Mathias Laurin

Friedrich-Alexander Universität Erlangen-Nürnberg, Erlangen, Bavaria, Germany

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Publications (61)325.49 Total impact

  • The Journal of Physical Chemistry C 10/2015; DOI:10.1021/acs.jpcc.5b07591 · 4.77 Impact Factor
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    ABSTRACT: Molecular insights into porphyrin adsorption on nanostructured metal oxide surfaces and associated ion exchange reactions are key to the development of functional hybrids for energy conversion, sensing and light emission devices. Here we investigated the adsorption of tetraphenyl-porphyrin (2HTPP) from toluene solution on two types of MgO powder. We compare MgO nanocubes with an average size d < 10 nm and MgO cubes with 10 nm ≤ d ≤ 1000 nm. Using molecular spectroscopy techniques such as UV/Vis transmission and diffuse reflectance (DR), photoluminescence (PL) and diffuse reflectance infrared Fourier-transform (DRIFT) spectroscopy in combination with structural characterization techniques (powder X-ray diffraction and transmission electron microscopy, TEM) we identified a new room temperature metalation reaction which converts 2HTPP into magnesium tetraphenyl-porphyrin (MgTPP). Mg2+ uptake from the MgO nanocube surfaces and the concomitant protonation of the oxide surface levels off at a concentration that corresponds to roughly one monolayer equivalent adsorbed on the MgO nanocubes. Larger MgO cubes, in contrast, show suppressed exchange, and only traces of MgTPP can be detected by photoluminescence.
    ACS Applied Materials & Interfaces 10/2015; 7(41). DOI:10.1021/acsami.5b08123 · 6.72 Impact Factor
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    ABSTRACT: The oxidation of carbon monoxide has been studied on pristine CeO2, Rh–CeO2, and Pt–CeO2 powders prepared in one step by solution combustion synthesis (SCS). The reaction was cycled between an oxygen-rich and a CO-rich feed with regard to the stoichiometric conditions. CO2 production was monitored by mass spectrometry, while the surface species were probed by operando DRIFTS (Diffuse Reflectance Infrared Fourier Transform Spectroscopy). Whereas the reaction starts above 150 °C on CeO2 and Rh–CeO2 and does not depend on the state of the surface (oxidized or reduced), the reaction on Pt–CeO2 shows strong dependency on the initial state and substantial activity is achieved at much lower temperatures with the CO-rich feed. We relate this result to the change in the oxidation state of Pt via strong interaction with ceria.
    Catalysis Science & Technology 09/2015; DOI:10.1039/C5CY00827A · 5.43 Impact Factor
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    ABSTRACT: To elucidate the adsorption behavior and interaction mechanisms of organic linker units on oxide surfaces, we have performed a model study under ultrahigh vacuum (UHV) conditions. We apply infrared reflection absorption spectroscopy (IRAS) in combination with density-functional theory (DFT), temperature programmed desorption (TPD), and X-ray photoelectron spectroscopy (XPS). Phthalic anhydride (PAA) was deposited at temperatures between 100 and 300 K by physical vapor deposition (PVD) onto an ordered MgO(100) film grown on Ag(100). At 100 K, the first monolayer adsorbs molecularly with the molecular plane aligned parallel to the surface. Subsequent growth of a multilayer film at low temperature also occurs with preferential molecular alignment parallel to the surface. At 240 K, the multilayer desorbs without decomposition. At 300 K, a mixed monolayer of chemically modified ring-opened and intact phthalic anhydride exists on the surface. The chemically modified species binds in a strongly tilted geometry via opening of the anhydride ring to form a bis-carboxylate species. This species additionally stabilizes the coadsorbed molecular PAA via intermolecular interactions. Finally, surface defects and hydroxyl groups are found to increase the amount of surface bis-carboxylate at 300 K, whereas the relative amount of coadsorbed molecular PAA decreases.
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    ABSTRACT: Structural control of organic thin films on dielectric substrates is the key to tailor the physical properties of hybrid materials, e.g. for application in solar energy conversion, molecular electronics or catalysis. In this work, we investigate the molecular orientation of phthalic anhydride (PAA) films on atomically well-defined MgO(100) on Ag(100) using temperature-programmed infrared reflection absorption spectroscopy (TP-IRAS) in combination with density-functional theory (DFT). A robust procedure is presented to determine the orientation of the PAA molecules which relies on the intensity ratios of vibrational bands only. We show that even at deposition temperatures of 110 K the PAA multilayer grows with a specific molecular orientation, i.e. the PAA molecular plane is preferentially aligned parallel with the MgO surface. No change of molecular orientation occurs up to a temperature of 145 K. Between 145 and 160 K, the films restructures adopting a nearly flat-lying molecular orientation. Between 170 and 205 K the film undergoes a second structural transition to a crystalline phase. This transition is associated with a pronounced molecular reorientation. The molecules adopt a tilted orientation and, simultaneously, rotate around their C2 axes. The reorientation behavior suggests that the molecular orientation in the crystalline phase is controlled by the interaction with the MgO(100) substrate. At higher temperature, no further restructuring is observed until the PAA multilayer desorbs at temperatures above 230 K.
    Langmuir 06/2015; 31(28). DOI:10.1021/acs.langmuir.5b01392 · 4.46 Impact Factor
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    ABSTRACT: A catalyst designed for homogeneous catalysis is shown to generate its own liquid phase if deposited onto a support. In this way, a macroscopically heterogeneous catalyst generates a microscopically homogeneous catalytic environment by self-organization. 2,2'-((3,3'-di-tert-butyl-5,5'-dimethoxy-[1,1'-biphenylj-2,2'-diyl)-bis(oxy))bis(4,4,5,5-tetraphenyl-1,3,2-dioxaphospholane) modified rhodium complexes molecularly adsorbed onto porous silica powder show surprisingly high activity and regioselectivity in the gas-phase hydroformylation of propene to but-anal, with no sign of deactivation. Operando IR investigations combined with density functional theory calculations confirm a side reaction: the aldol condensation of the butanal products. These heavier by-products accumulate inside the pores of the catalytic material. IR and gas chromatography show a direct relation between formation of enones, products of the aldol condensation, performance, and stability of the catalytic system. This demonstrates that the aldol condensation products generated in situ act as a solvent providing an ideal environment to the impregnated homogeneous catalyst. (c) 2014 Elsevier Inc. All rights reserved.
    Journal of Catalysis 01/2015; 321. DOI:10.1016/j.jcat.2014.10.019 · 6.92 Impact Factor
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    ABSTRACT: Through the use of temperature-programmed desorption (TPD), the self-metalation and dehydrogenation of deuterated 5,10,15,20-tetraphenyl-21,23D-porphyrin on Cu(111) have been studied, resulting in new insight into the metalation of porphyrins on surfaces. The metalation is found to proceed through the transfer of the central aminic hydrogen atoms to the Cu(111) surface and not, as suggested by gas phase calculations, through the combination of the hydrogen atoms to molecular hydrogen above the partially inserted metal center. This finding suggests that the metalation reaction could be significantly influenced by the stability of hydrogen on the substrate surface. The metalation reaction and the subsequent hydrogenation and dehydrogenation of the periphery of the porphyrin molecule leading to hydrogen–deuterium exchange are modeled with a simple microkinetic reaction model. The model is able to describe the main features of the TPD spectra.
    The Journal of Physical Chemistry C 10/2014; 118(46):26729–26736. DOI:10.1021/jp507303h · 4.77 Impact Factor
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    ABSTRACT: We herein describe a straight forward procedure to increase the performance of platinum-on-alumina catalysts in methanol steam reforming by applying an alkali hydroxide coating according to the "solid catalyst with ionic liquid layer" (SCILL) approach. We demonstrate by diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and temperature-programmed desorption (TPD) studies that potassium doping plays an important role in the catalyst activation. Moreover, the hygroscopic nature and the basicity of the salt modification contribute to the considerable enhancement in catalytic performance. During reaction, a partly liquid film of alkali hydroxides/carbonates forms on the catalyst/alumina surface, thus significantly enhancing the availability of water at the catalytically active sites. Too high catalyst pore fillings with salt introduce a considerable mass transfer barrier into the system as indicated by kinetic studies. Thus, the optimum interplay between beneficial catalyst modification and detrimental mass transfer effects had to be identified and was found on the applied platinum-on-alumina catalyst at KOH loadings around 7.5 mass %.
    ChemSusChem 08/2014; 7(9). DOI:10.1002/cssc.201402357 · 7.66 Impact Factor
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    ABSTRACT: Five to thirty monolayer thick films of the ionic liquid [C2C1Im][OTf] were vaporized in vacuo onto an atomically clean Pd(111) single crystal surface at 220 K. Time- and temperature-resolved infrared reflection-absorption spectroscopy reveals growth, interactions with the metallic support, and the macroscopic phase behavior of the layer. At 220 K, the IL layer first grows in form of a glassy phase. Crystallization of the IL was witnessed above a critical thickness of about ten monolayers. Based on the known bulk crystal structure of the IL, we suggest the formation of well-oriented checkerboard-like crystalline film structures on the surface. The preferential orientation manifested by the crystal phase with regard to the macroscopic metallic surface is attributed to strong interactions between anionic headgroups and the metal.
    Langmuir 05/2014; 30(23). DOI:10.1021/la500842c · 4.46 Impact Factor
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    ABSTRACT: Liquid organic hydrogen carriers (LOHC) are compounds that enable chemical energy storage through reversible hydrogenation. They are considered a promising technology to decouple energy production and consumption by combining high-energy densities with easy handling. A prominent LOHC is N-ethylcarbazole (NEC), which is reversibly hydrogenated to dodecahydro-N-ethylcarbazole (H12-NEC). We studied the reaction of H12-NEC on Pt(111) under ultrahigh vacuum (UHV) conditions by applying infrared reflection-absorption spectroscopy, synchrotron radiation-based high resolution X-ray photoelectron spectroscopy, and temperature-programmed molecular beam methods. We show that molecular adsorption of H12-NEC on Pt(111) occurs at temperatures between 173 and 223 K, followed by initial C-H bond activation in direct proximity to the N atom. As the first stable dehydrogenation product, we identify octahydro-N-ethylcarbazole (H8-NEC). Dehydrogenation to H8-NEC occurs slowly between 223 and 273 K and much faster above 273 K. Stepwise dehydrogenation to NEC proceeds while heating to 380 K. An undesired side reaction, C-N bond scission, was observed above 390 K. H8-NEC and H8-carbazole are the dominant products desorbing from the surface. Desorption occurs at higher temperatures than H8-NEC formation. We show that desorption and dehydrogenation activity are directly linked to the number of adsorption sites being blocked by reaction intermediates.
    ACS Catalysis 02/2014; 4(2):657-665. DOI:10.1021/cs400946x · 9.31 Impact Factor
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    ABSTRACT: The interactions between ionic liquids and their supports determine many of their applications. The adsorption of the ionic liquid 1-ethyl-3-methylimidazolium trifluoromethanesulfonate [C2C1Im][OTf] on Pd(111), ordered Al2O3/NiAl(110), and Pd nanoparticles supported on Al2O3/NiAl(110) was investigated under ultrahigh vacuum (UHV) conditions using time-resolved infrared reflection absorption spectroscopy (TR-IRAS). On Pd, the [OTf]− anion stands up with its CF3 group directed toward the vacuum, whereas the anion is less clearly oriented on the oxide. We also find that strong interactions of the IL with the Pd result in migration of the IL from the oxide to the metal nanoparticles.
    The Journal of Physical Chemistry C 02/2014; 118(6):3188–3193. DOI:10.1021/jp5006692 · 4.77 Impact Factor
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    ABSTRACT: From a different angle: Thin films of functionalized ionic liquids are deposited on cerium oxides following a surface science approach. The functionalization of the alkyl chain changes its orientation with respect to the surface plane from normal to parallel. This then leads to a different surface chemistry at higher temperatures.
    ChemPhysChem 11/2013; 14(16). DOI:10.1002/cphc.201300792 · 3.42 Impact Factor
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    ABSTRACT: Dodecahydro-N-ethylcarbazole (H12 -NEC) has been proposed as a potential liquid organic hydrogen carrier (LOHC) for chemical energy storage, as it combines both favourable physicochemical and thermodynamic properties. The design of optimised dehydrogenation catalysts for LOHC technology requires a detailed understanding of the reaction pathways and the microkinetics. Here, we investigate the dehydrogenation mechanism of H12 -NEC on Pd(111) by using a surface-science approach under ultrahigh vacuum conditions. By combining infrared reflection-absorption spectroscopy, density functional theory calculations and X-ray photoelectron spectroscopy, surface intermediates and their stability are identified. We show that H12 -NEC adsorbs molecularly up to 173 K. Above this temperature (223 K), activation of CH bonds is observed within the five-membered ring. Rapid dehydrogenation occurs to octahydro-N-ethylcarbazole (H8 -NEC), which is identified as a stable surface intermediate at 223 K. Above 273 K, further dehydrogenation of H8 -NEC proceeds within the six-membered rings. Starting from clean Pd(111), CN bond scission, an undesired side reaction, is observed above 350 K. By complementing surface spectroscopy, we present a temperature-programmed molecular beam experiment, which permits direct observation of dehydrogenation products in the gas phase during continuous dosing of the LOHC. We identify H8 -NEC as the main product desorbing from Pd(111). The onset temperature for H8 -NEC desorption is 330 K, the maximum reaction rate is reached around 550 K. The fact that preferential desorption of H8 -NEC is observed even above the temperature threshold for H8 -NEC dehydrogenation on the clean surface is attributed to the presence of surface dehydrogenation and decomposition products during continuous reactant exposure.
    Chemistry - A European Journal 08/2013; 19(33). DOI:10.1002/chem.201301323 · 5.73 Impact Factor
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    Mathias Laurin ·
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    ABSTRACT: QVibeplot is a software program that automatically generates two-dimensional visualizations of molecular vibrations. The representations show the changes of bond lengths, angles, and torsions occurring upon a vibration. This is consistent with the experimentalist’s understanding of molecular vibrations that makes a distinction between stretching and deformation modes. Two-dimensionality is achieved by basing the representation on a skeletal formula of the molecule. The program also displays the spectrum and the list of frequencies. The phase and amplitude are indicated as well, providing a comprehensive visualization of molecular vibrations. The software is available online as a free and open-source software.
    Journal of chemical education 07/2013; 90(7):944-946. DOI:10.1021/ed300554z · 1.11 Impact Factor
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    ABSTRACT: Tri-salts added: Pt on alumina catalysts can be used for converting methanol and water into hydrogen and carbon dioxide, for applications such as hydrogen storage. Both the activity and selectivity could be enhanced by coating these materials with a thin layer of a molten salt mixture of Li/K/Cs acetate. Potassium doping was identified by DRIFTS measurements to be an important factor for the boost in catalyst performance.
    Angewandte Chemie International Edition 05/2013; 52(19). DOI:10.1002/anie.201209758 · 11.26 Impact Factor
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    ABSTRACT: Practical applications of ionic liquids (ILs) often involve IL/oxide interfaces, but little is known regarding their interfacial chemistry. The unusual physicochemical properties of ILs, including their exceptionally low vapor pressure, provide access to such interfaces using a surface science approach in ultrahigh vacuum (UHV). We have applied synchrotron radiation photoelectron spectroscopy (SR-PES) to the study of a thin film of the ionic liquid [C6C1Im][Tf2N] prepared in situ in UHV on ordered stoichiometric CeO2(111) and partially reduced CeO2–x. On the partially reduced surface, we mostly observe decomposition of the anion. On the stoichiometric CeO2(111) surface, however, a layer of surface-anchored organic products with high thermal stability is formed upon reaction of the cation. The suggested acid–base reaction pathway may provide well-defined functionalized IL/solid interfaces on basic oxides.
    Journal of Physical Chemistry Letters 12/2012; 4(1):30–35. DOI:10.1021/jz301856a · 7.46 Impact Factor
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    ABSTRACT: Towards a better understanding of the interface chemistry of ionic liquid (IL) thin film catalytic systems we have applied a rigorous surface science model approach. For the first time, a model homogeneous catalyst has been prepared under ultrahigh vacuum conditions. The catalyst, di-μ-chlorobis(chlorotricarbonylruthenium) [Ru(CO)(3)Cl(2)](2), and the solvent, the IL 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [BMIM][Tf(2)N], have been deposited by physical vapor deposition onto an alumina model support [Al(2)O(3)/NiAl(110)]. First, the interaction between thin films of [Ru(CO)(3)Cl(2)](2) and the support is investigated. Then, the ruthenium complex is co-deposited with the IL and the influence of the solvent on the catalyst is discussed. D(2)O, which is a model reactant, is further added. Growth, surface interactions, and mutual interactions in the thin films are studied with IRAS in combination with density functional (DFT) calculations. At 105 K, molecular adsorption of [Ru(CO)(3)Cl(2)](2) is observed on Al(2)O(3)/NiAl(110). The IRAS spectra of the binary [Ru(CO)(3)Cl(2)](2) + [BMIM][Tf(2)N] and ternary [Ru(CO)(3)Cl(2)](2) + [BMIM][Tf(2)N] + D(2)O show every characteristic band of the individual components. Above 223 K, partial decomposition of the ruthenium complex leads to species of molecular nature attributed to Ru(CO) and Ru(CO)(2) surface species. Formation of metallic ruthenium clusters occurs above 300 K and the model catalyst decomposes further at higher temperatures. Neither the presence of the IL nor of D(2)O prevents this partial decomposition of [Ru(CO)(3)Cl(2)](2) on alumina.
    Physical Chemistry Chemical Physics 07/2012; 14(30):10603-12. DOI:10.1039/c2cp40697g · 4.49 Impact Factor
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    ABSTRACT: Nickel(II) complexes with double alkyl chain functionalized N-heterocyclic carbene (NHC) ligands, [NiCl2(C12MIM)2] and [NiCl2(C12C12IM)2], where C12MIM = 1-dodecyl-3-methylimidazolin-2-ylidene (1) and C12C12IM = 1,3-didodecylimidazolin-2-ylidene (2), have been prepared and fully characterized by 1H NMR, 13C NMR, and CHN elemental analyses. Furthermore, we have developed a system, in which double long alkyl chain derivatized Ni–NHC complexes are dissolved in the related ionic liquid crystalline 1,3-didodecylimidazolium tetrafluoroborate, [C12C12IM][BF4], to form pre-organized structures for enhanced reactivity. Remarkably, differential scanning calorimetry, polarized optical microscopy, and temperature-programmed IR reflection absorption spectroscopy performed on a mixture of 10 wt% Ni complexes in [C12C12IM][BF4] demonstrate that this system retains an ionic liquid crystalline phase; even after immobilization onto a silica-100 support with pore filling α = 1.
    Journal of Materials Chemistry 01/2012; 22(5):1893-1898. DOI:10.1039/C1JM13416G · 7.44 Impact Factor
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    ABSTRACT: The influence of confinement on the ionic liquid crystal (ILC) [C(18)C(1)Im][OTf] is studied using differential scanning calorimetry (DSC), polarized optical microscopy (POM), and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The ILC studied is supported on Si-based powders and glasses with pore sizes ranging from 11 to 50 nm. The temperature of the solid-to-liquid-crystalline phase transition seems mostly unaffected by the confinement, whereas the temperature of the liquid-crystalline-to-liquid phase transition is depressed for smaller pore sizes. A contact layer with a thickness in the order of 2 nm is identified. The contact layer exhibits a phase transition at a temperature 30 K lower than the solid-to-liquid-crystalline phase transition observed for the neat ILC. For applications within the "supported ionic liquid phase (SILP)" concept, the experiments show that in pores of diameter 50 nm a pore filling of α>0.4 is sufficient to reproduce the phase transitions of the neat ILC.
    ChemPhysChem 12/2011; 12(18):3539-46. DOI:10.1002/cphc.201100379 · 3.42 Impact Factor
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    ABSTRACT: The picture shows the temperature-switchable molecular structure of an ionic liquid crystal, confined as a thin film in a porous material. This work is presented on p. 3539 by P. Wasserscheid, J. Libuda, K. Meyer et al.
    ChemPhysChem 12/2011; 12(18). DOI:10.1002/cphc.201190091 · 3.42 Impact Factor

Publication Stats

1k Citations
325.49 Total Impact Points


  • 2007-2015
    • Friedrich-Alexander Universität Erlangen-Nürnberg
      • Lehrstuhl für Technische Elektronik
      Erlangen, Bavaria, Germany
  • 2008-2014
    • Universitätsklinikum Erlangen
      Erlangen, Bavaria, Germany
  • 2003-2007
    • Max Planck Society
      München, Bavaria, Germany
    • Fritz Haber Institute of the Max Planck Society
      • Department of Physical Chemistry
      Berlín, Berlin, Germany