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Instruments / Technical Area	Publication Details	Published	Actions
I11-High Resolution Powder Diffraction I12-JEEP: Joint Engineering, Environmental and Processing	Structural variety in ytterbium dicarboxylate frameworks and in situ study diffraction of their solvothermal crystallisation Matthew I. Breeze , Thomas W. Chamberlain , Guy J. Clarkson , Raíssa Pires De Camargo , Yue Wu , Juliana Fonseca De Lima , Franck Millange , Osvaldo A. Serra , Dermot O'hare , Richard I. Walton Crystengcomm vol. 1 DOI: 10.1039/C7CE00481H Diamond Proposal Number(s): [7303, 7645] Show Abstract ▼ Abstract: The ytterbium 1,4-benzenedicarboxylate (BDC) framework [Yb2(BDC)3(DMF)2]·H2O (1) crystallises from a N,N-dimethylformamide (DMF)-rich solution at 80–120 °C. (1) is constructed from infinite chains of dicarboxylate-bridged seven-coordinate Yb atoms, cross-linked in two directions by BDC to yield diamond-shaped channels (sra topology) lined by coordinated DMF molecules and occluded water. Increasing the water content in the synthesis solution yields a material with more crystal water Yb2(BDC)3(DMF)2(H2O)2 (2), in which the Yb centres are eight-coordinate and form dimers bridged by BDC to give two interpenetrating networks of pcu (α-Po) topology. Upon extended reaction in this water-rich solvent mixture, an alternative phase is formed: an anhydrous mixed BDC-formate, Yb(BDC)(HCO2), (3), which has a pillared, layered structure, with formate produced by hydrolysis of the DMF. An isoreticular version of (2) can also be formed under similar conditions using 2,6-naphthalene-dicarboxylate (NDC) as linker: [Yb2(NDC)3(H2O)4]·2DMF (4). Despite their different structures, (1) and (2) are calcined to a common porous, desolvated phase Yb2(BDC)3 at 300 °C. Using high energy X-rays at Diamond Light Source we are able to penetrate the solvothermal reaction vessels and to follow the formation of (1) and (2) in real time. This allows accurate crystallisation curves to be obtained from which qualitative kinetic information is extracted. Importantly, the high angular resolution of the in situ powder XRD patterns allows refinement of crystal structure: this permits the temporal evolution of unit cell parameters to be followed, which are ascribed to changes in coordinated solvent composition within the materials during their formation, while analysis of phase fraction allows kinetic parameters to be quantified using the nucleation-growth model of Gualtieri.	Apr 2017
B18-Core EXAFS	Control of chemical state of cerium in doped anatase TiO Juliana Fonseca De Lima , Hilni Harunsani , David Martin , Dan Kong , Peter Dunne , Diego Gianolio , Reza J. Kashtiban , Jeremy Sloan , Osvaldo Serra , Junwang Tang , Richard Walton Journal Of Materials Chemistry A 3 (18), 9890 - 9898 DOI: 10.1039/C5TA01474C Diamond Proposal Number(s): [9741] Show Abstract ▼ Abstract: Solvothermal synthesis at 240 °C in ethanol from titanium(IV) isopropoxide and cerium(III) nitrate hexahydrate produces nanocrystalline powders of anatase-structured TiO2. At low Ce content (0.5 mol% Ti replaced by Ce) the materials contain mixtures of Ce3+ and Ce4+, seen from Ce LIII-edge X-ray absorption near-edge structure (XANES) spectroscopy, which are well dispersed in the anatase structure as evidenced from nanometre-scale electron energy loss spectroscopy maps and powder X-ray diffraction (XRD). The addition of lactic acid to the solvothermal reaction produces less crystalline samples, proved by powder XRD and Raman spectroscopy, with higher surface areas from nitrogen adsorption, and that contain a higher proportion of Ce3+. This leads to material with high activity for photocatalytic hydrogen production from water under UV irradiation in the presence of sacrificial methanol and Pt catalyst. Further in situ XANES experiments at the Ce LIII-edge recorded on heating the materials in air above 300 °C shows that oxidation to Ce4+ occurs. This process, typical of the conditions usually used in the synthesis of Ce-doped titania materials, yields materials with lower photocatalytic activity.	Mar 2015

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