Using a Sutton and Chen interatomic potential, we study the molecular dynamics of Au-Pd nanoparticles with an initial icosahedral structure at different temperatures and concentrations, where each relative concentration of the 561-atom particles was made by placing atoms of the same species at equivalent sites, in order to identify under which conditions the melting transition temperature appears for each particle. In addition, we compute global order parameters in order to correlate the obtained results with the caloric curves of each particle. As a result, we observe that the melting transition temperature depends on the relative atomic positions of gold and palladium. The melting transition temperature of the Au-Pd alloy particles appears at higher temperature than that of the pure-gold particle. From the analysis of the structure of the particles, we found that the melting temperature increases with the proportion of gold atoms, and for those particles with a higher concentration of palladium on the surface, we observe an early migration of gold atoms before the melting transition temperature appears.

Recently, bimetallic nanostructures and nanoalloys have received special interest due to their promising chemical and physical properties. Specifically, Cu-Ni nanoparticles have been investigated for biomedical and catalytic applications. This work reports the synthesis of alloys and bimetallic nanoparticles of CuxNi100-x (x = 20, 40, 50, 60 and 80) by sol-gel method, and their morphological, structural and magnetic characterization. A precursor material was prepared using a standard Pechini method and then CuNi nanoparticles were obtained by calcination treatments of the precursor in H2/N2atmosphere at 600 and 700°C for 15 minutes. The resulting nanoparticles were characterized by X-ray diffraction (XRD), which reveals that this method led to the formation of CuNi substitutional nanoalloys and bimetallic nanoparticles with good cristallinity related with the calcination temperatures and Cu:Ni weight ratios. Transmission electron microscopy (TEM) shows nearly monodisperse and uniform spherical nanoparticles with sizes between 40 and 70 nm. The magnetic properties were studied using SQUID magnetometry, according with these results, the CuNi nanoparticles showed a ferromagnetic behavior, the magnetization value increases as a function of the weight percentage of Ni.

We present extensive pseudopotential density functional theory calculations dedicated to analyze the stability, electronic properties, and structural isomerism in Cu6 clusters. We consider structures of different symmetries and charge states. Our total energy calculations reveal a strong competition between two- and three-dimensional atomic arrays, the later being mostly energetically preferred for the anionic structures. The bond lengths and electronic spectra strongly depend on the local atomic environment, a result that is expected to strongly influence the catalytic activity of our clusters. Using the nudged elastic band method we analyze the interconversion processes between different Cu6 isomers. Complex atomic relaxations are obtained when we study the transition between different cluster structures; however relatively small energy barriers of approximately 0.3 eV accompany the atomic displacements. Interestingly, we obtain that by considering positively charged Cu6+ systems we reduce further the energy barriers opposing the interconversion process. The previous results could imply that, under a range of experimental conditions, it should be possible to observe different Cu6cluster structures in varying proportions.

Ultrasonically generated forces are well known for dispersing and deagglomeration of small volumes in laboratory and bench-top scale. By the evaluation and optimization of the most important ultrasonic parameters and the development of large scale ultrasonic machinery, ultrasound forces can be applied also for particle size reduction and wet-milling of nano-particles in industrial scale.

In the framework of bioanalytics and multiple array detection, we developed a fully portable and low-cost detection system based on Localized Surface Plasmon Resonance (LSPR) in a transmission configuration (T-LSPR). The transmission approach is suitable to be scaled to small dimension systems and to enable high-density array measurements on the same platform. Our setup is made out of off-the-shelf components and consists of a set of discrete light sources and a couple of light-detectors which enable a differential measurement setup. An algorithm fits the measured data and extracts the information of the plasmon peak position in the spectrum.

The performance of our T-LSPR measurement system has been characterized on a set of Fluorinated Tin Oxide-coated glass slides covered with gold Nanoislands (NIs). The samples have been modified with a single-stranded DNA layer and a real-time DNA hybridization experiment has been performed. Here we demonstrate that the proposed T-LSPR device, based on the characterization of the plasmon peak with a differential approach, is able to monitor real-time DNA hybridization on surface, and to precisely measure the position of the peak with a standard deviation in wavelength of 0.2 nm.

1-3 BaTiO3-PVDF hybrid nanocomposites were prepared by combining electrospinning, sol-gel and spin-coating techniques. First, one-dimensional structures of barium titanate (BaTiO3) were obtained by electrospinning. An alcoholic solution consisting of Ba2+ and Ti4+ions (1:1 molar ratio) and poly(vinylpyrrolidone) was electrospun at 15 kV, with a tip-to-collector distance of 15 cm and a feed rate of 0.5 mL/h. Ceramic fibers were obtained after sintering the as-spun fibers at 900 °C for 2 hours. In a second step, poly(vinylidene fluoride) (PVDF) was incorporated to the oxide fibers by spin-coating a dimetilformamide solution, thus conforming 1-3 ceramic-polymeric hybrid nanocomposites on stainless steel substrates.

Scanning electron microscopy images showed that the as-spun fibers were smooth, long and continuous with an average diameter of 155 ± 40 nm, ranging from 60 to 240 nm, while sintered fibers presented a reduction in size, with an average diameter of 115 ± 16 nm, ranging from 96 to 120 nm. Sintered nanofibers were also long and continuous but with a rough surface. X-ray diffraction confirmed the perovskite-type structure of the BaTiO3. A structure refinement revealed a degree of tetragonality of 1.0046.

The polymer crystalline phases were identified by infrared spectroscopy on ATR mode. This study showed the presence of both β and γ polar phases, and absence of non-polar α phase, according to the characteristic bands for such crystalline phases.

The nanocomposites exhibited a ferroelectric behavior and electrical polarization according to their ceramic and polymeric components.

In the present work, a comparison study of the Ni catalysts supported on SBA-15 silica support prepared with and without the addition of organic ligands (citric acid and ethylenediaminetetraacetic acid (EDTA) was undertaken. The aim of this study was to inquire on the effect of the addition of organic ligands on the characteristics of the supported NiO and Ni nanoparticles and on their activity and selectivity in hydrogenation (HYD) of aromatics. Catalysts with different metal loadings (5, 10 and 20 wt. % of Ni) were prepared, characterized by nitrogen physisorption, small-angle and powder XRD, TPR, UV-vis DRS, and HRTEM, and tested in HYD of naphthalene (NP). It was found that Ni(II)-Ligand complexes were formed in aqueous solutions of Ni(NO3)2 containing citric acid (CA) or EDTA. Catalysts prepared from impregnation solutions with and without ligands had different textural characteristics and dispersion of NiO particles after calcination at 500 °C for 4 h. As it was shown by XRD, DRS and TPR, dispersion of NiO particles significantly increased when EDTA was used, whereas it noticeably decreased after the addition of CA. Similar trends were observed in the dispersion of metallic Ni particles after reduction of the NiO/SBA-15 precursors (HRTEM). In line with the characterization results, catalytic activity tests revealed strong differences in the activity of the prepared Ni/SBA-15 catalysts in hydrogenation of naphthalene. Catalysts prepared with the addition of EDTA were more active than those prepared without ligands. On the contrary, the HYD activity of a series of the Ni catalysts prepared with citric acid was lower than of other corresponding samples. The reasons of such a different behavior of the catalysts prepared with two organic ligands used are discussed on the basis of the obtained characterization results.

Dendrons with a porphyrin core and π-conjugated dendron branches have been synthesized and characterized. The dendrons showed an all trans configuration. Cubic non-linear optical behavior of the styryl and porphyrin-containing dendrimers was tested viaZ-Scan measurements in spin-coated film samples.

Composite layers of the detonation nanodiamond/polymer type possess a spatial organization of components with new structural features and physical properties, as well as complex functions due to the strong synergistic effects between the nanoparticles and polymer [1]. Composite layers were deposited by a plasma polymerization (PP) process of the detonation nanodiamond (DND) particles added to a hexamethyl disiloxan (HMDS) monomer [1]. The incorporation of silver ions in the polymer leads to the production of materials that are highly efficient against bacterial colonization and allows better cell adhesion and spreading. [2] For cell culture processes, fibronectin (FN) treatment is one of the commonly used approaches to enhance the cell adhesion on a surface [3].

As an integrated part of our search for improved materials for life science applications such as biomaterials and biosensors, the objective of the present study is to investigate the interaction of Ag-based composite surfaces with FN protein. Two types of composite layers, Ag-ND/PPHMDS and Ag-nano/PPHMDS were obtained by plasma polymerization of HMDS and nanoparticles of Ag and Ag-DND. The composite layers are representative of the different incorporation of the Ag in the polymer net. The structures studied, consisting of composite layers with adsorbed FN were optically characterized with Ellipsometry, Fourier Transform Infrared (FTIR) and Ultra Violet (UV) Spectroscopy as well as by stylus profiling (Talysurf). The kinetic study of the FN adsorption indicates that the process depends on the FN concentration and the exposure time as well as on the surface chemistry of the composites. Compared to the reference sample, all composite layers exhibit an indication of a stronger ability to initiate the intrinsic pathway of coagulation.

Plasma surface activation and antibacterial properties of nanocomposites of polypropylene/silver nanoparticles (PP/nAg) and nylon-6/silver nanoparticles (Ny6/nAg) were investigated. The nanocomposites were prepared by melt blending assisted by ultrasound, while surface activation was achieved by means of argon plasma. To evaluate the antimicrobial properties of the nanocomposites, pathogen microorganisms such as Pseudomonas aeruginosa and Aspergillus niger were tested. Scanning Electron Microscopy (SEM) analyses showed a uniform dispersion of nanoparticles within the polymer matrix, though the presence of some agglomerates was also appreciated. On the other hand, surface topography by Atomic Force Microscopy (AFM) suggested that ions from the argon plasma generated ion collisions with the surface of the nanocomposites removing or etching polymer from surface and improving silver nanoparticles exposure, increasing their antimicrobial properties as corroborated by antimicrobial analyses. Nanocomposites exposed to argon plasma presented higher antimicrobial properties than the ones not exposed. These results indicated that plasma treatment increased the contact area of the nanoparticles with the microorganisms and enhanced the antimicrobial properties of nanocomposites. The results also showed that PP/nAg nanocomposites presented higher bacterial inhibition than Ny6/nAg nanocomposites, indicating that the chemical structure of the polymer also plays a big role in the final performance of the composite.

The nanoencapsulation in biocompatible inorganic materials with human cell activity is a leading technology to control the process of releasing the drug in the right place. At present, the sol-gel process has emerged as a promising platform for the immobilization, stabilization and encapsulation of biological molecules such as enzymes, antibodies, microorganisms, and a variety of drugs. The matrices obtained are chemically inert, hydrophilic and easy synthesis. They have high mechanical strength, thermal stability in wide temperature ranges and absorb organic solvents so insignificant compared with other organic polymers. They are resistant to microbial attack and exhibit high biocompatibility with the body, as provided for implantation in situ in the treatment of various diseases. An additional advantage is that it provides viability encapsulated molecules, since these matrices act as reservoirs of water thus helping to maintain the biological activity of enzymes, antibodies, cells, and drugs for the moisture level required for the molecule. We used the action of the active ingredients of tepezcohuite (condensed tannins) to assess the capacity aseptic surgical wound healing than 1 cm in diameter in New Zealand white rabbits. Experimentally and statistically demonstrating the effectiveness of healing nanoreservoirs Tan/TiO2-150 the weight of tannins by 60% compared to condensed tannins as such, TiO2and isotonic saline.

Dendrons with dodecyl ended groups joined benzyloxy moieties were attached to a cyclotriveratrylene core. The dendrimers were used in Diederich cyclopropanation reaction with the fullerene C60. The structure of the synthesized dendrimers was confirmed by 1H- and 13C-NMR, MALDI-TOF mass spectrometry and elemental analysis.

A series of NiW catalysts supported on SBA-15-type materials modified with Al, Ti or Zr were prepared and tested in simultaneous hydrodesulfurization (HDS) of two model compounds: dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT). Catalysts were prepared by incipient wetness impregnation of SBA-type materials (pure silica SBA-15, Al-SBA-15, Ti-SBA-15 or Zr-SBA-15) using Keggin-type heteropolyacid H4SiW12O40 as active phase precursor and nickel nitrate. Nominal composition of the catalysts was 19 wt.% of WO3 and 3 wt.% of NiO. The supports and catalysts were characterized by SEM-EDX, N2physisorption, small-angle and powder XRD, UV-Vis DRS, TPR and HRTEM. It was shown that a good dispersion of Al, Ti and Zr species on the SBA-15 surface was reached. The characteristic structure of the SBA-15 support was preserved in all supports and NiW catalysts. Addition of metal atoms (Al, Ti, Zr) on the SBA-15 surface prior to catalysts’ preparation improved dispersion of Ni and W oxide species in calcined catalysts. HRTEM characterization of sulfided catalysts showed that the dispersion of NiW active phase was also better on metal-containing SBA-15 supports than on the pure silica one. All NiW catalysts supported on metal-containing SBA-15 materials showed an outstanding catalytic performance in HDS of both model compounds used (DBT and 4,6-DMDBT). A good correlation was found between the dispersion of sulfided NiW active phase and catalytic activity results. The highest HDS activity was obtained with the NiW catalyst supported on Zr-containing SBA-15 molecular sieve, which makes it a promising catalytic system for ultra-deep hydrodesulfurization of diesel fuel.

In this paper, the effect of anodization time on the properties of TiO2 nanotube humidity sensors is reported. TiO2 nanotube arrays were grown by anodization of Ti foil using diethylene glycol and ammonium fluoride. Highly ordered TiO2 nanotube arrays were obtained, with the length of tube increasing from 4 to 20 μm as the time of anodization increases, at the expense of nanotube integrity. Humidity sensors based on TiO2 nanotube arrays were fabricated in impedance mode with ITO as top contact. The results revealed that sensor performance does not correlate with anodization time, regardless of enhanced area, showing an optimum morphology at 4h and 10h. The increase resistivity of the sensors upon water exposure, a donor molecule, is explained by the lack of TiO2 stoichiometry and the fluctuations in the concentration of oxygen vacancies.

Molecular Dynamics (MD) simulations are performed to calculate the interfacial energy between zinc oxide (ZnO) and graphitic carbon for the study of solid–solid adhesion. The MD model consists of a ZnO slab and a single layer of graphitic carbon. The calculation was validated experimentally by atomic force microscopy (AFM) liftoff. A polishing process was applied to create a tip with a flat surface that was subsequently coated with a ZnO film allowing force displacement measurement on Highly Oriented Pyrolitic Graphite to validate the simulations. The MD simulation and AFM lift-off show good agreement with adhesive energies of 0.303 J/m2 and 0.261 ± 0.054 J/m2, respectively.

TiO2 nanoflowers were obtained on modified ITO substrates by solvothermal synthesis. Surface modification was achieved with a layer of TiO2 seeds/nucleus obtained by dip-coating at various pH and dip cycles. Field emission scanning electron microscopy results indicated that at all nucleation conditions there was a dual population of TiO2 nanoparticles and nanoflowers. For a particular pH, the effect of increasing the number of dips was to increase the size and number of the nanoflowers, whereas for a fixed number of dips, the increase in pH causes a decrease in nanoflower population. The comparison with solvothermal films obtained on unmodified substrates indicates that TiO2 nanoflowers grew up on the nucleation sites. These microstructural changes determine the active surface area and sensing properties of the solvothermal films. At room temperature, no evidence of superior ethanol sensing properties was found for TiO2 nanoflowers, which show larger resistivity than TiO2 nanoparticles.

In this work, the thermal conductivity of composites made up of carbon nanotubes embedded in a polyester resin is investigated by comparing experimental data with theoretical predictions. The composite samples were prepared with a random and aligned distribution of carbon nanotubes. Its thermal conductivity is then measured by using the photothermal radiometry technique. The obtained experimental data is accurately described by the proposed theoretical model, which takes into account the size effects of the nanotubes. It is expected that the obtained results can provide useful insights on the thermal design of composites based on carbon nanotubes.

We present a joint experimental and theoretical study dedicated to analyze the properties of Boron-Nitride (BN) nanotubes. First, multi-walled boron-nitride (MWBN) nanotubes were prepared by means of a modified electric arc discharge technique using boron-nitride powder. In a first stage, the BN powder was subjected to a ball milling process for about 100 hours in an atmosphere of ammonia. Later on, BN nanoparticle formation took place after the preparation of a pressed pellet at 300 °C to 25 kPa which was sintered in a furnace at approximately 1000 °C in nitrogen atmosphere for 15 hrs. The pellets were subsequently incorporated to the electrical arc discharge set up to obtain the MWBN nanotubes. The as-prepared MWBN nanotubes samples were characterized by scanning electron microscope, X-ray photoelectron spectroscopy, and micro RAMAN spectroscopy. Second, and in order to understand the measured data, extensive density functional theory calculations were performed. We present low energy atomic configurations for model finite-length armchair, zigzag, and chiral single-walled BN nanotubes, as well as for two-dimensional BN sheets. We calculate the vibrational spectra and the optical gap of each one of our considered structures and reveal how precise details of the local atomic environment can be revealed. Finally, we consider BN nanotubes functionalized with NH2, glycine and S-H molecules. We present the structural characteristics of the adsorbed configurations, charge transfer effects, and the electronic behavior. We conclude by underlining the crucial role played by molecular functionalization in order to tune the properties of these kinds of systems.

In this paper, an experimental study aimed at achieving better control of the deposition patterns of carbon nanotubes (CNTs) is presented. CNTs were grown on a long of reactor by the catalytic chemical vapor deposition (CVD) of a benzene/ferrocene solution at 1073 K. The deposition patterns on the substrate were controlled for process times and carrier gas flow rates. In order to investigate the reaction mechanism and production rate for the growth of CNTs in catalyst CVD, computational fluid dynamics (CFD) model was developed in this study. Then the computational model was integrated with the dynamic model to optimize the process parameters formulating a correlation between turbulence, deposition rate for the growth of carbon nanotubes and parameters as process time and carrier gas flow rate. Scanning electron microscopes (SEM) are used to characterize carbon nanotubes products.

In this work we alternate breaking-symmetry-substrates (BSS) and non-breaking-symmetry-substrates (NBSS) such as SiC and SiO2,following the Silver-Mean (MSMGS) and Period-Doubling (MPDGS) sequences. We implement the Transfer Matrix technique to calculate the transmittance and the linear-regime conductance as a function of the most relevant parameters of the multilayered graphene structures: energy and angle of incidence, widths of BSS and NBSS regions and the generation of the quasi-regular sequence. We analyze the main difference of the transmission and conductance properties between MSMGS and MPDGS.