II), Ti Research Articles

A Mixed-Valence Ti(II)/Ti(III) Inverted Sandwich Compound as a Regioselective Catalyst for the Uncommon 1,3,5-Alkyne Cyclotrimerization.

The synthesis, structure, and catalytic activity of a Ti(II)/Ti(III) inverted sandwich compound are presented in this study. Synthesis of the arene-bridged dititanium compound begins with the preparation of the titanium(IV) precursor [TiCl2(MesPDA)(thf)2] (MesPDA = N,N'-bis(2,4,6-trimethylphenyl)-o-phenylenediamide) (2). The reduction of 2 with sodium metal results in species [{Ti(MesPDA)(thf)}2(μ-Cl)3{Na}] (3) in oxidation state III. To achieve the lower oxidation state II, 2 undergoes reduction through alkylation with lithium cyclopentyl. This alkylation approach triggers a cascade of reactions, including β-hydride abstraction/elimination, hydrogen evolution, and chemical reduction, to generate the Ti(II)/Ti(III) compound [Li(thf)4][(TiMesPDA)2(μ-η6: η6-C6H6)] (4). X-ray and EPR characterization confirms the mixed-valence states of the titanium species. Compound 4 catalyzes a mild, efficient, and regiospecific cyclotrimerization of alkynes to form 1,3,5-substituted arenes. Kinetic data support a mechanism involving a binuclear titanium arene compound, similar to compound 4, as the resting state. The active catalyst promotes the oxidative coupling of two alkynes in the rate-limiting step, followed by a rapid [4 + 2] cycloaddition to form the arene product. Computational analysis of the resting state for the cycloaddition of trimethylsilylacetylene indicates a thermodynamic preference for stabilizing the 1,3,5-arene within the space between the two [TiMesPDA] fragments, consistent with the observed regioselectivity.

On the Use of Ti3C2 T x MXene as a Negative Electrode Material for Lithium-Ion Batteries.

The pursuit of new and better battery materials has given rise to numerous studies of the possibilities to use two-dimensional negative electrode materials, such as MXenes, in lithium-ion batteries. Nevertheless, both the origin of the capacity and the reasons for significant variations in the capacity seen for different MXene electrodes still remain unclear, even for the most studied MXene: Ti3C2 T x . Herein, freestanding Ti3C2 T x MXene films, composed only of Ti3C2 T x MXene flakes, are studied as additive-free negative lithium-ion battery electrodes, employing lithium metal half-cells and a combination of chronopotentiometry, cyclic voltammetry, X-ray photoelectron spectroscopy, hard X-ray photoelectron spectroscopy, and X-ray absorption spectroscopy experiments. The aim of this study is to identify the redox reactions responsible for the observed reversible and irreversible capacities of Ti3C2 T x -based lithium-ion batteries as well as the reasons for the significant capacity variation seen in the literature. The results demonstrate that the reversible capacity mainly stems from redox reactions involving the T x -Ti-C titanium species situated on the surfaces of the MXene flakes, whereas the Ti-C titanium present in the core of the flakes remains electro-inactive. While a relatively low reversible capacity is obtained for electrodes composed of pristine Ti3C2 T x MXene flakes, significantly higher capacities are seen after having exposed the flakes to water and air prior to the manufacturing of the electrodes. This is ascribed to a change in the titanium oxidation state at the surfaces of the MXene flakes, resulting in increased concentrations of Ti(II), Ti(III), and Ti(IV) in the T x -Ti-C surface species. The significant irreversible capacity seen in the first cycles is mainly attributed to the presence of residual water in the Ti3C2 T x electrodes. As the capacities of Ti3C2 T x MXene negative electrodes depend on the concentration of Ti(II), Ti(III), and Ti(IV) in the T x -Ti-C surface species and the water content, different capacities can be expected when using different manufacturing, pretreatment, and drying procedures.

Microwave-assisted synthesis of Co(II), Ni(II), Ti(III), and Ti (IV) complexes of iminochromeno-pyrido-pyrimidine and in vitro antiproliferative effect against H460, MCF-7, and HCT116

The purpose of this paper is the synthesis of new metal complexes and their biological application. Four new transition metal complexes (2–5) were synthesized using conventional as well as microwave methods from 7-iminochromeno[4,3-d]pyrido[1,2-a]pyrimidin-6(7H)-one (1) and corresponding metal salts. Ligand 1 and metal complexes 2–5 were characterized by IR, 1H-NMR, 13 C-NMR, Mass spectroscopy and elemental analysis. The free ligand and the metal complexes have been tested for in vitro antiproliferative activity. The evaluation of the antiproliferative effects of compounds (1–5) on three tumor cell lines (H460, MCF-7, and HCT116) shows that all tested compounds have demonstrated moderate to pronounced antiproliferative and/or cytotoxic effect. The most active compounds were ligand 1 and metal complexes 3 and 5.

Seacraft hulls protection with Ti, Cu - biocide pigments

The main directions of creating new forms of anti-fouling coatings for hulls of sea vessels lie in the field of obtaining an optimal biocide or mixture of biocides. Copper (I) oxide and copper-containing compounds are currently used as the main biocide in such compositions. To obtain competitive biocides containing copper (I) oxide, it is necessary to use relatively cheap inert fillers. The authors proposed a method for producing pigments based on titanium (IV) phosphate and copper compounds that have toxic effect on marine microorganisms for use in coatings that prevent biofouling of ship hulls in seawater. It is shown that by varying the initial ratio of Cu (II) : Ti (III) in the composition of the pigment, the order of mixing, and the temperature of heat treatment of the pigment, it is possible to change the content of various copper compounds in the polymer matrix of titanium phosphate. The obtained samples were studied using the X-ray diffraction, differential scanning calorimetry, scanning electron microscopy methods and other. Thermal transformations of titanium (IV) phosphate samples containing copper in different oxidation states were studied by thermal synchronic analysis in air and nitrogen.The conditions for obtaining a pigment with a maximum content of copper (I) oxide, necessary for prolonged inhibition of fouling, were found. The ability of the compositions to leach copper and phosphate ions in distilled water and in water similar in composition to seawater, depending on the conditions of heat treatment, was studied. Evaluation tests of the biocidal activity of the obtained pigments in relation to ciliates Tetrachimena piriformis and test cultures of bacteria Staphylococcus aureus, Bacillus subtilis were carried out.

The effect of metals and metal oxides on biodiesel oxidative stability from promotion to inhibition

Biodiesel, usually the methyl esters of plant oils or other triacylglycerol-containing materials, has become an established alternative to conventional, petroleum-derived diesel fuel. Several technical problems persist when using biodiesel, one of which is oxidation stability upon exposure to oxygen in air. Factors affecting oxidation stability are not only the composition of the fuel with polyunsaturated fatty acid methyl esters being more susceptible to oxidation but also temperature, presence of light, storage headspace, and presence of extraneous materials such as pro- and antioxidants, metals, and other substances. In case of metals, it has been stated/shown that some metals are especially effective in promoting oxidation of biodiesel, especially copper. In this work, studies on the effect of metals are expanded to include a total of 26 metals for their effect on biodiesel in form of soybean oil methyl esters. The metals included in this study are Ag, Al, Au, Co, Cr, Cu, Fe, In, Mg, Mn, Mo, Nb, Ni, Pd, Re, Rh, Ru, Sc, Si, Sn, Ta, Ti, V, W, Zn and Zr. Besides these neat metals, the oxides of 29 metals were studied. These oxides are those of Ag (I), Ag (II), Al (III), Au (III), Ba (II), Ca (II), Co, Cr (III), Cr (VI), Cu (II), Eu (III), Fe (II), Fe (III), In (III), La (III), Mg (II), Mn (III), Mn (IV), Mo (IV), Mo (VI), Nb (II), Nb (IV), Nb (V), Ni (II), Sc (III), Si (IV), Sn (IV), Sr (II), Pd (II), Re (VI), Re (VII), Ru (IV), Ta (V), Ti (II), Ti (III), V (V), W (IV), W (VI), Zn (II), Zr (IV). As experimental procedure the Rancimat method, which is included in biodiesel standards, was used. The results confirm that Cu indeed is the metal most strongly promoting oxidation, while most other metals gave results in which the induction time in the Rancimat test did not differ widely from that of the used biodiesel. Some metals, notably Mo and Re, showed an inhibitory effect on biodiesel oxidation. The metal oxides usually show similar effects on biodiesel oxidation from promotion to inhibition with oxides of Ag, Au, Cr, Cu, Re and Ru showing the greatest promoting effect and oxides of Mo the greatest inhibiting effect.

Transition metal chelates: Synthesis, physicochemical, thermal, and biological studies

The transition metal complex of Mn(II), Co(II), Ni(II), Cu(II), Ti(III), Cr(III), Fe(III), Zr(IV), and UO2(VI) ion with a Schiff’s base ligand derived from 2-hydroxy-[2-oxo-1,2-dihydro-3H-indol-3-ylidene]-benzohydrazide have been prepared. The complexes have been characterized by elemental analysis data, IR and electronic absorption spectra, magnetic moments, and thermogravimetric analysis data. The complexes of the 1: 1 metal-to-ligand stoichiometry have been formed. The physico-chemical data have suggested the octahedral geometry for all the complexes except for Cu(II); the Cu(II) complex has been square planar. Thermal analysis data of the ligand and its complexes have been analyzed, and the kinetic parameters have been determined using the Horowitz–Metzger method. According to the solid-state electrical conductivity measurements, the ligand and its complexes are semiconducting in nature. The antimicrobial activity of the ligand and the complexes towards E. coli, S. typhi, P. aeruginosa, and S. aureus has been tested by the disc diffusion method.

Екстракційно-фотометричне визначення кадмію(ІІ) за допомогою 1-(5-бензилтіазол-2-іл)азонафтален-2-олу

For the first time, the absorption spectra of 1-(5-benzylthiazol-2-yl)azonaphthalen-2-ol were investigated in such solvents as ethanol, toluene, chloroform and carbon tetrachloride. Cadmium(II) ion interacts with 1-(5-benzylthiazol-2-yl)azonaphthalen-2-ol forming a violet chelate complex ( λ max = 595 nm) which can be extracted into toluene from the alkaline aqueous solution. The complex compound has a molar absorptivity of 1.9∙10 4 L∙mol –1 ∙cm –1 . The stoichiometric ratio of reagent to Cd(II) in complex is equal 2:1 that was established using spectrophotometric (mole-ratio method and method of continuous variations) and voltammetric methods. Optimum reaction conditions for complexation were found, an extraction-photometric method for the determination of Cd 2+ -ions has been proposed with determination limit of 0.3 μg∙ml –1 . Zn(II), Mn(II), Ti(III) and Fe(III) ions do not have an influence on the Cd(II) determination. Interference from such ions as Co(II), Cu(II), Ag(I) and Ni(II) was shown.

Bonding in Complexes of Bis(pentalene)dititanium, Ti2(C8H6)2.

Bonding in the bis(pentalene)dititanium “double-sandwich” species Ti2Pn2 (Pn = C8H6) and its interaction with other fragments have been investigated by density functional calculations and fragment analysis. Ti2Pn2 with C2v symmetry has two metal–metal bonds and a low-lying metal-based empty orbital, all three frontier orbitals having a1 symmetry. The latter may be regarded as being derived by symmetric combinations of the classic three frontier orbitals of two bent bis(cyclopentadienyl) metal fragments. Electrochemical studies on Ti2Pn†2 (Pn† = 1,4-{SiiPr3}2C8H4) revealed a one-electron oxidation, and the formally mixed-valence Ti(II)–Ti(III) cationic complex [Ti2Pn†2][B(C6F5)4] has been structurally characterized. Theory indicates an S = 1/2 ground-state electronic configuration for the latter, which was confirmed by EPR spectroscopy and SQUID magnetometry. Carbon dioxide binds symmetrically to Ti2Pn2, preserving the C2v symmetry, as does carbon disulfide. The dominant interaction in Ti2Pn2CO2 is σ donation into the LUMO of bent CO2, and donation from the O atoms to Ti2Pn2 is minimal, whereas in Ti2Pn2CS2 there is significant interaction with the S atoms. The bridging O atom in the mono(oxo) species Ti2Pn2O, however, employs all three O 2p orbitals in binding and competes strongly with Pn, leading to weaker binding of the carbocyclic ligand, and the sulfur analogue Ti2Pn2S behaves similarly. Ti2Pn2 is also capable of binding one, two, or three molecules of carbon monoxide. The bonding demands of a single CO molecule are incompatible with symmetric binding, and an asymmetric structure is found. The dicarbonyl adduct Ti2Pn2(CO)2 has Cs symmetry with the Ti2Pn2 unit acting as two MCp2 fragments. Synthetic studies showed that in the presence of excess CO the tricarbonyl complex Ti2Pn†2(CO)3 is formed, which optimizes to an asymmetric structure with one semibridging and two terminal CO ligands. Low-temperature 13C NMR spectroscopy revealed a rapid dynamic exchange between the two bound CO sites and free CO.

Synthesis , Characterization and Biological Studies of Some Transition Metal Chelates Derived from Hydrazone Schiff Base Ligand

Complexes of Mn(II), Co(II), Ni(II), Cu(II), Ti(III), Cr(III), Fe(III), Zr(IV) and UO2(VI) with a Schiff base ligand derived from 2-hydroxy-5-methyl-3-nitroacetophenone and 2-hydroxybenzohydrazide have been prepared. The complexes have been characterized on the basis of elemental analysis, IR and electronic spectra, magnetic moment and thermogravimetric analysis. From the analytical data, the stoichiometry of the complexes has been found to be 1: 1 (metal: ligand).The physicochemical data suggest octahedral geometry for all the complexes except Cu(II). The Cu(II) complex shows square planar geometry. The thermal data of prepared compounds have been analyzed and various kinetic parameters have been evaluated according to the Horowitz-Metzger method. The solid- state electrical conductivity of synthesized compounds has been measured in pellet form and the complexes are found to have a semiconducting nature. The ligand and its complexes have also been tested for their antimicrobial behavior against E. coli, S. typhi, P. aeruginosa and S. aureus by the disc diffusion method. The Scanning electron micrograph (SEM) of the ligand and its Cu(II) complex have been studied. The Mn(II) complex has been studied by means of powder XRD and was found to be crystalline.

Separation of Sc(III) from ZrO(II) by solvent extraction using oxidized Phoslex DT-8

Oxidized di(2-ethylhexyl)dithiophoshate (Phoslex DT-8) in n-hexane is shown to extract Sc(III) greater than 97% in the pH range of 1.01–4.46, while ZrO(II) is not extracted under the same conditions. Phoslex DT-8 was oxidized by blowing air in it, and the percent extraction of Sc(III) increased along with the duration of air-oxidation. The present extraction system can be used to separate Sc(III) from ZrO(II), Ti(III), Y(III) and Al(III) in a single batchwise extraction.

The presence of Ti(II) centers in doped nanoscale TiO2 and TiO2−xNx

Unusual trends are observed in the Ti (2s, 2p) XPS spectra of Fe(II) doped TiO2 and TiO2−xNx. The binding energy of Ti (2s, 2p) initially decreases with increasing Fe(II) concentration, as expected, but increases at higher Fe(II) doping levels. Density functional theory is used to analyze the results. The observed VB-XPS and core level XPS spectra are consistent with the facile charge transfer sequence Ti(IV)+Fe(II)→Ti(III)+Fe(III) followed by Ti(III)+Fe(II)→Ti(II)+Fe(III). The formed Ti(II) sites may be relevant to nanoparticle catalysis on TiO2 surfaces.

Binuclear TiOMn charge-transfer chromophore in mesoporous silica

An all-inorganic heterobinuclear chromophore consisting of Ti(IV) oxo-bridged to a Mn(II) center has been assembled on the surface of silica pores of MCM-41 material. The key step of covalent attachment on the pore surface is the reaction of a Mn(II) precursor featuring weakly held CH3CN ligands with the OH group of a previously anchored titanol site. The optical diffuse reflectance spectrum reveals a Ti(IV)OMn(II) --> Ti(III)OMn(III) metal-to-metal charge-transfer (MMCT) absorption extending from the UV throughout to visible into the red spectral region. FT-IR, FT-Raman and optical spectroscopy confirm that the material is free of Mn oxide clusters, while EPR and Mn K-edge X-ray absorption spectra indicate that the donor center is predominantly in oxidation state +2. In situ FT-IR spectroscopy allowed detection of visible light-induced redox chemistry of the MMCT unit using O2 (18O2) and methanol as acceptor and donor probe molecules, respectively. Formate and water were observed as primary products, with methyl formate emerging as a secondary condensation product. The observed photochemistry demonstrates that excitation of the Ti(IV)OMn(II) --> Ti(III)OMn(III) results in complete transfer of an electron from donor to acceptor center, with the charge separation sufficiently long lived for initiation of redox chemistry to occur. With donor and acceptor redox potentials appropriate for driving multi-electron catalysts for water oxidation, proton or CO2 reduction, the TiOMn(II) unit is an attractive candidate as a charge-transfer chromophore in a solar fuel generating system.

Titanium-magnesium catalysts for olefin polymerization - effect of titanium oxidation state on catalyst performance

In this work, we investigated the influence of oxidation state of titanium and the effect of ethoxy groups' introduction into titanium compounds on the catalytic properties of MgCl2 - supported catalysts [with triisobutylaluminum (TIBA) or triethylaluminum (TEA) as cocatalyst] in ethylene polymerization and ethylene 1-hexene copolymerization, and on the polymer characteristics. To prepare supported titanium-magnesium catalysts of various compositions, soluble compounds of titanium in different oxidation states [?6-benzene-Ti2+Al2Cl8, Ti3+Cl3źnDBE, and Ti4+(OEt)2Cl2] were synthesized, analyzed by ESR and 13C NMR methods, and immobilized on the highly dispersed magnesium chloride. The data were obtained on the effects produced by composition and oxidation state of titanium compounds (covering also commonly used TiCl4) on the activity, control of PE molecular weight by hydrogen, copolymerization ability, and molecular weight distribution (MWD) of polyethylene. The results obtained demonstrate that different titanium precursors comprising Ti(II), Ti(III) and Ti(IV) compounds supported on MgCl2 allow preparing the highly active catalysts for ethylene polymerization or ethylene/1-hexene copolymerization. It was found that titanium oxidation state in the initial titanium compounds had a weak effect on the molecular weight and MWD of PE, whereas the ligand environment of titanium affected this parameter more strongly.

Using artificial neural networks to develop molecular mechanics parameters for the modelling of metalloporphyrins. III. Five coordinate Zn(II) porphyrins and the metalloprophyrins of the early 3d metals

Artificial neural networks (ANNs) are used as an aid in developing force field parameters for modelling, using molecular mechanics methods and the MM2 force field, the porphyrins of the early transition metals, Sc(III), Ti(II), Ti(III), Ti(IV), V(II), V(III), V(IV), Cr(III), Cr(IV) and Cr(V), in which the metal is either five- or six-coordinate. The porphyrin ring itself was modelled with previously derived parameters and attention was focussed on deriving parameters to model the coordination sphere of the metal. By modelling five-coordinate Zn(II) porphyrins with an axial pyridine ligand, for which there are many structures, we demonstrate that the length of the metal–N porph bond is relatively insensitive to the length of the metal–N axial bond, and vice versa. There are relatively few crystal structures of the early 3d metalloporphyrins available and very few which contain the same axial ligand. Hence, preliminary parameters for modelling a wide variety of axial ligands are reported; these were typically derived by initially setting the strain free bond length and bond angles involving the metal and the axial donor atom to the crystallographically observed value, and varying the bond stretching and angle bending parameter, or the strain free bond length and bond angles iteratively, until the bond length and angles were reproduced to within 0.01 Å and 2.5°, respectively. Since the modelling of the [Zn(porphyrin)(pyridine)] complexes demonstrated the relative insensitivity of the equatorial metal–ligand parameters to the axial metal–ligand parameters and vice-versa, the paucity of structures and hence the necessarily preliminary values of the parameters for the modelling of the axial ligands did not preclude the development of parameters for the equatorial ligands. The strain free bond length l o, and the stretching force constant k s for the metal–N porph bond length was varied in a grid-like pattern. The mean difference between the metal–N porph bond length observed experimentally and determined by MM was defined as the error function. The minimum value of the error function was found using ANNs. Modelling the structures with the values of k s and l o that correspond to the minimum of the error function gave mean metal–N porph bonds that differed from crystallographically observed values by at most 0.008 Å, within the experimental standard deviation of this parameter. The deviations from planarity found in many of the modelled structures were usually well reproduced in the modelling. Where significant differences were noted, these could sometimes (but not always) be shown to be due to packing forces in the crystal lattice. As expected, the orientation of axial ligands and substituents on the periphery of the porphyrin ring was often significantly different in the modelled and the solid-state structure because of the conformational freedom of these groups.

Electrosynthesis of coordination compounds by the dissolution of metal anodes using ligand precursors

Electrosynthesis of complex compounds by the dissolution of metal anodes is an established method for the preparation of a wide variety of compounds in different oxidation states in a single step. The electrolyte is an aqueous, nonaqueous or mixed solvent containing the ligand. During electrolysis the anode goes into solution and forms a complex with the ligand. The latter may also be generated in the electrolytic phase by a chemical reaction or by the cathodic reduction of the ligand precursor. A variety of thiolato, xanthato, dithiocarbamato, amine and Schiff base complexes have been synthesized using appropriate ligand precursors. Compounds obtained by anodic dissolution are in normal or lower oxidation states of the metals. The method has been utilized to synthesize some compounds of In(I), Ga(II), Th(II), Mo(II), Cr(II), Ti(III) etc. in a single step. Attempts have been made to synthesize higher valent compounds by the anodic oxidation of the initial product by a second stage electrolysis using a platinum anode.

Electrochemistry of Titanium in Molten 2AlCl3 ‐ NaCl

The electrochemistry of titanium has been examined in electrolyte. Titanium may be oxidized to yield Ti(II), Ti(III), and Ti(IV) complexes. The divalent species may be used to electrodeposit Al‐Ti alloys, while the trivalent species is sparingly soluble. Cyclic voltammetry on a tungsten electrode in solutions with varying Ti(II) concentration has been used to examine the kinetics of the precipitation reaction associated with Ti(III). The induction time required for precipitation is dependent upon the bulk concentration of Ti(II), in a manner similar to that reported for homogeneous precipitation from aqueous solutions. At higher Ti(II) concentrations and slower sweep rates the electrode is passivated by the Ti(III) precipitation. Slow sweep rate voltammetry suggests that the i‐E characteristics of the passivation reaction are dominated by the resistance associated with the precipitate film. The film blocks the electrode preventing oxidation of Ti(II) to Ti(IV). A parallel study of the dissolution kinetics of titanium metal reveals similar passivation phenomena due to Ti(III) precipitation. However, the passive film on titanium is somewhat conductive unlike that associated with the precipitated film formed on a tungsten electrode. This distinction presumably results from the formation of a compact passive film at the interface between the precipitated film and the titanium substrate. At more oxidizing potentials the protective nature of the passive film breaks down with the generation of Ti(IV). A comparison between the Ti(II) concentration determined by voltammetry and that anticipated from dissolution of titanium metal reveals a deviation from Faraday's law at high Ti(II) concentrations. This discrepancy is resolved by adopting a previously postulated model involving the formation of oligomers of Ti(II).

The Electrodeposition of Al3Ti from Chloroaluminate Electrolytes

The electrochemistry of Ti(II) in and the electrodeposition of metastable aluminum‐titanium alloys containing up to 28 atom percent Ti are reported. Ti(II)/Ti(III) was studied by chronoamperometry, chronopotentiometry, cyclic voltammetry, and convolution voltammetry during the electrochemical dissolution of titanium. It was concluded that Ti(II)/Ti(III) behaves reversibly in this electrolyte and that, at low current densities, titanium dissolves to form Ti(II). The dissolution follows Faraday's law for Ti(II) concentrations approaching , though concentrations up to 325 mmol/liter can be obtained at dissolution current efficiencies less than 100%. Single‐phase with the ordered face‐centered cubic structure is deposited under conditions where the Ti partial current is not diffusion limited. Current transients and microscopic analysis of the early stages of potentiostatic deposition suggest that forms by instantaneous three‐dimensional nucleation at potentials where the growth process is under mixed kinetic and diffusion control.

Electron transfer. 119. Reductions of rhodium-bound superoxide

Treatment of (Rh II ) 2 4+ (aq) with O 2 in 3 M HClO 4 yields a violet (e 560 max =620 M -1 cm -1 ) superoxo complex, the properties of which are in accord with the assigned formula [(H 2 O) 4 (OH)Rh III (O 2 )Rh III (OH)(H 2 O) 4 ] 3+ . This cation is reduced, in 1:1 reactions with V(II), Eu(II), Ti(III), and Fe(II), or in 2:1 reactions with ascorbic acid and hydroquinone, to a le - reduction product, the corresponding peroxo complex

Photoelectron spectroscopic and surface resistance measurements of TiO2 and V2O5 after rare‐gas sputtering

AbstractInsulating to semiconducting transformation was observed for surface layers of the transition metal oxides exposed to 1.5–15 keV He+, Ar+ and Xe+ ions. The surface electrical conductivity increased with the fluence of the ion beams and reached ∼10Ω−1 cm−1 at a fluence of 1 × 1017 Ar+ cm−2. Core‐line splittings in the metal 2p region and preferential losses of the surface oxygen observed in the x‐ray photoelectron spectra give evidence of the formation of the reduced chemical species Ti(II), Ti(III) and V(III). The ion bombardment also brought about the appearance of a new peak near the Fermi level in the UV photoelectron spectra. These observations suggest that electrons in the O 2p orbital are transferred to the 3d‐derived non‐bonding level by the losses of atomic oxygen and thus behave as charge carriers, which causes an increase in electrical conductivity.

Stopped-flow kinetic spectrophotometric method for the simultaneous determination of iron, titanium and vanadium

A kinetic method for the simultaneous determination of iron, titanium and vanadium is proposed based on their inductive effects on the chromium(VI)-iodide-starch reaction in weakly acidic medium. The reaction was monitored with the stopped-flow spectrophotometric technique. The calibration graphs are linear in the ranges 0–2.2, 0–3.1 and 0–1.8 μg ml −1 for Fe(II), Ti(III) and V(IV), respectively, and the detection limits are 0.012, 0.020 and 0.018 μg ml −1, respectively. It was found that 100–1000 times higher concentrations of Co 2+, Ni 2+, Zr 4+, Mn 2+, Cd 2+, Cu 2+, Pb 2+ and tervalent rare earths ions do not interfere with the determination. The method was applied to the determination of Fe, Ti and V in an aluminium alloy and a synthetic sample.