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  • 1.
    Héraly, Frédéric
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Stimuli-Responsive Materials Derived from Cellulose Nanofibrils: Synthesis, characterization, and performance evaluation2024Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis presents a comprehensive study on stimuli-responsive materials derived from cellulose nanofibrils (CNFs), focusing on their synthesis, characterization, and performance evaluation in various applications. Renowned for their biodegradability, renewability, and robust mechanical properties, CNFs are explored in three primary contexts: moisture-responsive actuators, voltage-responsive actuators, and CO2-responsive sensors.

    The unique properties of CNFs, such as high tensile strength and surface area, are leveraged to achieve effective motion in response to moisture exposure. Specifically, CNFs are utilized to create bilayer, torsional, and tensile actuators. These actuators exhibit controllable and dynamic responses, making them suitable for applications in soft robotics and wearable technology.

    In the realm of voltage-responsive actuators, this study investigates the impact of various electrolytes and counteranions on positively charged CNFs. It uncovers the critical role of electrolyte choice, ion migration and the plasticization effect within the CNFs matrix, resulting in volumetric expansion, which is pivotal to the actuation mechanism. These insights pave the way for CNFs applications requiring precise control of motion and flexibility in shape, such as in soft robotics.

    The third area of application involves the development of a capacitive CO2 sensor using CNFs-based foams functionalized with primary amines to enhance CO2 capture through chemisorption. This functionalization turns the CNFs-based foam into an efficient dielectric layer (DE) for sensor applications. The addition of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) to the DE further expands the scope of sensor's capacitance change in response to CO2 exposure, underscoring its potential in environmental monitoring and CO2 detection.

    Overall, this thesis emphasizes the versatility and adaptability of CNFs as a sustainable biomaterial for developing stimuli-responsive devices. The insights gained from studying CNFs in these varied applications contribute significantly to materials science and open new avenues for research in sustainable, bio-based materials.

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  • 2.
    Fijoł, Natalia
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Wallenberg Wood Science Center (WWSC).
    3D printing of Green Water Purification Filters: Design towards Sustainable and Scalable Biocomposite Materials2023Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The globally escalating water pollution and water scarcity necessitates the development of efficient and sustainable water treatment technologies. This thesis investigates the feasibility of utilizing renewable and waste materials in the form of green composites for the fabrication of water purification filters via Fused Deposition Modelling (FDM).

    The first system studied within this thesis is based on the biobased thermoplastic polymer - polylactic acid (PLA), which serves as a composite matrix that is reinforced and functionalized with an array of green materials including fish-scale extracted hydroxyapatite (HAp), 2,2,6,6 – tetramethylpiperdine-1-oxyl (TEMPO) - oxidized cellulose nanofibers (TCNF), chitin nanofibers (ChNF), and bioinspired metal-organic framework – SU-101. All the developed PLA-based biocomposites exhibited great design flexibility and excellent printability, leading to the development of high surface-finish quality water purification filters of various geometries and porosity architectures. The developed filters successfully removed various contaminants from water. High capability for removal of metal ions from both, model solutions (reaching removal capacity towards Cu2+ ions of 208 mg/gNF and 234 mg/gNF for ChNF/PLA and TCNF/PLA filters, respectively, compared to only 4 mg/g for PLA filters), as well as from an actual mine effluent, reaching removal efficiency towards i.a. Mn2+ ions of over 50 % was demonstrated. Moreover, the developed TCNF/PLA and ChNF/PLA filters successfully removed microplastics from laundry effluent with over 70 % separation efficiency. The PLA-based biocomposite filters surface-functionalized with SU-101 were also suitable for the removal of cationic dye, methylene blue (MB), from water with removal efficiencies of over 40 %.

    The second composite system explored the possibility of using post-consumer polycotton textile waste as a functional entity for the polyethylene terephthalate glycol (PETG) matrix, for the fabrication of 3D printing filaments, which can be further processed into highly functional water purification filters by the FDM. The conducted TEMPO-mediated oxidation of the polycotton garments introduced negatively charged carboxylic groups onto the 3D printing filament’s surface and consequently, onto the 3D printed structures, yielding filters suitable for removal of cationic dyes, such as MB, from water.

    Apart from being evaluated for their ability to remove various contaminants from water, the filters have been subjected to a series of tests to assess the homogeneity of the filler dispersion in the polymer matrix as well as the filters’ permeability and mechanical stability. The high throughput character of the filters was demonstrated, as e.g., for the HAp/PLA filters the calculated flux reached 2x106 Lm-2h-1bar-1. The reinforcing impact of the nanospecies on the polymer matrix in the gradient porosity filters was investigated and so, it was shown that the addition of ChNF and TCNF fibers into PLA increases their Young’s modulus value from 550.7 ± 2.8 MPa, to 622.7 ± 1.6 MPa and 702.9 ± 5.4 MPa, respectively. Moreover, the lifespan of the filters was assessed by subjecting them to an accelerated ageing procedure in water, which have shown that the TCNF/PLA and ChNF/PLA filters could serve up to eight and five months, respectively, while maintaining their functionality and good mechanical performance. Furthermore, the study revealed that the filters are indeed biodegradable, as after prolonged exposure to water at elevated temperatures, they have fully disintegrated.

    Overall, the obtained results demonstrate the feasibility of combining renewable and recycled materials with 3D printing technology to create water purification filters suitable for the removal of a wide variety of contaminants from water.

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  • 3.
    Hadi, Seyed Ehsan
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Yeprem, H. Aygül
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Yıldız Technical University, Turkey.
    Åhl, Agnes
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Morsali, Mohammad
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Kapuscinski, Martin
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Kriechbaum, Konstantin
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Sipponen, Mika H.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Highly magnetic hybrid foams based on aligned tannic acid-coated iron oxide nanoparticles and TEMPO-oxidized cellulose nanofibers2023In: RSC Advances, E-ISSN 2046-2069, Vol. 13, no 20, p. 13919-13927Article in journal (Refereed)
    Abstract [en]

    Lightweight iron oxide nanoparticle (IONP)/TEMPO-oxidized cellulose nanofibril (TOCNF) hybrid foams with an anisotropic structure and a high IONP content were produced using magnetic field-enhanced unidirectional ice-templating. Coating the IONP with tannic acid (TA) improved the processability, the mechanical performance, and the thermal stability of the hybrid foams. Increasing the IONP content (and density) increased the Young's modulus and toughness probed in compression, and hybrid foams with the highest IONP content were relatively flexible and could recover 14% axial compression. Application of a magnetic field in the freezing direction resulted in the formation of IONP chains that decorated the foam walls and the foams displayed a higher magnetization saturation, remanence, and coercivity compared to the ice-templated hybrid foams. The hybrid foam with an IONP content of 87% displayed a saturation magnetization of 83.2 emu g−1, which is 95% of the value for bulk magnetite. Highly magnetic hybrid foams are of potential interest for environmental remediation, energy storage, and electromagnetic interference shielding.

  • 4.
    Di, Andi
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Schiele, Carina
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Hadi, Seyed Ehsan
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Thermally Insulating and Moisture-Resilient Foams Based on Upcycled Aramid Nanofibers and Nanocellulose2023In: Advanced Materials, ISSN 0935-9648, E-ISSN 1521-4095, Vol. 35, no 48, article id 2305195Article in journal (Refereed)
    Abstract [en]

    Low-density foams and aerogels based on upcycled and bio-based nanofibers and additives are promising alternatives to fossil-based thermal insulation materials. Super-insulating foams are prepared from upcycled acid-treated aramid nanofibers (upANFA) obtained from Kevlar yarn and tempo-oxidized cellulose nanofibers (CNF) from wood. The ice-templated hybrid upANFA/CNF-based foams with an upANFA content of up to 40 wt% display high thermal stability and a very low thermal conductivity of 18–23 mW m−1 K−1 perpendicular to the aligned nanofibrils over a wide relative humidity (RH) range of 20% to 80%. The thermal conductivity of the hybrid upANFA/CNF foams is found to decrease with increasing upANFA content (5–20 wt%). The super-insulating properties of the CNF-upANFA hybrid foams are related to the low density of the foams and the strong interfacial phonon scattering between the very thin and partially branched upANFA and CNF in the hybrid foam walls. Defibrillated nanofibers from textiles are not limited to Kevlar, and this study can hopefully inspire efforts to upcycle textile waste into high-performance products.

  • 5.
    Di, Andi
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Xu, Jipeng
    Zinn, Thomas
    Sztucki, Michael
    Deng, Wentao
    Ashok, Anumol
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Lian, Cheng
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Tunable Ordered Nanostructured Phases by Co-assembly of Amphiphilic Polyoxometalates and Pluronic Block Copolymers2023In: Nano Letters, ISSN 1530-6984, E-ISSN 1530-6992, Vol. 23, no 5, p. 1645-1651Article in journal (Refereed)
    Abstract [en]

    The assembly of polyoxometalate (POM) metal–oxygen clusters into ordered nanostructures is attracting a growing interest for catalytic and sensing applications. However, assembly of ordered nanostructured POMs from solution can be impaired by aggregation, and the structural diversity is poorly understood. Here, we present a time-resolved small-angle X-ray scattering (SAXS) study of the co-assembly in aqueous solutions of amphiphilic organo-functionalized Wells-Dawson-type POMs with a Pluronic block copolymer over a wide concentration range in levitating droplets. SAXS analysis revealed the formation and subsequent transformation with increasing concentration of large vesicles, a lamellar phase, a mixture of two cubic phases that evolved into one dominating cubic phase, and eventually a hexagonal phase formed at concentrations above 110 mM. The structural versatility of co-assembled amphiphilic POMs and Pluronic block copolymers was supported by dissipative particle dynamics simulations and cryo-TEM. 

  • 6.
    Church, Tamara L.
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Kriechbaum, Konstantin
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Schiele, Carina
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Apostolopoulou-Kalkavoura, Varvara
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Hadi, Seyed Ehsan
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    A Stiff, Tough, and Thermally Insulating Air- and Ice-Templated Plant-Based Foam2022In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 23, no 6, p. 2595-2602Article in journal (Refereed)
    Abstract [en]

    By forming and directionally freezing an aqueous foam containing cellulose nanofibrils, methylcellulose, and tannic acid, we produced a stiff and tough anisotropic solid foam with low radial thermal conductivity. Along the ice-templating direction, the foam was as stiff as nanocellulose–clay composites, despite being primarily methylcellulose by mass. The foam was also stiff perpendicular to the direction of ice growth, while maintaining λr < 25 mW m–1 K–1 for a relative humidity (RH) up to 65% and <30 mW m–1 K–1 at 80% RH. This work introduces the tandem use of two practical techniques, foam formation and directional freezing, to generate a low-density anisotropic material, and this strategy could be applied to other aqueous systems where foam formation is possible. 

  • 7.
    Sultan, Sahar
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Nanocellulose based 3D printed hydrogel scaffolds for cartilage and bone regeneration: Tuning of composition, pore structure and functions2022Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Biobased-materials with customized scaffolds have played a prominent role in the success of tissue engineering (TE). Cellulose nanomaterials (CNM) isolated from the abundant biopolymer, cellulose, is explored in this thesis for TE engineering due to its versatile properties such as biocompatibility, high specific strength, surface functionality and water retention capacity. Hydrogel formation capability of CNM at low concentrations (1–2 wt%) and shear thinning behavior has facilitated its use in 3-dimensional (3D) printing as a fabrication technique for 2-dimensional (2D) and 3D scaffolds. This technique offers 3D scaffolds with tailored, controlled and complex geometries having precise micro and macro scaled structures. The current work focuses on CNM-based 3D printed hydrogel scaffolds with tuned composition and pore structure for cartilage and bone regeneration. Design of CNM hydrogel formulations with suitable rheological properties, hydrogel inks capable of ex-situ crosslinking, print resolution during printing due to swelling and mechanical and dimensional stability of the printed scaffolds in moist environment are key challenges that were addressed.

    Inspired by the hierarchical and gradient nature of natural tissues 3D printed hydrogel scaffolds with gradient pore structure and composition are reported for the first time with focus on cellulose nanocrystals (CNC) and TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl radical)-oxidized cellulose nanofibers (TOCNF) based hydrogel ink printing for advanced and functional scaffolds.

    CNC-based hydrogel ink was used to 3D print uniform and gradient porous cubic scaffolds for cartilage regeneration. This work highlighted the importance of nozzle movement to obtain high resolution scaffolds with higher z-axis. The anisotropic rigid CNC aligned themselves along the printing direction due to the shear induced orientation that was quantified between 61–76%. To obtain adequate mechanical properties (0.20–0.45 MPa) suitable for cartilage regeneration, the hydrogel ink solid content was increased almost two-fold (5.4 wt% to 9.9 wt%) while exhibiting and mimicking the viscoelasticity of natural cartilage tissues. To improve the bioactivity of the CNC-based 3D printed scaffolds, a surface treatment through dopamine coating was performed. This coating enhanced the hydrophilicity and capability of 3D printed scaffolds to bind bioactive molecules such as fibroblast growth factor (FGF-18) for soft TE scaffolds.

    Surface functionality of TOCNF was utilized to fabricate functional hybrid scaffolds (CelloZIF-8) through one-pot in- situ synthesis of Metal-Organic frameworks (MOFs) with varied ZIF-8 loadings (30.8–70.7%). The inherent porosity of the ZIF-8 was used for loading and stimuli-responsive (pH-dependent) releasing of drug molecule such as curcumin. The developed CelloMOF system was extended to other MOFs (MIL-100) and drugs (methylene blue). The shear thinning property of TOCNF was reserved after MOFs hybridization and was used to 3D print porous scaffolds with excellent shape fidelity. In Cello-Apatite, TOCNF was also used as template for in-situ synthesis of hydroxyapatite (HAP) where the HAP loading was 67 wt% to mimic the bone composition. In an attempt to address both cartilage and bone regeneration, a biphasic osteochondral 3D printed hydrogel scaffold has been introduced with tuned composition, pore structure and mechanical properties.

    The work presents a sustainable, cost effective and scalable approach for TE using biobased and toxic free water-based formulations using low temperature processes that are extendable to other biomaterials as well as to other applications, such as water treatment.

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  • 8.
    Héraly, Frédéric
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Zhang, Miao
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Åhl, Agnes
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Cao, Wei
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Yuan, Jiayin
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Nanodancing with Moisture: Humidity-Sensitive Bilayer Actuator Derived from Cellulose Nanofibrils and Reduced Graphene Oxide2022In: Advanced Intelligent Systems, E-ISSN 2640-4567, Vol. 4, no 1, article id 2100084Article in journal (Refereed)
    Abstract [en]

    Bilayer actuators, traditionally consisting of two laminated materials, are the most common types of soft or hybrid actuators. Herein, a nanomaterial-based organic–inorganic humidity-sensitive bilayer actuator composed of TEMPO-oxidized cellulose nanofibrils (TCNF-Na+) and reduced graphene oxide (rGO) sheets is presented. The hybrid actuator displays a large humidity-driven locomotion with an atypical fast unbending. Cationic exchange of the anionically charged TCNF-Na+ and control of the layer thickness is used to tune and dictate the locomotion and actuator's response to humidity variations. Assembly of a self-oscillating electrical circuit, that includes a conductive rGO layer, displays autonomous on-and-off lighting in response to actuation-driven alternating electrical heating.

  • 9.
    Ménard, Delphine
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. Umeå University, Sweden.
    Blaschek, Leonard
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Kriechbaum, Konstantin
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Lee, Cheng Choo
    Serk, Henrik
    Zhu, Chuantao
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Lyubartsev, Alexander
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Nuoendagula,
    Bacsik, Zoltán
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Mathew, Aji
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Kajita, Shinya
    Pesquet, Edouard
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. Stockholm University, Faculty of Science, The Bolin Centre for Climate Research (together with KTH & SMHI). Umeå University, Sweden.
    Plant biomechanics and resilience to environmental changes are controlled by specific lignin chemistries in each vascular cell type and morphotype2022In: The Plant Cell, ISSN 1040-4651, E-ISSN 1532-298X, Vol. 34, no 12, p. 4877-4896Article in journal (Refereed)
    Abstract [en]

    The biopolymer lignin is deposited in the cell walls of vascular cells and is essential for long-distance water conduction and structural support in plants. Different vascular cell types contain distinct and conserved lignin chemistries, each with specific aromatic and aliphatic substitutions. Yet, the biological role of this conserved and specific lignin chemistry in each cell type remains unclear. Here, we investigated the roles of this lignin biochemical specificity for cellular functions by producing single cell analyses for three cell morphotypes of tracheary elements, which all allow sap conduction but differ in their morphology. We determined that specific lignin chemistries accumulate in each cell type. Moreover, lignin accumulated dynamically, increasing in quantity and changing in composition, to alter the cell wall biomechanics during cell maturation. For similar aromatic substitutions, residues with alcohol aliphatic functions increased stiffness whereas aldehydes increased flexibility of the cell wall. Modifying this lignin biochemical specificity and the sequence of its formation impaired the cell wall biomechanics of each morphotype and consequently hindered sap conduction and drought recovery. Together, our results demonstrate that each sap-conducting vascular cell type distinctly controls their lignin biochemistry to adjust their biomechanics and hydraulic properties to face developmental and environmental constraints. 

  • 10.
    Munier, Pierre
    et al.
    Department of Materials and Environmental Chemistry, Stockholm University, Stockholm, 10691, Sweden.
    Hadi, Seyed Ehsan
    Department of Materials and Environmental Chemistry, Stockholm University, Stockholm, 10691, Sweden;Wallenberg Wood Science Center, Department of Materials and Environmental Chemistry, Stockholm University, Stockholm, 10691, Sweden.
    Segad, Mo
    Department of Materials and Environmental Chemistry, Stockholm University, Stockholm, 10691, Sweden.
    Bergström, Lennart
    Department of Materials and Environmental Chemistry, Stockholm University, Stockholm, 10691, Sweden.
    Rheo-SAXS study of shear-induced orientation and relaxation of cellulose nanocrystal and montmorillonite nanoplatelet dispersions2022In: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 18, no 2, p. 390-396Article in journal (Refereed)
  • 11.
    Munier, Pierre
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Hadi, Seyed Ehsan
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Wallenberg Wood Science Center, Sweden.
    Segad, Mo
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Rheo-SAXS study of shear-induced orientation and relaxation of cellulose nanocrystal and montmorillonite nanoplatelet dispersions2022In: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 18, no 2, p. 390-396Article in journal (Refereed)
    Abstract [en]

    The development of robust production processes is essential for the introduction of advanced materials based on renewable and Earth-abundant resources. Cellulose nanomaterials have been combined with other highly available nanoparticles, in particular clays, to generate multifunctional films and foams. Here, the structure of dispersions of rod-like cellulose nanocrystals (CNC) and montmorillonite nanoplatelets (MNT) was probed using small-angle X-ray scattering within a rheological cell (Rheo-SAXS). Shear induced a high degree of particle orientation in both the CNC-only and CNC:MNT composite dispersions. Relaxation of the shear-induced orientation in the CNC-only dispersion decayed exponentially and reached a steady-state within 20 seconds, while the relaxation of the CNC:MNT composite dispersion was found to be strongly retarded and partially inhibited. Viscoelastic measurements and Guinier analysis of dispersions at the shear rate of 0.1 s(-1) showed that the addition of MNT promotes gel formation of the CNC:MNT composite dispersions. A better understanding of shear-dependent assembly and orientation of multi-component nanoparticle dispersions can be used to process materials with improved mechanical and functional properties.

  • 12. Björkander, Sophia
    et al.
    Du, Likun
    Zuo, Fanglei
    Ekström, Sandra
    Wang, Yating
    Wan, Hui
    Sherina, Natalia
    Schoutens, Lisanne
    Andréll, Juni
    Stockholm University, Science for Life Laboratory (SciLifeLab). Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Andersson, Niklas
    Georgelis, Antonios
    Bergström, Anna
    Marcotte, Harold
    Kull, Inger
    Hammarström, Lennart
    Melén, Erik
    Pan-Hammarström, Qiang
    SARS-CoV-2-specific B- and T-cell immunity in a population-based study of young Swedish adults2022In: Journal of Allergy and Clinical Immunology, ISSN 0091-6749, E-ISSN 1097-6825, Vol. 149, no 1, p. 65-75Article in journal (Refereed)
    Abstract [en]

    Background: Young adults are now considered major spreaders of coronavirus disease 2019 (COVID-19) disease. Although most young individuals experience mild to moderate disease, there are concerns of long-term adverse health effects. The impact of COVID-19 disease and to which extent population-level immunity against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) exists in young adults remain unclear.

    Objective: We conducted a population-based study on humoral and cellular immunity to SARS-CoV-2 and explored COVID-19 disease characteristics in young adults.

    Methods: We invited participants from the Swedish BAMSE (Barn [Children], Allergy Milieu, Stockholm, Epidemiology) birth cohort (age 24-27 years) to take part in a COVID-19 followup. From 980 participants (October 2020 to June 2021), we here present data on SARS-CoV-2 receptor-binding domain-specific IgM, IgA, and IgG titers measured by ELISA and on symptoms and epidemiologic factors associated with seropositivity. Further, SARS-CoV-2-specific memory B-and T-cell responses were detected for a subpopulation (n 5 108) by ELISpot and FluoroSpot.

    Results: A total of 28.4% of subjects were seropositive, of whom 18.4% were IgM single positive. One in 7 seropositive subjects was asymptomatic. Seropositivity was associated with use of public transport, but not with sex, asthma, rhinitis, IgE sensitization, smoking, or body mass index. In a subset of representative samples, 20.7% and 35.0% had detectable SARSCoV-2 specific B-and T-cell responses, respectively. B-and T-cell memory responses were clearly associated with seropositivity, but T-cell responses were also detected in 17.2% of seronegative subjects.

    Conclusions: Assessment of IgM and T-cell responses may improve population-based estimations of SARS-CoV-2 infection. The pronounced surge of both symptomatic and asymptomatic infections among young adults indicates that the large-scale vaccination campaign should be continued. (J Allergy Clin Immunol 2022;149:65-75.)

  • 13. Bender, Philipp
    et al.
    Wetterskog, Erik
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Salazar-Alvarez, German
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Uppsala University, Sweden.
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Hermann, Raphael P.
    Brückel, Thomas
    Wiedenmann, Albrecht
    Disch, Sabrina
    Shape-induced superstructure formation in concentrated ferrofluids under applied magnetic fields2022In: Journal of applied crystallography, ISSN 0021-8898, E-ISSN 1600-5767, Vol. 55, no 6, p. 1613-1621Article in journal (Refereed)
    Abstract [en]

    The field-induced ordering of concentrated ferrofluids based on spherical and cuboidal maghemite nanoparticles is studied using small-angle neutron scattering, revealing a qualitative effect of the faceted shape on the interparticle interactions as shown in the structure factor and correlation lengths. Whereas a spatially disordered hard-sphere interaction potential with a short correlation length is found for ∼9 nm spherical nanoparticles, nanocubes of a comparable particle size exhibit a more pronounced interparticle interaction and the formation of linear arrangements. Analysis of the anisotropic two-dimensional pair distance correlation function gives insight into the real-space arrangement of the nanoparticles. On the basis of the short interparticle distances found here, oriented attachment, i.e. a face-to-face arrangement of the nanocubes, is likely. The unusual field dependence of the interparticle correlations suggests a field-induced structural rearrangement.

  • 14.
    Lv, Zhong-Peng
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Aalto University, Finland.
    Kapuscinski, Martin
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Uppsala University, Sweden.
    Járvás, Gábor
    Yu, Shun
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Time-Resolved SAXS Study of Polarity- and Surfactant-Controlled Superlattice Transformations of Oleate-Capped Nanocubes During Solvent Removal2022In: Small, ISSN 1613-6810, E-ISSN 1613-6829, Vol. 18, no 22, article id 2106768Article in journal (Refereed)
    Abstract [en]

    Structural transformations and lattice expansion of oleate-capped iron oxide nanocube superlattices are studied by time-resolved small-angle X-ray scattering (SAXS) during solvent removal. The combination of conductor-like screening model for real solvents (COSMO-RS) theory with computational fluid dynamics (CFD) modeling provides information on the solvent composition and polarity during droplet evaporation. Evaporation-driven poor-solvent enrichment in the presence of free oleic acid results in the formation of superlattices with a tilted face-centered cubic (fcc) structure when the polarity reaches its maximum. The tilted fcc lattice expands subsequently during the removal of the poor solvent and eventually transforms to a regular simple cubic (sc) lattice during the final evaporation stage when only free oleic acid remains. Comparative studies show that both the increase in polarity as the poor solvent is enriched and the presence of a sufficient amount of added oleic acid is required to promote the formation of structurally diverse superlattices with large domain sizes. 

  • 15.
    Munier, Pierre
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Assembly and alignment in cellulose nanomaterial-based composite dispersions and thermally insulating foams2021Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Research on nanoparticles extracted from renewable and highly available sources is motivated by both the development of functional nanomaterials and the drive to replace widely used materials based on fossil resources. In particular, cellulose, in the form of cellulose nanomaterials (CNM), has attracted increased attention for the development of sustainable and high performance products, thanks to properties that include high specific mechanical strength, chemical versatility and anisotropic thermal conductivity. Ice-templated CNM foams display super-insulating properties across the direction of the aligned particles (radially) and could potentially compete with fossil-based insulation materials. This thesis investigates the alignment and co-assembly of widely available inorganic nanomaterials with CNM in aqueous dispersions, and the relative importance of phonon scattering in anisotropic thermally insulating composite foams.

    Time resolved small-angle X-ray scattering (SAXS) experiments have been conducted to study assembly and alignment in composite aqueous dispersions containing cellulose nanocrystals (CNC) and montmorillonite (MNT) clay nanoplatelets. The co-assembly of CNC and MNT in slowly evaporating levitating droplets was dominated by the interactions between the dispersed CNC particles but MNT promoted gelation and assembly at lower total volume fractions than in CNC-only droplets. Combining SAXS with rotational rheology showed that shear induced a high degree of orientation of CNC in both the CNC-only and mixed CNC:MNT dispersions. The shear-induced CNC orientation relaxed quickly in the CNC-only dispersion but relaxation was strongly retarded and partially inhibited in the mixed CNC:MNT dispersions.

    Analysis of previous works suggests that anisotropic and multiscale CNM-based foams with a high number of interfaces can favour heat dissipation by phonon scattering within the foam walls. Measurements and theoretical estimates of the thermal conductivities of CNC-only ice-templated foams over a wide range of densities confirmed the importance of phonon scattering to achieve super-insulating radial thermal conductivity values. 

    Ice-templated CNC:MNT composite foams displayed a lower radial thermal conductivity compared to CNC-only foams, which suggests that the introduction of heterogeneous interfaces between the biopolymer and the clay enhanced the dissipation of heat through phonon scattering. Composite ice-templated foams of colloidal silica and TEMPO-oxidised cellulose nanofibrils (TCNF) were significantly stronger under mechanical compression and less sensitive to moisture uptake than TCNF-only foams, and maintained radial thermal conductivities that are comparable with widely used thermally insulating materials. These examples could pave the way towards the development of super-insulating, strong and moisture-resilient CNM-based composite foams.

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  • 16.
    Munier, Pierre
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Di, Andi
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Hadi, Seyed Ehsan
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Kapuscinski, Martin
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Segad, Mo
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Assembly of cellulose nanocrystals and clay nanoplatelets studied by time-resolved X-ray scattering2021In: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 17, no 23, p. 5747-5755Article in journal (Refereed)
    Abstract [en]

    Time-resolved small-angle X-ray scattering (SAXS) was used to probe the assembly of cellulose nanocrystals (CNC) and montmorillonite (MNT) over a wide concentration range in aqueous levitating droplets. Analysis of the SAXS curves of the one-component and mixed dispersions shows that co-assembly of rod-like CNC and MNT nanoplatelets is dominated by the interactions between the dispersed CNC particles and that MNT promotes gelation and assembly of CNC, which occurred at lower total volume fractions in the CNC:MNT than in the CNC-only dispersions. The CNC dispersions displayed a d proportional to phi(-1/2) scaling and a low-q power-law exponent of 2.0-2.2 for volume fractions up to 35%, which indicates that liquid crystal assembly co-exists and competes with gelation.

  • 17.
    Apostolopoulou Kalkavoura, Varvara
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Munier, Pierre
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Dlugozima, Lukasz
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Heuthe, Veit-Lorenz
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Effect of density, phonon scattering and nanoporosity on the thermal conductivity of anisotropic cellulose nanocrystal foams2021In: Scientific Reports, E-ISSN 2045-2322, Vol. 11, no 1, article id 18685Article in journal (Refereed)
    Abstract [en]

    Anisotropic cellulose nanocrystal (CNC) foams with densities between 25 and 130 kg m−3 (CNC25 –CNC130) were prepared by directional ice-templating of aqueous dispersions. Estimates of the solid and gas conduction contributions to the thermal conductivity of the foams using a parallel resistor model showed that the relatively small increase of the radial thermal conductivity with increasing foam density can be attributed to interfacial phonon scattering. The foam wall nanoporosity and, to a lesser extent, the orientation of the CNC particles and alignment of the columnar macropores, also influence the insulation performance of the foams. The insight on the importance of phonon scattering for the thermal insulation properties of nanocellulose foams provides useful guidelines for tailoring nanofibrillar foams for super-insulating applications.

  • 18.
    Church, Tamara L.
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Kriechbaum, Konstantin
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Emami, S. Noushin
    Stockholm University, Faculty of Science, Department of Molecular Biosciences, The Wenner-Gren Institute. University of Greenwich, U.K..
    Mozuraitis, Raimondas
    Stockholm University, Faculty of Science, Department of Zoology.
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Functional Wood-Foam Composites for Controlled Uptake and Release2021In: ACS Sustainable Chemistry and Engineering, E-ISSN 2168-0485, Vol. 9, no 46, p. 15571-15581Article in journal (Refereed)
    Abstract [en]

    Wood-foam hierarchical composites were produced via the shear-forced infiltration of shear-thinning nanocellulose-based foams or gels into the tracheids of Picea abies. Shear processing viscoelastic and shear-thinning aqueous foams composed of cellulose nanocrystals, methylcellulose, and tannic acid (total solids content: 2 wt %) resulted in foam-filled wood composites containing 15-20 wt % foam, with open foam structures and compression strengths similar to those of unmodified P. abies. An amino-functionalized nanocellulose-containing foam confined in wood reversibly adsorbed CO2, retaining 15% of its theoretical uptake capacity over 50 cycles in the thermogravimetric analyzer, and a citronellol-loaded foam released this mosquito-repellent compound over four days, as evaluated using solid-phase microextraction. Shear-forced infiltration of functional foams into wood is an operationally simple route to hierarchically porous composites based on renewable materials.

  • 19.
    Apostolopoulou-Kalkavoura, Varvara
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Hu, Shiqian
    Lavoine, Nathalie
    Garg, Mohit
    Linares, Mathieu
    Munier, Pierre
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Zozoulenko, Igor
    Shiomi, Junichiro
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Humidity-Dependent Thermal Boundary Conductance Controls Heat Transport of Super-Insulating Nanofibrillar Foams2021In: Matter, ISSN 2590-2393, E-ISSN 2590-2385, Vol. 4, no 1, p. 276-289Article in journal (Refereed)
    Abstract [en]

    Cellulose nanomaterial (CNM)-based foams and aerogels with thermal conductivities substantially below the value for air attract significant interest as super-insulating materials in energy-efficient green buildings. However, the moisture dependence of the thermal conductivity of hygroscopic CNM-based materials is poorly understood, and the importance of phonon scattering in nanofibrillar foams remains unexplored. Here, we show that the thermal conductivity perpendicular to the aligned nanofibrils in super-insulating ice-templated nanocellulose foams is lower for thinner fibrils and depends strongly on relative humidity (RH), with the lowest thermal conductivity (14 mW m−1 K−1) attained at 35% RH. Molecular simulations show that the thermal boundary conductance is reduced by the moisture-uptake-controlled increase of the fibril-fibril separation distance and increased by the replacement of air with water in the foam walls. Controlling the heat transport of hygroscopic super-insulating nanofibrillar foams by moisture uptake and release is of potential interest in packaging and building applications.

  • 20.
    Willhammar, Tom
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Daicho, Kazuho
    Johnstone, Duncan N.
    Kobayashi, Kayoko
    Liu, Yingxin
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Midgley, Paul A.
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Saito, Tsuguyuki
    Local Crystallinity in Twisted Cellulose Nanofibers2021In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 15, no 2, p. 2730-2737Article in journal (Refereed)
    Abstract [en]

    Cellulose is crystallized by plants and other organisms into fibrous nanocrystals. The mechanical properties of these nanofibers and the formation of helical superstructures with energy dissipating and adaptive optical properties depend on the ordering of polysaccharide chains within these nanocrystals, which is typically measured in bulk average. Direct measurement of the local polysaccharide chain arrangement has been elusive. In this study, we use the emerging technique of scanning electron diffraction to probe the packing of polysaccharide chains across cellulose nanofibers and to reveal local ordering of the chains in twisting sections of the nanofibers. We then use atomic force microscopy to shed light on the size dependence of the inherent driving force for cellulose nanofiber twisting. The direct measurement of crystalline twisted regions in cellulose nanofibers has important implications for understanding single-cellulose-fibril properties that influence the interactions between cellulose nanocrystals in dense assemblies. This understanding may enable cellulose extraction and separation processes to be tailored and optimized.

  • 21. Gross, B.
    et al.
    Philipp, S.
    Josten, E.
    Leliaert, J.
    Wetterskog, E.
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Poggio, M.
    Magnetic anisotropy of individual maghemite mesocrystals2021In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 103, no 1, article id 014402Article in journal (Refereed)
    Abstract [en]

    Interest in creating magnetic metamaterials has led to methods for growing superstructures of magnetic nanoparticles. Mesoscopic crystals of maghemite (gamma-Fe2O3) nanoparticles can be arranged into highly ordered body-centered tetragonal lattices of up to a few micrometers. Although measurements on disordered ensembles have been carried out, determining the magnetic properties of individual mesoscopic crystals is challenging due to their small total magnetic moment. Here, we overcome these challenges by utilizing sensitive dynamic cantilever magnetometry to study individual micrometer-sized gamma-Fe2O3 mesocrystals. These measurements reveal an unambiguous cubic anisotropy, resulting from the crystalline anisotropy of the constituent maghemite nanoparticles and their alignment within the mesoscopic lattice. The signatures of anisotropy and its origins come to light because we combine the self-assembly of highly ordered mesocrystals with the ability to resolve their individual magnetism. This combination is promising for future studies of the magnetic anisotropy of other nanoparticles, which are too small to investigate individually.

  • 22. Garg, Mohit
    et al.
    Apostolopoulou-Kalkavoura, Varvara
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Linares, Mathieu
    Kaldéus, Tahani
    Malmström, Eva
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). KTH Royal Institute of Technology, Sweden.
    Zozoulenko, Igor
    Moisture uptake in nanocellulose: the effects of relative humidity, temperature and degree of crystallinity2021In: Cellulose, ISSN 0969-0239, E-ISSN 1572-882X, Vol. 28, no 14, p. 9007-9021Article in journal (Refereed)
    Abstract [en]

    Foams made from cellulose nanomaterials are highly porous and possess excellent mechanical and thermal insulation properties. However, the moisture uptake and hygroscopic properties of these materials need to be better understood for their use in biomedical and bioelectronics applications, in humidity sensing and thermal insulation. In this work, we present a combination of hybrid Grand Canonical Monte Carlo and Molecular Dynamics simulations and experimental measurements to investigate the moisture uptake within nanocellulose foams. To explore the effect of surface modification on moisture uptake we used two types of celluloses, namely TEMPO-oxidized cellulose nanofibrils and carboxymethylated cellulose nanofibrils. We find that the moisture uptake in both the cellulose nanomaterials increases with increasing relative humidity (RH) and decreases with increasing temperature, which is explained using the basic thermodynamic principles. The measured and calculated moisture uptake in amorphous cellulose (for a given RH or temperature) is higher as compared to crystalline cellulose with TEMPO- and CM-modified surfaces. The high water uptake of amorphous cellulose films is related to the formation of water-filled pores with increasing RH. The microscopic insight of water uptake in nanocellulose provided in this study can assist the design and fabrication of high-performance cellulose materials with improved properties for thermal insulation in humid climates or packaging of water sensitive goods.

  • 23.
    Apostolopoulou-Kalkavoura, Varvara
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Thermal Conductivity of Hygroscopic Foams Based on Cellulose Nanomaterials2021Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Biobased super-insulating materials could mitigate climate change by minimizing the use of petroleum-based materials, creating artificial carbon sinks and minimizing the energy needed to maintain pleasant interior conditions. Cellulose nanomaterials (CNM) produced from abundantly available cellulose sources constitute versatile, highly anisotropic raw materials with tunable surface chemistry and high strength. This thesis includes the evaluation of the thermal conductivity of isotropic and anisotropic CNM-based foams and aerogels and analysis of the dominant heat transfer mechanisms. 

    We have developed a customized measurement cell for hygroscopic materials in which the humidity and temperature are carefully controlled while the thermal conductivity is measured. Anisotropic cellulose nanofibrils (CNF) foams with varying diameters showed a super-insulating behavior perpendicular (radial) to the nanofibril direction, that depended non-linearly on the relative humidity (RH) and foam density. Molecular simulations revealed that the very low thermal conductivity is related to phonon scattering due to the increase of the inter-fibrillar gap with increasing RH that resulted in a 6-fold decrease of the thermal boundary conductance. The moisture-induced swelling exceeds the thermal conductivity increase due to water uptake at low and intermediate RH and resulted in a minimum thermal conductivity of 14 mW m-1 K-1 at 35% RH and 295 K for the foams based on the thinnest CNF.

    The density-dependency of the thermal conductivity of cellulose nanocrystal (CNC) foams with densities of 25 to 129 kg m-3 was investigated and a volume-weighted modelling of the solid and gas thermal conductivity contributions suggested that phonon scattering was essential to explain the low radial thermal conductivity, whereas the replacement of air with water and the Knudsen effect related to the nanoporosity in the foam walls had a small effect. Intermediate-density CNC foams (34 kg m-3) exhibited a radial thermal conductivity of 24 mW m-1 K-1 at 295 K and 20% RH, which is below the value for air.

    The moisture uptake of foams based on CNMs with different degree of crystallinity and surface modifications decreased significantly with increasing crystallinity and temperature. Molecular simulations showed that the narrow pore size distribution of the amorphous cellulose film, and the relatively low water adsorption in the hydration cell around the oxygen of the carboxyl group play an important role for the moisture uptake of amorphous and crystalline CNM-based materials.

    Isotropic CNF- and polyoxamer based foams as well as CNF-AL-MIL-53 (an aluminum‑based metal-organic framework) foams were both moderately insulating (>40 mW m-1 K-1) and comparable with commercial expanded polystyrene. The thermal conductivity of CNF and polyoxamer foams displayed a very strong RH dependency that was modelled with a modified Künzel’s model. The presence of hydrophobic AL-MIL-53 decreased the moisture uptake of CNF-AL-MIL-53 aerogels by 42% compared to CNF-polyoxamer foams.

    Solid and gas conduction are the main heat transfer mechanisms in hygroscopic nanofibrillar foams and aerogels that depend on the interfacial phonon scattering, Knudsen effect and water uptake. It is essential that the thermal conductivity measurements of hygroscopic CNM-based foams and aerogels are determined at controlled RH and that parameters such as the temperature, density, nanoporosity, fibril dimensions and alignment are characterized and controlled for systematic development and upscaling of biobased foams for applications in building insulation and packaging.

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  • 24.
    Apostolopoulou-Kalkavoura, Varvara
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Munier, Pierre
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Thermally Insulating Nanocellulose-Based Materials2021In: Advanced Materials, ISSN 0935-9648, E-ISSN 1521-4095, Vol. 33, no 28, article id 2001839Article, review/survey (Refereed)
    Abstract [en]

    Thermally insulating materials based on renewable nanomaterials such as nanocellulose could reduce the energy consumption and the environmental impact of the building sector. Recent reports of superinsulating cellulose nanomaterial (CNM)-based aerogels and foams with significantly better heat transport properties than the commercially dominating materials, such as expanded polystyrene, polyurethane foams, and glass wool, have resulted in a rapidly increasing research activity. Herein, the fundamental basis of thermal conductivity of porous materials is described, and the anisotropic heat transfer properties of CNMs and films with aligned CNMs and the processing and structure of novel CNM-based aerogels and foams with low thermal conductivities are presented and discussed. The extraordinarily low thermal conductivity of anisotropic porous architectures and multicomponent approaches are highlighted and related to the contributions of the Knudsen effect and phonon scattering.

  • 25.
    Moreno, Adrian
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Liu, Jinrong
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Gueret, Robin
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Hadi, Seyed Ehsan
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Slabon, Adam
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Sipponen, Mika H.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Unravelling the Hydration Barrier of Lignin Oleate Nanoparticles for Acid- and Base-Catalyzed Functionalization in Dispersion State2021In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 60, no 38, p. 20897-20905Article in journal (Refereed)
    Abstract [en]

    Lignin nanoparticles (LNPs) are promising renewable nanomaterials with applications ranging from biomedicine to water purification. However, the instability of LNPs under acidic and basic conditions severely limits their functionalization for improved performance. Here, we show that controlling the degree of esterification can significantly improve the stability of lignin oleate nanoparticles (OLNPs) in acidic and basic aqueous dispersions. The high stability of OLNPs is attributed to the alkyl chains accumulated in the shell of the particle, which delays protonation/deprotonation of carboxylic acid and phenolic hydroxyl groups. Owing to the enhanced stability, acid- and base-catalyzed functionalization of OLNPs at pH 2.0 and pH 12.0 via oxirane ring-opening reactions were successfully performed. We also demonstrated these new functionalized particles as efficient pH-switchable dye adsorbents and anticorrosive particulate coatings.

  • 26.
    Kriechbaum, Konstantin
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Antioxidant and UV-Blocking Leather-Inspired Nanocellulose-Based Films with High Wet Strength2020In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 21, no 5, p. 1720-1728Article in journal (Refereed)
    Abstract [en]

    The mechanical performance in the wet state needs to be significantly improved and the intrinsic functionalities should be fully utilized to promote the replacement of fossil-based plastics with renewable biobased materials. We demonstrate a leather-inspired approach to produce multifunctional materials with a high wet strength that is based on tannin-induced precipitation of gelatin grafted onto surface-modified cellulose nanofibrils (CNF). The leather-inspired CNF-based films had a wet tensile strength of 33 MPa, a Young's modulus of 310 MPa, and a strain at failure of 22%, making the wet materials stronger than, for example, dry conventional low-density polyethylene and more ductile than paper-based food packaging materials. The tannin-containing films displayed excellent antioxidant and UV-blocking properties, rapidly scavenging more than 90% of added free radicals and absorbing 100% of light in the UV-B/UV-C range. This work illustrates the prospect of combining renewable materials in a leather-inspired approach to form wet strong and multifunctional films with potential application in food packaging.

  • 27. Walther, Andreas
    et al.
    Lossada, Francisco
    Benselfelt, Tobias
    Kriechbaum, Konstantin
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Berglund, Lars
    Ikkala, Olli
    Saito, Tsuguyuki
    Wagberg, Lars
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Best Practice for Reporting Wet Mechanical Properties of Nanocellulose-Based Materials2020In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 21, no 6, p. 2536-2540Article in journal (Refereed)
    Abstract [en]

    Nanocellulose-based materials and nanocomposites show extraordinary mechanical properties with high stiffness, strength, and toughness. Although the last decade has witnessed great progress in understanding the mechanical properties of these materials, a crucial challenge is to identify pathways to introduce high wet strength, which is a critical parameter for commercial applications. Because of the waterborne fabrication methods, nanocellulose-based materials are prone to swelling by both adsorption of moist air or liquid water. Unfortunately, there is currently no best practice on how to take the swelling into account when reporting mechanical properties at different relative humidity or when measuring the mechanical properties of fully hydrated materials. This limits and in parts fully prevents comparisons between different studies. We review current approaches and propose a best practice for measuring and reporting mechanical properties of wet nanocellulose-based materials, highlighting the importance of swelling and the correlation between mechanical properties and volume expansion.

  • 28. Zhou, Shengyang
    et al.
    Apostolopoulou-Kalkavoura, Varvara
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    da Costa, Marcus Vinicius Tavares
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Stromme, Maria
    Xu, Chao
    Elastic Aerogels of Cellulose Nanofibers@Metal-Organic Frameworks for Thermal Insulation and Fire Retardancy2020In: Nano-Micro Letters, ISSN 2150-5551, Vol. 12, no 1, article id 9Article in journal (Refereed)
    Abstract [en]

    Metal-organic frameworks (MOFs) with high microporosity and relatively high thermal stability are potential thermal insulation and flame-retardant materials. However, the difficulties in processing and shaping MOFs have largely hampered their applications in these areas. This study outlines the fabrication of hybrid CNF@MOF aerogels by a stepwise assembly approach involving the coating and cross-linking of cellulose nanofibers (CNFs) with continuous nanolayers of MOFs. The cross-linking gives the aerogels high mechanical strength but superelasticity (80% maximum recoverable strain, high specific compression modulus of similar to 200 MPa cm(3) g(-1), and specific stress of similar to 100 MPa cm(3) g(-1)). The resultant lightweight aerogels have a cellular network structure and hierarchical porosity, which render the aerogels with relatively low thermal conductivity of similar to 40 mW m(-1) K-1. The hydrophobic, thermally stable MOF nanolayers wrapped around the CNFs result in good moisture resistance and fire retardancy. This study demonstrates that MOFs can be used as efficient thermal insulation and flame-retardant materials. It presents a pathway for the design of thermally insulating, superelastic fire-retardant nanocomposites based on MOFs and nanocellulose.

  • 29.
    Kapuscinski, Martin
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Following nanoparticle self-assembly in real-time: Small-angle X-ray scattering and quartz crystal microbalance study of self-assembling iron oxide nanocubes2020Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Self-assembly of nanoparticles is a widely used technique to produce nanostructured materials with crystallographic coherence on the atomic scale, i.e. mesocrystals, which can display useful collective properties. This thesis focusses on the underlying mechanism and dynamics of mesocrystal formation by using real-time techniques. Quartz-crystal microbalance with dissipation monitoring (QCM-D) as well as small-angle X-ray scattering (SAXS) in combination with optical microscopy were used to probe the temporal evolution of growing mesocrystals to elucidate the growth mechanism.

    Time-resolved small-angle X-ray scattering was used to probe the formation and how the structure and defects of the growing mesocrystals in levitating droplets evolve with time. Probing self-assembly of oleate-capped iron oxide nanocubes during evaporation-driven poor-solvent enrichment (EDPSE) showed that a low particle concentration in combination with a short nucleation period can generate large and well-ordered mesocrystals. Information on the formation and transformation of defects in mesocrystals were obtained by analysis of the temporal evolution of crystal strain. A transition from a rapidly increasing isotropic strain to a decreasing anisotropic strain towards the end of the growth stage was observed. The occurrence of anisotropic strain was assigned to the formation of stress-relieving dislocations in the crystal, which were induced by large internal stresses caused by superlattice contraction.

    Directed assembly of superparamagnetic iron oxide nanocubes, subjected to a weak magnetic field, produced one-dimensional mesocrystal fibers. Real-time SAXS as well as optical microscopy revealed a two-stage growth mechanism. The primary stage involved the growth of cuboidal mesocrystals by nanocube self-assembly. In a secondary stage, the cuboidal mesocrystals were assembled and aligned into fibers by the magnetic field. Evaluation of the magnetic dipole-dipole and van der Waals interactions showed that the dipolar forces arising between two nanocubes in a weak magnetic field are negligible compared to the van der Waals forces, but become the dominant force for larger mesocrystals, which drives the formation of fibers.

    QCM-D combined with optical microscopy provided simultaneously information on the rheological properties as well as on the mass of an adsorbed self-assembled layer of iron oxide nanocubes. We show that the iron oxide nanocubes rapidly assembled into an array with primarily viscous characteristics. This fluid-like behaviour can be assigned to a layer of solvent surrounding the nanocubes inside the assembly. Expulsion of the thin solvent layer from the assembled array is responsible for the increase in rigidity observed shortly after the beginning of self-assembly.

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  • 30.
    Kriechbaum, Konstantin
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Functional Nanocellulose–Tannin Materials Inspired by Nature and Traditional Processes2020Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Renewable and biodegradable alternatives to fossil-based materials are essential as concerns over depleting finite resources and the pollution of our ecosystems are growing. Abundant, highly anisotropic, and mechanically strong cellulose nanofibrils (CNF) are attractive building blocks for the fabrication of high-performance biobased materials that can compete with their conventional fossil-based counterparts. This thesis presents potential solutions to key challenges in the production and properties of CNF and CNF-based materials, such as low moisture resistance and energy-intense processing, by using the physicochemical properties of tannins. The benchmarking of CNF to improve energy-efficient production was investigated and the ability of plant-derived tannins to precipitate proteins, react with nucleophiles when oxidized, and coordinate to metal ions was exploited to produce multifunctional films and foams that were inspired by Nature or traditional processes.

    Wet strong, antioxidant, and UV-blocking CNF-based films were produced by mimicking the traditional process of leather tanning. Oxidized CNF were grafted with gelatin that was precipitated with a water-soluble tannin. The polyphenolic tannin provided the films with good radical scavenging properties and efficient blocking of light in the UV-B/UV-C range. The insoluble gelatin–tannin complexes conferred upon the material wet mechanical properties that were comparable to the dry mechanical performance of fossil-based packaging films. So far, there is no universally accepted approach to account for how the swelling of a hygroscopic CNF-based film influences its mechanical properties in humid or wet conditions. Here, a best practice for determining and reporting wet strength is suggested.

    Inspired by the sclerotization of insect cuticle, a scalable route towards moisture-resilient, strong, and thermally insulating CNF-based foams was developed. The CNF were modified with a polyamine, ice-templated, treated with an oxidized tannin, solvent-exchanged to ethanol, and evaporatively dried. The cross-linked structure had a high compressive modulus and a thermal conductivity close to that of air, even at high relative humidities.

    A method to produce micron-sized patterns on CNF films based on the traditional Bògòlanfini dyeing technique is presented. The films were pre-impregnated with a tannin and patterned using microcontact printing with a metal-salt-soaked stamp. The line and dot patterns were analyzed and their colors were tuned by changing the metal ion in the printing ink or the pH.

    The final part of the thesis describes a novel approach to assess the degree of CNF fibrillation during energy-efficient grinding by analyzing the structure and properties of anisotropic foams. The optimal energy input during fiber disintegration that produced CNF foams with the best mechanical and thermal insulation properties, as well as the highest CNF and foam cell wall orientation, was identified.

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  • 31.
    Kriechbaum, Konstantin
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Apostolopoulou-Kalkavoura, Varvara
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Munier, Pierre
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Sclerotization-inspired aminoquinone cross-linking of thermally insulating and moisture-resilient biobased foams2020In: ACS Sustainable Chemistry and Engineering, E-ISSN 2168-0485, Vol. 8, no 47, p. 17408-17416Article in journal (Refereed)
    Abstract [en]

    Thermally insulating foams and aerogels based on cellulose nanofibrils (CNFs) are promising alternatives to fossil-based thermal insulation materials. We demonstrate a scalable route for moisture-resilient lightweight foams that relies on sclerotization-inspired Michael-type cross-linking of amine-modified CNFs by oxidized tannic acid. The solvent-exchanged, ice-templated, and quinone-tanned cross-linked anisotropic structures were mechanically stable and could withstand evaporative drying with minimal structural change. The low-density (7.7 kg m–3) cross-linked anisotropic foams were moisture-resilient and displayed a compressive modulus of 90 kPa at 98% relative humidity (RH) and thermal conductivity values close to that of air between 20 and 80% RH at room temperature. Sclerotization-inspired cross-linking of biobased foams offers an energy-efficient and scalable route to produce sustainable and moisture-resilient lightweight materials.

  • 32.
    Munier, Pierre
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Apostolopoulou-Kalkavoura, Varvara
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Persson, Michael
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Strong silica-nanocellulose anisotropic composite foams combine low thermal conductivity and low moisture uptake2020In: Cellulose, ISSN 0969-0239, E-ISSN 1572-882X, Vol. 27, no 18, p. 10825-10836Article in journal (Refereed)
    Abstract [en]

    We report the fabrication of anisotropic lightweight composite foams based on commercial colloidal silica particles and TEMPO-oxidized cellulose nanofibrils (TOCNF). The unidirectional ice-templating of silica-TOCNF dispersions resulted in anisotropic foams with columnar porous structures in which the inorganic and organic components were homogeneously distributed. The facile addition of silica particles yielded a significant enhancement in mechanical strength, compared to TOCNF-only foams, and a 3.5-fold increase in toughness at a density of 20 kg m−3. The shape of the silica particles had a large effect on the mechanical properties; anisotropic silica particles were found to strengthen the foams more efficiently than spherical particles. The water uptake of the foams and the axial thermal conductivity in humid air were reduced by the addition of silica. The composite foams were super-insulating at dry conditions at room temperature, with a radial thermal conductivity value as low as 24 mW m−1 K−1, and remained lower than 35 mW m−1 K−1 up to 80% relative humidity. The combination of high strength, low thermal conductivity and manageable moisture sensitivity suggests that silica-TOCNF composite foams could be an attractive alternative to the oil-based thermal insulating materials.

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  • 33. Josten, Elisabeth
    et al.
    Angst, Manuel
    Glavic, Artur
    Zakalek, Paul
    Rücker, Ulrich
    Seeck, Oliver H.
    Kovács, András
    Wetterskog, Erik
    Kentzinger, Emmanuel
    Dunin-Borkowski, Rafal E.
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Brückel, Thomas
    Strong size selectivity in the self-assembly of rounded nanocubes into 3D mesocrystals2020In: Nanoscale Horizons, ISSN 2055-6764, E-ISSN 2055-6756, Vol. 5, no 7, p. 1065-1072Article in journal (Refereed)
    Abstract [en]

    The self-assembly of nanoparticles into highly ordered crystals is largely influenced by variations in the size and shape of the constituent particles, with crystallization generally not observed if their polydispersity is too large. Here, we report on size selectivity in the self-assembly of rounded cubic maghemite nanoparticles into three-dimensional mesocrystals. Different X-ray scattering techniques are used to study and compare a nanoparticle dispersion that is used later for self-assembly, an ensemble of mesocrystals grown on a substrate, as well as an individual mesocrystal. The individual lm-sized mesocrystal is isolated using a focused-ion-beam-based technique and investigated by the diffraction of a micro-focused X-ray beam. Structural analysis reveals that individual mesocrystals have a drastically smaller size dispersity of nanoparticles than that in the initial dispersion, implying very strong size selectivity during self-assembly. The small size dispersity of the nanoparticles within individual mesocrystals is accompanied by a very narrow lattice parameter distribution. In contrast, the lattice parameter distribution within all mesocrystals of an ensemble is about four times wider than that of individual mesocrystals, indicating significant size fractionalization between mesocrystals during self-assembly. The small size dispersity within each mesocrystal has important implications for their physical properties.

  • 34.
    Kapuscinski, Martin
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Agthe, Michael
    Lv, Zhong-Peng
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Liu, Yingxin
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Segad, Mo
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Temporal Evolution of Superlattice Contraction and Defect-Induced Strain Anisotropy in Mesocrystals during Nanocube Self-Assembly2020In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 14, no 5, p. 5337-5347Article in journal (Refereed)
    Abstract [en]

    Understanding and controlling defect formation during the assembly of nanoparticles is crucial for fabrication of self-assembled nanostructured materials with predictable properties. Here, time-resolved small-angle X-ray scattering was used to probe the temporal evolution of strain and lattice contraction during evaporation-induced self-assembly of oleate-capped iron oxide nanocubes in a levitating drop. We show that the evolution of the strain and structure of the growing mesocrystals is related to the formation of defects as the solvent evaporated and the assembly process progressed. Superlattice contraction during the mesocrystal growth stage is responsible for the rapidly increasing isotropic strain and the introduction of point defects. The crystal strain, quantified by the Williamson-Hall analysis, became more anisotropic due to the formation of stress-relieving dislocations as the mesocrystal growth was approaching completion. Understanding the formation of the transformation of defects in mesocrystals and superlattices could assist in the development of optimized assembly processes of nanoparticles with multifunctional properties.

  • 35.
    Kapuscinski, Martin
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Munier, Pierre
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Segad, Mo
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Two-Stage Assembly of Mesocrystal Fibers with Tunable Diameters in Weak Magnetic Fields2020In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 20, no 10, p. 7359-7366Article in journal (Refereed)
    Abstract [en]

    Controlling the morphology and crystallographic coherence of assemblies of magnetic nanoparticles is a promising route to functional materials. Time-resolved small-angle X-ray scattering (SAXS) was combined with microscopy and scaling analysis to probe and analyze evaporation-induced assembly in levitating drops and thin films of superparamagnetic iron oxide nanocubes in weak magnetic fields. We show that assembly of micrometer-sized mesocrystals with a cubic shape preceded the formation of fibers with a high degree of crystallographic coherence and tunable diameters. The second-stage assembly of aligned cuboidal mesocrystals into fibers was driven by the magnetic field, but the first-stage assembly of the oleate-capped nanocubes was unaffected by weak magnetic fields. The transition from 3D growth of the primary mesocrystals to the second stage 1D assembly of the elongated fibers was related to the size and field dependence of isotropic van der Waals and directional dipolar interactions between the interacting mesocrystals.

  • 36.
    Liu, Yingxin
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Wallenberg Wood Science Center, KTH, Sweden.
    Schütz, Christina
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Wallenberg Wood Science Center, KTH, Sweden.
    Salazar-Alvarez, German
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Wallenberg Wood Science Center, KTH, Sweden.
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Assembly, Gelation, and Helicoidal Consolidation of Nanocellulose Dispersions2019In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 35, no 10, p. 3600-3606Article in journal (Refereed)
    Abstract [en]

    The ability to probe the assembly, gelation, and helicoidal consolidation of cellulose nanocrystal (CNC) dispersions at high concentrations can provide unique insight into the assembly and can assist optimized manufacturing of CNC-based photonic and structural materials. In this Feature Article, we review and discuss the concentration dependence of the structural features, characterized by the particle separation distance and the helical pitch, at CNC concentrations (c) that range from the isotropic state, over the biphasic range, to the fully liquid crystalline state. The structure evolution of CNC dispersions probed by time resolved small-angle X-ray scattering during evaporation-induced assembly highlighted the importance of gelation and consolidation at high concentrations. We briefly discuss how the homogeneity of helicoidal nanostructures in dry CNC films can be improved and present an outlook for future work.

  • 37. Adolphsen, Jens Q.
    et al.
    Gil, Vanesa
    Sudireddy, Bhaskar R.
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Characterisation and processing of aqueous LaNi0.6Fe0.4O3 Suspensions into Porous Electrode Layers for Alkaline Water Electrolysis2019In: Journal of the European Ceramic Society, ISSN 0955-2219, E-ISSN 1873-619X, Vol. 39, no 4, p. 1271-1278Article in journal (Refereed)
    Abstract [en]

    The colloidal properties and processing of aqueous LaNi0.6.Fe0.4O3 suspensions into electrode layers with hierarchical pore sizes has been investigated by light scattering, electron microscopy and rheology. We found that the colloidal stability of the oxide particles and the resulting microstructure of the electrode layers were similar when dispersing the particles at their intrinsic pH, or when adding polyvinylpyrrolidone. The addition of the ammonium salt of poly(methaacrylic acid) resulted in a poor colloidal stability and the concentrated suspensions became viscoelastic during processing. Addition of rice starch resulted in an increase of the porosity but the cast electrode layers cracked and delaminated.

  • 38.
    Bergström, Malin
    et al.
    Stockholm University, Faculty of Social Sciences, Department of Public Health Sciences, Centre for Health Equity Studies (CHESS). Karolinska Institutet, Sweden.
    Fransson, Emma
    Stockholm University, Faculty of Social Sciences, Department of Public Health Sciences, Centre for Health Equity Studies (CHESS).
    Wells, Michael B.
    Köhler, Lennart
    Hjern, Anders
    Stockholm University, Faculty of Social Sciences, Department of Public Health Sciences, Centre for Health Equity Studies (CHESS). Karolinska Institutet, Sweden.
    Children with two homes: Psychological problems in relation to living arrangements in Nordic 2- to 9-year-olds2019In: Scandinavian Journal of Public Health, ISSN 1403-4948, E-ISSN 1651-1905, Vol. 47, no 2, p. 137-145Article in journal (Refereed)
    Abstract [en]

    Aim: Joint physical custody, children spending equal time in each parents’ respective home after a parental divorce, is particularly common in Nordic compared with other Western countries. Older children have been shown to fare well in this practice but for young children there are few existing studies. The aim of this paper is to study psychological problems in 2- to 9-year-old Nordic children in different family forms. Methods: Total symptom score according to the Strengths and Difficulties Questionnaire as well as scores showing externalizing problems were compared among 152 children in joint physical custody, 303 in single care and 3207 in nuclear families through multiple linear regression analyses. Results: Children in single care had more psychological symptoms than those in joint physical custody (B = 1.08; 95% CI 0.48 to 1.67) and those in nuclear families had the least reported symptoms (B = −0.53; 95% CI −0.89 to −0.17). Externalizing problems were also lower in nuclear families (B = −0.28, 95% CI −0.52 to −0.04) compared with joint physical custody after adjusting for covariates. Conclusions: Young children with non-cohabiting parents suffered from more psychological problems than those in intact families. Children in joint physical custody had a lower total problem score than those in single care after adjusting for covariates. Longitudinal studies with information on family factors before the separation are needed to inform policy of young children’s post-separation living arrangements.

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  • 39.
    Limaye, Mukta
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Royal Institute of Technology, Sweden; Indian Institute of Science Education & Research, India.
    Schütz, Christina
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Royal Institute of Technology, Sweden.
    Kriechbaum, Konstantin
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Wohlert, Jakob
    Bacsik, Zoltán
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Wohlert, Malin
    Xia, Wei
    Pléa, Mama
    Dembele, Cheick
    Salazar-Alvarez, German
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Royal Institute of Technology, Sweden.
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Functionalization and patterning of nanocellulose films by surface-bound nanoparticles of hydrolyzable tannins and multivalent metal ions2019In: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 11, no 41, p. 19278-19284Article in journal (Refereed)
    Abstract [en]

    Inspired by the Bogolanfini dyeing technique, we report how flexible nanofibrillated cellulose (CNF) films can be functionalized and patterned by surface-bound nanoparticles of hydrolyzable tannins and multivalent metal ions with tunable colors. Molecular dynamics simulations show that gallic acid (GA) and ellagic acid (EA) rapidly adsorb and assemble on the CNF surface, and atomic force microscopy confirms that nanosized GA assemblies cover the surface of the CNF. CNF films were patterned with tannin-metal ion nanoparticles by an in-fibre reaction between the pre-impregnated tannin and the metal ions in the printing ink. Spectroscopic studies show that the Fe-III/II ions interact with GA and form surface-bound, stable GA-Fe-III/II nanoparticles. The functionalization and patterning of CNF films with metal ion-hydrolyzable tannin nanoparticles is a versatile route to functionalize films based on renewable materials and of interest for biomedical and environmental applications.

  • 40.
    Lyu, Zhong-Peng
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Kapuscinski, Martin
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Tunable assembly of truncated nanocubes by evaporation-driven poor-solvent enrichment2019In: Nature Communications, E-ISSN 2041-1723, Vol. 10, article id 4228Article in journal (Refereed)
    Abstract [en]

    Self-assembly of nanocrystals is extensively used to generate superlattices with long-range translational order and atomic crystallographic orientation, i.e. mesocrystals, with emergent mesoscale properties, but the predictability and tunability of the assembly methods are poorly understood. Here, we report how mesocrystals produced by poor-solvent enrichment can be tuned by solvent composition, initial nanocrystal concentration, poor-solvent enrichment rate, and excess surfactant. The crystallographic coherence and mesoscopic order within the mesocrystal were characterized using techniques in real and reciprocal spaces, and superlattice growth was followed in real time by small-angle X-ray scattering. We show that formation of highly ordered superlattices is dominated by the evaporation-driven increase of the solvent polarity and particle concentration, and facilitated by excess surfactant. Poor-solvent enrichment is a versatile nanoparticle assembly method that offers a promising production route with high predictability to modulate and maximize the size and morphology of nanocrystal metamaterials.

  • 41.
    Voisin, Hugo P.
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Gordeyeva, Korneliya
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Siqueira, Gilberto
    Hausmann, Michael K.
    Studart, Andre R.
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    3D Printing of Strong Lightweight Cellular Structures Using Polysaccharide-Based Composite Foams2018In: ACS Sustainable Chemistry and Engineering, E-ISSN 2168-0485, Vol. 6, no 12, p. 17160-17167Article in journal (Refereed)
    Abstract [en]

    Polysaccharides are attractive sustainable resources for the fabrication of advanced materials, but the assembly of these building blocks into complex-shaped structures combining the high strength and low weight required in many applications remains challenging. We have investigated and optimized the rheological and mechanical properties of polysaccharide-based composite foams based on mixtures of methylcellulose (MC), cellulose nanofibrils (CNF), montmorillonite (MMT), and glyoxal and tannic acid. Such foams were found to be stabilized by the coadsorption of MC, CNF, and MMT at the air-water interface, while the complexation of the polysaccharides with tannic acid improved the foam stability. Tannic acid could also be used to tune and optimize the microstructure and the viscoelastic properties of the wet foam for direct ink writing of robust cellular architectures. Glyoxal had no noticeable effect on the properties of the wet foams but significantly enhanced the water resilience and stiffness of the lightweight material obtained after drying at ambient pressure and elevated temperatures with minimum shrinkage. The foams possessed a high porosity and displayed a specific Youngs modulus and yield strength that outperformed other biobased foams and commercially available expanded polystyrene. The strong and water-resilient 3D printed foams can be surface modified using, for example, aminosilanes, which opens up applications for air purification and thermal insulation.

  • 42. Zhou, Yaxin
    et al.
    Saito, Tsuguyuki
    Bergstrom, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). The University of Tokyo, Japan.
    Isogai, Akira
    Acid-Free Preparation of Cellulose Nanocrystals by TEMPO Oxidation and Subsequent Cavitation2018In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 19, no 2, p. 633-639Article in journal (Refereed)
    Abstract [en]

    Softwood bleached kraft pulp (SBKP) and microcrystalline cellulose (MCC) were oxidized using a 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-mediated system. The TEMPO-oxidized SBKP prepared with 10 mmol/g NaClO (SBKP-10) had a higher mass recovery ratio and higher carboxylate content than the other prepared celluloses including the TEMPO-oxidized MCCs. The SBKP-10 was then exposed to cavitation-induced forces through sonication in water for 10-120 min to prepare aqueous dispersions of needle-like TEMPO-oxidized cellulose nanocrystals (TEMPO-CNCs) with homogeneous width of 3.5 to 3.6 nm and average lengths of similar to 200 nm. The average chain lengths of the cellulose molecules that make up the TEMPO-CNCs were less than half the average lengths of the TEMPO-CNCs. Compared with conventional CNCs prepared by acid hydrolysis, the TEMPO-CNCs prepared by the acid-free and dialysis-free process exhibited higher mass recovery ratios, significantly higher amounts of surface anionic groups, and smaller and more homogeneous widths.

  • 43.
    Liu, Yingxin
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). KTH, Sweden.
    Agthe, Michael
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Salajková, Michaela
    Gordeyeva, Korneliya
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Guccini, Valentina
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). KTH, Sweden.
    Fall, Andreas
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Salazar-Alvarez, Germán
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). KTH, Sweden.
    Schütz, Christina
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). KTH, Sweden.
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Assembly of cellulose nanocrystals in a levitating drop probed by time-resolved small angle X-ray scattering2018In: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 10, no 38, p. 18113-18118Article in journal (Refereed)
    Abstract [en]

    Assembly of bio-based nano-sized particles into complex architectures and morphologies is an area of fundamental interest and technical importance. We have investigated the assembly of sulfonated cellulose nanocrystals (CNC) dispersed in a shrinking levitating aqueous drop using time-resolved small angle X-ray scattering (SAXS). Analysis of the scaling of the particle separation distance (d) with particle concentration (c) was used to follow the transition of CNC dispersions from an isotropic state at 1-2 vol% to a compressed nematic state at particle concentrations above 30 vol%. Comparison with SAXS measurements on CNC dispersions at near equilibrium conditions shows that evaporation-induced assembly of CNC in large levitating drops is comparable to bulk systems. Colloidal states with d vs. c scalings intermediate between isotropic dispersions and unidirectional compression of the nematic structure could be related to the biphasic region and gelation of CNC. Nanoscale structural information of CNC assembly up to very high particle concentrations can help to fabricate nanocellulose-based materials by evaporative methods.

  • 44.
    Gordeyeva, Korneliya
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Design, processing and properties of lightweight foams from cellulose nanofibers2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Foams are applied in many areas including thermal insulation of buildings, flotation devices, packaging, filters for water purification, CO2 sorbents and for biomedical devices. Today, the market is dominated by foams produced from synthetic, non-renewable polymers, which raises serious concerns for the sustainable and ecological development of our society. This thesis will demonstrate how lightweight foams based on nanocellulose can be processed and how the properties in both the wet and dry state can be optimized.

    Lightweight and highly porous foams were successfully prepared using a commercially available surface-active polyoxamer, Pluronic P123TM, cellulose nanofibers (CNFs), and soluble CaCO3 nanoparticles. The stability of wet and dry composite foams was significantly improved by delayed aggregation of the CNF matrix by gluconic acid-triggered dissolution of the CaCO3 nanoparticles, which generated a strong and dense CNF network in the foam walls. Drying the Ca2+-reinforced foam at 60 °C resulted in moderate shrinkage but the overall microstructure and pore/foam bubble size distribution were preserved after drying. The elastic modulus of Ca2+-reinforced composite foams with a density of 9 – 15 kg/m3 was significantly higher than fossil-based polyurethane foams.

    Lightweight hybrid foams have been prepared from aqueous dispersions of a surface-active aminosilane (AS) and CNF for a pH range of 10.4 – 10.8. Evaporative drying at a mild temperature (60 °C) resulted in dry foams with low densities (25 – 50 kg/m3) and high porosities (96 – 99%). The evaporation of water catalyzed the condensation of the AS to form low-molecular linear polymers, which contributed to the increase in the stiffness and strength of the CNF-containing foam lamella.

    Strong wet foams suitable for 3D printing were produced using methylcellulose (MC), CNFs and montmorillonite clay (MMT) as a filler and tannic acid and glyoxal as cross-linkers. The air-water interface of the foams was stabilized by the co-adsorption of MC, CNF and MMT. Complexation of the polysaccharides with tannic acid improved the foam stability and the viscoelastic properties of the wet foam for direct ink writing of robust cellular architectures. Glyoxal improved the water resistance and stiffened the lightweight material that had been dried at ambient pressure and elevated temperatures with minimum shrinkage. The highly porous foams displayed a specific Young’s modulus and yield strength that outperformed other bio-based foams and commercially available expanded polystyrene.

    Unidirectional freezing, freeze-casting, of nanocellulose dispersions produced cellular foams with high alignment of the rod-like nanoparticles in the freezing direction. Quantification of the alignment with X-ray diffraction showed high orientation of CNF and short and stiff cellulose nanocrystals (CNC).

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  • 45. Wicklein, Bernd
    et al.
    Diem, Achim M.
    Knöller, Andrea
    Cavalcante, Manoella S.
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Bill, Joachim
    Burghard, Zaklina
    Dual-Fiber Approach toward Flexible Multifunctional Hybrid Materials2018In: Advanced Functional Materials, ISSN 1616-301X, E-ISSN 1616-3028, Vol. 28, no 27, article id 1704274Article in journal (Refereed)
    Abstract [en]

    Multifunctional paper-like materials containing metal oxide nanofibers are important for flexible electronics and other redox-based applications, but are often prone to mechanical failure. This work presents the coassembly of V2O5 nanofibers (VNFs) in a dual-fiber approach together with cellulose nanofibers to produce tough (0.26 MJ m(-3)), but strong (250 MPa) flexible hybrid materials. Indeed, nanotensile tests reveal a significant increase in toughness (200%) and strength (85%) of the hybrid films as compared to pristine VNF films. The microstructure of the films shows a transition from an anisotropic texture for the single-component films to an isotropic, entangled network in case of the hybrid films, which facilitates effective fracture resistance mechanisms. The flexible hybrid films display high electrical conductivity (0.2 S cm(-1)) and elastic properties originating from V2O5 nanofibers with excellent toughness and transparency endowed by the cellulose nanofibers. The self-supported hybrid films show reversible electrochromic behavior without the need for common substrates such as conducting indium tin oxide glass. It is conceivable that these self-supported films can be exploited in the future in smart, flexible optoelectronic devices.

  • 46. Yu, Zhi-Long
    et al.
    Yang, Ning
    Apostolopoulou-Kalkavoura, Varvara
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Qin, Bing
    Ma, Zhi-Yuan
    Xing, Wei-Yi
    Qiao, Chan
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Antonietti, Markus
    Yu, Shu-Hong
    Fire-Retardant and Thermally Insulating Phenolic-Silica Aerogels2018In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 57, no 17, p. 4538-4542Article in journal (Refereed)
    Abstract [en]

    Energy efficient buildings require materials with a low thermal conductivity and a high fire resistance. Traditional organic insulation materials are limited by their poor fire resistance and inorganic insulation materials are either brittle or display a high thermal conductivity. Herein we report a mechanically resilient organic/inorganic composite aerogel with a thermal conductivity significantly lower than expanded polystyrene and excellent fire resistance. Co-polymerization and nanoscale phase separation of the phenol-formaldehyde-resin (PFR) and silica generate a binary network with domain sizes below 20 nm. The PFR/SiO2 aerogel can resist a high-temperature flame without disintegration and prevents the temperature on the non-exposed side from increasing above the temperature critical for the collapse of reinforced concrete structures.

  • 47.
    Gordeyeva, Korneliya
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Voisin, Hugo
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Hedin, Niklas
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Lavoine, Nathalie
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Lightweight foams of amine-rich organosilica and cellulose nanofibrils by foaming and controlled condensation of aminosilane2018In: Materials Chemistry Frontiers, E-ISSN 2052-1537, Vol. 2, no 12, p. 2220-2229Article in journal (Refereed)
    Abstract [en]

    Organosilica foams are commonly formed by a multistep process involving hydrolysis and condensationof organosilanes followed by solvent exchange and e.g. supercritical CO2 drying. Here, we propose astraightforward route to synthesize lightweight hybrid foams from aqueous dispersions of a surfaceactiveaminosilane (AS) and TEMPO-oxidized cellulose nanofibrils (TCNFs). Air bubbles were introducedin the TCNF/AS dispersion by mechanical blending, and the foam was solidified by oven-drying.Evaporative drying at mild temperature (60 1C) resulted in dry foams with low densities (25–50 kg m3),high porosities (96–99%) and macropores of 150–300 mm in diameter. The foaming and foam stabilizationwere successful for a pH range of 10.4–10.8 for foams containing 55–65 wt% of organosilica inthe dry state. The protonation of AS increased the ionic strength of the dispersion and enhanced theinterparticle interactions with TCNFs and, in turn, the foam viscosity and foam stability upon drying. Theevaporation of water catalyzed the condensation of the AS to form low-molecular linear polymers,which resulted in an increased stiffness and strength of the foam lamella. The crosslinking of the ASpolymeric network with the TCNF matrix allowed lightweight and homogeneous macroporous foams tobe obtained with controlled densities and high amine content (amine content 44.5 mmol g1) using anenvironmentally friendly technique.

  • 48.
    Liu, Yingxin
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Wallenberg Wood Science Center, Sweden.
    Nanocellulose-based materials: from colloidal assembly to functional films2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The assembly of nature-based nanomaterials into complex architectures is both a design principle of biological composites, e.g., wood and nacre with outstanding properties and a promising route for developing functional macroscopic materials. This thesis aims to investigate and understand the colloidal and self-assembly behaviour of nanocellulose in aqueous dispersions. Moreover, composite films of nanocellulose and nanoclay/lignin with diverse functionalities, e.g., mechanical and optical properties, are fabricated by tailoring the electrostatic interactions of these building blocks.

    The evaporation induced assembly of sulfonated cellulose nanocrystal (CNC) has been followed in either an aqueous droplet on substrates or a levitated droplet by real-time small angle X-ray scattering. The evolution of structural features, e.g., an isotropic phase, biphasic phase, fully liquid crystalline and contracted helical structures of drying CNC dispersions were related to the power-law scaling of the particle separation distance (d) with concentrations (c, from 1 vol% to 38 vol%). Below 2 vol%, CNC dispersions consolidated isotropically with a scaling of d c-1/3, while the fully cholesteric liquid crystalline phase showed a unidimensional contraction of the nematic structure (d c-1) with increasing concentrations. Competition between gelation and the ordered assembly of CNC was quantitatively evaluated in nanoscale for the first time, which was reflected by a scaling of d c-2/3.

    The rheology of composite dispersions of carboxylated cellulose nanofibril (CNF) and nanoclay was investigated, which was influenced by the surface charge of CNF, the morphology of nanoclays and interactions between CNF and clay particles. Optically transparent films of synthetic aminoclay (50 wt%) and CNF were fabricated, of which tensile strength and strain to failure (205 MPa and 7.5%) were significantly higher than those of nacre and other nacre-mimicking nanocellulose-based materials, e.g., montmorillonite-CNF films, due to the formation of ionic bonding between the cationic clay and anionic CNF.

    Lignin nanoparticles were testified to enhance the colloidal stability and dispersity of carboxylated CNF in dispersions, and showed a remarkable strengthening and stiffening effect on the matrix of CNF. The mechanical properties of lignin-CNF films were superior to previously reported polymer/nanoparticle-CNF composites, such as polyvinyl alcohol-CNF films and even reduced graphene oxide-CNF films.

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  • 49.
    Liu, Yingxin
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Wallenberg Wood Science Center, Sweden.
    Stoeckel, Daniela
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Gordeyeva, Korneliya
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Agthe, Michael
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Schütz, Christina
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Fall, Andreas B.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Nanoscale Assembly of Cellulose Nanocrystals during Drying and Redispersion2018In: ACS Macro Letters, E-ISSN 2161-1653, Vol. 7, no 2, p. 172-177Article in journal (Refereed)
    Abstract [en]

    We have followed the structural evolution during evaporation-induced self-assembly of sulfonated cellulose nanocrystal (CNC) in the presence of H+ and Li+ counterions by small-angle X-ray scattering. Drying of CNC-H dispersions results in ordered films that could not be readily redispersed, while the CNC-Li films were disordered and prone to reswelling and redispersion. The scaling of the separation distance (d) between CNC particles and the particle concentration (c) shows that the CNC-H dispersions display a unidimensional contraction of the nematic structure (d alpha c(-1)) during drying, while the CNC-Li dispersions consolidate isotropically (d alpha c(-1/3)), which is characteristic for hydrogels with no preferential orientation. Temporal evolution of the structure factor and complementary dynamic light-scattering measurements show that CNC-Li is more aggregated than CNC-H during evaporation-induced assembly. Insights on the structural evolution during CNC assembly and redispersion can promote development of novel and optimized processing routes of nanocellulose-based materials.

  • 50. Isogai, Akira
    et al.
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). The University of Tokyo, Japan.
    Preparation of cellulose nanofibers using green and sustainable chemistry2018In: Current Opinion in Green and Sustainable Chemistry, E-ISSN 2452-2236 , Vol. 12, p. 15-21Article, review/survey (Refereed)
    Abstract [en]

    The development of green and sustainable routes to liberate crystalline cellulose microfibrils from plant cell walls is of utmost importance to enable development of the large-scale production of sustainable nanomaterials based on renewable resources. The catalytic oxidation of cellulose using 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO) under aqueous conditions at room temperature is a position-selective and efficient chemical modification. TEMPO-mediated oxidation of plant cellulose fibers, followed by gentle mechanical disintegration of the oxidized celluloses in water, results in the formation of TEMPO-oxidized cellulose nanofibers (TOCNs) with homogeneous widths (similar to 3 nm) and high aspect ratios. TOCNs are characteristic bio-based materials with high tensile strengths and elastic moduli. Sodium carboxylate groups are densely present on the crystalline TOCN surfaces and can undergo counterion exchange from sodium to other metal or alkylammonium ions under aqueous conditions. The hydrophilic/hydrophobic, stable/biodegradable, super deodorant, catalytic, and other functionalities of TOCNs can be controlled through counterion exchange.

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