Browsing by Author "Johansson, Leena-Sisko"

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  • Addition of Ascorbic Acid or Purified Kraft Lignin in Pulp Refining: Effects on Chemical Characteristics, Handsheet Properties, and Thermal Stability
    (2016-02) Vänskä, Emilia; Vihelä, Tuomas; Johansson, Leena-Sisko; Vuorinen, Tapani
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    The effects of two pulp pretreatments, impregnation with ascorbic acid (AA) or purified kraft lignin (KL), on bleached pulp refining were investigated by examining and testing handsheets made from these pulps. The AA pretreatment of the pulp amplified the depolymerization of the cellulose and notably impaired the strength properties of the pulp handsheets. The effects were enhanced upon the combination of the AA pretreatment and intensive refining. Furthermore, heat treatments (at 225 degrees C, 30 min, in water vapor atmospheres of 1 and 75% (v/v)) promoted the depolymerization of cellulose and the total color difference in the AA impregnated handsheets more than for the KL impregnated and reference handsheets. In contrast to AA, the KL pretreatment of the pulp improved the burst index stability of the refined pulp handsheets after the humid thermal treatment (75% (v/v)). In addition, the total color difference of the KL impregnated handsheets was lower than the AA impregnated and reference handsheets.
  • All-lignin approach to prepare cationic colloidal lignin particles: Stabilization of durable Pickering emulsions
    (2017) Sipponen, Mika; Smyth, Matthew; Leskinen, Timo; Johansson, Leena-Sisko; Österberg, Monika
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Surface modification of colloidal lignin particles (CLPs), which are obtained from renewable resources, is a plausible route towards novel biomaterials. Here we show that adsorption of cationic lignin onto spherical CLPs produces positively charged particles with tailored properties for the stabilization of Pickering emulsions. The threshold dosing of cationic lignin needed to achieve colloidally stable cationic dispersions was 4% relative to the dry weight of CLPs. Compared to irregular kraft lignin particles or regular CLPs, cationic CLPs stabilized a broader array of durable Pickering emulsions. This all-lignin adsorption process to prepare cationic CLPs is advantageous because it minimizes the consumption of synthetic polymers, and opens new application opportunities for structurally defined nano- and microscale lignin particles.
  • Assessing Fire-Damage in Historical Papers and Alleviating Damage with Soft Cellulose Nanofibers
    (2022-04) Völkel, Laura; Beaumont, Marco; Johansson, Leena-Sisko; Czibula, Caterina; Rusakov, Dmitrii; Mautner, Andreas; Teichert, Christian; Kontturi, Eero; Rosenau, Thomas; Potthast, Antje
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    The conservation of historical paper objects with high cultural value is an important societal task. Papers that have been severely damaged by fire, heat, and extinguishing water, are a particularly challenging case, because of the complexity and severity of damage patterns. In-depth analysis of fire-damaged papers, by means of examples from the catastrophic fire in a 17th-century German library, shows the changes, which proceeded from the margin to the center, to go beyond surface charring and formation of hydrophobic carbon-rich layers. The charred paper exhibits structural changes in the nano- and micro-range, with increased porosity and water sorption. In less charred areas, cellulose is affected by both chain cleavage and cross-linking. Based on these results and conclusions with regard to adhesion of auxiliaries, a stabilization method is developed, which coats the damaged paper with a thin layer of cellulose nanofibers. It enables the reliable preservation of the paper and—most importantly—retrieval of the contained historical information: the nanofibers form a flexible, transparent film on the surface and adhere strongly to the damaged matrix, greatly reducing its fragility, giving it stability, and enabling digitization and further handling.
  • Bioinspired lubricating films of cellulose nanofibrils and hyaluronic acid
    (2016-02-01) Valle-Delgado, Juan Jose; Johansson, Leena-Sisko; Österberg, Monika
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    The development of materials that combine the excellent mechanical strength of cellulose nanofibrils (CNF) with the lubricating properties of hyaluronic acid (HA) is a new, promising approach to cartilage implants not explored so far. A simple, solvent-free method to produce a very lubricating, strong cellulosic material by covalently attaching HA to the surface of CNF films is described in this work. A detailed analysis of the tribological properties of the CNF films with and without HA is also presented. Surface and friction forces at micro/nanoscale between model hard surfaces (glass microspheres) and the CNF thin films were measured using an atomic force microscope and the colloid probe technique. The effect of HA attachment, the pH and the ionic strength of the aqueous medium on the forces was examined. Excellent lubrication was observed for CNF films with HA attached in conditions where the HA layer was highly hydrated. These results pave the way for the development of new nanocellulose-based materials with good lubrication properties that could be used in biomedical applications. (C) 2015 Elsevier B.V. All rights reserved.
  • Clean and reactive nanostructured cellulose surface
    (2013-06) Österberg, Monika; Peresin, Maria S.; Johansson, Leena-Sisko; Tammelin, Tekla
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    A simple, solvent-free and low cost method to activate the surface of nanofibrillated cellulose films for further functionalization is presented. The method is based on the oxidative properties of UV radiation and ozone, to effectively remove contaminants from nanocellulosic surface, which remains clean and reactive for at least a week. The efficiency of the method is demonstrated by X-ray photoelectron spectroscopy and contact angle measurements. In clear contrast to previous results on nanoscaled cellulose the relative atomic concentration of non-cellulosic carbon atoms was only 4%, and water completely wetted the surface within seconds. After activation, neither chemical degradation nor morphological changes on cellulose were observed. This surface activation is essential for further functionalization of the film in dry state or nonpolar media. The surface activation was confirmed by silylation and a four times higher degree of substitution was achieved on the activated sample compared to non-activated reference film, as monitored with XPS.
  • Controlled diazonium electrodeposition towards a biosensor for C-reactive protein
    (2021) Gillan, Liam; Teerinen, Tuija; Johansson, Leena-Sisko; Smolander, Maria
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Electrografting of aryldiazonium species is useful for linkage between electrochemical transducer surface and biosensor recognition elements. However, the process proceeds uncontrollably to form branched/multilayer growth. This paper reports harnessing steric hindrance for controlled growth of aryldiazonium coupling agent during electrografting to screen-printed carbon electrode surface, which was subsequently used for linkage of CRP recognition elements to form a biosensor with greater sensitivity (32.0 ± 0.5 μA/(ng/mL) than that formed by way of uncontrolled growth (26.6. ± 5.3 μA/(ng/mL) across a highly sensitive operating range of 0.01–10 ng/mL. To the best of our knowledge, this is the first report of this approach demonstrated as a route for biosensor fabrication. This finding suggests the approach can be exploited in immunosensor assays.
  • Ceriumin kemiallisen tilan määrittäminen SrS:Ce-ohutkalvoissa röntgenfotoelektronispektrometrialla
    (1996) Sala, Hannele
     Helsinki University of Technology | Master's thesis
  • The effect of sodium isobutyl xanthate on galena and chalcopyrite flotation in the presence of dithionite ions
    (2021-08-01) Mhonde, Ngoni; Johansson, Leena-Sisko; Corin, Kirsten; Schreithofer, Nora
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Sulphoxy anions in recycled flotation process waters possess the potential to reduce the flotation efficacy of flotation reagents. In this study, dithionite ions and their interaction with thiol collectors in solution and the surface modifications of galena and chalcopyrite surfaces in the presence of dithionite ions were investigated. Microflotation tests, zeta potential tests, electrochemistry studies, solution xanthate degradation kinetics and surface analyses were carried out. Microflotation results showed a reduction in chalcopyrite and galena recoveries in dithionite solutions even in the presence of xanthate. Zeta potential and rest potential measurements showed that the potential determining effect of dithionites on the sulphide mineral surfaces (zeta potentials) and the solution (pulp potential), inherently decrease collector-mineral interactions. Xanthate degradation tests showed that more than half of the collector in solution was consumed in 10 min of reacting 20 mg/L of xanthate with 500 mg/L of dithionites. Surface analyses results also revealed that dithionites strongly influenced the chemical state of the sulphide minerals under investigation by producing oxidised sulphur species in the form of sulphites on the galena surface and oxidised iron species in the form of oxides and hydroxides on chalcopyrite. The current study presents a complete view of dithionite behaviours in plant waters by considering the dithionite-mineral surface interactions and dithionite-collector interactions in addition to the traditionally agreed on pulp potential alterations.
  • The Effect of Tetrathionate Ions on the Surface Chemistry and Flotation Response of Selected sulphide Minerals
    (2021-12-08) Mhonde, Ngoni; Johansson, Leena-Sisko; Corin, Kirsten; Schreithofer, Nora
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    This study investigated the impact of tetrathionate ions on selected sulfide mineral surfaces and their flotation response to tetrathionates using X-ray photoelectron spectroscopy (XPS), zeta potential and batch flotation studies and linking the results to previously reported electrochemistry, FTIR and microflotation studies. XPS revealed that tetrathionates have the propensity to oxidize minerals, changing the chemical composition of the mineral surface. This surface alteration renders the sulfide minerals hydrophilic through sulphoxy and hydroxy entities reducing collector adsorption as noted in FTIR and mixed potential studies. Zeta potentials showed little specific adsorption of tetrathionates on the sulfides except at moderately high concentrations, i.e., 1000 mg/L. Batch flotation showed that tetrathionates in solution depressed sulfide minerals, particularly galena, reducing its recovery to the concentrates in support of earlier microflotation results.
  • Evolution of carbon nanostructure during pyrolysis of homogeneous chitosan-cellulose composite fibers
    (2021-11-15) Zahra, Hilda; Sawada, Daisuke; Kumagai, Shogo; Ogawa, Yu; Johansson, Leena-Sisko; Ge, Yanling; Guizani, Chamseddine; Yoshioka, Toshiaki; Hummel, Michael
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Chitosan-cellulose composite fibers spun using a Lyocell technology are characterized by a homogeneous distribution and a close packing of the two biopolymers inside the fibrous matrix. Due to the intimate contact of cellulose and chitosan, synergistic effects can be observed during the pyrolysis of the composite fibers. In this study, the catalytic role of chitosan in altering the cellulose pyrolysis pathway in the composite fibers at moderate treatment temperatures up to 900 °C is confirmed. Analyses of the evolved gases during pyrolysis revealed that chitosan promoted cellulose dehydration and substantially decreased the formation of levoglucosan, explaining the higher char yield. The enhanced dehydration reaction is associated with the formation of intermolecular crosslinks due to the incorporation of nitrogen from chitosan in the resulting carbon structures. Nitrogen could also contribute to the in-plane disorder in the aromatic clusters when the pyrolysis is carried out at 500–700 °C, although the in-plane disorder is less noticeable from 700 to 900 °C. Nevertheless, the size of the aromatic cluster continues to grow when the composite fibers are pyrolyzed in a temperature range of 500–900 °C.
  • Hydrophobization of the Man-Made Cellulosic Fibers by Incorporating Plant-Derived Hydrophobic Compounds
    (2021-04-05) Moriam, Kaniz; Rissanen, Marja; Sawada, Daisuke; Altgen, Michael; Johansson, Leena-Sisko; Evtyugin, Dmitry Victorovitch; Guizani, Chamseddine; Hummel, Michael; Sixta, Herbert
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    The cellulosic fiber-based sustainable textile industry needs greener alternatives to the existing hydrophobization approaches—which are essentially based on nonrenewable and expensive hydrophobizing agents and adversely impact the environment. Herein, we report the production of novel hydrophobic cellulose based fibers produced by incorporating nature-derived hydrophobic additives—betulin (BE) and betulinic acid (BA) using the Ioncell technology. The incorporation process is simple and does not require any additional step during dry-jet wet spinning. Spinning dopes containing up to 10 wt % BE and BA were spinnable and the spun fibers (10BE and 10BA) maintained their mechanical properties. Compared to BE, BA-incorporated fiber showed homogeneous surface morphology suggesting the increased compatibility of BA with cellulose. Consequently, in contrast to BE-incorporated fibers, BA-incorporated fibers demonstrated higher yarn spinnability. Both 10BE and 10BA fibers showed hydrophobicity (water contact angle >90°) in the produced nonwovens and yarns. In summary, we developed a system for hydrophobizing man-made cellulose fiber via a simple eco-friendly and cost-effective way, which has potential for scalability and industrial applications.
  • Layer-by-layer assembled hydrophobic coatings for cellulose nanofibril films and textiles, made of polylysine and natural wax particles
    (2017) Forsman, Nina; Lozhechnikova, Alina; Khakalo, Alexey; Johansson, Leena-Sisko; Vartiainen, Jari; Österberg, Monika
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Herein we present a simple method to render cellulosic materials highly hydrophobic while retaining their breathability and moisture buffering properties, thus allowing for their use as functional textiles. The surfaces are coated via layer-by-layer deposition of two natural components, cationic poly-l-lysine and anionic carnauba wax particles. The combination of multiscale roughness, open film structure, and low surface energy of wax colloids, resulted in long-lasting superhydrophobicity on cotton surface already after two bilayers. Atomic force microscopy, interference microscopy, scanning electron microscopy and X-ray photoelectron spectroscopy were used to decouple structural effects from changes in surface energy. Furthermore, the effect of thermal annealing on the coating was evaluated. The potential of this simple and green approach to enhance the use of natural cellulosic materials is discussed.
  • Lignin-Based Porous Supraparticles for Carbon Capture
    (2021-04-27) Zhao, Bin; Borghei, Maryam; Zou, Tao; Wang, Ling; Johansson, Leena-Sisko; Majoinen, Johanna; Sipponen, Mika H.; Österberg, Monika; Mattos, Bruno D.; Rojas, Orlando J.
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Multiscale carbon supraparticles (SPs) are synthesized by soft-templating lignin nano- and microbeads bound with cellulose nanofibrils (CNFs). The interparticle connectivity and nanoscale network in the SPs are studied after oxidative thermostabilization of the lignin/CNF constructs. The carbon SPs are formed by controlled sintering during carbonization and develop high mechanical strength (58 N·mm-3) and surface area (1152 m2·g-1). Given their features, the carbon SPs offer hierarchical access to adsorption sites that are well suited for CO2 capture (77 mg CO2·g-1), while presenting a relatively low pressure drop (∼33 kPa·m-1 calculated for a packed fixed-bed column). The introduced lignin-derived SPs address the limitations associated with mass transport (diffusion of adsorbates within channels) and kinetics of systems that are otherwise based on nanoparticles. Moreover, the carbon SPs do not require doping with heteroatoms (as tested for N) for effective CO2 uptake (at 1 bar CO2 and 40 °C) and are suitable for regeneration, following multiple adsorption/desorption cycles. Overall, we demonstrate porous SP carbon systems of low cost (precursor, fabrication, and processing) and superior activity (gas sorption and capture).
  • Maskless, High-Precision, Persistent, and Extreme Wetting-Contrast Patterning in an Environmental Scanning Electron Microscope
    (2016) Liimatainen, Ville; Shah, Ali; Johansson, Leena-Sisko; Houbenov, Nikolay; Zhou, Quan
     School of Electrical Engineering | A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
  • Mild alkaline separation of fiber bundles from eucalyptus bark and their composites with cellulose acetate butyrate
    (2021-07) Dou, Jinze; Karakoç, Alp; Johansson, Leena-Sisko; Hietala, Sami; Evtyugin, Dmitry; Vuorinen, Tapani
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    High surface lignin content (i.e. 34.6 %) sclerenchyma fiber bundles were successfully isolated with a yield of 71 % by a mild alkali (NaOH dosage of 5 wt%) extraction of eucalyptus (Eucalyptus globulus) bark under 100 °C for 60 min. The mechanical properties of the composites prepared by hot pressing of cellulose acetate butyrate (CAB) sheets with the fiber bundles were evaluated. The fiber bundles exhibited good compatibility with CAB due to their hydrophobic fiber surfaces. The mechanical properties of the fiber bundle/ cellulose acetate butyrate composites revealed the maximum at a weight ratio of 25:75, which demonstrates the promise of utilizing these isotropic aligned fiber bundles as the reinforcement to the cellulose acetate butyrate without the addition of plasticizers for composite uses.
  • Nanodiamonds on tetrahedral amorphous carbon significantly enhance dopamine detection and cell viability
    (2017) Peltola, Emilia; Wester, Niklas; Holt, Katherine B.; Johansson, Leena-Sisko; Koskinen, Jari; Myllymäki, Vesa; Laurila, Tomi
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    We hypothesize that by using integrated carbon nanostructures on tetrahedral amorphous carbon (ta-C), it is possible to take the performance and characteristics of these bioelectrodes to a completely new level. The integrated carbon electrodes were realized by combining nanodiamonds (NDs) with ta-C thin films coated on Ti-coated Si-substrates. NDs were functionalized with mixture of carboxyl and amine groups NDandante or amine NDamine, carboxyl NDvox or hydroxyl groups NDH and drop-casted or spray-coated onto substrate. By utilizing these novel structures we show that (i) the detection limit for dopamine can be increased by two orders of magnitude [from 10 µM to 50 nM] in comparison to ta-C thin film electrodes and (ii) the coating method significantly affects electrochemical properties of NDs and (iii) the ND coatings selectively promote cell viability. NDandante and NDH showed most promising electrochemical properties. The viability of human mesenchymal stem cells and osteoblastic SaOS-2 cells was increased on all ND surfaces, whereas the viability of mouse neural stem cells and rat neuroblastic cells was improved on NDandante and NDH and reduced on NDamine and NDvox. The viability of C6 cells remained unchanged, indicating that these surfaces will not cause excess gliosis. In summary, we demonstrated here that by using functionalized NDs on ta-C thin films we can significantly improve sensitivity towards dopamine as well as selectively promote cell viability. Thus, these novel carbon nanostructures provide an interesting concept for development of various in vivo targeted sensor solutions.
  • Occurrence of Reverse Side Effects in Corona Treatment of Dispersion-coated Paperboard and its Influence on Grease Barrier Properties
    (2016) Ovaska, Sami-Seppo; Rinkunas, Ringaudas; Lozovksi, Tadeusz; Maldzius, Robertas; Sidaravicius, Jonas; Johansson, Leena-Sisko; Österberg, Monika; Backfolk, Kaj
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    The uncoated side of dispersion-barrier-coated paperboards was exposed to positive and negative direct current corona treatments in order to confirm the occurrence of backside treatment and clarify its effects on the usability of the paperboard. The main component of the coating dispersions was hydroxypropylated potato starch and the effects of talc and styrene-butadiene latex additions on backside treatment were evaluated. Coatings with a high talc proportion showed excellent initial grease resistance, but corona-induced strikethroughs caused a drastic decrease in grease penetration time. The root-mean-square roughness measurements revealed moderate surface roughening at the backside, indicating thus backside treatment. The alterations in surface free energies and rapeseed oil contact angles confirmed the occurrence of backside treatment. The high polarization potential of latex played a key role in these observations. At the same time, the inertity of talc had a stabilizing effect but it did not prevent backside treatment completely. X-ray photoelectron spectroscopy results verified that backside treatment occurs also when the barrier-coated side of the substrate is treated with corona, indicating that a dispersion coating layer does not prevent this undesired phenomenon. Bearing in mind that expressing customized information or including personalized elements in food packages or disposable cups and plates is under great interest, it can be assumed the exposure of packaging materials to corona will become more common in the near future, and the need for optimizing bio-based packaging materials for such purposes is obvious.
  • Open coating with natural wax particles enables scalable, non-toxic hydrophobation of cellulose-based textiles
    (2020-01-01) Forsman, Nina; Österberg, Monika; Johansson, Leena-Sisko; Kääriäinen, Pirjo; Tuure, Matilda; Koivula, Hanna
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Environmental benign cellulosic textiles are hampered by their tendency to absorb water, which restricts their use in functional clothing. Herein we describe a method to functionalize textile surfaces using thin, open coatings based on natural wax particles and natural polymers rendering cellulosic fabrics water-repellent while retaining their feel and breathability. The impact of curing temperature, cationic polymer and fabric properties on wetting and long-term water-repellency were studied using contact angle measurements and scanning electron microscopy. The wetting properties were correlated to roughness of the textiles using white light interferometer. X-ray photoelectron spectroscopy revealed the surface chemical composition, leading to fundamental understanding of the effect of annealing on the wax layer. Breathability was evaluated by water vapor permeability. The optimal curing temperature was 70 °C. The developed coating performed well on different natural textiles, and better than commercial alternatives. A set of garment prototypes were produced using the coating.
  • Single Walled Carbon Nanotube network - Tetrahedral Amorphous Carbon composite film
    (2015) Iyer, Ajai; Kaskela, Antti; Johansson, Leena-Sisko; Liu, Xuwen; Kauppinen, Esko I.; Koskinen, Jari
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
  • Surface functionalization of nanofibrillated cellulose using click-chemistry approach in aqueous media
    (2011) Pahimanolis, Nikolaos; Hippi, Ulla; Johansson, Leena-Sisko; Saarinen, Tapio; Houbenov, Nikolay; Ruokolainen, Janne; Seppälä, Jukka
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä