Application of TOF-SIMS Method in the Study of Wetting the Iron (111) Surface with Promoter Oxides

In the present work, a simplified model of the Fe(111) surface’s promoter-oxide system was investigated in order to experimentally verify the previously proposed and known models concerning the structure and chemical composition of the surfaces of iron nanocrystallites in the ammonia-synthesis catalyst. It was shown that efficient oxygen diffusion from metal oxides to the clean Fe(111) iron surface took place even at temperatures lower than 100 °C. The effective wetting of the iron surface by potassium oxide is possible when the surface is covered with oxygen at temperatures above 250 °C. In the TOF-SIMS spectra of the surface of iron wetted with potassium, an emission of secondary FeOK⁺ ions was observed that implies that potassium atoms are bound to the iron surface atoms through oxygen. As a result of further wetting the iron surface with potassium ions, a heterogeneous surface structure was formed consisting of a thin K₂O layer, next to which there was an iron-oxide phase covered with potassium ions. Only a limited increase in calcium concentration was observed on the Fe(111) iron surface upon sample annealing at up to 350 °C. As a result of wetting the iron surface with calcium ions, an oxide solution of CaO-Fe_xO_y was formed. In the annealing process of the sample containing alumina, only traces of this promoter diffusing to the iron surface were observed. Alumina formed a solution with a passive layer on the iron surface and under the process conditions (350 °C) it did not wet the pure iron (111) surface. The decrease in Fe⁺-ion emission from the Fe-Ca and Fe-Al samples at 350 °C implies a reduction in the oxygen concentration on the sample surface at this temperature.     

Zundel‐like and Eigen‐like Hydrated Protons on a Platinum Surface

The nature of hydrated protons is an important topic in the fundamental study of electrode processes in acidic environment. For example, it is not yet clear whether hydrated protons are formed in the solution or on the electrode surface in the hydrogen evolution reaction on a Pt electrode. Using mass spectrometry and infrared spectroscopy, we show that hydrogen atoms are converted into hydrated protons directly on a Pt(111) surface coadsorbed with hydrogen and water in ultrahigh vacuum. The hydrated protons are preferentially stabilized as multiply hydrated species (H₅O₂⁺ and H₇O₃⁺) rather than as hydronium (H₃O⁺) ions. These surface‐bound hydrated protons may play an important role in the interconversion between adsorbed hydrogen atoms and solvated protons in solution.     

Fragmentation of protonated O,O-diethyl O-aryl phosphorothionates in tandem mass spectral analysis

The gas-phase ion chemistry of protonated O,O-diethyl O-aryl phosphorothionates was studied with tandem mass spectrometric and ab initio theoretical methods. Collision-activated dissociation (CAD) experiments were performed for the [M+H]⁺ ions on a triple quadrupole mass spectrometer. Various amounts of internal energy were deposited into the ions upon CAD by variation of the collision energy and collision gas pressure. In addition to isobutane, deuterated isobutane C₄D₁₀ also was used as reagent gas in chemical ionization. The daughter ions [M+H?C₂H₄]⁺ and [M+H?2C₂H₄]⁺ dominate the CAD spectra. These fragments arise via various pathways, each of which involves γ-proton migration. Formation of the terminal ions [M+H?2C₂H₄?H₂O]⁺, [M+H?2C₂H₄?H₂S]⁺, [ZPhOH₂]⁺, [ZPhSH₂]⁺, and [ZPhS]⁺ [Z = substituent(s) on the benzene ring] suggests that (1) the fragmenting [M+H]⁺ ions of O,O-diethyl O-aryl phosphorothionates have protons attached on the oxygen of an ethoxy group and on the oxygen of the phenoxy group; (2) thiono-thiolo rearrangement by aryl migration to sulfur occurs; (3) the fragmenting rear-ranged [M+H]⁺ ions have protons attached on the oxygen of an ethoxy group and on the sulfur of the thiophenoxy group. To get additional support for our interpretation of the mass spectrometric results, some characteristics of three protomers of O,O-diethyl O-phenyl phosphorothionate were investigated by carrying out ab initio molecular orbital calculations at the RHF/3–21G* level of theory.     

A mesoporous non-precious metal boride system: synthesis of mesoporous cobalt boride by strictly controlled chemical reduction

Generating high surface area mesoporous transition metal boride is interesting because the incorporation of boron atoms generates lattice distortions that lead to the formation of amorphous metal boride with unique properties in catalysis. Here we report the first synthesis of mesoporous cobalt boron amorphous alloy colloidal particles using a soft template-directed assembly approach. Dual reducing agents are used to precisely control the chemical reduction process of mesoporous cobalt boron nanospheres. The Earth-abundance of cobalt boride combined with the high surface area and mesoporous nanoarchitecture enables solar-energy efficient photothermal conversion of CO₂ into CO compared to non-porous cobalt boron alloys and commercial cobalt catalysts.

Generating high surface area mesoporous transition metal boride is challenging but interesting because incorporation of boron atoms can generate lattice distortion to form amorphous metal boride which has unique properties in catalysis.     

Complexes of iron(II) with cysteine-containing peptides in the gas phase

Gas-phase interactions of peptides that contain cysteine with iron(II) atoms were examined by using fast-atom bombardment and tandem mass spectrometry. Specific and strong interactions of iron and sulfur from the thiol group of the cysteine side chain occur in the gas phase and are the basis for highly specific fragmentation to give abundant [a _n ?⁺ ions. For peptides that contain two cysteines, an internal ion, which results from the interaction of Fe and both thiol groups, is formed upon collisional activation. The mechanism for the formation of [a _n ?2H+Fe]⁺ fragment ions requires the metal to be coordinated at sulfur in close proximity to the site of reaction. Iron-bis(pentapeptide) complexes, which form under the same conditions, decompose predominantly to lose a pentapeptide molecule and, to a lesser extent, to give [a _a ?2H+Fe]⁺ ions.     

Theoretical prediction of a new noncluster lithium boride Li<Subscript>1 − <Emphasis Type="Italic">x</Emphasis></Subscript>B<Subscript>9</Subscript> with one-dimensional ionic and two-dimensional electronic conductivity in mutually perpendicular directions

Based on the features of the structure of B₅H₁₁ and other known boranes, the possibility of the existence of a new structure type—LiB₉ (hexagonal, space group P6₃ cm, a = 0.565 nm, c = 0.504 nm, Z = 2, d = 2.49 g/cm³)—was predicted. The basal plane contains perforated deltahedral layers of boron atoms with delocalized electrons combined into a framework by fixed 3c2e bonds. Discrete, almost cylindrical channels accommodating Li⁺ cations are perpendicular to the layers. Thermal or electrochemical removal of part of lithium should be favorable for the appearance or buildup of the cationic conductivity with the possible intermediate formation of lithium incommensurate phase. Valence-scheme analysis of boride layers revealed low-barrier hole bipolaron conductivity within the layers and considerable hindrance to interlayer electron transport.     

Ion-etching of discharge-produced tetrafluoroethylene film with hydrogen,oxygen and noble gases. A mass spectrometric analysis

Freshly deposited discharge-produced tetrafluoroethylene films were ion-etched with either helium, neon, argon, oxygen or hydrogen. The ions C⁺, CF⁺, CF₂⁺ and CF₃⁺ comprised most of the positive ions in rare gas discharges, with CF⁺ always dominant. Sputtered fragments containing two or more carbon atoms were rare. These findings are compatible with the ion-etching of a highly crosslinked polymer film. Residual background gases were contributed to 1–3% of the total ion flux even though their actual partial pressures were very low. The concentration of neutral species corresponding to the ions observed was less than one part in ten thousand of the etching gas. With pure hydrogen, very little etching occurred and the degree of ionization relative to the rare gases was low. The principal reaction was the abstraction of fluorine from the polymer to give hydrogen fluoride and a more highly crosslinked film. Oxygen containing discharges produced the largest total yield of all the systems studied and the most evidence of chemical attack on the polymer. The ions observed were CO⁺, CO₂⁺, COF⁺, COF₂⁺ as well as C⁺, CF⁺, CF₂⁺ and CF₃⁺. Thus oxygen etches the polymer by preferentially attacking the carbon-carbon framework.     

Ion formation processes in the afterpeak time regime of pulsed glow discharge plasmas

The formation of ions following the termination of power in a pulsed glow discharge ion source is investigated. The populations of ionized species containing sputtered atoms M⁺, M ₂ ¹ :, and MAr⁺ are observed to maximize after the termination of discharge power. Collisions involving sputtered atoms and metastable argon atoms, Penning and associative ionization, are considered to be responsible for the formation of ions in the discharge afterpeak time regime. The domination of these ion formation processes during the afterpeak time regime is supported by the results from investigations of discharge operating parameters, metastable argon atom quenching, and ion kinetic energy distributions.     

Effects of oxygen addition to argon glow discharges: A hybrid Monte Carlo-fluid modeling investigation

A hybrid model is developed for describing the effects of oxygen addition to argon glow discharges. The species taken into account in the model include Ar atoms in the ground state and the metastable level, O₂ gas molecules in the ground state and two metastable levels, O atoms in the ground state and one metastable level, O₃ molecules, Ar⁺, O⁺, O₂⁺ and O^? ions, as well as the electrons. The hybrid model consists of a Monte Carlo model for electrons and fluid models for the other plasma species. In total, 87 different reactions between the various plasma species are taken into account. Calculation results include the species densities and the importance of their production and loss processes, as well as the dissociation degree of oxygen. The effect of different O₂ additions on these calculation results, as well as on the sputtering rates, is discussed.     

Dissociation of polyatomic ions in the inductively coupled plasma

A general method for identifying the origin of a particular polyatomic ion is described. Based on a postulated dissociation reaction, measured ion signal ratios (e.g. Ar₂⁺/Ar⁺) are combined with mass bias corrections and estimates of the density of the neutral product (usually Ar, O or H atoms) to determine a gas kinetic temperature T_gas. The temperature can also be measured by the reduction in pressure when the ICP is sampled (compared to room temperature argon), or by other means. Dissociation energies and spectroscopic constants for the ions are necessary. For the particular instrument used, some of the findings of this study are: (a) ArO⁺ and ArN⁺ can be either dissociated (if the plasma potential is high) or created (if the plasma potential is low) by collisions between the sampler and skimmer; (b) the strongly-bound oxide ions O₂⁺ and MO⁺ for the rare earths are observed at levels consistent with T_gas ∼5300 K in a ‘hot’ plasma, but ClO⁺ is formed in excess; and (c) the abundances of most other polyatomic ions like H₂O⁺ and ArH⁺ correspond to higher densities than would be expected in the ICP itself.     

Argon sensitized formation of Xe+2: A new mechanism for the Jesse effect

Photoexcitation of the argon resonance states in the presence of xenon leads to Xe⁺₂. Kinetic analysis indicates rapid near-resonant energy transfer between argon and xenon atoms. The possibility of an analogous mechanism in other rare gas systems is examined.     

Syntheses and Structures of μ-Oxo-Bis[dichloroiron(III)]-Bis-[2,6-Diacetylpyridinedioximate(-1)]Iron(II) and Related Compounds

The syntheses and structures of four new compounds are described. Two of these compounds are the anhydrous and dihydrate chloride salts of the diamagnetic bis(2,6-diacetylpyridinedioxime)iron(II) cation, [Fe(DAPDH₂)₂]²⁺. In this complex cation the DAPDH₂ ligand binds to the iron, as expected, through its three nitrogen atoms leaving the four oxime oxygen atoms protonated and uncoordinated. The third compound is (AsPh₄)₂[Fe₂OCl₆], a new salt of the well-known oxo-bridged diiron complex, [Fe₂OCl₆]^2?. The synthesis of (AsPh₄)₂[Fe₂OCl₆] is a high yield, straightforward, one-step preparation starting with AsPh₄Cl and ferrous chloride in methanol. In this synthesis Fe(II) is oxidized to Fe(III) by atmospheric O₂. The fourth new compound is the novel and unexpected triiron complex [Fe(DAPDH)₂Fe₂OCl₄]. This complex is derived from [Fe(DAPDH₂)₂)]²⁺ and [Fe₂OCl₆]^2? by removing the H⁺ from each of two adjacent oxime oxygen atoms of the former and one Cl^? from each of the Fe(III) ions of the latter. The resulting neutral fragments, Fe(DAPDH)₂ and Fe₂OCl₄, are joined via bonds linking the two oxime oxygen atoms to the two Fe(III) ions giving rise to an unusual eight membered chelate ring containing three iron ions, two nitrogen atoms and three oxygen atoms, one of which is the bridge between the two Fe(III) ions.     

Molecular ionization-dissociation of fluoranthene at 266 nm: Energetic and dissociative pathways

Experimental studies have been carried out for nanosecond 266-nm laser-induced photoionization and dissociation of fluoranthene, C₁₆H₁₀ with pulse energies from 0.5 to 20 mJ using a time of flight mass spectrometer. The fragmentation patterns have been characterized and discussed with respect to the number of absorbed photons. They fall into three regimes. The first regime involves low energy processes, where the molecular parent ion promptly dissociates, resulting in the formation of Cm⁺Hn(m=11−15) by a process where up to two photons are absorbed. The second regime involves intermediate energy, where dissociative processes are activated by up to three-photon absorption and produce a second group of daughter ions: C10⁺Hn, C₉⁺Hn, and C₈⁺Hn. Finally, there is a third dissociative process, characterized by the absorption of up to four photons, producing C₇⁺Hn, C₆⁺Hn, C₅⁺Hn, C₄⁺Hn, and C₃⁺Hn. Most of the detected ions are of the form Cm⁺Hn with m < n. Total deprotonation has also been observed. The mechanism proposed involves the dissociation of the parent ion, which then dissociates by different competitive channels. Helium, neon and argon were used as carrier gases (CG). A detailed discussion is presented regarding the use of He as the CG. The laser pulse intensity allows the absorption of up to nine photons, observed through the formation of multiply charged ions of some of the CG atoms.     

Ion–molecule reactions and dissociation of glycols in a quadrupole ion trap mass spectrometer: Evidence of intramolecular interactions

Polyethylene glycols react with CH₃OCH₂⁺ ions from dimethyl ether to form [M + 13]⁺ products. The [M + 13]⁺ ions are stabilized by intramolecular interactions involving the internal ether oxygen atoms and the terminal methylene group. Collisionally activated dissociation (CAD), including MSⁿ and deuterium labeling experiments show that fragmentation reactions involving intramolecular cyclization are predominant. Scrambling of hydrogen and deuterium atoms in the ion-molecule reaction products is not indicated. The CAD spectra of the [M + 13]⁺ ions provide unambiguous assignment of the glycol size.     

Hybrid Monte Carlo — Fluid model for studying the effects of nitrogen addition to argon glow discharges

A computer model is developed for describing argon/nitrogen glow discharges. The species taken into account in the model include electrons, Ar atoms in the ground state and in the 4s metastable levels, N₂ molecules in the ground state and in six different electronically excited levels, N atoms, Ar⁺ ions, N⁺, N₂⁺, N₃⁺ and N₄⁺ ions. The fast electrons are simulated with a Monte Carlo model, whereas all other species are treated in a fluid model. 74 different chemical reactions are considered in the model. The calculation results include the densities of all the different plasma species, as well as information on their production and loss processes. The effect of different N₂ additions, in the range between 0.1 and 10%, is investigated.     

Accessibility of Lithium Cations in VSH-2 Zeotype: Structural Effects and Formation of Protonated Water Clusters

The accessibility of lithium cations in microporous vanadosilicate VSH-2Cs of composition Cs₂(VO)(Si₆O₁₄) ⋅ 3H₂O was investigated by Single Crystal X-ray Diffraction, Attenuated Total Reflection Fourier Transformed Infrared Spectroscopy and Density Functional Theory calculations. The topological symmetry of VSH-2Cs is described in space group Cmca. After Li-ion exchange, the structure of VSH-2Li adopted monoclinic symmetry (space group C2/c) with a=17.011(2) Å, b=8.8533(11) Å, c=12.4934(16) Å, β=91.677(4)°, V=1880.7(4) ų. The strong interactions between Li ions and oxygen-framework atoms drive the main deformation mechanism, which is based on cooperative rotation of SiO₄ and VO₅ units around their oxygen atoms that behave as hinges. Exchange of Cs⁺ by Li⁺ is incomplete and accompanied by the formation of protonated species to counterbalance the electrostatic charge. The incorporation of protons is mediated by the presence of water dimers in the structural channels. H₂O molecules in VSH-2Li account not only as “space-fillers” after the removal of large Cs ions but also mediate proton transfer to compensate the negative charge of the host vanadosilicate framework.     

Secondary effects in prompt charged particle activation analysis

The phenomenon of secondary excitation was observed during irradiation of thick targets of boron and gallium nitride with 2 MeV³He⁺ ions. This effect, though negligible during irradiation with protons or⁴He⁺ ions, becomes significant when highly exoergic reactions can occur.     

Cationic and anionic environments in LiTFSI-doped di-ureasils with application in solid-state electrochromic devices

Fourier Transform mid-infrared and Raman spectroscopies were used to investigate the cation/polymer, cation/urea bridge, cation/anion and hydrogen bonding interactions in poly(oxyethylene) (POE)/siloxane di-ureasil networks prepared by the sol–gel route and doped with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). Materials with compositions 200 ?n ? 5 (where n expresses the molar ratio OCH₂CH₂/Li⁺) were studied. The Li⁺ ions coordinate to the urea carbonyl oxygen atoms over the whole range of salt concentration considered. Bonding to the ether oxygen atoms of the POE chains occurs at n ? 40, although a significant fraction of the POE chains remain non-coordinated. In these high salt content samples, the cations interact with the anions forming contact ion pairs. “Free” ions are probably the main charge carriers at the room temperature conductivity maximum of these ormolytes.     

Molecular fragmentation on collision with protons for freon and propane molecules

In ab initio calculations, we determined the most probable routes of decomposition of the [CF₃Cl]⁺, [CF₂Cl₂]⁺, [CFCl₃]⁺, [CCl₄]⁺ molecular ions of freons and [C₃H₈]⁺ ions of hydrocarbons formed by collision of neutral molecules with protons with energies of the order of 10 keV. The calculated potential surface sections are compared on a qualitative level with the probability of various ion fragments in experiments on fragmentation. The role of the charge transfer dynamics between the proton and the molecule is discussed.     

Chemical ionization of fluorophenyl n-propyl ethers: Loss of propene from the metastable [M + D]+ ions

Chemical ionization (CI) mass spectrometry with the reagents D₂O, CD₃OD, and CD₃CN (given in order of increasing proton affinity) has been used to generate metastable [M + D]⁺ ions of a series of mono-, di-, and trifluorophenyl n-propyl ethers and analogs labeled with two deuterium atoms at the β position of the alkyl group. Loss of propene is the main reaction of the [M + D]⁺ ions, whereas dissociation with formation of propyl carbenium ions is of minor importance. The combined results reveal that the deuteron added in the CI process can be incorporated in the propene molecules as well as in the propyl carbenium ions. The extent to which the added deuteron is exchanged with the hydrogen atoms of the propyl group is markedly dependent on the position of the fluorine atom(s) on the ring and the exothermicity of the initial deuteron transfer. For 3-fluorophenyl n-propyl ether, exchange is not observed if D₂O is the CI reagent, and occurs only to a minor extent in the experiments with the CI reagents CD₃OD and CD₃CN. Similar results are obtained for the 3,5-difluoro- and 2,4,6-trifluorophenyl ethers, whereas significant exchange is observed prior to the dissociations of the [M + D]⁺ ions of the 4-fluoro- and 2,6-difluorophenyl n-propyl ethers, irrespective of the nature of the CI reagent. These results are discussed in terms of the occurrence of initial deuteron transfer either to the oxygen atom or the aromatic ring followed by formation of an ion/neutral complex of a fluorine-substituted molecule and a secondary propyl carbenium ion. Initial deuteron transfer to the oxygen atom is suggested to yield complexes that can react by exchange between the added deuteron and the hydrogen atoms of the original propyl group prior to dissociation. By contrast, initial deuteron transfer to the ring is suggested to lead to complexes that react further by loss of propene molecules containing only the hydrogen/deuterium atoms of the original propyl entity.