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  • 1. Acharya, Shravan S.
    et al.
    Easton, Christopher D.
    McCoy, Thomas M.
    Spiccia, Leone
    Ohlin, C. André
    Umeå University, Faculty of Science and Technology, Department of Chemistry. School of Chemistry, Monash University, Clayton, Australia.
    Winther-Jensen, Bjorn
    Diverse composites of metal-complexes and PEDOT facilitated by metal-free vapour phase polymerization2017In: Reactive & functional polymers, ISSN 1381-5148, E-ISSN 1873-166X, Vol. 116, p. 101-106Article in journal (Refereed)
    Abstract [en]

    Abstract Oxidative polymerization for the manufacture of conducting polymers such as poly(3,4-ethylenedioxy-thiophene) has traditionally employed iron(III) salts. Demonstrated in this study is vapour phase polymerization of 3,4-ethylenedio- xythiophene using a metal-free oxidant, ammonium persulfate, leading to films with an estimated conductivity of 75 S/cm. Additionally, a route for embedding active transition metal complexes into these poly(3,4-ethylenedioxythiophene)/-poly(styrene-4-sulfonate) (PEDOT/PSS) films via vapour assisted complexation is outlined. Here, the vapour pressure of solid ligands around their melting temperatures was exploited to ensure complexation to metal ions added into the oxidant mixture prior to polymerization of PEDOT. Four composite systems are discussed, viz. PEDOT/PSS embedded with tris(8-hydroxyquinolinato)cobalt(III), tris(2,2-bipyridine)cobalt(II), tris(1,10- phenanthroline)cobalt(II) and tris(8-hyd-roxyquinolinato)aluminium(III). Using these composites, electrochemical reduction of nitrite to ammonia with a faradaic efficiency of 61% was reported.

  • 2.
    Adranno, Brando
    et al.
    Physical Materials Chemistry, Department of Materials and Environmental Chemistry, Stockholm University, 10691 Stockholm, Sweden.
    Tang, Shi
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Paterlini, Veronica
    Physical Materials Chemistry, Department of Materials and Environmental Chemistry, Stockholm University, 10691 Stockholm, Sweden.
    Smetana, Volodymyr
    Physical Materials Chemistry, Department of Materials and Environmental Chemistry, Stockholm University, 10691 Stockholm, Sweden; Intelligent Advanced Materials (iAM), Department of Biological and Chemical Engineering and iNANO, Aarhus University, 8000 Aarhus C, Denmark.
    Renier, Olivier
    Physical Materials Chemistry, Department of Materials and Environmental Chemistry, Stockholm University, 10691 Stockholm, Sweden.
    Bousrez, Guillaume
    Physical Materials Chemistry, Department of Materials and Environmental Chemistry, Stockholm University, 10691 Stockholm, Sweden; Intelligent Advanced Materials (iAM), Department of Biological and Chemical Engineering and iNANO, Aarhus University, 8000 Aarhus C, Denmark.
    Edman, Ludvig
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Mudring, Anja-Verena
    Physical Materials Chemistry, Department of Materials and Environmental Chemistry, Stockholm University, 10691 Stockholm, Sweden; Intelligent Advanced Materials (iAM), Department of Biological and Chemical Engineering and iNANO, Aarhus University, 8000 Aarhus C, Denmark.
    Broadband white-light-emitting electrochemical cells2023In: Advanced Photonics Research, ISSN 2699-9293, Vol. 4, no 5, article id 2200351Article in journal (Refereed)
    Abstract [en]

    Emerging organic light-emitting devices, such as light-emitting electrochemical cells (LECs), offer a multitude of advantages but currently suffer from that most efficient phosphorescent emitters are based on expensive and rare metals. Herein, it is demonstrated that a rare metal-free salt, bis(benzyltriphenylphosphonium)tetrabromidomanganate(II) ([Ph3PBn]2[MnBr4]), can function as the phosphorescent emitter in an LEC, and that a careful device design results in the fact that such a rare metal-free phosphorescent LEC delivers broadband white emission with a high color rendering index (CRI) of 89. It is further shown that broadband emission is effectuated by an electric-field-driven structural transformation of the original green-light emitter structure into a red-emitting structure.

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  • 3.
    Aghbolagh, Mahdi Shahmohammadi
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Meynaq, Mohammad Yaser Khani
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Shimizu, Kenichi
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Lindholm-Sethson, Britta
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Aspects on mediated glucose oxidation at a supported cubic phase2017In: Bioelectrochemistry, ISSN 1567-5394, E-ISSN 1878-562X, Vol. 118, p. 8-13Article in journal (Refereed)
    Abstract [en]

    A supported liquid crystalline cubic phase housing glucose oxidase on an electrode surface has been suggested as bio-anode in a biofuel. The purpose of this investigation is to clarify some aspect on the mediated enzymatic oxidation of glucose in such a bio-anode where the mediator ferrocene-carboxylic acid and glucose were dissolved in the solution. The enzyme glucose oxidase was housed in the water channels of the mono-olein cubic phase. The system was investigated with cyclic voltammetry at different scan rates and the temperature was varied between 15 degrees C and 30 degrees C. The diffusion coefficient of the mediator and also the film resistance was estimated showing a large decrease in the mass-transport properties as the temperature was decreased. The current from mediated oxidation of glucose at the electrode surface increased with decreasing film thickness. The transport of the mediator in the cubic phase was the rate-limiting step in the overall reaction, where the oxidation of glucose took place at the outer surface of the cubic phase.

  • 4.
    Akhtar, Sohel
    et al.
    School of Chemical Sciences, Indian Association for the Cultivation of Science, Kolkata, West Bengal, India.
    Bala, Sukhen
    School of Chemical Sciences, Indian Association for the Cultivation of Science, Kolkata, West Bengal, India.
    De, Avik
    School of Chemical Sciences, Indian Association for the Cultivation of Science, Kolkata, West Bengal, India.
    Das, Krishna Sundar
    School of Chemical Sciences, Indian Association for the Cultivation of Science, Kolkata, West Bengal, India.
    Adhikary, Amit
    School of Chemical Sciences, Indian Association for the Cultivation of Science, Kolkata, West Bengal, India.
    Jyotsna, Shubhra
    Physical & Materials Chemistry Division, CSIR-National Chemical Laboratory, Pune, India.
    Poddar, Pankaj
    Physical & Materials Chemistry Division, CSIR-National Chemical Laboratory, Pune, India.
    Mondal, Raju
    School of Chemical Sciences, Indian Association for the Cultivation of Science, Kolkata, West Bengal, India.
    Designing Multifunctional MOFs Using the Inorganic Motif [Cu33-OH)(μ-Pyz)] as an SBU and Their Properties2018In: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 19, no 2, p. 992-1004Article in journal (Refereed)
    Abstract [en]

    In a continuation of our interest in pyrazole-based multifunctional metal–organic frameworks (MOFs), we report herein the construction of a series of Cu(II) MOFs using pyrazole and various 5-substituted isophthalic acids. The central theme is to generate MOFs using the crystal engineering strategy of spacer and node; however, for the node we have introduced a well-known inorganic motif, a [Cu3(μ3-OH)(μ-Pyz)3] unit. The appearance of the SBU in five MOFs confirms the robustness and reproducibility of the motif with some interesting structures of various dimensionality ranging from 1D helical and 2D herringbone grid to a complex 3D framework. The deployment of bent acids brings chirality via helicity in the system, as further confirmed by solid-state CD spectra. A detailed investigation of the porous MOFs reveals their importance as zeolite analogues for environment remediation. MOF-1–MOF-5 show some interesting photodegradation of harmful organic dyes. MOF-4 and MOF-5 show impressive selective CO2 gas sorption properties. Furthermore, magnetic properties associated with the trinuclear and hexanuclear SBUs of MOF-1 and MOF-3–MOF-5 have also been investigated.

  • 5. Alhayali, Amani
    et al.
    Tavelin, Staffan
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Pharmacology.
    Velaga, Sitaram
    Dissolution and precipitation behavior of ternary solid dispersions of ezetimibe in biorelevant media2017In: Drug Development and Industrial Pharmacy, ISSN 0363-9045, E-ISSN 1520-5762, Vol. 43, no 1, p. 79-88Article in journal (Refereed)
    Abstract [en]

    The effects of different formulations and processes on inducing and maintaining the supersaturation of ternary solid dispersions of ezetimibe (EZ) in two biorelevant media fasted-state simulated intestinal fluid (FaSSIF) and fasted-state simulated gastric fluid (FaSSGF) at different temperatures (25 °C and 37 °C) were investigated in this work.

    Ternary solid dispersions of EZ were prepared by adding polymer PVP-K30 and surfactant poloxamer 188 using melt-quenching and spray-drying methods. The resulting solid dispersions were characterized using scanning electron microscopy, differential scanning calorimetry (DSC), modulated DSC, powder X-ray diffraction and Fourier transformation infrared spectroscopy. The dissolution of all the ternary solid dispersions was tested in vitro under non-sink conditions.

    All the prepared solid dispersions were amorphous in nature. In FaSSIF at 25 °C, the melt-quenched (MQ) solid dispersions of EZ were more soluble than the spray-dried (SD) solid dispersions and supersaturation was maintained. However, at 37 °C, rapid and variable precipitation behavior was observed for all the MQ and SD formulations. In FaSSGF, the melting method resulted in better solubility than the spray-drying method at both temperatures.

    Ternary solid dispersions show potential for improving solubility and supersaturation. However, powder dissolution experiments of these solid dispersions of EZ at 25 °C may not predict the supersaturation behavior at physiologically relevant temperatures.

  • 6.
    Annamalai, Alagappan
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Sandström, Robin
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Gracia-Espino, Eduardo
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Boulanger, Nicolas
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Boily, Jean-Francois
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Mühlbacher, Inge
    Shchukarev, Andrey
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Wågberg, Thomas
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Influence of Sb5+ as a Double Donor on Hematite (Fe3+) Photoanodes for Surface-Enhanced Photoelectrochemical Water Oxidation2018In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 10, no 19, p. 16467-16473Article in journal (Refereed)
    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.

  • 7. Anugwom, Ikenna
    et al.
    Maki-Arvela, Paivi
    Virtanen, Pasi
    Willfor, Stefan
    Damlin, Pia
    Hedenström, Mattias
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Mikkola, Jyri-Pekka
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Treating birch wood with a switchable 1,8-diazabicyclo-[5.4.0]-undec-7-ene-glycerol carbonate ionic liquid2012In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 66, no 7, p. 809-815Article in journal (Refereed)
    Abstract [en]

    The suitability of a new switchable ionic liquid (SIL) has been investigated as a solvent for fractionation of lignocellulosic materials. SIL was prepared from inexpensive chemicals, e. g., glycerol, CO2, and 1,8-diazabicyclo-[5.4.0]-undec-7-ene (DBU). Fresh Nordic birch wood (B. pendula) was treated with the SIL for a time period of 1-5 days at 100 degrees C and under atmospheric pressure. Upon SIL treatment, at best, 57 % of the hemicelluloses were dissolved and 50 % of lignins were dissolved from the native birch. The slightly fibrillated SIL treated chips contained about 55 % cellulose. Up to 76 % of the recovered species removed from the spent SIL liquor was originating from hemicelluloses, mainly from xylan. The spent SILs were reused for fresh wood dissolution in four consecutive cycles and each time the wood dissolution efficiency was similar. SILs could offer affordable (easy-to-synthesize) solvent systems for partial elimination of hemicelluloses and lignin from wood. SILs can also be prepared in-situ and on-site.

  • 8. Artemenko, A.
    et al.
    Shchukarev, Andrey
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Štenclová, P.
    Wågberg, Thomas
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Segervald, Jonas
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Jia, X.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Kromka, A.
    Reference XPS spectra of amino acids2021Conference paper (Refereed)
    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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  • 9. Asres, Georgies Alene
    et al.
    Baldoví, José J.
    Dombovari, Aron
    Järvinen, Topias
    Lorite, Gabriela Simone
    Mohl, Melinda
    Shchukarev, Andrey
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Pérez Paz, Alejandro
    Xian, Lede
    Mikkola, Jyri-Pekka
    Umeå University, Faculty of Science and Technology, Department of Chemistry. 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 materials2018In: Nano Reseach, ISSN 1998-0124, E-ISSN 1998-0000, Vol. 11, no 8, p. 4215-4224Article in journal (Refereed)
    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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  • 10.
    Auroux, Etienne
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Huseynova, Gunel
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Ràfols-Ribé, Joan
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Miranda la Hera, Vladimir
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Edman, Ludvig
    Umeå University, Faculty of Science and Technology, Department of Physics.
    A metal-free and transparent light-emitting device by sequential spray-coating fabrication of all layers including PEDOT:PSS for both electrodes2023In: RSC Advances, E-ISSN 2046-2069, Vol. 13, no 25, p. 16943-16951Article in journal (Refereed)
    Abstract [en]

    The concept of a metal-free and all-organic electroluminescent device is appealing from both sustainability and cost perspectives. Herein, we report the design and fabrication of such a light-emitting electrochemical cell (LEC), comprising a blend of an emissive semiconducting polymer and an ionic liquid as the active material sandwiched between two poly(3,4-ethylenedioxythiophene):poly(styrene-sulfonate) (PEDOT:PSS) conducting-polymer electrodes. In the off-state, this all-organic LEC is highly transparent, and in the on-state, it delivers uniform and fast to turn-on bright surface emission. It is notable that all three device layers were fabricated by material- and cost-efficient spray-coating under ambient air. For the electrodes, we systematically investigated and developed a large number of PEDOT:PSS formulations. We call particular attention to one such p-type doped PEDOT:PSS formulation that was demonstrated to function as the negative cathode, as well as future attempts towards all-organic LECs to carefully consider the effects of electrochemical doping of the electrode in order to achieve optimum device performance.

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  • 11.
    Auroux, Etienne
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Sandström, Andreas
    LunaLEC AB, Umeå, Sweden.
    Larsen, Christian
    Umeå University, Faculty of Science and Technology, Department of Physics. LunaLEC AB, Umeå, Sweden.
    Zäll, Erik
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Lundberg, Petter
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Wågberg, Thomas
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Edman, Ludvig
    Umeå University, Faculty of Science and Technology, Department of Physics. LunaLEC AB, Umeå, Sweden.
    Evidence and Effects of Ion Transfer at Active-Material/Electrode Interfaces in Solution-Fabricated Light-Emitting Electrochemical Cells2021In: Advanced Electronic Materials, E-ISSN 2199-160X, Vol. 7, no 8, article id 2100253Article in journal (Refereed)
    Abstract [en]

    The light-emitting electrochemical cell (LEC) allows for energy- and cost-efficient printing and coating fabrication of its entire device structure, including both electrodes and the single-layer active material. This attractive fabrication opportunity is enabled by the electrochemical action of mobile ions in the active material. However, a related and up to now overlooked issue is that such solution-fabricated LECs commonly comprise electrode/active-material interfaces that are open for transfer of the mobile ions, and it is herein demonstrated that a majority of the mobile anions in a common spray-coated active material can transfer into a spray-coated poly(3,4-ethylenedioxythiophene):poly(styrene-sulfonate) (PEDOT:PSS) positive electrode during LEC operation. Since it is well established that the mobile ion concentration in the active material has a profound influence on the LEC performance, this significant ion transfer is an important factor that should be considered in the design of low-cost LEC devices that deliver high performance.

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  • 12. Baburin, Igor A
    et al.
    Klechikov, Alexey
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Mercier, Guillaume
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Talyzin, Alexandr
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Seifert, Gotthard
    Hydrogen adsorption by perforated graphene2015In: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 40, no 20, p. 6594-6599Article in journal (Refereed)
    Abstract [en]

    We performed a combined theoretical and experimental study of hydrogen adsorption in graphene systems with defect-induced additional porosity. It is demonstrated that perforation of graphene sheets results in increase of theoretically possible surface areas beyond the limits of ideal defect-free graphene (∼2700 m2/g) with the values approaching ∼5000 m2/g. This in turn implies promising hydrogen storage capacities up to 6.5 wt% at 77 K, estimated from classical Grand canonical Monte Carlo simulations. Hydrogen sorption was studied for the samples of defected graphene with surface area of ∼2900 m2/g prepared using exfoliation of graphite oxide followed by KOH activation. The BET surface area of studied samples thus exceeded the value of single-layered graphene. Hydrogen uptake measured at 77 K and 296 K amounts to 5.5 wt% (30 bar) and to 0.89 wt% (120 bar), respectively. 

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  • 13.
    Bala, Sukhen
    et al.
    School of Chemical Science, Indian Association for the Cultivation of Science, Kolkata, India; Key Laboratory of Bioinorganic and Synthetic Chemistry of Ministry of Education, School of Chemistry, Sun Yat-Sen University, Guangzhou, P. R. China.
    De, Avik
    School of Chemical Science, Indian Association for the Cultivation of Science, Kolkata, India.
    Adhikary, Amit
    School of Chemical Science, Indian Association for the Cultivation of Science, Kolkata, West Bengal, India.
    Saha, Sayan
    School of Chemical Science, Indian Association for the Cultivation of Science, Kolkata, India.
    Akhtar, Sohel
    School of Chemical Science, Indian Association for the Cultivation of Science, Kolkata, India.
    Das, Krishna Sundar
    School of Chemical Science, Indian Association for the Cultivation of Science, Kolkata, India.
    Tong, Ming-Liang
    Key Laboratory of Bioinorganic and Synthetic Chemistry of Ministry of Education, School of Chemistry, Sun Yat-Sen University, Guangzhou, P. R. China.
    Mondal, Raju
    School of Chemical Science, Indian Association for the Cultivation of Science, Kolkata, India.
    Influence of Semirigidity and Diverse Binding Modes of an Asymmetric Pyridine-pyrazole Based Bis-Chelating Ligand in Controlling Molecular Architectures and Their Properties2020In: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 20, no 9, p. 5698-5708Article in journal (Refereed)
  • 14. Barišić, Antun
    et al.
    Lützenkirchen, Johannes
    Bebić, Nikol
    Li, Qinzhi
    Hanna, Khalil
    Shchukarev, Andrey
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Begović, Tajana
    Experimental Data Contributing to the Elusive Surface Charge of Inert Materials in Contact with Aqueous Media2021In: Colloids and interfaces, E-ISSN 2504-5377, Vol. 5, no 1, article id 6Article in journal (Other academic)
    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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  • 15.
    Barzegar, Hamid Reza
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Gracia-Espino, Eduardo
    Umeå University, Faculty of Science and Technology, Department of Physics. Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Sharifi, Tiva
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Nitze, Florian
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Wågberg, Thomas
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Nitrogen Doping Mechanism in Small Diameter Single-Walled Carbon Nanotubes: Impact on Electronic Properties and Growth Selectivity2013In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 117, no 48, p. 25805-25816Article in journal (Refereed)
    Abstract [en]

    Nitrogen doping in carbon nanostructures has attracted interest for more than a decade, and recent implementation of such structures in energy conversion systems has boosted the interest even more. Despite numerous studies, the structural conformation and stability of nitrogen functionalities in small diameter single-walled carbon nanotubes (SWNTs), and the impact of these functionalities on the electronic and mechanical properties of the SWNTs, are incomplete. Here we report a detailed study on nitrogen doping in SWNTs with diameters in the range of 0.8?1.0 nm, with well-defined chirality. We show that the introduction of nitrogen in the carbon framework significantly alters the stability of certain tubes, opening for the possibility to selectively grow nitrogen-doped SWNTs with certain chirality and diameter. At low nitrogen concentration, pyridinic functionalities are readily incorporated and the tubular structure is well pertained. At higher concentrations, pyrrolic functionalities are formed, which leads to significant structural deformation of the nanotubes and hence a stop in growth of crystalline SWNTs. Raman spectroscopy is an important tool to understand guest atom doping and electronic charge transfer in SWNTs. By correlating the influence of defined nitrogen functionalities on the electronic properties of SWNTs with different chirality, we make precise interpretation of experimental Raman data. We show that the previous interpretation of the double-resonance G?-peak in many aspects is wrong and instead can be well-correlated to the type of nitrogen doping of SWNTs originating from the p- or n-doping nature of the nitrogen incorporation. Our results are supported by experimental and theoretical data.

  • 16. Behravesh, Erfan
    et al.
    Kumar, Narendra
    Balme, Quentin
    Roine, Jorma
    Salonen, Jarno
    Shchukarev, Andrey
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Mikkola, Jyri-Pekka
    Umeå University, Faculty of Science and Technology, Department of Chemistry. 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 acidity2017In: Journal of Catalysis, ISSN 0021-9517, E-ISSN 1090-2694, Vol. 353, p. 223-238Article in journal (Refereed)
    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.

  • 17. Biryulin, YF
    et al.
    Kurdybaylo, D
    Shamanin, V
    Aleksjuk, G
    Volkova, T
    Melenevskaya, E
    Saydashev, I
    Eidelman, E
    Makarova, Tatiana
    Ioffe Physico-Technical Institute RAS, Russia.
    Terukov, E
    Zaitseva, N
    Negrov, V
    Tkatchyov, A
    Strongly non-linear carbon nanofibre influence on electrical properties of polymer composites2008In: Fullerenes, nanotubes, and carbon nanostructures, ISSN 1536-383X, E-ISSN 1536-4046, Vol. 16, no 5-6, p. 629-633Article in journal (Refereed)
    Abstract [en]

    Composites of carbon nanofibres (CNF) (30-50 nm diam., length up to 1 mu m) in two polymer matrices (polybutadiene-styrene and polypyrrhol) show strong non-linearities of conductivity vs. CNF concentration. We have studied their voltage-current dependencies, and observed correlation of their extrema and layer morphology. Multistability of conductivity is discovered, with apparent effect of magnetic field effect on it in polypyrrhol-based composites. In addition CNF spatial configuration influence on layers' conductivity is discussed.

  • 18.
    Boily, Jean-Francois
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Yesilbas, Merve
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Uddin, Munshi Md. Musleh
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Baiqing, Lu
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Trushkina, Yulia
    Salazar-Alvarez, German
    Thin Water Films at Multifaceted Hematite Particle Surfaces2015In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 31, no 48, p. 13127-13137Article in journal (Refereed)
    Abstract [en]

    Mineral surfaces exposed to moist air stabilize nanometer- to micrometer-thick water films. This study resolves the nature of thin water film formation at multifaceted hematite (alpha-Fe2O3) nanoparticle surfaces with crystallographic faces resolved by selected area electron diffraction. Dynamic vapor adsorption (DVA) in the 0-19 Torr range at 298 K showed that these particles stabilize water films consisting of up to 4-5 monolayers. Modeling of these data predicts water loadings in terms of an "adsorption regime" (up to 16 H2O/nm(2)) involving direct water binding to hematite surface sites, and of a "condensation regime" (up to 34 H2O/nm(2)) involving water binding to hematite-bound water nanodusters. Vibration spectroscopy identified the predominant hematite surface hydroxo groups (-OH, mu-OH, mu(3)-OH) through which first layer water molecules formed hydrogen bonds, as well as surface iron sites directly coordinating water molecules (i.e., as geminal eta-(OH2)(2) sites). Chemometric analyses of the vibration spectra also revealed a strong correspondence in the response of hematite surface hydroxo groups to DVA-derived water loadings. These findings point to a near-saturation of the hydrogen-bonding environment of surface hydroxo groups at a partial water vapor pressure of similar to 8 Torr (similar to 40% relative humidity). Classical molecular dynamics (MD) resolved the interfacial water structures and hydrogen bonding populations at five representative crystallographic faces expressed in these nanoparticles. Simulations of single oriented slabs underscored the individual roles of all (hydro)oxo groups in donating and accepting hydrogen bonds with first layer water in the "adsorption regime". These analyses pointed to the preponderance of hydrogen bond-donating -OH groups in the stabilization of thin water films. Contributions of mu-OH and mu(3)-OH groups are secondary, yet remain essential in the stabilization of thin water films. MD simulations also helped resolve crystallographic controls on water water interactions occurring in the "condensation regime". Water water hydrogen bond populations are greatest on the (001) face, and decrease in importance in the order (001) > (012) approximate to (110) > (014) >> (100). Simulations of a single (similar to 5 nm x similar to 6 nm x similar to 6 nm) nanometric hematite particle terminated by the (001), (110), (012), and (100) faces also highlighted the key roles that sites at particle edges play in interconnecting thin water films grown along contiguous crystallographic faces. Hydroxo water hydrogen bond populations showed that edges were the preferential loci of binding. These simulations also suggested that equilibration times for water binding at edges were slower than on crystallographic faces. In this regard, edges, and by extension roughened surfaces, are expected to play commanding roles in the stabilization of thin water films. Thus, in focusing on the properties of nanometric-thick water layers at hematite surfaces, this study revealed the nature of interactions between water and multifaced particle surfaces. Our results pave the way for furthering our understanding of mineral-thin water film interfacial structure and reactivity on a broader range of materials.

  • 19.
    Boulanger, Nicolas
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Kuzenkova, Anastasiia S.
    Department of Chemistry, Lomonosov Moscow State University, Leninskie Gory, Moscow, Russian Federation.
    Iakunkov, Artem
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Nordenström, Andreas
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Romanchuk, Anna Yu.
    Department of Chemistry, Lomonosov Moscow State University, Leninskie Gory, Moscow, Russian Federation.
    Trigub, Alexander L.
    Department of Chemistry, Lomonosov Moscow State University, Leninskie Gory, Moscow, Russian Federation; National Research Centre “Kurchatov Institute”, Moscow, Russian Federation.
    Zasimov, Pavel V.
    Department of Chemistry, Lomonosov Moscow State University, Leninskie Gory, Moscow, Russian Federation.
    Prodana, Mariana
    Center for Surface Science and Nanotechnology, University Politehnica of Bucharest, Splaiul Independentei 313, Bucharest, Romania.
    Enachescu, Marius
    Center for Surface Science and Nanotechnology, University Politehnica of Bucharest, Splaiul Independentei 313, Bucharest, Romania; Academy of Romanian Scientists, Splaiul Independentei 54, Bucharest, Romania.
    Bauters, Stephen
    Helmholtz Zentrum Dresden-Rossendorf (HZDR), Institute of Resource Ecology, Dresden, Germany; The Rossendorf Beamline at ESRF, The European Synchrotron, CS40220, Grenoble Cedex 9, France.
    Amidani, Lucia
    Helmholtz Zentrum Dresden-Rossendorf (HZDR), Institute of Resource Ecology, Dresden, Germany; The Rossendorf Beamline at ESRF, The European Synchrotron, CS40220, Grenoble Cedex 9, France.
    Kvashnina, Kristina O.
    Helmholtz Zentrum Dresden-Rossendorf (HZDR), Institute of Resource Ecology, Dresden, Germany; The Rossendorf Beamline at ESRF, The European Synchrotron, CS40220, Grenoble Cedex 9, France.
    Kalmykov, Stepan N.
    Department of Chemistry, Lomonosov Moscow State University, Leninskie Gory, Moscow, Russian Federation.
    Talyzin, Aleksandr V.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    High Surface Area "3D Graphene Oxide" for Enhanced Sorption of Radionuclides2022In: Advanced Materials Interfaces, ISSN 2196-7350, Vol. 9, no 18, article id 2200510Article in journal (Refereed)
    Abstract [en]

    Here preparation of high surface area activated reduced graphene oxide (arGO) oxidized into a 3D analogue of defect-rich GO (dGO) is reported. Surface oxidation of arGO results in carbon to oxygen ratio C/O = 3.3, similar to the oxidation state of graphene oxide while preserving high BET surface area of about 880 m2 g−1. Analysis of surface oxidized arGO shows high abundance of oxygen functional groups which converts hydrophobic precursor into hydrophilic material. High surface area carbons provide the whole surface for oxidation without the need of intercalation and lattice expansion. Therefore, surface oxidation methods are sufficient to convert the materials into 3D architectures with chemical properties similar to graphene oxide. The "3D graphene oxide" shows high sorption capacity for U(VI) removal in an extraordinary broad interval of pH. Notably, the surface oxidized carbon material has a rigid 3D structure with micropores accessible for penetration of radionuclide ions. Therefore, the bulk "3D GO" can be used as a sorbent directly without dispersing, the step required for GO to make its surface area accessible for pollutants.

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  • 20.
    Boulanger, Nicolas
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Kuzenkova, Anastasiia S.
    Iakunkov, Artem
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Romanchuk, Anna Yu
    Trigub, Alexander L.
    Egorov, Alexander, V
    Bauters, Stephen
    Amidani, Lucia
    Retegan, Marius
    Kvashnina, Kristina O.
    Kalmykov, Stepan N.
    Talyzin, Aleksandr V.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Enhanced Sorption of Radionuclides by Defect-Rich Graphene Oxide2020In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 12, no 40, p. 45122-45135Article in journal (Refereed)
    Abstract [en]

    Extremely defect graphene oxide (dGO) is proposed as an advanced sorbent for treatment of radioactive waste and contaminated natural waters. dGO prepared using a modified Hummers oxidation procedure, starting from reduced graphene oxide (rGO) as a precursor, shows significantly higher sorption of U(VI), Am(III), and Eu(III) than standard graphene oxides (GOs). Earlier studies revealed the mechanism of radionuclide sorption related to defects in GO sheets. Therefore, explosive thermal exfoliation of graphite oxide was used to prepare rGO with a large number of defects and holes. Defects and holes are additionally introduced by Hummers oxidation of rGO, thus providing an extremely defect-rich material. Analysis of characterization by XPS, TGA, and FTIR shows that dGO oxygen functionalization is predominantly related to defects, such as flake edges and edge atoms of holes, whereas standard GO exhibits oxygen functional groups mostly on the planar surface. The high abundance of defects in dGO results in a 15-fold increase in sorption capacity of U(VI) compared to that in standard Hummers GO. The improved sorption capacity of dGO is related to abundant carboxylic group attached hole edge atoms of GO flakes as revealed by synchrotron-based extended X-ray absorption fine structure (EXAFS) and high-energy resolution fluorescence detected X-ray absorption near edge structure (HERFD-XANES) spectroscopy.

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  • 21.
    Boulanger, Nicolas
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Li, Gui
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Bakhiia, Tamuna
    Department of Chemistry, Lomonosov Moscow State University, Leninskie Gory, Moscow, Russian Federation.
    Maslakov, Konstantin I.
    Department of Chemistry, Lomonosov Moscow State University, Leninskie Gory, Moscow, Russian Federation.
    Romanchuk, Anna Yu.
    Department of Chemistry, Lomonosov Moscow State University, Leninskie Gory, Moscow, Russian Federation.
    Kalmykov, Stepan N.
    Department of Chemistry, Lomonosov Moscow State University, Leninskie Gory, Moscow, Russian Federation.
    Talyzin, Aleksandr V.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Super-oxidized “activated graphene” as 3D analogue of defect graphene oxide: oxidation degree vs U(VI) sorption2023In: Journal of Hazardous Materials, ISSN 0304-3894, E-ISSN 1873-3336, Vol. 457, article id 131817Article in journal (Refereed)
    Abstract [en]

    Porous carbons are not favorable for sorption of heavy metals and radionuclides due to absence of suitable binding sites. In this study we explored the limits for surface oxidation of “activated graphene” (AG), porous carbon material with the specific surface area of ∼2700 m2/g produced by activation of reduced graphene oxide (GO). Set of “Super-Oxidized Activated Graphene” (SOAG) materials with high abundance of carboxylic groups on the surface were produced using “soft” oxidation. High degree of oxidation comparable to standard GO (C/O=2.3) was achieved while keeping 3D porous structure with specific surface area of ∼700–800 m2/. The decrease in surface area is related to the oxidation-driven collapse of mesopores while micropores showed higher stability. The increase in the oxidation degree of SOAG is found to result in progressively higher sorption of U(VI), mostly related to the increase in abundance of carboxylic groups. The SOAG demonstrated extraordinarily high sorption of U(VI) with the maximal capacity up to 5400 μmol/g, that is 8.4 – fold increase compared to non-oxidized precursor AG, ∼50 –fold increase compared to standard graphene oxide and twice higher than extremely defect-rich graphene oxide. The trends revealed here show a way to further increase sorption if similar oxidation degree is achieved with smaller sacrifice of surface area.

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  • 22.
    Boulanger, Nicolas
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Skrypnychuk, Vasyl
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Nordenström, Andreas
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Moreno-Fernández, Gelines
    Centre for Cooperative Research on Alternative Energies (CIC energiGUNE), Basque Research and Technology Alliance (BRTA) Alava Technology Park, Vitoria-Gasteiz, Spain.
    Granados-Moreno, Miguel
    Centre for Cooperative Research on Alternative Energies (CIC energiGUNE), Basque Research and Technology Alliance (BRTA) Alava Technology Park, Vitoria-Gasteiz, Spain.
    Carriazo, Daniel
    Centre for Cooperative Research on Alternative Energies (CIC energiGUNE), Basque Research and Technology Alliance (BRTA) Alava Technology Park, Vitoria-Gasteiz, Spain.
    Mysyk, Roman
    Centre for Cooperative Research on Alternative Energies (CIC energiGUNE), Basque Research and Technology Alliance (BRTA) Alava Technology Park, Vitoria-Gasteiz, Spain.
    Bracciale, Gaetan
    Thales Research & Technology, Palaiseau, France.
    Bondavalli, Paolo
    Thales Research & Technology, Palaiseau, France.
    Talyzin, Alexandr V.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Spray deposition of supercapacitor electrodes using environmentally friendly aqueous activated graphene and activated carbon dispersions for industrial implementation2021In: ChemElectroChem, E-ISSN 2196-0216, Vol. 8, no 7, p. 1349-1361Article in journal (Refereed)
    Abstract [en]

    A spray gun machine was used to deposit high‐surface‐area supercapacitor electrodes using green non‐toxic aqueous dispersions based on different kinds of high specific surface area nanostructured carbon materials: activated graphene (a‐rGO) and activated carbon (AC). Tuning the spray conditions and dispersion formulation allowed us to achieve good adhesion to stainless‐steel current collectors in combination with high surface area and a satisfactory mechanical stability of the electrodes. The specific surface area of approximately 2000 m2/g was measured directly on a‐rGO and AC electrodes showing only around a 20 % decrease compared to the precursor powder materials. The performance of the electrodes deposited on stainless‐steel and aluminum current collectors was tested in supercapacitor devices using three electrolytes. The electrodes were tested in an “as‐deposited” state and after post‐deposition annealing at 200 °C. The spray deposition method and post‐deposition annealing are completely compatible with roll‐to‐roll industrial production methods. The a‐rGO demonstrated superior performance compared to AC in supercapacitor electrodes with gravimetric capacitance, energy, and power density parameters, which exceed commercially available analogues. The formulation of the dispersions used in this study is environmentally friendly, as it is based on only on water as a solvent and commercially available non‐toxic additives (graphene oxide, fumed silica, and carbon nanotubes).

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  • 23.
    Boulanger, Nicolas
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Yu, Victor
    Hilke, Michael
    Toney, Michael F.
    Barbero, David R.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Graphene induced electrical percolation enables more efficient charge transport at a hybrid organic semiconductor/graphene interface2018In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 20, no 6, p. 4422-4428Article in journal (Refereed)
    Abstract [en]

    Self-assembly of semiconducting polymer chains during crystallization from a liquid or melt dictates to a large degree the electronic properties of the resulting solid film. However, it is still unclear how charge transport pathways are created during crystallization. Here, we performed complementary in situ electrical measurements and synchrotron grazing incidence X-ray diffraction (GIXD), during slow cooling from the melt of highly regio-regular poly(3-hexylthiophene) (P3HT) films deposited on both graphene and on silicon. Two different charge transport mechanisms were identified, and were correlated to the difference in crystallites' orientations and overall amount of crystallites in the films on each surface as molecular self-assembly proceeded. On silicon, a weak charge transport was enabled as soon as the first edge-on lamellae formed, and further increased with the higher amount of crystallites (predominantly edge-on and randomly oriented lamellae) during cooling. On graphene however, the current remained low until a minimum amount of crystallites was reached, at which point interconnection of conducting units (face-on, randomly oriented lamellae and tie-chains) formed percolated conducting pathways across the film. This lead to a sudden rapid increase in current by approximate to 10 fold, and strongly enhanced charge transport, despite a much lower amount of crystallites than on silicon.

  • 24.
    Bui, Thai Q.
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Konwar, Lakhya Jyoti
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Samikannu, Ajaikumar
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Nikjoo, Dariush
    Division of Materials Science, Luleå University of Technology, Luleå, Sweden.
    Mikkola, Jyri-Pekka
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Laboratory of Industrial Chemistry and Reaction Engineering, Johan Gadolin Process Chemistry Centre, Åbo Akademi University, Turku, Finland.
    Mesoporous Melamine-Formaldehyde Resins as Efficient Heterogeneous Catalyst for Continuous Synthesis of Cyclic Carbonates from Epoxides and gaseous CO22020In: ACS Sustainable Chemistry and Engineering, E-ISSN 2168-0485, Vol. 8, no 34, p. 12852-12869Article in journal (Refereed)
    Abstract [en]

    Herein we report the application of inexpensive mesoporous melamine-formaldehyde resins (MMFR and MMFR250) obtained by a novel template-free and organosolvent-free hydrothermal method as efficient heterogeneous catalysts for direct synthesis of cyclic carbonates from CO2 and epoxides (epichlorohydrin, butylene oxide and styrene oxide). The catalytic activity of the melamine resins was attributed to the abundant Lewis basic N-sites capable of activating CO2 molecules. Based on CO2-Temperature programmed desorption, the concentration of surface basic sites for MMFR and MMFR250 were estimated to be 172 and 56 µmol/g, while the activation energy of CO2 desorption (strength of basic sites) were calculated to be 92.1 and 64.5 kJ/mol. We also observed considerable differences in the catalytic activity and stability of polymeric catalysts in batch and in continuous-flow mode; due to the existence of a synergism between adsorption of CO2 and cyclic carbonates (poison). Our experiments also revealed important role of catalyst surface chemistry and CO2 partial pressure upon catalyst poisoning. Nevertheless, owing to their unique properties (large specific surface area, large mesoporous and CO2 basicity) melamine resins presented excellent activity (turnover frequency 207-2147 h-1), selectivity (>99%) for carbonation of epoxides with CO2 (20 bar initial CO2 or CO2:epoxide mole ratio ~1.5) under solvent-free and co-catalyst-free conditions at 100-120 oC. Most importantly, these low-cost polymeric catalysts were reusable and demonstrated exceptional stability in a flow reactor (tested upto 13 days time on stream, weight hourly space velocity 0.26-1.91 h-1) for continuous cyclic carbonate production from gaseous CO2 with different epoxides (conversion 76-100% and selectivity >99%) under industrially relevant conditions (120 oC, 13 bar, solvent-free/co-catalyst-free) confirming their superiority over the previously reported catalytic materials.

  • 25.
    Calderon, Blanca
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Univ Alicante, Dept Chem Engn, San Vicente del Raspeig Rd S-N, Alicante 03690, Spain.
    Lundin, Lisa
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Aracil, Ignacio
    Fullana, Andres
    Study of the presence of PCDDs/PCDFs on zero-valent iron nanoparticles2017In: Chemosphere, ISSN 0045-6535, E-ISSN 1879-1298, Vol. 169, p. 361-368Article in journal (Refereed)
    Abstract [en]

    Studies show that nanoscale zero-valent iron (nZVI) particles enhance the formation of chlorinated compounds such as polychlorinated dioxins and furans (PCDD/Fs) during thermal processes. However, it is unclear whether nZVI acts as a catalyst for the formation of these compounds or contains impurities, such as PCDD/Fs, within its structure. We analyzed the presence of PCDD/Fs in nZVI particles synthesized through various production methods to elucidate this uncertainty. None of the 2,3,7,8-substituted congeners were found in the commercially-produced nZVI, but they were present in the laboratory synthesized nZVI produced through the borohydride method, particularly in particles synthesized from iron (III) chloride rather than from iron sulfate. Total PCDD/F WHO-TEQ concentrations of up to 35 pg/g were observed in nZVI particles, with hepta-and octa-chlorinated congeners being the most abundant. The reagents used in the borohydride method were also analyzed, and our findings suggest that FeCl3 effectively contains PCDD/Fs at concentrations that could explain the concentrations observed in the nZVI product. Both FeCl3 and nZVI showed a similar PCDD/F patterns with slight differences. These results suggest that PCDD/Fs might transfer from FeCl3 to nZVI during the production method, and thus, care should be taken when employing certain nZVI for environmental remediation.

  • 26. Cano, A.
    et al.
    Rodríguez-Hernández, J.
    Shchukarev, Andrey
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Reguera, E.
    Intercalation of pyrazine in layered copper nitroprusside: synthesis, crystal structure and XPS study2019In: Journal of Solid State Chemistry, ISSN 0022-4596, E-ISSN 1095-726X, Vol. 273, p. 1-10Article in journal (Refereed)
    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.

  • 27.
    Cant, David J. H.
    et al.
    National Physical Laboratory, Teddington, UK.
    Pei, Yiwen
    National Physical Laboratory, Teddington, UK.
    Shchukarev, Andrey
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Ramstedt, Madeleine
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    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 nanomedicines2023In: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 127, no 39, p. 8220-8227Article in journal (Refereed)
    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.

  • 28. Carvalho, Paulo H. B. Brant
    et al.
    Mace, Amber
    Andersson, Ove
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Tulk, Chris A.
    Molaison, Jamie
    Haussermann, Ulrich
    Elucidating the guest disorder in structure II argon hydrate: A neutron diffraction isotopic substitution study2020In: Journal of Solid State Chemistry, ISSN 0022-4596, E-ISSN 1095-726X, Vol. 285, article id 121220Article in journal (Refereed)
    Abstract [en]

    Clathrate hydrates with the cubic structure II (CS-II) form typically with large guest molecules, such as tetrahydrofuran, trimethylamine oxide, or propane. However, CS-II is also realized for argon hydrate despite the comparatively small van der Waals diameter of the guest (around 3.8 angstrom). Here, the structure of deuterated argon hydrate was studied at ambient pressure in the temperature range 20-95 K using neutron diffraction and comparing natural Ar with Ar-36, which scatters neutrons more than 13 times more efficiently. The procedure allowed to unambiguously establish the positional disorder within the large cages of CS-H, while simultaneously refining host and guest structures. These cages are singly occupied and off-centered argon atoms distribute on two tetrahedron-shaped split positions with a ratio 3:1. Molecular dynamics (MD) simulations revealed that the crystallographic positional disorder structure is due to mobile argon atoms even at 20 K. The MD potential energy distribution confirmed the diffraction model. It is noted that the unit cell volumes of argon hydrate in the investigated temperature range are virtually identical to N-2 hydrate, which has a similar composition at ambient pressure, indicating a very similar (slightly attractive) host-guest interaction.

  • 29. Chen, Yuqing
    et al.
    He, Qiu
    Zhao, Yun
    Zhou, Wang
    Xiao, Peitao
    Gao, Peng
    Tavajohi Hassan Kiadeh, Naser
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Tu, Jian
    Li, Baohua
    He, Xiangming
    Xing, Lidan
    Fan, Xiulin
    Liu, Jilei
    Breaking solvation dominance of ethylene carbonate via molecular charge engineering enables lower temperature battery2023In: Nature Communications, E-ISSN 2041-1723, Vol. 14, article id 8326Article in journal (Refereed)
    Abstract [en]

    Low temperatures severely impair the performance of lithium-ion batteries, which demand powerful electrolytes with wide liquidity ranges, facilitated ion diffusion, and lower desolvation energy. The keys lie in establishing mild interactions between Li+ and solvent molecules internally, which are hard to achieve in commercial ethylene-carbonate based electrolytes. Herein, we tailor the solvation structure with low-ε solvent-dominated coordination, and unlock ethylene-carbonate via electronegativity regulation of carbonyl oxygen. The modified electrolyte exhibits high ion conductivity (1.46 mS·cm−1) at −90 °C, and remains liquid at −110 °C. Consequently, 4.5 V graphite-based pouch cells achieve ~98% capacity over 200 cycles at −10 °C without lithium dendrite. These cells also retain ~60% of their room-temperature discharge capacity at −70 °C, and miraculously retain discharge functionality even at ~−100 °C after being fully charged at 25 °C. This strategy of disrupting solvation dominance of ethylene-carbonate through molecular charge engineering, opens new avenues for advanced electrolyte design.

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  • 30.
    Cheng, Wei
    et al.
    College of Resources and Environmental Science, South-Central University for Nationalities, Wuhan, China.
    Marsac, Rémi
    Université Rennes, CNRS, Géosciences Rennes-UMR 6118, Rennes, France.
    Hanna, Khalil
    Université Rennes, Ecole Nationale Supérieure de Chimie de Rennes, UMR CNRS 6226, 11 Allée de Beaulieu, Cedex 7, Rennes, France; Institut Universitaire de France (IUF), MESRI, 1 rue Descartes, Paris, France.
    Boily, Jean-Francois
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Competitive Carboxylate-Silicate Binding at Iron Oxyhydroxide Surfaces2021In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 37, no 44, p. 13107-13115Article in journal (Refereed)
    Abstract [en]

    Dissolved silicate ions in wet and dry soils can determine the fate of organic contaminants via competitive binding. While fundamental surface science studies have advanced knowledge of binding in competitive systems, little is still known about the ranges of solution conditions, the time dependence, and the molecular processes controlling competitive silicate-organic binding on minerals. Here we address these issues by describing the competitive adsorption of dissolved silicate and of phthalic acid (PA), a model carboxylate-bearing organic contaminant, onto goethite, a representative natural iron oxyhydroxide nanomineral. Using surface complexation thermodynamic modeling of batch adsorption data and chemometric analyses of vibrational spectra, we find that silicate concentrations representative of natural waters (50-1000 μM) can displace PA bound at goethite surfaces. Below pH ∼8, where PA binds, every bound Si atom removes ∼0.3 PA molecule by competing with reactive singly coordinated hydroxo groups (-OH) on goethite. Long-term (30 days) reaction time and a high silicate concentration (1000 μM) favored silicate polymer formation, and increased silicate while decreasing PA loadings. The multisite complexation model predicted PA and silicate binding in terms of the competition for -OH groups without involving PA/silicate interactions, and in terms of a lowering of outer-Helmholtz potentials of the goethite surface by these anions. The model predicted that silicate binding lowered loadings of PA species, and whose two carboxylate groups are hydrogen- (HB) and metal-bonded (MB) with goethite. Vibrational spectra of dried samples revealed that the loss of water favored greater proportions of MB over HB species, and these coexisted with predominantly monomeric silicate species. These findings underscored the need to develop models for a wider range of organic contaminants in soils exposed to silicate species and undergoing wet-dry cycles.

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  • 31. Chilkoor, Govinda
    et al.
    Karanam, Sushma Priyanka
    Star, Shane
    Shrestha, Namita
    Sani, Rajesh K.
    Upadhyayula, Venkata K. K.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Ghoshal, Debjit
    Koratkar, Nikhil A.
    Meyyappan, M.
    Gadhamshetty, Venkataramana
    Hexagonal Boron Nitride: The Thinnest Insulating Barrier to Microbial Corrosion2018In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 12, no 3, p. 2242-2252Article in journal (Refereed)
    Abstract [en]

    We report the use of a single layer of two-dimensional hexagonal boron nitride (SL-hBN) as the thinnest insulating barrier to microbial corrosion induced by the sulfate-reducing bacteria Desulfovibrio alaskensis G20. We used electrochemical methods to assess the corrosion resistance of SL-hBN on copper against the effects of both the planktonic and sessile forms of the sulfate-reducing bacteria. Cyclic voltammetry results show that SL-hBN-Cu is effective in suppressing corrosion effects of the planktonic cells at potentials as high as 0.2 V (vs Ag/AgCl). The peak anodic current for the SL-hBN coatings is ∼36 times lower than that of bare Cu. Linear polarization resistance tests confirm that the SL-hBN coatings serve as a barrier against corrosive effects of the G20 biofilm when compared to bare Cu. The SL-hBN serves as an impermeable barrier to aggressive metabolites and offers ∼91% corrosion inhibition efficiency, which is comparable to much thicker commercial coatings such as polyaniline. In addition to impermeability, the insulating nature of SL-hBN suppresses galvanic effects and improves its ability to combat microbial corrosion.

  • 32. Cui, Wen
    et al.
    Yao, Mingguang
    Yao, Zhen
    Ma, Fengxian
    Li, Quanjun
    Liu, Ran
    Liu, Bo
    Zou, Bo
    Cui, Tian
    Liu, Bingbing
    Sundqvist, Bertil
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Reversible pressure-induced polymerization of Fe(C5H5)(2) doped C-702013In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 62, p. 447-454Article in journal (Refereed)
    Abstract [en]

    High pressure Raman, IR and X-ray diffraction (XRD) studies have been carried out on C-70(Fe(C5H5)(2))(2) (hereafter, "C-70(Fc)(2)") sheets. Theoretical calculation is further used to analyze the Electron Localization Function (ELF) and charge transfer in the crystal and thus to understand the transformation of C-70(Fc)(2) under pressure. Our results show that even at room temperature dimeric phase and one dimensional (1D) polymer phase of C-70 molecules can be formed at about 3 and 8 GPa, respectively. The polymerization is found to be reversible Upon decompression and the reversibility is related to the pressure-tuned charge transfer, as well as the overridden steric repulsion of counter ions. According to the layered structure of the intercalated ferrocene molecules formed in the crystal, we suggest that ferrocene acts as not only a spacer to restrict the polymerization of C-70 molecules within a layer, but also as charge reservoir to tune the polymerization process. This supplies a possible way for us to design the polymerization of fullerenes at suitable conditions.

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  • 33.
    Cwik, Katarzyna
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Broström, Markus
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Backlund, Krister
    Fjäder, Kenneth
    Hiljanen, Emil
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Eriksson, Matias
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics. Swedish Mineral Processing Research Association MinFo, Stockholm, Sweden.
    Thermal decrepitation and thermally-induced cracking of limestone used in quicklime production2022In: Minerals, E-ISSN 2075-163X, Vol. 12, no 10, article id 1197Article in journal (Refereed)
    Abstract [en]

    To produce quicklime, high calcium carbonate rocks, including limestone, are burned in industrial kilns at 1100–1450 °C. As a consequence of the high temperatures, the carbonate rock can break and decrepitate into fine material, causing operational problems and material losses. In the present paper, an industrial case study on thermal decrepitation was performed on Boda Limestone from the Jutjärn quarry in Dalarna, Sweden. We analyzed 80 limestone samples for thermal decrepitation; furthermore, the correlation with chemical composition was statistically analyzed. The experiments were complemented by a detailed analysis of thermally-induced cracking at a range of temperatures (ambient, 500 °C, 800 °C, and 1150 °C) for two limestone samples with similar chemical compositions but with very different decrepitation behaviors. Decrepitation was analyzed by an in-house method, the chemical composition by XRF, and the thermally-induced cracking was investigated by SEM and image analysis. No strong correlation was found between thermal decrepitation and the chemical composition of the limestone. For the sample with low thermal decrepitation, a dense narrow network of fractures was found after full calcination; however, this network was not observed in the sample with high thermal decrepitation. A plausible explanation for the different decrepitation behaviors is that this fracture network releases internal stress and stabilizes the calcined rock. The obtained results can help in predicting limestone thermal decrepitation, enabling increased resource efficiency in quicklime production.

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  • 34. Dardouri, Maïssa
    et al.
    Bettencourt, Ana
    Martin, Victor
    Carvalho, Filomena A.
    Colaço, Bruno
    Gama, Adelina
    Ramstedt, Madeleine
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Santos, Nuno C.
    Fernandes, Maria H.
    Gomes, Pedro S.
    Ribeiro, Isabel A. C.
    Assuring the Biofunctionalization of Silicone Covalently Bonded to Rhamnolipids: Antibiofilm Activity and Biocompatibility2022In: Pharmaceutics, ISSN 1999-4923, E-ISSN 1999-4923, Vol. 14, no 9, article id 1836Article in journal (Refereed)
    Abstract [en]

    Silicone-based medical devices composed of polydimethylsiloxane (PDMS) are widely used all over the human body (e.g., urinary stents and catheters, central venous catheters stents) with extreme clinical success. Nevertheless, their abiotic surfaces, being prone to microorganism colonization, are often involved in infection occurrence. Improving PDMS antimicrobial properties by surface functionalization with biosurfactants to prevent related infections has been the goal of different works, but studies that mimic the clinical use of these novel surfaces are missing. This work aims at the biofunctional assessment of PDMS functionalized with rhamnolipids (RLs), using translational tests that more closely mimic the clinical microenvironment. Rhamnolipids were covalently bonded to PDMS, and the obtained surfaces were characterized by contact angle modification assessment, ATR-FTIR analysis and atomic force microscopy imaging. Moreover, a parallel flow chamber was used to assess the Staphylococcus aureus antibiofilm activity of the obtained surfaces under dynamic conditions, and an in vitro characterization with human dermal fibroblast cells in both direct and indirect characterization assays, along with an in vivo subcutaneous implantation assay in the translational rabbit model, was performed. A 1.2 log reduction in S. aureus biofilm was observed after 24 h under flow dynamic conditions. Additionally, functionalized PDMS lessened cell adhesion upon direct contact, while supporting a cytocompatible profile, within an indirect assay. The adequacy of the biological response was further validated upon in vivo subcutaneous tissue implantation. An important step was taken towards biofunctional assessment of RLs-functionalized PDMS, reinforcing their suitability for medical device usage and infection prevention.

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  • 35.
    Das, Krishna Sundar
    et al.
    School of Chemical Sciences, Indian Association for the Cultivation of Science, Kolkata, India.
    Pal, Baishakhi
    Department of Physics, Jadavpur University, Jadavpur, Kolkata, India.
    Saha, Sayan
    School of Chemical Sciences, Indian Association for the Cultivation of Science, Kolkata, India.
    Akhtar, Sohel
    School of Chemical Sciences, Indian Association for the Cultivation of Science, Kolkata, India.
    De, Avik
    School of Chemical Sciences, Indian Association for the Cultivation of Science, Kolkata, India.
    Ray, Partha Pratim
    Department of Physics, Jadavpur University, Jadavpur, Kolkata, India.
    Mondal, Raju
    School of Chemical Sciences, Indian Association for the Cultivation of Science, Kolkata, India.
    Utilization of counter anions for charge transportation in the electrical device fabrication of Zn(ii) metal–organic frameworks2020In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 49, no 46, p. 17005-17016Article in journal (Refereed)
    Abstract [en]

    The present work reports the fabrication of anion-induced electrical devices with Zn(II) metal–organic frameworks. The essence of our electronic device fabrication is to utilize the anionic species entrapped inside of the three-dimensional network of the MOFs for charge transportation. The idea is to generate MOFs as a host–guest system with encapsulated anions or anion–solvent clusters as guests and a cationic yet insulating three-dimensional framework as the host. Accordingly, we have synthesized two Zn(II) MOFs using a neutral bispyrazole-based ligand, which results in a cationic chassis with substantial void space and porous channels inside the network. For both MOFs, the porous channels are occupied by infinitely hydrogen bonded networks of anions and anion–solvent clusters. This provides an excellent platform for anionic species-induced charge transportation and improved electrical conductivity. Indeed, the impedance spectroscopy data and current density–voltage (J–V) characteristics of the fabricated electrical devices further vindicate our idea. The current–voltage measurements clearly indicate the usefulness of modified host–guest-type MOFs for electronic device fabrication with corroborating conductivity values of 8.71 × 10−5 S m−1 and 5.79 × 10−4 S m−1 for compound 1 and compound 2, respectively.

  • 36.
    De, Avik
    et al.
    School of Chemical Sciences;Indian Association for the Cultivation of Science;Kolkata 700032;India.
    Bala, Sukhen
    Key Laboratory of Bioinorganic and Synthetic Chemistry of Ministry of Education;School of Chemistry;Sun Yat-Sen University;Guangzhou 510275;P. R. China.
    Saha, Sayan
    School of Chemical Sciences;Indian Association for the Cultivation of Science;Kolkata 700032;India.
    Das, Krishna Sundar
    School of Chemical Sciences;Indian Association for the Cultivation of Science;Kolkata 700032;India.
    Akhtar, Sohel
    School of Chemical Sciences;Indian Association for the Cultivation of Science;Kolkata 700032;India.
    Adhikary, Amit
    School of Chemical Sciences;Indian Association for the Cultivation of Science;Kolkata 700032;India.
    Ghosh, Arijit
    Laboratory of Molecular Biology;School of Biological Sciences;Indian Association for the Cultivation of Science;Kolkata 700032;India.
    Huang, Guo-Zhang
    Key Laboratory of Bioinorganic and Synthetic Chemistry of Ministry of Education;School of Chemistry;Sun Yat-Sen University;Guangzhou 510275;P. R. China.
    Chowdhuri, Srijita Paul
    Laboratory of Molecular Biology;School of Biological Sciences;Indian Association for the Cultivation of Science;Kolkata 700032;India.
    Das, Benu Brata
    Laboratory of Molecular Biology;School of Biological Sciences;Indian Association for the Cultivation of Science;Kolkata 700032;India.
    Tong, Ming-Liang
    Key Laboratory of Bioinorganic and Synthetic Chemistry of Ministry of Education;School of Chemistry;Sun Yat-Sen University;Guangzhou 510275;P. R. China.
    Mondal, Raju
    School of Chemical Sciences;Indian Association for the Cultivation of Science;Kolkata 700032;India.
    Lanthanide clusters of phenanthroline containing a pyridine–pyrazole based ligand: magnetism and cell imaging2021In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 50, no 10, p. 3593-3609Article in journal (Refereed)
    Abstract [en]

    In this contribution, we report the synthesis, characterization and luminescence-magnetic properties of Ln-clusters (Ln = Gd3+, Eu3+and Tb3+) using a new pyridine-pyrazole functionalized ligand fitted with a chromophoric phenanthroline backbone. The unorthodox N-rich ligand forms isostructural trinuclear lanthanide complexes with a topology that closely resembles two interdigitating hairpins. The clusters crystallize in chiral space groups and also exhibit chirality for bulk samples, which were further confirmed using solid state CD spectra. Magnetic studies on the complexes reveal their interesting features while the Gd cluster shows a significant cryogenic magnetic cooling behaviour with a moderately high magnetic entropy change of −23.42 J kg−1K−1at 7 T and 2 K. On the other hand, Eu and Tb complexes exhibit interesting fluorescence properties. The compounds were subsequently used as fluorescent probes for the imaging of human breast adenocarcinoma (MCF7) cells. Live cell confocal microscopy images show that the complexes penetrate beyond the usual cytoplasm region and can be useful in imaging the nucleus region of MCF7 cells.

  • 37.
    De, Avik
    et al.
    Department of Inorganic Chemistry, Indian Association for the Cultivation of Science, Kolkata, India.
    Mondal, Raju
    Department of Inorganic Chemistry, Indian Association for the Cultivation of Science, Kolkata, India.
    Toxic Metal Sequestration Exploiting a Unprecedented Low-Molecular-Weight Hydrogel-to-Metallogel Transformation2018In: ACS Omega, E-ISSN 2470-1343, Vol. 3, no 6, p. 6022-6030Article in journal (Refereed)
    Abstract [en]

    We report herein the development of a unique low-molecular-weight gelator-induced technique for environmental remediation. The motive of this work is wastewater purification using a gel-based toxic heavy metal sequestration. The essence of this technique was to bring two different functionalities, one capable of multiple coordination and another with gel-forming ability, arranged in tandem within a single ligand molecule. Naturally, the success of the approach depends on whether the two tandem-arrayed functionalities are indeed working in tandem. Our results show that the ligand molecule is an excellent example of concomitant hydrogelator and metallogelator. The most interesting aspects of this study involve the toxic metal sequestration of Pb, Cd, and Hg which was further studied in detail with spectroscopic, microscopic, and diffraction techniques. We also report here a rare property of pure organic hydrogel-to-metallogel transformation which could open up a new avenue on wastewater purification. In essence, the hydrogels can be envisaged as a unique class of metal-free zeolite analogue for environmental remediation not by just absorbance but through absorbance cum coordination, which are further corroborated by the inductively coupled plasma-optical emission spectroscopy results.

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  • 38.
    Ding, Pengjia
    et al.
    College of Environmental Science and Engineering, Hebei University of Science and Technology, Shijiazhuang, China; Institute for Ecological Research and Pollution Control of Plateau Lakes, School of Ecology and Environmental Science, Yunnan University, Kunming, China.
    Niu, Jianrui
    College of Environmental Science and Engineering, Hebei University of Science and Technology, Shijiazhuang, China.
    Chang, Fengqin
    Institute for Ecological Research and Pollution Control of Plateau Lakes, School of Ecology and Environmental Science, Yunnan University, Kunming, China.
    He, Zhuang
    College of Environmental Science and Engineering, Hebei University of Science and Technology, Shijiazhuang, China; Institute for Ecological Research and Pollution Control of Plateau Lakes, School of Ecology and Environmental Science, Yunnan University, Kunming, China.
    Wågberg, Thomas
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Li, Zaixing
    College of Environmental Science and Engineering, Hebei University of Science and Technology, Shijiazhuang, China.
    Hu, Guangzhi
    College of Environmental Science and Engineering, Hebei University of Science and Technology, Shijiazhuang, China; Institute for Ecological Research and Pollution Control of Plateau Lakes, School of Ecology and Environmental Science, Yunnan University, Kunming, China.
    NiCo2O4 hollow microsphere–mediated ultrafast peroxymonosulfate activation for dye degradation2021In: Chinese Chemical Letters, ISSN 1001-8417, E-ISSN 1878-5964, Vol. 32, no 8, p. 2495-2498Article in journal (Refereed)
    Abstract [en]

    Morphology and dispersity are key factors for activating peroxymonosulfate (PMS). In this study, we designed a recyclable open-type NiCo2O4 hollow microsphere via a simple hydrothermal method with the assistance of an NH3 vesicle. The physical structure and chemical properties were characterized using techniques such as scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD), N2 adsorption and X-ray photoelectron spectroscopy (XPS). The test results confirm that the inner and outer surfaces of open-type NiCo2O4 hollow-sphere can be efficiently utilized because of the hole on the surface of the catalyst, which can minimize the diffusion resistance of the reactants and products. Under optimized conditions, the total organic carbon (TOC) removal efficiency of rhodamine B (RhB) can reach up to 80% in 40 min, which is almost 50% shorter than the reported values. The reactive radicals were identified and the proposed reaction mechanism was well described. Moreover, the disturbances of HCO3, NO3, Cl and H2PO4 were further investigated. As a result, HCO3 and NO3 suppressed the reaction while Cl and H2PO4 had a double effect on reaction.

  • 39.
    dos Reis, Glaydson Simoes
    et al.
    Department of Forest Biomaterials and Technology, Biomass Technology Centre, Swedish University of Agricultural Sciences, Umeå, Sweden.
    de Oliveira, Helinando Pequeno
    Institute of Materials Science, Federal University of Sao Francisco Valley, Petrolina, Brazil.
    Candido, Iuri Custodio Montes
    Institute of Materials Science, Federal University of Sao Francisco Valley, Petrolina, Brazil.
    Freire, Andre Luiz
    Institute of Materials Science, Federal University of Sao Francisco Valley, Petrolina, Brazil.
    Molaiyan, Palanivel
    Research Unit of Sustainable Chemistry, University of Oulu, Oulu, Finland.
    Dotto, Guilherme Luiz
    Research Group On Adsorptive and Catalytic Process Engineering (ENGEPAC), Federal University of Santa Maria, Av. Roraima, 1000-7, RS, Santa Maria, Brazil.
    Grimm, Alejandro
    Department of Forest Biomaterials and Technology, Biomass Technology Centre, Swedish University of Agricultural Sciences, Umeå, Sweden.
    Mikkola, Jyri-Pekka
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Industrial Chemistry and Reaction Engineering, Johan Gadolin Process Chemistry Centre, Åbo Akademi University, Åbo-Turku, Finland.
    Supercapacitors and triboelectric nanogenerators based on electrodes of greener iron nanoparticles/carbon nanotubes composites2024In: Scientific Reports, E-ISSN 2045-2322, Vol. 14, no 1, article id 11555Article in journal (Refereed)
    Abstract [en]

    The development of supporting materials based on carbon nanotubes (CNTs) impregnated with iron nanoparticles via a sustainable and green synthesis employing plant extract of Punica granatum L. leaves was carried out for the iron nanoparticle modification and the following impregnation into the carbon nanotubes composites (CNT-Fe) that were also coated with polypyrrole (CNT-Fe + PPy) for use as electrode for supercapacitor and triboelectric nanogenerators. The electrochemical characterization of the materials by cyclic voltammetry (CV) and galvanostatic charge–discharge (GCD) assays revealed that the CNT-Fe + PPy gave rise to better performance due to the association of double-layer capacitance behavior of carbon derivative in association with the pseudocapacitance contribution of PPy resulting in an areal capacitance value 202 mF/ cm2 for the overall composite. In terms of the application of electrodes in triboelectric nanogenerators, the best performance for the composite of CNT-Fe + PPy was 60 V for output voltage and power density of 6 μW/cm2. The integrated system showed that the supercapacitors can be charged directly by the nanogenerator from 0 to 42 mV in 300 s. The successful green synthesis of iron nanoparticles on CNT and further PPy coating provides a feasible method for the design and synthesis of high-performance SCs and TENGs electrode materials. This work provides a systematic approach that moves the research front forward by generating data that underpins further research in self-powered electronic devices.

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  • 40.
    dos Reis, Glaydson Simões
    et al.
    Department of Forest Biomaterials and Technology, Swedish University of Agricultural Sciences, Biomass Technology Centre, Umeå, Sweden.
    Pinheiro Lima, Ravi Moreno A.
    Institute of Materials Science, Universidade Federal do Vale do São Francisco, Avenida Antônio Carlos Magalhães, 510, Santo Antônio, BA, Juazeiro, Brazil.
    Larsson, Sylvia H.
    Department of Forest Biomaterials and Technology, Swedish University of Agricultural Sciences, Biomass Technology Centre, Umeå, Sweden.
    Subramaniyam, Chandrasekar Mayandi
    Chemistry and Biochemistry Dpto., Facultad de Farmacia, Universidad San Pablo-CEU, CEU Universities, Boadilla del Monte, Madrid, Spain.
    Dinh, Van Minh
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Thyrel, Mikael
    Department of Forest Biomaterials and Technology, Swedish University of Agricultural Sciences, Biomass Technology Centre, Umeå, Sweden.
    de Oliveira, Helinando Pequeno
    Institute of Materials Science, Universidade Federal do Vale do São Francisco, Avenida Antônio Carlos Magalhães, 510, Santo Antônio, BA, Juazeiro, Brazil.
    Flexible supercapacitors of biomass-based activated carbon-polypyrrole on eggshell membranes2021In: Journal of Environmental Chemical Engineering, E-ISSN 2213-3437, Vol. 9, no 5, article id 106155Article in journal (Refereed)
    Abstract [en]

    The quest to develop flexible membrane-like supercapacitors to be applied in advanced electronic devices with a flexible structure is important for the modern world. In this study, we developed biomass-based supercapacitors by depositing activated carbon on an eggshell membrane and subsequently coating these with polypyrrole in a two-step procedure. The competition between the electrical double layer capacitance (EDLC) from activated carbon and the pseudocapacitance (PC) for the hybrid device is controlled by varying the amount of polypyrrole (PC component) in a time-dependent polymerization process. An areal capacitance of 172.5 mF cm−2, a corresponding energy density of 4.73 W h kg−1, and power density of 320.8 W kg−1, with a 60% retention even after 1000 cycles were obtained for samples prepared with the polymerization of polypyrrole on the activated carbon (incorporation of an active layer of 3.18 mg cm−2).

  • 41.
    dos Santos, John Marques
    et al.
    Organic Semiconductor Centre, EaStCHEM School of Chemistry, University of St Andrews, St Andrews, United Kingdom.
    Chan, Chin-Yiu
    Center for Organic Photonics and Electronics Research (OPERA), Kyushu University, Motooka 744, Fukuoka, Nishi-ku, Japan.
    Tang, Shi
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Hall, David
    Organic Semiconductor Centre, EaStCHEM School of Chemistry, University of St Andrews, St Andrews, United Kingdom; Laboratory for Computational Modeling of Functional Materials, Namur Institute of Structured Matter, University of Namur, 61 Rue de Bruxelles, Namur, Belgium.
    Matulaitis, Tomas
    Organic Semiconductor Centre, EaStCHEM School of Chemistry, University of St Andrews, St Andrews, United Kingdom.
    Cordes, David B.
    Organic Semiconductor Centre, EaStCHEM School of Chemistry, University of St Andrews, St Andrews, United Kingdom.
    Slawin, Alexandra M. Z.
    Organic Semiconductor Centre, EaStCHEM School of Chemistry, University of St Andrews, St Andrews, United Kingdom.
    Tsuchiya, Youichi
    Center for Organic Photonics and Electronics Research (OPERA), Kyushu University, Motooka 744, Fukuoka, Nishi-ku, Japan.
    Edman, Ludvig
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Adachi, Chihaya
    Center for Organic Photonics and Electronics Research (OPERA), Kyushu University, Motooka 744, Fukuoka, Nishi-ku, Japan.
    Olivier, Yoann
    Laboratory for Computational Modeling of Functional Materials, Namur Institute of Structured Matter, University of Namur, 61 Rue de Bruxelles, Namur, Belgium.
    Zysman-Colman, Eli
    Organic Semiconductor Centre, EaStCHEM School of Chemistry, University of St Andrews, St Andrews, United Kingdom.
    Color tuning of multi-resonant thermally activated delayed fluorescence emitters based on fully fused polycyclic amine/carbonyl frameworks2023In: Journal of Materials Chemistry C, ISSN 2050-7526, E-ISSN 2050-7534, Vol. 11, no 24, p. 8263-8273Article in journal (Refereed)
    Abstract [en]

    Two novel π-extended amine/carbonyl-based multi-resonance thermally activated delayed fluorescence (MR-TADF) emitters have been designed and synthesized. The two emitters are isomeric, composed of nine fused rings and show green-yellow emission. Sym-DiDiKTa and Asym-DiDiKTa possess tert-butyl groups distributed in a symmetrical and asymmetrical fashion, respectively, which significantly impact the single-crystal packing structure. The two compounds possess similar singlet-triplet energy gaps, ΔEST, of around 0.23 eV, narrowband emission characterized by a full-width at half-maximum, FWHM, of 29 nm and a photoluminescence quantum yield, ΦPL, of 70% and 53% for the symmetric and asymmetric counterparts, respectively, in toluene. Investigation in OLEDs demonstrated that the devices with Sym-DiDiKTa and Asym-DiDiKTa displayed electroluminescence maxima of 543 and 544 nm, and maximum external quantum efficiencies (EQEmax) of 9.8% and 10.5%, respectively. The maximum EQE was further improved to 19.9% by employing a hyperfluorescence strategy. We further present the first example of a neutral MR-TADF emitter incorporated in a LEC device where Sym-DiDiKTa acts as the emitter. The LEC shows a λEL at 551 nm and FWHM of 60 nm with luminance of 300 cd m−2 and a fast turn-on time of less than 2 s to 100 cd m−2

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  • 42. Du, Hao
    et al.
    Kang, Yuqiong
    Li, Chenglei
    Zhao, Yun
    Tian, Yao
    Lu, Jian
    Chen, Zhaoyang
    Gao, Ning
    Li, Zhike
    Wozny, John
    Li, Tao
    Wang, Li
    Tavajohi Hassan Kiadeh, Naser
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Kang, Feiyu
    Li, Baohua
    Recovery of lithium salt from spent lithium-ion battery by less polar solvent wash and water extraction2023In: Carbon Neutralization, ISSN 2769-3325, Vol. 2, no 4, p. 416-424Article in journal (Refereed)
    Abstract [en]

    The lithium hexafluorophosphate (LiPF6) in spent lithium-ion batteries (LIBs) is a potentially valuable resource and a significant environmental pollutant. Unfortunately, most of the LiPF6 in a spent LIB is difficult to extract because the electrolyte is strongly adsorbed by the cathode, anode, and separator. Storing extracted electrolyte is also challenging because it contains LiPF6, which promotes the decomposition of the solvent. Here we show that electrolytes in spent LIBs can be collected by a less polar solvent dimethyl carbonate (DMC) wash, and LiPF6 can be concentrated by simple aqueous extraction by lowering ethylene carbonate (EC) content in the recycled electrolyte. Due to the similar dielectric constant of EC and water, reducing the content of EC in LIB electrolytes, or even eliminating it, facilitates the separation of water and electrolyte, thus enabling the lithium salts in the electrolyte to be separated from the organic solvent. The lithium salt extracting efficiency achieved in this way can be as high as 99.8%, and fluorine and phosphorus of LiPF6 can be fixed in the form of stable metal fluoride and phosphate by hydrothermal method. The same strategy can be used in industrial waste electrolyte recycling by diluting the waste with DMC and extracting the resulting solution with water. This work thus reveals a new route for waste electrolyte treatment and will also support the development of advanced EC-free electrolytes for high-performance, safe, and easily recyclable LIBs.

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  • 43.
    Du, Hao
    et al.
    Institute of Materials Research, Tsinghua Shenzhen International Graduate School, Tsinghua University, Shenzhen, China.
    Kang, Yuqiong
    Institute of Materials Research, Tsinghua Shenzhen International Graduate School, Tsinghua University, Shenzhen, China.
    Li, Chenglei
    Institute of Materials Research, Tsinghua Shenzhen International Graduate School, Tsinghua University, Shenzhen, China.
    Zhao, Yun
    Institute of Materials Research, Tsinghua Shenzhen International Graduate School, Tsinghua University, Shenzhen, China.
    Wozny, John
    Department of Chemistry and Biochemistry, Northern Illinois University, DeKalb, Illinois, USA.
    Li, Tao
    Department of Chemistry and Biochemistry, Northern Illinois University, DeKalb, Illinois, USA.
    Tian, Yao
    Institute of Materials Research, Tsinghua Shenzhen International Graduate School, Tsinghua University, Shenzhen, China.
    Lu, Jian
    Institute of Materials Research, Tsinghua Shenzhen International Graduate School, Tsinghua University, Shenzhen, China.
    Wang, Li
    Institute of Nuclear and New Energy Technology, Tsinghua University, Beijing, China.
    Kang, Feiyu
    Institute of Materials Research, Tsinghua Shenzhen International Graduate School, Tsinghua University, Shenzhen, China.
    Tavajohi Hassan Kiadeh, Naser
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Li, Baohua
    Institute of Materials Research, Tsinghua Shenzhen International Graduate School, Tsinghua University, Shenzhen, China.
    Easily recyclable lithium-ion batteries: Recycling-oriented cathode design using highly soluble LiFeMnPO4 with a water-soluble binder2023In: Battery Energy, ISSN 2768-1688, Vol. 2, no 4, p. 1-9, article id 20230011Article in journal (Refereed)
    Abstract [en]

    Recycling lithium-ion batteries (LIBs) is fundamental for resource recovery, reducing energy consumption, decreasing emissions, and minimizing environmental risks. The inherited properties of materials and design are not commonly attributed to the complexity of recycling LIBs and their effects on the recycling process. The state-of-the-art battery recycling methodology consequently suffers from poor recycling efficiency and high consumption from issues with the cathode and the binder material. As a feasibility study, high-energy-density cathode material LiFeMnPO4 with a water-soluble polyacrylic acid (PAA) binder is extracted with dilute hydrochloric acid at room temperature under oxidant-free conditions. The cathode is wholly leached with high purity and is suitable for reuse. The cathode is easily separated from its constituent materials and reduces material and energy consumption during recycling by 20% and 7%, respectively. This strategy is utilized to fabricate recyclable-oriented LiFeMnPO4/graphite LIBs with a PAA binder and carbon paper current collector. Finally, the limitation of the solubility of the binder is discussed in terms of recycling. This research hopefully provides guidance for recycling-oriented design for the circular economy of the LIB industry.

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  • 44.
    Du, Hao
    et al.
    Institute of Materials Research, Tsinghua Shenzhen International Graduate School, Tsinghua University, Shenzhen, 518055 China.
    Wang, Yadong
    Institute of Materials Research, Tsinghua Shenzhen International Graduate School, Tsinghua University, Shenzhen, 518055 China.
    Kang, Yuqiong
    Institute of Materials Research, Tsinghua Shenzhen International Graduate School, Tsinghua University, Shenzhen, 518055 China.
    Zhao, Yun
    Institute of Materials Research, Tsinghua Shenzhen International Graduate School, Tsinghua University, Shenzhen, 518055 China.
    Tian, Yao
    Institute of Materials Research, Tsinghua Shenzhen International Graduate School, Tsinghua University, Shenzhen, 518055 China.
    Wang, Xianshu
    National and Local Joint Engineering Research Center of Lithium-ion Batteries and Materials Preparation Technology, Key Laboratory of Advanced Battery Materials of Yunnan Province, Faculty of Metallurgical and Energy Engineering, Kunming University of Science and Technology, Kunming, 650093 P. R. China.
    Tan, Yihong
    School of Chemistry and Chemical Engineering, Frontiers Science Center for Transformative Molecules, Shanghai Jiao Tong University, Shanghai, 200240 China.
    Liang, Zheng
    School of Chemistry and Chemical Engineering, Frontiers Science Center for Transformative Molecules, Shanghai Jiao Tong University, Shanghai, 200240 China.
    Wozny, John
    Department of Chemistry and Biochemistry, Northern Illinois University, DeKalb, IL, 60115 USA.
    Li, Tao
    Department of Chemistry and Biochemistry, Northern Illinois University, DeKalb, IL, 60115 USA.
    Ren, Dongsheng
    Institute of Nuclear & New Energy Technology, Tsinghua University, Beijing, 100084 China.
    Wang, Li
    Institute of Nuclear & New Energy Technology, Tsinghua University, Beijing, 100084 China.
    He, Xiangming
    Institute of Nuclear & New Energy Technology, Tsinghua University, Beijing, 100084 China.
    Xiao, Peitao
    College of Aerospace Science and Engineering, National University of Defense Technology, Changsha, 410073 China.
    Mao, Eryang
    State Key Laboratory of Catalysis, Dalian National Laboratory for Clean Energy, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, 116023 China.
    Tavajohi, Naser
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Kang, Feiyu
    Institute of Materials Research, Tsinghua Shenzhen International Graduate School, Tsinghua University, Shenzhen, 518055 China.
    Li, Baohua
    Institute of Materials Research, Tsinghua Shenzhen International Graduate School, Tsinghua University, Shenzhen, 518055 China.
    Side reactions/changes in lithium-ion batteries: mechanisms and strategies for creating safer and better batteries2024In: Advanced Materials, ISSN 0935-9648, E-ISSN 1521-4095Article, review/survey (Refereed)
    Abstract [en]

    Abstract Lithium-ion batteries (LIBs), in which lithium ions function as charge carriers, are considered the most competitive energy storage devices due to their high energy and power density. However, battery materials, especially with high capacity undergo side reactions and changes that result in capacity decay and safety issues. A deep understanding of the reactions that cause changes in the battery's internal components and the mechanisms of those reactions is needed to build safer and better batteries. This review focuses on the processes of battery failures, with voltage and temperature as the underlying factors. Voltage-induced failures result from anode interfacial reactions, current collector corrosion, cathode interfacial reactions, overcharge, and overdischarge, while temperature-induced failure mechanisms include SEI decomposition, separator damage, and interfacial reactions between electrodes and electrolytes. The review also presents protective strategies for controlling these reactions. As a result, the reader is offered a comprehensive overview of the safety features and failure mechanisms of various LIB components. 

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  • 45. Durgadevi, Ganesan
    et al.
    Samikannu, Ajaikumar
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Chandran, Muthaiah
    Kuppusamy, Muniyan Ramasamy
    Dinakaran, Kannaiyan
    Synthesis and characterization of CdS nanoparticle anchored Silica-Titania mixed Oxide mesoporous particles: Efficient photocatalyst for discoloration of textile effluent2019In: International Journal of Nano Dimension, ISSN 2008-8868, E-ISSN 2228-5059, Vol. 10, no 3, p. 272-280Article in journal (Refereed)
    Abstract [en]

    An efficient photocatalyst consisting of CdS nanoparticle dispersed mesoporous silica-titania was prepared using amphiphilic triblock copolymer P123 as template and silica-titania sol-gel precursors. The CdS nanoparticle was incorporated into silica-titania mesoporous nanosturctures by post impregnation method. The synthesized catalyst has been characterized by FTIR, TEM, SEM, and EDAX analysis. The CdS nanoparticles incorporated silica-titania mesoporous particles exhibited an enhanced light harvesting, large surface area and excellent photocatalytic activity. Photocatalytic degradation experiments on methyleneblue solution at different pH of the medium revealed that, the catalyst ST0.5CdS0.2 is more effective in basic medium with a degradation efficiency of 98%. In addition, the catalyst is also tested for dye degradation against a raw textile dye effluent containing multiple dye molecules, and their results indicated that the raw effluent can be decolorized within 90min using ST0.5CdS0.2 catalyst.

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  • 46. Dyson, P J
    et al.
    Laurenczy, G
    Ohlin, C A
    Vallance, J
    Welton, T
    Determination of hydrogen concentration in ionic liquids and the effect (or lack of) on rates of hydrogenation2003In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, no 19, p. 2418-2419Article in journal (Refereed)
    Abstract [en]

    The solubility of hydrogen and the corresponding Henry coefficients for 11 ionic liquids have been determined in situ at 100 atm H(2) pressure and are much lower than expected; attempts to correlate the solubility of hydrogen in the ionic liquids with the rate of reaction for the hydrogenation of benzene to cyclohexane in these solvents have been made.

  • 47.
    Ekeroth, Sebastian
    et al.
    Department of Physics, Chemistry and Biology, Linköping University, Linköping, Sweden.
    Ekspong, Joakim
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Perivoliotis, Dimitrios K.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Sharma, Sachin
    Department of Physics, Chemistry and Biology, Linköping University, Linköping, Sweden.
    Boyd, Robert
    Department of Physics, Chemistry and Biology, Linköping University, Linköping, Sweden.
    Brenning, Nils
    Department of Physics, Chemistry and Biology, Linköping University, Linköping, Sweden; Division of Space and Plasma Physics, School of Electrical Engineering, KTH Royal Institute of Technology, Stockholm, Sweden.
    Gracia-Espino, Eduardo
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Edman, Ludvig
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Helmersson, Ulf
    Department of Physics, Chemistry and Biology, Linköping University, Linköping, Sweden.
    Wågberg, Thomas
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Magnetically Collected Platinum/Nickel Alloy Nanoparticles as Catalysts for Hydrogen Evolution2021In: ACS Applied Nano Materials, E-ISSN 2574-0970, Vol. 4, no 12, p. 12957-12965Article in journal (Refereed)
    Abstract [en]

    The hydrogen evolution reaction (HER) is a key process in electrochemical water splitting. To lower the cost and environmental impact of this process, it is highly motivated to develop electrocatalysts with low or no content of noble metals. Here, we report on an ingenious synthesis of hybrid PtxNi1-x electrocatalysts in the form of a nanoparticle-nanonetwork structure with very low noble metal content. The structure possesses important features such as good electrical conductivity, high surface area, strong interlinking, and substrate adhesion, which render an excellent HER activity. Specifically, the best performing Pt0.05Ni0.95 sample demonstrates a Tafel slope of 30 mV dec-1 in 0.5 M H2SO4 and an overpotential of 20 mV at a current density of 10 mA cm-2 with high stability. The impressive catalytic performance is further rationalized in a theoretical study, which provides insight into the mechanism on how such small platinum content can allow for close-to-optimal adsorption energies for hydrogen.

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  • 48.
    Ekspong, Joakim
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Gracia-Espino, Eduardo
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Theoretical Analysis of Surface Active Sites in Defective 2H and 1T ' MoS2 Polymorphs for Hydrogen Evolution Reaction: Quantifying the Total Activity of Point Defects2020In: Advanced Theory and Simulations, E-ISSN 2513-0390, Vol. 3, no 3, article id 1900213Article in journal (Refereed)
    Abstract [en]

    Defect engineering is a common and promising strategy to improve the catalytic activity of layered structures such as MoS2, where in particular the 2H and 1T ' polymorphs have been under intense study for their activity toward the hydrogen evolution reaction. However, the large variety of defects, each with its own distinct and usually unknown effects, complicates the design and optimization of such defective materials. Therefore, it is relevant to characterize in detail the effect of individual defects and to be able to combine these observations to describe more complex materials, such as those seen experimentally. Therefore, nine point defects (antisites defects and vacancies) are theoretically studied on single layer 1T, 1T ', and 2H MoS2 polymorphs, and the variation and spatial distribution in the active sites are identified. It is found that all defective 1T ' monolayers exhibit an increase in the exchange current density of at least 2.3 times when compared to pristine 1T ' MoS2, even if a reduced number of active sites are observed. The results are later used to propose a methodology to study materials containing a mixture of crystal phases, or other alterations that cause inhomogeneous changes in the activity of catalytic sites.

  • 49.
    Elbashir, Sana
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Broström, Markus
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Skoglund, Nils
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Thermodynamic modelling assisted three-stage solid state synthesis of high purity β-Ca3(PO4)22024In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 238, article id 112679Article in journal (Refereed)
    Abstract [en]

    A three-stage solid state synthesis assisted by thermodynamic modelling was developed to prepare highly pure (>99 %) beta tricalcium phosphate (β-TCP) powder. The optimal synthesis temperature was experimentally determined to be 1000 °C in good agreement with the theoretical calculations. The synthesis design described here has substantially improved the product quality and eliminated the presence of secondary phosphate phases compared to one- and two-stage methods investigated in this work. A comprehensive characterization of the material's structural, vibrational, and morphological characteristics was conducted. Rietveld refinement of the X-ray diffraction data confirmed the high purity of the samples. The crystal structure of the prepared β-TCP was determined and the refined unit cell parameters agreed well with the reference values. From infrared and Raman spectral analyses, the characteristics of β-TCP were observed and discussed in details. Furthermore, the morphology and elemental composition of the products were examined and found to be homogenous and impurity free. The reproducibility of the material was scrutinized and showed no significant data variations. Using our three-stage synthesis method, it is possible to produce β-TCP powder of high purity with consistent repeatability.

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  • 50.
    Elhaj, Ahmed
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Porous Polymeric Monoliths by Less Common Pathways: Preparation and Characterization2014Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis focuses on my endeavors to prepare new porous polymeric monoliths that are viable to use as supports in flow-through processes. Polymer monoliths of various porous properties and different chemical properties have been prepared utilizing the thermally induced phase separation (TIPS) phenomenon and step-growth polymerization reactions. The aim has been to find appropriate synthesis routes to produce separation supports with fully controlled chemical, physical and surface properties. This thesis includes preparation of porous monolithic materials from several non-cross-linked commodity polymers and engineering plastics by dissolution/precipitation process (i.e. TIPS). Elevated temperatures, above the upper critical solution temperature (UCST), were used to dissolve the polymers in appropriate solvents that only dissolve the polymers above this critical temperature. After dissolution, the homogeneous and clear polymer-solvent solution is thermally quenched by cooling. A porous material, of three dimensional structure, is then obtained as the temperature crosses the UCST. More than 20 organic solvents were tested to find the most compatible one that can dissolve the polymer above the UCST and precipitate it back when the temperature is lowered. The effect of using a mixture of two solvents or additives (co-porogenic polymer or surfactant) in the polymer dissolution/precipitation process have been studied more in depth for poly(vinylidine difluoride) (PVDF) polymers of two different molecular weight grades. Monolithic materials showing different pore characteristics could be obtained by varying the composition of the PVDF-solvent mixture during the dissolute­ion/precipitation process. Step-growth polymerization (often called polycondensat­ion reaction) combined with sol-gel process with the aid of porogenic polymer and block copolymer surfactant have also been used as a new route of synthesis for production of porous melamine-formaldehyde (MF) monoliths. In general, the meso- and macro-porous support materials, for which the synthesis/preparation is discussed in this thesis, are useful to a wide variety of applications in separation science and heterogeneous reactions (catalysis).

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