E. V. Savinkina

Synthesis, characterization, and properties of nanoscale titanium dioxide modifications with anatase and η-TiO2 structures

Nanoscale titanium dioxide modifications with anatase and η-TiO2 structures have been obtained by the sulfate method. Bands characteristic of the η-TiO2 phase are selected in the Raman and IR spectra of the samples containing this phase. A study of the properties of synthesized samples applying a complex of physicochemical methods revealed that nanocrystals in the samples containing phases of different modifications differ in size, structure, and surface composition. It is shown that the abovementioned nanoscale modifications are characterized by the efficient sorption of As (V), Bi (III), and V (V) from aqueous media; the degree of sorption depends on the size and structural form of nanocrystals.

Synthesis and morphology of anatase and η-TiO2 nanoparticles

Samples containing anatase and η-TiO2 nanoparticles have been prepared from titanyl sulfate solutions and characterized by X-ray diffraction, transmission electron microscopy, and electron diffraction. Unit-cell parameters of η-TiO2 have been proposed that do not rule out a relationship between the anatase and η-TiO2 structures. The samples containing anatase and η-TiO2 differ in crystallite size and specific surface area and consist of agglomerates of particles of various sizes covered with an amorphous layer. We have studied the effect of synthesis conditions on the ability to prepare a particular titania polymorph with various functional characteristics.

Influence of the conditions of the sulfate method on the characteristics of nanosized anatase-type samples

The nanosized anatase modification of titanium dioxide was prepared from two forms of solvated titanyl sulfate (TiOSO4·2H2O and TiOSO4·xH2SO4·yH2O) at different initial concentrations of the reagent under different conditions of the hydrolysis and coagulation. The sample characteristics (the sizes of aggregates, microparticles, nanoparticles, and coherent scattering regions, the specific surface area, the nano- and ultrananopore volumes) were deter-mined by scanning electron microscopy, small-angle and wide-angle X-ray diffraction, and physical adsorption of nitrogen at −196 °C. The relationship between these characteristics and the conditions of the sample preparation was established. The optimal processing conditions were found for the synthesis of samples with a high practical yield of the anatase-type phase.

The characteristics of the nanosized η-TiO2 polymorph

The nanosized η-TiO2 polymorph was prepared by the hydrolysis of titanyl sulfate (TiO)SO4 · xH2SO4 · yH2O. η-TiO2 was studied by X-ray diffraction, X-ray photoelectron spectroscopy, IR spectroscopy, and Raman spectroscopy. Characteristic X-ray data and distinguishing Raman spectrum features were found for η-TiO2,. The surface of η-TiO2 samples contained adsorbed OH− particles and water molecules or water molecules of crystal hydrates. The free specific surface area of samples with crystallite sizes of L = 50 (4) and 60 (5) Å was S = 10.17 (9) and 15.6 (1) m2/g. The characteristics of samples with η-TiO2 were favorable for their use as photocatalysts and adsorbents.

Composition, microstructure, and properties of anatase and η-TiO2 nanoparticles

Nanoparticulate anatase and η-TiO2 prepared via a sulfate route have been shown (using powder X-ray diffraction, scanning electron microscopy, X-ray microanalysis, and IR spectroscopy) to differ in micro- and nanoparticle size and elemental composition. The degree of As(V), V(V), and Bi(III) extraction from aqueous solutions (for the last element, a content below its maximum allowable concentration has been reached) using nanoparticulate titania adsorbents depends on their composition, crystal structure, crystallinity, and microstructure. The synthesized anatase and η-TiO2 powders are shown to be potentially attractive carriers of PdCl2-CuCl2/TiO2 catalysts for low-temperature carbon monoxide oxidation in air.

Novel crown-containing porphyrin and its complexes with transition metals

The novel crown-containing porphyrin 5-{4-[(4-hydroxybenzo-15-crown-5)-5-yldiazo]phenyl}-10,15,20-triphenylporphyrin (H3L) and its transition metal complexes MHL (M = Co(II), Ni(II), Cu(II), and Zn(II)) and AgH2L were obtained. The compositions and structures of all the compounds were studied by MALDI-TOF mass spectroscopy, electronic absorption and IR spectroscopy. The diamagnetic compounds were additionally characterized by 1H NMR spectroscopy. It was proved that Co(II), Ni(II), Cu(II), and Zn(II) are coordinated through the pyrrole N atoms, while Ag(I) is coordinated through the hydroxyl O atom and the diazo N atom of H3L.

Efficiency of sensitizing nano-titania with organic dyes and peroxo complexes

A new method of sensitizing titania by treatment of the reaction mixture with Methylene Blue, Methyl Red or hydrogen peroxide is developed; the sensitizer was introduced into the reaction mixture while synthesizing nanosize TiO2 from titanyl sulfate. The samples prepared by this method are compared to the samples prepared by cold impregnation of Methylene Blue, Methyl Red or hydrogen peroxide on titania, pre-synthesized by sulfate method, or commercial Degussa P25 and Hombikat UV100. The samples were characterized by X-ray diffraction; their photocatalytic activity was studied in the model reaction of Methyl Orange decomposition in aqueous solution under UV and visible light. The highest photocatalytic activity under visible light was found for titania, sensitized with titanium peroxo complexes by the new method. It is also active for photodegradation of salicylic acid under visible light.

Introduction of peroxo groups into titania: preparation, characterization and properties of the new peroxo-containing phase

A new phase, where peroxo groups are incorporated into titania particles, along with anatase and hydrated η-TiO2 with peroxo groups on the surface of titania nanoparticles were prepared by introduction of H2O2 into reaction mixtures while synthesizing TiO2 from TiOSO4 or by cold impregnation of pre-synthesized TiO2. The samples were studied by a range of methods (classical and synchrotron-radiation X-ray powder diffraction, small-angle X-ray scattering, high-resolution scanning electron microscopy with energy-dispersive X-ray spectroscopy, X-ray absorption spectroscopy, IR and Raman spectroscopy, X-ray photoelectron spectroscopy, UV-vis diffuse reflectance and absorption spectroscopy, DSC). The [TiOx(O2)2−x(H2O)m] phase was first structurally characterized and compared to η-TiO2. Most samples of H2O2-sensitized TiO2 discolor methyl orange under visible light irradiation faster than commercial Hombikat UV100 treated with H2O2. The activity of the samples strongly relating to their phase composition was associated with the existence of a large amount of titanium peroxo complexes along with formation of mixed-phase samples.

Effect of sulfate synthesis conditions on characteristics of samples with the nanosized η-TiO2 modification

The nanosized titania modification η-TiO2 has been obtained from titanyl sulfate with different starting precursor concentration, under different hydrolysis and coagulation conditions. Characteristics of samples (nanoparticle and crystallite size, specific surface, pore volume) have been determined by scanning electron microscopy, small-angle and wide-angle X-ray diffraction, and nitrogen physical adsorption at −196°C, and their correlation with the synthesis conditions has been established. Optimal technological regimes ensuring fabrication of samples with a high yield of η-TiO2 modification and specified functional characteristics have been found.

Crystal structure of cadmium iodide complexes with acetamide and propaneamide [Cd(CH3CONH2)6][Cd2I6] and [Cd(C2H5CONH2)6][Cd2I6]

AbstractThe complexes of CdI2 with acetamide (AA) and propaneamide (PrA) of the composition [Cd(AA)6][Cd2I6] (I) and [Cd(PrA)6][Cd2I6] (II) were synthesized and studied by X-ray diffraction. Isostructural crystals I and II are triclinic: a = 7.285(3) and 8.066(6), b = 11.266(4) and 11.649(3), c = 11.554(3) and 12.063(2) Å, α = 100.96(2)° and 102.74(2)°, β = 91.59(2)° and 91.73(4)°, γ = 100.76(3)° and 101.05(4)°, V = 912.5 and 1081.9 Å3, respectively; space group