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See detailForce measurements reveal how small binders perturb the dissociation mechanisms of DNA duplex sequences
Burmistrova, Anastasia; Fresch, Barbara ULg; Sluysmans, Damien ULg et al

in Nanoscale (2016), 8

The force-driven separation of double-stranded DNA is crucial to the accomplishment of cellular pro- cesses like genome transactions. Ligands binding to short DNA sequences can have a local stabilizing or ... [more ▼]

The force-driven separation of double-stranded DNA is crucial to the accomplishment of cellular pro- cesses like genome transactions. Ligands binding to short DNA sequences can have a local stabilizing or destabilizing effect and thus severely affect these processes. Although the design of ligands that bind to specific sequences is a field of intense research with promising biomedical applications, so far, their effect on the force-induced strand separation has remained elusive. Here, by means of AFM-based single mole- cule force spectroscopy, we show the co-existence of two different mechanisms for the separation of a short DNA duplex and demonstrate how they are perturbed by small binders. With the support of Mole- cular Dynamics simulations, we evidence that above a critical pulling rate one of the dissociation pathways becomes dominant, with a dramatic effect on the rupture forces. Around the critical threshold, we observe a drop of the most probable rupture forces for ligand-stabilized duplexes. Our results offer a deep understanding of how a stable DNA–ligand complex behaves under force-driven strand separation [less ▲]

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See detailSize- and shape-dependent phase diagram of In–Sb nano-alloys
Ghasemi, Masoomeh; Zanolli, Zeila ULg; Stankovski, Martin et al

in Nanoscale (2015), 7

Nano-scale alloy systems with at least one dimension below 100 nm have different phase stabilities than those observed in the macro-scale systems due to a large surface to volume ratio. We have used the ... [more ▼]

Nano-scale alloy systems with at least one dimension below 100 nm have different phase stabilities than those observed in the macro-scale systems due to a large surface to volume ratio. We have used the semi-empirical thermodynamic modelling, i.e. the CALPHAD method, to predict the phase equilibria of the In–Sb nano-scale systems as a function of size and shape. To calculate the size- and shape-depen- dent phase diagram of the In–Sb system, we have added size-dependent surface energy terms to the Gibbs energy expressions in the In–Sb thermodynamic database. We estimated the surface energies of the solution phases and of the InSb intermetallic phase using the Butler equation and DFT calculations, respectively. A melting point and eutectic point depression were observed for both nanoparticle and nanowire systems. The eutectic composition on the In-rich and Sb-rich sides of the phase diagram shifted towards higher solubility. We believe that the phase diagram of In–Sb nano-alloys is useful for an increased understanding of the growth parameters and mechanisms of InSb nanostructures. [less ▲]

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See detailUnraveling the complexity of the interactions of DNA nucleotides with gold by single molecule force spectroscopy
Bano, Fouzia; Sluysmans, Damien ULg; Wislez, Arnaud ULg et al

in Nanoscale (2015), 7

Addressing the effect of different environmental factors on the adsorption of DNA to solid supports is critical for the development of robust miniaturized devices for applications ranging from biosensors ... [more ▼]

Addressing the effect of different environmental factors on the adsorption of DNA to solid supports is critical for the development of robust miniaturized devices for applications ranging from biosensors to next generation molecular technology. Most of the time, thiol-based chemistry is used to anchor DNA on gold – a substrate commonly used in nanotechnology – and little is known about the direct interaction between DNA and gold. So far there have been no systematic studies on the direct adsorption behavior of the deoxyribonucleotides (i.e., a nitrogenous base, a deoxyribose sugar, and a phosphate group) and on the factors that govern the DNA–gold bond strength. Here, using single molecule force spectroscopy, we investigated the interaction of the four individual nucleotides, adenine, guanine, cytosine, and thymine, with gold. Experiments were performed in three salinity conditions and two surface dwell times to reveal the factors that influence nucleotide–Au bond strength. Force data show that, at physiological ionic strength, adenine–Au interactions are stronger, asymmetrical and independent of surface dwell time as compared to cytosine–Au and guanine–Au interactions. We suggest that in these conditions only adenine is able to chemisorb on gold. A decrease of the ionic strength significantly increases the bond strength for all nucleotides. We show that moderate ionic strength along with longer surface dwell period suggest weak chemisorption also for cytosine and guanine. [less ▲]

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See detailEmission tunable, cyto/hemocompatible, near-IR-emitting Ag2S quantum dots by aqueous decomposition of DMSA
Hocaoglu, I.; Demir, F.; Birer, O. et al

in Nanoscale (2014), 6

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See detailMetallic nanowire networks: effects of thermal annealing on electrical resistance
Langley, Daniel ULg; Lagrange, Mélanie; Giusti, Gael et al

in Nanoscale (2014), 6

Metallic nanowire networks have huge potential in devices requiring transparent electrodes. This article describes how the electrical resistance of metal nanowire networks evolve under thermal annealing ... [more ▼]

Metallic nanowire networks have huge potential in devices requiring transparent electrodes. This article describes how the electrical resistance of metal nanowire networks evolve under thermal annealing. Understanding the behavior of such films is crucial for the optimization of transparent electrodes which find many applications. An in-depth investigation of silver nanowire networks under different annealing conditions provides a case study demonstrating that several mechanisms, namely local sintering and desorption of organic residues, are responsible for the reduction of the systems electrical resistance. Optimization of the annealing led to specimens with transmittance of 90% (at 550 nm) and sheet resistance of 9.5 Ω sq−1. Quantized steps in resistance were observed and a model is proposed which provides good agreement with the experimental results. In terms of thermal behavior, we demonstrate that there is a maximum thermal budget that these electrodes can tolerate due to spheroidization of the nanowires. This budget is determined by two main factors: the thermal loading and the wire diameter. This result enables the fabrication and optimization of transparent metal nanowire electrodes for solar cells, organic electronics and flexible displays. [less ▲]

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See detailPoly(acrylic acid)-block-poly(vinyl alcohol) anchored maghemite nanoparticles designed for multi-stimuli triggered drug release
Liu, Ji ULg; Detrembleur, Christophe ULg; Debuigne, Antoine ULg et al

in Nanoscale (2013), 5(23), 11464-11477

Original core/corona nanoparticles composed of amaghemite core and a stimuli-responsive polymer coating made of poly(acrylic acid)-block-poly(vinyl alcohol) macromolecules were fabricated for drug ... [more ▼]

Original core/corona nanoparticles composed of amaghemite core and a stimuli-responsive polymer coating made of poly(acrylic acid)-block-poly(vinyl alcohol) macromolecules were fabricated for drug delivery system (DDS) application. This kind of DDS aims to combine the advantage of stimuli-responsive polymer coating, in order to regulate the drug release behaviours under different conditions and furthermore, improve the biocompatibility and in vivo circulation half-time of the maghemite nanoparticles. Drug loading capacity was evaluated with methylene blue (MB), a cationic model drug. The triggered release of MB was studied under various stimuli such as pH, ionic strength and temperature. Local heating generated under alternating magnetic field (AMF) application was studied, and remotely AMF-triggered release was also confirmed, while a mild heating-up of the release medium was observed. Furthermore, their potential application as magnetic resonance imaging (MRI) contrast agents was explored via relaxivity measurements and acquisition of T2-weighted images. Preliminary studies on the cytotoxicity against mouse fibroblast-like L929 cell line and also their cellular uptake within human melanoma MEL-5 cell line were carried out. In conclusion, this kind of stimuli-responsive nanoparticles appears to be promising carriers for delivering drugs to some tumour sites or into cellular compartments with an acidic environment. [less ▲]

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See detail2D to 3D crossover of the magnetic properties in ordered arrays of iron oxide nanocrystals
Faure, Bertrand; Wetterskog, Erik; Gunnarsson, Klas et al

in NANOSCALE (2013), 5(3), 953-960

The magnetic 2D to 3D crossover behavior of well-ordered arrays of monodomain gamma-Fe2O3 spherical nanoparticles with different thicknesses has been investigated by magnetometry and Monte Carlo (MC ... [more ▼]

The magnetic 2D to 3D crossover behavior of well-ordered arrays of monodomain gamma-Fe2O3 spherical nanoparticles with different thicknesses has been investigated by magnetometry and Monte Carlo (MC) simulations. Using the structural information of the arrays obtained from grazing incidence small-angle X-ray scattering and scanning electron microscopy together with the experimentally determined values for the saturation magnetization and magnetic anisotropy of the nanoparticles, we show that MC simulations can reproduce the thickness-dependent magnetic behavior. The magnetic dipolar particle interactions induce a ferromagnetic coupling that increases in strength with decreasing thickness of the array. The 2D to 3D transition in the magnetic properties is mainly driven by a change in the orientation of the magnetic vortex states with increasing thickness, becoming more isotropic as the thickness of the array increases. Magnetic anisotropy prevents long-range ferromagnetic order from being established at low temperature and the nanoparticle magnetic moments instead freeze along directions defined by the distribution of easy magnetization directions. [less ▲]

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See detailStructural diversity in iron oxide nanoparticle assemblies as directed by particle morphology and orientation
Disch, Sabrina; Wetterskog, Erik; Hermann, Raphael ULg et al

in NANOSCALE (2013), 5(9), 3969-3975

The mesostructure of ordered arrays of anisotropic nanoparticles is controlled by a combination of packing constraints and interparticle interactions, two factors that are strongly dependent on the ... [more ▼]

The mesostructure of ordered arrays of anisotropic nanoparticles is controlled by a combination of packing constraints and interparticle interactions, two factors that are strongly dependent on the particle morphology. We have investigated how the degree of truncation of iron oxide nanocubes controls the mesostructure and particle orientation in drop cast mesocrystal arrays. The combination of grazing incidence small-angle X-ray scattering and scanning electron microscopy shows that mesocrystals of highly truncated cubic nanoparticles assemble in an fcc-type mesostructure, similar to arrays formed by iron oxide nanospheres, but with a significantly reduced packing density and displaying two different growth orientations. Strong satellite reflections in the GISAXS pattern indicate a commensurate mesoscopic superstructure that is related to stacking faults in mesocrystals of the anisotropic nanocubes. Our results show how subtle variation in shape anisotropy can induce oriented arrangements of nanoparticles of different structures and also create mesoscopic superstructures of larger periodicity. [less ▲]

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See detailPhonon spectroscopy in a Bi2Te3 nanowire array
Bessas, Dimitrios; Toellner, William; Aabdin, Zainul et al

in NANOSCALE (2013), 5(21), 10629-10635

The lattice dynamics in an array of 56 nm diameter Bi2Te3 nanowires embedded in a self-ordered amorphous alumina membrane were investigated microscopically using Te-125 nuclear inelastic scattering. The ... [more ▼]

The lattice dynamics in an array of 56 nm diameter Bi2Te3 nanowires embedded in a self-ordered amorphous alumina membrane were investigated microscopically using Te-125 nuclear inelastic scattering. The element specific density of phonon states is measured on nanowires in two perpendicular orientations and the speed of sound is extracted. Combined high energy synchrotron radiation diffraction and transmission electron microscopy was carried out on the same sample and the crystallinity was investigated. The nanowires grow almost perpendicular to the c-axis, partly with twinning. The average speed of sound in the 56 nm diameter Bi2Te3 nanowires is similar to 7% smaller with respect to bulk Bi2Te3 and a decrease in the macroscopic lattice thermal conductivity by similar to 13% due to nanostructuration and to the reduced speed of sound is predicted. [less ▲]

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See detailMagnetostructural effects in ligand stabilized Pd13 clusters: a density functional theory study
Fresch, Barbara ULg; Boyen, H.-G.; Remacle, Françoise ULg

in Nanoscale (2012), 4(14), 4138-4147

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