscillating electronic charge density. Such dissipative electron dynamics of the He molecular ion is elucidated by treating electronic charge density as an electron‐“fluid” in the terminology of QFD. © 2011 Wiley Periodicals, Inc. J Comput Chem, 2011