Browsing by Author "Johansson, Leena Sisko"

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Antibacterial effects of wood structural components and extractives from pinus sylvestris and picea abies on methicillin-resistant Staphylococcus aureus and Escherichia coli O157
(2017-11-01) Vainio-Kaila, Tiina; Zhang, Xue; Hänninen, Tuomas; Kyyhkynen, Aino; Johansson, Leena Sisko; Willför, Stefan; Österberg, Monika; Siitonen, Anja; Rautkari, Lauri
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Antibacterial properties of wood structural components and extractives were investigated against methicillin-resistant Staphylococcus aureus (MRSA) and Escherichia coli O157:H7 by placing bacterial inoculum on the model surfaces and incubating them for 2, 4, and 24 h. After incubation, the amount of viable bacteria on the surfaces was studied. The film coverage and thickness were evaluated with atomic-force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). The extracts were analyzed with gas chromatography-mass spectrometry (GC-MS). The results showed that films fully covered the glass surfaces. The XPS results confirmed the analysis of GC-MS, which revealed more similarities between the extractives of pine heartwood and spruce heartwood than between pine heartwood and pine sapwood. Only the pine heartwood extract showed an antibacterial effect against E. coli O157:H7. In contrast, MRSA was susceptible to all of the extracts and milled wood lignin (MWL).
Antimicrobial Colloidal Silver-Lignin Particles via Ion and Solvent Exchange
(2019-09-16) Lintinen, Kalle; Luiro, Sanna; Figueiredo, Patrícia; Sakarinen, Ekaterina; Mousavi, Zekra; Seitsonen, Jani; Rivière, Guillaume N.S.; Mattinen, Ulriika; Niemelä, Matti; Tammela, Päivi; Österberg, Monika; Johansson, Leena Sisko; Bobacka, Johan; Santos, Hélder A.; Kostiainen, Mauri A.
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Acid-precipitated lignin nanoparticles with a cationic polymer coating exhibit antibacterial activity when infused with silver. While the use of such particles would be beneficial due to their high antibacterial activity with a low silver content, their production holds steps that are difficult to scale up to inexpensive industrial manufacture. For example, the production of acid-precipitated lignin nanoparticles requires the use of ethylene glycol, which is not easily recycled. Furthermore, the binding of silver to these particles is weak, and thus the particles need to be used rapidly after preparation. Here, we show that with a deprotonation reaction of an organic solution of anhydrous lignin and subsequent ion exchange with silver nitrate and colloid formation by solvent exchange, highly spherical silver carboxylate colloidal lignin particles (AgCLPs) can be prepared. Silver is not released from the particles in deionized water but can be released in physiological conditions, shown by their high antibacterial efficacy with low silver loading. In comparison to lignin nanoparticles with weakly bound silver, AgCLPs have high antibacterial activity even without cationic polyelectrolyte coating, and they retain their antibacterial activity for days. While the rapid depletion of silver from silver-infused lignin nanoparticles can be considered beneficial for some applications, the sustained antibacterial activity of the AgCLPs with ionically bound silver will enable their use in applications where silver nanoparticles have been previously used. Our results demonstrate that CLPs, which can be produced with a closed cycle process on a large scale, can be rapidly and quantitatively functionalized into active materials.
Cellulose carbamate derived cellulose thin films: preparation, characterization and blending with cellulose xanthate
(2019-08-15) Weißl, Michael; Hobisch, Mathias Andreas; Johansson, Leena Sisko; Hettrich, Kay; Kontturi, Eero; Volkert, Bert; Spirk, Stefan
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Cellulose carbamate (CC) was employed as a water-soluble precursor in the manufacturing of cellulose based thin films using the spin coating technique. An intriguing observation was that during spin coating of CC from alkaline aqueous solutions, regeneration to cellulose was accomplished without the addition of any further chemicals. After rinsing, homogeneous thin films with tunable layer thickness in a range between 20 and 80 nm were obtained. Further, CC was blended with cellulose xanthate in different ratios (3:1, 1:1, 1:3) and after regeneration the properties of the resulting all-cellulose blend thin films were investigated. We could observe some slight indications of phase separation by means of atomic force microscopy. The layer thickness of the blend thin films was nearly independent of the ratio of the components, with values between 50 and 60 nm for the chosen conditions. The water uptake capability (80–90% relative to the film mass) determined by H2O/D2O exchange in a quartz crystal microbalance was independent of the blend ratio.
Cellulose-cyclodextrin co-polymer for the removal of cyanotoxins on water sources
(2019-12-01) Gomez-Maldonado, Diego; Erramuspe, Iris Beatriz Vega; Filpponen, Ilari; Johansson, Leena Sisko; Lombardo, Salvatore; Zhu, Junyong; Thielemans, Wim; Peresin, Maria S.
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
With increasing global water temperatures and nutrient runoff in recent decades, the blooming season of algae lasts longer, resulting in toxin concentrations that exceed safe limits for human consumption and for recreational use. From the different toxins, microcystin-LR has been reported as the main cyanotoxin related to liver cancer, and consequently its abundance in water is constantly monitored. In this work, we report a methodology for decorating cellulose nanofibrils with β-cyclodextrin or with poly(β-cyclodextrin) which were tested for the recovery of microcystin from synthetic water. The adsorption was followed by Quartz Crystal Microbalance with Dissipation monitoring (QCM-D), allowing for real-time monitoring of the adsorption behavior. A maximum recovery of 196 mg/g was obtained with the modified by cyclodextrin. Characterization of the modified substrate was confirmed with Fourier Transform Infrared Spectroscopy (FT-IR), X-ray Photoelectron Spectroscopy (XPS), Thermogravimetric Analysis (TGA), and Atomic Force Microscopy (AFM).
Co-exfoliation and fabrication of graphene based microfibrillated cellulose composites-mechanical and thermal stability and functional conductive properties
(2018-05-28) Phiri, Josphat; Johansson, Leena Sisko; Gane, Patrick; Maloney, Thad C.
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
The excellent functional properties of graphene and micro-nanofibrillated cellulose (MNFC) offer plenty of possibilities for wide ranging applications in combination as a composite material. In this study, flexible graphene/microfibrillated cellulose (MFC) composite films were prepared by a simple method of co-exfoliation of graphite in an MFC suspension by high-shear exfoliation. We show that pristine graphene, without any chemical treatment, was homogeneously dispersed in the MFC matrix, and the produced composites showed enhanced thermal, electrical and mechanical properties compared to a non-co-exfoliated control. The film properties were studied by XPS, XRD, Raman, SEM, FTIR, TGA, nitrogen sorption, UV-vis spectroscopy, optical and formation analysis tests. At 0.5 wt% loading, the specific surface area of graphene/MFC composites increased from 218 to 273 m2 g-1 while the tensile strength and Young's modulus for the graphene/MFC composites increased by 33% and 28% respectively. Thermal stability was enhanced by 22% at 9 wt% loading and the composites showed a high electrical conductivity of 2.4 S m-1. This simple method for the fabrication of graphene/MFC composites with enhanced controlled functional properties can prove to be industrially beneficial, and is expected to open up a new route for novel potential applications of materials based largely on renewable resources.
A comparative study of mechanical, thermal and electrical properties of graphene-, graphene oxide- and reduced graphene oxide-doped microfibrillated cellulose nanocomposites
(2018-08-15) Phiri, Josphat; Johansson, Leena Sisko; Gane, Patrick; Maloney, Thad
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Micro-nanofibrillated cellulose (MFC/NFC) and graphene-based composites are interesting materials due to their complementary functional properties, opening up potential in a variety of applications. Graphene, graphene oxide (GO) and reduced graphene oxide (RGO) were used in this comparative study as reinforcement functional fillers for the fabrication of multifunctional MFC nanocomposites using a simple aqueous dispersion based mixing method. The MFC composites showed different properties depending on the type of filler used. Graphene was seen to agglomerate and was poorly dispersed in the MFC matrix, whilst GO and RGO were homogeneously dispersed due to the presence of functional groups that promoted a strong interfacial molecular interaction between the filler and the MFC matrix. At 0.6 wt% filler loading, the tensile strength for MFC/GO and MFC/RGO increased by 17 % and 22 %, respectively, whilst the Young's modulus increased from 18 GPa to 21 GPa and 25 GPa, respectively. Compared to the neat MFC, addition of 5 wt% of graphene enhanced the thermal stability by 5 % and whilst with the addition of GO and RGO stability increased by 2 and 3 %, respectively. Graphene/MFC and RGO/MFC showed a high electrical conductivity of 1.7 S m-1 and 0.5 S m-1, respectively while the GO reinforced composites were insulators.
Comparison of conventional and lignin-rich microcrystalline cellulose
(2016-05-01) Vanhatalo, Kari; Maximova, Natalia; Perander, Anna Maija; Johansson, Leena Sisko; Haimi, Eero; Dahl, Olli
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Three microcrystalline cellulose (MCC) samples were manufactured from bleached and unbleached softwood kraft pulp, and their properties were compared to those of the commercial MCC, Avicel PH-101. One of the produced samples retained a large portion of lignin (10.3%), while the two others retained only some. The physical, chemical, thermogravimetric, and molecular properties were analyzed. The presence of lignin caused a substantial effect on the thermogravimetric and chemical properties of the MCC, as well as on its surface characteristics. The lignin-containing sample degraded at lower temperatures, and its UV Raman spectra had a high intensity aromatic band (1600 cm-1) arising from the lignin. X-ray photoelectron spectroscopy confirmed a high surface lignin coverage (40%) in this specimen only. Particle size and BET surface area measurement results varied in some limits between MCCs, while the cellulose crystallinity index showed almost equal values between 0.82 and 0.84. This work introduces a new wood-based product, the lignin-containing MCC, comparable in properties to the wide-marketed Avicel.
Control of the size of silver nanoparticles and release of silver in heat treated SiO2-Ag composite powders
(2018-01-05) Granbohm, Henrika; Larismaa, Juha; Ali, Saima; Johansson, Leena Sisko; Hannula, Simo Pekka
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
The growth of silver nanoparticles, the activation energy for silver particle growth, and the release of silver species in heat treated SiO2-Ag composite powders are investigated. The silver particle growth is controlled by heat treatment for 75 min of the as-synthesized SiO2-Ag composite powder at 300-800 °C. During heat treatment the mean size of the Ag particles increases from 10 nm up to 61 nm with increasing temperature, however, the particle size distribution widens and the mean size increases with increasing heat treatment temperature. Based on X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) studies, silver particles are crystalline and in a metallic state after annealing in all SiO2-Ag composite powders. The growth of Ag particles is suggested to take place via diffusion and Ostwald ripening. The activation energy for particle growth was determined as 0.14 eV. The dissolution of silver in aqueous solutions from the SiO2-Ag composites heat treated, at 300 °C, 600 °C, and 700 °C, was investigated by varying pH and temperature. The dissolution was reduced in all conditions with increasing silver particle size, i.e., when the total surface area of Ag particles is reduced. It is suggested that the dissolution of silver from the composite powders can conveniently be adjusted by controlling the Ag particle size by the heat treatment of the composite powder.
Core-Selective Silver-Doping of Gold Nanoclusters by Surface-Bound Sulphates on Colloidal Templates: From Synthetic Mechanism to Relaxation Dynamics
(2023-01-04) Chandra, Sourov; Sciortino, Alice; Shandilya, Shruti; Fang, Lincan; Chen, Xi; Nonappa; Jiang, Hua; Johansson, Leena Sisko; Cannas, Marco; Ruokolainen, Janne; Ras, Robin H.A.; Messina, Fabrizio; Peng, Bo; Ikkala, Olli
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Ultra-small luminescent gold nanoclusters (AuNCs) have gained substantial interest owing to their low photobleaching and high biocompatibility. While the substitution of silver for gold at the central core of AuNCs has shown significant augmentation of photoluminescence with enhanced photostability, selective replacement of the central atom by silver is, however, energetically inhibited. Herein, a new strategy for in situ site-selective Ag-doping exclusively at the central core of AuNCs using sulphated colloidal surfaces as the templates is presented. This approach exceedingly improves the photoluminescence quantum efficiency of AuNCs by eliminating nonradiative losses in the multi-step relaxation cascade populating the emissive state. Density functional theory predicts the mechanism of specific doping at the central core, endorsing the preferential bonding between Ag+ ions and sulphates in water. Finally, the generic nature of the templating concept to allow core-specific doping of nanoclusters is unraveled.
Dehydroabietylamine-Based Cellulose Nanofibril Films: A New Class of Sustainable Biomaterials for Highly Efficient, Broad-Spectrum Antimicrobial Effects
(2019-03-04) Hassan, Ghada; Forsman, Nina; Wan, Xing; Keurulainen, Leena; Bimbo, Luis M.; Johansson, Leena Sisko; Sipari, Nina; Yli-Kauhaluoma, Jari; Zimmermann, Ralf; Stehl, Susanne; Werner, Carsten; Saris, Per E.J.; Österberg, Monika; Moreira, Vânia M.
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
The design of antimicrobial surfaces as integral parts of advanced biomaterials is nowadays a high research priority, as the accumulation of microorganisms on surfaces inflicts substantial costs on the health and industry sectors. At present, there is a growing interest in designing functional materials from polymers abundant in nature, such as cellulose, that combine sustainability with outstanding mechanical properties and economic production. There is also the need to find suitable replacements for antimicrobial silver-based agents due to environmental toxicity and spread of resistance to metal antimicrobials. Herein we report the unprecedented decoration of cellulose nanofibril (CNF) films with dehydroabietylamine 1 (CNF-CMC-1), to give an innovative contact-active surface active against Gram-positive and Gram-negative bacteria including the methicillin-resistant S. aureus MRSA14TK301, with low potential to spread resistance and good biocompatibility, all achieved with low surface coverage. CNF-CMC-1 was particularly effective against S. aureus ATCC12528, causing virtually complete reduction of the total cells from 10 5 colony forming units (CFU)/mL bacterial suspensions, after 24 h of contact. This gentle chemical modification of the surface of CNF fully retained the beneficial properties of the original film, including moisture buffering and strength, relevant in many potential applications. Our originally designed surface represents a new class of ecofriendly biomaterials that optimizes the performance of CNF by adding antimicrobial properties without the need for environmentally toxic silver.
Electrically Conductive Thin Films Based on Nanofibrillated Cellulose : Interactions with Water and Applications in Humidity Sensing
(2020-08-12) Solin, Katariina; Borghei, Maryam; Sel, Ozlem; Orelma, Hannes; Johansson, Leena Sisko; Perrot, Hubert; Rojas, Orlando J.
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
TEMPO-oxidized cellulose nanofibrils (TOCNF) and oxidized carbon nanotubes (CNT) were used as humidity-responsive films and evaluated using electroacoustic admittance (quartz crystal microbalance with impedance monitoring, QCM-I) and electrical resistivity. Water uptake and swelling phenomena were investigated in a range of relative humidity (% RH) between 30 and 60% and temperatures between 25 and 50 °C. The presence of CNT endowed fibril networks with high water accessibility, enabling fast and sensitive response to changes in humidity, with mass gains of up to 20%. The TOCNF-based sensors became viscoelastic upon water uptake, as quantified by the Martin-Granstaff model. Sensing elements were supported on glass and paper substrates and confirmed a wide window of operation in terms of cyclic % RH, bending, adhesion, and durability. The electrical resistance of the supported films increased by ∼15% with changes in % RH from 20 to 60%. The proposed system offers a great potential to monitor changes in smart packaging.
From vapour to gas: Optimising cellulose degradation with gaseous HCl
(2018-06-01) Pääkkönen, Timo; Spiliopoulos, Panagiotis; Knuts, Aaro; Nieminen, Kaarlo; Johansson, Leena Sisko; Enqvist, Eric; Kontturi, Eero
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
A cellulose degradation technique utilizing a pressurized HCl gas (up to 100 kPa) device is introduced. High pressure HCl quickly degraded cellulose in purified cotton linters, reaching the so-called levelling-off degree of polymerisation (LODP) in less than 1.5 h. LODP marks the point where the disordered portions of cellulose microfibrils have been degraded and only the crystalline portions remain, generally signalling the end of cellulose degradation unless remarkably high concentrations are used. In the present high pressure system, however, continued hydrolysis following the LODP was detected by incremental release of sugars from the hydrolysate after its exposure to water, supposedly caused by erosion from the cellulose crystallite ends. With minimal water consumption and the ease of recycling the gaseous acid, the technique could be a potential candidate for pre-treatment considering the future production of cellulose nanomaterials, particularly cellulose nanocrystals.
Gold Au(I)6 Clusters with Ligand-Derived Atomic Steric Locking: Multifunctional Optoelectrical Properties and Quantum Coherence
(2023-04-18) Chandra, Sourov; Sciortino, Alice; Das, Susobhan; Ahmed, Faisal; Jana, Arijit; Roy, Jayoti; Li, Diao; Liljeström, Ville; Jiang, Hua; Johansson, Leena Sisko; Chen, Xi; Nonappa; Cannas, Marco; Pradeep, Thalappil; Peng, Bo; Ras, Robin H.A.; Sun, Zhipei; Ikkala, Olli; Messina, Fabrizio
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
An atomically precise ultrasmall Au(I)6 nanocluster where the six gold atoms are complexed by three sterically interlocking stabilizing ligands is reported, allowing a unique combination of efficient third harmonic generation (THG), intense photoluminescence quantum yield (35%), ultrafast quantum coherence, and electron accepting properties. The reaction of 6-(dibutylamino)-1,3,5-triazine-2,4-dithiol (TRZ) with HAuCl4 leads to complexation by thiolation. However, intriguingly, another reduction step is needed to form the centrosymmetric Au(I)6TRZ3 clusters with the multifunctional properties. Here, ascorbic acid is employed as a mild reducing agent, in contrast to the classic reducing agents, like NaBH4 and NaBH3CN, which often produce mixtures of clusters or gold nanoparticles. Such Au(I)6 nanocluster films produce very strong THG response, never observed for nanoclusters. The clusters also produce brilliant single and multiphoton luminescence with exceptional stability. Density functional theory calculations and femtosecond transient absorption studies suggest ultrafast ligand-to-metal charge transfer, quantum coherence with long decoherence time 200–300 fs, and fast propagation of excitation from the core to the surrounding solvent. Finally, novel electron-accepting ground state properties allow p-doping of 2D field-effect transistor devices. Summarizing, the potential of ultrasmall sterically interlocked Au(I) clusters, i.e., complexes allowed by the new sequential reduction protocol, towards multifunctional devices, fast photoswitches, and quantum colloidal devices is shown.
High-Throughput Tailoring of Nanocellulose Films : From Complex Bio-Based Materials to Defined Multifunctional Architectures
(2020-11-16) Khakalo, Alexey; Mäkelä, Tapio; Johansson, Leena Sisko; Orelma, Hannes; Tammelin, Tekla
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
This paper demonstrates a high-throughput approach to fabricate nanocellulose films with multifunctional performance using conventionally existing unit operations. The approach comprises cast-coating and direct interfacial atmospheric plasma-assisted gas-phase modification along with the microscale patterning technique (nanoimprint lithography, NIL), all applied in roll-to-roll mode, to introduce organic functionalities in conjunction with structural manipulation. Our strategy results in multifunctional cellulose nanofibrils (CNF) films in which the high optical transmittance (∼90%) is retained while the haze can be adjusted (2-35%). Concomitantly, the hydrophobic/hydrophilic balance can be tuned (50-21 mJ/m2 with the water contact angle ranging from ∼20 up to ∼120°), while intrinsic hygroscopicity of CNF films is not significantly compromised. Therefore, a challenge to produce multifunctional bio-based materials with properties defined by various high-performance applications conjoined to the lack of efficient processing strategies is elucidated. Overall, economically and ecologically viable strategy, which was realized by facile and upscalable unit operations using the R2R technology, is introduced to expand the properties' spaces and thus offer a vast variety of interesting applications for CNF films.
Hydrothermally induced changes in the properties of MFC and characterization of the low molar mass degradation products
(2019-11-01) Hiltunen, Salla; Koljonen, Krista; Niemelä, Klaus; Heiskanen, Isto; Johansson, Leena Sisko; Backfolk, Kaj
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
The aim of this study was to determine hydrothermally induced changes in the physico-chemical properties of a fine microfibrillated cellulose (MFC). The MFC was prepared from a monocomponent endoglucanase-treated never-dried birch kraft pulp which had been run several times through a microfluidizer in order to obtain a sample substantially free from fibers or fiber fragments. The fine MFC was subjected to hydrothermal treatment at 150∘C for 0.5, 2.5, 4.5, 8.5 and 20.5 h, after which the viscosity, water-retention capacity, surface charge, discoloration and formation of hydrolysis products were determined. The viscosity, surface charge and water-retention capacity of MFC decreased as a result of the treatment but in oscillatory measurements the storage and loss moduli increased. Hydrothermal treatment also caused discoloration of the sample which could not be fully washed away with water. Surface analysis with XPS revealed no significant changes in the surface structure of the dried MFC cakes but the filtrates after the hydrothermal treatment were complex mixtures of sugars, organic acids and furans. The main degradation products detected were xylose and xylobiose, but isomerization products of sugars (xylulose, fructose) were also found in the filtrates. In addition numerous organic acids, including formic, glycolic, lactic and xylonic acid, were identified in the filtrates, showing that both acid and alkaline catalyzed reactions occur due to dissociation of water into H + and OH -.
Mesoporous Carbon Microfibers for Electroactive Materials Derived from Lignocellulose Nanofibrils
(2020-06-15) Wang, Ling; Borghei, Maryam; Ishfaq, Amal; Lahtinen, Panu; Ago, Mariko; Papageorgiou, Anastassios C.; Lundahl, Meri J.; Johansson, Leena Sisko; Kallio, Tanja; Rojas, Orlando J.
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
The growing adoption of biobased materials for electronic, energy conversion, and storage devices has relied on high-grade or refined cellulosic compositions. Herein, lignocellulose nanofibrils (LCNF), obtained from simple mechanical fibrillation of wood, are proposed as a source of continuous carbon microfibers obtained by wet spinning followed by single-step carbonization at 900 °C. The high lignin content of LCNF (∼28% based on dry mass), similar to that of the original wood, allowed the synthesis of carbon microfibers with a high carbon yield (29%) and electrical conductivity (66 S cm-1). The incorporation of anionic cellulose nanofibrils (TOCNF) enhanced the spinnability and the porous morphology of the carbon microfibers, making them suitable platforms for electrochemical double layer capacitance (EDLC). The increased loading of LCNF in the spinning dope resulted in carbon microfibers of enhanced carbon yield and conductivity. Meanwhile, TOCNF influenced the pore evolution and specific surface area after carbonization, which significantly improved the electrochemical double layer capacitance. When the carbon microfibers were directly applied as fiber-shaped supercapacitors (25 F cm-3), they displayed a remarkably long-term electrochemical stability (>93% of the initial capacitance after 10 000 cycles). Solid-state symmetric fiber supercapacitors were assembled using a PVA/H2SO4 gel electrolyte and resulted in an energy and power density of 0.25 mW h cm-3 and 65.1 mW cm-3, respectively. Overall, the results indicate a green and facile route to convert wood into carbon microfibers suitable for integration in wearables and energy storage devices and for potential applications in the field of bioelectronics.
Morphology-Controlled Synthesis of Colloidal Polyphenol Particles from Aqueous Solutions of Tannic Acid
(2019-01-01) Kämäräinen, Tero; Ago, Mariko; Greca, Luiz G.; Tardy, Blaise L.; Müllner, Markus; Johansson, Leena Sisko; Rojas, Orlando J.
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
The properties and application of particulate systems can be tailored by gaining control on their morphology. Here, a facile method is described for the bottom-up synthesis of biobased colloidal particles with varied morphologies by simple aqueous oxidation of tannic acid used as a precursor in alkaline solutions. Initial tannic acid concentrations of 1-2 wt % produce the largest crystalline yields, while total precipitate yields (up to 64%) are achieved at 2 wt %. Structural and thermochemical evaluations are reported from measurements based on X-ray diffraction and thermogravimetry, as well as infrared, mass, nuclear magnetic resonance, and X-ray photoelectron spectroscopies. The analyses suggest a galloyl-rich composition of the particles with thermal stability up to 450-500 °C. We show that the selection of the base species and pH affords control of the particle morphologies that include rods, platelets, rhomboids, cuboids, and quasi-spherical shapes. The main cause-effect relations are elucidated from principal component analysis of process conditions and particle morphogenetic parameters, which are derived from their physical dimensions and yield. The results indicate an anticorrelation between base countercation ionic radius and particle volume, whereas base strength and initial solution pH correlate with the total precipitate yield and elongated morphologies, respectively.
Nitrogen plasma surface treatment for improving polar ink adhesion on micro/nanofibrillated cellulose films
(2019-04-15) Dimic-Misic, Katarina; Kostić, Mirjana; Obradović, Bratislav; Kramar, Ana; Jovanović, Stevan; Stepanenko, Dimitrije; Mitrović-Dankulov, Marija; Lazović, Saša; Johansson, Leena Sisko; Maloney, Thad; Gane, Patrick
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
We find that nitrogen plasma treatment of micro/nanofibrillated cellulose films increases wettability of the surface by both liquid polar water and nonpolar hexadecane. The increased wetting effect is more pronounced in the case of polar liquid, favouring the use of plasma treated micro/nanofibrillated cellulose films as substrates for a range of inkjet printing including organic-based polar-solvent inks. The films were formed from aqueous suspensions of progressively enzymatic pretreated wood-free cellulose fibres, resulting in increased removal of amorphous species producing novel nanocellulose surfaces displaying increasing crystallinity. The mechanical properties of each film are shown to be highly dependent on the enzymatic pretreatment time. The change in surface chemistry arising from exposure to nitrogen plasma is revealed using X-ray photoelectron spectroscopy. That both polar and dispersive surface energy components become increased, as measured by contact angle, is also linked to an increase in surface roughness. The change in surface free energy is exemplified to favour the trapping of photovoltaic inks.
Non-leaching, Highly Biocompatible Nanocellulose Surfaces That Efficiently Resist Fouling by Bacteria in an Artificial Dermis Model
(2020-07-20) Hassan, Ghada; Forsman, Nina; Wan, Xing; Keurulainen, Leena; Bimbo, Luis M.; Stehl, Susanne; Van Charante, Frits; Chrubasik, Michael; Prakash, Aruna S.; Johansson, Leena Sisko; Mullen, Declan C.; Johnston, Blair F.; Zimmermann, Ralf; Werner, Carsten; Yli-Kauhaluoma, Jari; Coenye, Tom; Saris, Per E.J.; Österberg, Monika; Moreira, Vânia M.
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Bacterial biofilm infections incur massive costs on healthcare systems worldwide. Particularly worrisome are the infections associated with pressure ulcers and prosthetic, plastic, and reconstructive surgeries, where staphylococci are the major biofilm-forming pathogens. Non-leaching antimicrobial surfaces offer great promise for the design of bioactive coatings to be used in medical devices. However, the vast majority are cationic, which brings about undesirable toxicity. To circumvent this issue, we have developed antimicrobial nanocellulose films by direct functionalization of the surface with dehydroabietic acid derivatives. Our conceptually unique design generates non-leaching anionic surfaces that reduce the number of viable staphylococci in suspension, including drug-resistant Staphylococcus aureus, by an impressive 4-5 log units, upon contact. Moreover, the films clearly prevent bacterial colonization of the surface in a model mimicking the physiological environment in chronic wounds. Their activity is not hampered by high protein content, and they nurture fibroblast growth at the surface without causing significant hemolysis. In this work, we have generated nanocellulose films with indisputable antimicrobial activity demonstrated using state-of-the-art models that best depict an "in vivo scenario". Our approach is to use fully renewable polymers and find suitable alternatives to silver and cationic antimicrobials.
Phosphorylated cellulose nanofibers exhibit exceptional capacity for uranium capture
(2020-12) Lehtonen, Janika; Hassinen, Jukka; Kumar, Avula Anil; Johansson, Leena Sisko; Mäenpää, Roni; Pahimanolis, Nikolaos; Pradeep, Thalappil; Ikkala, Olli; Rojas, Orlando J.
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
We investigate the adsorption of hexavalent uranium, U(VI), on phosphorylated cellulose nanofibers (PHO-CNF) and compare the results with those for native and TEMPO-oxidized nanocelluloses. Batch adsorption experiments in aqueous media show that PHO-CNF is highly efficient in removing U(VI) in the pH range between 3 and 6. Gelling of nanofiber hydrogels is observed at U(VI) concentration of 500 mg/L. Structural changes in the nanofiber network (scanning and transmission electron microscopies) and the surface chemical composition (X-ray photoelectron spectroscopy) gave insights on the mechanism of adsorption. The results from batch adsorption experiments are fitted to Langmuir, Freundlich, and Sips isotherm models, which indicate a maximum adsorption capacity of 1550 mg/g, the highest value reported so far for any bioadsorbent. Compared to other metals (Zn, Mn, and Cu) and typical ions present in natural aqueous matrices the phosphorylated nanofibers are shown to be remarkably selective to U(VI). The results suggest a solution for the capture of uranium, which is of interest given its health and toxic impacts when present in aqueous matrices.