Optical Nanoparticle Sorting Elucidates Synthesis of Plasmonic Nanotriangles.

We investigate the optical and morphological properties of gold nanoparticles grown by reducing a gold salt with Na2S. Lasers are tuned to the observed plasmon resonances, and the optical forces exerted on the nanoparticles are used to selectively print individual nanoparticles onto a substrate. This enables us to combine dark-field spectroscopy and scanning electron microscopy to compare the optical properties of single nanoparticles with their morphology.

Localization of adhesins on the surface of a pathogenic bacterial envelope through atomic force microscopy.

Bacterial adhesion is the first and a significant step in establishing infection. This adhesion normally occurs in the presence of flow of fluids. Therefore, bacterial adhesins must be able to provide high strength interactions with their target surface in order to maintain the adhered bacteria under hydromechanical stressing conditions.

Surface-diffusion-driven decay of high-aspect-ratio gratings: existence of morphologically related classes.

We present numerical and theoretical results concerning the technologically important process of evolution of high-aspect-ratio profiles due to surface diffusion under thermal treatment. We show how a broad class of initial gratings adopt, after a short transient stage, a typical shape that can be accurately described as a curve whose curvature has only two single Fourier modes as a function of the arc-length parameter. Moreover, we introduce a set of evolution equations for the relevant parameters that accounts very accurately for both morphological and kinetic aspects of the transformation processes for these curves in a wide region in parameter space.

Adhesin contribution to nanomechanical properties of the virulent Bordetella pertussis envelope.

Adherence to a biological surface allows bacteria to colonize and persist within the host and represents an essential first step in the pathogenesis of most bacterial diseases. Consequently, the physicochemical properties of the outer membrane in bacteria play a key role for attachment to surfaces and therefore for biofilm formation. Bordetella pertussis is a Gram-negative bacterium that colonizes the respiratory tract of humans, producing whooping cough or pertussis, a highly infectious disease.

One-dimensional gratings evolving through high-temperature annealing: sine-generated solutions.

Sine-generated curves (i.e. curves in which the curvature is a sine function of the arc-length parameter) have been used in the past to describe river meanders.

Surface-diffusion-driven decay of patterns: beyond the small slopes approximation.

By combining analytical results and computer simulations, we studied the continuous theory of surface diffusion applied to the decay of periodic high-aspect-ratio patterned substrates. Our results show that, after a transient stage, and for a broad class of initial conditions, patterns adopt a 'universal' mathematically well-specified shape that depends on two coefficients. Moreover, we were able to determine the time-dependence of such coefficients, which enabled us to mathematically reconstruct the pattern's shape at any subsequent time.

Continuous and discrete modeling of the decay of two-dimensional nanostructures.

In this work we review some recent research on the surface diffusion-mediated decay of two-dimensional nanostructures. These results include both a continuous, vectorial model and a discrete kinetic Monte Carlo approach. Predictions from the standard linear continuous theory of surface-diffusion-driven interface decay are contrasted with simulational results both from kinetic and morphological points of view.

Spontaneous nanoripple formation on metallic templates.

Nanoripple structures spontaneously formed at room temperature during chemical and electrochemical deposition of metals, semiconductors, and alloys on gold and copper templates, patterned with nanocavities, have been studied by atomic force microscopy (AFM) and scanning tunneling microscopy (STM). Annealing the templates at approximately equal to 373 K also results in ripple formation. Both experimental results and modeling, including anisotropic surface diffusion, demonstrate that nanocavity size in the template determines the ripple wavelength and amplitude, prior to a final stage of coarsening.

Kinetic Monte Carlo study on the decay of two-dimensional nanostructures: influence of the activation energy of diffusion on kinetic and morphological properties.

Surface diffusion-mediated decay of two-dimensional nanostructures is studied by means of a kinetic Monte Carlo model. We consider several possible choices for the activation energies associated with possible diffusion paths, including simple phenomenological models, as well as results provided by the embedded atom model. Numerical results show that kinetic aspects of the evolution are quite sensitive to the activation energy model chosen.

Modeling growth from the vapor and thermal annealing on micro- and nanopatterned substrates.

We propose a -dimensional mesoscopic model to describe the most relevant physical processes that take place while depositing and/or annealing micro- and nanopatterned solid substrates. The model assumes that a collimated incident beam impinges over the growing substrate; scattering effects in the vapor and reemission processes are introduced in a phenomenological way as an isotropic flow. Surface diffusion is included as the main relaxation process at the micro- or nanoscale.

Dynamics of solid growth under a gravitational field: influence of the formation of a diffusive layer.

We discuss the gravitational sedimentation of particles in terms of a stochastic model considering, in view of experimental evidence, that the aggregation to the growing surface (deposit) is mediated by the formation of a layer of suspended particles subject to gravitational forces, thermal agitation, as well as aggregation (contact) forces. The aggregation of such partially buoyant particles is ruled by the rates of occurrence of the different stochastic events: incorporation to the layer of suspended particles, sedimentation, and gravitationally biased diffusion. The model introduces bridges across different standard solid on solid deposition models which can be considered as limit cases of the present one.

Role of surface heterogeneity and molecular interactions in the charge-transfer process through self-assembled thiolate monolayers on Au(111).

A comparative study of charge-transfer processes from/to methyl-terminated and carboxylate-terminated thiolate-covered Au(111) surfaces to/from immobilized methylene blue (MB) molecules is presented. Scanning tunneling microscopy images with molecular resolution reveal the presence of molecular-sized defects, missing rows, and crystalline domains with different tilts that turn the thickness of the alkanethiolate SAM (the spacer) uncertain. The degree of surface heterogeneity at the SAMs increases as the number of C units (n) in the hydrocarbon chain decreases from n = 6.

Probing universality classes in solid-on-solid deposition.

We consider several stochastic processes corresponding to the same physical solid-on-solid deposition problem. Simplified models presenting the same (conditional) mean and variance for each process are also introduced as well as generalizations in terms of the deposition of blobs and probabilistic deposition rules. We compare the evolution of the roughness as a function of time for a three-parameter family that includes as limit cases the Family model and the Edwards-Wilkinson equation, showing that in all cases the derived models with the same mean and variance are indistinguishable from the originating models in terms of the evolution of the roughness.