Sander Clerick

Influence of aqueous precursor chemistry on the growth process of epitaxial SrTiO3 buffer layers

In this Article, epitaxial thin films of SrTiO3 were prepared on single crystalline (100) LaAlO3 by an aqueous chemical solution deposition method. By using different chelating agents to stabilize the metal ions in water, the impact of the precursor chemistry on the microstructural and crystalline properties of the films was studied. Thorough investigation of the precursor by means of infrared and Raman spectroscopy as well as thermogravimetric analysis revealed that stable precursors can be obtained in which strontium ions can be either free in the solution or stabilized by one of the chelating agents. This stabilization of strontium ions appeared to be essential in order to obtain single phase SrTiO3 films. Precursors in which Sr(2+) remained as free ions showed SrO microcrystal segregation. Precursors in which both metal ions were stabilized gave rise to strongly textured, dense, and terraced SrTiO3 films, allowing subsequent deposition of YBa2Cu3O7-δ with superior superconducting performances.

Heterogeneous Ru(III) oxidation catalysts via ‘click’ bidentate ligands on a periodic mesoporous organosilica support

A 100% monoallyl ring-type Periodic Mesoporous Organosilica (PMO) is prepared as a novel, versatile and exceptionally stable catalytic support with a high internal surface area and 5.0 nm pores. Thiol–ene ‘click’ chemistry allows straightforward attachment of bifunctional thiols (–NH2, –OH, –SH) which, exploiting the thioether functionality formed, give rise to ‘solid’ bidentate ligands. [Ru(acac)2(CH3CN)2]PF6 is attached and complex formation on the solid is studied via density functional theory. All resulting solid catalysts show high activity and selectivity in alcohol oxidation reactions performed in green conditions (25 °C/water). The PMO catalysts do not leach Ru during reaction and are thus easily recuperated and re-used for several runs. Furthermore, oxidation of poorly water-soluble (±)-menthol illustrates the benefits of using hydrophobic PMOs as catalytic supports.