[article] Kemian tekniikan korkeakoulu / CHEM

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  • Simulation of electrochemical processes during oxygen evolution on Pb-MnO2 composite electrodes
    (2017) Schmachtel, Sönke; Murtomäki, Lasse; Aromaa, Jari; Lundström, Mari; Barker, Michael H.
     School of Chemical Technology | A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    The geometric properties of Pb-MnO2 composite electrodes are studied, and a general formula ispresented for the length of the triple phase boundary (TPB) on two dimensional (2D) compositeelectrodes using sphere packing and cutting simulations. The difference in the geometrical properties of2D (or compact) and 3D (or porous) electrodes is discussed. It is found that the length of the TPB is theonly reasonable property of a 2D electrode that follows a 1/r particle radius relationship. Subsequently,sphere packing cuts are used to derive a statistical electrode surface that is the basis for the earlierproposed simulations of different electrochemical mechanisms. It is shown that two of the proposedmechanisms (conductivity and a two-step-two-material kinetic mechanism) can explain the currentincrease at Pb-MnO2 anodes compared to standard lead anodes.The results show that although MnO2 has low conductivity, when combined with Pb as the metal matrix,the behaviour of the composite is not purely ohmic but is also affected by activation overpotentials,increasing the current density close to the TPB. Current density is inversely proportional to the radius ofthe catalyst particles, matching with earlier experimental results. Contrary to earlier SECM experiments,mass transport of sulphuric acid is not likely to have any influence, as confirmed with simulations.A hypothetical two-step-two-material mechanism with intermediate H2O2 that reacts on both the Pbmatrix and MnO2 catalyst is studied. It was found that assuming quasi-reversible generation of H2O2followed by its chemical decomposition on MnO2, results are obtained that agree with the experiments.If the quasi-reversible formation of H2O2 occurs near the peroxide decomposition catalyst, currentincreases, leading to an active TPB and to the current density that scales with 1/r. It is furtheremphasised that both the Pb matrix and MnO2 catalyst are necessary and their optimum ratio dependson the used current density. Yet, additional experimental evidence is needed to support the postulatedmechanism.
  • Superstructure-Dependent Loading of DNA Origami Nanostructures with a Groove-Binding Drug
    (2018) Kollmann, Fabian; Ramakrishnan, Saminathan; Shen, Boxuan; Grundmeier, Guido; Kostiainen, Mauri A.; Linko, Veikko; Keller, Adrian
     School of Chemical Technology | A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
  • Nanometrology and super-resolution imaging with DNA
    (2017) Graugnard, Elton; Hughes, William L.; Jungmann, Ralf; Kostiainen, Mauri A.; Linko, Veikko
     School of Chemical Technology | A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
  • Plasmonic nanostructures through DNA-assisted lithography
    (2018) Shen, Boxuan; Linko, Veikko; Tapio, Kosti; Pikker, Siim; Lemma, Tibebe; Gopinath, Ashwin; Gothelf, Kurt V.; Kostiainen, Mauri A.; Toppari, J. Jussi
     School of Science | A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Programmable self-assembly of nucleic acids enables the fabrication of custom, precise objects with nanoscale dimensions. These structures can be further harnessed as templates to build novel materials such as metallic nanostructures, which are widely used and explored because of their unique optical properties and their potency to serve as components of novel metamaterials. However, approaches to transfer the spatial information of DNA constructions to metal nanostructures remain a challenge. We report a DNA-assisted lithography (DALI) method that combines the structural versatility of DNA origami with conventional lithography techniques to create discrete, well-defined, and entirely metallic nanostructures with designed plasmonic properties. DALI is a parallel, high-throughput fabrication method compatible with transparent substrates, thus providing an additional advantage for optical measurements, and yields structures with a feature size of ~10 nm. We demonstrate its feasibility by producing metal nanostructures with a chiral plasmonic response and bowtie-shaped nanoantennas for surface-enhanced Raman spectroscopy. We envisage that DALI can be generalized to large substrates, which would subsequently enable scale-up production of diverse metallic nanostructures with tailored plasmonic features.
  • Experiments and modeling of fixed-bed debarking residue pyrolysis: The effect of fuel bed properties on product yields
    (2015) Boriouchkine, Alexandre; Sharifi, Vida; Swithenbank, Jim; Jämsä-Jounela, Sirkka-Liisa
     School of Chemical Technology | A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    This paper presents a study on the fixed-bed pyrolysis of debarking residue obtained from Norway spruce. Analysis is based on the dynamic model of packed bed pyrolysis which was calibrated by determining appropriate reaction rates and enthalpies to match the model predictions with the experimental data. The model comprises mass, energy and momentum equations coupled with a rate equation that describes both the primary and secondary pyrolysis reactions. The experiments used for the model calibration determined the yields of solid, liquid and gaseous pyrolysis products as well as their compositions at three distinct holding temperatures. Subsequently, the dynamic model was used to predict the product yields and to analyze the underlying phenomena controlling the overall pyrolysis reaction in a fixed-bed reactor.
  • A performance optimization algorithm for controller reconfiguration in fault tolerant distributed model predictive control
    (2015) Zakharov, Alexey; Zattoni, Elena; Yu, Miao; Jämsä-Jounela, Sirkka-Liisa
     School of Chemical Technology | A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    This paper presents a performance optimization algorithm for controller reconfiguration in fault tol-erant distributed model predictive control for large-scale systems. After the fault has been detectedand diagnosed, several controller reconfigurations are proposed as candidate corrective actions for faultcompensation. The solution of a set of constrained optimization problems with different actuator andsetpoint reconfigurations is derived by means of an original approach, exploiting the information onthe active constraints in the non-faulty subsystems. Thus, the global optimization problem is split intotwo optimization subproblems, which enable the online computational burden to be greatly reduced.Subsequently, the performances of different candidate controller reconfigurations are compared, andthe better performing one is selected and then implemented to compensate the fault effects. Efficacyof the proposed approach has been shown by applying it to the benzene alkylation process, which is abenchmark process in distributed model predictive control.
  • Protein Coating of DNA Nanostructures for Enhanced Stability and Immunocompatibility
    (2017) Auvinen, Henni; Zhang, Hongbo; Nonappa, Nonappa; Kopilow, Alisa; Niemelä, Elina H.; Nummelin, Sami; Correia, Alexandra; Santos, Hélder A.; Linko, Veikko; Kostiainen, Mauri A.
     School of Science | A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
  • A method for detecting non-stationary oscillations in process plants
    (2014) Tikkala, Vesa-Matti; Zakharov, Alexey; Jämsä-Jounela, Sirkka-Liisa
     School of Chemical Technology | A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    This paper proposes a method for detecting oscillations in non-stationary timeseries based on the statistical properties of zero-crossings. The main development presented is atechnique to remove non-stationary trend component from the analysed signals before applyingan oscillation detection procedure. First, the method extracts the signal's baseline that is utilizedto stationarize the signal. Then, an index describing the regularity of the stationarized signal'szero-crossings is computed in order to determine the presence of oscillation. The propertiesand performance of the method are analysed in simulation studies. Furthermore, the methodis comprehensively tested with industrial data in a comparative study in which the proposedmethod is tested against other oscillation detection methods using industrial benchmark dataand in tests on paperboard machine process. Finally, the simulation and industrial results areanalysed and discussed.
  • Toward energy efficiency through an optimized use of wood: The development of natural hydrophobic coatings that retain moisture-buffering ability
    (2015) Lozhechnikova, Alina; Vahtikari, Katja; Hughes, Mark; Österberg, Monika
     School of Chemical Technology | A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    The hygroscopicity of a wooden material or the ability to absorb, store and release moisture helps to naturally regulate the indoor climate by dampening humidity variations and avoiding extremes. This phenomenon, known as moisture buffering, is an energy-efficient way of moderating moisture levels in a living space, improving air quality, and influencing the health and comfort of the occupants. This work focused on developing a surface treatment that preserves the natural ability of timber to buffer moisture vapor whilst increasing the resistance to liquid water. For this purpose we suggest a method based on a natural non-continuous coating of hydrophobic Carnauba wax particles. The coating was compared, in terms of water repellency and moisture buffering efficiency, to a continuous wax film and conventional coating methods like lacquer and linseed oil. The resistance of the surfaces to liquid water was studied by Contact Angle measurement. Moisture Buffering experiments were conducted by exposing the surfaces to cyclic changes in relative humidity. It was found that coating with wax particles resulted in more hydrophobic surfaces with enhanced moisture buffering ability, whilst the rest of the coatings examined either reduced moisture buffering drastically (wax film, lacquer) or were not sufficiently hydrophobic (linseed oil).
  • Cationic polymers for DNA origami coating – examining their binding efficiency and tuning the enzymatic reaction rates
    (2016) Kiviaho, Jenny K.; Linko, Veikko; Ora, Ari; Tiainen, Tony; Järvihaavisto, Erika; Mikkilä, Joona; Tenhu, Heikki; Nonappa; Kostiainen, Mauri A.
     School of Science | A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
  • Automated design of DNA origami
    (2016) Linko, Veikko; Kostiainen, Mauri A.
     School of Chemical Technology | B1 Kirjoitus tieteellisessä aikakauslehdessä
  • DNA origami structures as calibration standards for nanometrology
    (2017) Korpelainen, Virpi; Linko, Veikko; Seppä, Jeremias; Lassila, Antti; Kostiainen, Mauri A
     School of Chemical Technology | A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
  • Cellular delivery of enzyme-loaded DNA origami
    (2016) Ora, Ari; Järvihaavisto, Erika; Zhang, Hongbo; Auvinen, Henni; Santos, Hélder A.; Kostiainen, Mauri A.; Linko, Veikko
     School of Chemical Technology | A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
  • DNA Nanostructures as Smart Drug-Delivery Vehicles and Molecular Devices
    (2015) Linko, Veikko; Ora, Ari; Kostiainen, Mauri A.
     School of Chemical Technology | A2 Katsausartikkeli tieteellisessä aikakauslehdessä
  • Dielectrophoretic trapping of multilayer DNA origami nanostructures and DNA origami-induced local destruction of silicon dioxide
    (2015) Shen, Boxuan; Linko, Veikko; Dietz, Hendrik; Toppari, J. Jussi
     School of Science | A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
  • Self-Assembly of Amphiphilic Janus Dendrimers into Mechanically Robust Supramolecular Hydrogels for Sustained Drug Release
    (2015) Nummelin, Sami; Liljeström, Ville; Saarikoski, Eve; Ropponen, Jarmo; Nykänen, Antti; Linko, Veikko; Seppälä, Jukka; Hirvonen, Jouni; Ikkala, Olli; Bimbo, Luis M.; Kostiainen, Mauri A.
     School of Science | A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
  • Virus-Encapsulated DNA Origami Nanostructures for Cellular Delivery
    (2014) Mikkilä, Joona; Eskelinen, Antti-Pekka; Niemelä, Elina H.; Linko, Veikko; Frilander, Mikko J.; Törmä, Päivi; Kostiainen, Mauri A.
     School of Science | A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
  • Custom-shaped metal nanostructures based on DNA origami silhouettes
    (2015) Shen, Boxuan; Linko, Veikko; Tapio, Kosti; Kostiainen, Mauri A.; Toppari, J. Jussi
     School of Chemical Technology | A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
  • A modular DNA origami-based enzyme cascade nanoreactor
    (2015) Linko, Veikko; Eerikäinen, Marika; Kostiainen, Mauri A.
     School of Science | A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
  • Metallic Nanostructures Based on DNA Nanoshapes
    (2016) Shen, Boxuan; Tapio, Kosti; Linko, Veikko; Kostiainen, Mauri A.; Toppari, J. Jussi
     School of Chemical Technology | A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä