Alfons Baiker

Bio: Alfons Baiker is an academic researcher from ETH Zurich. The author has contributed to research in topics: Catalysis & Enantioselective synthesis. The author has an hindex of 83, co-authored 978 publications receiving 42903 citations. Previous affiliations of Alfons Baiker include University of Vienna & Paul Scherrer Institute.

Fluoro-apatite and calcium phosphate nanoparticles by flame synthesis

Abstract: Calcium phosphate nanoparticles with calcium/phosphorus molar ratios ranging from 143 to 167 have been synthesized by simultaneous combustion of calcium carboxylate and tributyl-phosphate based precursors in a flame spray reactor Fluoro-apatite and zinc or magnesium doped calcium phosphates were obtained by adding trifluoroacetic acid or corresponding carboxylates into the fuel Nanoparticle morphology and the structure of sintered ceramics were studied using transmission and scanning electron microscopy Thermal evolution of calcium phosphate phases was investigated by powder X-ray diffraction, Fourier transform infrared spectroscopy, and thermal analysis A molar ratio of Ca/P < 15 in the precursor promoted the formation of dicalcium pyrophosphate (Ca2P2O7) Phase pure β-tricalcium phosphate was obtained with a precursor Ca/P ratio of 152 after subsequent calcination at 900 °C The regular, open structure with interconnecting micropores and the facile substitution of both anions and cations suggest

Porous silica gels and TiO2/SiO2 mixed oxides prepared via the sol-gel process: characterization by spectroscopic techniques

Abstract: Titania/silica mixed oxides prepared by sol-gel techniques are characterized by diffuse reflectance FTIR, Raman and 29Si solid state CP/MAS-NMR spectroscopy. The degree of cross-linking of the silica network is inferred from the frequency of the v(Si O Si) skeletal vibration. Gels prepared by complete hydrolysis of the alkoxide precursors (tetra-ethoxy-orthosilicate, TEOS, and tetra-isopropoxy-orthotitanate, TIOT, respectively) prior to mixing exhibit TiO2 crystallites embedded in an amorphous silica matrix. Raman spectroscopy is used to study the dependence of TiO2 crystallite size on hydrolysis pH. In an alternative two-stage hydrolysis procedure, 2 mol of water are first added per mole of TEOS, followed by mixing with the appropriate amount of TIOT, and completion of the hydrolysis. No crystalline domains are detected in the resulting oxides. The formation of Si O Ti bridges, as monitored by the intensity of a characteristic 945–960 cm−1 vibration, is particularly prominent if both steps of the two-stage hydrolysis procedure are performed in an acidic medium. A redispersion treatment in base, designed to induce a pore ripening process, if found to be only effective when applied to the wet gel, i.e., prior to drying. 29Si NMR experiments are used to investigate the processes occurring upon drying at 873 K. The extent of condensation reactions, by which Si O Si bridges are formed with concomitant desorption of water, is inferred from the fraction of completely cross-linked Si( O Si)4 sites. 1H-29Si cross-polarization dynamics are found to depend strongly on the degree of cross-linking, as well as on the number of available surface silanol groups.

SCR of NO by NH3 over TiO2-supported V2O5-MoO3 catalysts: reactivity and redox behavior

Abstract: The reactivity in the selective catalytic reduction (SCR) reaction and the redox behavior of V2O5–MoO3/TiO2 catalysts was investigated by means of the temperature programmed reduction (TPR)/reaction technique, and compared with that of binary V2O5/TiO2 and MoO3/TiO2 catalysts having the same metal oxide loading. It was found that the ternary catalysts are more active in the SCR reaction at low temperatures compared to the corresponding binary samples: hence the ‘temperature window’ of the reaction is widened and shifted towards lower temperatures. Transient reactivity data provide clear evidence in favor of the hypothesis of a redox mechanism for the SCR reaction and point out that the ternary catalysts are more easily reduced and reoxidized than the corresponding binary samples: this indicates that the simultaneous presence of V and Mo enhances the catalyst redox properties, and thus its reactivity. Such conclusions are also in line with the results of the characterization studies pointing out the existence of electronic interactions involving the V and Mo surface oxide species. The overall picture closely resembles the one obtained in the case of the analogous V2O5–WO3/TiO2 system and indicates that the effects of the addition of WO3 and MoO3 to V2O5/TiO2 are similar, both oxides acting as ‘chemical’ promoters besides playing a ‘structural’ function as well.

Process for the preparation of amines.

Abstract: A single-stage process is described for the preparation of primary aliphatic polyamines of the formula in which R 1 and R 2 independently of one another are hydrogen, methyl, ethyl or aminomethyl, by reaction of polyalcohols on a Co/Ni catalyst with supercritical ammonia in the presence of hydrogen.

Gold nanoparticles: assembly, supramolecular chemistry, quantum-size-related properties, and applications toward biology, catalysis, and nanotechnology.

Abstract: Although gold is the subject of one of the most ancient themes of investigation in science, its renaissance now leads to an exponentially increasing number of publications, especially in the context of emerging nanoscience and nanotechnology with nanoparticles and self-assembled monolayers (SAMs). We will limit the present review to gold nanoparticles (AuNPs), also called gold colloids. AuNPs are the most stable metal nanoparticles, and they present fascinating aspects such as their assembly of multiple types involving materials science, the behavior of the individual particles, size-related electronic, magnetic and optical properties (quantum size effect), and their applications to catalysis and biology. Their promises are in these fields as well as in the bottom-up approach of nanotechnology, and they will be key materials and building block in the 21st century. Whereas the extraction of gold started in the 5th millennium B.C. near Varna (Bulgaria) and reached 10 tons per year in Egypt around 1200-1300 B.C. when the marvelous statue of Touthankamon was constructed, it is probable that “soluble” gold appeared around the 5th or 4th century B.C. in Egypt and China. In antiquity, materials were used in an ecological sense for both aesthetic and curative purposes. Colloidal gold was used to make ruby glass 293 Chem. Rev. 2004, 104, 293−346

The Chemistry and Applications of Metal-Organic Frameworks

Abstract: Crystalline metal-organic frameworks (MOFs) are formed by reticular synthesis, which creates strong bonds between inorganic and organic units. Careful selection of MOF constituents can yield crystals of ultrahigh porosity and high thermal and chemical stability. These characteristics allow the interior of MOFs to be chemically altered for use in gas separation, gas storage, and catalysis, among other applications. The precision commonly exercised in their chemical modification and the ability to expand their metrics without changing the underlying topology have not been achieved with other solids. MOFs whose chemical composition and shape of building units can be multiply varied within a particular structure already exist and may lead to materials that offer a synergistic combination of properties.