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This paper describes bacterial organization on nano/micropatterned surfaces with different chemical properties, which show different interactions with the biological systems (inert, biocompatible, and bactericide). These surfaces were prepared by molding techniques and exposed to Pseudomonas fluorescens (P. fluorescens) cultures. Results from atomic force microscopy and optical imaging demonstrate that the structure of P. fluorescens aggregates is strongly dependent on the surface topography while there is no clear linking with the physical-chemical surface properties (charge and contact angle) of the substrate immersed in abiotic culture media. We observe that regardless of the material when the surface pattern matches the bacterial size, bacterial assemblages involved in surface colonization are disorganized. The fact there is not a relationship between surface chemistry and bacterial organization can be explained by the coverage of the surfaces by adsorbed organic species coming from the culture medium. Viability assays indicate that copper behaves as a toxic substrate despite the presence of adsorbed molecules. The combination of surface traps and biocidal activity could act synergistically as a suitable strategy to limit bacterial spreading on implant materials.

In this paper, the synthesis of gold at gold(I)-thiolate core at shell nanoparticles is described for the first time. The chemical nature and structure of these nanoparticles were characterized by a multi-technique approach. The prepared particles consist of gold metallic cores, about 1 nm in size, surrounded by stable gold(I)-thiomalate shells (Au at Au(I)-TM). These nanoparticles could be useful in medicine due to the interesting properties that gold(I)-thiomalate has against rheumatoid arthritis. Furthermore, the described results give new insights in the synthesis and characterization of metallic and core at shell nanoparticles.

We have prepared ultrathin, nanostructured melanin films on Au(111) by means of electrochemical self-assembly. These films were characterized by using Auger electron spectroscopy, X-ray absorption near-edge structure spectroscopy, scanning tunneling microscopy, magnetic force microscopy, and electrochemical techniques. Two types of nanostructures are present in the film: melanin nanoparticles and Fe(3)O(4) nanoparticles. The melanin nanoparticles contain Fe bonded to oxygen-containing phenolic groups in an octahedral configuration similar to that found in Fe(2)O(3). The inorganic-organic composite exhibits magnetic properties and catalyzes the electroreduction of hydrogen peroxide in alkaline and neutral electrolyte solutions. The electrocatalytic activity depends on the Fe-bound melanin and appears to be similar to that found for Fe-porphyrins.

The surface structure of dodecanethiolate self-assembled monolayers (SAMs) on Au(111) surfaces, formed from the liquid phase, have been studied by grazing incidence X-ray diffraction (GIXRD), scanning tunneling microscopy (STM), and electrochemical techniques. STM images show that the surface structure consists of (square root 3 x square root 3)-R30 degrees domains with only a few domains of the c(4 x 2) lattice. The best fitting of GIXRD data for the (square root 3 x square root 3)-R30 degrees lattice is obtained with alkanethiolate adsorption at the top sites, although good fittings are also obtained for the fcc and hcp hollow sites. On the basis of this observation, STM data, electrochemical measurements, and previously reported data, we propose a two-site model that implies the formation of incoherent domains of alkanethiolate molecules at top and fcc hollow sites. This model largely improves the fitting of the GIXRD data with respect to those observed for single adsorption sites and, also, for the other possible two-site combinations. The presence of alkanethiolate molecules adsorbed at the less favorable top sites could result from the adsorption pathway that involves an initial physisorption step which, for steric reasons, takes place at on top sites. Once the molecules are chemisorbed, the presence of energy barriers for alkanethiolate surface diffusion, arising mostly from chain-chain interactions, "freezes" some of them at the on top sites, hindering their movement toward fcc hollow sites. By considering the length of the hydrocarbon chain and the adsorption time, the two-site model could be a tool to explain most of the controversial results on this matter reported in the literature.

Resonant Raman and surface-enhanced Raman scattering (SERS) spectroscopies, complemented with scanning tunnel microscopy and electrochemical techniques, have been used to obtain information about the amount and spatial distribution of methylene blue (MB) molecules immobilized on sulfur and four ultrathin molecular alkanethiolate films self-assembled on Au(111) and rough Au electrodes. The intensity of the Raman signals allow one to estimate the amount of immobilized MB at different organic films, whereas the decrease in the SERS intensity as a function of distance for the rough Au electrodes is used to locate the average position of the MB species with respect to the Au substrate. We found that significant amounts of cationic MB species are able to diffuse into methyl-terminated thiols, but they are stopped at the outer plane of the self-assembled monolayer (SAM) by negatively charged carboxylate groups. The relative shift of C-N stretching Raman modes indicates that the binding of MB to S is different from that found for MB on thiols. Most of the molecules immobilized on methyl- and carboxylate-terminated thiols are electrochemically inactive, suggesting that strong coupling between the Au electrode and the MB molecules is needed for charge transfer. Our results are consistent with a small population of electrochemically active MB species very close to the Au surface that reach this position driven by their lipophilic (hydrophobic) character through defects at SAMs.

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. The stochastic model is built following population dynamics considerations; both stochastic simulations and the deterministic limit are analyzed. Numerical aspects regarding its implementation are also discussed. We study the shape-preserving growth mode, the coupling between shadowing effects and random fluctuations, and the spatial structure of noises using numerical simulations. We report important deviations from linear theories of surface diffusion when the interfaces are not compatible with the small slope approximation, including spontaneous formation of overhangs and nonexponential decay of pattern amplitudes. We discuss the dependence of stationary states with respect to the boundary conditions imposed on the system.

Pattern transfer with high resolution is a frontier topic in the emerging field of nanotechnologies. Electrochemical molding is a possible route for nanopatterning metal, alloys and oxide surfaces with high resolution in a simple and inexpensive way. This method involves electrodeposition onto a conducting master covered by a self-assembled alkanethiolate monolayer (SAMs). This molecular film enables direct surface-relief pattern transfer from the conducting master to the inner face of the electrodeposit, and also allows an easy release of the electrodeposited film due their excellent anti-adherent properties. Replicas of the original conductive master can be also obtained by a simple two-step procedure. SAM quality and stability under electrodeposition conditions combined with the formation of smooth electrodeposits are crucial to obtain high-quality pattern transfer with sub-50 nm resolution.

In this work, the electrochemical formation of alkanethiolate self-assembled monolayers (SAMs) on Ni(111) and polycrystalline Ni surfaces from alkanethiol-containing aqueous 1 M NaOH solutions was studied by combining Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS), electrochemical techniques, and density functional theory (DFT) calculations. Results show that alkanethiolates adsorb on Ni concurrent with NiO electroreduction. The resulting surface coverage depends on the applied potential and hydrocarbon chain length. Electrochemical and XPS data reveal that alkanethiolate electroadsorption at room temperature takes place without S-C bond scission, in contrast to previous results from gas-phase adsorption. A complete and dense monolayer, which is stable even at very high cathodic potentials (-1.5 V vs SCE), is formed for dodecanethiol. DFT calculations show that the greater stability against electrodesorption found for alkanethiolate SAMs on Ni, with respect to SAMs on Au, is somewhat related to the larger alkanethiolate adsorption energy but is mainly due to the larger barrier to interfacial electron transfer present in alkanethiolate-covered Ni. A direct consequence of this work is the possibility of using electrochemical self-assembly as a straightforward route to build stable SAMs of long-chained alkanethiolates on Ni surfaces at room temperature.

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. Finally, we show that although all the models studied belong to the same universality class, some relevant features such as the final surface roughness are reproduced only for models within a restricted class determined by sharing the same (conditional) mean and variance.