| 1. |
- Borges, Ana C., et al.
(author)
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Nanofibrillated cellulose composite hydrogel for the replacement of the Nucleus Pulposus
- 2011
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In: Acta Biomaterialia. - : Elsevier BV. - 1742-7061 .- 1878-7568. ; 7:9, s. 3412-3421
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Journal article (peer-reviewed)abstract
- The swelling and compressive mechanical behavior as well as the morphology and biocompatibility of composite hydrogels based on Tween® 20 trimethacrylate (T3), N-vinyl-2-pyrrolidone (NVP) and nanofibrillated cellulose (NFC) were assessed in the present study. The chemical structure of T3 was verified by FTIR and 1H NMR and the degree of substitution (DS) was found to be around 3. Swelling ratios of neat hydrogels composed of different concentrations of T3 and NVP were found to range from 1.5 to 5.7 with decreasing concentration of T3. Various concentrations of cellulose nanofibrils (0.2 to 1.6 wt%) were then used to produce composite hydrogels that showed lower swelling ratios than neat ones for a given T3 concentration. Neat and composite hydrogels exhibited typical non-linear response under compression. All composite hydrogels showed an increase in elastic modulus compared to neat hydrogel of about 3 to 8-fold, reaching 18 kPa at 0% strain and 62 kPa at 20% strain for the hydrogel with the highest NFC content. All hydrogels presented a porous and homogeneous structure, with interconnected pore cells of around 100 nm in diameter. The hydrogels are biocompatible. The results of this study demonstrate that composite hydrogels reinforced with NFC may be viable as nucleus pulposus implant due to their adequate swelling ratio that may restore annulus fibrosus loading and their increased mechanical properties that could possibly restore the height of intervertebral discs.
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| 2. |
- Even, Anais, et al.
(author)
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Influence of radical photoinitiator content on UV curing process and UV-cured hybrid sol–gel films
- 2020
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In: JCT Research. - : Springer. - 1547-0091 .- 2168-8028. ; 17:2, s. 333-343
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Journal article (peer-reviewed)abstract
- Hybrid sol–gel coatings are widely used as protective layers for aluminum alloys because of their barrier abilities. This study aims at explaining the barrier properties of a sol–gel coating based on alkyltrimethoxysilane and methacrylate resin by its film structure. This approach was examined by modifying one photopolymerization parameter, e.g., by varying the content of radical photoinitiator. By neutral salt spray test and electrochemical impedance spectroscopy, the barrier properties are highlighted. The film structure is related to thermomechanical properties of films whose glass transition temperature and elastic modulus are measured by dynamic mechanical analysis and nanoindentation, respectively. On a finer scale, conversion of methacrylate functions calculated from Fourier transform infrared spectroscopy has given information on the chemical structure of films. The morphology of these coatings is studied by scanning electron microscopy, transmission electron microscopy, atomic force microscopy operating in tapping mode, and X-ray diffraction. Results revealed that formulations containing between 3 and 9 wt% of radical photoinitiator exhibit the maximal conversion of methacrylate functions and, at a microscopic scale, a homogeneous coating where the two organic and inorganic networks are well interpenetrated. This hybrid sol–gel microstructure corresponds to the highest glass transition temperature and the highest mechanical characteristics (elastic modulus, E and hardness, H) and the highest protection performance. This results in the best barrier properties, and thus the highest corrosion resistance.
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| 3. |
- Liu, Peng, et al.
(author)
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Cellulose and chitin nanomaterials for capturing silver ions (Ag+) from water via surface adsorption
- 2014
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In: Cellulose. - : Springer Science and Business Media LLC. - 0969-0239 .- 1572-882X. ; 21:1, s. 449-461
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Journal article (peer-reviewed)abstract
- The study explores the potential of cellulose nanocrystals (CNC), cellulose nanofibers (CNF) and chitin nanocrystals (ChNC) isolated from bioresidues to remove silver ions from contaminated water. Zeta sizer studies showed negatively charged surfaces for CNC and CNF isolated from cellulose sludge in the acidic and alkaline pHs, whereas ChNC isolated from crab shell residue showed either positive or negative charges depending on pH conditions. Model water containing silver ions showed a decrease in Ag+ ion concentration (measured by inductively coupled plasma-optical emission spectrometer; inductively coupled plasma mass spectrometry), after treatment with CNC, CNF and ChNC suspensions. The highest Ag+ ion removal was measured near neutral pH for CNC, being 34.4 mg/g, corresponding to 64 % removal. ChNC showed 37 % and CNF showed 27 % removal of silver ions. The WDX (wavelength dispersive X-ray analysis) and XPS (X-ray photoelectron spectroscopy) analysis confirmed the presence of silver ions on the surface of the nanocellulose and nanochitin after adsorption. Surface adsorption on the nanoparticles via electrostatic interactions is considered to be the prominent mechanism of heavy metal ion capture from aqueous medium, with CNC with negative surface charge and negatively charged functional groups being most favourable for the adsorption of positively charged Ag+ ions compared to other native bionanomaterials
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| 4. |
- Sehaqui, Houssine, et al.
(author)
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Enhancing adsorption of heavy metal ions onto biobased nanofibers from waste pulp residues for application in wastewater treatment
- 2014
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In: Cellulose. - : Springer Science and Business Media LLC. - 0969-0239 .- 1572-882X. ; 21:4, s. 2831-2844
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Journal article (peer-reviewed)abstract
- Biobased nanofibers are increasingly considered in purification technologies due to their high mechanical properties, high specific surface area, versatile surface chemistry and natural abundance. In this work, cellulose and chitin nanofibers functionalized with carboxylate entities have been prepared from pulp residue (i.e., a waste product from the pulp and paper production) and crab shells, respectively, by chemically modifying the initial raw materials with the 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) mediated oxidation reaction followed by mechanical disintegration. A thorough investigation has first been carried out in order to evaluate the copper(II) adsorption capacity of the oxidized nanofibers. UV spectrophotometry, X-ray photoelectron spectroscopy and wavelength dispersive X-rays analysis have been employed as characterization tools for this purpose. Pristine nanofibers presented a relatively low content of negative charges on their surface thus adsorbing a low amount of copper(II). The copper adsorption capacity of the nanofibers was enhanced due to the oxidation treatment since the carboxylate groups introduced on the nanofibers surface constituted negative sites for electrostatic attraction of copper ions (Cu2+). The increase in copper adsorption on the nanofibers correlated both with the pH and carboxylate content and reached maximum values of 135 and 55 mg g−1 for highly oxidized cellulose and chitin nanofibers, respectively. Furthermore, the metal ions could be easily removed from the contaminated nanofibers through a washing procedure in acidic water. Finally, the adsorption capacity of oxidized cellulose nanofibers for other metal ions, such as nickel(II), chromium(III) and zinc(II), was also demonstrated. We conclude that TEMPO oxidized biobased nanofibers from waste resources represent an inexpensive and efficient alternative to classical sorbents for heavy metal ions removal from contaminated water.
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| 5. |
- Stefelova, Jana, et al.
(author)
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Drying and Pyrolysis of Cellulose Nanofibers from Wood, Bacteria, and Algae for Char Application in Oil Absorption and Dye Adsorption
- 2017
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In: ACS Sustainable Chemistry and Engineering. - : AMER CHEMICAL SOC. - 2168-0485. ; 5:3, s. 2679-2692
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Journal article (peer-reviewed)abstract
- Native cellulose nanofibers (CNF) constitute an abundant resource for pyrolysis leading to char materials offering a wide range of properties and application possibilities. With the aim to produce chars having large surface area and pore volume for dyes adsorption and oil absorption, respectively, we herein explore the slow pyrolysis process of cellulose nanofibers from wood, Cladophora algae and bacteria that were subjected to various drying routes. Whereas algae CNF with their large crystallites lead to high surface area (S-BET) substrates using conventional drying from aqueous suspension, CNF from wood having smaller crystallites requires drying from solvents to reach high S-BET substrates, which results in chars with a good adsorption capacity for both anionic and cationic dyes. Moreover, the porosity of the CNF substrate can be tuned via an ice-templating freeze-drying procedure reaching values as high as 99.7% and corresponding chars capable of absorbing 64-120 g g(-1) of various oils and organic solvents. Besides the absorption/adsorption properties of the chars, we report effects of CNF source and structure on the thermal properties assessed by thermogravimetric and thermomechanical analyses, differential scanning calorimetry, and mass spectrometry, and we identified over 20 decomposition products and 3 expansion events occurring during CNF pyrolysis.
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