| 1. |
- Li, T., et al.
(författare)
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Anisotropic, lightweight, strong, and super thermally insulating nanowood with naturally aligned nanocellulose
- 2018
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Ingår i: Science Advances. - : American Association for the Advancement of Science. - 2375-2548. ; 4:3
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Tidskriftsartikel (refereegranskat)abstract
- There has been a growing interest in thermal management materials due to the prevailing energy challenges and unfulfilled needs for thermal insulation applications. We demonstrate the exceptional thermal management capabilities of a large-scale, hierarchal alignment of cellulose nanofibrils directly fabricated fromwood, hereafter referred to as nanowood. Nanowood exhibits anisotropic thermal properties with an extremely low thermal conductivity of 0.03W/m·K in the transverse direction (perpendicular to the nanofibrils) and approximately two times higher thermal conductivity of 0.06W/m·K in the axial direction due to the hierarchically aligned nanofibrilswithin the highly porous backbone. The anisotropy of the thermal conductivity enables efficient thermal dissipation along the axial direction, thereby preventing local overheating on the illuminated side while yielding improved thermal insulation along the backside that cannot be obtained with isotropic thermal insulators. The nanowood also shows a low emissivity of <5% over the solar spectrum with the ability to effectively reflect solar thermal energy. Moreover, the nanowood is lightweight yet strong, owing to the effective bonding between the aligned cellulose nanofibrils with a high compressive strength of 13 MPa in the axial direction and 20MPa in the transverse direction at 75% strain, which exceeds other thermal insulation materials, such as silica and polymer aerogels, Styrofoam, and wool. The excellent thermal management, abundance, biodegradability, high mechanical strength, low mass density, and manufacturing scalability of the nanowood make this material highly attractive for practical thermal insulation applications.
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| 2. |
- Sundqvist, Bertil, et al.
(författare)
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Physical properties of pressure polymerized C60
- 1996
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Ingår i: Proceedings of the Symposium on Recent Advances in the Chemistry and Physics of Fullerenes and Related Materials. - Pennington, NJ : Electrochemical Society, Incorporated. - 1566771625 ; , s. 1014-1028
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Konferensbidrag (refereegranskat)
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| 3. |
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| 4. |
- Brusentsev, Yury, et al.
(författare)
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Photocross-Linkable and Shape-Memory Biomaterial Hydrogel Based on Methacrylated Cellulose Nanofibres
- 2023
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Ingår i: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 24:8, s. 3835-3845
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Tidskriftsartikel (refereegranskat)abstract
- In the context of three-dimensional (3D) cell culture and tissue engineering, 3D printing is a powerful tool for customizing in vitro 3D cell culture models that are critical for understanding the cell-matrix and cell-cell interactions. Cellulose nanofibril (CNF) hydrogels are emerging in constructing scaffolds able to imitate tissue in a microenvironment. A direct modification of the methacryloyl (MA) group onto CNF is an appealing approach to synthesize photocross-linkable building blocks in formulating CNF-based bioinks for light-assisted 3D printing; however, it faces the challenge of the low efficiency of heterogenous surface modification. Here, a multistep approach yields CNF methacrylate (CNF-MA) with a decent degree of substitution while maintaining a highly dispersible CNF hydrogel, and CNF-MA is further formulated and copolymerized with monomeric acrylamide (AA) to form a super transparent hydrogel with tuneable mechanical strength (compression modulus, approximately 5-15 kPa). The resulting photocurable hydrogel shows good printability in direct ink writing and good cytocompatibility with HeLa and human dermal fibroblast cell lines. Moreover, the hydrogel reswells in water and expands to all directions to restore its original dimension after being air-dried, with further enhanced mechanical properties, for example, Young’s modulus of a 1.1% CNF-MA/1% PAA hydrogel after reswelling in water increases to 10.3 kPa from 5.5 kPa.
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| 5. |
- Dahlström, Christina, 1977-, et al.
(författare)
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Ion conductivity through TEMPO-mediated oxidated and periodate oxidated cellulose membranes
- 2020
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Ingår i: Carbohydrate Polymers. - : ELSEVIER SCI LTD. - 0144-8617 .- 1879-1344. ; 233
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Tidskriftsartikel (refereegranskat)abstract
- Cellulose in different forms is increasingly used due to sustainability aspects. Even though cellulose itself is an isolating material, it might affect ion transport in electronic applications. This effect is important to understand for instance in the design of cellulose-based supercapacitors. To test the ion conductivity through membranes made from cellulose nanofibril (CNF) materials, different electrolytes chosen with respect to the Hofmeister series were studied. The CNF samples were oxidised to three different surface charge levels via 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO), and a second batch was further cross-linked by periodate oxidation to increase wet strength and stability. The outcome showed that the CNF pre-treatment and choice of electrolyte are both crucial to the ion conductivity through the membranes. Significant specific ion effects were observed for the TEMPO-oxidised CNF. Periodate oxidated CNF showed low ion conductivity for all electrolytes tested due to an inhibited swelling caused by the crosslinking reaction.
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| 6. |
- Eriksson, Axl, et al.
(författare)
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Synthesis of Well-Ordered Functionalized Silicon Microwires Using Displacement Talbot Lithography for Photocatalysis
- 2024
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Ingår i: ACS Omega. - 2470-1343. ; 9:18, s. 20623-20628
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Tidskriftsartikel (refereegranskat)abstract
- Metal-assisted chemical etching (MACE) is a cheap and scalable method that is commonly used to obtain silicon nano- or microwires but lacks spatial control. Herein, we present a synthesis method for producing vertical and highly periodic silicon microwires, using displacement Talbot lithography before wet etching with MACE. The functionalized periodic silicon microwires show 65% higher PEC performance and 2.3 mA/cm2 higher net photocurrent at 0 V compared to functionalized, randomly distributed microwires obtained by conventional MACE at the same potentials.
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| 7. |
- Horvath, Andrew T., et al.
(författare)
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Adsorption of highly charged polyelectrolytes onto an oppositely charged porous substrate
- 2008
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 24:15, s. 7857-7866
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Tidskriftsartikel (refereegranskat)abstract
- The adsorption behavior of highly charged cationic polyelectrolytes onto porous substrates is electrostatic in nature and has been shown to be highly dependent on the poly electrolyte properties. Copolymers of acrylamide (AM) and diallyldimethylammonium chloride (DADMAC) were synthesized to have a range of macromolecular properties (i.e., charge density and molecular mass). Traditional titration methods have been complemented by fluorescence labeling techniques that were developed to directly observe the extent that fluorescently labeled poly(AM-co-DADMAC) adsorbs into the pore structure of a cellulosic substrate. Although contributing to the electrostatic driving force, the charge density acts to limit adsorption to the outermost surface under electrolyte-free conditions. However, adsorption into the pores can occur if both the molecular mass and charge density of poly(AM-co-DADMAC) are sufficiently low. Adsorption initially increases as the electrolyte concentration is increased. However, the electrostatic persistence length of poly(AM-co-DADMAC) restricts the polyelectrolyte from entering the pores. Therefore, changes in the adsorption behavior at moderate electrolyte concentrations have been attributed to swelling of the polyelectrolyte layer at the fiber exterior. The adsorption behavior changes again at high electrolyte concentrations such that poly(AMco-DADMAC) could adsorb into the pore structure. This occurred when the electrolyte concentration was sufficient to screen the electrostatic persistence length of poly(AM-co-DADMAC), provided that the entropie driving force for adsorption still existed. It is suggested that adsorption into the pore structure is a kinetic process that is governed by localized electrostatic interactions between poly(AM-co-DADMAC) and the charges located within the pores.
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| 8. |
- Horvath, Andrew T., et al.
(författare)
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Adsorption of low charge density polyelectrolytes to an oppositely charged porous substrate
- 2008
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 24:13, s. 6585-6594
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Tidskriftsartikel (refereegranskat)abstract
- The adsorption behavior of a low charge density cationic polyelectrolyte to cellulosic fibers has been studied. Cationic dextran served as a model polyelectrolyte, as it can be prepared over a range in molecular mass and charge density. The adsorption behavior of the cationic dextran was measured in electrolyte-free conditions using polyelectrolyte titration techniques. By fluorescent labeling the cationic dextran, the extent to which adsorption occurs inside the porous structure was further determined by fluorescent confocal laser scanning microscopy. Cationic dextran having a sufficiently low charge density adsorbed into the pores, although the extent the cationic dextran adsorbed was governed by the molecular mass. The adsorption behavior of the cationic dextran was also studied in various electrolyte concentrations. The adsorbed mass monotonically decreased with increasing electrolyte, as the electrostatic interaction with the substrate was more effectively screened. This behavior also suggests that the interactions between adsorbed polyelectrolyte chains, i.e. lateral correlation effects, are negligible for low charge density polyelectrolytes. Finally, the effect of having a preadsorbed layer of cationic dextran on the adsorption behavior was determined in electrolytefree conditions using fluorescent double staining techniques. The preadsorbed cationic dextran had almost no effect on the adsorption of low molecular mass fractions. Low molecular mass fractions directly adsorbed into the pore structure, as opposed to adsorbing to a free surface and diffusing into the pores. It was also shown that cationic dextran can be selectively adsorbed to different locations, such that the surface of a porous substrate can be treated uniquely from the bulk.
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