| 1. |
- Kattge, Jens, et al.
(författare)
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TRY plant trait database - enhanced coverage and open access
- 2020
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Ingår i: Global Change Biology. - : Wiley-Blackwell. - 1354-1013 .- 1365-2486. ; 26:1, s. 119-188
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Tidskriftsartikel (refereegranskat)abstract
- Plant traits-the morphological, anatomical, physiological, biochemical and phenological characteristics of plants-determine how plants respond to environmental factors, affect other trophic levels, and influence ecosystem properties and their benefits and detriments to people. Plant trait data thus represent the basis for a vast area of research spanning from evolutionary biology, community and functional ecology, to biodiversity conservation, ecosystem and landscape management, restoration, biogeography and earth system modelling. Since its foundation in 2007, the TRY database of plant traits has grown continuously. It now provides unprecedented data coverage under an open access data policy and is the main plant trait database used by the research community worldwide. Increasingly, the TRY database also supports new frontiers of trait-based plant research, including the identification of data gaps and the subsequent mobilization or measurement of new data. To support this development, in this article we evaluate the extent of the trait data compiled in TRY and analyse emerging patterns of data coverage and representativeness. Best species coverage is achieved for categorical traits-almost complete coverage for 'plant growth form'. However, most traits relevant for ecology and vegetation modelling are characterized by continuous intraspecific variation and trait-environmental relationships. These traits have to be measured on individual plants in their respective environment. Despite unprecedented data coverage, we observe a humbling lack of completeness and representativeness of these continuous traits in many aspects. We, therefore, conclude that reducing data gaps and biases in the TRY database remains a key challenge and requires a coordinated approach to data mobilization and trait measurements. This can only be achieved in collaboration with other initiatives.
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| 2. |
- Antonio, Capezza, et al.
(författare)
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Preparation and Comparison of Reduced Graphene Oxide and Carbon Nanotubes as Fillers in Conductive Natural Rubber for Flexible Electronics
- 2019
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Ingår i: Omega. - : American Chemical Society (ACS). - 0030-2228 .- 1541-3764. ; 4:2
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Tidskriftsartikel (refereegranskat)abstract
- Conductive natural rubber (NR) nanocomposites were prepared by solvent-casting suspensions of reduced graphene oxide(rGO) or carbon nanotubes (CNTs), followed by vulcanization of the rubber composites. Both rGO and CNT were compatible as fillers in the NR as well as having sufficient intrinsic electrical conductivity for functional applications. Physical (thermal) and chemical reduction of GO were investigated, and the results of the reductions were monitored by X-ray photoelectron spectroscopy for establishing a reduction protocol that was useful for the rGO nanocomposite preparation. Field-emission scanning electron microscopy showed that both nanofillers were adequately dispersed in the main NR phase. The CNT composite displays a marked mechanical hysteresis and higher elongation at break, in comparison to the rGO composites for an equal fraction of the carbon phase. Moreover, the composite conductivity was always ca. 3-4 orders of magnitude higher for the CNT composite than for the rGO composites, the former reaching a maximum conductivity of ca. 10.5 S/m, which was explained by the more favorable geometry of the CNT versus the rGO sheets. For low current density applications though, both composites achieved the necessary percolation and showed the electrical conductivity needed for being applied as flexible conductors for a light-emitting diode.
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| 3. |
- Birdsong, Björn K., et al.
(författare)
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Large-scale synthesis of 2D-silica (SiOx) nanosheets using graphene oxide (GO) as a template material
- 2023
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Ingår i: Nanoscale. - : Royal Society of Chemistry (RSC). - 2040-3364 .- 2040-3372. ; 15:31, s. 13037-13048
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Tidskriftsartikel (refereegranskat)abstract
- Graphene oxide (GO) was used in this study as a template to successfully synthesize silicon oxide (SiOx) based 2D-nanomaterials, adapting the same morphological features as the GO sheets. By performing a controlled condensation reaction using low concentrations of GO (<0.5 wt%), the study shows how to obtain 2D-nanoflakes, consisting of GO-flakes coated with a silica precursor that were ca. 500 nm in lateral diameter and ca. 1.5 nm in thickness. XPS revealed that the silanes had linked covalently with the GO sheets at the expense of the oxygen groups present on the GO surface. The GO template was shown to be fully removable through thermal treatment without affecting the nanoflake morphology of the pure SiOx-material, providing a methodology for large-scale preparation of SiOx-based 2D nanosheets with nearly identical dimensions as the GO template. The formation of SiOx sheets using a GO template was investigated for two different silane precursors, (3-aminopropyl) triethoxysilane (APTES) and tetraethyl orthosilicate (TEOS), showing that both precursors were capable of accurately templating the graphene oxide template. Molecular modeling revealed that the choice of silane affected the number of layers coated on the GO sheets. Furthermore, rheological measurements showed that the relative viscosity was significantly affected by the specific surface area of the synthesized particles. The protocol used showed the ability to synthesize these types of nanoparticles using a common aqueous alcohol solvent, and yield larger amounts (∼1 g) of SiOx-sheets than what has been previously reported.
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| 4. |
- Buyuktas, Duygu, et al.
(författare)
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A screen-printed electrode modified with gold nanoparticles/ cellulose nanocrystals for electrochemical detection of 4,4'-methylene diphenyl diamine
- 2023
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Ingår i: Heliyon. - : Elsevier BV. - 2405-8440. ; 9:4
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Tidskriftsartikel (refereegranskat)abstract
- Developing simple, cost-effective, easy-to-use, and reliable analytical devices if of utmost importance for the food industry for rapid in-line checks of their products that must comply with the provisions set by the current legislation. The purpose of this study was to develop a new electrochemical sensor for the food packaging sector. More specifically, we propose a screen -printed electrode (SPE) modified with cellulose nanocrystals (CNCs) and gold nanoparticles (AuNPs) for the quantification of 4,4'-methylene diphenyl diamine (MDA), which is one of the most important PAAs that can transfer from food packaging materials into food stuffs. The electrochemical performance of the proposed sensor (AuNPs/CNCs/SPE) in the presence of 4,4'- MDA was evaluated using cyclic voltammetry (CV). The modified AuNPs/CNCs/SPE showed the highest sensitivity for 4,4'-MDA detection, with a peak current of 9.81 mu A compared with 7.08 mu A for the bare SPE. The highest sensitivity for 4,4'-MDA oxidation was observed at pH = 7, whereas the detection limit was found at 57 nM and the current response of 4,4'-MDA rose linearly as its concentration increased from 0.12 mu M to 100 mu M. Experiments using real packaging materials revealed that employing nanoparticles dramatically improved both the sensitivity and the selectivity of the sensor, which can be thus considered as a new analytical tool for quick, simple, and accurate measurement of 4,4 '-MDA during converting operations.
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| 5. |
- Buyuktas, Duygu, et al.
(författare)
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Development of a nano-modified glassy carbon electrode for the determination of 2,6-diaminotoluene (TDA)
- 2021
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Ingår i: FOOD PACKAGING AND SHELF LIFE. - : ELSEVIER. - 2214-2894. ; 29
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Tidskriftsartikel (refereegranskat)abstract
- The objective of this study was to improve the overall performance of a glassy carbon electrode (GCE) for the detection of 2,6-diaminotoluene (TDA), a possibly carcinogenic primary aromatic amines (PAAs) that poses a serious risk for the consumer' health because they can transfer from multilayer food packages including adhesives based on aromatic polyurethane (PU) systems, to the food. The modification of the electrode surface was made by means of multi-walled carbon nanotubes (MWCNTs) and mesopomus carbon nanoparticles (MCNs). The MWCNTs-MCNs/GCE allowed achieving the best performance in terms of sensitivity, as revealed by cyclic voltammetry - CV, with an oxidation peak of 20.95 mu A over 0.079 mu A of the bare GCE. The pH of the medium influenced the oxidation of 2,6-TDA, with highest sensitivity at pH similar to 7. Amperometry experiments led to an estimated detection limit of 0.129 mu M, and three linear ranges were obtained for 2,6-TDA: 0.53-11.37 mu M, 11.37-229.36 mu M, and 229.36-2326.60 mu M. Chronoamperometry experiments combined with Cottrell's theory allowed estimating a diffusion coefficient of 2,6-TDA of 1.34 x 10(-4) cm(2) s(-1). The number of electrons (n similar to 1) involved in the catalytic oxidation of 2,6-TDA was determined according to the Lavimn's theory. Real sample tests demonstrated that the modification of the sensor using nanoparticls allowed to obtain a highly sensitive and selective sensor, which can possibly used as an alternative analytical device for the rapid, easy, and reliable determination of 2,6-TDA.
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| 6. |
- Cozzolino, Carlo A., et al.
(författare)
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Dye release behavior from polyvinyl alcohol films in a hydro-alcoholic medium : Influence of physicochemical heterogeneity
- 2012
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Ingår i: Colloids and Surfaces A. - : Elsevier BV. - 0927-7757 .- 1873-4359. ; 403, s. 45-53
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we investigated the release kinetics of a model drug-like compound (Coomassie brilliant blue) from polyvinyl alcohol (PVOH) films into a hydro-alcoholic solution as a function of the physicochemical properties of the polymer matrix. After 33 days of monitoring, the total amount released ranged from 10% for the high hydrolysis degree/low molecular weight PVOH films to 60% for the low hydrolysis degree/low molecular weight films. Mathematical modeling allowed for an estimation of the two diffusion coefficients (D 1 and D 2) that characterized the release profile of the dye from the films. The degree of hydrolysis dramatically affected both the morphology and the physical structure of the polymer network. A high hydroxyl group content was also associated with the shifting of second order and first order transitions toward higher temperatures, with a concurrent increase in crystallinity. Moreover, the higher the degree of hydrolysis, the higher the affinity of the polymer to the negatively charged molecule dye. Selection of the polymer matrix based on physicochemical criteria may help in achieving different release patterns, thereby representing the first step for the production of polymer systems with modulated release properties.
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| 7. |
- Cozzolino, Carlo A., et al.
(författare)
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Microfibrillated cellulose and borax as mechanical, O-2-barrier, and surface-modulating agents of pullulan biocomposite coatings on BOPP
- 2016
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Ingår i: Carbohydrate Polymers. - : Elsevier. - 0144-8617 .- 1879-1344. ; 143, s. 179-187
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Tidskriftsartikel (refereegranskat)abstract
- Multifunctional composite coatings on bi-oriented polypropylene (BOPP) films were obtained using borax and microfibrillated cellulose (MFC) added to the main pullulan coating polymer. Spectroscopy analyses suggested that a first type of interaction occurred via hydrogen bonding between the C-6-OH group of pullulan and the hydroxyl groups of boric acid, while monodiol and didiol complexation represented a second mechanism. The deposition of the coatings yielded an increase in the elastic modulus of the entire plastic substrate (from similar to 2 GPa of the neat BOPP to similar to 3.1 GPa of the P/B+/MFC-coated BOPP). The addition of MFC yielded a decrease of both static and kinetic coefficients of friction of approximately 22% and 25%, respectively, as compared to the neat BOPP. All composite coatings dramatically increased the oxygen barrier performance of BOPP, especially under dry conditions. The deposition of the high hydrophilic coatings allowed to obtain highly wettable surfaces (water contact angle of similar to 18 degrees).
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| 8. |
- Ghaani, Masoud, et al.
(författare)
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A bionanocomposite- modified glassy carbon electrode for the determination of 4,4 0-methylene diphenyl diamine
- 2018
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Ingår i: Analytical Methods. - : Royal Society of Chemistry. - 1759-9660 .- 1759-9679. ; 10:34
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Tidskriftsartikel (refereegranskat)abstract
- A nanosensor based on a glassy carbon electrode modified with the biopolymer chitosan, multi-wall carbon nanotubes, and gold nanoparticles (MWCNTs-CS-AuNPs/GCE) was developed for the determination of 4,4-diaminodiphenyl diamine (MDA). Cyclic voltammetry (CV) was used to investigate the electrochemical behavior of the sensor in the presence of MDA. MDA displayed a well-expressed oxidation peak at 0.54 V (versus Ag/AgCl) in Britton-Robinson (B-R) universal buffer solution (pH = 10). The transfer coefficient, , and the overall number of electrons (n) involved in the catalytic oxidation of MDA at the MWCNTs-CS-AuNPs/GCE surface were also determined by CV. The reactivity of spiked MDA was strongly dependent on the pH of the supporting electrolyte, with the pH dependence of the MDA oxidation quantified as 27.576 mV pH(-1). Through chronoamperometry, the diffusion coefficient (D) of MDA was calculated to be 9.49 x 10(-5) cm(2) s(-1). The limit of detection of MDA was estimated to be approximate to 20 nM through amperometry experiments, while three linear ranges were found for MDA, i.e., 0.49-10.14 M, 10.14-94.9 M, and 94.9-261.18 M. Real sample tests enabled us to emphasize the potential of this nanocomposite-modified electrode as a new analytical tool for the determination of MDA.
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| 9. |
- Introzzi, Laura, et al.
(författare)
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Ultrasound-Assisted Pullulan/Montmorillonite Bionanocomposite Coating with High Oxygen Barrier Properties
- 2012
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 28:30, s. 11206-11214
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, the preparation and characterization of oxygen barrier pullulan sodium montmorillonite (Na+-MMT) nanocomposite coatings are presented for the first time. Full exfoliation of platelets during preparation of the coating water dispersions was mediated by ultrasonic treatment, which turned out to be a pivotal factor in the oxygen barrier performance of the final material even at high relative humidity (RH) conditions [oxygen permeability coefficients similar to 1.43 +/- 0.39 and 258.05 +/- 13.78 mL.mu m.m(-2).(24 h)(-1).atm(-1) at 23 degrees C and 0% RH and 70% RH, respectively]. At the micro- and nanoscale, the reasons are discussed. The final morphology of the coatings revealed that clay lamellae were stacked on top of one another, probably due to the forced confinement of the platelets within the coating thickness after solvent evaporation. This was also confirmed by modeling the experimental oxygen permeability data with the well-known Nielsen and Cussler permeation theoretical models, which suggested a reasonable aspect ratio (alpha) of similar to 100. Electron microscopic analyses also disclosed a peculiar cell-like arrangement of the platelets. The stacking of the clay lamellae and the cell-like arrangement create the excellent oxygen barrier properties. Finally, we demonstrated that the slight haze increase in the bionanocomposite coating materials arising from the addition of the clays depends on the clay concentration but not so much on the sonication time, due to the balance of opposite effects after sonication (an increase in the number of scattering centers but a reduction in their size).
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| 10. |
- Liu, Dongming, et al.
(författare)
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Cellulose nanofibril core-shell silica coatings and their conversion into thermally stable nanotube aerogels
- 2015
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry. - 2050-7488 .- 2050-7496. ; 3:30, s. 15745-15754
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Tidskriftsartikel (refereegranskat)abstract
- A facile water-based one-pot reaction protocol for obtaining 20 nm thick uniform silica coatings on cellulose nanofibrils (CNFs) is herein presented for the first time. The fully covering silica shells result in the thermal stability of the CNFs improved by ca. 70 degrees C and 50 degrees C under nitrogen and oxygen atmospheres, respectively. Heating of the core-shell hybrid fibres to 400 degrees C results in complete degradation/removal of the CNF cores, and demonstrates an inexpensive route to large-scale preparation of silica nanotubes with the CNFs used as templates. The key to a uniform condensation of silica (from tetraethyl orthosilicate) to cellulose is a reaction medium that permits in situ nucleation and growth of the silica phase on the fibrils, while simultaneously matching the quantity of the condensed silica with the specific surface area of the CNFs. Most coatings were applied to bundles of 2-3 associated CNFs, which could be discerned from their negative imprint that remained inside the silica nanotubes. Finally, it is demonstrated that the coated nanofibrils can be freeze-dried into highly porous silica/cellulose aerogels with a density of 0.005 g cm(-3) and how these hybrid aerogels preserve their shape when extensively exposed to 400 degrees C in air (>6 h). The resulting material is the first reported silica nanotube aerogel obtained by using cellulose nanofibrils as templates.
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| 11. |
- Rovera, Cesare, et al.
(författare)
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Enzymatic Hydrolysis in the Green Production of Bacterial Cellulose Nanocrystals
- 2018
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Ingår i: ACS Sustainable Chemistry and Engineering. - : AMER CHEMICAL SOC. - 2168-0485. ; 6:6, s. 7725-7734
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Tidskriftsartikel (refereegranskat)abstract
- In this study, we extensively describe experimental models, with correlating experimental conditions, which were used to investigate the enzymatic hydrolysis of bacterial cellulose (BC) to obtain nanocrystals. Cellulase from Trichoderma reesei was used in five enzyme/BC ratios over a period of 74 h. The turbidity data was modeled using both logistic regression and empirical regression to determine the fractal kinetics, resulting in unique kinetic patterns for the mixtures that were richest in BC and in enzymes. The evolution of the yield was inversely related to the turbidity, as confirmed through a semiempirical approach that was adopted to model the experimental data. The yield values after 74 h of hydrolysis were higher for the substrate-rich mixtures (similar to 20%) than for the enzyme rich mixtures (similar to 5%), as corroborated by cellobiose and glucose quantification. Transmission electron microscopy and atomic force microscopy analyses revealed a shift from a fibril network to a needle-like morphology (i.e., aggregated nanocrystals or individual nanocrystals similar to 6 nm width and 200-800 nm in length) as the enzyme/BC ratios went from lower to higher. These results were explained in terms of the heterogeneous substrate model and the erosion model. This work initiated a promising, environmentally friendly method that could serve as an alternative to the commonly used chemical hydrolysis routes.
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| 12. |
- Rovera, Cesare, et al.
(författare)
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Water vapor barrier properties of wheat gluten/silica hybrid coatings on paperboard for food packaging applications
- 2020
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Ingår i: Food Packaging and Shelf Life. - : Elsevier Ltd. - 2214-2894. ; 26
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Tidskriftsartikel (refereegranskat)abstract
- Motivated by the increasing need for new solutions with less environmental impact, in this work we have investigated the benefits of depositing a wheat gluten (WG) coating on paperboard substrates intended for food packaging applications. To overcome the inherent moisture sensitivity of this protein, WG was combined with a silica network obtained by sol-gel chemistry. WG/silica hybrid coatings were characterized in terms of structural, thermal, morphological, surface, and water vapor barrier properties. Spectrometric analysis demonstrated that the organic and inorganic phases interacted primarily through hydrogen bonding. This was also supported by thermal experiments, which revealed a higher Tg measured for the hybrid materials with the higher silica content (114 ± 1 °C and 128 ± 2 °C, respectively) compared to the pure WG material (Tg = 89 ± 1 °C). Scanning electron microscopy showed that the surfaces of the coatings were very smooth, though the presence of pinholes, cracks, fractures, and voids was detected, especially for the silica-rich formulations. Upon deposition of the coatings, the wettability of the bare paperboard increased, as demonstrated by the lower water contact angle values. In addition, hybrid coatings exhibited a higher wettability over the pristine WG coating, which was due to a more intense spreading phenomenon. The deposition of the coatings led to a ∼ 4-fold reduction in water vapor transmission rate (WVTR ∼ 90 g m-2 24 h-1 at 23 °C and 65% relative humidity) of the specific cellulosic substrate tested in this work (WVTR ∼ 350 g m-2 24-1).
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| 13. |
- Ture, Hasan, et al.
(författare)
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Nanostructured Silica Wheat Gluten Hybrid Materials Prepared by Catalytic Sol-Gel Chemistry
- 2013
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Ingår i: Macromolecular Chemistry and Physics. - : Wiley. - 1022-1352 .- 1521-3935. ; 214:10, s. 1131-1139
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Tidskriftsartikel (refereegranskat)abstract
- The main physicochemical properties of nanostructured silica/wheat gluten hybrid composites are presented. The extraction experiments suggest that the protein phase is intimately encased within the silica matrix, with silica–protein interactions driven by hydrogen bonding, as indicated by IR spectra. Spectroscopic results also show that silica induces a higher degree of constraint of the wheat gluten matrix, despite less aggregation. Moisture diffusion properties of the hybrid materials are investigated by a combined “desorption/sorption” approach. While the reduction of the moisture diffusivity in the presence of silica can be described by the geometrical impedance of a “sintered” porous solid, a time-dependent relaxation/restructuring of the composite apparently occurs during the sorption-desorption cycle.
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| 14. |
- Unalan, Ilke Uysal, et al.
(författare)
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Exceptional oxygen barrier performance of pullulan nanocomposites with ultra-low loading of graphene oxide
- 2015
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Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 26:27
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Tidskriftsartikel (refereegranskat)abstract
- Polymer nanocomposites are increasingly important in food packaging sectors. Biopolymer pullulan is promising in manufacturing packaging films or coatings due to its excellent optical clarity, mechanical strength, and high water-solubility as compared to other biopolymers. This work aims to enhance its oxygen barrier properties and overcome its intrinsic brittleness by utilizing two-dimensional planar graphene oxide (GO) nanoplatelets. It has been found that the addition of only 0.2 wt% of GO enhanced the tensile strength, Young's modulus, and elongation at break of pullulan films by about 40, 44 and 52%, respectively. The light transmittance at 550 nm of the pullulan/GO films was 92.3% and haze values were within 3.0% threshold, which meets the general requirement for food packaging materials. In particular, the oxygen permeability coefficient of pullulan was reduced from 6337 to 2614 mL mu mm(-2) (24 h(-1)) atm(-1) with as low as 0.05 wt% of GO loading and further to 1357 mL mu mm(-2) (24 h(-1)) atm(-1) when GO concentration reached 0.3 wt%. The simultaneous improvement of the mechanical and oxygen barrier properties of pullulan was ascribed to the homogeneous distribution and prevalent unidirectional alignment of GO nanosheets, as determined from the characterization and theoretical modelling results. The exceptional oxygen barrier properties of pullulan/ GO nanocomposites with enhanced mechanical flexibility and good optical clarity will add new values to high performance food packaging materials.
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