Inna Karatchevtseva

Single and mixed phase TiO2 powders prepared by excess hydrolysis of titanium alkoxide

Abstract To investigate the excess hydrolysis of titanium alkoxides, TiO2 powders were fabricated from titanium tetraisopropoxide using 6∶1 and 100∶1 H2O/Ti (r) ratios. The powders were dried and fired at a range of temperatures (⩽800°C). Hydroxylation and organic content in powders were characterised using attenuated total reflectance Fourier transform infrared spectroscopy (FTIR), laser Raman microspectroscopy and elemental microanalysis; surface area and pore size distribution were evaluated using N2 gas adsorption; phase composition was analysed using X-ray diffraction (XRD) and laser Raman microspectroscopy; and crystallite size was evaluated by XRD, TEM and SEM. Results showed near complete hydrolysis in a predominantly aqueous medium (r = 100), resulting in precipitated crystalline powders exhibiting brookite and anatase, which begin to transform to rutile below 500°C. The powders precipitated in a predominantly organic medium (r = 6) underwent partial hydrolysis, were highly porous and exhibited an amorphous structure, with the crystallisation of anatase occurring at ∼300°C and the transformation to rutile beginning at 500–600°C.

Synthesis and characterisation of nanocomposite materials prepared by dispersion of functional TiO2 nanoparticles in PMMA matrix

Composite powders and thin films composed of poly(methyl methacrylate) (PMMA) and functionalised titania nanoparticles are successfully prepared by in situ bulk co-polymerisation using benzoyl peroxide (BPO) as the initiator. The functionalised titania nanoparticles are synthesised by an arrested hydrolysis of Ti(OiPr)4 with either undecylenic (UA) or undecenylphosphonic (UPA) acids used as the organic templates with the long hydrocarbon chains and functional (terminal double bond) groups. Surface-modified TiO2 nanoparticles could be easily dispersed in organic solvent due to the long hydrocarbon chain surrounding the titanium core, and engaged as a co-monomer in polymerisation with the MMA due to the presence of a terminal double bond. TEM and small angle X-ray scattering (SAXS) data presented support the homogeneous and consistent distribution of inorganic phase within the PMMA matrix, with the larger titania nanoparticles detected when the UPA was employed to modify a TiO2 nanoparticle. This is attributed to the UPA greater binding affinity towards the TiO2 surfaces and therefore particles aggregation to some extent.

Uranium(VI) complexes with isonicotinic acid: from monomer to 2D polymer with unique U–N bonding

Two new uranium(VI) complexes with isonicotinic acid (HINT) have been synthesized and characterized. [(UO2)(NO3)2(HINT)2] (1) has a monomeric structure constructed of a hexagonal bipyramidal uranyl centre, two nitrate anions and two monodentate HINT in trans-positions. [(UO2)(OH)(INT)] (2) has a two-dimensional (2D) polymeric structure constructed of uranyl hydroxyl 1D pillars and μ3-bridging INT anions; the first observation of INT in μ3-bridging mode for U(VI) ion via U–N bonding. Thermal analysis confirmed both complexes lost coordinated INT ligands followed by further decomposition to form U3O8. Raman spectroscopy has confirmed the presence of uranyl ion and INT ligand in both complexes as well as the existence of nitrate vibrations in 1 and hydroxyl vibrations in 2. Their photoluminescence properties have been investigated.

Novel Chemical Synthesis and Characterization of CeTi2O6 Brannerite

Cerium titanate CeTi2O6 was prepared by a new soft chemistry route in aqueous solution. A suite of characterization techniques, including X-ray diffraction, thermal analysis, vibrational spectroscopy, and scanning and transmission electron spectroscopy, were employed to investigate the brannerite structure formation and its bulk properties. The synthesized powder formed the brannerite crystal structure upon calcination at temperatures as low as 800 °C. Samples sintered at 1350 °C possess a high level of crystallinity. X-ray absorption near-edge structure results indicate the presence of six-coordinated Ce(4+) in the brannerite samples.

Peroxide defect formation in zirconate perovskites

Atomic scale modelling suggests that excess oxygen can be accommodated in the group II perovskite zirconates by the formation of peroxide ion defects. This is unprecedented given the lack of charge compensating defects required for standard excess oxygen accommodation. The solution energy of O2 was predicted to be close to zero for BaZrO3, accommodating the peroxide ion defect more easily than in SrZrO3 or CaZrO3. This was experimentally examined by exposing SrZrO3 and BaZrO3 to hydrogen peroxide solution and then carrying out Raman spectroscopy measurements to look for a peak indicative of peroxide ions. A peak was observed at ∼1000 cm−1 in both compositions, suggesting the theoretically predicted peroxide ion is present.

Kinetics vs. thermodynamics: a unique crystal transformation from a uranyl peroxo-nanocluster to a nanoclustered uranyl polyborate

A novel method to prepare a nano-clustered uranyl polyborate in aqueous solution at room temperature has been developed. The initially formed kinetically favoured sodium uranyl peroxide yellow crystals transform, in the presence of boric acid, to the thermodynamically stable sodium uranyl polyborate in light yellow-green single crystal form.

3d transition metal complexes with a julolidine–quinoline based ligand: structures, spectroscopy and optical properties

A Schiff base type ligand with the combination of the julolidine and the quinoline groups has been reported as a potential chemosensor in detecting the cobalt(II) ion among other heavy and transition metal ions in solution. However, no crystal structure of such a ligand with any metal ions has been reported. In this work, its complexation with 3d transition metal ions (Mn(II), Co(II), Ni(II), Cu(II) and Zn(II)) has been investigated with five new complexes being synthesised, and spectroscopically and structurally characterised. [Mn2L2(CH3OH)2(CH3COO)2]·CH3OH (1) {HL (C22H21N3O) = ((E)-9-((quinolin-8-ylimino)methyl)-1,2,3,5,6,7-hexahydropyrido[3,2,1-ij]quinolin-8-ol)} shows a dinuclear structure with two Mn : L : acetate (1 : 1 : 1) units bridged by two methanol molecules. [CoL2(NO3)]·CH3OH·H2O (2) and [NiL2]·H2O (3) exhibit mononuclear structures with a Co : L or Ni : L ratio of 1 : 2. [CuL(CH3COO)]·1/3CH3OH (4) demonstrates a mononuclear structure and the Cu ion has a square planar coordination polyhedron with a L ligand and a highly non-symmetrical acetate anion. [Zn2L2(CH3COO)2]·CH3OH (5) has two types of dinuclear units, both with two ZnL units bridged by two acetate anions but in three different bridging coordination modes. Their vibrational modes, absorption and photoluminescence properties have also been investigated.

Dioxo-vanadium(V), oxo-rhenium(V) and dioxo-uranium(VI) complexes with a tridentate Schiff base ligand

The complexation of a julolidine–quinoline based tridentate ligand with three oxo-metal ions, dioxo-vanadium(V), oxo-rhenium(V) and dioxo-uranium(VI), has been investigated with four new complexes being synthesised and structurally characterised. (VO2L)·2/3H2O (1) {HL (C22H21N3O) = ((E)-9-((quinolin-8-ylimino)methyl)-1,2,3,5,6,7-hexahydropyrido[3,2,1-ij]quinolin-8-ol)} has a VO2L neutral mononuclear structure with a five-fold coordinated vanadium metal centre in a distorted trigonal bipyramidal geometry. (ReOL2)2(ReCl6)·7DMF (2) [DMF = dimethylformamide] exhibits a mixed valent rhenium complex with a (ReOL2)+ cationic unit in a distorted octahedral metal coordination geometry, charge balanced with (ReCl6)2− anions. [(UO2)L(H2O)2]2·2(NO3)·HL·4H2O (3) and [(UO2)L(CH3OH)2](NO3)·CH3OH (4) both have (UO2L)+ cationic mononuclear structures with either coordinated water or methanol molecules in pentagonal bipyramidal coordination geometries for the uranium metal centres. Intra-/intermolecular interactions including hydrogen bonding and π–π interactions are common and have been discussed. In addition, optical absorption and photoluminescence properties have been investigated.

Hydrothermal synthesis, structures and properties of two uranyl oxide hydroxyl hydrate phases with Co(II) or Ni(II) ions

Two new iso-structured uranyl oxide hydroxyl hydrate (UOH) phases with the incorporation of cobalt(II) or nickel(II) ions have been synthesised under hydrothermal conditions and structurally characterised. Both K4Co(OH)3(H2O)9[(UO2)12(O)7(OH)13] (1) and K4Ni(OH)3(H2O)9[(UO2)12(O)7(OH)13] (2) have two-dimensional (2D) polymeric uranyl oxohydroxyl layers with either potassium and hydroxyl cobalt(II) (1) or potassium and hydroxyl nickel(II) (2) ions between layers via uranyl–cation interactions. This work highlights the feasibility of making new UOH phases via a hydrothermal route at relatively higher solution pHs. It also demonstrates that other transition metal ions which are readily available in the environment may also be incorporated into such UOH phases during the natural weathering of uraninite as well as during the storage and disposal of spent nuclear fuels.

Deuterium retention and near-surface modification of ion-irradiated diamond exposed to fusion-relevant plasma

Chemical vapour deposited diamond was irradiated with 5 MeV carbon ions to simulate the damage caused by collision cascades from neutron irradiation in a fusion environment. Ion-irradiated samples were then exposed to a deuterium plasma in MAGPIE with ion flux of ~1.3 × 1021 ions m−2 s−1. Raman and near edge x-ray absorption fine structure (NEXAFS) spectroscopy were used to characterize the degree of disorder and sp2-bonding induced by the ion irradiation. The signals of sp2-bonded and disordered carbon were observed to decrease after exposure to the deuterium plasma, although sharp Raman peaks indicative of vacancy and interstitial defects induced by the MeV ions were less affected. Recovery of a diamond-like surface after plasma exposure was evident in the NEXAFS spectra. Elastic recoil detection analysis showed that the ion-damaged diamond retained more deuterium than diamond exposed only to deuterium plasma. For the case of unirradiated samples, diamond retained more deuterium than graphite. However, for the case of the ion-irradiated samples, diamond exhibited less deuterium retention than graphite.