| 11. |
|
|
| 12. |
- Dahlström, Christina, 1977-, et al.
(författare)
-
Regenerated cellulose properties tailored for optimized triboelectric output and the effect of counter-tribolayers
- 2024
-
Ingår i: Cellulose. - : Springer Nature. - 0969-0239 .- 1572-882X. ; 31:4, s. 2047-2061
-
Tidskriftsartikel (refereegranskat)abstract
- Cellulose has shown great potential in the development of green triboelectric nanogenerators. Particularly, regenerated cellulose (R-cellulose) has shown remarkably high output power density but the structural features and key parameters that explain such superior performance remain unexplored. In this work, wood cellulose fibers were dissolved in a LiOH(aq)-based solvent to produce a series of R-cellulose films. Regeneration in different alcohols (from methanol to n-pentanol) was performed and the films’ structural features and triboelectric performance were assessed. Nonsolvents of increased hydrophobicity led to R-cellulose films with a more pronounced (1–10) diffraction peak. An open-circuit voltage (VOC) of up to ca. 260 V and a short-circuit current (ISC) of up to ca. 150 µA were measured for R-cellulose against polytetrafluoroethylene (as negative counter-layer). However, R-cellulose showed an increased VOC of 175% (from 88.1 V) against polydimethylsiloxane when increasing the alcohol hydrocarbon chain length from methanol to n-pentanol. The corresponding ISC and output power also increased by 76% (from 89.9 µA) and by 382% (from 8.8 W m–2), respectively. The higher R-cellulose hydrophilicity, combined with soft counter-tribolayer that follow the surface structures increasing the effective contact area, are the leading reasons for a superior triboelectric performance.
|
|
| 13. |
- Dahlström, Christina, 1977-, et al.
(författare)
-
Triboelectric Performance Of Regenerated Cellulose
- 2023
-
Ingår i: Book of Abstracts EPNOE 2023. - : Graz University of Technology. ; , s. 116-
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Cellulose has shown great potential in the development of green triboelectric nanogenerators (TENG) [1]. Particularly, regenerated cellulose (R-cellulose) has shown remarkably high output power density but the structural features and key parameters that explain such superior performance remain unexplored. In this work, wood cellulose fibers were dissolved in a LiOH(aq)-based solvent to produce a series of R-cellulose films. Regeneration in different alcohols (from methanol to n-pentanol) was performed and the films’ structural features and triboelectric performance were assessed. Nonsolvents of increased hydrophobicity led to R-cellulose films with higher hydrophilic character; the films showed a (1- 10) diffraction peak of larger amplitude and higher apparent crystallinity. An open-circuit voltage (VOC) of up to ca. 260 V and a short-circuit current (ISC) of up to ca. 150 μA were measured for R-cellulose against polytetrafluoroethylene (as negative counter-layer). However, R-cellulose showed an increased VOC of 175% (from 88.1 V) against polydimethylsiloxane from methanol to n-pentanol. The corresponding ISC and output power also increased by 76% (from 89.9 μA) and by 382% (from 8.8 W m–2), respectively. The higher R-cellulose hydrophilicity, combined with soft counter-layer that follow the surface structures increasing the effective contact area, are the leading reasons for a superior triboelectric performance.[1] Zhang, R., Dahlström, C., Zou, H., Jonzon, J., Hummelgård, M., Örtegren, J., Blomquist, N., Yang, Y., Andersson, H., Olsen, M., Norgren, M., Olin, H. & Wang, Z.L. Adv. Mater. 32, 2002824, 2020; https://doi.org/10.1002/adma.202002824
|
|
| 14. |
- dos Santos, Tiago, et al.
(författare)
-
How does a non-ionic hydrophobically modified telechelic polymer interact with a non-ionic vesicle? Rheological aspects
- 2008
-
Ingår i: Colloids and Surfaces A: Physicochemical and Engineering Aspects. - : Elsevier BV. - 0927-7757. ; 319:1-3, s. 173-179
-
Konferensbidrag (refereegranskat)abstract
- The association between hydrophobically modified polyethylene glycol, HM-PEG, and non-ionic vesicles of tetraethylene glycol monododecyl ether, C12E4, was investigated. HM-PEG is in a triblock form, with an alkyl chain attached to each hydrophilic polymer-end. Such polymer structure is denoted as telechelic. The vesicle average radius was measured by self-diffusion measurements. The system exhibits both a monophasic gel and biphasic regions. The monophasic region was characterized from a theological point of view. We argue that the gel formation is due to the presence. of polymer crosslinks between different surfactant aggregates, once the polymer's hydrophobic moieties may adsorb into the vesicle bilayer. This association is strongly concentration dependent which is reflected in the monotonic increase of the storage modulus, relaxation time and shear viscosity with the addition of surfactant and/or polymer.
|
|
| 15. |
- Duarte, H., et al.
(författare)
-
On the Valorization of Arbutus unedo L. Pomace : Polyphenol Extraction and Development of Novel Functional Cookies
- 2023
-
Ingår i: Foods. - : MDPI. - 2304-8158. ; 12:19
-
Tidskriftsartikel (refereegranskat)abstract
- The fruits of Arbutus unedo L. have a crimson colour and are enriched with remarkable concentrations of bioactive compounds such as anthocyanins and polyphenols. These fruits are commonly used in the production of a Portuguese Protected Geographical Indication distillate called “Aguardente de Medronho”. During this process, a solid pomace is generated and presently discarded without valuable applications. In this work, two strategies have been developed for the valorisation of A. unedo pomace. The first approach considers the extraction of polyphenols from this by-product through the optimization of an ultrasound-assisted method using a Box-Behnken design coupled with response surface methodology. The results indicate that the temperature and the percentage of methanol, along with their interaction, significantly influence the total concentration of polyphenols and the antioxidant activity of the extracts obtained. The optimal conditions identified consider the extraction of 0.5 g of sample with 20 mL of a solvent containing 74% MeOH (aq), at a pH of 4.8, maintained at 70 °C for 15 min. On the other hand, the second valorisation strategy considered the use of A. unedo pomace in the development of functional cookies. The incorporation of 15–20% pomace in the cookie formulation was well-received by consumers. This incorporation results in an intake of ca. 6.55 mg of polyphenols per gram of cookie consumed, accompanied by an antioxidant activity of 4.54 mg Trolox equivalents per gram of cookie consumed. Overall, these results encourage the employment of A. unedo pomace either as a reliable source of extracts enriched in polyphenols or as a nutraceutical active ingredient in functional cookies, thereby positively impacting human health.
|
|
| 16. |
- Duarte, H., et al.
(författare)
-
Optimization of the extraction of polyphenols from Pinus pinaster residues using deep eutectic solvents : a sustainable approach
- 2023
-
Ingår i: Wood Science and Technology. - : Springer Nature. - 0043-7719 .- 1432-5225. ; 57:5, s. 1175-1196
-
Tidskriftsartikel (refereegranskat)abstract
- Abstract: In the present investigation, the optimization of a pressurized solid–liquid extraction of polyphenols from Pinus pinaster Aiton needles and bark residues has been carried out using new deep eutectic solvent systems (DES). A Box–Behnken design with response surface methodology was implemented, with six variables, including solid:liquid ratio, water content, temperature, extraction time, reactor closure state, and catalyst concentration. The DES consisting of levulinic acid: formic acid exhibited the highest content, and the optimal conditions were determined to be 0.10 g of residue in 10 mL of solvent (without water) and without catalyst, at 60 °C for 5 min. The method demonstrated excellent repeatability and intermediate precision, with a coefficient of variation of less than 5%. In addition, the antimicrobial and antioxidant activities of the polyphenol-enriched extracts were evaluated, obtaining a total reduction in S. aureus cell growth and remarkable antioxidant levels of 144.72 ± 4.24 and 161.01 ± 4.70 mg Trolox equivalents/gram for needle and bark residues, respectively. Under the optimized conditions, the new DES are remarkably superior to conventional solvents and can be recycled and reused, demonstrating that these systems have a promising environmental profile, making them valuable alternatives for biomass fractionation.
|
|
| 17. |
- Duarte, H., et al.
(författare)
-
Sustainable extraction of polyphenols from vine shoots using deep eutectic solvents : Influence of the solvent, Vitis sp., and extraction technique
- 2024
-
Ingår i: Talanta. - : Elsevier BV. - 0039-9140 .- 1873-3573. ; 267
-
Tidskriftsartikel (refereegranskat)abstract
- Vine shoots are the main by-products of grapevine pruning with no added value. In the present study, deep eutectic solvents (DESs) were used as alternatives to traditional chemical solvents, for the extraction of phytochemicals from grapevine shoots. Three levulinic acid-based DESs were tested for the first time, and their performance was compared to methanol (a standard chemical solvent) regarding the extraction of phenolic compounds from thirteen Vitis sp. shoots. Two extraction methods have been applied: ultrasound-assisted extraction and solid-liquid extraction. A total of eleven polyphenols which belongs to four families (proanthocyanins, stilbenes, hydroxycinnamic acids, and flavonols) have been identified and quantified in the extracts. The statistical analysis shows that the levulinic acid-based DES systems are novel and important alternatives to chemical solvents due to favourable eco-friendly properties and remarkable extraction performance of polyphenols. On the other hand, the ultrasound-assisted extraction technique has significantly increased the extraction rate in comparison to the solid-liquid extraction method with p-values lower than 0.05 for most compounds. The genetic factor has been shown to play an important role in the content of extracted polyphenols, being V. riparia pubescente the one that presented the highest concentrations of extracted polyphenols. Finally, the polyphenol-enriched extracts have proven important properties such as antioxidant activity and significant delay in bacteria growth against both gram-positive and gram-negative bacteria. It is important to note that, to the best of our knowledge, this is the first time that deep eutectic solvents have been used for the extraction of bioactive compounds from vine shoot residues.
|
|
| 18. |
- Duarte, H., et al.
(författare)
-
Ultrasound-Assisted Extraction of Polyphenols from Maritime Pine Residues with Deep Eutectic Solvents
- 2022
-
Ingår i: Foods. - : MDPI AG. - 2304-8158. ; 11:23
-
Tidskriftsartikel (refereegranskat)abstract
- Deep eutectic solvents represent an important alternative in the field of green solvents due to their low volatility, non-toxicity, and low synthesis cost. In the present investigation, we propose the production of enriched polyphenolic extracts from maritime pine forest residues via an ultrasound-assisted approach. A Box–Behnken experimental design with a response surface methodology was used with six variables to be optimized: solid-to-solvent ratio, water percentage, temperature and time of extraction, amplitude, and catalyst concentration. The mixture of levulinic and formic acids achieved the highest extraction yield of polyphenols from pine needle and bark biomass. In addition, the solid-to-solvent ratio was found to be the only influential variable in the extraction (p-value: 0.0000). The optimal conditions were established as: 0.1 g of sample in 10 mL of LA:FA (70:30%, v/v) with 0% water and 0 M H2SO4 heated to 30 °C and extracted during 40 min with an ultrasound amplitude of 80% at 37 kHz. The bioactive properties of polyphenol-enriched extracts have been proven with significant antioxidant (45.90 ± 2.10 and 66.96 ± 2.75 mg Trolox equivalents/g dw) and antimicrobial activities. The possibility to recycle and reuse the solvent was also demonstrated; levulinic acid was successfully recovered from the extracts and reused in novel extractions on pine residues. This research shows an important alternative to obtaining polyphenol-enriched extracts from forest residues that are commonly discarded without any clear application, thus opening an important window toward the valorization of such residues.
|
|
| 19. |
- Duarte, T. A. G., et al.
(författare)
-
A Glance at Novel Ionanofluids Incorporating Silk-Derived Carbon Dots
- 2024
-
Ingår i: Chemistry of Materials. - : American Chemical Society (ACS). - 0897-4756 .- 1520-5002. ; 36:3, s. 1136-1152
-
Tidskriftsartikel (refereegranskat)abstract
- One of the hallmarks of the current efforts in the field of thermal energy is heat transfer enhancement. Ionanofluids (INFs), a combination of nanomaterials and ionic liquids (ILs), are an appealing category of thermal fluids. In this work, we introduce sustainable INFs composed of carbon dots derived from Bombyx mori silk fibroin (SF) dispersed in a mixture of 1-butyl-3-methylimidazolium chloride (IL1) and 1-(4-sulfobutyl)-3-methylimidazolium triflate (IL2). The syntheses were performed at mild conditions, with reaction times of 3, 4, and 5 h, and without purification steps. The INFs display room-temperature emission in the visible spectral range with quantum yield values up to 0.09 and are essentially viscous fluids (G″ > G′). A marked shear thinning behavior is observed at high shear rates, particularly for the systems SFIL1IL2-3h and SFIL1IL2-4h. The INFs demonstrate relatively high heat capacity and thermal conductivity values in comparison to state-of-the-art INFs. Under suitable illumination conditions, the INFs can convert light into heat in an efficient manner, with photothermal conversion efficiencies of up to 28%, similar to other reported INFs. SFIL1IL2-5h exhibits remarkable stability over time within the range of working temperatures. This work paves the way for the development of new thermal fluids for enhanced heat transfer technologies using sustainable synthesis routes and natural raw precursor materials.
|
|
| 20. |
- Eivazi, Alireza, et al.
(författare)
-
On the development of all-cellulose capsules by vesicle-templated layer-by-layer assembly
- 2021
-
Ingår i: Polymers. - : MDPI AG. - 2073-4360. ; 13:4
-
Tidskriftsartikel (refereegranskat)abstract
- Polymeric multilayer capsules formed by the layer-by-layer (LbL) technique are interesting candidates for the purposes of storage, encapsulation, and release of drugs and biomolecules for pharmaceutical and biomedical applications. In the current study, cellulose-based core-shell particles were developed via the LbL technique alternating two cellulose derivatives, anionic carboxymethyl-cellulose (CMC), and cationic quaternized hydroxyethylcellulose ethoxylate (QHECE), onto a cationic vesicular template made of didodecyldimethylammonium bromide (DDAB). The obtained capsules were characterized by dynamic light scattering (DLS), ζ potential measurements, and high-resolution scanning electron microscopy (HR-SEM). DLS measurements reveal that the size of the particles can be tuned from a hundred nanometers with a low polydispersity index (deposition of 2 layers) up to micrometer scale (deposition of 6 layers). Upon the deposition of each cellulose derivative, the particle charge is reversed, and pH is observed to considerably affect the process thus demonstrating the electrostatic driving force for LbL deposition. The HR-SEM characterization suggests that the shape of the core-shell particles formed is reminiscent of the spherical vesicle template. The development of biobased nano-and micro-containers by the alternating deposition of oppositely charged cellulose derivatives onto a vesicle template offers several advantages, such as simplicity, reproducibility, biocompatibility, low-cost, mild reaction conditions, and high controllability over particle size and composition of the shell.
|
|
