Search results for "Atomic Force"
showing 10 items of 308 documents
Tuning molecular self-assembly on bulk insulator surfaces by anchoring of the organic building blocks.
2013
Molecular self-assembly constitutes a versatile strategy for creating functional structures on surfaces. Tuning the subtle balance between intermolecular and molecule-surface interactions allows structure formation to be tailored at the single-molecule level. While metal surfaces usually exhibit interaction strengths in an energy range that favors molecular self-assembly, dielectric surfaces having low surface energies often lack sufficient interactions with adsorbed molecules. As a consequence, application-relevant, bulk insulating materials pose significant challenges when considering them as supporting substrates for molecular self-assembly. Here, the current status of molecular self-ass…
Impact of local compressive stress on the optical transitions of single organic dye molecules
2012
The ability to mechanically control the optical properties of individual molecules is a grand challenge in nanoscience and could enable the manipulation of chemical reactivity at the single-molecule level. In the past, light has been used to alter the emission wavelength of individual molecules or modulate the energy transfer quantum yield between them. Furthermore, tensile stress has been applied to study the force dependence of protein folding/unfolding and of the chemistry and photochemistry of single molecules, although in these mechanical experiments the strength of the weakest bond limits the amount of applicable force. Here, we show that compressive stress modifies the photophysical …
Mechanical Properties of Pore-Spanning Lipid Bilayers Probed by Atomic Force Microscopy
2006
AbstractWe measure the elastic response of a free-standing lipid membrane to a local indentation by using an atomic force microscope. Starting point is a planar gold-coated alumina substrate with a chemisorbed 3-mercaptopropionic acid monolayer displaying circular pores of very well defined and tunable size, over which bilayers composed of N,N,-dimethyl-N,N,-dioctadecylammonium bromide or 1,2-dioleoyl-3-trimethylammonium-propane chloride were spread. Centrally indenting these “nanodrums” with an atomic force microscope tip yields force-indentation curves, which we quantitatively analyze by solving the corresponding shape equations of continuum curvature elasticity. Since the measured respon…
Pore Formation by a Bax-Derived Peptide: Effect on the Line Tension of the Membrane Probed by AFM
2007
AbstractBax is a critical regulator of physiological cell death that increases the permeability of the outer mitochondrial membrane and facilitates the release of the so-called apoptotic factors during apoptosis. The molecular mechanism of action is unknown, but it probably involves the formation of partially lipidic pores induced by Bax. To investigate the interaction of Bax with lipid membranes and the physical changes underlying the formation of Bax pores, we used an active peptide derived from helix 5 of this protein (Bax-α5) that is able to induce Bax-like pores in lipid bilayers. We report the decrease of line tension due to peptide binding both at the domain interface in phase-separa…
Formation of irreversibly bound annexin A1 protein domains on POPC/POPS solid supported membranes
2008
AbstractThe specific interaction of annexin A1 with phospholipid bilayers is scrutinized by means of scanning force and fluorescence microscopy, quartz crystal microbalance, ellipsometry, and modeled by dynamic Monte Carlo simulations. It was found that POPC/POPS bilayers exhibit phase separation in POPC- and POPS-enriched domains as a function of Ca2+ concentration. Annexin A1 interacts with POPC/POPS bilayers by forming irreversibly bound protein domains with monolayer thickness on POPS-enriched nanodomains, while the attachment of proteins to the POPC-enriched regions is fully reversible. A thorough kinetic analysis of the process reveals that both, the binding constant of annexin A1 at …
Monitoring the formation of biosilica catalysed by histidine-tagged silicatein.
2004
Surface bound silicatein retains its biocatalytic activity, which was demonstrated by monitoring the immobilisation of silicatein using a histidine-tag chelating anchor and the subsequent biosilicification of SiO(2) on surfaces by surface plasmon resonance spectroscopy, atomic force microscopy and scanning electron microscopy.
Single quantum dot emission at telecom wavelengths from metamorphic InAs/InGaAs nanostructures grown on GaAs substrates
2011
3 figuras, 3 páginas.
Formation and Evolution of Nanoscale Metal Structures on ITO Surface by Nanosecond Laser Irradiations of Thin Au and Ag Films
2012
The effect of nanosecond laser irradiations on 5 nm thick sputter-deposited Au and Ag films on Indium-Tin-Oxide surface is investigated by atomic force microscopy (AFM) and scanning electron microscopy (SEM). After 500, 750, and 1000 mJ/cm 2 fluence irradiations, the breakup of the Au and Ag films into nanoscale islands is observed as a consequence of fast melting and solidification processes. The mean nanoparticles size and surface density are quantified, as a function of the laser fluence, by the AFM and SEM analyses. In particular, the comparison between the Au and Ag islands reveals the formation of larger islands in the case of Ag for each fixed fluence. The mechanism of the nanoscale …
The zero field self-organization of cobalt/surfactant nanocomposite thin films
2009
Cobalt nanostructures have been prepared by a chemical route based on the Co(II) reduction in the confined space of cobalt bis(2-ethylhexyl)sulfosuccinate (Co(DEHSS)(2)) reverse micelles dispersed in n-heptane. This procedure involves the rapid formation of surfactant softly coated Co nanostructures followed by a slow separation process of the magnetic-field responsive Co/surfactant nanocomposites from the liquid phase. The detailed structure of thin films of the Co/surfactant nanocomposites has been investigated by scanning force microscopy (SFM). The thin films were characterized by different anisotropic features. Micrometric long domains of self-aligned ellipsoidal NPs (tens of nanometer…
Lateral force microscopy of multiwalled carbon nanotubes
2009
Carbon nanotubes are usually imaged with the atomic force microscope (AFM) in non-contact mode. However, in many applications, such as mechanical manipulation or elasticity measurements, contact mode is used. The forces affecting the nanotube are then considerable and not fully understood. In this work lateral forces were measured during contact mode imaging with an AFM across a carbon nanotube. We found that, qualitatively, both magnitude and sign of the lateral forces to the AFM tip were independent of scan direction and can be concluded to arise from the tip slipping on the round edges of the nanotube. The dependence on the normal force applied to the tip and on the ratio between nanotub…