| 1. |
- Cautela, Jacopo, et al.
(författare)
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Supracolloidal Atomium
- 2020
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Ingår i: ACS Nano. - : American Chemical Society (ACS). - 1936-086X .- 1936-0851. ; 14:11, s. 15748-15756
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Tidskriftsartikel (refereegranskat)abstract
- Nature suggests that complex materials result from a hierarchical organization of matter at different length scales. At the nano- and micrometer scale, macromolecules and supramolecular aggregates spontaneously assemble into supracolloidal structures whose complexity is given by the coexistence of various colloidal entities and the specific interactions between them. Here, we demonstrate how such control can be implemented by engineering specially customized bile salt derivative-based supramolecular tubules that exhibit a highly specific interaction with polymeric microgel spheres at their extremities thanks to their scroll-like structure. This design allows for hierarchical supracolloidal self-assembly of microgels and supramolecular scrolls into a regular framework of “nodes” and “linkers”. The supramolecular assembly into scrolls can be triggered by pH and temperature, thereby providing the whole supracolloidal system with interesting stimuli-responsive properties. A colloidal smart assembly is embodied with features of center-linker frameworks as those found in molecular metal–organic frameworks and in structures engineered at human scale, masterfully represented by the Atomium in Bruxelles.
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| 2. |
- Du, Guanqun, et al.
(författare)
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Condensed Supramolecular Helices : The Twisted Sisters of DNA
- 2022
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Ingår i: Angewandte Chemie (International edition). - : Wiley. - 1521-3773. ; 61:4
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Tidskriftsartikel (refereegranskat)abstract
- Condensation of DNA helices into hexagonally packed bundles and toroids represents an intriguing example of functional organization of biological macromolecules at the nanoscale. The condensation models are based on the unique polyelectrolyte features of DNA, however here we could reproduce a DNA-like condensation with supramolecular helices of small chiral molecules, thereby demonstrating that it is a more general phenomenon. We show that the bile salt sodium deoxycholate can form supramolecular helices upon interaction with oppositely charged polyelectrolytes of homopolymer or block copolymers. At higher order, a controlled hexagonal packing of the helices into DNA-like bundles and toroids could be accomplished. The results disclose unknown similarities between covalent and supramolecular non-covalent helical polyelectrolytes, which inspire visionary ideas of constructing supramolecular versions of biological macromolecules. As drug nanocarriers the polymer-bile salt superstructures would get advantage of a complex chirality at molecular and supramolecular levels, whose effect on the nanocarrier assisted drug efficiency is a still unexplored fascinating issue.
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| 3. |
- Gavagnin, Marco, et al.
(författare)
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Magnetic force microscopy study of shape engineered FEBID iron nanostructures
- 2014
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Ingår i: Physica Status Solidi (a) applications and materials science. - : Wiley. - 1862-6300 .- 1862-6319. ; 211:2, s. 368-374
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Tidskriftsartikel (refereegranskat)abstract
- The capability to control matter down to the nanoscale level in combination with the novel magnetic properties of nanomaterials have attracted increasing attention in the last few decades due to their applications in magnetic sensing, hard disc data storage and logic devices. Therefore, many efforts have been devoted to the implementation of both nanofabrication methods as well as characterization of magnetic nanoelements. In this study, Fe-based nanostructures have been synthesized on Si(100) by focused electron beam induced deposition (FEBID) utilizing iron pentacarbonyl as precursor. The so obtained nanostructures exhibit a remarkably high iron content (Fe>80at.%), expected to give rise to a ferromagnetic behaviour. For that reason, magnetic force microscopy (MFM) analyses were performed on the obtained FEBID Fe nanostructures. Moreover, object oriented micromagnetic framework (OOMMF) magnetic simulations have been executed to study the influence of the geometry on the magnetic properties of iron single-domain nanowires. FEBID is a mask-less nanofabrication method based on the injection of precursor gas molecules in proximity of the deposition area where their decomposition is locally induced by a focused electron beam.
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| 4. |
- Jansson, Maria, et al.
(författare)
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Nanoplatelet interactions in the presence of multivalent ions : The effect of overcharging and stability
- 2020
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Ingår i: Journal of Colloid and Interface Science. - : Elsevier BV. - 0021-9797. ; 579, s. 573-581
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Tidskriftsartikel (refereegranskat)abstract
- Hypothesis: The stability of colloidal dispersions in the presence of multivalent ions depends strongly on the electrostatic interactions between the suspended particles. Of particular interest are colloidal particles having dimensions in the nanometric range and with an anisotropic shape due to its high surface area per unit mass, for example clay, which has the key characteristic of a negatively charged surface, surrounded by an oppositely charged rim. Experiments: In this study, we investigate the interactions in nanoplatelet dispersions for the model system of Laponite® clay with addition of mono- and multivalent salt. Molecular dynamics simulations with enhanced umbrella sampling have been utilised in combination with the experimental techniques of zeta-potential measurements, dynamic light scattering, and transmission electron microscopy. Findings: It was observed that tactoid formation and tactoidal dissolution due to overcharging occur upon the addition of trivalent salt. The overcharging effect was captured from calculated potential of mean force and confirmed from the zeta-potential, which changed sign from negative to positive when increasing the stoichiometric charge-ratio between the positive salt ions and the clay. Consequently, the gained information could provide useful physical insight of nanoplatelet interactions in the presence of multivalent ions.
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| 5. |
- Jephthah, Stéphanie, et al.
(författare)
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Physicochemical characterisation of KEIF€-the intrinsically disordered N-terminal region of magnesium transporter A
- 2020
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Ingår i: Biomolecules. - : MDPI AG. - 2218-273X. ; 10:4
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Tidskriftsartikel (refereegranskat)abstract
- Magnesium transporter A (MgtA) is an active transporter responsible for importing magnesium ions into the cytoplasm of prokaryotic cells. This study focuses on the peptide corresponding to the intrinsically disordered N-terminal region of MgtA, referred to as KEIF. Primary-structure and bioinformatic analyses were performed, followed by studies of the undisturbed single chain using a combination of techniques including small-angle X-ray scattering, circular dichroism spectroscopy, and atomistic molecular-dynamics simulations. Moreover, interactions with large unilamellar vesicles were investigated by using dynamic light scattering, laser Doppler velocimetry, cryogenic transmission electron microscopy, and circular dichroism spectroscopy. KEIF was confirmed to be intrinsically disordered in aqueous solution, although extended and containing little β-structure and possibly PPII structure. An increase of helical content was observed in organic solvent, and a similar effect was also seen in aqueous solution containing anionic vesicles. Interactions of cationic KEIF with anionic vesicles led to the hypothesis that KEIF adsorbs to the vesicle surface through electrostatic and entropic driving forces. Considering this, there is a possibility that the biological role of KEIF is to anchor MgtA in the cell membrane, although further investigation is needed to confirm this hypothesis.
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| 6. |
- Kowalczyk, Dorota A., et al.
(författare)
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Local electronic structure of stable monolayers of α-MoO3−x grown on graphite substrate
- 2021
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Ingår i: 2D Materials. - : IOP Publishing. - 2053-1583. ; 8:2
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Tidskriftsartikel (refereegranskat)abstract
- We report on van der Waals epitaxy of two-dimensional (2D) molybdenum trioxide (MoO3−x) with monolayer thickness directly grown on highly oriented pyrolytic graphite by thermal evaporation under ultrahigh vacuum. The chemical composition, electronic and crystalline lattice structures of the mono-and few-layer MoO3−x sheets are analysed. Using scanning tunnelling microscopy and spectroscopy, we investigate the electronic properties of MoO3−x as a function of the number of layers and measure the apparent energy gap to be 0.4 eV for the first three layers of MoO3−x on graphite. We carried out density functional theory calculations to shed light on the mechanism underlying the observed narrow bandgap with oxygen deficiency. Moreover, the air exposure effect on monolayer MoO3−x is investigated confirming that the apparent bandgap closes, and additionally we show the reduction of the work function from 5.7 to 4.7 eV. We prove that it is possible to synthesize the 2D, non-stoichiometric, and electrically conductive MoO3−x.
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| 7. |
- Kowalczyk, Dorota A., et al.
(författare)
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Two-Dimensional Crystals as a Buffer Layer for High Work Function Applications : The Case of Monolayer MoO3
- 2022
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Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 14:39, s. 44506-44515
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Tidskriftsartikel (refereegranskat)abstract
- We propose that the crystallinity of two-dimensional (2D) materials is a crucial factor for achieving highly effective work function (WF) modification. A crystalline 2D MoO3 monolayer enhances substrate WF up to 6.4 eV for thicknesses as low as 0.7 nm. Such a high WF makes 2D MoO3 a great candidate for tuning properties of anode materials and for the future design of organic electronic devices, where accurate evaluation of the WF is crucial. We provide a detailed investigation of WF of 2D α-MoO3 directly grown on highly ordered pyrolytic graphite, by means of Kelvin probe force microscopy (KPFM) and ultraviolet photoemission spectroscopy (UPS). This study underlines the importance of a controlled environment and the resulting crystallinity to achieve high WF in MoO3. UPS is proved to be suitable for determining higher WF attributed to 2D islands on a substrate with lower WF, yet only in particular cases of sufficient coverage. KPFM remains a method of choice for nanoscale investigations, especially when conducted under ultrahigh vacuum conditions. Our experimental results are supported by density functional theory calculations of electrostatic potential, which indicate that oxygen vacancies result in anisotropy of WF at the sides of the MoO3 monolayer. These novel insights into the electronic properties of 2D-MoO3 are promising for the design of electronic devices with high WF monolayer films, preserving the transparency and flexibility of the systems.
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| 8. |
- Santilli, Andrea, et al.
(författare)
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Bioderived, chiral and stable 1-dimensional light-responsive nanostructures : Interconversion between tubules and twisted ribbons
- 2022
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Ingår i: Journal of Colloid and Interface Science. - : Elsevier BV. - 0021-9797. ; 623, s. 723-734
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Tidskriftsartikel (refereegranskat)abstract
- HYPOTHESIS: Self-assembling molecular structures responding to light stimulus are appealing for applications as sensing and drug delivery. Supramolecular nanotubes have a relevant potential in nanotechnology as they can be used to encapsulate different loads like drugs, biological macromolecules, and nanomaterials. In addition, they are suitable elements for novel supracolloidal materials. Structural responses of supramolecular nanotubes to non-invasive stimuli are very much desired to enable controlled release of the encapsulated guests and to provide these recently developed new materials with an external trigger. Here, we describe the formation of well-defined, single wall tubules that interconvert into twisted ribbons upon UV-light exposure in aqueous environment. The structures are provided by self-assembly of an azobenzene substituted cholic acid, a biological surfactant belonging to the family of bile acids. The azobenzene group allows for the light responsiveness of the molecular packing. Concurrently the steroidal moieties assure both chiral features and extensive hydrophobic interactions for time and temperature resistant aggregates.EXPERIMENTS: The molecular packing interconversion was followed by circular dichroism. Microscopy, small angle X-ray scattering and light scattering measurements demonstrated the drastic morphological variation upon irradiation. A model of the molecular arrangement within the tubular walls was suggested based on the circular dichroism spectra simulation.FINDINGS: Innovatively, the molecular design reported in our work allows for encoding in the same light responsive system multiple desirable features (e.g. bio-origin, temperature resistance and chirality of the aggregates). Such combination of properties, never reported before for a single molecule, might be relevant for the realization of robust, stimuli-responsive bio-vectors.
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