@article{25982, abstract = {{Iron (III) containing nanoparticles with superparamagnetic behaviour are prepared via deposition on various mesoporous supports (MgO, CeO2 and SBA-15). XRD, TEM-EDX, N2 physisorption, FTIR, and Moessbauer spectroscopy are used for their characterization. The reductive properties and catalytic behaviour in methanol decomposition of the materials are also studied. Depending on the chemical nature of the support, the predominant formation of: isolated iron species, strongly interacting with the support (for SBA-15), mixture of hematite and binary MgFe2O4 nanoparticles (for MgO) or almost homogeneously dispersed hematite particles (for CeO2) are observed. The state of iron species strongly affects their catalytic properties. The favorable effect of the support mesoporosity on the catalytic activity is most pronounced for the iron modified CeO2.}}, author = {{Tsoncheva, Tanya and Roggenbuck, Jan and Tiemann, Michael and Ivanova, Lyubomira and Paneva, Daniela and Mitov, Ivan and Minchev, Christo}}, issn = {{1387-1811}}, journal = {{Microporous and Mesoporous Materials}}, pages = {{339--346}}, title = {{{Iron oxide nanoparticles supported on mesoporous MgO and CeO2: A comparative physicochemical and catalytic study}}}, doi = {{10.1016/j.micromeso.2007.06.021}}, year = {{2008}}, } @inbook{25983, abstract = {{Nanoporous semiconducting metal oxide materials (In2O3, WO3) with uniform pore systems, large specific surface areas (80 m2 g−1), and pore-wall crystallinity were prepared by structure replication, using KIT-6 silica as a template. The products show improved properties as gas sensors (for methane or butanone) as compared to non-porous samples. In addition, porous WO3 samples with comparable porosity (prepared by conventional ‘soft templating’, using pluronic P123), which are amorphous on the atomic length scale show poorer gas sensitivity, indicating that crystallinity is a crucial factor in the sensing process.}}, author = {{Waitz, Thomas and Wagner, Thorsten and Kohl, Claus-Dieter and Tiemann, Michael}}, booktitle = {{Zeolites and related materials: Trends, targets and challenges, Proceedings of the 4th International FEZA Conference}}, issn = {{0167-2991}}, title = {{{New mesoporous metal oxides as gas sensors}}}, doi = {{10.1016/s0167-2991(08)80227-3}}, year = {{2008}}, } @article{25981, abstract = {{The growth of ZnS nanoparticles during precipitation from aqueous solution is studied by in situ stopped-flow UV absorption spectroscopy at temperatures between 283 and 323 K. Particle growth is marked by substantial ripening during the first 60 ms. Kinetic data suggest that a ripening mechanism by coalescence (oriented attachment) is predominant over Ostwald ripening, although the latter seems to coexist to a significant degree at early temporal stages, predominantly at low temperatures.}}, author = {{Tiemann, Michael and Marlow, Frank and Hartikainen, Juha and Weiss, Özlem and Lindén, Mika}}, issn = {{1932-7447}}, journal = {{The Journal of Physical Chemistry C}}, pages = {{1463--1467}}, title = {{{Ripening Effects in ZnS Nanoparticle Growth}}}, doi = {{10.1021/jp077729f}}, year = {{2008}}, } @article{25978, abstract = {{In recent years, a lot of research activity has focused on the synthesis of new ordered porous materials by utilization of porous matrices as templates. Since the matrices are themselves created by templating procedures, the entire process can be envisaged as “repeated templating”. This review describes recent conceptual developments in the field of structure replication and summarizes the large number of publications on new functional materials prepared by this method.}}, author = {{Tiemann, Michael}}, issn = {{0897-4756}}, journal = {{Chemistry of Materials}}, pages = {{961--971}}, title = {{{Repeated Templating}}}, doi = {{10.1021/cm702050s}}, year = {{2008}}, } @inbook{25984, abstract = {{Mesoporous ceria was synthesized by using both CMK-3 carbon and SBA-15 silica as structure matrices. All products exhibit uniform mesopores with diameters of 5-6 nm in a two-dimensional periodic arrangement in addition to varying amounts of interparticle porosity. The gas sensing properties (methane detection) of ordered mesoporous ceria was compared to a non-porous sample.}}, author = {{ROGGENBUCK, JAN and Tiemann, Michael}}, booktitle = {{Nanoporous Materials}}, title = {{{Mesoporous Ceria by Structure Replication from Various Porous Matrices}}}, doi = {{10.1142/9789812779168_0019}}, year = {{2008}}, } @article{25987, abstract = {{Mesoporous CeO2 was synthesised by using CMK-3 carbon as a structure matrix. Nitrogen physisorption, powder X-ray diffraction, transmission electron microscopy (TEM), selected-area electron diffraction (SAED), energy-dispersive X-ray (EDX), X-ray absorption near-edge structure (XANES), and thermal (TG/MS) analysis were used for their characterisation. Methanol decomposition to hydrogen, CO, and methane was used as a catalytic test reaction. The obtained products exhibit uniform pores with a diameter of ca. 5 nm in a two-dimensional hexagonal periodic arrangement, as well as interparticle porosity, broadly distributed around ca. 35 nm; the specific surface area is 148 m2 g−1. The pore walls are polycrystalline. The polycrystalline nature and high surface-to-volume ratio of the products is reflected in an increased signal intensity in X-ray absorption spectroscopy. The synthesis of CeO2 from Ce(NO3)3 within the pores of the carbon matrix and the subsequent thermal combustion of the carbon is monitored by thermal analysis. Catalytic tests reveal that the activity of the mesoporous products in methanol decomposition are substantially higher than for a non-porous sample.}}, author = {{Roggenbuck, Jan and Schäfer, Hanno and Tsoncheva, Tanya and Minchev, Christo and Hanss, Jan and Tiemann, Michael}}, issn = {{1387-1811}}, journal = {{Microporous and Mesoporous Materials}}, pages = {{335--341}}, title = {{{Mesoporous CeO2: Synthesis by nanocasting, characterisation and catalytic properties}}}, doi = {{10.1016/j.micromeso.2006.11.029}}, year = {{2007}}, } @article{25986, abstract = {{The authors report the synthesis of nanoporous ZnO, which exhibits a periodically ordered, uniform pore system with crystalline pore walls. The crystalline structure is investigated by x-ray diffraction, transmission electron microscopy, and selected area electron diffraction. The large specific surface area and the uniformity of the pore system are confirmed by nitrogen physisorption. Raman spectroscopy along with low-temperature photoluminescence measurements confirms the high degree of crystallinity and gives insight into defects participating in the radiative recombination processes. The authors thank Günter Koch for recording the TEM images and Marie-Luise Wolff for valuable help in the laboratory one of the authors (M.T.) thanks Michael Fröba for the continuous support.}}, author = {{Waitz, T. and Tiemann, Michael and Klar, P. J. and Sann, J. and Stehr, J. and Meyer, B. K.}}, issn = {{0003-6951}}, journal = {{Applied Physics Letters}}, title = {{{Crystalline ZnO with an enhanced surface area obtained by nanocasting}}}, doi = {{10.1063/1.2713872}}, year = {{2007}}, } @inbook{25990, abstract = {{In-situ X-ray diffraction study on the formation of a periodic mesoporous organosilica material...}}, author = {{Tiemann, Michael and Teixeira, Cilâine V. and Cornelius, Maximilian and Morell, Jürgen and Amenitsch, Heinz and Lindén, Mika and Fröba, Michael}}, booktitle = {{Recent Progress in Mesostructured Materials - Proceedings of the 5th International Mesostructured Materials Symposium (IMMS2006), Shanghai, P.R. China, August 5-7, 2006}}, issn = {{0167-2991}}, title = {{{In-situ X-ray diffraction study on the formation of a periodic mesoporous organosilica material}}}, doi = {{10.1016/s0167-2991(07)80253-9}}, year = {{2007}}, } @article{25988, abstract = {{We report on the synthesis and the gas-sensing properties (CO and NO2 detection) of mesoporous zinc oxide. A two-step structure replication method for the synthesis is employed. In the first step mesoporous SBA-15 silica is prepared by the utilization of self-organization of amphiphilic organic agents. This mesoporous silica is used as the structure matrix for synthesizing mesoporous carbon CMK-3, which, in turn, is employed for yet another replication step, using zinc nitrate as the precursor. The resulting material is characterized by X-ray diffraction and nitrogen physisorption and its gas-sensing properties are compared with a non-porous ZnO sample.}}, author = {{Wagner, T. and Waitz, T. and Roggenbuck, J. and Fröba, M. and Kohl, C.-D. and Tiemann, Michael}}, issn = {{0040-6090}}, journal = {{Thin Solid Films}}, pages = {{8360--8363}}, title = {{{Ordered mesoporous ZnO for gas sensing}}}, doi = {{10.1016/j.tsf.2007.03.021}}, year = {{2007}}, } @article{25985, abstract = {{Semiconducting metal oxides are frequently used as gas-sensing materials. Apart from large surface-to-volume ratios, well-defined and uniform pore structures are particularly desired for improved sensing performance. This article addresses the role of some key structural aspects in porous gas sensors, such as grain size and agglomeration, pore size or crack-free film morphology. New synthesis concepts, for example, the utilisation of rigid matrices for structure replication, allow to control these parameters independently, providing the opportunity to create self-diagnostic sensors with enhanced sensitivity and reproducible selectivity.}}, author = {{Tiemann, Michael}}, issn = {{0947-6539}}, journal = {{Chemistry - A European Journal}}, pages = {{8376--8388}}, title = {{{Porous Metal Oxides as Gas Sensors}}}, doi = {{10.1002/chem.200700927}}, year = {{2007}}, } @inbook{25989, abstract = {{Gas-sensing properties of ordered mesoporous Co3O4 synthesized by replication of SBA-15 silica...}}, author = {{Wagner, Thorsten and Roggenbuck, Jan and Kohl, Claus-Dieter and Fröba, Michael and Tiemann, Michael}}, booktitle = {{Recent Progress in Mesostructured Materials - Proceedings of the 5th International Mesostructured Materials Symposium (IMMS2006), Shanghai, P.R. China, August 5-7, 2006}}, issn = {{0167-2991}}, title = {{{Gas-sensing properties of ordered mesoporous Co3O4 synthesized by replication of SBA-15 silica}}}, doi = {{10.1016/s0167-2991(07)80332-6}}, year = {{2007}}, } @article{25993, abstract = {{The growth of ZnS nanoparticles by precipitation from supersaturated aqueous solution is studied by stopped-flow UV absorption spectroscopy. The average size, size distribution, and concentration of the particles are monitored within the sub-second time regime with a resolution of 1.28 ms. Particle growth at these early stages is governed by pronounced ripening. The UV absorption data strongly suggest that growth occurs by preferential adsorption of HS- anions relative to Zn2+ or ZnOH+ cations. Correspondingly, the initial sulfide concentration has a much more pronounced influence on the growth kinetics than the initial zinc concentration. These findings are verified by ζ-potential measurements which confirm that the particle surfaces are negatively charged under near-neutral pH conditions.}}, author = {{Tiemann, Michael and Marlow, Frank and Brieler, Felix and Lindén, Mika}}, issn = {{1520-6106}}, journal = {{The Journal of Physical Chemistry B}}, pages = {{23142--23147}}, title = {{{Early Stages of ZnS Growth Studied by Stopped-Flow UV Absorption Spectroscopy:  Effects of Educt Concentrations on the Nanoparticle Formation}}}, doi = {{10.1021/jp0638383}}, year = {{2006}}, } @article{25992, abstract = {{We report on the synthesis and CO gas-sensing properties of mesoporous tin(IV) oxides (SnO2). For the synthesis cetyltrimethylammonium bromide (CTABr) was used as a structure-directing agent; the resulting SnO2 powders were applied as films to commercially available sensor substrates by drop coating. Nitrogen physisorption shows specific surface areas up to 160 m2·g-1 and mean pore diameters of about 4 nm, as verified by TEM. The film conductance was measured in dependence on the CO concentration in humid synthetic air at a constant temperature of 300 °C. The sensors show a high sensitivity at low CO concentrations and turn out to be largely insensitive towards changes in the relative humidity. We compare the materials with commercially available SnO2-based sensors.}}, author = {{Wagner, Thorsten and Kohl, Claus-Dieter and Fröba, Michael and Tiemann, Michael}}, issn = {{1424-8220}}, journal = {{Sensors}}, pages = {{318--323}}, title = {{{Gas Sensing Properties of Ordered Mesoporous SnO2}}}, doi = {{10.3390/s6040318}}, year = {{2006}}, } @article{25991, abstract = {{Periodically ordered mesoporous magnesium oxide was synthesized in a double replication procedure. Mesoporous SBA-15 silica and CMK-3 carbon were successively used as hard structure matrixes. The carbon pore system was infiltrated with Mg(NO3)2, which was then converted to MgO at 573 K; the carbon matrix was finally removed by thermal combustion. The structure of the mesoporous MgO corresponds to that of the original SBA-15 silica. The products consist of hexagonally arranged cylindrical mesopores and crystalline pore walls. The efficiency of the replication series was studied by variation of the infiltration method and comprehensive pore size analysis of all involved mesoporous materials. The in situ formation of MgO inside the CMK-3 carbon pore system was monitored by thermal analysis. Postsynthetic treatment of the products at 823 K in a vacuum prior to removal of the carbon matrix was found to improve the crystallinity but to diminish the periodic order of the pore system.}}, author = {{Roggenbuck, Jan and Koch, Günter and Tiemann, Michael}}, issn = {{0897-4756}}, journal = {{Chemistry of Materials}}, pages = {{4151--4156}}, title = {{{Synthesis of Mesoporous Magnesium Oxide by CMK-3 Carbon Structure Replication}}}, doi = {{10.1021/cm060740s}}, year = {{2006}}, } @article{25995, abstract = {{The early stages of ZnS nanoparticle growth from supersaturated solution are investigated in situ by stopped-flow UV absorption spectroscopy with a time resolution of 1.28 ms. A model for data analysis is suggested which makes it possible to study both the average particle radius and the concentration. The average radii lie in the sub-nanometer range. During the first 40 ms, growth is predominantly governed by ripening.}}, author = {{Tiemann, Michael and Weiß, Özlem and Hartikainen, Juha and Marlow, Frank and Lindén, Mika}}, issn = {{1439-4235}}, journal = {{ChemPhysChem}}, pages = {{2113--2119}}, title = {{{Early Stages of ZnS Nanoparticle Growth Studied by In-Situ Stopped-Flow UV Absorption Spectroscopy}}}, doi = {{10.1002/cphc.200500163}}, year = {{2005}}, } @article{25994, abstract = {{Periodically ordered mesoporous magnesium oxides were synthesized by utilization of mesoporous CMK-3 carbon as exotemplate. The products exhibit high thermal stability and basic properties, which makes them promising for application in heterogeneous basic catalysis.}}, author = {{Roggenbuck, Jan and Tiemann, Michael}}, issn = {{0002-7863}}, journal = {{Journal of the American Chemical Society}}, pages = {{1096--1097}}, title = {{{Ordered Mesoporous Magnesium Oxide with High Thermal Stability Synthesized by Exotemplating Using CMK-3 Carbon}}}, doi = {{10.1021/ja043605u}}, year = {{2005}}, } @article{25996, abstract = {{In situ Synchrotron SAXS/XRD Study on the Formation of Ordered Mesoscopic Hybrid Materials with Crystal-Like Walls...}}, author = {{Morell, Jürgen and Teixeira, Cilaine V. and Cornelius, Maximilian and Rebbin, Vivian and Tiemann, Michael and Amenitsch, Heinz and Fröba, Michael and Lindén, Mika}}, issn = {{0897-4756}}, journal = {{Chemistry of Materials}}, pages = {{5564--5566}}, title = {{{In situ Synchrotron SAXS/XRD Study on the Formation of Ordered Mesoscopic Hybrid Materials with Crystal-Like Walls}}}, doi = {{10.1021/cm048453g}}, year = {{2004}}, } @inbook{25997, abstract = {{Recent Advances in the Synthesis of Mesostructured Aluminium Phosphates...}}, author = {{Tiemann, Michael and Fröba, Michael}}, booktitle = {{Host‐Guest‐Systems Based on Nanoporous Crystals}}, title = {{{Recent Advances in the Synthesis of Mesostructured Aluminum Phosphates}}}, doi = {{10.1002/3527602674.ch10}}, year = {{2003}}, } @article{25998, abstract = {{The formation of mesoscopically ordered silica/surfactant composites under acidic synthesis conditions is studied by time-resolved in-situ small-angle X-ray scattering (SAXS) using synchrotron radiation. Benzene is used a an additive which acts as a weak swelling agent although most of the benzene molecules are found to reside near the surfactant/silicate interface region rather than in the micelle cores. With increasing relative amounts of benzene, the curvature of the micellar aggregates decreases, which finally leads to a transition from (hexagonally) rodlike to lamellar; a mechanism for this change in curvature is suggested.}}, author = {{Tiemann, Michael and Goletto, Valérie and Blum, Raphaël and Babonneau, Florence and Amenitsch, Heinz and Lindén, Mika}}, issn = {{0743-7463}}, journal = {{Langmuir}}, pages = {{10053--10057}}, title = {{{In-Situ SAXS Studies on the Formation of Silicate/Surfactant Mesophases with Solubilized Benzene under Acidic Conditions}}}, doi = {{10.1021/la026473w}}, year = {{2002}}, } @article{26001, abstract = {{Mesoporous aluminophosphates with a strict ratio of Al∶P = 1∶1 have been synthesised from a single-source molecular precursor.}}, author = {{Tiemann, Michael and Fröba, Michael}}, issn = {{1359-7345}}, journal = {{Chemical Communications}}, pages = {{406--407}}, title = {{{Mesoporous aluminophosphates from a single-source precursor}}}, doi = {{10.1039/b110662g}}, year = {{2002}}, }