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  • 51. Kirilin, A
    et al.
    Sahin, S
    Tokarev, A
    Mäki Arvela, P
    Kordas, K
    Leino, A R
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Kustov, L M
    Salmi, T
    Murzin, D Yu
    Mechanistic investigations of the reaction network in chemobiocatalyzed synthesis of R1Phenylethyl Acetate2010Inngår i: Kinetics and catalysis, ISSN 0023-1584, E-ISSN 1608-3210, Vol. 51, nr 6, s. 809-815Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The kinetics and reaction network of the onepot synthesis of R1phenylethyl acetate was investigated at 70°C in toluene over a combination of three different catalysts: PdZn/Al2O3 as a catalyst for acetophenone hydrogenation, lipase as an enzymatic catalyst for R1phenylethanol acylation with ethyl acetate and Ru/Al2O3 as a racemization catalyst for S1phenylethanol. In addition to the desired reactions, other reactions, namely hydrogenolysis and dehydration of (R, S)1phenylethanol and debenzylation of (R, S)1phenylethyl acetate also occurred. The kinetic results revealed that ethylbenzene formation was enhancedwith higher amounts of PdZn/Al2O3, whereas lipase did not catalyze ethylbenzene formation. Furthermore, ethylbenzene was formed in the hydrogenolysis of (R, S)phenylethanol and in the debenzylation of (R, S)1phenylethylacetate over Pd/Al2O3 catalyst. The presence of Ru/Al2O3 catalyst, in which Ru was in the oxidation state of 3+, enhanced the formation of R1phenylethyl acetate, although no clear racemization of S1phenylethanol during the onepot synthesis of  R1phenylethyl acetate was observed. Dynamic kinetic resolution of (R, S)1phenylethanol in toluene, was, however, demonstrated over Ru/Al2O3 and lipase.

  • 52.
    Kiselev, A
    et al.
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Kemi.
    Andersson, M
    Mattson, A
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Kemi.
    Sjöberg, Staffan
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Kemi.
    Palmqvist, A
    Österlund, L
    Solar light decomposition of DFP on the surface of anatase and rutile TiO2 prepared by hydrothermal treatment of microemulsions2005Inngår i: Surface Science, Vol. 584, nr 1, s. 98-105Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The photocatalytic decomposition of diisopropylfluorophosphate (DFP) over nanostructured anatase and rutile TiO2 powder was investigated by FTIR and XPS. Upon irradiation with artificial solar light DFP decomposed on both polymorphs as evidenced by FTIR. For both crystalline structures acetone and subsequently coordinated formate and carbonate were observed on the surface during the photocatalytic reaction as the isopropyl groups dissociated from DFP. XPS revealed that small amounts of phosphates and inorganic fluoride (TiF) gradually built up on both TiO2 surfaces, while organic F was present only on the rutile phase. From repeated cycles of intermittent DFP adsorption and irradiation measurements, the decomposition rates and formation of residuals on the surface were deduced. It was found that the overall oxidation yield is higher on anatase than rutile. The oxidation rate decreases with increasing irradiation time, an effect that is more pronounced on rutile. We find that both the difference between the polymorphs and the initial decrease of the oxidation yield can largely be explained by variations in surface area rather than poisoning by POx or F species. In particular, we observe a dramatic decrease of the specific area of rutile as a function of photocatalytic oxidation cycle.

  • 53. Kochur, A. G.
    et al.
    Ivanova, T. M.
    Shchukarev, Andrey V.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Linko, R. V.
    Sidorov, A. A.
    Kiskin, M. A.
    Novotortsev, V. M.
    Eremenko, I. L.
    X-ray photoelectron Fe3s and Fe3p spectra of polynuclear trimethylacetate iron complexes2010Inngår i: Journal of Electron Spectroscopy and Related Phenomena, ISSN 0368-2048, E-ISSN 1873-2526, Vol. 180, nr 1-3, s. 21-26Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    X-ray photoelectron Fe3s and Fe3p spectra are employed to study the electron structure and the spin magnetic state of bi-, tri-, and hexa-nuclear trimethylacetate iron complexes. Assignment of the spectra is performed based on an isolated-ion Pauli-Fock calculation of Fe3s and Fe3p spectra of the Fe atoms in bi- and tri-valent states. Nonequivalent Fe(III) and Fe(II) atoms are detected in tri- and hexa-nuclear complexes. Paramagnetic-limit molecular magnetic moments are calculated using effective atomic magnetic moments obtained from spin-sensitive spectral characteristics. Comparison of those values with the magnetic measurements data demonstrates antiferromagnetic interaction within the complexes.

  • 54. Kochur, A. G.
    et al.
    Ivanova, T. M.
    Shchukarev, Andrey V.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Linko, R. V.
    Terebova, N. G.
    Sidorov, A. A.
    Eremenko, I. L.
    Study of the electronic structure of polynuclear cobalt trimethylacetate complexes by Co3s and Co3p X-ray photoelectron spectroscopy2011Inngår i: Russian Journal of Inorganic Chemistry, ISSN 0036-0236, E-ISSN 1531-8613, Vol. 56, nr 3, s. 402-408Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The electronic structure of mono-, hexa-, and nonanuclear cobalt trimethylacetate complexes was studied by XPS. The Co3s- and Co3p X-ray photoelectron spectra of the complexes were recorded. The Co3p spectrum of bivalent cobalt was calculated in the isolated-ion intermediate-coupling approximation. Spectrum analysis showed that the [Co(N-Phobsqdi)2(eta'-N-Ph-opda)(OOCCMe(3))] complex is a strong-field complex with Co(III) in the diamagnetic state; the [Co(dipy)(2)(OOCCMe(3))(2)], [Co(dipyam)(OOCCMe(3))(2)], and [Co(9)(mu(3)-OH)(6)(mu-OOCCMe(3))(12)(OCMe(2))(4)] are high-spin weak-field Co(II) complexes; and the [Co(6)(mu(4)-O)(2)(OOCCMe(3))(10)(THF)(4)] complex contains both the Co(II) and Co(III) atoms. The energy position of major Co3s- and Co3p spectral maxima were found to be sensitive to the nature of the nearest environment of cobalt atoms. The data correlate well with X-ray crystallographic data.

  • 55. Kononova, S V
    et al.
    Kruchinina, E V
    Romashkova, K A
    Potokin, I L
    Shchukarev, Andrey V
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Kudryavtsev, V V
    Phase-inversion gradient-porous films on the basis of polyamidoimides derived from phthalimidobenzenedicarbonyl dichloride and various diamines 2010Inngår i: Russian journal of general chemistry, ISSN 1070-3632, E-ISSN 1608-3350, Vol. 80, nr 10, s. 1977-1985Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Morphology of microporous films prepared from aromatic polyamidoimides under different molding conditions was studied by scanning, transmission, and atomic force microscopy with the specific attention given to the nanosize skin layer. The films were manufactured by the phase inversion molding of aromatic polyamidoimides which were synthesized by low-temperature polycondensation of phthalimidobenzenedicarbonyl dichloride with various diamines. Comparison of the parameters of films, including their wettability and X-ray photoelectron spectroscopy data, gave additional information on factors affecting the mechanism of formation of microporous membranes in the system polymer (polyamidoimide)-solvent (N-methylpyrrolidin-2-one)-non-solvent (water).

  • 56. Konwar, Lakhya Jyoti
    et al.
    Sugano, Yasuhito
    Chutia, Rahul Singh
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Mäki-Arvela, Päivi
    Kataki, Rupam
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Laboratory of Industrial Chemistry & Reaction Engineering, Johan Gadolin Process Chemistry Centre, Åbo Akademi University, Åbo-Turku, FI-20500, Finland.
    Sustainable synthesis of N and P co-doped porous amorphous carbon using oil seed processing wastes2016Inngår i: Materials letters (General ed.), ISSN 0167-577X, E-ISSN 1873-4979, Vol. 173, s. 145-148Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Abstract A facile approach for the sustainable synthesis of amorphous carbons co-doped with N and P (NC) was demonstrated using inexpensive protein rich wastes and H3PO4 as precursors. The prepared NC materials exhibited high degree of aromatization, porosity (specific surface area 435–915 m2/g, pore volume 0.34–0.66 cm3/g) and nitrogen doping levels of 3.4–9.8 at%, depending on intrinsic properties of precursor and synthesis conditions. The materials exhibited electro-catalytic activity for oxygen reduction reaction (ORR) in alkaline electrolytes.

  • 57.
    Kozin, Philipp A
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Boily, Jean-François
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Electrolyte Ion Binding at Iron Oxyhydroxide Mineral Surfaces2013Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 29, nr 39, s. 12129-12137Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Electrolyte ion loadings at the surfaces of synthetic goethite (α-FeOOH) and lepidocrocite (γ-FeOOH) particles that were pre-equilibrated in aqueous solutions of 10 mM NaCl and NaClO4 at 25 °C were investigated by cryogenic X-ray photoelectron spectroscopy (XPS). Atomic concentrations of Cl(-), ClO4(-), and Na(+) were correlated to potential determining ion (pdi; H(+), OH(-)) loadings obtained by potentiometric titrations. While Cl(-) promoted more pdi adsorption than ClO4(-), due to its greater charge-to-size ratio, both ions followed the same loading dependence on pdi adsorption, in contrast to previous studies supporting the concept for negligible perchlorate adorption. Lepidocrocite particles exhibited a stronger response of electrolyte adsorption to pdi loadings due electrolyte ion adsorption on the proton inactive (010) plane. These particles also acquired greater sodium loadings than goethite. These loadings were moreover considerably enhanced by perchlorate adsorption, possibly due to a thickening of the interfacial region in NaClO4 on the (010) plane. Finally, goethite particles with rougher surfaces acquired greater pdi and ion loadings than on those with smoother surfaces. No strong differences could be discerned between Cl(-) and ClO4(-) loadings on these materials. This work thus identified key aspects underpinning the relationship between pdi and electrolyte loadings at FeOOH mineral surfaces of environmental and technological importance.

  • 58. Kukkola, J
    et al.
    Jansson, E
    Popov, A
    Lappalainen, J
    Mäklin, J
    Halonen, N
    Tóth, G
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Jantunen, H
    Kordás, K
    Hast, J
    Hassinen, T
    Sunnari, A
    Jokinen, K
    Haverinen, H
    Sliz, R
    Jabbour, G
    Fabritius, T
    Myllylä, R
    Vasiliev, A
    Zaretskiy, N
    Novel printed nanostructured gas sensors2011Inngår i: Procedia Engineering, ISSN 1877-7058, E-ISSN 1877-7058, Vol. 25, s. 896-899Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    There is a need for low-cost mass-production circuits on various substrates, possibly performing some simple functions as switches, antennas, displays, and sensors. Also in the field of gas sensors widely used in several applications there is a need for such novel fabrication technologies and materials. In this paper, we present three gas sensor structures fabricated using novel printing techniques. Inkjet and gravure printing techniques were used for fabrication of resistive WO3 nanoparticle gas sensors for detection of NO, and inkjet printing was utilized for fabrication of solid electrolyte (mixture of H3PW12O40 and PVC) in a nanostructured Metal-Electrolyte-Insulator- Semiconductor (MEIS) transistor for detection of H2. The sensor structures were found to be sensitive for detection of NO below 10 ppm, and H2 below 100 ppm concentrations in synthetic air, respectively.

  • 59. Kukkola, Jarmo
    et al.
    Mohl, Melinda
    Leino, Anne-Riikka
    Maklin, Jani
    Halonen, Niina
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Konya, Zoltan
    Jantunen, Heli
    Kordas, Krisztian
    Room temperature hydrogen sensors based on metal decorated WO3 nanowires2013Inngår i: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 186, s. 90-95Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The emerging hydrogen economy has created a demand for the development of improved hydrogen sensors operating at room temperature. In this work, we present hydrogen detectors based on metal decorated WO3 nanowires that were able to detect 1000 ppm of H-2, even at room temperature (30 degrees C), with relatively short recovery time and high sensitivity. The nanowires were synthesized by a hydrothermal process and decorated with PdO and PtOx nanoparticles by decomposition of Pd(acac)(2) and Pt(acac)(2) precursors. The gas responses were tested for H-2, NO, H2S and CO analyte gases in an air buffer at 150,200 and 250 degrees C (H-2 also at 30,70 and 130 degrees C).

  • 60. Kukkola, Jarmo
    et al.
    Mohl, Melinda
    Leino, Anne-Riikka
    Toth, Geza
    Wu, Ming-Chung
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Popov, Alexey
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Lauri, Janne
    Riihimaki, Markus
    Lappalainen, Jyrki
    Jantunen, Heli
    Kordas, Krisztian
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Inkjet-printed gas sensors: metal decorated WO3 nanoparticles and their gas sensing properties2012Inngår i: Journal of Materials Chemistry, ISSN 0959-9428, E-ISSN 1364-5501, Vol. 22, nr 34, s. 17878-17886Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Inkjet deposition is an attractive technology to localize nanomaterials in an area-selective manner on virtually any kind of surfaces. Great advantages of the method are effective usage of materials, low processing temperatures and few required manufacturing steps, thus enabling rapid prototyping and bulk production with reasonably low cost. A number of different electrical devices such as light emitting diodes, transistors and solar cells have already been demonstrated, reflecting the versatility of inkjet printing. In this paper, we collect the contemporary results on inkjet deposited gas sensors and show examples of such gas sensing devices based on surface modified WO3 nanoparticles for efficient discrimination of various gaseous analytes from sub-ppm up to nearly 0.1% concentration levels in air.

  • 61. Kukkola, Jarmo
    et al.
    Mäklin, Jani
    Halonen, Niina
    Kyllönen, Teemu
    Tóth, Géza
    Szabó, Maria
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Jantunen, Heli
    Kordás, Krisztián
    Gas sensors based on anodic tungsten oxide2011Inngår i: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 153, nr 2, s. 293-300Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Nanostructured porous tungsten oxide materials were synthesized by the means of electrochemical etching (anodization) of tungsten foils in aqueous NaF electrolyte. Formation of the sub-micrometer size mesoporous particles has been achieved by infiltrating the pores with water. The obtained colloidal anodic tungsten oxide dispersions have been used to fabricate resistive WO3 gas sensors by drop casting the sub-micrometer size mesoporous particles between Pt electrodes on Si/SiO2 substrate followed by calcination at 400 °C in air for 2 h. The synthesized WO3 films show slightly nonlinear current–voltage characteristics with strong thermally activated carrier transport behavior measured at temperatures between −20 °C and 280 °C. Gas response measurements carried out in CO, H2, NO and O2 analytes (concentration from 1 to 640 ppm) in air as well as in Ar buffers (O2 only in Ar) exhibited a rapid change of sensor conductance for each gas and showed pronounced response towards H2 and NO in Ar and air, respectively. The response of the sensors was dependent on temperature and yielded highest values between 170 °C and 220 °C.

  • 62. Kukkola, Jarmo
    et al.
    Rautio, Aatto
    Sala, Giovanni
    Pino, Flavio
    Tóth, Géza
    Leino, Anne-Riikka
    Mäklin, Jani
    Jantunen, Heli
    Uusimäki, Antti
    Kordás, Krisztián
    Gracia, Eduardo
    Terrones, Mauricio
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Electrical transport through single-wall carbon nanotube-anodic aluminum oxide-aluminum heterostructures2010Inngår i: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 21, nr 3, s. 35707-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Aluminum foils were anodized in sulfuric acid solution to form thick porous anodic aluminum oxide (AAO) films of thickness approximately 6 microm. Electrodes of carboxyl-functionalized single-wall carbon nanotube (SWCNT) thin films were inkjet printed on the anodic oxide layer and the electrical characteristics of the as-obtained SWCNT-AAO-Al structures were studied. Nonlinear current-voltage transport and strong temperature dependence of conduction through the structure was measured. The microstructure and chemical composition of the anodic oxide layer was analyzed using transmission and scanning electron microscopy as well as x-ray photoelectron spectroscopy. Schottky emission at the SWCNT-AAO and AAO-Al interfaces allowed by impurity states in the anodic aluminum oxide film together with ionic surface conduction on the pore walls of AAO gives a reasonable explanation for the measured electrical conduction. Calcined AAO is proposed as a dielectric material for SWCNT-field effect transistors.

  • 63. Kwong, Wai Ling
    et al.
    Lee, Cheng Choo
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik.
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Björn, Erik
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Messinger, Johannes
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Department of Chemistry-Ångström Laboratory, Molecular Biomimetics, Uppsala University, 75120 Uppsala, Sweden.
    High-performance iron (III) oxide electrocatalyst for water oxidation in strongly acidic media2018Inngår i: Journal of Catalysis, ISSN 0021-9517, E-ISSN 1090-2694, Vol. 365, s. 29-35Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Stable and efficient oxygen evolution reaction (OER) catalysts for the oxidation of water to dioxygen in highly acidic media are currently limited to expensive noble metal (Ir and Ru) oxides since presently known OER catalysts made of inexpensive earth-abundant materials generally suffer anodic corrosion at low pH. In this study, we report that a mixed-polymorph film comprising maghemite and hematite, prepared using spray pyrolysis deposition followed by low-temperature annealing, showed a sustained OER rate (>24 h) corresponding to a current density of 10 mA cm−2 at an initial overpotential of 650 mV, with a Tafel slope of only 56 mV dec−1 and near-100% Faradaic efficiency in 0.5 M H2SO4 (pH 0.3). This performance is remarkable, since iron (III) oxide films comprising only maghemite were found to exhibit a comparable intrinsic activity, but considerably lower stability for OER, while films of pure hematite were OER-inactive. These results are explained by the differences in the polymorph crystal structures, which cause different electrical conductivity and surface interactions with water molecules and protons. Our findings not only reveal the potential of iron (III) oxide as acid-stable OER catalyst, but also highlight the important yet hitherto largely unexplored effect of crystal polymorphism on electrocatalytic OER performance.

  • 64. Kwong, Wai Ling
    et al.
    Lee, Cheng Choo
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik.
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Messinger, Johannes
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Department of Chemistry-Ångström Laboratory, Molecular Biomimetics, Uppsala University, 75120 Uppsala, Sweden.
    Cobalt- doped hematite thin films for electrocatalytic water oxidation in highly acidic media2019Inngår i: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 55, nr 34, s. 5017-5020Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Earth-abundant cobalt-doped hematite thin-film electrocatalysts were explored for acidic water oxidation. The strategically doped hematite produced a stable geometric current density of 10 mA cm(-2) for up to 50 h at pH 0.3, as a result of Co-enhanced intrinsic catalytic activity and charge transport properties across the film matrix.

  • 65. Leino, Anne-Riikka
    et al.
    Mohl, Melinda
    Kukkola, Jarmo
    Mäki-Arvela, Päivi
    Kokkonen, Tommi
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Kordas, Krisztian
    Low-temperature catalytic oxidation of multi-walled carbon nanotubes2013Inngår i: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 57, s. 99-107Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    When in a pure form, carbon nanotubes are known to be stable in air up to ∼800 K making them attractive for a large variety of applications. In this work, we report a significant decrease of ignition temperature (in some cases occurring at ∼500 K) and a reduction in the apparent activation energy for oxidation in air as a result of impregnation with nanoparticles (<2 nm) of metal (Pt, Pd, Ni and Co) acetylacetonates or by decoration with corresponding oxides. Surprisingly, defects introduced by partial oxidation of the carbon nanotubes do not in practice have any influence on the enhancement of further oxidation. Reduction temperatures of metal oxides with H2 were close to those of other carbon supported catalyst materials. However, the carbon nanotubes showed a tendency for low temperature gasification in the presence of hydrogenation catalyst metals (Pt, Pd).

  • 66. Leino, Ewelina
    et al.
    Kumar, Narendra
    Maki-Arvela, Paivi
    Aho, Atte
    Kordas, Krisztian
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. University of Oulu, Oulu, Finland.
    Leino, Anne-Riikka
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Murzin, Dmitry Yu
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Åbo Akademi University, Turku/Åbo, Finland.
    Influence of the synthesis parameters on the physico-chemical and catalytic properties of cerium oxide for application in the synthesis of diethyl carbonate2013Inngår i: Materials Chemistry and Physics, ISSN 0254-0584, E-ISSN 1879-3312, Vol. 143, nr 1, s. 65-75Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Synthesis of cerium (IV) oxide by means of room temperature precipitation method was carried out. The effect of preparation variables such as synthesis time, calcination temperature and pH of the solution on resulting CeO2 properties was discussed. Moreover, the comparison of CeO2 samples prepared in a static and rotation mode of synthesis is presented. The solid catalysts were characterized by means of X-ray powder diffraction, scanning electron microscopy, transmission electron microscope, nitrogen physisorption, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy using pyridine as a probe molecule and temperature programmed desorption of CO2. Significant variations in physicochemical properties of CeO2 by varying the preparation conditions were observed. Furthermore, the catalytic performances of CeO2 catalysts were compared in the synthesis of diethyl carbonate starting from ethanol and CeO2 using butylene oxide as a dehydrating agent. The dependence of CeO2 properties on its catalytic activity is evaluated in detail. (C) 2013 Elsevier B.V. All rights reserved.

  • 67. Leino, Ewelina
    et al.
    Mäki-Arvela, Päivi
    Eta, Valerie
    Kumar, Narendra
    Demoisson, Frédéric
    Ajaikumar, Samikannu
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Leino, Anne-Riikka
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Murzin, Dmitry Yu
    Kordás, Krisztián
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    The influence of various synthesis methods on the catalytic activity of cerium oxide in one-pot synthesis of diethyl carbonate starting from CO2, ethanol and butylene oxide2013Inngår i: Catalysis Today, ISSN 0920-5861, E-ISSN 1873-4308, Vol. 210, s. 47-54Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Different synthesis methods such as homogeneous precipitation at room temperature and supercritical water (T > 647 K and P > 22.1 MPa) were employed for cerium oxide preparation. Additionally, deposition of ceria on silica mesoporous material, SBA-15, was carried out. The obtained materials were characterized by means of X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, nitrogen physisorption, X-ray photoelectron spectroscopy and CO2 temperature programmed desorption. Considerable variations in physico-chemical properties of the resulting materials were observed. The catalytic activities of pristine cerium oxide and ceria loaded on SBA-15 support were compared. The test reaction was synthesis of diethyl carbonate starting from carbon dioxide and ethanol using butylene oxide as the dehydrating agent.

  • 68.
    Leone, Laura
    et al.
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Kemi.
    Ferri, Diego
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Kemi.
    Manfredri, Carla
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Kemi.
    Persson, Per
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Kemi.
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Kemi.
    Sjöberg, Staffan
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Kemi.
    Loring, John
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Kemi.
    Modeling the Acid-Base Properties of Bacterial Surfaces: A Combined Spectroscopic and Potentiometric Study of the Gram-Positive Bacterium Bacillus subtilis2007Inngår i: Environmental Science & Technology, Vol. 41, nr 18, s. 6465-71Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this study, macroscopic and spectroscopic data were combined to develop a surface complexation model that describes the acid-base properties of Bacillus subtilis. The bacteria were freeze-dried and then resuspended in 0.1 M NaCl ionic medium. Macroscopic measurements included potentiometric acid-base titrations and electrophoretic mobility measurements. In addition, ATR-FTIR spectra of wet pastes from suspensions of Bacillus subtilis at different pH values were collected. The least-squares program MAGPIE was used to generate a surface complexation model that takes into account the presence of three acid-base sites on the surface: COOH, NH+, and PO-, which were identified previously by XPS measurements. Both potentiometric titration data and ATR-FTIR spectra were used quantitatively, and electrostatic effects at the charged bacterial surface were accounted for using the constant capacitance model. The model was calculated using two different approaches: in the first one XPS data were used to constrain the ratio of the total concentrations of all three surface sites. The capacitance of the double layer, the total buffer capacity, and the deprotonation constants of the NH+, POH, and COOH species were determined in the fit. A second approach is presented in which the ratio determined by XPS of the total concentrations of NH+ to PO- sites is relaxed. The total concentration of PO- sites was determined in the fit, while the deprotonation constant for POH was manually varied until the minimization led to a model which predicted an isoelectric point that resulted in consistency with electrophoretic mobility data. The model explains well the buffering capacity of Bacillus subtilis suspensions in a wide pH range (between pH = 3 and pH = 9) which is of considerable environmental interest. In particular, a similar quantitative use of the IR data opens up possibilities to model other bacterial surfaces at the laboratory scale and help estimate the buffering capacity of carboxylate-containing compounds in natural samples.

  • 69.
    Leone, Laura
    et al.
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Kemi.
    Loring, John
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Kemi.
    Sjöberg, Staffan
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Kemi.
    Persson, Per
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Kemi.
    Shchukarev, Andrey
    Surface characterization of the Gram-positive bacteria Bacillus subtilis-an XPS study2006Inngår i: Surface and Interface Analytsis, Vol. 38, s. 202-5Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Interactions at the bacteria-solid interface in aquatic environments are of crucial importance in biofilm formation processes. The characterization of microbial surfaces properties is therefore a very important step for the understanding of these interactions. In this study, XPS spectra of Bacillus subtilis wet pastes centrifuged from suspensions over a span of pH values were recorded using a fast-freezing procedure. The chemical composition of the bacterial surface was elucidated and the presence of surface sites containing carboxylate, phosphate and amine functional groups was established. It was possible to distinguish between charged and uncharged amine sites on the surface and follow their deprotonation reactions as a function of pH. It is suggested that increased metabolic activity around the physiological pH results in the excretion of proteins and/or peptides which are possibly related to the production of extracellular polymeric substances (EPS). Copyright © 2006 John Wiley & Sons, Ltd.

  • 70. Li, Man-Bo
    et al.
    Posevins, Daniels
    Gustafson, Karl P. J.
    Tai, Cheuk-Wai
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Qiu, Youai
    Backvall, Jan-E.
    Diastereoselective Cyclobutenol Synthesis: A Heterogeneous Palladium-Catalyzed Oxidative Carbocyclization-Borylation of Enallenols2019Inngår i: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 25, nr 1, s. 210-215Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A highly selective and efficient oxidative carbocyclization/borylation of enallenols catalyzed by palladium immobilized on amino-functionalized siliceous mesocellular foam (Pd-AmP-MCF) was developed for diastereoselective cyclobutenol synthesis. The heterogeneous palladium catalyst can be recovered and recycled without any observed loss of activity or selectivity. The high diastereoselectivity of the reaction is proposed to originate from a directing effect of the enallenol hydroxyl group. Optically pure cyclobutenol synthesis was achieved by the heterogeneous strategy by using chiral enallenol obtained from kinetic resolution.

  • 71.
    Lucas, Marie
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Yeşilbaş, Merve
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Boily, Jean-Francois
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    X-ray photoelectron spectroscopy of fast-Frozen hematite colloids in aqueous solutions. 6. Sodium halide (F–, Cl–, Br–, I–) ion binding on microparticles2018Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 34, nr 45, s. 13497-13504Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Electrolyte ion binding at mineral surfaces is central to the generation of surface charge and key to electric double-layer formation. X-ray photoelectron spectroscopy of fast-frozen (−170 °C) mineral wet pastes provides a means to study weakly bound electrolyte ions at the mineral/water interface. In this study, we build upon a series of articles devoted to ion binding at hematite (α-Fe2O3) particle surfaces to resolve the nature of sodium halide ion binding. Measurements on micron-sized hematite particles terminated by the charged and amphoteric (012) and the relatively uncharged (001) faces point to the formation of salt loadings of similar composition to those of cryosalts of NaCl, NaBr, NaI, and NaF. These coatings could be likened to those of the better-known hydrohalite (NaCl·2H2O) phase, one that typically forms under concentrated (≫0.1 M) aqueous solutions of NaCl under freezing conditions. As we have previously shown that these reaction products do not occur in nanosized hematite particles, our work points to the involvement of the basal (001) face and/or the juxtaposition of these faces in packed tabular microparticles of hematite (1–3 μm in width) in stabilizing these cryosalts. One possible formation pathway involves first-layer Na+ and Cl– ions serving as an anchoring layer for a topotactic-like growth of amorphous to low-crystalline salt hydrates at the (001) face. Thus, by contrasting reaction products of four sodium halides at surfaces of tabular microparticles of hematite, this work revealed the formation of cryosalt-like solids. The formation of such solids may have especially important ramifications to ice nucleation mechanisms in the atmosphere, as well as in saline permafrosts on Earth and on planet Mars where salt-laden mineral particles prevail.

  • 72.
    Martin, Sebastien
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Rennes Cedex 7, France.
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Hanna, Khalil
    Rennes Cedex 7, France.
    Boily, Jean-Francois
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Kinetics and Mechanisms of Ciprofloxacin Oxidation on Hematite Surfaces2015Inngår i: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 49, nr 20, s. 12197-12205Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Adsorption of antibiotics at mineral surfaces has been extensively studied over the past 20 years, yet much remains to be learned on their interfacial properties and transformation mechanisms. In this study, interactions of Ciprofloxacin (CIP), a fluoroquinolone antibiotic with two sets of synthetic nanosized hematite particles, with relatively smooth (H10, 10-20 nm in diameter) and roughened (H80, 80-90 nm in diameter) surfaces, were studied by means of liquid chromatography (LC), mass spectrometry (MS), and spectroscopy (vibration and X-ray photoelectron). Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) spectroscopy provides evidence for inner-sphere bidentate complex formation of CIP at hematite surfaces in 0.01 M NaCl, irrespective of pH and particle size. ATR-FTIR spectroscopy also revealed that the sorbed mother CIP molecule decayed to other surface species over a period of at least 65 h. This was supported by the detection of three daughter products in the aqueous phase by LC/MS. The appearance of NH3+ groups during the course of these experiments, revealed by cryogenic XPS, provides further evidence that CIP oxidation proceeds through an opening of piperazine ring via N-dealkylation. Additional in vacuo FTIR experiments under temperature-programmed desorption also showed that oxidation of sorbed byproducts were effectively degraded beyond 450 degrees C, a result denoting considerably strong (inter)molecular bonds of both mother and daughter products. This work also showed that rougher, possibly multidomainic particles (H80) generated slower rates of CIP decomposition but occurring through more complex schemes than at smoother particle surfaces (H10). This work thus uncovered key aspects of the binding of an important antibiotic at iron oxide surfaces, and therefore provided additional constraints to our growing understanding of the fate of emerging contaminants in the environment.

  • 73. Masoud, Taheri
    et al.
    Mehran, Ghiaci
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    A comparison between two Pd‐Ni catalysts supported on two different supports toward Suzuki‐Miyaura coupling reaction2018Inngår i: Applied organometallic chemistry, ISSN 0268-2605, E-ISSN 1099-0739, Vol. 32, nr 5, artikkel-id e4338Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    When a single metal fails to promote an efficient Suzuki?Miyaura coupling reaction at ambient temperature, the synergistic cooperation of two distinct metals might improve the reaction. To examine the synergistic effect of palladium and nickel for catalyzing Suzuki coupling reaction, g?C3N4 supported metal nanoparticles of PdO, NiO and Pd?PdO?NiO were prepared, characterized and their catalytic activities evaluated over different aryl halides at room temperature and 78 °C. The morphological characterization of Pd?PdO?NiO/g?C3N4 demonstrated that the bimetallic particles were uniformly dispersed over the g?C3N4 layers with diameters ranging from 3.5?7.7 nm. XPS analysis showed that nanoparticles of Pd?PdO?NiO consisted of Pd(II), Pd(0) and Ni(II) sites. The experiments performed on the catalytic activity of Pd?PdO?NiO/g?C3N4 showed that the prepared catalyst demonstrated an efficient activity without using toxic solvents.

  • 74. Mikhlin, Yuri
    et al.
    Karacharov, Anton
    Tomashevich, Yevgeny
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Cryogenic XPS study of fast-frozen sulfide minerals: Flotation-related adsorption of n-butyl xanthate and beyond2016Inngår i: Journal of Electron Spectroscopy and Related Phenomena, ISSN 0368-2048, E-ISSN 1873-2526, Vol. 206, s. 65-73Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Cryogenic XPS of wet particulate samples separated via centrifugation and fast-frozen allows quasi in situ examination of solid surfaces, adsorbates, and reaction products, largely preventing the loss both of volatiles and hydrated species at mineral/water interfaces. Here, the cryo-XPS has been applied to characterize the surfaces and interfacial layers of natural pyrite (FeS2), chalcopyrite (CuFeS2), and galena (PbS) in solutions of a common flotation collector, potassium n-butyl xanthate (KBX), in conjunction with zeta-potential measurement. It was found, in particular, that dibutyl dixanthogen was the major adsorbate at pyrite in 0.1 mM KBX and 10 mM KBX solutions; dixanthogen and cuprous xanthate in the next stage were formed on chalcopyrite, and predominant chemisorbed butyl xanthate was present at galena, including in 10 mM KBX solution. The results may suggest that the production of dixanthogens at the interface has been underestimated while the quantities of surface metal xanthates could be over evaluated in previous studies. Pronounced differential charging effects were observed in the XPS experiment for the samples moderately hydrophobized by the xanthate treatment; we proposed that the effect was due to electrically isolated mineral particles with hydrophobic and ice-repellent surfaces, which retained, however, some frozen water islets.

  • 75. Mikhlin, Yuri
    et al.
    Karacharov, Anton
    Tomashevich, Yevgeny
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Interaction of sphalerite with potassium n-butyl xanthate and copper sulfate solutions studied by XPS of fast-frozen samples and zeta-potential measurement2016Inngår i: Vacuum, ISSN 0042-207X, E-ISSN 1879-2715, Vol. 125, s. 98-105Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We acquired low-temperature X-ray photoelectron spectra of fast-frozen wet pastes prepared by centrifugation of the natural sphalerite slurries containing potassium n-butyl xanthate (KBX), without washing or any additional treatment, before and after the mineral activation in 0.1 mM CuSO4 solution. Zeta potentials of the slurry particles were also measured. The method allowed characterizing the mineral surfaces and adsorbates, volatile substances and hydrated species within the interfacial layers under more realistic flotation-related conditions. The uptake of xanthate by unactivated mineral was low even in 10 mM KBX, while the surface became metal-deficient (enriched in sulfur), more hydrophobic and contaminated with carbonaceous matter. Dibutyl dixanthogen was the major interfacial product of the interaction of Cu-activated sphalerite having the surface atomic Zn/Cu ratio of 3 and excess of sulfur with the KBX solutions. The spectra revealed only minor quantities of Zn and Cu xanthates and oxyhydroxides at all the samples; some hydrated K+ counter-ions were detected at the negatively charged surfaces after the xanthate treatment. The dixanthogen was concluded to form via oxidation of xanthate at the interface, probably catalyzed by surface cuprous species but not direct interaction with cupric ions.

  • 76.
    Mladenovic, Zivko
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi.
    Sahlin-Platt, Annika
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi.
    Andersson,, Martin
    Department of Chemical and Biological Engineering, Chalmers University of Technology, Göteborg, Sweden.
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Ransjö, Maria
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi.
    Investigation of surface reactions and solid-solution interfaces of three bonegraft substitute materials incubated in cell culture mediumArtikkel i tidsskrift (Annet vitenskapelig)
  • 77.
    Mladenovic, Zivko
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi.
    Sahlin-Platt, Annika
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi.
    Bengtsson, Åsa
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Ransjö, Maria
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi.
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Surface characterization of bone graft substitute materials conditioned in cell culture medium2010Inngår i: Surface and Interface Analysis, ISSN 0142-2421, E-ISSN 1096-9918, Vol. 42, nr 6-7, s. 452-456Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Biomaterials are widely used in clinical practice as bone graft substitutes for treating patients with bone defects. A molecular level understanding of the chemical processes at the interface between the biomaterial and the biological environment is crucial to succeed in tissue regeneration and to predict the treatment outcome. In this study, we used three different bone graft substitute materials (BioGlass 45S5—synthetic, Bio-Oss—bovine derived and Algipore—derived from algae) which were incubated in an α-minimum essential medium (α-MEM) during 1, 3 and 7 days. Initial surface composition of the biomaterials and the chemistry of their solid–solution interface were monitored by XPS with a fast-frozen samples technique. The XPS analysis showed that the equilibrium at the solid-solution interface is reached within 24 h. The Na/Cl atomic ratio at equilibrium indicates a negatively charged surface for Bio-Oss. In contrast, the other two materials gained a positive surface charge, which resulted in pronounced adsorption of amino acids at the interface from the medium. The surface chemical reconstruction and charge generation mechanism responsible for this effect are discussed with regard to bulk composition of the materials and possible proliferation and differentiation cell patterns that could be expected at the interface. Copyright © 2010 John Wiley & Sons, Ltd.

  • 78.
    Nelson, Hanna
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Sjöberg, Staffan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Lövgren, Lars
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Composition and solubility of precipitated copper(II) arsenates2011Inngår i: Applied Geochemistry, ISSN 0883-2927, E-ISSN 1872-9134, Vol. 26, nr 5, s. 696-704Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Equilibrium reactions involving Cu(II) and As(V) have been studied with respect to formation of complexes in aqueous solutions as well as formation of solid phases. Potentiometric titrations performed at 25 °C (I = 0.1 M Na(Cl)) and at different Cu to As ratios gave no evidence for the existence of Cu(II) arsenate complexes in solution below the pH of the precipitation boundaries (pH ≈ 4), irrespective of the Cu to As ratio and pH. Mixing of solutions of Cu(II) and As(V) at different proportions and adjusting pH to values ranging from 4 to 9 resulted in precipitation of five different solid phases. The elemental composition of the solids was determined using X-ray Photoelectron Spectroscopy, and Environmental Scanning Microscopy–Field Emission Gun equipped with an energy dispersive spectroscopy detector. The average Cu/As ratio was determined by dissolving the solids. Total soluble concentrations of the components Cu(II) and As(V), as well as the basicity of the solid phases were determined by analysis of aqueous solutions. Based upon these experimental data the stoichiometric composition of the solid phases and their stability were determined. The resulting equilibrium model includes the solid phases Cu3(AsO4)2, Cu3(AsO4)(OH)3, Cu2(AsO4)(OH), Cu5Na(HAsO4)(AsO4)3 and Cu5Na2AsO4)4, where Cu5Na(HAsO4)(AsO4)3 and Cu5Na2(AsO4)4 have not been reported previously. In 0.1 M Na(Cl), Na+ was found to be a significant component in two of the solid phases. The Cu5Na2(AsO4)4 was formed in weakly alkaline conditions with pNa < 2.5. Stability constants for all solid phases have been determined. Distribution diagrams as well as predominance area (pNa–pH) diagrams are presented to illustrate stability fields of the different solid phases.

  • 79.
    Ngoc Pham, Tung
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Univ Danang, Univ Sci & Technol, Dept Chem, 54 Nguyen Luong Bang, Lien Chieu, Danang, Vietnam.
    Sharifi, Tiva
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Sandström, Robin
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Siljebo, William
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Kordas, Krisztian
    Wågberg, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Åbo Akad Univ, Dept Chem Engn, Proc Chem Ctr, Ind Chem & React Engn, FI-20500 Turku, Finland.
    Robust hierarchical 3D carbon foam electrode for efficient water electrolysis2017Inngår i: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 7, artikkel-id 6112Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Herein we report a 3D heterostructure comprising a hierarchical macroporous carbon foam that incorporates mesoporous carbon nanotubes decorated with cobalt oxide nanoparticles as an unique and highly efficient electrode material for the oxygen evolution reaction (OER) in electrocatalytic water splitting. The best performing electrode material showed high stability after 10 h, at constant potential of 1.7 V vs. RHE (reversible hydrogen electrode) in a 0.1 M KOH solution and high electrocatalytic activity in OER with low overpotential (0.38 V vs RHE at 10 mA cm(-2)). The excellent electrocatalytic performance of the electrode is rationalized by the overall 3D macroporous structure and with the firmly integrated CNTs directly grown on the foam, resulting in a large specific surface area, good electrical conductivity, as well as an efficient electrolyte transport into the whole electrode matrix concurrent with an ability to quickly dispose oxygen bubbles into the electrolyte. The eminent properties of the three-dimensional structured carbon matrix, which can be synthesized through a simple, scalable and cost effective pyrolysis process show that it has potential to be implemented in large-scale water electrolysis systems.

  • 80.
    Nguyen, Anh Mai
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Nordborg, Anna
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Irgum, Knut
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Thermally induced dissolution/precipitation: A simple approach for the preparation of Macroporous Monoliths from Linear Aliphatic Polyamides2009Inngår i: Journal of Separation Science, ISSN 1615-9306, E-ISSN 1615-9314, Vol. 32, nr 15-16, s. 2619-2628Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A versatile way of preparing macroporous monolithic materials from linear aliphatic polyamides is presented. Simply, polyamide pellets were treated in benzyl alcohol (BA) at elevated temperature, causing dissolution by interchain hydrogen bond disruption. Subsequent cooling below the upper critical solution temperature (UCST) resulted in precipitation and partial restoration of the semicrystalline polymer, which is organized into network structures. The final steps were a solvent exchange of BA for methanol, followed by drying to form monolithic entities. A number of polyamides ranging from hydrophilic to hydrophobic were tested and under the experimental conditions, poly(1-aza-2-cycloheptanone (PA6) and (poly-[imino-1,6-hexanediylimino{1,10-dioxo-1,10-decanediyl}] (PA610) yielded entities with macroporous properties that were deemed useful for liquid chromatography. The morphological features and porous properties of the monoliths produced by this dissolution-precipitation procedure were studied by scanning electron microscopy, adsorption/desorption of N2(g) according to the Brunauer-Emmett-Teller (BET) principle, and mercury intrusion porosimetry. Degradation of the polymer backbone was noticeable when the dissolution time was extended and shortening of the polymer chains was confirmed by MALDI-MS, viscosity measurements, X-ray photoelectron spectroscopy (XPS), and potentiometric titration. When the heating was limited to the time it took to dissolve the polymers, mechanically stable monoliths could be obtained. The dissolution/heat treatment time further seemed to be useful for controlling the macroporous morphology.

  • 81.
    Nordborg, Anna
    et al.
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Kemi.
    Limé, Fredrik
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Kemi.
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Kemi.
    Irgum, Knut
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Kemi.
    A cation-exchange material for protein separations based on grafting of thiol-terminated sulfopropyl methacrylate telomers onto hydrophilized monodisperse divinylbenzene particles2008Inngår i: Journal of Separation Science, ISSN 1615-9306, E-ISSN 1615-9314, Vol. 31, nr 12, s. 2143-2150Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A strong cation-exchange separation material has been prepared from monodisperse divinylbenzene particles modified by a grafting to approach, utilizing as anchoring points epoxy groups introduced onto the surface of the particles via oxidation of residual vinyl groups. The grafted chains consisted of thiol-terminated telomers of sulfopropyl methacrylate prepared by iniferter mediated polymerization, and grafting was performed by reaction of the corresponding thiolate anion with the surface epoxy groups. Attachment through epoxy moieties that were subsequently converted into 2,3-propanediol groups increased the hydrophilicity of the polymeric particles and incubation experiments showed no signs of the proteins denaturing on the column during an extended contact time of 1 h at room temperature. The performance of the grafted material was demonstrated by the chromatographic separation of cytochrome C, lysozyme, myoglobin, and ribonuclease A, in a cation-exchange mode.

  • 82. Nuri, Ayat
    et al.
    Mansoori, Yagoub
    Bezaatpour, Abolfazl
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Johan Gadolin Process Chemistry Centre, Laboratory of Industrial Chemistry, Åbo Akademi University, Turku-Åbo, Finland.
    Magnetic Mesoporous SBA-15 Functionalized with a NHC Pd(II) Complex: An Efficient and Recoverable Nanocatalyst for Hiyama Reaction2019Inngår i: ChemistrySelect, ISSN 2365-6549, Vol. 4, nr 5, s. 1820-1829Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Magnetite nanoparticles (MNPs) were covered by a silica shell and then embedded into mesoporous silica (SBA‐15). Magnetic mesoporous silica (Fe3O4@SiO2‐SBA) was then reacted with 3‐chloropropyltriethoxysilane (CPTS), sodium salt of imidazole and 2‐bromopyridine to give Fe3O4@SiO2‐SBA functionalized with 3‐(pyridin‐2‐yl)‐1H‐imidazol‐3‐ium‐propyl (PIP) as a supported pincer ligand for Pd(II). The functionalized magnetic mesoporous silica were then treated with t‐BuOK at −80 °C in THF and then reacted with [PdCl2(SMe2)2] to give supported Pd(II)‐carbene complex containing C,N‐bidentate ligand. The chloride ions were then exchanged by bromide ions using a NaBr solution of diethylether/acetone mixture. The prepared catalyst was characterized with, FT‐IR, thermo gravimetric analysis (TGA), scanning electron microscopy (SEM), transmission electron microscopy (TEM), vibrating sample magnetometry (VSM), Brunauer–Emmett–Teller surface area measurement (SBET), energy dispersive X‐ray analysis (EDX) and wide angle X‐ray diffraction spectroscopy (XRD). The prepared magnetic catalyst was effectively used in the coupling reaction of triethoxyphenylsilane with aryl halides (Hiyama reaction) in the presence of a base. The reaction parameters such as solvents, amount of catalyst, base and temperature were optimized. The catalyst was then magnetically decanted, washed, and reused several times.

  • 83.
    Persson, Ylva
    et al.
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Kemi.
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Kemi.
    Öberg, Lars
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Kemi.
    Tysklind, Mats
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Kemi.
    Dioxins, chlorophenols and other chlorinated organic pollutants in colloidal and water fractions of groundwater from a contaminated sawmill site2008Inngår i: Environmental Science and Pollution Research, Vol. 15, nr 6, s. 463-71Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Background, aim, and scope The distribution of chlorinated organic contaminants in groundwater and the importance of colloids were studied in groundwater from a sawmill site contaminated by chlorophenol preservatives.

    Materials and methods The groundwater was fractionated into three different size ranges: (1) >0.7 μm, (2) 0.4–0.7 μm and (3) 0.2–0.4 μm and the filtered water phase. The concentrations of chlorophenols (CP), chlorinated phenoxy phenols (PCPP), chlorinated diphenyl ethers (PCDE), chlorinated dibenzofurans (PCDF) and chlorinated dibenzo-p-dioxins (PCDD) were determined in each fraction. The colloids were characterised regarding the chemical composition using X-ray photoelectron spectroscopy (XPS).

    Results Chlorophenols were mostly found in the water fraction and PCDD/Fs were found almost exclusively in the particulate fractions. For example, the filtered water phase contained 2,100 μg l−1 and 0.72 ng l−1 for CPs and PCDD/Fs, respectively, and the particulate fractions contained 27 μg l−1 and 32 ng l−1 for CPs and PCDD/Fs, respectively. XPS evaluation of the particulate phases showed no correlation between the surface chemistry of the particle properties and the distribution of chlorinated compounds.

    Discussion The results suggest that groundwater transport of CPs, PCPPs, PCDEs and PCDD/Fs may occur from contaminated sawmill sites and that the colloid-facilitated transport, especially of PCDD/Fs, is substantial. The results correlated well with previous studies of compounds sorbed to dissolved organic carbon, which indicate that dissolved and colloidal organic carbon facilitated the transport of PCDEs, PCDFs and PCDDs particularly.

    Conclusions Several classes of chlorinated compounds were readily detected in the groundwater samples. Due to the differences in their physicochemical properties, CPs, PCPPs, PCDEs and PCDD/Fs vary in their partitioning between colloidal fractions and the filtered groundwater. The proportion of the bound fraction increased with an increasing hydrophobicity of the chlorinated compounds. The groundwater transport of colloid-associated pollutants from the site may be significant.

    Recommendations and perspectives The results imply that colloidal particles <0.7 μm are freely mobile in groundwater from this site. The groundwater transport of colloid-associated pollutants may be significant. However, the extent of the problem is not yet known and, thus, further research is needed to evaluate the impact of colloidal transport of hydrophobic organic contaminants. In Sweden alone, 400 to 500 sawmill sites are estimated to be contaminated with PCDD/Fs as a result of the former use of CP-based wood preservatives. The widespread use of CP mixtures for a variety of applications, including wood preservation, indicates that potential colloidal transport will be an issue of concern in many countries.

  • 84.
    Phal, Sereilakhena
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Lindholm-Sethson, Britta
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Geladi, Paul
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Tesfalidet, Solomon
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Determination of methotrexate in spiked human blood serum using multi-frequency electrochemical immittance spectroscopy and multivariate data analysis2017Inngår i: Analytica Chimica Acta, ISSN 0003-2670, E-ISSN 1873-4324, Vol. 987, s. 15-24Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This article describes an attempt to develop a sensor based on multi-frequency immittance spectroscopy for the determination of methotrexate (MTX) in blood serum using gold electrodes modified with antibodies. The attachment of antibodies was monitored with electrochemical immittance spectroscopy (EIS) and X-ray photoelectron spectroscopy (XPS). The EIS measurements of MTX resulted in a data matrix of size 39 × 55. The data were analysed using multivariate data analysis and showed a concentration dependence and time dependence that could be separated. This allowed the calculation of a multivariate calibration model. The model showed good linear behavior on a logarithmic scale offering a detection limit of 5 × 10−12 mol L−1.

  • 85.
    Ramstedt, Madeleine
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Andersson, Britt M.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Sjöberg, Staffan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Surface properties of hydrous manganite (-MnOOH): A potentiometric, electroacoustic, and x-ray photoelectron spectroscopy study2004Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 20, nr 19, s. 8224-8229Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The acid-base characteristics of the manganite (-MnOOH) surface have been studied at pH above 6, where dissolution is negligible. Synthetic microcrystalline particles of manganite were used in the experiments. From potentiometric titrations, electrophoretic mobility measurements, and X-ray photoelectron spectroscopy (XPS), a one pKa model was constructed that describes the observed behavior. The data show no ionic strength effect at pH < 8.2, which is the pH at the isoelectric point (pHiep), but ionic strength effects were visible above this pH. To explain these observations, Na+ ions were suggested to form a surface complex. The following equilibria were established: =MnOH2+1/2 =MnOH-1/2 + H+, log 0 (intr.) = -8.20; =MnOH2+1/2 + Na+ =MnOHNa+1/2 + H+, log 0 (intr.) = -9.64. The excess of Na+ at the surface was supported by XPS measurements of manganite suspensions containing 10 mM NaCl. The dielectric constant of synthetic manganite powder was also determined in this study.

  • 86.
    Ramstedt, Madeleine
    et al.
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Kemi.
    Ekstrand-Hammarström, Barbro
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Kemi.
    Bucht, Anders
    Umeå universitet, Medicinsk fakultet, Folkhälsa och klinisk medicin, Lungmedicin.
    Österlund, Lars
    Welch, Martin
    Huck, Wilhelm T.S.
    Bacterial and mammalian cell response to poly(3-sulfopropyl methacrylate) brushes loaded with silver halide salts2009Inngår i: Biomaterials, Vol. 30, nr 8, s. 1524-31Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This study investigates the antibacterial and cytotoxic effect of surfaces with sulphonate brushes containing silver salts. By using the same type of samples for both cytotoxicity and antibacterial studies, these two parameters could be compared in a controlled way. The silver was incorporated into the brush in four different forms to enable release of silver ions at different concentrations and different rates. It was found that although the surfaces displayed very good antibacterial properties in buffer solutions, this effect disappeared in systems with high protein content. Similarly, the silver-containing surfaces displayed cytotoxic effects in the absence of serum proteins but this effect was reduced in the presence of serum. The speciation of silver in the different solutions is discussed. Cytotoxic and antibacterial effects are compared at the different silver concentrations released. The implications of a concentration range where silver could be used to kill bacterial without harmful effects on mammalian cells are also discussed and questioned.

  • 87.
    Ramstedt, Madeleine
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Leone, Laura
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Persson, Per
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Cell wall composition of Bacillus subtilis changes as a function of pH and Zn2+ exposure: insights from cryo-XPS measurements2014Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 30, nr 15, s. 4367-4374Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Bacteria play an important role in the biogeochemical cycling of metals in the environment. Consequently, there is an interest to understand how the bacterial surfaces interact with metals in solution and how this affects the bacterial surface. In this work we have used a surface-sensitive analysis technique, cryogenic X-ray photoelectron spectroscopy (cryo-XPS), to monitor the surface of Bacillus subtilis cells as a function of pH and Zn2+ content in saline solution. The objective of the study was twofold: (1) to investigate the agreement between two data treatment methods for XPS, as well as investigate to what extent sample pretreatment may influence XPS data of bacterial samples, and (2) to characterize how the surface chemistry of bacterial cells is influenced by different external conditions. (1) It was found that the two data treatment methods gave rise to comparable results. However, identical samples analyzed fast-frozen or dry exhibited larger differences in surface chemistry, indicating that sample pretreatment can to large extents influence the obtained surface composition of bacterial samples. (2) The bacterial cell wall (in fast-frozen samples) undergoes dramatic compositional changes with pH and with Zn2+ exposure. The compositional changes are interpreted as an adaptive metal resistance response changing the biochemical composition of the bacterial cell wall. These results have implications for how adsorption processes at the surface of bacterial cells are analyzed, understood, modeled, and predicted. 

  • 88.
    Ramstedt, Madeleine
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Leone, Laura
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Bacterial surfaces in geochemistry: how can x-ray photoelectron spectroscopy help?2019Inngår i: Analytical geomicrobiology: a handbook of instrumental techniques / [ed] Janice P. L. Kenney, Harish Veeramani, Daniel S. Alessi, Cambridge: Cambridge University Press , 2019, s. 262-287Kapittel i bok, del av antologi (Annet vitenskapelig)
    Abstract [en]

    Processes occurring at surfaces and interfaces are very important in environmental systems, necessitating surface-specific characterization tools that can help us understand processes at and specific properties of surfaces and interfaces, and their role in biogeochemical systems. This chapter describes the use and application of X-ray photoelectron spectroscopy (XPS) to study interfacial processes of relevance for geomicrobiology. Examples are given from studies determining cell wall composition, acid–base properties, cell surface charge, metal adsorption onto bacterial cells, and bacterial surface–induced precipitation of secondary minerals. As XPS is an ultrahigh-vacuum technique, several sample preparation methods have been applied to enable analysis of bacterial samples, including analysis of freeze-dried samples as well as frozen bacterial suspensions. These are described and discussed alongside advantages and disadvantages of different approaches, with a special focus on fast-freezing and the cryogenic technique.

  • 89.
    Ramstedt, Madeleine
    et al.
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Kemi.
    Norgren, Caroline
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Kemi.
    Shchukarev, Andrei
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Kemi.
    Sjöberg, Staffan
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Kemi.
    Persson, Per
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Kemi.
    Co-adsorption of cadmium(II) and glyphosate at the water–manganite (γ-MnOOH) interface2005Inngår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 285, nr 2, s. 493-501Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The co-adsorption of Cd(II) and glyphosate (N-(phosphonomethyl)glycine, PMG) at the manganite (γ-MnOOH) surface has been studied in the pH range 6–10 at 25 °C and with 0.1 M Na(Cl) as ionic medium. Batch adsorption experiments, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and extended X-ray absorption fine structure (EXAFS) spectroscopy were used for the quantitative analysis and the determination of the molecular structure of the surface complexes. The adsorption of Cd(II) and PMG in the ternary Cd(II)–PMG–manganite system was compared with the adsorption in the binary Cd(II)–manganite and PMG–manganite systems. The formation of three inner sphere surface complexes was observed, a ternary Cd(II)–PMG–manganite complex, a binary Cd(II)–manganite complex and a binary PMG–manganite complex. The surface concentration of the ternary complex and the Cd(II)–manganite complex was more or less constant throughout the pH range studied. However, the surface concentration of the binary PMG–manganite complex decreased with increasing pH. The major part of the binary PMG–surface complex was protonated. The ternary surface complex displayed a type B structure (Cd(II)–PMG–manganite). The average Cd–Mn distance obtained from EXAFS (3.26 Å) indicates that the binary and ternary Cd(II)–surface complexes are formed by edge-sharing of Mn and Cd octahedra on the (010) plane of the manganite crystals.

  • 90.
    Ramstedt, Madeleine
    et al.
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Kemi.
    Norgren, Caroline
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Kemi.
    Sheals, Julia
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Kemi.
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Kemi.
    Sjöberg, Staffan
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Kemi.
    Chemical speciation of N-(phosphonomethyl)glycine in solution and at mineral interfaces2004Inngår i: Surface and Interface Analysis, ISSN 0142-2421, Vol. 36, nr 8, s. 1074-7Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The chemical speciation of the zwitterionic compound N-(phosphonomethyl)glycine (PMG) was studied in solution and at the mineral/water interface at different pH. Results from vacuum techniques such as XPS were compared with previously published conventional batch experiments. It was shown that by keeping the samples frozen during XPS analyses it was possible to keep a water interface. The frozen interface enables studies of the protonation of the nitrogen group which has previously been difficult using XPS. The protonation in frozen solutions was compared with literature data and the differences discussed. Furthermore, the speciation of PMG at the surface of manganite (-MnOOH) and goethite (-FeOOH) was studied. It was found that at least one of the protonation constants for surface-bound PMG differs significantly from the protonation constants in a pure PMG solution. The formation of different surface complexes is discussed together with differences between the sorption capacities of PMG onto the minerals studied.

  • 91.
    Ramstedt, Madeleine
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Analysis of bacterial cell surface chemical composition using cryogenic X-ray photoelectron spectroscopy2016Inngår i: Bacterial cell wall homeostasis: methods and protocols / [ed] Hee-Jeon Hong, New York, NY: Humana Press, 2016, s. 215-223Kapittel i bok, del av antologi (Annet vitenskapelig)
    Abstract [en]

    This chapter describes a method for measuring the average surface chemical composition with respect to lipids, polysaccharides, and peptides (protein + peptidoglycan) for the outer part of the bacterial cell wall. Bacterial cultures grown over night are washed with a buffer or saline at controlled pH. The analysis is done on fast-frozen bacterial cell pellets obtained after centrifugation, and the analysis requires access to X-ray photoelectron spectroscopy instrumentation that can perform analyses at cryogenic temperatures (for example using liquid nitrogen). The method can be used to monitor changes in the cell wall composition following environmental stimuli or genetic mutations. The data obtained originate from the outermost part of the cell wall. Thus, it is expected that for gram-negative bacteria only the outer membrane and part of the periplasmic peptidoglycan layer is probed during analysis, and for gram-positive bacteria only the top nanometers of the peptidoglycan layer of the cell wall is monitored.

  • 92.
    Ramstedt, Madeleine
    et al.
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Kemi.
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Kemi.
    Sjöberg, Staffan
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Kemi.
    Characterization of hydrous manganite (-MnOOH) surfaces - an XPS study2002Inngår i: Surface and Interface Analysis, Vol. 34, nr 1, s. 632-6Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Crystalline manganite (-MnOOH) has been synthesized and characterized using x-ray diffraction and high-resolution transmission electron microscopy techniques. The surface composition was studied with XPS between pH 0.4 and 11. Special pre-cooling procedures were developed to keep the manganite/water interface intact before and during XPS measurements. The O/OH group ratio differs between pH 6 and 11, in agreement with the acid/base characteristics of the surface. Below pH 6, on the other hand, drastic changes can be seen in the O 1s spectra due to dissolution of manganite. Possibly the interaction of OH groups with H+ in acidic suspensions is a first step leading to dissolution. The surface charge arising at high and low pH is compensated by the counter-ions Na+ and Cl-, respectively. The XPS spectra are presented and discussed in terms of the mechanisms for surface complexation and dissolution processes.

  • 93. Riittonen, Toni
    et al.
    Eränen, Kari
    Mäki-Arvela, Päivi
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Rautio, Anne-Riikka
    Kordas, Krisztian
    Kumar, Narendra
    Salmi, Tapio
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Åbo Akademi University, Process Chemistry Centre, Laboratory of Industrial Chemistry & Reaction Engineering, Turku/Åbo, Finland.
    Continuous liquid-phase valorization of bio-ethanol towards bio-butanol over metal modified alumina2015Inngår i: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 74, s. 369-378Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Commercial mixed-phase aluminum oxide was used as a heterogeneous catalyst support, providing slightly basic properties which are well-suited for the condensation of bio-ethanol to C-4 hydrocarbons, such as 1-butanol. Different metals (Cu, Ni and Co), at various metal loadings were deposited on the support. Consequently, the catalytic reactions were carried out in a continuous laboratory-scale fixed bed reactor operated at 240 degrees C and 70 bar. The catalysts were characterized by means of XRD, TEM, FT-IR, XPS and ICP-OES. Different metals were found to give entirely different product distributions. With the best catalysts, the selectivities towards 1-butanol close to 70% were reached, while the ethanol conversion typically varied between 10 and 30% - strongly depending on the metal applied. It was observed that low loading of copper and high loading of nickel were responsible for the formation of 1-butanol, whereas cobalt and high loading of copper resulted in the production of ethyl acetate. The reaction was found to be extremely sensitive to catalyst preparation conditions and procedures such as metal loading, calcination/reduction temperature and, thereby, to the formation of corresponding crystallite structure.

  • 94.
    Samikannu, Ajaikumar
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Golets, MikhailUmeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.Larsson, WilliamUmeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.Shchukarev, AndreyUmeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.Kordas, KrisztianUmeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Microelectronics and Materials Physics Laboratories, University of Oulu, FIN-90570 Oulu, Finland.Leino, Anne-RiikkaMicroelectronics and Materials Physics Laboratories, University of Oulu, FIN-90570 Oulu, Finland.Mikkola, Jyri-PekkaUmeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Åbo Akademi University, Åbo, Finland.
    Dehydroisomerization of α-pinene over metal supported Si-SBA-15 mesoporous molecular sieves2013Konferanseproceedings (Fagfellevurdert)
    Abstract [en]

    The effective dispersion of active metal species on mesoporous Si-SBA-15 is acquired by means of deposition-precipitation method.  In order to achieve this, the surface of Si-SBA-15 was first modified with TiO2 via grafting method, followed by deposition-precipitation method (DP) to obtain a fine dispersion of metallic nanoparticles over TiO2 modified Si-SBA-15. The structural features of the synthesized materials were characterized by means of X-ray diffraction (XRD), nitrogen sorption (BET), XPS and HR-TEM. A valuable platform chemical, p-cymene, was produced over the prepared catalyst by dehydroisomerization of α-pinene under vapour-phase conditions. A stable catalyst for one-spot synthesis of renewable p-cymene from α-pinene was developed.

  • 95.
    Samikannu, Ajaikumar
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Golets, Mikhail
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Larsson, William
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Kordas, Krisztian
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Microelectronics and Materials Physics Laboratories, University of Oulu, FIN-90570 Oulu, Finland.
    Leino, A-R
    Microelectronics and Materials Physics Laboratories, University of Oulu, FIN-90570 Oulu, Finland.
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Effective dispersion of Au and Au-M (M = Co, Ni, Cu and Zn) bimetallic nanoparticles over TiO2 grafted SBA-15: their catalytic activity on dehydroisomerization of α-pinene2013Inngår i: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 173, s. 99-111Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Mesostructured siliceous SBA-15 was synthesized via direct hydrothermal crystallization from acidic solution of poly-(ethylene glycol)-block-poly(propylene glycol)-block poly(ethylene glycol)-copolymer and tetraethyl orthosilicate. The amorphous surface of the calcined Si-SBA-15 was modified with 20wt.% of TiO2 by chemical grafting method using titanium isopropoxide as the titanium source in ethanol solution. Various metal nanoparticles Au, Au-M (M = Co, Ni, Cu and Zn) were supported on TiO2/SBA-15 by deposition-precipitation method (DP) using urea as the precipitating agent. The structural features of the synthesized materials were characterized by various physico-chemical techniques such as X-ray diffraction, nitrogen sorption, XPS and HR-TEM. BET results of Si-SBA-15 revealed the formation of mesoporous structure with an average pore size of 5.9nm, pore volume of 1.12 cm3/g and the specific surface area of 846 m2/g. HR-TEM results demonstrated that metal nanoparticles were highly dispersed over TiO2/SBA-15 and long range ordering of hexagonal mesopores of Si-SBA-15 was well retained after loading of 20 wt.% TiO2 and 3 wt.% of bimetallic nanoparticles. The catalytic performances of the prepared catalysts were studied on dehydroisomerization of α-pinene under gas phase conditions using hydrogen atmosphere. The stability and catalytic activity of Au-M-TiO2/SBA-15 (DP) catalysts upon conversion of α-pinene in to p-cymene was explored in comparison with the catalysts prepared by conventional method. AuNi-TiO2/SBA-15 catalysts prepared via DP method were found to be stable upon longer reaction time as well as superior in terms of conversion and selective towards the formation of p-cymene.

  • 96.
    Sandström, Robin
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Gracia-Espino, Eduardo
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Hu, Guangzhi
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. Key Laboratory of Chemistry of Plant Resources in Arid Regions, State Key Laboratory Basis of Xinjiang Indigenous Medicinal Plants Resource Utilization, Xinjiang Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Urumqi, China.
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Ma, Jingyuan
    Wågberg, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Yttria stabilized and surface activated platinum (PtxYOy) nanoparticles through rapid microwave assisted synthesis for oxygen reduction reaction2018Inngår i: Nano Energy, ISSN 2211-2855, E-ISSN 2211-3282, Vol. 46, s. 141-149Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The enhancement of platinum (Pt) based catalysts for the oxygen reduction reaction (ORR) by addition of rare earth metals represents a promising strategy to achieve high activity yet low content of the precious metal and concurrently addresses stability issues experienced by traditional late transition metal doping. Improvement in Pt utilization is essential for vehicular applications where material cost and abundancy is a great concern. Here we report a fast and efficient production route of yttria-stabilized platinum nanoparticles (PtxYOy) using a conventional household microwave oven. ORR performance showed a significant improvement and an optimum activity at a 3:1 Pt:Y ratio outperforming that of commercial Pt-Vulcan with a doubled specific activity. Incorporation of Y is evidenced by extended X-ray absorption fine structure and energy dispersive X-ray analysis, while significant amounts of integrated Y2O3 species are detected by X-ray photoelectron spectroscopy. Density functional theory calculations suggest surface migration and oxidation of Y, forming stable superficial yttrium oxide species with low negative enthalpies of formation. The robustness of PtxYOy is shown experimentally and through theoretical arguments demonstrating that surface yttria acts as a stabilizing agent and promoter of highly active ORR sites on the remaining Pt surface, surpassing even the Pt3Y alloy configuration.

  • 97. Sandström, Åke
    et al.
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Kemi.
    Paul, Jan
    XPS characterisation of chalcopyrite chemically and bio-leached at high and low redox potential2005Inngår i: Minerals Engineering, Vol. 18, nr 5, s. 505-15Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Leaching of chalcopyrite in sulphuric acid media has been investigated under constant redox potential conditions in solution. The leaching residues were analysed by X-ray diffraction and X-ray photoelectron spectroscopy. The leaching was performed at two different levels of redox potential, 420 mV and 600 mV (Pt vs. Ag, AgCl), at 65 °C. Both bioleaching and chemical leaching were investigated. The bioleaching was continuous, with a culture of the extremely thermophilic microorganism Sulfolobus metallicus. The high redox potential experiment was a “normal” bioleaching experiment; i.e., normal air flow, etc., the redox potential obtained at steady state was 600 mV and the low redox condition was achieved by a reduced airflow and additions of a sodium sulphite solution. The chemical leaching was done as a redox titration with potassium permanganate as oxidising agent to maintain the redox potential at 600 mV and 420 mV, respectively. Chalcopyrite leaching was greatly enhanced at the lower redox potential for both types of leaching, but especially during chemical leaching, which also resulted in large amounts of elemental sulphur. Passivation of the leaching at high redox potential was followed by a concomitant precipitation of large amounts of jarosite. Bioleaching resulted in a more complete sulphur oxidation to sulphate, even at low redox potential. It is thus concluded that passivation during chalcopyrite leaching is caused by jarosite and not elemental sulphur.

  • 98.
    Sarkar, Anjana
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Gracia-Espino, Eduardo
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Wågberg, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Mohl, Melinda
    Rautio, Anne-Riikka
    Pitkänen, Olli
    Sharifi, Tiva
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Kordas, Krisztian
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Photocatalytic reduction of CO2 with H2O over modified TiO2 nanofibers: Understanding the reduction pathway2016Inngår i: Nano Reseach, ISSN 1998-0124, E-ISSN 1998-0000, s. 1-13Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Nanosized metal (Pt or Pd)-decorated TiO2 nanofibers (NFs) were synthesized by a wet impregnation method. CdSe quantum dots (QDs) were then anchored onto the metal-decorated TiO2 NFs. The photocatalytic performance of these catalysts was tested for activation and reduction of CO2 under UV-B light. Gas chromatographic analysis indicated the formation of methanol, formic acid, and methyl formate as the primary products. In the absence of CdSe QDs, Pd-decorated TiO2 NFs were found to exhibit enhanced performance compared to Pt-decorated TiO2 NFs for methanol production. However, in the presence of CdSe, Pt-decorated TiO2 NFs exhibited higher selectivity for methanol, typically producing ∼90 ppmg−1·h−1 methanol. The CO2 photoreduction mechanism is proposed to take place via a hydrogenation pathway from first principles calculations, which complement the experimental observations.

  • 99.
    Sarkar, Anjana
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Leino, Anne-Riikka
    Kordas, Krisztian
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Petrov, Pavel O
    Tuchina, Elena S
    Popov, Alexey P
    Darvin, Maxim E
    Meinke, Martina
    Lademann, Juergen
    Tuchin, Valery V
    Photocatalytic activity of TiO2 nanoparticles: effect of thermal annealing under various gaseous atmospheres2012Inngår i: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 23, nr 47, s. 475711-475719Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The structure, composition and photocatalytic activity of TiO2 nanoparticles annealed in various gas atmospheres (N2, NH3 and H2) were studied in this work. The effect of treatment on crystal structure, particle size, chemical composition and optical absorbance were assessed by means of x-ray diffraction, transmission electron microscopy, x-ray photoelectron spectroscopy and diffuse optical reflectance/transmittance measurements, respectively. Photocatalytic properties of the materials were evaluated by three different methods: degradation of methyl orange in water, killing of Staphylococcus aureus bacteria and photogeneration of radicals in the presence of 3-carboxy-2,2,5,5-tetramethyl pyrrolidine-1-oxyl (PCA) marker molecules. The results indicate that the correlation between pretreatment and the photocatalytic performance depends on the photocatalytic processes and cannot be generalized.

  • 100. Schmidt, Sabrina A.
    et al.
    Kumar, Narendra
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Eranen, Kari
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Murzin, Dmitry Yu.
    Salmi, Tapio
    Preparation and characterization of neat and ZnCl2 modified zeolites and alumina for methyl chloride synthesis2013Inngår i: Applied Catalysis A: General, ISSN 0926-860X, E-ISSN 1873-3875, Vol. 468, s. 120-134Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A range of zeolite and alumina based catalysts, neat and impregnated with ZnCl2, were screened for gas-phase methyl chloride synthesis from methanol and HCl. The catalysts were characterized with FTIR, TEM, XPS, N-2-physisorption, XRD and EDX to identify the relationship between the catalyst characteristics and their activity and selectivity in methyl chloride synthesis. The work was focused on catalyst performance and stability, acid properties of catalysts and the influence of zinc impregnation. Upon modification with ZnCl2, the number of strong and medium Bronsted acid sites (BAS) decreased, while the number of Lewis acid sites (LAS) increased. The zinc species detected on the catalyst surface is possibly similar to ZnOCl. The presence of ZnCl2 as surface species is not probable, as chlorine is partially removed from the catalyst during calcination at 400 degrees C. However, the binding energy determined by XPS suggests a Zn2+ surface species. Zn2+ containing particles were observed on zeolites by TEM, which show a dependence of the particle size on the support acidity. The activities of the catalysts increased with the number of medium and strong LAS, whereas the methyl chloride selectivity slightly decreased giving dimethyl ether as a by-product. As the increase of acid sites upon modification with the same amounts of ZnCl2 was most pronounced for zeolite catalysts, they exhibited the highest activity. However, the zeolite catalysts showed deactivation with time on stream. Zn/H-ZSM 5 zeolite catalysts exhibited a higher stability in the synthesis of methyl chloride than ZnCl2 modified H-Beta and could be regenerated by burning the coke in air at 400 degrees C. Neat alumina and ZnCl2 modified alumina catalysts were active and selective at 300 degrees C and higher temperatures, but zeolite catalysts might be suitable for methyl chloride synthesis at lower temperatures, i.e. 200 degrees C.

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