| 1. |
- Abbondanza, Giuseppe, 1991, et al.
(author)
-
Au-Pd Barcode Nanowires with Tailored Lattice Parameters and Segment Lengths for Catalytic Applications
- 2024
-
In: ACS Applied Nano Materials. - 2574-0970. ; 7:4, s. 3861-3874
-
Journal article (peer-reviewed)abstract
- In this study, we present a systematic investigation of the controlled fabrication of Au-Pd barcode nanowires within nanoporous anodic aluminum oxide (NP-AAO) templates. By using a combination of in situ X-ray diffraction (XRD), focused ion beam scanning electron microscopy (FIB-SEM), and transmission electron microscopy (TEM), we elucidate the influence of template preparation methods on the resulting nanowire properties. The template treatment, involving either pore widening or barrier layer thinning, significantly impacts nanowire growth. Through the analysis of the XRD data, we observe sequential deposition of Au and Pd segments with lattice parameter variations and strain effects. Particularly, the lattice parameters of Au and Pd segments display intricate temporal dependencies, influenced by interfacial effects and strain caused by growth under confinement. FIB-SEM imaging reveals uniform and reproducible nanowire lengths in the template treated with pore widening. Furthermore, TEM analysis confirms the presence of distinct Au and Pd segments, while scanning TEM-energy-dispersive X-ray spectroscopy revealed minor evidence of interdiffusion between the first and the second electrodeposited segments. Our findings emphasize the potential of the electrodeposition process within nanoporous templates for producing barcode nanowires with precise segmental properties. The combination of in situ XRD and electron microscopy offers valuable insights into the growth dynamics and structural characteristics of the fabricated Au-Pd barcode nanowires. This controlled fabrication strategy opens doors to tailoring nanowire properties for diverse applications, particularly in catalysis.
|
|
| 2. |
- Abbondanza, Giuseppe, et al.
(author)
-
Templated electrodeposition as a scalable and surfactant-free approach to the synthesis of Au nanoparticles with tunable aspect ratios
- 2022
-
In: Nanoscale Advances. - : Royal Society of Chemistry. - 2516-0230. ; 4:11, s. 2452-2467
-
Journal article (peer-reviewed)abstract
- A high-throughput method for the fabrication of ordered arrays of Au nanoparticles is presented. It is based on pulsed electrodeposition into porous anodic alumina templates. In contrast to many synthesis routes, it is cyanide-free, prior separation of the alumina template from the aluminium substrate is not required, and the use of contaminating surfactants/capping agents often found in colloidal synthesis is avoided. The aspect ratio of the nanoparticles can also be tuned by selecting an appropriate electrodeposition time. We show how to fabricate arrays of nanoparticles, both with branched bases and with hemispherical bases. Furthermore, we compare the different morphologies produced with electron microscopies and grazing-incidence synchrotron X-ray diffraction. We find the nanoparticles are polycrystalline in nature and are compressively strained perpendicular to the direction of growth, and expansively strained along the direction of growth. We discuss how this can produce dislocations and twinning defects that could be beneficial for catalysis.
|
|
| 3. |
- Bermeo, Marie, et al.
(author)
-
Branched-gallium phosphide nanowires seeded by palladium nanoparticles
- 2023
-
In: Nanotechnology. - 0957-4484. ; 34:39
-
Journal article (peer-reviewed)abstract
- Palladium nanoparticles were produced by a chemical reagent-free and versatile method called spark ablation with control over particle size and density. These nanoparticles were used as catalytic seed particles for gallium phosphide nanowire growth by metalorganic vapour-phase epitaxy. Controlled growth of GaP nanowires using significantly small Pd nanoparticles between 10 and 40 nm diameter was achieved by varying several growth parameters. Low V/III ratios below 2.0 promote higher Ga incorporation into the Pd nanoparticles. Moderate growth temperatures under 600 °C avoid kinking and undesirable GaP surface growth. In addition, a second batch of palladium nanoparticles of concentration up to 1000 particles μm−2 was deposited onto the GaP nanowires. Subsequently, three-dimensional nanostructures evolved, with branches growing along the surface of the GaP nanowires. The GaP nanowires revealed a zinc blende structure with multiple twinning and a PdGa phase at the tip of the nanowires and branches.
|
|
| 4. |
- Dubackic, Marija, et al.
(author)
-
α-Synuclein Interaction with Lipid Bilayer Discs
- 2022
-
In: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 38:33, s. 10216-10224
-
Journal article (peer-reviewed)abstract
- α-Synuclein (aSyn) is a 140 residue long protein present in presynaptic termini of nerve cells. The protein is associated with Parkinson's disease, in which case it has been found to self-Assemble into long amyloid fibrils forming intracellular inclusions that are also rich in lipids. Furthermore, its synaptic function is proposed to involve interaction with lipid membranes, and hence, it is of interest to understand aSyn-lipid membrane interactions in detail. In this paper we report on the interaction of aSyn with model membranes in the form of lipid bilayer discs. Using a combination of cryogenic transmission electron microscopy and small-Angle neutron scattering, we show that circular discs undergo a significant shape transition after the adsorption of aSyn. When aSyn self-Assembles into fibrils, aSyn molecules desorb from the bilayer discs, allowing them to recover to their original shape. Interestingly, the desorption process has an all-or-none character, resulting in a binary coexistence of circular bilayer discs with no adsorbed aSyn and deformed bilayer discs having a maximum amount of adsorbed protein. The observed coexistence is consistent with the recent finding of cooperative aSyn adsorption to anionic lipid bilayers.
|
|
| 5. |
- Ek, Martin, et al.
(author)
-
Electron Image Series Reconstruction of Twin Interfaces in InP Superlattice Nanowires.
- 2011
-
In: Microscopy and Microanalysis. - 1435-8115. ; 17:5, s. 752-758
-
Journal article (peer-reviewed)abstract
- The twin interface structure in twinning superlattice InP nanowires with zincblende structure has been investigated using electron exit wavefunction restoration from focal series images recorded on an aberration-corrected transmission electron microscope. By comparing the exit wavefunction phase with simulations from model structures, it was possible to determine the twin structure to be the ortho type with preserved In-P bonding order across the interface. The bending of the thin nanowires away from the intended ⟨110⟩ axis could be estimated locally from the calculated diffraction pattern, and this parameter was successfully taken into account in the simulations.
|
|
| 6. |
- Larsson, Alfred, et al.
(author)
-
Electrochemical Fabrication and Characterization of Palladium Nanowires in Nanoporous Alumina Templates
- 2020
-
In: Journal of the Electrochemical Society. - : The Electrochemical Society. - 0013-4651 .- 1945-7111. ; 167:12
-
Journal article (peer-reviewed)abstract
- A method for the electrochemical synthesis of palladium nanowires, using porous alumina templates with diameters of 25 nm and 40 nm, is presented. Through an electrochemical barrier layer thinning step, pulsed electrodeposition can take place directly into the anodized aluminum; without need for extra removal, pore opening, and metal contact coating steps. A digital oscilloscope is used to record and integrate the current, allowing the efficiency of the electrodeposition to be calculated. We discuss how using a large 'off period' allows for the replenishment of the depleted diffusion layer. The nanowires are characterized by using a focused ion beam (FIB) to create cross-sections which can be accessed with a scanning electron microscope (SEM). With grazing-incidence X-ray diffraction (GI-XRD) we find that the nanowires have a slight compressive strain in the direction that they are confined by the pores (0.58 % and 0.51 % for the 25 nm and 40 nm pores respectively). Knowing the strain state of the nanowires inside the template is of importance for the use of templated nanowires in devices. Further characterization is made using high-resolution transmission electron microscopy (HR-TEM) and energy dispersive X-ray spectroscopy (EDS), after removal from the alumina templates.
|
|
| 7. |
- Larsson, Matilda, et al.
(author)
-
Effect of hydrophobically modified graphene oxide on the properties of poly(3-hydroxybutyrate-co-4-hydroxybutyrate)
- 2017
-
In: Polymer. - : Elsevier BV. - 0032-3861. ; 108, s. 66-77
-
Journal article (peer-reviewed)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.
|
|
| 8. |
- Menon, Heera, et al.
(author)
-
Fabrication of Single-Crystalline InSb-on-Insulator by Rapid Melt Growth
- 2022
-
In: Physica Status Solidi (A) Applications and Materials Science. - : Wiley. - 1862-6300. ; 219:4
-
Journal article (peer-reviewed)abstract
- InSb has the smallest bandgap and highest electron mobility among III-V semiconductors and is widely used for photodetectors and high-frequency electronic applications. Integration of InSb directly on Si would drastically reduce the fabrication cost and enable new applications, however, it is very challenging due to its 19% lattice mismatch with Si. Herein, the integration of single-crystalline InSb microstructures on insulator-covered Si through rapid melt growth (RMG) is reported and specifically provides details on the fabrication process. The importance of achieving high-quality conformal capping layers at low thermal budget to contain the InSb melt is assessed when the sample is annealed. The importance of ensuring a pristine Si seed area to achieve single-crystalline InSb is illustrated and demonstrated here for the first time.
|
|
| 9. |
- Mikkelä, Mikko-Heikki, et al.
(author)
-
Bismuth-oxide nanoparticles: study in a beam and as deposited
- 2024
-
In: Physical chemistry chemical physics : PCCP. - 1463-9084. ; 26:13, s. 10369-10381
-
Journal article (peer-reviewed)abstract
- Bi2O3 is a promising material for solid-oxide fuel cells (SOFC) due to the high ionic conductivity of some phases. The largest value is reached for its δ-phase, but it is normally stable at temperatures too high for SOFC operation, while nanostructured oxide is believed to have more suitable stabilization temperature. However, to manufacture such a material with a controlled chemical composition is a challenging task. In this work, we investigated the fabrication of nanostructured Bi2O3 films formed by deposition of free Bi-oxide nanoparticles created in situ. The particle-production method was based on reactive sputtering and vapour aggregation. Depending on the fabrication conditions, the nanoparticles contained either a combination of Bi–metal and Bi-oxide, or only Bi-oxide. Prior to deposition, the free particles were probed in the beam – by synchrotron-based photoelectron spectroscopy (PES), which allowed assessing their composition “on the-fly”. The nanoparticle films obtained after deposition were studied by PES, scanning electron microscopy, transmission electron microscopy, and electron diffraction. The films' chemical composition, grain dimensions, and crystal structure were probed. Our analysis suggests that our method produced Bi-oxide films in more than one polymorph of Bi2O3.
|
|
| 10. |
- Noshad, Asma, et al.
(author)
-
Antibacterial Effect of Silver Nanoparticles (AgNPs) Synthesized from Trichoderma Harzianum Against Clavibacter Michiganensis
- 2019
-
In: Journal of Nano Research. - 1662-5250 .- 1661-9897. ; 58, s. 10-19
-
Journal article (peer-reviewed)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.
|
|
