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.
In this work, fully a-axis oriented SrTiO 3 thin films were synthesized by ink-jet printing of water-based precursor inks. The developed precursor solution or 'ink' was optimized in terms of rheology, leading to the ejection of single droplets showing a maximum contact angle of 12°on (100) oriented single crystal LaAlO 3 substrates. By using the appropriate ink-jet deposition parameters and thermal treatment, well-textured and dense SrTiO 3 films of 130 nm thickness were obtained. The biaxial texture is maintained up to the surface of the films, leading to the formation of (h00)-oriented terraces. As shown by transmission electron microscopy, excellent texture transfer was achieved from the SrTiO 3 film to the YBa 2 Cu 3 O 7 − δ layer deposited by pulsed laser deposition. Outstanding superconducting properties were obtained with critical current densities up to 3.6 MA cm −2 in self-field at 77 K, demonstrating that these sustainable SrTiO 3 films meet the requirements to be used as growing template for high quality superconducting coatings.
The use of selective catalysts and easy recycling thereof, preferably with full recovery, is a major trend in green chemistry. Heterogenization of the active site on a porous solid support is an elegant method, often explored nowadays, to obtain a catalyst that can be easily separated from the medium by filtration. Another important trend is the use of water as a solvent which, restricts the use of nonhydrolytically stable supports.In 2015, we developed an allyl-functionalized interconnected [CH2Si]3 ring-type Periodic Mesoporous Organosilica (PMO) and applied it as a HPLC packing. 1 We also showed its exceptional hydrolytic stability (>pH 12 and >150°C). In order to develop this ultra-stable material into a catalytic support a different synthesis approach is required, e.g. to improve the pore morphology. Now, we developed a 100% monoallyl ring-type (mAR) PMO as a novel, versatile and exceptionally stable catalytic support with a high internal surface area and 5.0 nm pores. 2 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 reused for several runs. Moreover, the hydrophobic/hydrophilic reaction environment and ordered pores of the mAR-support enable high catalytic activity for a poorly water-soluble substrates.
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