Browsing by Author "Arrachart, G"

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    Nanostructural evolution of titania-based materials using modified titanium precursors.
    (Wiley-Blackwell, 2009-09) Arrachart, G; Cassidy, DJ; Karatchevtseva, I; Triani, G
    Titanium ethoxide [Ti(OEt)(4)] was modified with aminobenzoic acid (AB) or aminosalicylic acid (AS) in order to control the hydrolysis and condensation rates, and to allow the preparation of organic-inorganic hybrid materials. A suite of complementary techniques, including Fourier transform infrared spectroscopy, NMR, SEM, thermogravimetric analysis, and X-ray diffraction, were used to elucidate the effects of incorporating an organic functional group into the precursor chemistry and its subsequent affect on the structure and morphology of the resultant hybrid material. The annealing behavior of the resulting hybrid titanium base materials was also investigated. Our studies show that both amino acid organic ligands, AB and AS, chemically bounded to the titanium complex, effect the precursor reactivity, specifically the hydrolysis and polycondensation reactions, which control the evolution and formation of the nanohybrid-based titania material. Following sol-gel processing, the nanohybrid materials are amorphous, due to the incorporation of the organic component. The phase transition (amorphous-anatase-rutile) observed during annealing from 25 degrees to 800 degrees C show subtle differences in the crystallization behavior, which are associated with the nature of the organic ligand. © 2009, Wiley-Blackwell.
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    Nanostructuring of hybrid silicas through a self-recognition process
    (Wiley-VCH Verlag Berlin, 2009-05-11) Arrachart, G; Creff, G; Wadepohl, H; Blanc, C; Bonhomme, C; Babonneau, F; Alonso, B; Bantignies, JL; Carcel, C; Moreau, JJE; Dieudonné, P; Sauvajol, JL; Massiot, D; Man, MWC
    The hydrolysis and condensation of a silylated derivative of ureidopyrimidinone led to nanostructured hybrid silica, such as that depicted, as clearly shown by powder XRD studies. The nanostructuring was directly related to molecular recognition through hydrogen bonding. By combining FTIR, solution and solid-state NMR spectroscopic data, the transcription of the hydrogen-bonding networks from the precursor to the final product was clearly evidenced. © 2009, Wiley-VCH Verlag Berlin
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    Silylated melamine and cyanuric acid as precursors for imprinted and hybrid silica materials with molecular recognition properties
    (Wiley-VCH Verlag Berlin, 2009-06-15) Arrachart, G; Carcel, C; Trens, P; Moreau, JJE; Man, MWC
    Two monotrialkoxysilylated compounds that consist of complementary fragments of melamine (M) and cyanuric acid (CA) have been synthesised. The molecular recognition properties of the M and CA fragments through complementary hydrogen bonds (DAD and ADA D = donor, A = acceptor) are the key factor used to direct the formation of hybrid silica materials by using a sol-gel process. These materials were synthesised following two methods: First, an organo-bridged silsesquioxane was obtained by the hydrolysis of the two complementary monotrialkoxysilylated melamine and cyanuric acid derivatives, with fluoride ions as a catalyst. The hydrogen-bonding interactions between the two organic fragments are responsible for the formation of the bridging unit. The transcription of the assembly into the hybrid material was characterised and evidenced by solid-state NMR (Si-29, C-13) and FTIR spectroscopic experiments. Second, the molecular recognition was exploited to synthesise all imprinted hybrid silica. This material was prepared by co-condensation of tetraethyl orthosilicate (TEOS) with the monosilylated cyanuric acid derivative (CA) templated by nonsilylated melamine. The melamine, template was completely removed by treating the solid material with hydrochloric acid. The reintroduction of the template was performed by treating the resulting material with all aqueous suspension Of melamine. These steps were monitored and analysed by several techniques, such as solid-state NMR (Si-29, C-13) and FTIR spectroscopic analysis and nitrogen adsorption-desorption isotherms. © 2009, Wiley-VCH Verlag Berlin
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    Synthesis and characterisation of nanocomposite materials prepared by dispersion of functional TiO2 nanoparticles in PMMA matrix
    (Royal Society of Chemistry, 2011-07-29) Arrachart, G; Karatchevtseva, I; Heinemann, A; Cassidy, DJ; Triani, G
    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. © 2011 Royal Society of Chemistry