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  • 1.
    Abreu, Barbara
    et al.
    Univ Porto, Fac Sci, Dept Chem & Biochem, CIQUP, Rua Campo Alegre, P-4169007 Porto, Portugal..
    Rocha, Jessica
    Univ Porto, Fac Sci, Dept Chem & Biochem, CIQUP, Rua Campo Alegre, P-4169007 Porto, Portugal..
    Ferreira Fernandes, Ricardo Manuel
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Regev, Oren
    Ben Gurion Univ Negev, Dept Chem Engn, IL-84105 Beer Sheva, Israel.;Ben Gurion Univ Negev, Ilse Katz Inst Nanotechnol, IL-84105 Beer Sheva, Israel..
    Furo, Istvan
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Marques, Eduardo F.
    Univ Porto, Fac Sci, Dept Chem & Biochem, CIQUP, Rua Campo Alegre, P-4169007 Porto, Portugal..
    Gemini surfactants as efficient dispersants of multiwalled carbon nanotubes: Interplay of molecular parameters on nanotube dispersibility and debundling2019In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 547, p. 69-77Article in journal (Refereed)
    Abstract [en]

    Surfactants have been widely employed to debundle, disperse and stabilize carbon nanotubes in aqueous solvents. Yet, a thorough understanding of the dispersing mechanisms at molecular level is still warranted. Herein, we investigated the influence of the molecular structure of gemini surfactants on the dispersibility of multiwalled carbon nanotubes (MWNTs). We used dicationic n-s-n gemini surfactants, varying n and s, the number of alkyl tail and alkyl spacer carbons, respectively; for comparisons, single-tailed surfactant homologues were also studied. Detailed curves of dispersed MWNT concentration vs. surfactant concentration were obtained through a stringently controlled experimental procedure, allowing for molecular insight. The gemini are found to be much more efficient dispersants than their single-tailed homologues, i.e. lower surfactant concentration is needed to attain the maximum dispersed MWNT concentration. In general, the spacer length has a comparatively higher influence on the dispersing efficiency than the tail length. Further, scanning electron microscopy imaging shows a sizeable degree of MWNT debundling by the gemini surfactants in the obtained dispersions. Our observations also point to an adsorption process that does not entail the formation of micelle-like aggregates on the nanotube surface, but rather coverage by individual molecules, among which the ones that seem to be able to adapt best to the nanotube surface provide the highest efficiency. These studies are relevant for the rational design and choice of optimal dispersants for carbon nanomaterials and other similarly water-insoluble materials.

  • 2.
    Adhikari, Arindam
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Claesson, Per M.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Pani, Jinshan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Corrosion Science.
    Leygraf, Christofer
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Corrosion Science.
    Deidinaitei, Andra
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Blomberg, Eva
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Electrochemical behavior and anticorrosion properties of modified polyaniline dispersed in polyvinylacetate coating on carbon steel2008In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 53, no 12, p. 4239-4247Article in journal (Refereed)
    Abstract [en]

    Conducting polyaniline (Pani) was prepared in the presence of methane sulfonic acid (MeSA) as dopant by chemical oxidative polymerization. The Pani-MeSA polymer was characterized by FT-IR, UV-vis, X-ray diffraction (XRD) and impedance spectroscopy. The polyrner was dispersed in polyvinylacetate and coated oil carbon steel samples by a dipping method. The electrochemical behavior and anticorrosion properties of the coating, oil carbon steel in 3% NaCl were investigated using Open-circuit Potential (OCP) versus time of exposure, and electrochemical techniques including electrochemical impedance spectroscopy (EIS), potentiodynamic polarization and cyclic voltammetry (CV). During initial exposure, the OCP dropped about 0.35 V and the interfacial resistance increased several times, indicating I certain reduction of the polymer and oxidation of the steel surface. Later the OCP shifted to the noble direction and remained at a stable value during the exposure up to 60 days. The EIS monitoring also revealed the initial change and later stabilization of the coating. The stable high OCP and low coating impedance Suggest that the conducting polymer maintains its oxidative state and provides corrosion protection for carbon steel through out the investigated period. The polarization curves and CV show that the conducting polymer coating induces a passive-like behavior and greatly reduces the corrosion of carbon steel.

  • 3.
    Adolfsson, Karin H.
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymer Technology.
    Huang, Ping
    Department of Chemistry – Ångström Laboratory, Uppsala University, Box 523, Uppsala, 751 20, Sweden, Box 523.
    Golda-Cepa, Monika
    Faculty of Chemistry, Jagiellonian Universityul, Krakow, 30–387, Poland.
    Xu, Huan
    School of Materials Science and Physics, China University of Mining and Technology, Xuzhou, 221116, P. R. China.
    Kotarba, Andrzej
    Faculty of Chemistry, Jagiellonian Universityul, Krakow, 30–387, Poland.
    Hakkarainen, Minna
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymer Technology.
    Scavenging of DPPH by Persistent Free Radicals in Carbonized Particles2023In: Advanced Sustainable Systems, E-ISSN 2366-7486, Vol. 7, no 3, article id 2200425Article in journal (Refereed)
    Abstract [en]

    Persistent free radicals (PFR) in carbonized particles may play a role in degradation of environmental compounds. The influence of PFR is evaluated in various carbonized particles on their radical scavenging efficiency upon the common radical indicator 2-2-diphenyl-1-picrylhydrazyl (DPPH). Carbonized particles are derived by hydrothermal carbonization of glucose (C-W) or glucose and urea (NC-W) and ionothermal carbonization of glucose and urea ionic liquid (IL) (NC-IL). The carbonized materials contain OH/COOH, C=C, and C-O functionalities. The addition of urea introduces NH/NH2 functionalities. The content of polar surface groups is lower in IL-processed NC-IL. The scavenging ability, measured as DPPH UV–vis absorption decline, increases with concentration and time for all particles, while the efficiency changes are in the order of C-W > NC-W > NC-IL. Electron paramagnetic resonance analysis reveals similar radical concentration in all carbonized materials studied. The difference in efficiency is, thus, not directly related to the PFR concentration but rather to the type of PFR, surface functionalities and/or scavenging mechanism. According to the g-values, radicals in these particles are carbon-centered. The minor variation in g-values suggests interactions between the radicals and their environmental functional groups. This provides insights into the influence of PFR in carbonized materials on their radical scavenging efficiency.

  • 4.
    Agustin, Melissa B.
    et al.
    VTT Technical Research Centre of Finland Ltd., P.O. Box 1000, FI-02044 VTT, Finland, P.O. Box 1000; Department of Food and Nutrition, Faculty of Agriculture and Forestry, University of Helsinki, P.O. Box 66, FI-00014, Helsinki, Finland, P.O. Box 66.
    Lahtinen, Maarit H.
    Department of Food and Nutrition, Faculty of Agriculture and Forestry, University of Helsinki, P.O. Box 66, FI-00014, Helsinki, Finland, P.O. Box 66.
    Kemell, Marianna
    Department of Chemistry, Faculty of Science, University of Helsinki, P.O. Box 55, FI-00014, Helsinki, Finland, P.O. Box 55.
    Oliaei, Erfan
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Biocomposites. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Mikkonen, Kirsi S.
    Department of Food and Nutrition, Faculty of Agriculture and Forestry, University of Helsinki, P.O. Box 66, FI-00014, Helsinki, Finland, P.O. Box 66; Helsinki Institute of Sustainability Science, University of Helsinki, P.O. Box 65, FI-00014, Helsinki, Finland, P.O. Box 65.
    Grönqvist, Stina
    VTT Technical Research Centre of Finland Ltd., P.O. Box 1000, FI-02044 VTT, Finland, P.O. Box 1000.
    Lehtonen, Mari
    Department of Food and Nutrition, Faculty of Agriculture and Forestry, University of Helsinki, P.O. Box 66, FI-00014, Helsinki, Finland, P.O. Box 66.
    Enzymatic crosslinking of lignin nanoparticles and nanocellulose in cryogels improves adsorption of pharmaceutical pollutants2024In: International Journal of Biological Macromolecules, ISSN 0141-8130, E-ISSN 1879-0003, Vol. 266, article id 131168Article in journal (Refereed)
    Abstract [en]

    Pharmaceuticals, designed for treating diseases, ironically endanger humans and aquatic ecosystems as pollutants. Adsorption-based wastewater treatment could address this problem, however, creating efficient adsorbents remains a challenge. Recent efforts have shifted towards sustainable bio-based adsorbents. Here, cryogels from lignin-containing cellulose nanofibrils (LCNF) and lignin nanoparticles (LNPs) were explored as pharmaceuticals adsorbents. An enzyme-based approach using laccase was used for crosslinking instead of fossil-based chemical modification. The impact of laccase treatment on LNPs alone produced surface-crosslinked water-insoluble LNPs with preserved morphology and a hemicellulose-rich, water-soluble LNP fraction. The water-insoluble LNPs displayed a significant increase in adsorption capacity, up to 140 % and 400 % for neutral and cationic drugs, respectively. The crosslinked cryogel prepared by one-pot incubation of LNPs, LCNF and laccase showed significantly higher adsorption capacities for various pharmaceuticals in a multi-component system than pure LCNF or unmodified cryogels. The crosslinking minimized the leaching of LNPs in water, signifying enhanced binding between LNPs and LCNF. In real wastewater, the laccase-modified cryogel displayed 8–44 % removal for cationic pharmaceuticals. Overall, laccase treatment facilitated the production of bio-based adsorbents by improving the deposition of LNPs to LCNF. Finally, this work introduces a sustainable approach for engineering adsorbents, while aligning with global sustainability goals.

  • 5.
    Agustin, Melissa B.
    et al.
    Univ Helsinki, Fac Agr & Forestry, Dept Food & Nutr, POB 66, FI-00014 Helsinki, Finland..
    Lehtonen, Mari
    Univ Helsinki, Fac Agr & Forestry, Dept Food & Nutr, POB 66, FI-00014 Helsinki, Finland..
    Kemell, Marianna
    Univ Helsinki, Fac Sci, Dept Chem, POB 55, FI-00014 Helsinki, Finland..
    Lahtinen, Panu
    VTT Tech Res Ctr Finland, POB 1000, FIN-02044 Espoo, Finland..
    Oliaei, Erfan
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Mikkonen, Kirsi S.
    Univ Helsinki, Fac Agr & Forestry, Dept Food & Nutr, POB 66, FI-00014 Helsinki, Finland.;Univ Helsinki, Helsinki Inst Sustainabil Sci, POB 65, FI-00014 Helsinki, Finland..
    Lignin nanoparticle-decorated nanocellulose cryogels as adsorbents for pharmaceutical pollutants2023In: Journal of Environmental Management, ISSN 0301-4797, E-ISSN 1095-8630, Vol. 330, article id 117210Article in journal (Refereed)
    Abstract [en]

    Adsorption is a relatively simple wastewater treatment method that has the potential to mitigate the impacts of pharmaceutical pollution. This requires the development of reusable adsorbents that can simultaneously remove pharmaceuticals of varying chemical structure and properties. Here, the adsorption potential of nanostructured wood-based adsorbents towards different pharmaceuticals in a multi-component system was investigated. The adsorbents in the form of macroporous cryogels were prepared by anchoring lignin nanoparticles (LNPs) to the nanocellulose network via electrostatic attraction. The naturally anionic LNPs were anchored to cationic cellulose nanofibrils (cCNF) and the cationic LNPs (cLNPs) were combined with anionic TEMPO-oxidized CNF (TCNF), producing two sets of nanocellulose-based cryogels that also differed in their overall surface charge density. The cryogels, prepared by freeze-drying, showed layered cellulosic sheets randomly decorated with spherical lignin on the surface. They exhibited varying selectivity and efficiency in removing pharmaceuticals with differing aromaticity, polarity and ionic characters. Their adsorption potential was also affected by the type (unmodified or cationic), amount and morphology of the lignin nanomaterials, as well as the pH of the pharmaceutical solution. Overall, the findings revealed that LNPs or cLNPs can act as functionalizing and crosslinking agents to nanocellulose-based cryogels. Despite the decrease in the overall positive surface charge, the addition of LNPs to the cCNF-based cryogels showed enhanced adsorption, not only towards the anionic aromatic pharmaceutical diclofenac but also towards the aromatic cationic metoprolol (MPL) and tramadol (TRA) and neutral aromatic carbamazepine. The addition of cLNPs to TCNF-based cryogels improved the adsorption of MPL and TRA despite the decrease in the net negative surface charge. The improved adsorption was attributed to modes of removal other than electrostatic attraction, and they could be 7C-7C aromatic ring or hydrophobic interactions brought by the addition of LNPs or cLNPs. However, significant improvement was only found if the ratio of LNPs or cLNPs to nanocellulose was 0.6:1 or higher and with spherical lignin nanomaterials. As crosslinking agents, the LNPs or cLNPs affected the rheological behavior of the gels, and increased the firmness and decreased the water holding capacity of the corresponding cryogels. The resistance of the cryogels towards disintegration with exposure to water also improved with crosslinking, which eventually enabled the cryogels, especially the TCNF-based one, to be regenerated and reused for five cycles of adsorption-desorption experiment for the model pharmaceutical MPL. Thus, this study opened new opportunities to utilize LNPs in providing nanocellulose-based adsorbents with additional functional groups, which were otherwise often achieved by rigorous chemical modifications, at the same time, crosslinking the nanocellulose network.

  • 6.
    Agustin, Melissa B.
    et al.
    Department of Food and Nutrition, Faculty of Agriculture and Forestry, University of Helsinki, P.O. Box 66, FI-00014, Helsinki, Finland; VTT Technical Research Centre of Finland Ltd., P.O. Box 1000, FI-02044, Espoo, Finland.
    Nematollahi, Neda
    Department of Food and Nutrition, Faculty of Agriculture and Forestry, University of Helsinki, P.O. Box 66, FI-00014, Helsinki, Finland.
    Bhattarai, Mamata
    Department of Food and Nutrition, Faculty of Agriculture and Forestry, University of Helsinki, P.O. Box 66, FI-00014, Helsinki, Finland; Department of Bioproducts and Biosystems, Aalto University, P.O. Box 16300, 00076, Aalto, Finland.
    Oliaei, Erfan
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Biocomposites.
    Lehtonen, Mari
    Department of Food and Nutrition, Faculty of Agriculture and Forestry, University of Helsinki, P.O. Box 66, FI-00014, Helsinki, Finland.
    Rojas, Orlando J.
    Department of Bioproducts and Biosystems, Aalto University, P.O. Box 16300, 00076, Aalto, Finland; Bioproducts Institute, Department of Chemical and Biological Engineering, Department of Chemistry and Department of Wood Science, University of British Columbia, 2360, East Mall, Vancouver, BC, V6T 1Z3, Canada.
    Mikkonen, Kirsi S.
    Department of Food and Nutrition, Faculty of Agriculture and Forestry, University of Helsinki, P.O. Box 66, FI-00014, Helsinki, Finland; Helsinki Institute of Sustainability Science, University of Helsinki, P.O. Box 65, FI-00014, Helsinki, Finland.
    Lignin nanoparticles as co-stabilizers and modifiers of nanocellulose-based Pickering emulsions and foams2023In: Cellulose, ISSN 0969-0239, E-ISSN 1572-882X, Vol. 30, no 14, p. 8955-8971Article in journal (Refereed)
    Abstract [en]

    Nanocellulose is very hydrophilic, preventing interactions with the oil phase in Pickering emulsions. This limitation is herein addressed by incorporating lignin nanoparticles (LNPs) as co-stabilizers of nanocellulose-based Pickering emulsions. LNP addition decreases the oil droplet size and slows creaming at pH 5 and 8 and with increasing LNP content. Emulsification at pH 3 and LNP cationization lead to droplet flocculation and rapid creaming. LNP application for emulsification, prior or simultaneously with nanocellulose, favors stability given the improved interactions with the oil phase. The Pickering emulsions can be freeze–dried, enabling the recovery of a solid macroporous foam that can act as adsorbent for pharmaceutical pollutants. Overall, the properties of nanocellulose-based Pickering emulsions and foams can be tailored by LNP addition. This strategy offers a unique, green approach to stabilize biphasic systems using bio-based nanomaterials without tedious and costly modification procedures.

  • 7.
    Ahmad, Shargeel
    et al.
    Dalian Univ Technol, Inst Artificial Photosynth, State Key Lab Fine Chem, Dalian 116024, Peoples R China..
    Liu, Jinxuan
    Dalian Univ Technol, Inst Artificial Photosynth, State Key Lab Fine Chem, Dalian 116024, Peoples R China..
    Gong, Chenghuan
    Dalian Univ Technol, Inst Artificial Photosynth, State Key Lab Fine Chem, Dalian 116024, Peoples R China..
    Zhao, Jianzhang
    Dalian Univ Technol, Inst Artificial Photosynth, State Key Lab Fine Chem, Dalian 116024, Peoples R China..
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry. Dalian Univ Technol, Inst Artificial Photosynth, State Key Lab Fine Chem, Dalian 116024, Peoples R China..
    Photon Up-Conversion via Epitaxial Surface-Supported Metal-Organic Framework Thin Films with Enhanced Photocurrent2018In: ACS Applied Energy Materials, E-ISSN 2574-0962, Vol. 1, no 2, p. 249-253Article in journal (Refereed)
    Abstract [en]

    We report a new triplet-triplet annihilation photon up-conversion (TTA-UC) system using an epitaxial Zn-perylene surface-supported metal-organic framework (SURMOF) grown on metal oxide surface as "emitter", and a platinum octaethylporphyrin (PtOEP) as "sensitizer" in [Co(bpy)(3)](2+/3+) acetonitrile solution. It has been demonstrated that the photocurrent can be significantly enhanced relative to epitaxial Zn-perylene SURMOF due to the TTA-UC mechanism. This initial result holds promising applications toward SURMOF-based solar energy conversion devices.

  • 8.
    Ahmed, Safya
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry.
    Encapsulation of a biologic for pulmonary delivery via inhalation2023Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In recent years biologics have gained a lot of interest in the pharmaceutical industry due to their appealing features. However, the concern with these types of drugs is in regard to the chosen delivery route, which is limited to parenteral injections today. Pulmonary delivery is another alternative route that can be used to deliver the biologic, which is a route that is less invasive than the parenteral routes. Additionally, it bypasses the gastrointestinal system which reduces the risk of degrading the biologic. When delivering the drugs it can be advantageous to use drug carriers which will enable the drug to be delivered at high concentrations to its target. 

    In this thesis, mesoporous silica particles were used as excipients to deliver a biologic via inhalation for pulmonary delivery. The particles being used have been specially designed by the life science company, Nanologica AB (publ), to be used in dry powder inhaler formulations. Lipase originating from mucor miehei was loaded into the NLAB SPIRO® particles using two different methods: incipient wetness and adsorption. Loading with the adsorption method showed to be non-efficient and non-linear  with the change in pH. A more efficient loading was, however, obtained with the incipient wetness method, where the 2.5 wt% and 5 wt% loaded particles were the most homogenous. Aerosolization studies of these two loaded particles were performed in a reduced Next generation impactor (rNGI) and the fine particle fraction (FPF) was similar to that of the unloaded particles, indicating that the loading of the biologic did not affect their ability to be aerosolized and deposited in the lungs. Release studies of the encapsulated lipase in simulated lung conditions showed that more than 90% of the lipase is released within 2 hours. Initial results from an activity assay indicated that the released lipase was in active form, however further work to quantify the activity is required.

  • 9. Ahmed, Towfiq
    et al.
    Haraldsen, Jason T.
    Zhu, Jian-Xin
    Balatsky, Alexander V.
    KTH, Centres, Nordic Institute for Theoretical Physics NORDITA. Institute for Materials Science, Los Alamos National Laboratory, United States.
    Next-Generation Epigenetic Detection Technique: Identifying Methylated Cytosine Using Graphene Nanopore2014In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 5, no 15, p. 2601-2607Article in journal (Refereed)
    Abstract [en]

    DNA methylation plays a pivotal role in the genetic evolution of both embryonic and adult cells. For adult somatic cells, the location and dynamics of methylation have been very precisely pinned down with the 5-cytosine markers on cytosine-phosphate-guanine (CpG) units. Unusual methylation on CpG islands is identified as one of the prime causes for silencing the tumor suppressant genes. Early detection of methylation changes can diagnose the potentially harmful oncogenic evolution of cells and provide promising guideline for cancer prevention. With this motivation, we propose a cytosine methylation detection technique. Our hypothesis is that electronic signatures of DNA acquired as a molecule translocates through a nanopore would be significantly different for methylated and nonmethylated bases. This difference in electronic fingerprints would allow for reliable real-time differentiation of methylated DNA. We calculate transport currents through a punctured graphene membrane while the cytosine and methylated cytosine translocate through the nanopore. We also calculate the transport properties for uracil and cyanocytosine for comparison. Our calculations of transmission, current, and tunneling conductance show distinct signatures in their spectrum for each molecular type. Thus, in this work, we provide a theoretical analysis that points to a viability of our hypothesis.

  • 10. Ai, Yuejie
    et al.
    Li, Xin
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Ji, Yongfei
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Song, Wei-Guo
    Luo, Yi
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Hydrophobicity and Hydrophilicity Balance Determines Shape Selectivity of Suzuki Coupling Reactions Inside Pd@meso-SiO2 Nanoreactor2016In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 120, no 19, p. 10244-10251Article in journal (Refereed)
    Abstract [en]

    Molecular sorting and catalysis directed by shape selectivity have been extensively applied in porous extended frameworks for a low-carbon, predictable, renewable component of modern industry. A comprehensive understanding of the underlying recognition mechanism toward different shapes is unfortunately still missing, owing to the lack of structural and dynamic information under operating conditions. We demonstrate here that such difficulties can be overcome by state-of-the-art molecular dynamics simulations which provide atomistic details that are not accessible experimentally, as exemplified by our interpretation for the experimentally observed aggregation induced shape selectivity for Suzuki C-C coupling reaction catalyzed by Pd particles in mesoporous silica. It is found that both aggregation ability and aggregating pattern of the reactants play the decisive role in controlling the shape selectivity, which are in turn determined by the balance between the hydrophobicity and hydrophilicity of the reactants, or in other words, by the balance between the noncovalent hydrogen bonding interaction and van der Waals forces. A general rule that allows prediction of the shape selectivity of a reactant has been proposed and verified against experiments. We show that molecular modeling is a powerful tool for rational design of new mesoporous systems and for the control of catalytic reactions that are important for the petrochemical industry.

  • 11.
    Aidas, Kestutis
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Kongsted, Jacob
    Laaksonen, Aatto
    Mocci, Francesca
    A quantum mechanics/molecular dynamics study of electric field gradient fluctuations in the liquid phase. The case of Na+ in aqueous solution2013In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 15, no 5, p. 1621-1631Article in journal (Refereed)
    Abstract [en]

    The Na-23 quadrupolar coupling constant of the Na+ ion in aqueous solution has been predicted using molecular dynamics simulations and hybrid quantum mechanics/molecular mechanics methods for the calculation of electric field gradients. The developed computational approach is generally expected to provide reliable estimates of the quadrupolar coupling constants of monoatomic species in condensed phases, and we show here that intermolecular polarization and non-electrostatic interactions are of crucial importance as they result in a 100% increased quadrupolar coupling constant of the ion as compared to a simpler pure electrostatic picture. These findings question the reliability of the commonly applied classical Sternheimer approximation for the calculations of the electric field gradient. As it can be expected from symmetry considerations, the quadrupolar coupling constants of the 5- and 6-coordinated Na+ ions in solution are found to differ significantly.

  • 12. Ai-Xi, Chen
    et al.
    Hong, Wang
    Duan, Sai
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Hai-Ming, Zhang
    Xin, Xu
    Li-Feng, Chi
    Potential-Induced Phase Transition of N-Isobutyryl-L-cysteine Monolayers on Au(111) Surfaces2017In: Wuli huaxue xuebao, ISSN 1000-6818, Vol. 33, no 5, p. 1010-1016Article in journal (Refereed)
    Abstract [en]

    Functional solid substrates modified by self-assembled monolayers (SAMs) have potential applications in biosensors, chromatography, and biocompatible materials. The potential-induced phase transition of N-isobutyryl-L-cysteine (L-NIBC) SAMs on Au(111) surfaces was investigated by in-situ electrochemical scanning tunneling microscopy (EC-STM) in 0.1 mol.L-1 H2SO4 solution. The NIBC SAMs with two distinct structures (alpha phase and beta phase) can be prepared by immersing the Au(111) substrate in pure NIBC aqueous solution and NIBC solution controlled by phosphate buffer at pH 7, respectively. The as-prepared a phase and beta phase of NIBC SAMs show various structural changes under the control of electrochemical potentials of the Au(111) in H2SO4 solution. The a phase NIBC SAMs exhibit structural changes from ordered to disordered structures with potential changes from 0.7 V (vs saturated calomel electrode, SCE) to 0.2 V. However, the beta phase NIBC SAMs undergo structural changes from disordered structures (E < 0.3 V) to y phase (0.4 V < E < 0.5 V) and finally to the beta phase (0.5 V < E < 0.7 V). EC-STM images also indicate that the phase transition from the alpha phase NIBC SAMs to the a phase occurs at positive potential. Combined with density functional theory (DFT) calculations, the phase transition from the beta phase to the a phase is explained by the potential-induced break of bonding interactions between -COO- and the negatively charged gold surfaces.

  • 13.
    Ajpi Condori, Cesario
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry. UMSA Univ Mayor San Andres, IIQ Chem Res Inst, Dept Inorgan Chem & Mat Sci Adv Mat, La Paz, Bolivia..
    Leiva, Naviana
    UMSA Univ Mayor San Andres, IIQ Chem Res Inst, Dept Inorgan Chem & Mat Sci Adv Mat, La Paz, Bolivia..
    Vargas, Max
    UMSA Univ Mayor San Andres, IIQ Chem Res Inst, Dept Inorgan Chem & Mat Sci Adv Mat, La Paz, Bolivia..
    Lundblad, Anders
    Res Inst Sweden, Div Safety & Transport Elect, RISE, SE-50462 Borås, Sweden..
    Lindbergh, Göran
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Cabrera, Saul
    UMSA Univ Mayor San Andres, IIQ Chem Res Inst, Dept Inorgan Chem & Mat Sci Adv Mat, La Paz, Bolivia..
    Synthesis and spectroscopic characterization of NiII coordination network:: Poly-[tris(µ4-Benzene-1,4-dicarboxylato)-tetrakis(µ1-dimethylformamide-κ1O)-trinickel(II)] as material for lithium ion batteries2022In: Journal of Molecular Structure, ISSN 0022-2860, E-ISSN 1872-8014, Vol. 1265, p. 133316-, article id 133316Article in journal (Refereed)
    Abstract [en]

    The compound Ni3(C8H4O4)3(C3H7NO)3, poly-[tris(µ4-Benzene-1,4-dicarboxylato)-tetrakis(µ1-dimethylformamide-κ1O)-trinickel(II)], was synthesized by the solvothermal method prepared via reaction between NiCl2•6H2O and terephthalic acid using N,N-dimethylformamide (DMF) as solvent. The structure was characterized by powder X-ray diffraction and infrared spectroscopy analyses. The electrochemical properties as a potential active material in lithium-ion batteries were characterized by electrochemical impedance spectroscopy and galvanostatic charge-discharge curves in a battery half-cell.

    The characterization results show that the coordination network contains one independent structure in the asymmetric unit. It is constructed from Ni2+ ions, terephthalate bridges and in-situ-generated DMF ligands, forming two similar two-dimensional (2D) layer structures. These similar 2D layers are in an alternating arrangement and are linked with each other by dense H—H interactions (45%) to generate a three-dimensional (3D) supramolecular framework with ordered and disordered DMF molecules.

    The electrochemical measurements, conducted in the potential range of 0.5–3.5 V vs Li/Li+, show that Ni3(C8H4O4)3(C3H7NO)4 has good electrochemical properties and can work as anode in lithium-ion batteries. The material presents an initial specific capacity of ∼420 mAh g−1, which drops during consecutive scans but stabilizes at ∼50 mAh g−1. However, due to the wide potential range there are indications of a gradual collapse of the structure. The electrochemical impedance spectroscopy shows an increase of charge transfer resistance from 24 to 1190 Ohms after cycling likely due to this collapse.

  • 14.
    Akpe, Victor
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Cell Physics.
    Brismar, Hjalmar
    KTH, School of Engineering Sciences (SCI), Applied Physics, Cell Physics.
    Nyokong, Tebello
    Osadebe, P. O.
    Photophysical and photochemical parameters of octakis (benzylthio) phthalocyaninato zinc, aluminium and tin: Red shift index concept in solvent effect on the ground state absorption of zinc phthalocyanine derivatives2010In: Journal of Molecular Structure, ISSN 0022-2860, E-ISSN 1872-8014, Vol. 984, no 1-3, p. 1-14Article in journal (Refereed)
    Abstract [en]

    This paper addresses the synthesis of octa-substituted benzylthio metallophthalocyanines (OBTMPcs) that contain the central metal ions of Zn2+, Al3+ and Sn4+. The ground state absorption of ZnPc(SR)(8) (OBTZnPc) along with the ZnPc derivatives, well documented in literature were used to study a new concept called the red shift index (RsI). The concept is based on the empirical values of RsI of the different complexes in solvent media. Unequivocally, parameters used in this paper show strong correlations that are consistent with the results obtained. For instance, 12,1 of the complexes tend to increase as the refractive index, n(D), and solvent donor, DN, of solvent increases. Photodegradation (photobleaching) quantum yield, phi(d) measurements of these compounds show that they are highly photostable, phi(d) (0.03-0.33 x 10(-5)). The triplet quantum yield, phi(T) (0.40-0.53) and the triplet lifetime, tau(T) (610-810 mu s) are within the typical range for metallophthalocyanines in DMSO. The photosensitisation efficiency. S-Delta, is relatively high for all the molecules (0.74-0.90). (C) 2010 Elsevier B.V. All rights reserved.

  • 15.
    Al Soubaihi, Rola Mohammad
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Saoud, Khaled Mohammad
    Virginia Commonwealth Univ Qatar, Liberal Arts & Sci Program, POB 8095, Doha, Qatar..
    Dutta, Joydeep
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Critical Review of Low-Temperature CO Oxidation and Hysteresis Phenomenon on Heterogeneous Catalysts2018In: Catalysts, E-ISSN 2073-4344, Vol. 8, no 12, article id 660Article, review/survey (Refereed)
    Abstract [en]

    There is a growing demand for new heterogeneous catalysts for cost-effective catalysis. Currently, the hysteresis phenomenon during low-temperature CO oxidation is an important topic in heterogeneous catalysis. Hysteresis provides important information about fluctuating reaction conditions that affect the regeneration of active sites and indicate the restoration of catalyst activity. Understanding its dynamic behavior, such as hysteresis and self-sustained kinetic oscillations, during CO oxidation, is crucial for the development of cost-effective, stable and long-lasting catalysts. Hysteresis during CO oxidation has a direct influence on many industrial processes and its understanding can be beneficial to a broad range of applications, including long-life CO2 lasers, gas masks, catalytic converters, sensors, indoor air quality, etc. This review considers the most recent reported advancements in the field of hysteresis behavior during CO oxidation which shed light on the origin of this phenomenon and the parameters that influence the type, shape, and width of the conversion of the hysteresis curves.

  • 16.
    Alaei, Zahra
    KTH, School of Chemical Science and Engineering (CHE).
    Release of Solubilizate from Micelle Triggered by Core Freezing2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The present thesis focuses on the release of solubilizate from micelle triggered by core freezing studied using 1H-NMR spectroscopy. The surfactant studied was the nonionic BrijTM S20 with a concentration of 1 wt% in water and hexamethyldisiloxane (HMDSO) was used as the model solubilizate to be loaded in micelle. The solubilizate in the micelle was found be squeezed out by core shrinking of the micelle upon decreasing the temperature. Besides 1H-NMR spectra, self-diffusion coefficients and longitudinal relaxation times                          were also measured upon decreasing the temperature. The temperature-dependent fraction of HMDSO in the micelle was determined together with relevant properties of the micelle, such as core freezing point, internal dynamics and size. The results were compared to corresponding data in the neat micellar system.

  • 17.
    Alexander, Shovsky
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Polyelectrolyte complexes of bottle brush copolymers: Solution and adsorption properties2011Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The aim of this thesis work was to systematically investigate the physico-chemical properties of polyelectrolyte complexes (PECs) formed by bottle brush and linear polyelectrolytes in solution and at solid / liquid interfaces. Electrostatic self-assembly of oppositely charged macromolecules in aqueous solution is a versatile strategy to construction of functional nanostructures with easily controlled properties. Bottle brush architecture, introduced into the PEC, generates a number of distinctive properties of the complexes, related to a broad range of application, such as colloidal stability and protein repellency to name a few. To utilize these materials in a wide range of applications e.g. drug delivery, the understanding of the effects of polymer architecture and solution parameters on the properties of bottle brush PECs is of paramount importance. This thesis constitutes a systematic investigation of PECs formed by a series of cationic bottle-brush polyelectrolytes and a series of anionic linear polyelectrolytes in aqueous solution. The focus of the first part of the thesis was primarily on formation and characterization of PECs in solution, whereas the adsorption properties and adsorption kinetics of bottle-brush polyelectrolytes and their complexes was investigated in the second part of the thesis work. In particular, effects of the side-chain density of the bottlebrush polyelectrolyte, concentration, mixing ratio and molecular weigh of the linearpolyelectrolyte on formation, solution properties, stability and adsorption of PECs were addressed.

    The pronounced effect of the side-chain density of the bottle-brush polyelectrolyte on the properties of stoichiometric and nonstoichiometric PECs was demonstrated. Formation of PECs by bottle-brush copolymers with high density of side-chains results in small, watersoluble, molecular complexes having nonspherical shape, independent of concentration. Whereas formation of PEC-aggregates was revealed by bottle-brush polyelectrolytes with low side chain density, the level of aggregation in these complexes is controlled by polyelectrolyte concentration. The structure of the PECs formed with low molecular weight polyanions is consistent with the picture that several small linear polyelectrolyte molecules associate with the large bottle-brush. In contrast, when complexation occurs between polyanions of high molecular weigh and the bottle-brush polymers considerably larger PECs are formed, consistent with several bottle-brush polymers associating with one high molecular weight polyanion.

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  • 18.
    Alipoormazandarani, Niloofar
    et al.
    Lakehead Univ, Dept Chem Engn, Thunder Bay, ON, Canada.;Abo Akad Univ, Lab Nat Mat Technol, Turku, Finland..
    Benselfelt, Tobias
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Coating Technology.
    Wang, Luyao
    Abo Akad Univ, Lab Nat Mat Technol, Turku, Finland..
    Wang, Xiaoju
    Abo Akad Univ, Lab Nat Mat Technol, Turku, Finland..
    Xu, Chunlin
    Abo Akad Univ, Lab Nat Mat Technol, Turku, Finland..
    Wågberg, Lars
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Willfor, Stefan
    Abo Akad Univ, Lab Nat Mat Technol, Turku, Finland..
    Fatehi, Pedram
    Lakehead Univ, Dept Chem Engn, Thunder Bay, ON, Canada.;Qilu Univ Technol, State Key Lab Biobased Mat & Green Papermaking, Jinan, Shandong, Peoples R China..
    Functional Lignin Nanoparticles with Tunable Size and Surface Properties: Fabrication, Characterization, and Use in Layer-by-Layer Assembly2021In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 13, no 22, p. 26308-26317Article in journal (Refereed)
    Abstract [en]

    Lignin is the richest source of renewable aromatics and has immense potential for replacing synthetic chemicals. The limited functionality of lignin is, however, challenging for its potential use, which motivates research for creating advanced functional lignin-derived materials. Here, we present an aqueous-based acid precipitation method for preparing functional lignin nanoparticles (LNPs) from carboxy-methylated or carboxy-pentylated lignin. We observe that the longer grafted side chains of carboxy-pentylated lignin allow for the formation of larger LNPs. The functional nanoparticles have high tolerance against salt and aging time and well-controlled size distribution with R-h <= 60 nm over a pH range of 5-11. We further investigate the layer-by-layer (LbL) assembly of the LNPs and poly(allylamine hydrochloride) (PAH) using a stagnation point adsorption reflectometry (SPAR) and quartz crystal microbalance with dissipation (QCM-D). Results demonstrate that LNPs made of carboxypentylated lignin (i.e., PLNPs with the adsorbed mass of 3.02 mg/m(2)) form a more packed and thicker adlayer onto the PAH surface compared to those made of carboxymethylated lignin (i.e., CLNPs with the adsorbed mass of 2.51 mg/m(2)). The theoretical flux, J, and initial rate of adsorption, (d Gamma/dt)(0), analyses confirm that 22% of PLNPs and 20% of CLNPs arriving at the PAH surface are adsorbed. The present study provides a feasible platform for engineering LNPs with a tunable size and adsorption behavior, which can be adapted in hionanomaterial production.

  • 19. Allouche, Joachim
    et al.
    Tyrode, Eric
    Laboratorio FIRP, Ingeniería Química, Universidad de Los Andes, Avenida Don Tulio Febres, Mérida .
    Sadtler, Veronique
    Choplin, Lionel
    Salager, Jean-Louis
    Simultaneous Conductivity and Viscosity Measurements as a Technique To Track Emulsion Inversion by the Phase-Inversion-Temperature Method2004In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 20, no 6, p. 2134-2140Article in journal (Refereed)
    Abstract [en]

    Two kinds of transitions can occur when an emulsified water-oil-ethoxylated nonionic surfactant system is cooled under const. stirring. At a water-oil ratio close to unity, a transitional inversion takes place from a water-in-oil (W/O) to an oil-in-water (O/W) morphol. according to the so-called phase-inversion-temp. method. At a high water content, a multiple W/O/W emulsion changes to a simple O/W emulsion. The continuous monitoring of both the emulsion cond. and viscosity allows the identification of several phenomena that take place during the temp. decrease. In all cases, a viscosity max. is found on each side of the three-phase behavior temp. interval and correlates with the attainment of extremely fine emulsions, where the best compromise between a low-tension and a not-too-unstable emulsion is reached. The studied system contains Polysorbate 85, a light alkane cut oil, and a sodium chloride brine. All transitions are interpreted in the framework of the formulation-compn. bidimensional map.

  • 20. Allouche, Joachim
    et al.
    Tyrode, Eric
    FIRP Laboratory, Universidad de Los Andes, Mérida.
    Sadtler, Veronique
    Choplin, Lionel
    Salager, Jean-Louis
    Single- and Two-Step Emulsification To Prepare a Persistent Multiple Emulsion with a Surfactant-Polymer Mixture2003In: Industrial & Engineering Chemistry Research, ISSN 0888-5885, E-ISSN 1520-5045, Vol. 42, no 17, p. 3982-3988Article in journal (Refereed)
    Abstract [en]

    The regions corresponding to different emulsion morphol. occurrences have been clearly identified on a bidimensional formulation-compn. map. Multiple emulsions spontaneously form when there is a conflict between the formulation and compn. effects. In such systems the most external emulsion is found to be unstable when the formulation effect is produced by a single surfactant. The use of a proper surfactant-polymer mixt. allows one to strongly inhibit the mass transfer and to considerably lengthen the equilibration between interfaces. As a consequence, the multiple emulsion can be stable enough to be used in encapsulation and controlled-release applications. The area where multiple emulsions occur and their characteristics (cond. and amt. of encapsulated external phase) are reported for a system contg. a sorbitan ester lipophilic surfactant and a diblock poly(ethylene oxide)-poly(propylene oxide) hydrophilic polymer, as a function of the formulation and compn., for a single-step process in which a specific amt. of mech. energy (stirring) is supplied. An increase in the oil viscosity is found to alter the map and to modify the multiple emulsion characteristics. The application of the results to emulsion-making technol. is discussed.

  • 21. Altincekic, T. G.
    et al.
    Boz, I.
    Baykal, A.
    Kazan, S.
    Topkaya, R.
    Toprak, Muhammet S.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Synthesis and characterization of CuFe2O4 nanorods synthesized by polyol route2010In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 493, no 1-2, p. 493-498Article in journal (Refereed)
    Abstract [en]

    Uniform, high quality, CuFe2O4 nanorods with high aspect ratios were synthesized by a surfactant-free single step polyol process at 220 degrees C. The structure of the product was characterized by XRD and FT-IR, and the morphology of the product was analyzed by SEM. The results showed that the as-prepared nanorods have a uniform cross-section and with average diameter of similar to 100 nm and aspect ratio in the range of 13-52. X-ray line profile fitting resulted in crystallite size of 15 nm, which reveals the polycrystalline nature of these nanorods. Magnetic characterization of product was performed by EPR and VSM techniques and the results show that the CuFe2O4 nanorods are ferromagnetic. The line width of the resonance lines in FMR is about 1.8 kOe which may originate from different resonance fields of randomly distributed nanocrystals which have different orientation of magnetic easy axes.

  • 22.
    Amft, Martin
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Multiscale Materials Modelling.
    Walle, L. E.
    Ragazzon, D.
    Borg, A.
    Uvdal, P.
    Skorodumova, Natalia V.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Multiscale Materials Modelling.
    Sandell, A.
    A Molecular Mechanism for the Water-Hydroxyl Balance during Wetting of TiO22013In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 117, no 33, p. 17078-17083Article in journal (Refereed)
    Abstract [en]

    We show that the formation of the wetting layer and the experimentally observed continuous shift of the H2O-OH balance toward molecular water at increasing coverage on a TiO2(110) surface can be rationalized on a molecular level. The mechanism is based on the initial formation of stable hydroxyl pairs, a repulsive interaction between these pairs, and an attractive interaction with respect to water molecules. The experimental data are obtained by synchrotron radiation photoelectron spectroscopy and interpreted with the aid of density functional theory calculations and Monte Carlo simulations.

  • 23.
    Amizhtan, S. K.
    et al.
    Indian Inst Technol Madras IIT Madras, Dept Elect Engn, Chennai 600036, Tamil Nadu, India..
    Amalanathan, A. J.
    Indian Inst Technol Madras IIT Madras, Dept Elect Engn, Chennai 600036, Tamil Nadu, India..
    Babu, Myneni Sukesh
    Indian Inst Technol Madras IIT Madras, Dept Elect Engn, Chennai 600036, Tamil Nadu, India..
    Sarathi, R.
    Indian Inst Technol Madras IIT Madras, Dept Elect Engn, Chennai 600036, Tamil Nadu, India..
    Kumar, Ganesh
    Indian Inst Technol Madras IIT Madras, Dept Ocean Engn, Chennai 600036, Tamil Nadu, India..
    Sangwai, Jitendra S.
    Edin, Hans Ezz
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Taylor, Nathaniel
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Experimental Study and ANN Analysis of Rheological Behavior of Mineral Oil-Based SiO2 Nanofluids2022In: IEEE transactions on dielectrics and electrical insulation, ISSN 1070-9878, E-ISSN 1558-4135, Vol. 29, no 3, p. 956-964Article in journal (Refereed)
    Abstract [en]

    This work reports an experimental and theoretical analysis of the rheological properties of mineral oil-based SiO2 nanofluid for their potential applications in transformer insulation. The flow electrification mechanism on the nanofluids with different surfactants such as cetyl trimethyl ammonium bromide (CTAB), oleic acid, and Span 80 is studied using a spinning disk technique. The results show a higher streaming current for the nanofluids with CTAB as a surfactant compared to oleic acid and Span 80. The rheological behavior of nanofluids is explored with the double gap concentric cylinder geometry. The variation of shear stress with shear rate follows a power law relationship along with a yield stress observed for all the nanofluids. A transition is seen from storage modulus to dominant loss modulus for the nanofluids during the frequency sweep analysis, whereas no transition is observed in the case of mineral oil. In addition, regression analysis using artificial neural network (ANN) algorithms are performed on the experimentally measured viscosity of the nanofluids in order to estimate theoretical parameters and provide insights into the streaming current formation. The desirable rheological characteristics of nanofluids are identified for achieving enhanced insulation performance in transformers.

  • 24.
    Amizhtan, S. K.
    et al.
    Indian Inst Technol Madras, Dept Elect Engn, Chennai 600036, Tamil Nadu, India..
    Amalanathan, A. J.
    Indian Inst Technol Madras, Dept Elect Engn, Chennai 600036, Tamil Nadu, India..
    Sarathi, R.
    Indian Inst Technol Madras, Dept Elect Engn, Chennai 600036, Tamil Nadu, India..
    Srinivasan, Balaji
    Indian Inst Technol Madras, Dept Elect Engn, Chennai 600036, Tamil Nadu, India..
    Gardas, Ramesh L.
    Indian Inst Technol Madras, Dept Chem, Chennai 600036, Tamil Nadu, India..
    Edin, Hans Ezz
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Taylor, Nathaniel
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Impact of Surfactants on the Electrical and Rheological Aspects of Silica Based Synthetic Ester Nanofluids2022In: IEEE Access, E-ISSN 2169-3536, Vol. 10, p. 18192-18200Article in journal (Refereed)
    Abstract [en]

    This study reports experimental investigations of the effects of different surfactants (CTAB, Oleic acid and Span 80) on silica based synthetic ester nanofluids. The positive and negative potential observed for the ionic (CTAB) and non-ionic surfactant (Span 80) from zeta potential analysis indicates an improved stability. The optimization of nanofillers and surfactants is performed considering the corona inception voltage measured using ultra high frequency (UHF) technique and fluorescent fiber. Rheological analysis shows no significant variation of properties with shear rate, implying Newtonian behavior even with the addition of surfactant. In addition, the permittivity of the nanofluid is not much affected by adding surfactant but a marginal variation is noticed in the loss tangent with the effect of temperature. The fluorescence spectroscopy shows no change in the emission wavelength with the addition of silica nanofiller and surfactants. Flow electrification studies indicate an increase in the streaming current with the rotation speed and temperature, with a higher current magnitude observed in the case of nanofluids.

  • 25. An, J.
    et al.
    Tian, Z.
    Zhang, L.
    Yang, X.
    Cai, B.
    Yu, Z.
    Hagfeldt, A.
    Sun, Licheng
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry. State Key Laboratory of Fine Chemicals, Institute of Artificial Photosynthesis, DUT-KTH Joint Education and Research Center on Molecular Devices, Dalian University of Technology (DUT), Dalian 116024, China.
    Supramolecular Co-adsorption on TiO2to enhance the efficiency of dye-sensitized solar cells2021In: Journal of Materials Chemistry A, ISSN 2050-7488, E-ISSN 2050-7496, Vol. 9, no 23, p. 13697-13703Article in journal (Refereed)
    Abstract [en]

    Three novel push-pull dyes, with carbazole donors, codedAJ502,TZ101andTZ102are synthesized and applied as co-sensitizers in dye-sensitized solar cells (DSSCs).TZ101andTZ102have similar structures except for two fluorine atoms introduced on the benzotriazole (BTZ) unit.AJ502shows a near-IR absorption spectrum that is suitable for co-sensitization withTZ101andTZ102. The co-sensitized DSSC device based onCO-1(AJ502 : TZ101= 3 : 4 (0.075 mM : 0.1 mM)) achieves a power conversion efficiency (PCE) of 10.3% under AM 1.5G irradiation, with 1.06 V open-circuit voltage (Voc), 13.75 mA cm−2short-circuit photocurrent density (Jsc), and 70.8% fill factor (FF), a significant improvement compared to the single dye, 6.0% forAJ502and 5.1% forTZ101with a copper(i/ii)-based redox electrolyte. A PCE of 8.9% is also obtained by devices based onCO-2(AJ502 : TZ102= 3 : 4). ForCO-1, the fluorine atoms inTZ101play a critical role by widening the active light capturing bands of bothTZ101andAJ502on the TiO2film whileTZ102andAJ502show weaker interaction under the same conditions. The UV-vis spectrum and Raman spectrum revealed thatAJ502can form supramolecules withTZ101andTZ102formed on the TiO2film. 

  • 26.
    An, Jincheng
    et al.
    State Key Laboratory of Fine Chemicals, Institute of Artificial Photosynthesis, DUT−KTH Joint Education and Research Center on Molecular Devices, Dalian University of Technology (DUT), Dalian 116024, China.
    Yang, Xichuan
    State Key Laboratory of Fine Chemicals, Institute of Artificial Photosynthesis, DUT−KTH Joint Education and Research Center on Molecular Devices, Dalian University of Technology (DUT), Dalian 116024, China.
    Cai, Bin
    State Key Laboratory of Fine Chemicals, Institute of Artificial Photosynthesis, DUT−KTH Joint Education and Research Center on Molecular Devices, Dalian University of Technology (DUT), Dalian 116024, China.
    Zhang, Li
    State Key Laboratory of Fine Chemicals, Institute of Artificial Photosynthesis, DUT−KTH Joint Education and Research Center on Molecular Devices, Dalian University of Technology (DUT), Dalian 116024, China.
    Yang, Kaiyuan
    State Key Laboratory of Fine Chemicals, Institute of Artificial Photosynthesis, DUT−KTH Joint Education and Research Center on Molecular Devices, Dalian University of Technology (DUT), Dalian 116024, China.
    Yu, Ze
    State Key Laboratory of Fine Chemicals, Institute of Artificial Photosynthesis, DUT−KTH Joint Education and Research Center on Molecular Devices, Dalian University of Technology (DUT), Dalian 116024, China.
    Wang, Xiuna
    State Key Laboratory of Fine Chemicals, Institute of Artificial Photosynthesis, DUT−KTH Joint Education and Research Center on Molecular Devices, Dalian University of Technology (DUT), Dalian 116024, China.
    Hagfeldt, Anders
    Laboratory of Photomolecular Science, Institute of Chemical Sciences and Engineering, École Polytechnique Fédérale de Lausanne, Lausanne CH-1015, Switzerland.
    Sun, Licheng
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry. State Key Laboratory of Fine Chemicals, Institute of Artificial Photosynthesis, DUT−KTH Joint Education and Research Center on Molecular Devices, Dalian University of Technology (DUT), Dalian 116024, China.
    Fine-Tuning by Triple Bond of Carbazole Derivative Dyes to Obtain High Efficiency for Dye-Sensitized Solar Cells with Copper Electrolyte2020In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 12, no 41, p. 46397-46405Article in journal (Refereed)
    Abstract [en]

    Three novel dyes consisting of a 5,8,15-tris(2-ethylhexyl)-8,15-dihydro-5H-benzo[1,2-b:3,4-b':6,5-b″]tricarbazole (BTC) electron-donating group and a 4,7-bis(4-hexylthiophen-2-yl)benzo[c][1,2,5]thiadiazole (BTBT) π-bridge with an anchoring group of phenyl carboxyl acid were synthesized and applied in dye-sensitized solar cells (DSCs).The AJ202 did not contain any triple bonds, the AJ201's ethynyl group was inserted between the BTC and BTBT units, and the AJ206's ethynyl group was introduced between the BTBT moiety and the anchor group. The inclusion and position of the ethynyl linkage in the sensitizer molecules significantly altered the electrochemical properties of these dyes, which can fine-tune the energy levels of the dyes. The best performing devices contained AJ206 as a sensitizer and a Cu(I/II) redox couple, which resulted in a power conversion efficiency (PCE) up to 10.8% under the standard AM 1.5 G illumination, which obtained PCEs higher than those from the devices that contained AJ201 (9.2%) and AJ202 (9.7%) under the same conditions. The highest occupied molecular orbital and lowest unoccupied molecular orbital levels of the sensitizers were tuned to be well-suited for the Cu(I/II) redox potential and the Fermi level of TiO2. The innovative synthesis of a tricarbazole-based donor moiety in a sensitizer used in combination with a Cu(I/II) redox couple has resulted in relatively high PCEs.

  • 27.
    An, Jincheng
    et al.
    Dalian Univ Technol DUT, DUT KTH Joint Educ & Res Ctr Mol Devices, Inst Artificial Photosynth, State Key Lab Fine Chem, Dalian 116024, Peoples R China..
    Yang, Xichuan
    Dalian Univ Technol DUT, DUT KTH Joint Educ & Res Ctr Mol Devices, Inst Artificial Photosynth, State Key Lab Fine Chem, Dalian 116024, Peoples R China..
    Tian, Zhifeng
    Dalian Univ Technol DUT, DUT KTH Joint Educ & Res Ctr Mol Devices, Inst Artificial Photosynth, State Key Lab Fine Chem, Dalian 116024, Peoples R China..
    Cai, Bin
    Dalian Univ Technol DUT, DUT KTH Joint Educ & Res Ctr Mol Devices, Inst Artificial Photosynth, State Key Lab Fine Chem, Dalian 116024, Peoples R China..
    Zhang, Li
    Dalian Univ Technol DUT, DUT KTH Joint Educ & Res Ctr Mol Devices, Inst Artificial Photosynth, State Key Lab Fine Chem, Dalian 116024, Peoples R China..
    Yu, Ze
    Dalian Univ Technol DUT, DUT KTH Joint Educ & Res Ctr Mol Devices, Inst Artificial Photosynth, State Key Lab Fine Chem, Dalian 116024, Peoples R China..
    Wang, Xiuna
    Dalian Univ Technol DUT, DUT KTH Joint Educ & Res Ctr Mol Devices, Inst Artificial Photosynth, State Key Lab Fine Chem, Dalian 116024, Peoples R China..
    Hagfeldt, Anders
    Ecole Polytech Fed Lausanne, Lab Photomol Sci, Inst Chem Sci & Engn, CH-1015 Lausanne, Switzerland..
    Sun, Licheng
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry. Dalian Univ Technol DUT, DUT KTH Joint Educ & Res Ctr Mol Devices, Inst Artificial Photosynth, State Key Lab Fine Chem, Dalian 116024, Peoples R China..
    Thiophene-fused carbazole derivative dyes for high-performance dye-sensitized solar cells2021In: Tetrahedron, ISSN 0040-4020, E-ISSN 1464-5416, Vol. 88, article id 132124Article in journal (Refereed)
    Abstract [en]

    Two novel dyes that are similar in chemical structure, except for different donor units, AJ301and AJ303 were synthesized, characterized and applied as sensitizers in dye-sensitized solar cells (DSSCs). Both dyes exhibited a wide absorption of visible sunlight. The introduction of fused rings on the donor unit of AJ303 presented an appropriate energy level, less recombination and longer electron lifetime to achieve a power conversion efficiency (PCE) of 10.2%, far above that achieved for AJ301 of 6.2% with a [Co(bpy)(3)](2+/3+)-based electrolyte under standard AM1.5G solar irradiation (100 mW cm(-2)). The DSSCs based on AJ303 and AJ301 with [Cu(tmby)(2)](2+/+)-based electrolyte showed a lower PCE of 8.2% and 5.4%, respectively. Therefore, the results indicated that the introduction of a fused-ring in the donor group is a meaningful synthetic strategy to improve the photovoltaic performance.

  • 28.
    An, Junxue
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Biomolecular association – biolubrication perspective: Association between hyaluronan and phospholipids2011Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Dipalmitoylphosphatidylcholine (DPPC) vesicles were prepared by sonication and their size in sodium chloride solutions ([NaCl] = 0.116 M) containing different amount of calcium ions (0, 1, 2, 5, 10 mM) were studied by Dynamic Light Scattering (DLS). The time dependence of the particle size in various solutions was also tested. The data showed that the hydrodynamic diameter of DPPC vesicles was not affected by the Ca2+ concentration; however, the stability of DPPC vesicles was improved with the presence of Ca2+. Besides, when the temperature was above the phase transition temperature (41.5°C), the DPPC vesicles in dispersions with more than 2 mM CaCl2 remained stable for at least 2 weeks. Zeta potential of vesicles in aqueous solutions was tested by Zetasizer. The result showed that the stability of DPPC vesicles increased with increasing Ca2+ concentration with the evidence of increasing zeta potential due to the binding of Ca2+ onto vesicle bilayers. The association between zwitterionic DPPC vesicles and anionic polyelectrolyte hyaluronan (HA) was also studied by testing the hydrodynamic diameter and electrophoretic mobility change after the addition of HA. DLS results showed that the hydrodynamic diameter of DPPC vesicles increased in the presence of HA. In addition, after several days’ incubation at 55°C precipitation appeared in the DPPC-HA mixture solution. Furthermore, electrophoretic mobility of DPPC vesicles decreased after the addition of polyelectrolyte. The combined results demonstrated that the association between DPPC and HA occurred.

  • 29.
    An, Junxue
    KTH, School of Chemical Science and Engineering (CHE). KTH.
    Polymers in Aqueous Lubrication2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The main objective of this thesis work was to gain understanding of the layer properties and polymer structures that were able to aid lubrication in aqueous media. To this end, three types of polyelectrolytes: a diblock copolymer, a train-of-brushes and two brush-with-anchor mucins have been utilized. Their lubrication ability in the boundary lubrication regime has been examined by Atomic Force Microscopy with colloidal probe.

    The interfacial behavior of the thermoresponsive diblock copolymer, PIPOZ60-b-PAMPTAM17,on silica was studied in the temperature interval 25-50 ˚C. The main finding is that adsorption hysteresis, due to the presence of trapped states, is important when the adsorbed layers are in contact with a dilute polymer solution. The importance of trapped states was also demonstrated in the measured friction forces, where significantly lower friction forces, at a given temperature, were encountered on cooling than on the preceding heating stage, which was attributed to increased adsorbed amount. On the heating stage the friction force decreased with increasing temperature despite the worsening of the solvent condition, and the opposite trend was observed when using pre-adsorbed layers (constant adsorbed amount) as a consequence of increased segment-segment attraction.

    The second part of the studies was devoted to the interfacial properties of mucins on PMMA. The strong affinity provided by the anchoring group of C-PSLex and C-P55 together with their more extended layer structure contribute to the superior lubrication of PMMA compared to BSM up to pressures of 8-9 MPa. This is a result of minor bridging and lateral motion of molecules along the surface during shearing. We further studied the influence of glycosylation on interfacial properties of mucin by utilizing the highly purified mucins, C-P55 and C-PSLex. Our data suggest that the longer and more branched carbohydrate side chains on C-PSLex provide lower interpenetration and better hydration lubrication at low loads compared to the shorter carbohydrate chains on C-P55. However, the longer carbohydrates appear to counteract disentanglement less efficiently, giving rise to a higher friction force at high loads.

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  • 30.
    An, Junxue
    et al.
    Uppsala Univ, Dept Pharm, Uppsala, Sweden..
    Forchheimer, Daniel
    KTH, School of Engineering Sciences (SCI), Applied Physics, Nanostructure Physics.
    Sävmarker, Jonas
    Orexo AB, Pharmaceut Dev, Uppsala, Sweden..
    Brulls, Mikael
    AstraZeneca, Early Prod Dev & Mfg Pharmaceut Sci, R&D, Gothenburg, Sweden..
    Frenning, Goran
    Uppsala Univ, Dept Pharm, Uppsala, Sweden..
    Nanoscale characterization of PEGylated phospholipid coatings formed by spray drying on silica microparticles2020In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 577, p. 92-100Article in journal (Refereed)
    Abstract [en]

    Phospholipids constitute biocompatible and safe excipients for pulmonary drug delivery. They can retard the drug release and, when PEGylated, also prolong the residence time in the lung. The aim of this work was to assess the structure and coherence of phospholipid coatings formed by spray drying on hydrophilic surfaces (silica microparticles) on the nanoscale and, in particular, the effect of addition of PEGylated lipids thereon. Scanning electron microscopy showed the presence of nanoparticles of varying sizes on the microparticles with different PEGylated lipid concentrations. Atomic force microscopy confirmed the presence of a lipid coating on the spray-dried microparticles. It also revealed that the lipid-coated microparticles without PEGylated lipids had a rather homogenous coating whereas those with PEGylated lipids had a very heterogeneous coating with defects, which was corroborated by confocal laser scanning microscopy. All coated microparticles had good dispersibility without agglomerate formation, as indicated by particle size measurements. This study has demonstrated that coherent coatings of phospholipids on hydrophilic surfaces can be obtained by spray drying. However, the incorporation of PEGylated lipids in a one-step spray-drying process to prepare lipid coated microparticles with both controlled-release and stealth properties is very challenging.

  • 31.
    An, Junxue
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Jin, Chunsheng
    Dėdinaitė, Andra
    Holgerssond, Jan
    Karlssonb, Niclas G.
    Claesson, Per M.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Influence of Glycosylation on Interfacial Properties of Recombinant Mucins: Adsorption, Surface Forces and FrictionManuscript (preprint) (Other academic)
    Abstract [en]

    Interfacial properties of two brush-with-anchor mucins, C-P55 and C-PSLex, have been investigated at the aqueous solution/poly(methylmethacrylate) (PMMA) interface. Both are recombinant mucin-type fusion proteins, produced by fusing the glycosylated mucin part of P-selectin glycoprotein ligand-1 (PSLG-1) to the Fc part of a mouse immunoglobulin in two different cells. They are mainly expressed as dimers upon production. Analysis of the O-glycans shows that the C-PSLex mucin has the longer and more branched side chains, but C-P55 has slightly higher sialic acid content. The adsorption of the mucins to PMMA surfaces was studied by quartz crystal microbalance with dissipation. The sensed mass, including the adsorbed mucin and water trapped in the layer, was found to be similar for these two mucin layers. Atomic force microscopy with colloidal probe was employed to study surface and friction forces between mucin-coated PMMA surfaces. Purely repulsive forces of steric origin were observed between mucin layers on compression, whereas a small adhesion was detected between both mucin layers on decompression. This was attributed to chain entanglement. The friction force between C-PSLex-coated PMMA is lower than that between C-P55-coated PMMA at low loads, but vice versa at high loads. We discuss our results in terms of the differences in the glycosylation composition of these two mucins.

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  • 32.
    Andersson, Claes-Henrik
    et al.
    Uppsala Univ, Dept Biochem & Organ Chem, S-57123 Uppsala, Sweden..
    Lahmann, Martina
    Univ Bangor, Sch Chem, Bangor LL57 2UW, Gwynedd, Wales..
    Oscarson, Stefan
    Univ Coll Dublin, Ctr Synth & Chem Biol, Dublin 4, Ireland..
    Grennberg, Helena
    Uppsala Univ, Dept Biochem & Organ Chem, S-57123 Uppsala, Sweden..
    Reversible non-covalent derivatisation of carbon nanotubes with glycosides2009In: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 5, no 14, p. 2713-2716Article in journal (Refereed)
    Abstract [en]

    SWNTs and MWNTs have been non-covalently functionalized with glycosides in a reversible manner, and fluorescence titrations have been used to quantify the formed supramolecular assemblies which for SWNTs exhibits increased water solubility.

  • 33.
    Andersson, David A.
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Korzhavyi, Pavel A.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Johansson, Börje
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    First-principles based calculation of binary and multicomponent phase diagrams for titanium carbonitride2008In: Calphad, ISSN 0364-5916, E-ISSN 1873-2984, Vol. 32, no 3, p. 543-565Article in journal (Refereed)
    Abstract [en]

    In this paper we have used a combined first principles and Calphad approach to calculate phase diagrams in the titanium-carbon-nitrogen system, with particular focus on the vacancy-induced ordering of the substoichiometric carbonitride phase, TiCxNy (x + y <= 1). Results from earlier Monte Carlo simulations of the low-temperature binary phase diagrams are used in order to formulate sublattice models for TiCxNy within the compound energy formalism (CEF) that are capable of describing both the low temperature ordered and the high-temperature disordered state. We parameterize these models using first-principles calculations and then we demonstrate how they can be merged with thermodynamic descriptions of the remaining Ti-C-N phases that are derived within the Calphad method by fitting model parameters to experimental data. We also discuss structural and electronic properties of the ordered end-member compounds, as well as short range order effects in the TiCxNy phase.

  • 34.
    Andersson, David A.
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Korzhavyi, Pavel A.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Johansson, Börje
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Thermodynamics of structural vacancies in titanium monoxide from first principles calculations2005In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 71, no 14, p. 144101-Article in journal (Refereed)
    Abstract [en]

    The structure, stability and electronic properties of the low oxygen oxides of titanium, TiOx with 1/3 <= x <= 3/2, have been studied by means of accurate first-principles calculations. In both stoichiometric and nonstoichiometric TiO there are large fractions of vacant lattice sites. These so-called structural vacancies are essential for understanding the properties and phase stability of titanium oxides. Structures with an ordered arrangement of vacancies were treated with a plane wave pseudo-potential method, while calculations for structures with disordered vacancies were performed within the framework of the Korringa-Kohn-Rostoker Green's function technique. The relaxed structural parameters in general compare well with experimental data, though some discrepancies exist for stoichiometric TiO in the ideal B1 structure, i.e., without any vacancies. The equation of state as well as the elastic properties are also derived. A monoclinic, vacancy-containing, structure of stoichiometric TiO is confirmed to be stable at low temperature and pressure. Experimentally a transition from a stoichiometric cubic structure with disordered vacancies to the ideal B1 structure without any vacancies has been observed at high pressure. It is discussed how this experimental observation relates to the present theoretical results for defect-containing and defect-free TiO.

  • 35. Andrae, Johan C. G.
    et al.
    Brinck, Tore
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Kalghatgi, G. T.
    HCCI experiments with toluene reference fuels modeled by a semidetailed chemical kinetic model2008In: Combustion and Flame, ISSN 0010-2180, E-ISSN 1556-2921, Vol. 155, no 4, p. 696-712Article in journal (Refereed)
    Abstract [en]

    A semidetailed mechanism (137 species and 633 reactions) and new experiments in a homogeneous charge conic pression ignition (HCCI) engine on the autoignition of toluene reference fuels are presented. Skeletal mechanisms for isooctane and n-heptane were added to a detailed toluene submechanism. The model shows generally good agreement with ignition delay times measured in a shock tube and a rapid compression machine and is sensitive to changes in temperature, pressure, and mixture strength. The addition of reactions involving the formation and destruction of benzylperoxide radical was crucial to modeling toluene shock tube data. Laminar burning velocities for benzene and toluene were well predicted by the model after some revision of the high-temperature chemistry. Moreover, laminar burning velocities of a real gasoline at 353 and 500 K Could be predicted by the model using a toluene reference fuel as a surrogate. The model also captures the experimentally observed differences in combustion phasing of toluene/n-heptane mixtures, compared to a primary reference fuel of the same research octane number, in HCCI engines as the intake pressure and temperature are changed. For high intake pressures and low intake temperatures, a sensitivity analysis at the moment of maximum heat release rate shows that the consumption of phenoxy radicals is rate-limiting when a toluene/n-heptane fuel is used, which makes this fuel more resistant to autoignition than the primary reference fuel. Typical CPU times encountered in zero-dimensional calculations were on the order of seconds and minutes in laminar flame speed calculations. Cross reactions between benzylperoxy radicals and n-heptane improved the model prediction,,; of shock tube experiments for phi = 1.0 and temperatures lower than 800 K for an n-heptane/toluene fuel mixture, but cross reactions had no influence on HCCI Simulations.

  • 36.
    Anil, Athira
    et al.
    Department of Material Science and Engineering, Ångström Laboratory, Uppsala University, Box 35 751 03 Uppsala Sweden.
    White, Jai
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Campos dos Santos, Egon
    Advanced Institute for Materials Research (WPI-AIMR), Tohoku University, Sendai 980-8577 Japan.
    Terekhina, Irina
    Department of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University, Stockholm 106 Sweden.
    Johnsson, Mats
    Department of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University, Stockholm 106 Sweden.
    Pettersson, Lars G.M.
    Department of Physics, Stockholm University, Stockholm 106 Sweden.
    Cornell, Ann M.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Salazar-Alvarez, German
    Department of Material Science and Engineering, Ångström Laboratory, Uppsala University, Box 35 751 03 Uppsala Sweden.
    Effect of pore mesostructure on the electrooxidation of glycerol on Pt mesoporous catalysts2023In: Journal of Materials Chemistry A, ISSN 2050-7488, E-ISSN 2050-7496, Vol. 11, no 31, p. 16570-16577Article in journal (Refereed)
    Abstract [en]

    Glycerol is a renewable chemical that has become widely available and inexpensive owing to the increased production of biodiesel. Noble metal materials are effective catalysts for the production of hydrogen and value-added products through the electrooxidation of glycerol. In this study, we developed three platinum systems with distinct pore mesostructures, e.g., hierarchical pores (HP), cubic pores (CP) and linear pores (LP), all with high electrochemically active surface area (ECSA). The ECSA-normalized GEOR catalytic activity of the systems follows HPC > LPC > CPC > commercial Pt/C. Regarding the oxidation products, we observe glyceric acid as the main three-carbon product (C3), with oxalic acids as the main two-carbon oxidation product. DFT-based theoretical calculations support the glyceraldehyde route going through tartronic acid towards oxalic acid and also help in understanding why the dihydroxyacetone (DHA) route is active despite the absence of DHA amongst the observed oxidation products.

  • 37.
    Anusuyadevi, Prasaanth Ravi
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Svagan, Anna Justina
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Role of cellular solids in heterogeneous photocatalytic applications2021In: Nanostructured Photocatalysts: From Fundamental to Practical Applications, Elsevier BV , 2021, p. 305-330Chapter in book (Other academic)
    Abstract [en]

    Heterogeneous photocatalysis exhibits the potential for the complete degradation of pollutants present in water or gas phase. The effective realization of heterogeneous photocatalysis, at both large-scale industrial setups for water treatment and in situ application for solar remediation of ecological units, can be achieved by the concurrent development of photocatalytic supports along with solid semiconductor materials targeted for implementation as photocatalysts. This chapter provides an update of such developments in the field of photocatalytic supports, very specifically, on cellular solid-based carriers (foams). In the first part, a brief introduction to the fundamentals of cellular solids is presented. Subsequently, the role of cellular solids, as structured photocatalytic supports, for implementation in large-scale, continuously processed photoreactors for high-throughput water treatment, are discussed. The second part of this chapter reports all the materials used, up-to-date, in the fabrication of cellular solid-based photocatalyst carriers for the real-time solar remediation of the natural system. Finally, this chapter ends up in the discussion of novel cellulose nanofiber-based nanofoams as buoyant photocatalytic supports for the realization of bio-based, nonmetallic, nontoxic floating photocatalysts.

  • 38. Aparicio, Francisco J.
    et al.
    Holgado, Miguel
    Borras, Ana
    Blaszczyk-Lezak, Iwona
    Griol, Amadeu
    Barrios, Carlos A.
    Casquel, Rafael
    Sanza, Francisco J.
    Sohlström, Hans
    KTH, School of Electrical Engineering (EES), Microsystem Technology.
    Antelius, Mikael
    KTH, School of Electrical Engineering (EES), Microsystem Technology.
    Gonzalez-Elipe, Agustin R.
    Barranco, Angel
    Transparent Nanometric Organic Luminescent Films as UV-Active Components in Photonic Structures2011In: Advanced Materials, ISSN 0935-9648, E-ISSN 1521-4095, Vol. 23, no 6, p. 761-765Article in journal (Refereed)
    Abstract [en]

    A new kind of visible-blind organic thin-film material, consisting of a polymeric matrix with a high concentration of embedded 3-hydroxyflavone (3HF) dye molecules, that absorbs UV light and emits green light is presented. The thin films can be grown on sensitive substrates, including flexible polymers and paper. Their suitability as photonic active components in photonic devices is demonstrated.

  • 39. Araujo, Rafael B.
    et al.
    Banerjee, Amitava
    Ahujati, Rajeev
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics. Uppsala University, Sweden.
    Divulging the Hidden Capacity and Sodiation Kinetics of NaxC6Cl4O2: A High Voltage Organic Cathode for Sodium Rechargeable Batteries2017In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 121, no 26, p. 14027-14036Article in journal (Refereed)
    Abstract [en]

    In the current emerging sustainable organic battery field, quinones are seen as one of the prime candidates for application in rechargeable battery electrodes. Recently, C6Cl4O2, a modified quinone, has been proposed as a high voltage organic cathode. However, the sodium insertion mechanism behind the cell reaction remained unclear due to the nescience of the right crystal structure. Here, the framework of the density functional theory (DFT) together with an evolutionary algorithm was employed to elucidate the crystal structures of the compounds NaxC6Cl4O2 (x = 0.5, 1.0, 1.5 and 2). Along with the usefulness of PBE functional to reflect the experimental potential, also the importance of the hybrid functional to divulge the hidden theoretical capacity is evaluated. We showed that the experimentally observed lower specific capacity is a result of the great stabilization of the intermediate phase Na1.5C6Cl4O2. The calculated activation barriers for the ionic hops, are 0.68, 0.40, and 0.31 eV, respectively, for NaC6Cl4O2, Na1.5C6Cl4O2, and Na2C6Cl4O2. These results indicate that the kinetic process must not be a limiting factor upon Na insertion. Finally, the correct prediction of the specific capacity has confirmed that the theoretical strategy used, employing evolutionary simulations together with the hybrid functional framework, can rightly model the thermodynamic process in organic electrode compounds.

  • 40. Araujo, Rafael B.
    et al.
    Banerjee, Amitava
    Panigrahi, Puspamitra
    Yang, Li
    Sjodin, Martin
    Stromme, Maria
    Araujo, C. Moyses
    Ahuja, Rajeev
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics. Uppsala Univ, Sweden.
    Assessing the electrochemical properties of polypyridine and polythiophene for prospective applications in sustainable organic batteries2017In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 19, no 4, p. 3307-3314Article in journal (Refereed)
    Abstract [en]

    Conducting polymers are being considered promising candidates for sustainable organic batteries mainly due to their fast electron transport properties and high recyclability. In this work, the key properties of polythiophene and polypyridine have been assessed through a combined theoretical and experimental study focusing on such applications. A theoretical protocol has been developed to calculate redox potentials in solution within the framework of the density functional theory and using continuous solvation models. Here, the evolution of the electrochemical properties of solvated oligomers as a function of the length of the chain is analyzed and then the polymer properties are estimated via linear regressions using ordinary least square. The predicted values were verified against our electrochemical experiments. This protocol can now be employed to screen a large database of compounds in order to identify organic electrodes with superior properties.

  • 41. Araujo, Rafael B.
    et al.
    Chakraborty, Sudip
    Barpanda, Prabeer
    Ahuja, Rajeev
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics. Condensed Matter Theory Group, Department of Physics and Astronomy, Uppsala University, Sweden.
    Na2M2(SO4)(3) (M = Fe, Mn, Co and Ni): towards high-voltage sodium battery applications2016In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 18, no 14, p. 9658-9665Article in journal (Refereed)
    Abstract [en]

    Sodium-ion-based batteries have evolved as excellent alternatives to their lithium-ion-based counterparts due to the abundance, uniform geographical distribution and low price of Na resources. In the pursuit of sodium chemistry, recently the alluaudite framework Na2M2(SO4)(3) has been unveiled as a high-voltage sodium insertion system. In this context, the framework of density functional theory has been applied to systematically investigate the crystal structure evolution, density of states and charge transfer with sodium ions insertion, and the corresponding average redox potential, for Na2M2(SO4)(3) (M = Fe, Mn, Co and Ni). It is shown that full removal of sodium atoms from the Fe-based device is not a favorable process due to the 8% volume shrinkage. The imaginary frequencies obtained in the phonon dispersion also reflect this instability and the possible phase transition. This high volume change has not been observed in the cases of the Co- and Ni-based compounds. This is because the redox reaction assumes a different mechanism for each of the compounds investigated. For the polyanion with Fe, the removal of sodium ions induces a charge reorganization at the Fe centers. For the Mn case, the redox process induces a charge reorganization of the Mn centers with a small participation of the oxygen atoms. The Co and Ni compounds present a distinct trend with the redox reaction occurring with a strong participation of the oxygen sublattice, resulting in a very small volume change upon desodiation. Moreover, the average deintercalation potential for each of the compounds has been computed. The implications of our findings have been discussed both from the scientific perspective and in terms of technological aspects.

  • 42.
    Araujo, Rafael B.
    et al.
    Stockholm Univ, AlbaNova Univ Ctr, FYSIKUM, SE-10691 Stockholm, Sweden..
    Martín-Yerga, Daniel
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry. Univ Warwick, Dept Chem, Coventry CV4 7AL, W Midlands, England..
    dos Santos, Egon Campos
    Stockholm Univ, AlbaNova Univ Ctr, FYSIKUM, SE-10691 Stockholm, Sweden..
    Cornell, Ann M.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Pettersson, Lars G. M.
    Stockholm Univ, AlbaNova Univ Ctr, FYSIKUM, SE-10691 Stockholm, Sweden..
    Elucidating the role of Ni to enhance the methanol oxidation reaction on Pd electrocatalysts2020In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 360, article id 136954Article in journal (Refereed)
    Abstract [en]

    Amongst promising available technologies enabling the transition to renewable energy sources, electrochemical oxidation of alcohols, in a direct fuel cell or in an electrolysis reaction (H-2 production), can be an economically and sustainable alternative to currently used technologies. In this work, we highlight the advantages of a Pd-Ni bimetallic electrocatalyst for methanol electrooxidation - a convenient choice due to the low cost of Ni combined with the observed acceptable catalytic performance of Pd. We report a synergistic effort between experiments and theoretical calculations based on density functional theory to provide an in-depth understanding - at the atomistic level - of the origin of the enhanced electrochemical activity of methanol electrooxidation using the bimetallic catalysts Pd3Ni and PdNi over pure Pd. Cyclic voltammograms and High-Performance Liquid Chromatography (HPLC) demonstrate higher activity towards methanol electrooxidation with increased Ni concentration and, furthermore, higher selectivity for CO2. These effects are understood by: 1) changes in the methanol oxidation reaction mechanism. 2) Mitigation or suppression of CO poisoning on the Pd-Ni alloys as compared to the pure Pd catalyst. 3) A stronger tendency towards highly oxidized intermediates for the alloys. These findings elucidate the effects of a bimetallic electrocatalyst for alcohol electrooxidation as well as unambiguously suggest PdNi as a more cost-effective alternative electrocatalyst.

  • 43.
    Ashour, Radwa M.
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Abdelhamid, Hani Nasser
    Abdel-Magied, Ahmed F.
    Abdel-Khalek, Ahmed A.
    Ali, M. M.
    Uheida, Abdusalam
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Muhammed, Mamoun
    Zou, Xiaodong
    Dutta, Joydeep
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Rare Earth Ions Adsorption onto Graphene Oxide Nanosheets2017In: Solvent extraction and ion exchange, ISSN 0736-6299, E-ISSN 1532-2262, Vol. 35, no 2, p. 91-103Article in journal (Refereed)
    Abstract [en]

    Graphene oxide (GO) was synthesized and used as a coagulant of rare earth elements (REEs) from aqueous solution. Stability and adsorption capacities were exhibited for target REEs such as La(III), Nd(III), Gd(III), and Y(III). The parameters influencing the adsorption capacity of the target species including contact time, pH, initial concentration, and temperature were optimized. The adsorption kinetics and thermodynamics were studied. The method showed quantitative recovery (99%) upon desorption using HNO3 acid (0.1 M) after a short contact time (15 min).

  • 44. Ata, S.
    et al.
    Pugh, Robert
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Jameson, G. J.
    The influence of interfacial ageing and temperature on the coalescence of oil droplets in water2011In: Colloids and Surfaces A: Physicochemical and Engineering Aspects, ISSN 0927-7757, E-ISSN 1873-4359, Vol. 374, no 1-3, p. 96-101Article in journal (Refereed)
    Abstract [en]

    Understanding the coalescence behaviour of two single droplets of industrial kerosene oil is an important precursor for predicting the stability of a concentrated kerosene emulsion system. In taking such an approach, distinct differences in the dynamic coalescence of fresh and aged binary droplets of analytical and technical grade kerosene was observed which we believe to be important with regard to the stability of concentrated systems. It was shown from induction time measurements (the time from first contact to rupture of the thin film separating the droplets) that the analytical grade kerosene binary droplets are considerable more stable than the technical grade at higher temperature (up to 65 degrees C) but the analytical grade shows a gradual decrease in stability up to 65 degrees C. At 75 degrees C, both grades of kerosene droplets remained stable to coalescence. After this initial rupture, coalescence proceeded as a series of dynamic oscillations and further insight into the fusion behaviour could be obtained by analysis of the change in the surface area of the aggregated droplets as a function of time. The longer induction times correlated with the more vigorous post rupture oscillations (less damping resulting from an increase in interfacial elasticity) which were recorded during the drop fusion. These experiments reveal preliminary steps in the coalescence of oil droplets where measurements from first contact to final damped equilibrium are quantified. This aspect of coalescence has not been well represented in the earlier literature. (C) 2010 Elsevier B.V. All rights reserved.

  • 45.
    Attarzadeh, Reza
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering.
    Attarzadeh-Niaki, Seyed-Hosein
    Shahid Beheshti Univ SBU, Fac Comp Sci & Engn, Tehran, Iran..
    Duwig, Christophe
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Process Technology.
    Multi-objective optimization of TPMS-based heat exchangers for low-temperature waste heat recovery2022In: Applied Thermal Engineering, ISSN 1359-4311, E-ISSN 1873-5606, Vol. 212, p. 118448-, article id 118448Article in journal (Refereed)
    Abstract [en]

    The transformation to a truly sustainable energy system will require taking better advantage of the waste heat. Integrating heat exchangers with the triply periodic minimal surface (TPMS) is a promising and efficient way to build waste heat recovery systems that harness heat emissions from the low pitch thermal systems. This is mainly due to the low hydrodynamic resistance and pressure drop in the TPMS while securing good heat transfer at low-temperature gradient. This study establishes a computational design and analysis of heat and mass transfer inside a heat exchanger based on the TPMS structure and determine thermal effectiveness, heat transfer coefficient, and pressure drop inside the channel. The non-linearity dependence of results to several design variables makes obtaining the optimal design configuration solely using conventional CFD or experimental study nearly impossible. Hence, a multi-objective optimization workflow based on a Genetic Algorithm for laminar flow is employed to reveal the underlying relationships between design variables for the optimal configurations. The results illustrate the local sensitivity of important parameters such as the heat transfer coefficient, Nusselt number, and thermal performance of the heat exchanger against various design variables. It is shown that the pressure drop is directly affected by gas inlet velocity, viscosity, and density, from high to low, respectively. The Pareto frontiers for the optimal thermal performance are extracted, and the correlation between design objectives is determined. This methodology provides a promising framework for heat exchangers' design analysis, including multi-objective goals and design constraints.

  • 46.
    Atwa, Mohamed M.
    et al.
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Alaskalany, Ahmed
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Elgammal, Karim
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics. KTH, Centres, SeRC - Swedish e-Science Research Centre.
    Smith, Anderson D.
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Hammar, Mattias
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Östling, Mikael
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Trilayer Graphene as a Candidate Material for Phase-Change Memory Applications2016In: MRS Advances, E-ISSN 2059-8521, Vol. 1, no 20, p. 1487-1494Article in journal (Refereed)
    Abstract [en]

    There is pressing need in computation of a universal phase change memory consolidating the speed of RAM with the permanency of hard disk storage. A potentiated scanning tunneling microscope tip traversing the soliton separating a metallic, ABA-stacked phase and a semiconducting ABC-stacked phase in trilayer graphene has been shown to permanently transform ABA-stacked regions to ABC-stacked regions. In this study, we used density functional theory (DFT) calculations to assess the energetics of this phase-change and explore the possibility of organic functionalization using s-triazine to facilitate a reverse phase-change from rhombohedral back to Bernal in graphene trilayers. A significant deviation in the energy per simulated atom arises when s-triazine is adsorbed, favoring the transformation of the ABC phase to the ABA phase once more. A phase change memory device utilizing rapid, energy-efficient, reversible, field-induced phase-change in graphene trilayers could potentially revolutionize digital memory industry.

  • 47.
    Atzori, Marco
    et al.
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics. Department of Particulate Flow Modelling, Johannes Kepler University, Linz, Austria.
    Chibbaro, Sergio
    Sorbonne Université, CNRS, UMR 7190, Institut Jean Le Rond d’Alembert, F-75005 Paris, France.
    Duwig, Christophe
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Process Technology.
    Brandt, Luca
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics. Department of Energy and Process Engineering, Norwegian University of Science and Technology (NTNU), Trondheim, Norway.
    LES and RANS calculations of particle dispersion behind a wall-mounted cubic obstacle2022In: International Journal of Multiphase Flow, ISSN 0301-9322, E-ISSN 1879-3533, Vol. 151, p. 104037-, article id 104037Article in journal (Refereed)
    Abstract [en]

    In the present paper, we evaluate the performances of three stochastic models for particle dispersion in the case of a three-dimensional turbulent flow. We consider the flow in a channel with a cubic wall-mounted obstacle, and perform large-eddy simulations (LESs) including passive particles injected behind the obstacle, for cases of low and strong inertial effects. We also perform Reynolds-averaged simulations of the same case, using standard turbulence models, and employ the two discrete stochastic models for particle dispersion implemented in the open-source code OpenFOAM and the continuous Lagrangian stochastic model proposed by Minier et al. (2004). The Lagrangian model is consistent with a Probability Density Function (PDF) model of the exact particle equations, and is based on the modelling of the fluid velocity seen by particles. This approach allows a consistent formulation which eliminates the spurious drifts flawing discrete models and to have the drag force in a closed form. The LES results are used as reference data both for the fluid RANS simulations and particle simulations with dispersion models. The present test case allows to evaluate the performance of dispersion models in highly non-homogeneous flow, and it used in this context for the first time. The continuous stochastic model generally shows a better agreement with the LES than the discrete stochastic models, in particular in the case of particles with higher inertia. 

  • 48.
    Augusto, Ohara
    et al.
    Univ Sao Paulo, Inst Quim, Dept Bioquim, BR-5508000 Sao Paulo, Brazil..
    Goldstein, Sara
    Hebrew Univ Jerusalem, Chem Inst, IL-91904 Jerusalem, Israel..
    Hurst, James K.
    Oregon State Univ, Dept Biochem & Biophys, Corvallis, OR 97331 USA..
    Lind, Johan
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH).
    Lymar, Sergei, V
    Brookhaven Natl Lab, Dept Chem, Upton, NY 11973 USA..
    Merényi, Gabor
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Radi, Rafael
    Univ Republica, Dept Bioquim, Fac Med, Montevideo 11800, Uruguay.;Univ Republica, Ctr Free Rad & Biomed Res, Fac Med, Montevideo 11800, Uruguay..
    Carbon dioxide-catalyzed peroxynitrite reactivity - The resilience of the radical mechanism after two decades of research2019In: Free Radical Biology & Medicine, ISSN 0891-5849, Vol. 135, p. 210-215Article, review/survey (Refereed)
    Abstract [en]

    Peroxynitrite, ONOO-, formed in tissues that are simultaneously generating NO center dot and O-2(center dot-), is widely regarded as a major contributor to oxidative stress. Many of the reactions involved are catalyzed by CO2 via formation of an unstable adduct, ONOOC(O)O-, that undergoes O-O bond homolysis to produce NO2 center dot and CO3 center dot- radicals, whose yields are equal at about 0.33 with respect to the ONOO- reactant. Since its inception two decades ago, this radical-based mechanism has been frequently but unsuccessfully challenged. The most recent among these [Serrano-Luginbuehl et al. Chem. Res. Toxicol. 31: 721-730; 2018] claims that ONOOC(O)O- is stable, predicts a yield of NO2 center dot/CO3 center dot- of less than 0.01 under physiological conditions and, contrary to widely accepted viewpoints, suggests that radical generation is inconsequential to peroxynitrite-induced oxidative damage. Here we review the experimental and theoretical evidence that support the radical model and show this recently proposed alternative mechanism to be incorrect.

  • 49. Baber, Ashleigh E.
    et al.
    Xu, Fang
    Dvorak, Filip
    Mudiyanselage, Kumudu
    Soldemo, Markus
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Weissenrieder, Jonas
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Senanayake, Sanjaya D.
    Sadowski, Jerzy T.
    Rodriguez, José A.
    Matolín, Vladimír
    White, Michael G.
    Stacchiola, Darío J.
    In Situ Imaging of Cu2O under Reducing Conditions: Formation of Metallic Fronts by Mass Transfer2013In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 135, no 45, p. 16781-16784Article in journal (Refereed)
    Abstract [en]

    Active catalytic sites have traditionally been analyzed based on static representations of surface structures and characterization of materials before or after reactions. We show here by a combination of in situ microscopy and spectroscopy techniques that, in the presence of reactants, an oxide catalyst's chemical state and morphology are dynamically modified. The reduction of Cu2O films is studied under ambient pressures (AP) of CO. The use of complementary techniques allows us to identify intermediate surface oxide phases and determine how reaction fronts propagate across the surface by massive mass transfer of Cu atoms released during the reduction of the oxide phase in the presence of CO. High resolution in situ imaging by AP scanning tunneling microscopy (AP-STM) shows that the reduction of the oxide films is initiated at defects both on step edges and the center of oxide terraces.

  • 50. Bacalum, Mihaela
    et al.
    Wang, Lina
    Boodts, Stijn
    Yuan, Peijia
    Leen, Volker
    Smisdom, Nick
    Fron, Eduard
    Knippenberg, Stefan
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Fabre, Gabin
    Trouillas, Patrick
    Beljonne, David
    Dehaen, Wim
    Boens, Noel
    Ameloot, Marcel
    A Blue-Light-Emitting BODIPY Probe for Lipid Membranes2016In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 32, no 14, p. 3495-3505Article in journal (Refereed)
    Abstract [en]

    Here we describe a new BODIPY-based membrane probe (1) that provides an alternative to dialkylcarbocyanine dyes, such as DiI-C,8, that can be excited in the blue spectral region. Compound 1 has unbranched octadecyl chains at the 3,5 -positions and a meso-amino function. In organic solvents, the absorption and emission maxima of 1 are determined mainly by solvent acidity and dipolarity. The fluorescence quantum yield is high and reaches 0.93 in 2-propanol. The fluorescence decays are well fitted with a single -exponential in pure solvents and in small and giant unilamellar vesicles (GUV) with a lifetime of ca. 4 ns. Probe 1 partitions in the same lipid phase as DiI-C-18(5) for lipid mixtures containing sphingomyelin and for binary mixtures of dipalmitoylphosphatidylcholine (DPPC) and dioleoylphosphatidylcholine (DOPC). The lipid phase has no effect on the fluorescence lifetime but influences the fluorescence anisotropy. The translational diffusion coefficients of 1 in GUVs and OLN-93 cells are of the same order as those reported for DiI-C-18. The directions of the absorption and transition dipole moments of 1 are calculated to be parallel. This is reflected in the high steady-state fluorescence anisotropy of 1 in high ordered lipid phases. Molecular dynamic simulations of 1 in a model of the DOPC bilayer indicate that the average angle of the transition moments with respect to membrane normal is ca. 70 degrees, which is comparable with the value reported for al DiI-C-18.

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