We present a set of Molecular Dynamics simulations of the axial elongation of gold nanowires, and the compression of silver decahedral nanowires by a carbon AFM tip. We used Sutton and Chen multibody potentials to describe the metallic interactions, a Tersoff potential to simulate the carbon-carbon interactions, and a 6-12 Lennard-Jones potential to describe the metal-carbon interactions. In the elongation simulations, gold nanowires were subjected to strain at several rates, and we concentrated our attention in the specific case of a wire with an atomistic arrangement based on the intercalation of icosahedral motifs forming a Boerdijk-Coxeter (BCB) spiral, and compare it against results of nanowires with fcc structure and (001), (011), and (111) orientations. We found that the BCB nanowire is more resistant to breakage than the fcc nanowires. In the simulations of lateral compression, we made a strain analysis of the trajectories, finding that when a gold decahedral nanowire is compressed by the AFM tip in a direction parallel to a (100) face, the plastic deformation regime is considerably larger than in the case of compression exerted in a direction parallel to a twin plane, where the fracture of the wire comes almost immediately after the elastic range ends. The strain distribution and elastic response in the compression of nanoparticles with different geometries is also discussed.

Aluminum titanium oxynitride (TiAlNO) coatings were deposited on 316 steel substrates by the sputtering technique, varying the nitrogen flow from 2.5, 5, 7.5 to 10 sccm, and maintaining constant at 12 sccm the flow argon gas. We used targets of titanium and alumina with 99.995% purity. The hardness and tribological analyses were determined by Vickers microhardness and tribology (tribometer pin-disc), respectively. The results show that the coating with a nitrogen flow of 10 sccm had the lowest volumetric wear (2.047738693 mm3) and the maximum value of hardness (11.2 GPa). Analysis of X-ray diffraction evidenced the presence of three crystalline phases: Ti2N, Al2O3 and TiO2. It can be observed that by increasing the nitrogen flow, the portion of semi-Ti2N phase increases, Al2O3 decreases and TiO2 remains almost constant, and also producing a change in crystallographic orientation with reference to the Ti2N phase. Crystal grain sizes were estimated by X-ray diffraction Fourier line profile analysis using Warren–Averbach method. This analysis showed a grain size between 5 and 15 nm. Raman spectroscopy results show the presence of the TiO2 phase which corroborated the X-ray diffraction results.

The conventional magnetic recording approached the physical frontiers of the recording density. The magnetic recording must face the famous trilemma: In order to increase the recording density, smaller grain volumes are needed, but in order to ensure the thermal stability of recorded information, the anisotropy constant should be increased accordingly; what results is an increased anisotropy field, which requires higher writing fields. Such fields are unavailable with the maximum saturation magnetization obtainable with the magnetic materials of the current heads. In order to overcome these problems, new media structures have been proposed. The most promising is the bit-patterned magnetic media (BPM), intensively studied over the last years with the aim of obtaining obtain an ultra-high recording density of hard-disk drives. A BPM comprises monodisperse high-anisotropy nano-particles in a self-organized patterning. They have a higher thermal stability, a lower noise and a higher signal resolution, which leads to a higher recording density and a better SNR. They eliminate the transition noise and, due to the large fraction of the bit volume occupied by the magnetic dots, improve thermal stability. Nevertheless, some important issues such as long-range patterning, control of the surface roughness, signal readout, etc., remain critical problems to solve. Another challenge is the fact that recording on BPM is sensitive to the material and geometry parameter fluctuations that may lead to additional constraints and require tight synchronization of the write-field misregistration time and bit positions. A possible route to higher recording densities is to use a multilevel recording, where more than two states are stored per dot.

In this work, the deposition and photocatalytic response of V2O5 thin films modified with different amounts of Ag (Ag:V2O5) is reported. Films were deposited on glass and silicon substrates (100), using the pulsed laser deposition (PLD) technique. A high purity vanadium target, with a different number of silver pellets attached on it were used. Thin films were characterized by energy dispersive spectroscopy (EDS) to determine the elemental chemical composition; structural changes due to the addition of Ag were monitored by Raman spectroscopy; Optical microscopy was used to observe the surface morphology and UV-Vis spectroscopy was employed to determine optical properties. Photocatalytic response of the prepared films was studied through the degradation of a malachite green solution using a solar irradiation source.

Chitosan is biocompatible polymer has a great commercial interest because it can be processed in a sort of devices varying in shape and size, such as membranes, gels and nanoparticles. Mostly, the cell’s attachment and proliferation are very positive on nanostructurated materials with a three-dimensional formation. An irreversible network can be produced by covalently binding the polymer to the cross-linker molecules. Chitosan nanoparticles were prepared using glutaraldehyde as cross-linker. This crosss-liker mostly reacts with chitosan amino groups. In order to control and understand the physical characteristics of chitosan nanoparticle, in this work is showed the molecular behavior of chitosan/glutaraldehyde from the viewpoint of molecular interactions base in a series of molecular dynamics (MD) computer simulation. The results indicated the conformations of both molecules, which had a significant influence on the molecular association. The chitosan chains were uniformly distributed presenting a high flexibility and preference for the relaxed two-fold helix. This was due to the various associations such as intramolecular chitosan interactions –O-H···O-C-. While the chitosan-glutaraldehyde associations were due to the positive net charge density of hydrogens in the chitosan plus - H2N···C=O associations. In solid state chitosan nano and microparticles were analyzed by scanning electron microscopy (SEM). According to the micrographs results, the nanoparticles presented a monomorphism with piles of particles arranged in linear order which was consistent with the conformations determined by simulation.

The characteristics of silicon films deposited by plasma depend strongly on the reactor parameters. In our experiments, the two-level factorial design was implemented. Pressure, silane and hydrogen flows were set at high and low values for the synthesis of silicon films. Results showed that the flows of silane and hydrogen played a key role, being the influence of pressure low. In particular, the samples at high level of hydrogen exhibited the lowest deposition rate and photosensitivity. On the other hand, the samples at low level of hydrogen showed crystalline regions and high deposition rate. For the lowest dilution ratio, nano/meso-structured silicon films were obtained, showing high photosensitivity and high roughness that increases the scattering of light. These characteristics of our films make them suitable to be used in photovoltaics.

Gold nanoparticles can be used as ultimate electrical materials for storing electrons or controlling their flow for the next generation nano-electronic devices. These particles are the core element of assemblies where the electrical current is reduced to the smallest possible since electrons are controlled one by one by using the Coulomb blockade phenomenon. We prepared colloidal gold nanoparticles beteween 4 and 15 nm and grafted them on a grafted organic monolayer (GOM) on silicon. GOM are highly ordered monolayers prepared by hydrosilylation of alkene molecules and subsequently modified with an amine group so that gold nanoparticles can be firmly immobilized on top of the layer. We discuss several electrical properties at a single electron level. Using the conductive tip of KPFM, we were also able to reveal the spontaneous charging behavior of the gold nanoparticles so that the local work function of a 10 nm gold nanoparticle is only 3.7 eV. By placing an STM tip above a nanoparticle, Coulomb blockade allows controlling the number of electrons simultaneously injected in the nanoparticle. This opens the way for new kinds of single electron memories or single electron transistors.

Carbon nanotubes (CNTs) were synthesized by Chemical Vapor Deposition (CVD) from diethyl ether, butanol, hexane and ethyl acetate. A quartz tube with a stainless steel tube catalyst core with 0.019 m diameter and 0.6 m large formed the reactor. To avoid combustion, argon was used as the carrier gas. Time process ranged 30 to 60 min. The range of CNTs synthesis temperature was 680-850 °C for different precursors. Scanning Electron Microscopy micrographs have demonstrated tangled CNTs growth in all samples, thus presenting difficult length measurement. The CNTs diameters from diethyl ether are 45-200 nm, butanol diameter range from 55-230 nm, hexane diameter range is 50-130 nm and ethyl acetate range from 100 to 300 nm. Carbon content for all samples was higher than 93 %, CNTs from butanol showed carbon concentration up to 99%. FTIR, Raman and X-Ray Spectroscopies spectra for all samples demonstrated the characteristics signals present in carbon nanotubes. This research proposes a simple, effective and innovative method to synthesize CNTs by CVD on iron stainless steel catalyst in combination with diethyl ether, ethyl acetate, butanol and hexane as precursors by applying the principles of green chemistry, sustainability and its ease to be scaled.

Nanostructured silica materials with different morphologies and adjustable pore size have been studied by researches worldwide for several applications such as catalysis, separation, adsorption, and templates for new materials. The main interest in the development of these materials is to obtain a structure with a specific combination of pore sizes for a particular application. The morphology and textural properties of pores can be easily changed with the modification of the synthesis parameters, among these, the choice of surfactant or structure directing agent (SDA).

Accordingly, in this work, three types of nanostructured silica with different mesoporosity were synthesized by using of CTAB and Pluronic 123 as structure directing agents: SBA-15 and MCM-41 unimodal mesoporous silica and SBA-15/MCM-41 bimodal mesoporous silica.

To evaluate the effect of surfactant on the morphology and textural properties of pores, the materials were characterized by scanning electron microscopy (SEM), X-ray Diffraction (XRD) and nitrogen sorption (BET).

Magnetic nanoparticles (MNPs) are a class of materials that can be manipulated under the influence of an external magnetic field. Thanks to the ability of the MNPs to be guided by an external magnetic field that is like "action at a distance", combined with their low cytotoxicity and the intrinsic penetrability of magnetic fields into human tissue, opens up many applications involving the transport and/or immobilization of biological entities [1, 2].

This work is focused on the synthesis of magnetite nanoparticles by varied methods, their functionalization with nickel tetrasulfonated phthalocyanine, and the corresponding physicochemical characterization and colloidal stability studies in biologically compatible media. The in vitro production of singlet oxygen by these nanoparticles through photochemical stimulation in ultraviolet and visible region was evaluated, resulting in 4.5 and 4 µM respectly to magnetite synthetized in the group. The increase reactive oxygen species concentration in the cellular environment can result in modification and damage of cellular components, and potentially, cell death and necrosis. Therefore, these materials offer the promise of revolutionary tools for photodynamic therapy and hyperthermia, which are attractive strategies for cancer therapy without systemic toxicity.

Chitin nanowhiskers were obtained with the purpose to be used as astaxanthin protectors against the photo and thermal degradation. These nanostructures were generated by a freezing/thawing procedure using two stirring methods: mechanical and sonication, which were named as FTM and FTS respectively. Morphological and spectroscopic studies were carried out on chitin nanowhiskers by scanning electronic microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). Through a SEM analysis, chitin fibers were found uniformly spaced and oriented with the width ranged from of 20-40 nm. Furthermore, the nanowhiskers obtained by FTM showed long and flattened structures and bundles of homogeneous sizes, which have the capacity of being sites of stress concentration. In contrast, by FTS, the nanowhiskers showed coarse fibers exhibiting numerous peaks. By comparing the two methods is appreciated that FTS method provides more surface area, giving more sites for functionalization. Fourier transform infrared spectroscopy (FTIR) allowed the determination of free movement of functional groups on the surface of samples obtained by FTM and FTS methods. Significant differences of signals in the spectra indicate that there were more unassociated amides in the nanowhiskers obtained by FTS than by FTM.

The optical and structural properties of co-doped HfO2 thin films with rare earth trivalent ions prepared by ultrasonic spray pyrolysis technique, are reported. An arrangement of multi-layer (Si-SiO2-HfO2:Eu3+-HfO2:Tb3+-HfO2:Tm3+-SiO2) were deposited on silicon substrates at temperatures from 400 to 550°C, using acetyl acetonates as precursory reagents. A refractive index value of 2.1 was determined by spectral ellipsometry. The surface morphology was obtained by AFM measurements. For 50 to 550 nm thickness films, an average roughness value of ∼56.8 Å was obtained for different substrate temperatures and grown deposition times. EDS measurements showed the presence of hafnium, and rare earths dopants as elemental composition. XPS measurements demonstrated that hafnium and rare earths oxidation species are formed at hafnium dioxide thin films. Photoluminescence emission spectra of multi-layer structures present characteristic emission peaks associated with Tb+3, Eu3+, and Tm3+ dopants. The results presented above motivate us to consider that these multilayer structures could be appropriate to be used as a rare earth host to improve optical emission.

Y2O3 and Gd2O3 upconversion nanoparticles (UCN) co-doped with Yb3+ and Er3+ can absorb and upconvert near infrared (NIR) radiation into visible light. These UCN find application in bioimaging, as an important tool to diagnose and visualize cancer cells. The UCN can be used as biolabels to identify the cells; the nanoparticles can be coated and functionalized with ligands that bind to receptors on the surface of the cell. In this project, the UCN were synthesized by sol-gel method and subsequently coated with a thin silica shell by using the Stöber method. The core-shell UCN were functionalized with amine group to enable folic acid conjugation. The functionalized core-shell nanoparticles were analyzed by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and luminescence measurements. Concentrations of bare and coated/functionalized UCN between 0.001 µg/mL and 1 µg/mL were tested on two different cell lines from human cervix carcinoma (HeLa) and human colorectal adenocarcinoma (DLD-)1 with colorimetric assay based on the MTT reagent (methy-134 thiazolyltetrazolium). The results show good luminescence spectra on all core-shell UCN. The MTT assays show that some concentrations of bare UCN of Y2O3: Er, Yb (1%, 1% mol) and Gd2O3 were cytotoxic for cervical adenocarcinoma cells (HeLa). For human colorectal adenocarcinoma all UCN are non-cytotoxic. The UCN with silica-aminosilane functionalization (APTS/TEOS) were non-cytotoxic on both cell lines.

Development of polymers with antimicrobial characteristics can avoid deterioration and assist in containing spread of pathogens harmful to human health. This study aimed to compare the antimicrobial and mechanical properties of polymeric matrices containing organic antimicrobial additives. Silver organomodified bentonite (Ag_bentonite) and organochlorine molecule in a masterbatch based polyethylene (Cl_PE) were tested in proportion of 2% in a thermoplastic elastomeric formulation. The polymeric matrices were prepared by melt mixing and evaluated in tensile and antimicrobial properties against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) strains. The additives were characterized by thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). The nanoscale of Ag_bentonite was verified by SEM. TGA assay showed that Cl_PE is more sensitive to heat than Ag_bentonite. As a result of this lower thermal stability, the addition of Cl_PE reduced the tensile properties of the compound. The sample with Cl_PE was effective against both bacterial strains, reducing the populations of S. aureus and E. coli in 99 and 96%, respectively. The addition of Ag_bentonite did not affect the tensile strength and decreased in 97 and 40% S. aureus and E. coli populations, respectively. The results indicate that the use of organic additives is promissory, but further modifications in processing must be necessary.

In this work there was studied the effect of nano-Mg/Al hydrotalcite (NHT) as filler on maleic anhydride grafted linear low density polyethylene (LLDPE-g-MA). NHT was synthesized by the coprecipitation method with a ratio of Mg/Al=6 and nanocomposites were prepared using 1, 3 and 5 %wt of filler via melt-blending.

Morphological and structural analysis of NHT were performed and for nanocomposites, tensile tests and thermal properties were measured. Results showed that filler was well dispersed in the LLDPE matrix, mechanical properties were enhanced in most of the cases and thermal stability improvements were achieved in the nanocomposites.