| 1. |
- Larsson, Matilda, et al.
(författare)
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Effect of hydrophobically modified graphene oxide on the properties of poly(3-hydroxybutyrate-co-4-hydroxybutyrate)
- 2017
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Ingår i: Polymer. - : Elsevier BV. - 0032-3861. ; 108, s. 66-77
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Tidskriftsartikel (refereegranskat)abstract
- Nanocomposites of poly(3-hydroxybutyrate-co-4-hydroxybutyrate) [P(3,4HB)] and hydrophobically modified graphene oxide (GO) were prepared via melt blending and characterised with respect to processability, polymer degradation, as well as thermal, rheological and mechanical properties. GO prepared via the modified Hummer’s method was alkylated by reactions with butyl-, octyl- and hexadecylamine, respectively. The successful functionalisation was verified by IR spectroscopy, X-ray diffraction measurements, transmission electron microscopy and elemental analysis. The thermal decomposition temperature of the alkylated GOs increased with increasing alkyl chain length. Moreover, the alkylated GOs showed a much improved compatibility with P(3,4HB) in the melt compared to the unmodified GO, and microscopy showed an even distribution in the polymer matrix. The molecular weight of P(3,4HB) was found to decrease during the melt extrusion, and the chain degradation was found to increase after the addition of alkylated GO. However, this effect decreased with increasing alkyl chain length. Melt rheology measurements showed that percolating networks appeared at filler contents above ~2 wt%. These networks were detected as increases in shear storage modulus and decreased phase shifts towards more elastic materials over time and at low frequencies. During cooling of the melts, calorimetric measurements showed an increase in the crystallisation temperature and enthalpy with increasing filler contents up to ~2 wt%. However, at higher filler contents a decreased propensity for crystallisation was noted, which again indicated network formation. Tensile testing showed that the nanocomposites containing the GO with hexadecyl chains displayed the highest elongation at break and yield stress. However, the numbers were lower compared to the unfilled P(3,4HB), most probably because of the lower molecular weight of the P(3,4HB) in the nanocomposites. The results of the present study demonstrated that alkylation of GO greatly improves the compatibility with the polymer, and that the processability and thermo-mechanical properties of the nanocomposites are systematically influenced by the GO content and the alkyl chain length.
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| 2. |
- Noshad, Asma, et al.
(författare)
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Antibacterial Effect of Silver Nanoparticles (AgNPs) Synthesized from Trichoderma Harzianum Against Clavibacter Michiganensis
- 2019
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Ingår i: Journal of Nano Research. - 1662-5250 .- 1661-9897. ; 58, s. 10-19
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Tidskriftsartikel (refereegranskat)abstract
- In nanotechnology, fungal mediated green synthesis of silver nanoparticles (AgNPs) has tremendous application in the development of antimicrobial systems but the mechanism behind the synthesis is yet to be understood. This study aims to synthesize the silver nanoparticles via a green chemistry route using mycellial aqueous extract of agriculturally beneficial fungi Trichoderma harzianum. Two different concentrations (1 mM and 2.5 Mm) of aqueous silver salt (AgNO3) were used and mixed as 1:1 ratio with aqueous extract of T. harzianum at room temperature and the pH of the reaction mixture was monitored until it stabilized. Formation of AgNPs was confirmed by using UV-Vis spectroscopic analysis. For further insight, AgNPs were characterized by using HR-TEM and XRD, which clearly showed appearance of crystalline, monodispersed round-shaped particles of 3-20 nm in size. The synthesised NPs were subjected to antimicrobial assay against gram +ve and gram –ve bacteria using the disk diffusion method. The focused species was Clavibacter michiganensis subsp michiganensis, which is the causitive pathogen of Tomato canker disease and we hypothesised that the synthesised AgNPs might be useful to control this pathogen. Appreciable antibiotic activity was monitored even at a low concentration of 1mM level, while the zone of inhibition was positively increased at 2.5 mM. Our results clearly indicate that the present process is an excellent candidate for industrial scale production of AgNPs, and has the potential to control the bacterial pathogen cmm.
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| 3. |
- Noshad, Asma, et al.
(författare)
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Impact of AgNPs on seed germination and seedling growth : A focus study on its antibacterial potential against clavibacter michiganensis subsp. Michiganensis infection in solanum lycopersicum
- 2019
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Ingår i: Journal of Nanomaterials. - : Hindawi Limited. - 1687-4110 .- 1687-4129. ; 2019
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Tidskriftsartikel (refereegranskat)abstract
- This study investigated the effect of biogenic AgNPs on seed germination and seedling growth of Solanum lycopersicum. Treatment with silver nanoparticles (AgNPs) showed a significantly high germination rate and seedling growth compared to untreated seeds. Furthermore, its bactericidal effect against bacterial pathogen Clavibacter michiganensis subsp. michiganensis (cmm) infection in Solanum lycopersicum was also determined. Bacterial canker of tomato (BCT) caused by cmm results in reduced plant growth and production leading to considerable economic losses. Herein, fungal extracts of T. harzianum and A. fumigatus were used separately as a reducing agent to synthesize AgNPs of varying concentrations (0.088 mg/L, 0.176 mg/L, and 0.44 mg/L). Results suggested that the biosynthesized AgNPs not only worked as bactericide but also completely inhibited the incidence of cmm infection even at the lowest concentration of 0.088 mg/L under greenhouse conditions. Plants treated with AgNPs showed significantly enhanced growth parameters including plant height (cm), tomato yield/plant (g), fresh biomass (g), number of shoots/plant, root weight (g), and dry biomass (g). So, in order to reduce the toxic effects of chemical-based bactericides, biobased AgNPs are recommended, not only to control but also to prevent the bacterial infection in agriculture.
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| 4. |
- Ossler, Frederik, et al.
(författare)
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Finger-like carbon-based nanostructures produced by combustion of flour-based sticks (spaghetti)
- 2019
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Ingår i: C: Journal of Carbon Research. - : MDPI AG. - 2311-5629.
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Tidskriftsartikel (refereegranskat)abstract
- Biomass is becoming particularly important as a starting material for advanced carbon structures. In this study, we found interesting nanostructures on the surface of burnt spaghetti using scanning electron microscopy, transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy (EDX) for analysis. The structures were elongated and finger-like, with evidence that the tubes have shell and core components. The shell was carbon that included amorphous and layered graphene structures. EDX showed enriched potassium and phosphorous in the core and at the tip of the tubes. The results indicate that tube formation depends on phase separation of polar/ionic and nonpolar moieties when water is produced in the biomass from the pyrolysis/combustion. The tube growth is most probably due to the raising pressure of vapor that cannot escape through the carbon film that is formed at the surface of the stick from flame heat. This process resembles glass blowing or volcanic activity, where the carbon acts as the glass or earth’s crust, respectively. These observations suggest that new interesting tubular nanostructures with different properties on the inside and outside can be produced in a relatively simple way, utilizing processes of combustion of starch-rich biomass materials.
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