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  • 1.
    Ajaikumar, Samikannu
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Ahlkvist, Johan
    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, K
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Laboratory of Industrial Chemistry and Reaction Engineering, Process Chemistry Centre, Åbo Akademi University, Piispankatu 8, FIN-20500, Turku/Åbo, Finland.
    Oxidation of α-pinene over gold containing bimetallic nanoparticles supported on reducible TiO2 by DPU method2011Ingår i: Applied Catalysis A: General, ISSN 0926-860X, E-ISSN 1873-3875, Vol. 392, nr 1-2, s. 11-18Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A series of bimetallic catalysts Au–M (where M = Cu, Co and Ru) were supported on a reducible TiO2 oxide via deposition-precipitation (DP) method with a slow decomposition of urea as the precipitating agent. The characteristic structural features of the prepared materials were characterized by various physico-chemical techniques such as X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). XPS results indicated the formation of alloyed bimetallic particles on the TiO2 support. TEM results confirmed the fine dispersion of metal nanoparticles on the support with an average particle size in the range of 3–5 nm. An industrially important process, oxy-functionalization of α-pinene was carried out over the prepared bimetallic heterogeneous catalysts under liquid phase conditions. Reaction parameters such as the reaction time, temperature, and the effect of solvent were studied for optimal conversion of α-pinene into verbenone. The major products obtained were verbenone, verbenol, α-pinene oxide and alkyl-pinene peroxide. The activity of the catalysts followed the order; AuCu/TiO2 > AuCo/TiO2 > Cu/TiO2 > Au/TiO2 > AuRu/TiO2. Upon comparison of the various catalysts, AuCu/TiO2 was found to be an active and selective catalyst towards the formation of verbenone. The temperature, nature of the catalysts and the choice of solvents greatly influenced the reaction rate.

  • 2.
    Annamalai, Alagappan
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Sandström, Robin
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Gracia-Espino, Eduardo
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Boulanger, Nicolas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Boily, Jean-Francois
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Mühlbacher, Inge
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Wågberg, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Influence of Sb5+ as a Double Donor on Hematite (Fe3+) Photoanodes for Surface-Enhanced Photoelectrochemical Water Oxidation2018Ingår i: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 10, nr 19, s. 16467-16473Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    To exploit the full potential of hematite (α-Fe2O3) as an efficient photoanode for water oxidation, the redox processes occurring at the Fe2O3/electrolyte interface need to be studied in greater detail. Ex situ doping is an excellent technique to introduce dopants onto the photoanode surface and to modify the photoanode/electrolyte interface. In this context, we selected antimony (Sb5+) as the ex situ dopant because it is an effective electron donor and reduces recombination effects and concurrently utilize the possibility to tuning the surface charge and wettability. In the presence of Sb5+ states in Sb-doped Fe2O3 photoanodes, as confirmed by X-ray photoelectron spectroscopy, we observed a 10-fold increase in carrier concentration (1.1 × 1020 vs 1.3 × 1019 cm–3) and decreased photoanode/electrolyte charge transfer resistance (∼990 vs ∼3700 Ω). Furthermore, a broad range of surface characterization techniques such as Fourier-transform infrared spectroscopy, ζ-potential, and contact angle measurements reveal that changes in the surface hydroxyl groups following the ex situ doping also have an effect on the water splitting capability. Theoretical calculations suggest that Sb5+ can activate multiple Fe3+ ions simultaneously, in addition to increasing the surface charge and enhancing the electron/hole transport properties. To a greater extent, the Sb5+- surface-doped determines the interfacial properties of electrochemical charge transfer, leading to an efficient water oxidation mechanism.

  • 3. Artemenko, A.
    et al.
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Štenclová, P.
    Wågberg, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Segervald, Jonas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Jia, X.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Kromka, A.
    Reference XPS spectra of amino acids2021Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this report we present XPS data for five amino acids (AAs) (tryptophan, methionine, glutamine, glutamic acid, and arginine) with different side chain groups measured in solid state (powder form). The theoretically and experimentally obtained chemical structure of AAs are compared. Here, we analyse and discuss C 1 s, N 1 s, O 1s and S 2p core level binding energies, FWHMs, atomic concentrations of the functional groups in AAs. The experimentally obtained and theoretically calculated ratio of atomic concentrations are compared. The zwitterionic nature of methionine and glutamine in solid state was determined from protonated amino groups in N 1s peak and deprotonated carboxylic groups in the C 1s spectrum. The obtained XPS results for AAs well correspond with previously reported data.

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  • 4. Asres, Georgies Alene
    et al.
    Baldoví, José J.
    Dombovari, Aron
    Järvinen, Topias
    Lorite, Gabriela Simone
    Mohl, Melinda
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Pérez Paz, Alejandro
    Xian, Lede
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Industrial Chemistry & Reaction Engineering, Department of Chemical Engineering, Johan Gadolin Process Chemistry Centre, Åbo Akademi University, Åbo-Turku, Finland.
    Spetz, Anita Lloyd
    Jantunen, Heli
    Rubio, Ángel
    Kordás, Krisztian
    Ultrasensitive H2S gas sensors based on p-type WS2 hybrid materials2018Ingår i: Nano Reseach, ISSN 1998-0124, E-ISSN 1998-0000, Vol. 11, nr 8, s. 4215-4224Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Owing to their higher intrinsic electrical conductivity and chemical stability with respect to their oxide counterparts, nanostructured metal sulfides are expected to revive materials for resistive chemical sensor applications. Herein, we explore the gas sensing behavior of WS2 nanowire-nanoflake hybrid materials and demonstrate their excellent sensitivity (0.043 ppm-1) as well as high selectivity towards H2S relative to CO, NH3, H2, and NO (with corresponding sensitivities of 0.002, 0.0074, 0.0002, and 0.0046 ppm-1, respectively). Gas response measurements, complemented with the results of X-ray photoelectron spectroscopy analysis and first-principles calculations based on density functional theory, suggest that the intrinsic electronic properties of pristine WS2 alone are not sufficient to explain the observed high sensitivity towards H2S. A major role in this behavior is also played by O doping in the S sites of the WS2 lattice. The results of the present study open up new avenues for the use of transition metal disulfide nanomaterials as effective alternatives to metal oxides in future applications for industrial process control, security, and health and environmental safety.

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  • 5. Aulin, Christian
    et al.
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Lindqvist, Josefina
    Malmström, Eva
    Wågberg, Lars
    Lindström, Tom
    Wetting kinetics of oil mixtures on fluorinated model cellulose surfaces2008Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 317, nr 2, s. 556-67Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The wetting of two different model cellulose surfaces has been studied; a regenerated cellulose (RG) surface prepared by spin-coating, and a novel multilayer film of poly(ethyleneimine) and a carboxymethylated microfibrillated cellulose (MFC). The cellulose films were characterized in detail using atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). AFM indicates smooth and continuous films on a nanometer scale and the RMS roughness of the RG cellulose and MFC surfaces was determined to be 3 and 6 nm, respectively. The cellulose films were modified by coating with various amounts of an anionic fluorosurfactant, perfluorooctadecanoic acid, or covalently modified with pentadecafluorooctanyl chloride. The fluorinated cellulose films were used to follow the spreading mechanisms of three different oil mixtures. The viscosity and surface tension of the oils were found to be essential parameters governing the spreading kinetics on these surfaces. XPS and dispersive surface energy measurements were made on the cellulose films coated with perfluorooctadecanoic acid. A strong correlation was found between the surface concentration of fluorine, the dispersive surface energy and the contact angle of castor oil on the surface. A dispersive surface energy less than 18 mN/m was required in order for the cellulose surface to be non-wetting (θe>90°) by castor oil.

    Graphical abstract

    AFM tapping mode image of a bilayer of PEI/MFC on silica in the height mode. The scanned surface area was 1 μm2 (left) and dispersive surface energy of fluorinated regenerated cellulose surfaces vs atomic fluorine concentration (right).

  • 6. Barišić, Antun
    et al.
    Lützenkirchen, Johannes
    Bebić, Nikol
    Li, Qinzhi
    Hanna, Khalil
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Begović, Tajana
    Experimental Data Contributing to the Elusive Surface Charge of Inert Materials in Contact with Aqueous Media2021Ingår i: Colloids and interfaces, E-ISSN 2504-5377, Vol. 5, nr 1, artikel-id 6Artikel i tidskrift (Övrigt vetenskapligt)
    Abstract [en]

    We studied the charging of inert surfaces (polytetrafluoroethylene, i.e., PTFE; graphite; graphene; and hydrophobic silica) using classical colloid chemistry approaches. Potentiometric titrations showed that these surfaces acquired less charge from proton-related reactions than oxide minerals. The data from batch-type titrations for PTFE powder did not show an effect of ionic strength, which was also in contrast with results for classical colloids. In agreement with classical colloids, the electrokinetic results for inert surfaces showed the typical salt level dependence. In some cases, the point of zero net proton charge as determined from mass and tentatively from acid–base titration differed from isoelectric points, which has also been previously observed, for example by Chibowski and co-workers for ice electrolyte interfaces. Finally, we found no evidence for surface contaminations of our PTFE particles before and after immersion in aqueous solutions. Only in the presence of NaCl-containing solutions did cryo-XPS detect oxygen from water. We believe that our low isoelectric points for PTFE were not due to impurities. Moreover, the measured buffering at pH 3 could not be explained by sub-micromolar concentrations of contaminants. The most comprehensive explanation for the various sets of data is that hydroxide ion accumulation occurred at the interfaces between inert surfaces and aqueous solutions.

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  • 7. Behravesh, Erfan
    et al.
    Kumar, Narendra
    Balme, Quentin
    Roine, Jorma
    Salonen, Jarno
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Process Chemistry Centre, Åbo Akademi University, FI-20500 Turku/Åbo, Finland.
    Peurla, Markus
    Aho, Atte
    Eränen, Kari
    Murzin, Dmitry Yu.
    Salmi, Tapio
    Synthesis and characterization of Au nano particles supported catalysts for partial oxidation of ethanol: Influence of solution pH, Au nanoparticle size, support structure and acidity2017Ingår i: Journal of Catalysis, ISSN 0021-9517, E-ISSN 1090-2694, Vol. 353, s. 223-238Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Partial oxidation of ethanol to acetaldehyde was carried out over gold catalysts supported on various oxides and zeolites by deposition precipitation. The special focus of this work was on the influence of H-Y zeolite surface charge on Au cluster size and loading linking it to activity and selectivity in ethanol oxidation and comparing with other studied catalysts. The catalysts were characterized by nitrogen physisorption, transmission electron microscopy (TEM), scanning electron microscopy/energy dispersive X-ray analysis (SEM/EDXA), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR) and zeta potential measurements. pH of the solution governed the Au NPs size within the range of 5.8–13.2 nm with less negatively charged surfaces leading to formation of smaller clusters. Au loading on H-Y zeolite with silica to alumina ratio of 80 was increased by raising the pH. In fact, H-Y-12 and H-Beta-25 were selective towards diethyl ether while acetaldehyde was the prevalent product on less acidic H-Y-80. The results demonstrated strong dependency of the catalytic activity on the Au cluster size. Namely turn over frequency (TOF) decreased with an increase in metal size from 6.3 to 9.3 nm on H-Y-80. Selectivity towards acetaldehyde and ethyl acetate did not change significantly on H-Y-80 within 6.3–9.3 nm Au particle size range. On Al2O3 support, however, selectivity towards acetaldehyde increased considerably upon diminishing Au average particle size from 3.7 to 2.1 nm.

  • 8.
    Bengtsson, Åsa
    et al.
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Kemi.
    Persson, Per
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Kemi.
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Kemi.
    Boström, Dan
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Kemi.
    Lövgren, Lars
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Kemi.
    A kinetic and spectroscopic study of fluorapatite dissolution2004Konferensbidrag (Övrigt vetenskapligt)
  • 9.
    Bengtsson, Åsa
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Persson, Per
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Sjöberg, Staffan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Phase Transformations, Ion-Exchange, Adsorption, and Dissolution Processes in Aquatic Fluorapatite Systems2009Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 25, nr 4, s. 2355-2362Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A synthetic fluorapatite was prepared that undergoes a phase transformation generated during a dialysis step. A surface layer with the composition Ca9(HPO4)2(PO4)4F2 is formed, which is suggested to form as one calcium atom is replaced by two protons. A surface complexation model, based upon XPS measurements, potentiometric titration data, batch experiments, and zeta-potential measurements was presented. The CaOH and OPO3H2 sites were assumed to have similar protolytic properties as in a corresponding nonstoichiometric HAP (Ca8.4(HPO4)1.6(PO4)4.4(OH)0.4) system. Besides a determination of the solubility product of Ca9(HPO4)2(PO4)4F2, two additional surface complexation reactions were introduced; one that accounts for a F/OH ion exchange reaction, resulting in the release of quite high fluoride concentrations (∼1 mM) that turned out to be dependent on the surface area of the particles. Furthermore, to explain the lowering of pHiep from around 8 in nonstoichiometric HAP suspensions to about 5.7 in FAP suspensions, a reaction that lowers the surface charge due to the readsorption of fluoride ions to the positively charged Ca sites was introduced: ≡CaOH2+ + F− ⇋ ≡CaF + H2O. The resulting model also agrees with predictions based upon XPS and ATR-FTIR observations claiming the formation of CaF2(s) in the most acidic pH range.

  • 10.
    Bengtsson, Åsa
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Persson, Per
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Sjöberg, Staffan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    A solubility and surface complexation study of a non-stoichiometric hydroxyapatite2009Ingår i: Geochimica et Cosmochimica Acta, ISSN 0016-7037, E-ISSN 1872-9533, Vol. 73, nr 2, s. 257-267Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The dissolution and surface complexation of a non-stoichiometric hydroxyapatite (Ca8.4(HPO4)1.6(PO4)4.4(OH)0.4), (HAP) was studied in the pH range 3.5 – 10.5, at 25 ºC in 0.1 M Na(Cl). The results from well-equilibrated batch experiments, potentiometric titrations, and zeta-potential measurements were combined with information provided by Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) spectroscopy and X-ray Photoelectron Spectroscopy (XPS). The information from the analyses was used to design an equilibration model that takes in to account dissolution, surface potential, solution and surface complexation, as well as possible phase transformations. The results from the XPS measurements clearly show that the surface of the mineral has a different composition than the bulk and that the Ca/P ratio of the surface layer is 1.4 ± 0.1. This ratio was also found in solution in the batches equilibrated at low pH where the dominating reaction is dissolution. In the batches equilibrated at near neutral pH values, however, the Ca/P ratio in solution attains values as high as 25, which is due to re-adsorption of phosphate ions to the HAP surface. The total concentration of protons as well as the total concentration of dissolved calcium and phosphate in solution were used to calculate a model for the dissolution and surface complexation of HAP. The constant capacitance model was applied in designing the following surface complexation model.

  • 11.
    Biasi, P.
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Åbo Akad Univ, Dept Chem Engn, Lab Ind Chem & React Engn, Johan Gadolin Proc Chem Ctr PCC, Biskopsgatan 8, FI-20500 Turku, Finland.
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Åbo Akad Univ, Dept Chem Engn, Lab Ind Chem & React Engn, Johan Gadolin Proc Chem Ctr PCC, Biskopsgatan 8, FI-20500 Turku, Finland.
    Sterchele, S.
    Salmi, T.
    Gemo, N.
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Centomo, P.
    Zecca, M.
    Canu, P.
    Rautio, A. -R
    Kordàs, K.
    Revealing the role of bromide in the H2O2 direct synthesis with the catalyst wet pretreatment method (CWPM)2017Ingår i: AIChE Journal, ISSN 0001-1541, E-ISSN 1547-5905, Vol. 63, nr 1, s. 32-42Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A tailor-made Pd0/K2621 catalyst was subjected to post synthesis modification via a wet treatment procedure. The aimwas the understanding of the role of promoters and how—if any—improvements could be qualitatively related to the cat-alyst performance for the H2O2direct synthesis. The Catalyst Wet Pretreatment Method was applied in different metha-nolic solutions containing H2O2, NaBr, and H3PO4, either as single modifiers or as a mixture. The catalyst wascharacterized by Transmission Electron Microscopy and X-ray Photoelectron Spectroscopy. It was concluded that themodified catalysts give rise to higher selectivities compared to the pristi ne reference catalyst thus opening a possibilityto exclude the addit ion of the undesirable selectivity enhancers in the reaction medium. This work provides original evi-dence on the role of promoter s, especially bromide, allowing the formulation of a new reaction mechanism for one ofthe most challenging reactions recognized by the world.

  • 12.
    Boily, Jean-Francois
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    X-ray photoelectron spectroscopy of fast-frozen hematite colloids in aqueous solutions. 2. tracing the relationship between surface charge and electrolyte adsorption2010Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 114, nr 6, s. 2613-2616Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Colloidal-sized hematite spheroids exposed to aqueous NaCl solutions were investigated by X-ray photoelectron spectroscopy using the fast-frozen technique. The O 1s region provided evidence for (de)protonation reactions of surface (hydr)oxo groups of OH-enriched/O-depleted hematite Surfaces. These results were also correlated to changes in sodium (Na 1s) and chloride (Cl 2p) contents with pH. Electrolyte ion surface loadings were successfully predicted using a classic thermodynamic adsorption model normalized for surface site density. These efforts pointed to ion-specific inner-Helmholtz plane capacitances.

  • 13. Borah, Raju Kumar
    et al.
    Raul, Prasanta Kumar
    Mahanta, Abhijit
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Industrial Chemistry & Reaction Engineering, Åbo Akademi University, Åbo-Turku, Finland.
    Thakur, Ashim Jyoti
    Copper Oxide Nanoparticles as a Mild and Efficient Catalyst for N-Arylation of Imidazole and Aniline with Boronic Acids at Room Temperature2017Ingår i: Synlett: Accounts and Rapid Communications in Synthetic Organic Chemistry, ISSN 0936-5214, E-ISSN 1437-2096, Vol. 28, nr 10, s. 1177-1182Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The present work describes the excellent catalytic activity of copper(II) oxide nanoparticles (NPs) towards N-arylation of aniline and imidazole at room temperature. The copper(II) oxide NPs were synthesized by a thermal refluxing technique and characterized by FT-IR spectroscopy; powder XRD, SEM, EDX, TEM, TGA, XPS, BET surface area analysis, and particle size analysis. The size of the NPs was found to be around 12 nm having a surface area of 164.180 m(2) g(-1). The catalytic system was also found to be recyclable and could be reused in subsequent catalytic runs without a significant loss of activity.

  • 14.
    Bottone, Anna
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Department of Ecology and Genetics, Uppsala University, Uppsala, Sweden.
    Boily, Jean-Francois
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Andersson, Patrik L.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Klaminder, Jonatan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Sodium hypochlorite as an oxidizing agent for removal of soil organic matter before microplastics analyses2021Ingår i: Journal of Environmental Quality, ISSN 0047-2425, E-ISSN 1537-2537, Vol. 51, nr 1, s. 112-122Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The omnipresence of microplastics (MPs) across Earth's surface has raised concerns about their environmental impact and created an urgent need for methods to identify them in complex soil and sedimentary matrices. However, detecting MPs in the O horizons of soils is difficult because plastic polymers share many physical and chemical properties with natural soil organic matter (SOM). In this study, we assessed whether sodium hypochlorite (NaOCl), a reagent that can oxidize SOM and simultaneously preserve mineral constituents, can be used for MP analysis and characterization in soil environments. In addition, we scrutinized how factors such as MP size, polymer type, extraction methods, and soil matrix affect the recovery of microplastic particles. We used both hydrophobic and density-dependent separation methods to assess the effects of our oxidation treatment on the recovery of MP. We observed that NaOCl effectively removed SOM without greatly altering the surface properties of resistant MP polymers (polypropylene, polylactic acid, low-density polyethylene, and polyethylene terephthalate), which were characterized using scanning electron microscopy and Fourier-transform infrared spectroscopy after SOM removal. The NaOCl treatment caused some chlorination and formation of additional C–OH bonds on polymer surfaces, which likely contributed to the reduced efficiency of the hydrophobic-based (oil) extraction. We conclude that NaOCl treatment can improve detection of MPs in SOM-rich soil and that recovery of MPs from soils is influenced by MP size, polymer type, extraction method, and soil type, which makes it challenging to develop a universal analytical method.

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  • 15.
    Bukhanko, Natalia
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Samikannu, Ajaikumar
    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.
    Leino, Anne-Riikka
    Microelectronics and Materials Physics Laboratories, University of Oulu, Finland.
    Kordas, Krisztian
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Microelectronics and Materials Physics Laboratories, University of Oulu, Finland.
    Wärnå, Johan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Laboratory of Industrial Chemistry and Reaction Engineering, Process Chemistry Centre, Åbo Akademi University, Finland.
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Laboratory of Industrial Chemistry and Reaction Engineering, Process Chemistry Centre, Åbo Akademi University, Finland.
    Continuous gas phase synthesis of 1-ethyl chloride from ethyl alcohol and hydrochloric acid over Al2O3-based catalysts: the ‘green’ route2013Ingår i: ACS Sustainable Chemistry and Engineering, E-ISSN 2168-0485, Vol. 1, nr 8, s. 883-893Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The synthesis of 1-ethyl chloride in the gas-phase mixture of ethanol and hydrochloric acid over ZnCl2/Al2O3 catalysts was studied in a continuous reactor using both commercial and tailor-made supports. The catalytic materials were characterized by the means of structural (XPS, TEM, XRD, and BET) and catalytic activity (selectivity and conversion) measurements. The reaction parameters such as temperature, pressure, and feedstock flow rates were optimized for the conversion of ethanol to ethyl chloride. The new tailor-made highly porous Al2O3-based catalyst outperformed its commercial counterpart by exhibiting high conversion and selectivity (98%) at the temperature of 325 °C. Long-term stability tests (240 h) confirmed the excellent durability of the tailor-made alumina catalysts. The process demonstrated here poses an efficient and economic “green” large-scale on-site synthesis of this industrially important reactant in industry, where bioethanol is produced and 1-ethyl chloride is necessary, e.g., for ethylation of cellulose and synthetic polymer products. On-site in situ production of ethyl chloride avoids the problems associated with the transportation and storage of toxic and flammable 1-ethyl chloride.

  • 16.
    Bukhanko, Natalia
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Department of Forest Biomaterials Technology, Swedish University of Agricultural Science, Umeå, Sweden.
    Schwarz, Christopher
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Samikannu, Ajaikumar
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Ngoc Pham, Tung
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Department of Chemistry, The University of Danang - University of Science and Technology, Nguyen Luong Bang, Lien Chieu, Da Nang, Viet Nam.
    Siljebo, William
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Wärnå, Johan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Rautio, Anne-Riikka
    Kordas, Krisztian
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Gas phase synthesis of isopropyl chloride from isopropanol and HCl over alumina and flexible 3-D carbon foam supported catalysts2017Ingår i: Applied Catalysis A: General, ISSN 0926-860X, E-ISSN 1873-3875, Vol. 542, nr 25, s. 212-225Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Isopropyl chloride synthesis from isopropanol and HCl in gas phase over ZnCl2 catalysts supported on Al2O3 as well as flexible carbon foam was studied in a continuous reactor. A series of catalytic materials were synthesised and characterised by BET, XPS, SEM, TEM, XRD and NH3-TPD methods. Catalytic activity tests (product selectivity and conversion of reactants) were performed for all materials and optimal reaction conditions (temperature and feedstock flow rates) were found. The results indicate that the highest yield of isopropyl chloride was obtained over 5 wt.% ZnCl2 on commercial Al2O3 (No. II) (95.3%). Determination of product mixture compositions and by-product identification were done using a GC-MS method. Carbon foam variant catalyst, 5 wt.% ZnCl2/C, was found to perform best out of the carbon-supported materials, achieving ∼75% yield of isopropyl chloride. The kinetic model describing the process in a continuous packed bed reactor was proposed and kinetic parameters were calculated. The activation energy for the formation of isopropyl chloride reaction directly from isopropanol and HCl was found to be ∼58 kJ/mol.

  • 17. Cano, A.
    et al.
    Lartundo-Rojas, L.
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Reguera, E.
    Contribution to the coordination chemistry of transition metal nitroprussides: a cryo-XPS study2019Ingår i: New Journal of Chemistry, ISSN 1144-0546, E-ISSN 1369-9261, Vol. 43, nr 12, s. 4835-4848Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The series of coordination polymers under investigation was formed by the assembly of a pentacyanonitrosylferrate(ii) anionic block, [Fe(CN)(5)NO](2-), through monovalent and divalent transition metal ions, e.g. Mn2+, Fe2+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+, Hg2+ and Ag+. For divalent ions, the resulting materials have a 3D porous framework with attractive features for applications in gas storage and separation, as electroactive solids, light-driven molecular magnets, and so on; in this study, we report the results obtained for a series of coordination polymers using the cryogenic X-ray photoelectron spectroscopy (cryo-XPS) data; comprehensive details regarding their coordination chemistries were obtained from the acquired spectra in addition to their comparison with the structural and spectroscopic information obtained from other techniques. The results discussed herein are original and contribute towards the understanding of the electronic structures and related properties for this family of coordination polymers. This series of solids was found to be highly susceptible to strong damage induced by X-ray beams throughout the conventional XPS experiment; therefore, the analysis was conducted under cryogenic conditions.

  • 18. Cano, A.
    et al.
    Rodríguez-Hernández, J.
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Reguera, E.
    Intercalation of pyrazine in layered copper nitroprusside: synthesis, crystal structure and XPS study2019Ingår i: Journal of Solid State Chemistry, ISSN 0022-4596, E-ISSN 1095-726X, Vol. 273, s. 1-10Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Hybrid inorganic–organic solids form an interesting family of functional materials, where their functionalities are determined by both, the inorganic and organic building blocks. This study reports the intercalation of pyrazine in 2D copper nitroprusside, the crystal structure of the resulting hybrid solid and explores the scope of cryogenic X-ray photoelectron spectroscopy (XPS) to shed light on its electronic structure. In this material, the pyrazine molecule appears coordinated to Cu atoms from neighboring layers, to form the columns in the resulting 3D porous framework. Its crystal structure was solved and refined from the corresponding XRD powder pattern. XPS data, recorded under cryogenic conditions, provided fine details on the electronic structure of this hybrid solid. The binding energy values for the ligand atoms and the involved metals show a definite correlation with the structural data and FT-IR spectra. When XPS spectra were recorded at room temperature, a significant sample decomposition was observed. Three possible mechanisms for the sample damage during the XPS experiment are considered. The hybrid material under study is representative of a wide series of nanoporous solids obtained by intercalation of organic pillars between 2D inorganic solids.

  • 19.
    Cant, David J. H.
    et al.
    National Physical Laboratory, Teddington, UK.
    Pei, Yiwen
    National Physical Laboratory, Teddington, UK.
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Ramstedt, Madeleine
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Marques, Sara S.
    Department of Chemical Sciences, Faculty of Pharmacy, University of Porto, Porto, Portugal.
    Segundo, Marcela A.
    Department of Chemical Sciences, Faculty of Pharmacy, University of Porto, Porto, Portugal.
    Parot, Jeremie
    Department of Biotechnology and Nanomedicine, SINTEF Industry, Trondheim, Norway.
    Molska, Alicja
    Department of Biotechnology and Nanomedicine, SINTEF Industry, Trondheim, Norway.
    Borgos, Sven E.
    Department of Biotechnology and Nanomedicine, SINTEF Industry, Trondheim, Norway.
    Shard, Alexander G.
    National Physical Laboratory, Teddington, UK.
    Minelli, Caterina
    National Physical Laboratory, Teddington, UK.
    Cryo-XPS for surface characterization of nanomedicines2023Ingår i: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 127, nr 39, s. 8220-8227Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Nanoparticles used for medical applications commonly possess coatings or surface functionalities intended to provide specific behavior in vivo, for example, the use of PEG to provide stealth properties. Direct, quantitative measurement of the surface chemistry and composition of such systems in a hydrated environment has thus far not been demonstrated, yet such measurements are of great importance for the development of nanomedicine systems. Here we demonstrate the first use of cryo-XPS for the measurement of two PEG-functionalized nanomedicines: a polymeric drug delivery system and a lipid nanoparticle mRNA carrier. The observed differences between cryo-XPS and standard XPS measurements indicate the potential of cryo-XPS for providing quantitative measurements of such nanoparticle systems in hydrated conditions.

  • 20. Cheng, Wei
    et al.
    Lindholm, Jerry
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Holmboe, Michael
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Luong, N. Tan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Ilton, Eugene S.
    Hanna, Khalil
    Boily, Jean-Francois
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Nanoscale hydration in layered manganese oxides2021Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 37, nr 2, s. 666-674Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Birnessite is a layered MnO2 mineral capable of intercalating nanometric water films in its bulk. With its variable distributions of Mn oxidation states (MnIV, MnIII, and MnII), cationic vacancies, and interlayer cationic populations, birnessite plays key roles in catalysis, energy storage solutions, and environmental (geo)chemistry. We here report the molecular controls driving the nanoscale intercalation of water in potassium-exchanged birnessite nanoparticles. From microgravimetry, vibrational spectroscopy, and X-ray diffraction, we find that birnessite intercalates no more than one monolayer of water per interlayer when exposed to water vapor at 25 °C, even near the dew point. Molecular dynamics showed that a single monolayer is an energetically favorable hydration state that consists of 1.33 water molecules per unit cell. This monolayer is stabilized by concerted potassium–water and direct water–birnessite interactions, and involves negligible water–water interactions. Using our composite adsorption–condensation–intercalation model, we predicted humidity-dependent water loadings in terms of water intercalated in the internal and adsorbed at external basal faces, the proportions of which vary with particle size. The model also accounts for additional populations condensed on and between particles. By describing the nanoscale hydration of birnessite, our work secures a path for understanding the water-driven catalytic chemistry that this important layered manganese oxide mineral can host in natural and technological settings.

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  • 21. Chernyshova, I V
    et al.
    Hanumantha Rao, K
    Vidyadhar, A
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Kemi.
    Mechanism of Adsorption of Long-Chain Alkylamines on Silicates. A Spectroscopic Study. 1. Quartz2000Ingår i: Langmuir, Vol. 16, nr 21, s. 8071-84Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The mechanism of adsorption of long-chain alkylamines at pH 6-7 onto quartz was studied using FTIR and XPS spectroscopy. The spectroscopic data were correlated with potential and Hallimond flotation results. For the first time it was shown that (1) amine cation in the first monolayer is H-bonded with surface silanol group and this H-bond becomes stronger after the break in the adsorption characteristics (isotherm, potential, floatability); (2) at the break the origin of the adsorbed amine species changes qualitatively, and along with alkylammonium ion attached to deprotonated silanol group, molecular amine appears at the surface and, as a result, monolayer thick patches of well-oriented and densely packed adsorbed amine species form rendering the surface highly hydrophobic; and (3) at higher amine concentration, bulk precipitation of molecular amine takes place. The counterion was found to influence both these steps. A model of successive two-dimensional and three-dimensional precipitation was suggested to explain amine adsorption on a silicate surface.

  • 22. Chernyshova, I V
    et al.
    Hanumantha Rao, K
    Vidyadhar, A
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Kemi.
    Mechanism of Adsorption of Long-Chain Alkylamines on Silicates: A Spectroscopic Study: 2. Albite2001Ingår i: Langmuir, Vol. 17, nr 3, s. 775-85Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Using FTIR (DRIFTS and IRRAS) and XPS spectroscopy, potential measurements, and Hallimond flotation tests, we confirmed that long-chain primary amines are adsorbed on silicates at pH 6-7 through the 2D-3D precipitation mechanism. The orientation and packing of dodecyl- and hexadecylammonium acetate and chloride adsorbed on albite in the different regions of the adsorption isotherm were determined. It was shown that these characteristics depend strongly on the substrate. Coadsorption of the counterion was not revealed, but the counterion was found to affect indirectly the adsorption at concentrations above the concentration of the bulk amine precipitation.

  • 23.
    Courtois, Julien
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Szumski, M
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Byström, Emil
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Iwasiewicz, Agnieszka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Irgum, Knut
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    A study of surface modification and anchoring techniques used in the preparation of monolithic microcolumns in fused silica capillaries.2006Ingår i: Journal of Separation Science, ISSN 1615-9306, E-ISSN 1615-9314, Vol. 29, nr 1, s. 14-24Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Based on a survey of the literature on pretreatment of fused silica capillaries, 3 etching procedures and 11 silanization protocols based on the vinylic silane 3-((trimethoxysilyl)propyl) methacrylate (gamma-MAPS) were found to be most representative as a means of ensuring attachment of in situ prepared vinylic polymers. These techniques were applied to fused silica capillaries and the success in establishing the intended surface modification was assessed. X-ray photoelectron spectroscopy (XPS) was used to characterize the chemical state of the surface, providing information regarding presence of the reagent bound to the capillary. Wetting angles were measured and correlated with the XPS results. An adherence test was done by photopolymerization of a 2 mm long plug of 1,6-butanediol dimethacrylate in the prepared capillaries and evaluation of its ability to withstand applied hydraulic pressure. SEM was also performed in cases where the plug was released or other irregularities were observed. Finally, the roughness of the etched surface, considered to be of importance, was assessed by atomic force microscopy. Alkaline etching at elevated temperature provided a surface roughness promoting adhesion. The commonly used silanization protocols involving water in the silanization or washing steps gave inadequate surface treatment. The best silanization procedure was based on toluene as a solvent.

  • 24. Das, Vijay Kumar
    et al.
    Bharali, Pranjal
    Konwar, Bolin Kumar
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Shchukarev, Andrey
    Industrial Chemistry & Reaction Engineering, Johan Gadolin Process Chemistry Centre, Åbo Akademi University.
    Thakur, Ashim Jyoti
    A convenient 'NOSE' approach used towards the synthesis of 6-amino-1,3-dimethyl-5-indolyl-1H-pyrimidine-2,4-dione derivatives catalyzed by nano-Ag2016Ingår i: New Journal of Chemistry, ISSN 1144-0546, E-ISSN 1369-9261, Vol. 40, nr 3, s. 1935-1939Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An endeavour has been made towards the synthesis of uracil based compounds in good to high yield catalyzed by nano-Ag at 70 [degree]C upon reacting 6-amino-1,3-dimethyluracil and indole derivatives. The catalyst was potentially recyclable from fresh up to the third run.

  • 25. Davidovich, P. B.
    et al.
    Fischer, A. I.
    Korchagin, D. V.
    Panchuk, V. V.
    Shchukarev, Andrey V.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Garabadzhiu, A. V.
    Belyaev, A. N.
    Synthesis, structure, biochemical, and docking studies of a new dinitrosyl iron complex [Fe-2(mu-SC4H3SCH2)(2)(NO)(4)]2015Ingår i: Journal of Molecular Structure, ISSN 0022-2860, E-ISSN 1872-8014, Vol. 1092, s. 137-142Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A new dinitrosyl iron complex of binuclear structure [Fe-2(mu-S-2-methylthiophene)(2)(NO)(4)] was first synthesized and structurally characterized by XRD and theoretical methods. Using caspase-3 as an example it was shown that [Fe-2(mu-S-2-methylthiophene)(2)(NO)(4)] and its analog [Fe-2(mu-S-2-methylfurane)(2)(NO)(4)] can inhibit the action of active site cysteine proteins; the difference in inhibitory activity was explained by molecular docking studies. Biochemical and in silico studies give grounds that the biological activity of dinitrosyl iron complexes is a mu-SR bridging ligand structure function. Thus the rational design strategy of [Fe-2(mu-SR)(2)(NO)(4)] complexes can be applied to make NO prodrugs with high affinity to therapeutically significant targets involved in cancer and inflammation.

  • 26.
    Davidovich, P. B.
    et al.
    Russia.
    Gurzhiy, V. V.
    Russia.
    Sabina, N. A.
    Russia.
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Garabadzhiu, A. V.
    Russia.
    Belyaev, A. N.
    Russia.
    Synthesis and structure of dinitrosyl iron complexes with secondary thiolate bridging ligands [Fe-2(mμ-SCHR2)(2)(NO)(4)], R = Me, Ph2015Ingår i: Polyhedron, ISSN 0277-5387, E-ISSN 1873-3719, Vol. 90, s. 197-201Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    New dinitrosyl iron complexes of binuclear structure [Fe-2(mu-SCHMe2)(2)(NO)(4)] and [Fe-2(mu-SCHPh2)(2)(NO)(4)] were first synthesized employing new method from Fe(CO)(5), corresponding thiol, and EtONO. Complexes structures were determined by XRD technique. DFT calculations were performed to probe the cis-conformer structures in gas and solution phases. NO donor ability of the complex with isopropyl thiolate ligand was studied.

  • 27.
    Dinh, Ngoc Phuoc
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Nguyen, Anh Mai
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Quach, Minh Cam
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Shchukarev, Andrei
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Irgum, Knut
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Functionalization of epoxy-based monoliths for ion exchange chromatography of proteins2009Ingår i: Journal of Separation Science, Vol. 32, nr 15-16, s. 2556-2564Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Macroporous epoxy-based monoliths prepared by emulsion polymerization have been modified for use in ion exchange chromatography (IEC) of proteins. Strong anion exchange functionality was established by iodomethane quaternization of tertiary amine present on the monolith surface as a part of the polymer backbone. The modification pathway to cation exchange materials was via incorporation of glycidyl methacrylate (GMA) brushes which were coated using atom transfer radical polymerization (ATRP). Strong (SO3-) and weak (COO-) cation exchange groups were thereafter introduced onto the GMA-grafted monoliths by reactions with sodium hydrogen sulfite and iminodiacetic acid, respectively. Grafting was confirmed by XPS, gravimetric measurement, and chromatographic behavior of the modified materials toward model proteins. In incubation experiments the proteins were recovered quantitatively with no obvious signs of unfolding after contact with the stationary phase for >2 h. Chromatographic assessments on the functionalized columns as well as problems associated with flow-through modification by ATRP are discussed.

  • 28. Domashevskaya, E. P.
    et al.
    Chuvenkova, O. A.
    Ryabtsev, S. V.
    Yurakov, Yu. A.
    Kashkarov, V. M.
    Shchukarev, Andrey V.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Turishchev, S. Yu.
    Electronic structure of undoped and doped SnOx nanolayers2013Ingår i: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 537, s. 137-144Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Results of electronic structure investigations for tin oxide nanolayers obtained by tin magnetron sputtering and their following oxidation in air at different temperatures are presented. Using X-ray photoelectron spectroscopy (XPS) and X-ray absorption near edge structure (XANES) spectroscopy techniques it was shown that at the 240 degrees C anneal a predominant phase in the sample surface layers is tin monoxide. With the annealing temperature increase up to 450 degrees C the phase composition corresponds to tin dioxide. Rather high sorption sensitivity for the samples oxidized at 450 degrees C was found. The compositional model of the gap structure based on XANES and XPS data matching for SnOx nanolayers revealed occurrence of the crossed transitions with the energy of similar to 3.7 eV in the presence of two phases: the SnO and the SnO2 or SnOx with vacancies. Under surface doping of SnO2 nanolayers with palladium PdO and PdO2 is observed where PdO is the most intensive component. O-2 and H-2 multiple alternate exposures resulted in the disappearance of palladium dioxide and PdO recovery to the metallic Pd. Under Pd bulk doping of nanolayers PdO and PdO2 were observed in the surface layers. In this case PdO2 was presented by two types of particles different in size, one of them having the greatest binding energy of Pd 3d(5/2) (339.0 eV). (C) 2013 Elsevier B.V. All rights reserved.

  • 29. Domashevskaya, EP
    et al.
    Ryabtsev, SV
    Turishchev, S Yu
    Kashkarov, VM
    Yurakov, Yu A
    Chuvenkova, OA
    Shchukarev, Andrey V
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    XPS and XANES studies of SnOx nanolayers2008Ingår i: Journal of Structural Chemistry, ISSN 0022-4766, E-ISSN 1573-8779, Vol. 49, nr Suppl 1, s. 80-91Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper presents the results of our XPS (X-ray photoelectron spectroscopy) and XANES (X-ray absorption near edge structure) Studies of tin oxide nanolayers obtained by magnetron spraying of the metal and its further oxidation in air at different temperatures. It was shown that at 240 degrees C (annealing temperature), tin monoxide was dominant in the surface layer of the samples. When the temperature was increased to 450 degrees C, the phase composition corresponded to tin dioxide. Increased sorption ability was found for the samples oxidized at 450 degrees C. The band structure model of SnOx nanolayers obtained by superposition of the XANES and XPS data revealed cross transitions with energy similar to 3.7 eV in the presence of the SnO and SnO, phases. Surface doping of nanolayers with palladium gave the Pd, PdO, and PdO2 components, among which PdO was most intense. Alternate treatments with O-2 and H-2 gases led to the disappearance of palladium dioxide and the reduction of PdO to the Pd metal. After the volume doping of nanoplayers with palladium, the surface layer contained PdO and PdO2; the latter was represented by two types of particles with different sizes.

  • 30.
    Ekspong, Joakim
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Sharifi, Tiva
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Klechikov, Alexey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Wågberg, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Gracia-Espino, Eduardo
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Stabilizing Active Edge Sites in Semicrystalline Molybdenum Sulfide by Anchorage on Nitrogen-Doped Carbon Nanotubes for Hydrogen Evolution Reaction2016Ingår i: Advanced Functional Materials, ISSN 1616-301X, E-ISSN 1616-3028, Vol. 26, nr 37, s. 6766-6776Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Finding an abundant and cost-effective electrocatalyst for the hydrogen evolu-tion reaction (HER) is crucial for a global production of hydrogen from water electrolysis. This work reports an exceptionally large surface area hybrid catalyst electrode comprising semicrystalline molybdenum sulfi de (MoS 2+ x) catalystattached on a substrate based on nitrogen-doped carbon nanotubes (N-CNTs), which are directly grown on carbon fiber paper (CP). It is shown here that nitrogen-doping of the carbon nanotubes improves the anchoring of MoS 2+ xcatalyst compared to undoped carbon nanotubes and concurrently stabilizes a semicrystalline structure of MoS 2+ x with a high exposure of active sites for HER. The well-connected constituents of the hybrid catalyst are shown to facilitate electron transport and as a result of the good attributes, the MoS 2+ x/N-CNT/CPelectrode exhibits an onset potential of −135 mV for HER in 0.5 M H2SO4, a Tafel slope of 36 mV dec −1, and high stability at a current density of −10 mA cm −2.

  • 31. Eriksson, Johan
    et al.
    Frankki, Sofia
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Kemi.
    Skyllberg, Ulf
    Binding of 2,4,6-Trinitrotoluene, Aniline, and Nitrobenzene to Dissolved and Particulate Soil Organic Matter2004Ingår i: Environmental Science & Technology, Vol. 38, nr 11, s. 3074-80Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The distribution of TNT* (the sum of TNT and its degradation products), aniline, and nitrobenzene between particulate organic matter (POM), dissolved soil organic matter (DOM), and free compound was studied in controlled kinetic (with and without irradiation) and equilibrium experiments with mixtures of POM and DOM reflecting natural situations in organic rich soils. The binding of TNT* to POM was fast, independent of irradiation, and adsorption isotherms had a great linear contribution (as determined by a mixed model), indicative of a hydrophobic partitioning mechanism. The binding of TNT* to DOM was slower, strongly enhanced under nonirradiated conditions, and adsorption isotherms were highly nonlinear, indicative of a specific interaction between TNT derivatives and functional groups of DOM. Nitrobenzene was associated to both POM and DOM via hydrophobic partitioning, whereas aniline binding was dominated by specific binding to POM and DOM functional groups. On the basis of nitrobenzene and TNT* adsorption parameters determined by a mixed Langmuir + linear model, POM had 2-3 times greater density of hydrophobic moieties as compared to DOM. This difference was reflected by a greater (O + N)/C atomic ratio for DOM. The sum of C-C and C-H moieties, as determined by X-ray photoelectron spectroscopy (XPS), and the sum of aryl-C and alkyl-C, as determined by solid-state cross-polarization magic-angle spinning (CP-MAS) 13C NMR, could only qualitatively account for differences in adsorption parameters. Aliphatic C was found to be more important for the hydrophobic partitioning than aromatic C. On the basis of nonlinear adsorption parameters, the density of functional groups reactive with aniline and TNT derivatives was 1.3-1.4 times greater in DOM than in POM, which was in fair agreement with 13C NMR and XPS data for the sum of carboxyl and carbonyl groups as potential sites for electrostatic and covalent bonding. We conclude that in contaminated soils characterized by continuous leaching of DOM, formation of TNT derivatives (via biotic and abiotic reductive degradation) and their preference for specific functional groups in DOM may contribute to a significant transportation of potentially toxic TNT compounds into surface waters and groundwaters.

  • 32. Fischer, A I
    et al.
    Kuznetsov, V A
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Belyaev, A N
    Crystal and molecular structures of mixedvalence octanuclear cobalt(II,III) propionate and butyrate with an etagerelike core2012Ingår i: Russian chemical bulletin, ISSN 1066-5285, E-ISSN 1573-9171, Vol. 61, nr 4, s. 821-827Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The new mixed-valence octanuclear cobalt carboxylate complexes [CoII4CoIII4(μ4-O)4-(μ3-OMe)4(μ-O2CR)6(O2CR)2(H2O)6]·4H2O, where R = Et (3) or n-Pr (4), were investigated by X-ray diffraction analysis. Complexes 3 and 4 have a molecular octanuclear structure, and they are valence trapped, and contain four cobalt atoms Co3+ in the central cubane fragment with four cobalt atoms Co2+ at the periphery of the molecules. The molecules of the complexes are stabilized by four intramolecular hydrogen bonds and are linked, together with water solvent molecules, by intermolecular hydrogen bonds to form a three-dimensional supramolecular system.

  • 33. Fisher, AI
    et al.
    Ruzanov, DO
    Panina, NS
    Belyaev, AN
    Simanova, SA
    Dolgushin, FM
    Shchukarev, Andrey V
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    The first example of cobalt(III) mu-oxoacetate with water molecules in apical positions2008Ingår i: Russian journal of general chemistry, ISSN 1070-3632, E-ISSN 1608-3350, Vol. 78, nr 11, s. 2006-2012Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Oxidation of Co(MeCOO)(2)center dot 4H(2)O with ozone in acetic acid followed by the treatment with nitric acid results in the formation of the trinuclear oxo-centered acetate complex [Co(III) (3)(mu(3)-O)(mu-O(2)CMe)(6)(OH(2))(3)] NO(3)center dot MeCOOH ([I]NO(3)center dot MeCOOH). Reasons of a decrease in the idealized symmetry of molecular structure (D (3h) -> D (3)) of the complex cation [I](+) were analyzed by means of quantum-chemical calculations. The complex does not retain its structure in solutions (in water, methanol, and ethanol).

  • 34. Frankki, Sofia
    et al.
    Persson, Ylva
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Kemi.
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Kemi.
    Tysklind, Mats
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Kemi.
    Partitioning of chloroaromatic compounds between the aqueous phase and dissolved and particulate soil organic matter at chlorophenol contaminated sites2007Ingår i: Environmental Pollution, Vol. 148, nr 1, s. 182-90Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The retention and mobility of hydrophobic organic contaminants (HOCs) in soil is mainly determined by hydrophobic partitioning to dissolved and particulate organic matter (DOM and POM, respectively). The aqueous phase, DOM, and POM fractions were extracted and separated from soils at three sites contaminated with technical chlorophenol formulations. Concentrations of chlorophenols (CP), polychlorinated phenoxyphenols (PCPP), polychlorinated diphenyl ethers (PCDE) and polychlorinated dibenzo-p-dioxins and furans (PCDD/F) were determined. The partitioning to POM, in relation to DOM, increased in all three soils with increasing hydrophobicity in the order CP < PCPP PCDE PCDF < PCDD. Differences in partitioning to DOM (log KDOC) and POM (log KPOC) could not be explained by differences in gross organic C chemistry. Black carbon did not contribute significantly to the sorption of PCDDs, whereas >70% wood fibre in one soil resulted in a decrease of log KPOC of 0.5 units for CPs and PCDDs. We conclude that log KOC for both DOM and POM need to be explicitly determined when the retention and mobility of HOCs is described and modelled in soils.

    Increasing hydrophobicity of organic compounds increases the partitioning to particulate natural organic matter relative to dissolved natural organic matter.

  • 35. Gemo, Nicola
    et al.
    Menegazzo, Federica
    Biasi, Pierdomenico
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Åbo Akademi University, Laboratory of Industrial Chemistry and Reaction Engineering, Process Chemistry Centre, Turku/Åbo, Finland .
    Sarkar, Anjana
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Samikannu, Ajaikumar
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Raut, Dilip G.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Kordás, Krisztián
    Rautio, Anne-Riikka
    Mohl, Melinda
    Boström, Dan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Åbo Akademi University, Laboratory of Industrial Chemistry and Reaction Engineering, Process Chemistry Centre, Turku/Åbo, Finland .
    TiO2 nanoparticles vs. TiO2 nanowires as support in hydrogen peroxide direct synthesis: the influence of N and Au doping2016Ingår i: RSC Advances, E-ISSN 2046-2069, Vol. 6, nr 105, s. 103311-103319Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The performance of Pd on titania support were evaluated in the direct synthesis of hydrogen peroxide. The equipment used was a high pressure, semi-batch apparatus equipped with a special injection system. Pd (1 wt%) catalysts on TiO2 materials with different nature were prepared by wet impregnation method. Three aspects were investigated: (a) the structure of the support (nanoparticles vs. nanowires); (b) the addition of a second active metal (Au); (c) the influence of N-doping of the support. All samples were characterized by means of XPS, TEM and XRD analyses. TiO2 nanoparticle supported catalyst demonstrated higher H2O2 selectivity and higher turnover frequency (TOF) than the catalysts based on TiO2 nanowires. The addition of Au to the Pd TiO2 nanowire catalyst improved the H2O2 selectivity due to altered particle size and electronic effects. Both N-doped versions of the catalysts gave rise to higher H2O2 selectivity than the parent non-doped ones. The synthetic procedure was the source of this observation: larger mean Pd nanoparticles were present, thus favouring the formation of H2O2 as the primary product.

  • 36. Gemo, Nicola
    et al.
    Sterchele, Stefano
    Biasi, Pierdomenico
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Department of Chemical Engineering, Åbo Akademi University, Biskopsgatan 8, Åbo-Turku, Finland .
    Centomo, Paolo
    Canu, Paolo
    Zecca, Marco
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Kordas, Krisztian
    Salmi, Tapio Olavi
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Department of Chemical Engineering, Åbo Akademi University, Biskopsgatan 8, Åbo-Turku, Finland .
    The influence of catalyst amount and Pd loading on the H2O2 synthesis from hydrogen and oxygen2015Ingår i: Catalysis Science & Technology, ISSN 2044-4753, E-ISSN 2044-4761, Vol. 5, nr 7, s. 3545-3555Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Palladium catalysts with an active metal content from 0.3 to 5.0 wt.% and supported on a strongly acidic, macroporous resin were prepared by ion-exchange/reduction method. H2O2 direct synthesis was carried out in the absence of promoters (acids and halides). The total Pd amount in the reacting environment was varied by changing A) the catalyst concentration in the slurry and B) the Pd content of the catalyst. In both cases, smaller amounts of the active metal enhance the selectivity towards H2O2, at any H-2 conversion, with option B) better than A). In case A), the Pd(II)/Pd(0) molar ratio (XPS) in the spent catalysts was found to decrease at lower catalyst Pd content. With these catalysts and this experimental set-up the dynamic H-2(1)/Pd molar ratio, the metal loading and the metal particle size were the key factors controlling the selectivity, which reached 57% at 60% H-2 conversion, and 80% at lower conversion.

  • 37.
    Gojkovic, Zivan
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Ramstedt, Madeleine
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Funk, Christiane
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Cryogenic X-ray photoelectron spectroscopy determines surface composition of algal cells and gives insights into their spontaneous sedimentation2020Ingår i: Algal Research, ISSN 2211-9264, Vol. 47, artikel-id 101836Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The flotation properties of two green microalgal species isolated from Northern Sweden, Chlorella vulgaris 13-1 and Coelastrella sp. 3-4, were investigated. C. vulgaris 13-1 is a flotating alga that remains suspended in solution during culturing, while Coelastrella sp. 3-4 is readily sedimenting in the stationary growth phase. We were the first to use cryogenic X-ray photoelectron spectroscopy (Cryo-XPS) to gain information on the chemical composition of the algal cell surface and added to these data results obtained from diffuse reflectance - Fourier Transform infrared spectroscopy (DR-FTIR) and classical chemical extractions of carbohydrates, lipids and proteins. Based on the Cryo-XPS data the surface of the sedimenting Coelastrella sp. 3-4 strain is rich in proteins and lipids, while the cell surface of non-flocculating C. vulgaris 13-1 is predominated by carbohydrates, but is poor in lipids. The Zeta-potential of both strains was equally negative. Cell size and the amount of carbohydrates on the algal cell surface, but not the negative surface charge, therefore indicate colloidal stability of microalgae in solutions and can be applied to predict flotation properties of green microalgae.

  • 38. Golyakov, A. M.
    et al.
    Shchukarev, Andrey V.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Ardasheva, L. P.
    Borisov, A. N.
    Electrochemical and spectral properties of the polymer form of Cu(II) complex with N,N '-bis(salicylidene)-1,3-propylenediamine2013Ingår i: Russian journal of general chemistry, ISSN 1070-3632, E-ISSN 1608-3350, Vol. 83, nr 3, s. 423-429Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A conductive polymer based on the Cu(II) complex with N,N'-bis(salicylidene)-1,3-propylenediamine was obtained electrochemically. The optimal mode of the synthesis of the polymer under potentiostatic conditions was found. We determined the charge diffusion coefficient and activation barrier and elucidated the nature of the limiting step of the charge transfer in the polymer bulk in the electrolyte medium. The azomethine base, Cu(II) complex, and its polymer form in the oxidized and reduced states were characterized by X-ray photoelectron spectroscopy and electron absorption spectroscopy.

  • 39. Golyakov, A M
    et al.
    Shchukarev, Andrey V
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Pak, V N
    Shagisultanova, G A
    Borisov, A N
    Electrochemical Synthesis and Spectroscopy of the Polymeric Form of N,N '-Bis(3-methoxysalicylidene)-1,3-propylenediamine2011Ingår i: Russian journal of applied chemistry, ISSN 1070-4272, E-ISSN 1608-3296, Vol. 84, nr 2, s. 317-324Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Electrochemical oxidation of N,N '-bis(3-methoxysalicylidene)-1,3-propylenediamine leads to the formation of a conducting polymer on the electrode surface. The diffusion coeffi cient and activation barrier of the charge transfer in the bulk of the polymer in an electrolyte medium were determined. The Schiff base and its polymeric form in the oxidized and reduced states were characterized by IR, X-ray photoelectron, and electronic absorption spectroscopy. Reversible changes in the polymer structure, accompanying its electrochemical oxidation–reduction, are substantiated.

  • 40.
    Gracia-Espino, Eduardo
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Hu, Guangzhi
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Wågberg, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Understanding the Interface of Six-Shell Cuboctahedral and Icosahedral Palladium Clusters on Reduced Graphene Oxide: Experimental and Theoretical Study2014Ingår i: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 136, nr 18, s. 6626-6633Artikel i tidskrift (Refereegranskat)