The study of several types of plasma reactors used to obtain carbon nanostructures (CNS) is realized in the Laboratory of Plasma Applications. To obtain carbon nanotubes (CNT) thermal plasma was used and carbon nanofibers (CNF) were obtained with glow discharge. Optical emission spectroscopy was applied to correlate some plasma parameters with CNS growth. Several analytical techniques are used to study CNS obtained by both plasma techniques.

In this work, we present results concerning the use of CNS as harmful gases traps and some results of a CNT based supercapacitor prototype are also depicted.

Experimental results here detailed, show the capacity of CNF to absorb nitrogen oxides (NOx), sulfur dioxide (SO2) and, at less proportion, carbon dioxide (CO2).

CNF films were obtained by electrophoretic deposition technique and by adding CNT ink; preliminary results showed a capacitance value of 2.69 F/g. This value remains still low compared to some supercapacitors, therefore additional work has to be done in order to improve the capacitance value.

While the most promising longitudinal recording systems cannot surpass the theoretical limit of about 200 Gb/in2 for areal recording density and the demand for higher densities is permanently increasing, the perpendicular magnetic recording constitutes the realistic issue to the longitudinal one. The perpendicular magnetic recording offers significant advantages, the most important being stronger write and read fields, and therefore the use of media of higher anisotropy, smaller grain size, higher signal-to-noise ratio, and a better thermal stability. Unfortunately, the perpendicular recording has to cope some important physical and technological difficulties. To overcome them, many ingenious solutions were proposed. In this paper the coupled granular/continuous (CGC) media, a subtle association of the continuous and, respectively, granular media, are analysed from the viewpoint of their magnetic and recording properties. The challenges and possible improvements of CGC media are discussed.

First-order-reversal-curves (FORCs) are an elegant, nondestructive tool for characterizing the magnetic properties of materials comprising fine (micron- or nano-scale) magnetic particles. FORC measurements and analysis have long been the standard protocol used by geophysicists and earth and planetary scientists investigating the magnetic properties of rocks, soils, and sediments. FORC can distinguish between single-domain, multi-domain, and pseudo single-domain behavior, and it can distinguish between different magnetic mineral species [1]. More recently, FORC has been applied to a wider array of magnetic material systems because it yields information regarding magnetic interactions and coercivity distributions that cannot be obtained from major hysteresis loop measurements alone. In this paper, we will discuss this technique and present high-temperature FORC results for two magnetic nanoparticle materials: CoFe nanoparticles dispersed in a SiO2 matrix, and FeCo-based nanocrystalline amorphous/nanocomposites.

Gold/albumin core/shell nanoparticles (Au/AlbNPs) was prepared by a novel aggregation/crosslinking technique and characterized by several spectroscopic and microscopy methods. Albumin, in presence of gold nanoparticles (AuNPs), is aggregated by the addition of ethanol and further stabilized by radiation-induced crosslinking using a 60Co source. Nanoconstructs are characterized to determine size, morphology and optical characteristics. The Au/AlbNPs were prepared in different ethanol and albumins concentrations. Results showed that it is possible to obtain Au/AlbNPs using ethanol 30 %v/v, albumin in different concentrations and an irradiation dose of 10 kGy. Au/AlbNP plasmon peak shifted to 530 nm, keeping the typical plasmon peak shape. The size of Au/AlbNPs is approximately double respect to the naked AuNPs and they show core/shell type morphology. The main amide peaks of albumin in FTIR spectrum can be found in the spectrum of nanoconstructs.

In this work it was evaluated the bactericidal effect of silver and silver-gold nanoparticles coated with silicon dioxide on Xanthomonas fragariae. Nanoparticles were synthesized by combining laser ablation and chemical synthesis techniques. Irradiating the samples at the same wavelength where nanoparticles exhibit its maximum absorbance is possible to photo induce the bactericidal effect by detonating the surface plasmon resonance. The results showed that the minimum bactericidal concentration (MBC) of silver nanoparticles was 16 μM (referred to [AgNO3]) and for silver-gold nanoparticles were 32 μM (referred to [AgNO3-HAuCl4]) at 60 minutes of irradiation.

Nanofibrous mats of poly ε-caprolactone (PCL) were fabricated by electrospinning. The nanofiber structures were investigated and characterized by scanning electron microscope, differential scanning calorimetry, thermogravimetric analysis, dynamic mechanical analysis, static water-contact-angle analysis and mechanical properties. The results showed that the nanofibrous PCL is an ideal biopolymer for cell adhesion, owing to its biocompatibility, biodegradability, structural stability and mechanical properties. Differential scanning calorimetry results showed that the fibrous structure of PCL does not alter its crystallinity. Studies of the mechanical properties, wettability and degradability showed that the structure of the electrospun PCL improved the tensile modulus, tensile strength, wettability and biodegradability of the nanotemplates. To evaluate the nanofibrous structure of PCL on cell adhesion, osteoblasts cells were seeded on these templates. The results showed that both adhesion and proliferation of the cells is viable on these electrospun PCL membranes. Thus electrospinning is a relatively inexpensive and scalable manufacturing technique for submicron to nanometer diameter fibers, which can be of interest in the commodity industry.

In this research, zinc chloride has been used as precursor and zinc oxide nanostructures have been synthesized by Sol-Gel process, using deionized water and 2-propanol as solvents in order to evaluate their influence on the final materials and their properties. Thin films of synthesized samples were deposited on glass substrates by the dipping method. The structure and morphology of crystals were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) respectively. The electrical response of the samples to CO was investigated at different operating temperatures and sensitivity curves are presented for samples synthesized in water and 2-propanol (IsOH) solvents. The SEM analysis revealed that ZnO thin films have yielded to different morphologies depending on the solvent, and material was found on the non-immersed side of the substrate attributable to migration during the dip-coating process. XRD analysis shows that the samples present the ZnO wurtzite structure. In EDS analysis it was found the presence of chlorine on the sample, opening the possibility the presence of zinc oxychloride.

Gas monitoring is a relevant activity for industrial and domestic applications due to usage of dangerous gases as methane, which has been increasingly used as domestic and industrial fuel. In this field of research, metallic oxides such as SnO2, ZnO and Fe2O3 have been widely studied, but we are far from reaching the total understanding of all the parameters that can be varied; in order to improve the gas sensing properties of the metallic oxides. In this work, we present the change of properties derived from using different solvents during the preparation of SnO2 nanoparticles via the sol-gel process. The nanoparticles suspended in two different solvents were deposited on glass substrates by the dip-coating method. The addition of Sb as a dopant was studied at two different Sb:Sn ratios of 1:99 and 1:2. SEM showed differences in the nanostructured topology of the samples and EDS analysis was performed to determine the elemental composition of the samples and the ratios of doping. XRD spectroscopy was used to determine the phase of the materials and the crystallite size. Measurements of the electric response of the coatings to methane, under controlled conditions at different temperatures, were carried out and curves of sensitivity versus temperature were obtained.

The purpose of this research is to study the viability of photocatalytic water splitting using ASTM A792 Zn-Al-Fe commercial metallic sheets as substrates for electrodeposited and corroded electrodes. The nanostructures were synthesized in two different procedures: via electrodeposition of migrating species from one electrode to another and from the remaining materials after corrosion of electrodes during electrodeposition, both procedures were done immersing the metallic electrodes in FeCl3 salts dissolved in water as cell electrolyte. The released or remaining Zinc-Aluminum-Iron can be used for the construction of nanostructures or as co-catalyst on the coating over the substrate. Actual EDS-SEM data reveals incorporation of Zinc on dendrite-like structures with traces of Al-Fe due to material release and further electrodeposition on working electrode, meanwhile, dendrite-like structures with an increased amount of Iron were obtained from the corrosion in the auxiliary electrode. Finally, samples were tested with lineal voltammetry to measure the photocurrent activity as indicator of photocatalytic viability for water splitting, obtaining an improvement of 31 mA/cm2 over natural photovoltaic current generation of substrates with higher Zinc concentrations under UV-Visible radiation.

Electrochemical Impedance Spectroscopy (EIS), is a confirmed tool for investigation of electrode/electrolyte interfaces and surface-modified electrodes. In the present work, we apply this approaching way to obtain a deeper insight into the electrochemical oxidation mechanism of the glucose in alkaline media. We studied the EIS response of gold nanoparticles embedded in carbon paste and use it as an electrode for the electro-oxidation of glucose. The results were compared with those of a polycrystalline gold electrode. In order to determine the polarization potentials for EIS tests, cyclic voltammetry is first conducted in 0.3 M KOH with 10 mM glucose, recorded at a scan rate of 1 mVs-1. Three polarization potentials were chosen, corresponding to: the open circuit potential (OCP), glucose oxidation and gold oxide formation respectively.

TiO2 nanotubular structures were fabricated on Ti polished and unpolished foils exposed to H2O-Glycerol (50-50Vol.%)+0.27 M NH4F at 20V. The obtained TiO2 nanostructures were analyzed by SEM obtaining the morphological characterization, from which the roughness factors were calculated. Crystalline phases of both TiO2 nanotubular films were obtained by XRD after annealing at 450 °C and 600 °C for 2 h. The electrochemical stability of the TiO2 nanotubular films was obtained from the potentiodynamic polarization curves (PC) and the linear polarization resistance (Lpr) techniques, exposing the samples in 1M Na2SO4 + H2SO4 solution (pH = 3.2), such pH is in accordance with the acidic wastewater containing sulfur compounds coming from the industries or acid waters of the aquifers, which have been contaminated from the volcanoes nearby. It was concluded that the electrochemical stability of the crystallized nanotubular films is improved with the increase of the annealing temperature of the amorphous TiO2 arrays, which is associated to the higher composition of anatase and rutile, observing that the major amount of rutile improved the corrosion performance. The photoelectrochemical measurements were carried out in 0.5 M Na2SO4 solution using an 8 W UV lamp at a λ= 365 nm, whose results were recorded at zero bias during 10 min under darkness and illumination intervals of 1 min each. The obtained results were in agreement with the necessary features for being used in photocatalytic water remediation.

TiO2 nanotubular structures were formed on titanium foils through anodic oxidation using an electrolyte of Ethyleneglycol-H2O (97:3 Vol %)+0.25 M NH4F at a constant voltage of 60V. The anodized samples were analyzed in a FE-SEM obtaining the geometric parameters of the nanotubular arrays. The diameter and the length of the nanotubes were 112 nm and 65µm |respectively, whereas the wall thickness was 44 nm. Crystalline phase of TiO2 nanotubular films (TNTF) were determined by XRD after annealing at 500°C for 2 h, resulting high intensity peaks of anatase and low intensity peaks of rutile. Then, the crystallized samples were characterized from an optical, photoelectrochemical and photocatalytic point of view. The photoelectrochemical measurements were carried out in 0.5 M Na2SO4 solution using an 8 W UV lamp at a λ= 365 nm, which results were recorded at 0 bias during 10 min under darkness and illumination intervals of 1 min each. Photocatalytic performance of the TNTF was explored with a 10 mg/L methyl orange solution using an UV light at a wavelength of 365 nm. The changes in the concentration of the MO solution was determined from the calibration curve determined from the absorption spectra at different concentrations of MO (from 0.1 mg/L to 20 mg/L). It was observed an efficiency yield of 99.8% in the photocatalytic performance in presence of the TNTF.

Based on the nature of the links and interactions existing at the hybrid interface, hybrid materials can be broadly classified in two main designations: a) Hybrid compounds Class I, that include all systems with electrostatic forces, hydrogen bonding or Van der Waals interactions and b) Hybrid compounds Class II, showing that the inorganic and organic components are linked through strong covalent or ionic-covalent bonds. The physico–chemical properties of nanostructured copolymer acrylates based on butyl acrylate (BA), methyl methacrylate (MMA) and acrylic acid (AA) has been investigated employing un-modified SiO2 (Class I) and modified SiO2 particles (Class II) using 3-(trimethoxysilyl) propyl methacrylate (MPS) as compatibilizing agent. The synthesis was carried out using seeded batch emulsion polymerization system. Metastable nanostructured emulsions containing 1 wt% nanoparticles were obtained. Films casted from the in-situ nanostructured latex exhibited excellent optical transparency suggesting good nanoparticles dispersion. However, the mechanical properties showed by SiO2-MPS nanocomposite, are better than the Class I hybrid compounds. Therefore, SiO2-MPS surface treatment prior to polymerization enhances the physical properties of copolymer BA-MMA-AA film. The mass loss derivative traces for the polyacrylic nanocomposites and the neat polymer obtained by thermogravimetric analysis showed that the onset temperature for thermal decomposition was shifted towards a higher temperature than the neat polyacrylic, indicating the enhancement of thermal stability of the un-modified SiO2 nanocomposite. However, there is a decrease of 40°C in the decomposition temperature for the modified polyacrylic nanocomposite. The results obtained so far have shown that weak Van der Waals and H-bonding interactions may be sufficient to enable improvement of the physical properties of the acrylate nanocomposites.

The synthesis of inorganic/organic nanocomposite systems, well known as hybrid materials, represents a new class of polymeric materials, which combine properties of inorganic particles, such as barrier, optical, catalytic and conductive properties, among others, with flexibility and transparency of the organic polymer matrix, being easily processable. They could be applied in a diversity of areas such as textiles, inks, adhesion, biomaterials, paints, adhesives, and electronics [1-2]. Within the inorganic materials, silica nanoparticles which present excellent properties, such as high mechanical strength, thermal and chemical stability, and high surface area, have been widely incorporated into a polymer matrix to prepare polymer/silica hybrid materials [3-4]. It is reported that the quantity and the dispersion of nano-SiO2 in the polymer matrix have a real effect on the properties of the final materials [5-6].

In this work, hybrid silica/poly(butyl acrylate-methyl methacrylate-acrylic acid) (SiO2/P(BA-MMA-AA)) were synthesized via in situ semi-batch emulsion polymerization. The results showed that this process was produced with high monomer conversion and low formation of agglomerates. The thermomechanical behavior of the films obtained from latexes was characterized by using thermogravimetric analysis, differential scanning calorimetry, and tensile test. The nanocomposite films displays significantly improved mechanical and thermal properties over its pure polymer film, and also presents almost the same high transparency.

The field of composites materials has evolved from the use of traditional fillers (e.g. carbon and glass fibers) to nanoscale fillers that add unique and often multifunctional properties to the neat polymer. Because nanoparticles have extremely high surface to volume ratios, that alter the mobility of polymer chains near their interfaces, even a small addition of nanoparticles. These components have the potential to drastically transform the properties of the host polymers. While the last decade has observed several advances in the field of nanocomposites, some recent reviews have made it clear that definitive structure-property relationships are insufficient in the literature. The influence of inorganic TiO2 nanoparticles on the dynamic mechanical properties and microstructure of copolymer based on Butyl acrylate - Methyl methacrylate - Acrylic Acid has been investigated. The mechanical relaxations of the reinforced copolymer/TiO2 composites were studied under tension mode. Addition of TiO2 nanoparticles to acrylic copolymer produced a decrease in the glass transition temperature. Dynamic mechanical analysis (DMA) showed that the local motions associated with the alpha-transition (40°C) are enhanced as the frequency of oscillation increases, i.e. the tan d maximum increases at higher frequencies. The addition of TiO2 nanoparticles reduces significantly the strength of the alpha-transition. Thus, the cooperative molecular motions involving segments of the molecular chains associated with the alpha-transition were compromised by the presence of TiO2 nanoparticles resulting in a decrement of the storage modulus.

The incorporation of layered nano-silicates in polymer matrix greatly enhances the properties of the polymer. At present, there are many applications of polymer nanocomposites including coatings and architectural, they are also parts of automotive and construction industry among others. The acrylics employed at the present study were based on butyl acrylate (BA), styrene (STY), and methacrylic acid (MAA), and the nano-clay was Na-montomorillonite (MMT). The MMT clay was added to the polymer, which is the mixing matrix in a physical state solution called blend. Furthermore, their mechanical, thermal and wettability of especially prepared acrylic montmorillonite (MMT) nanocomposites were performed. By increasing the MMT in the polymer matrix concentration the Young’s modulus tends to increase it by an order of magnitude. However, by Differential Scanning Calorimetry (DSC), the thermograms show an increase in the glass transition temperature of nanocomposites for all weight percentages of MMT. Also, the wetting angle was determined, in order to know how much water is retained on the surface of the nanocomposite; the results showed that by increasing the particle of nano clay in the polymer matrix will induce a hydrophobic property to the nanocomposite.

Nanocrystalline MnxZn1-xFe2O4 with the varying concentration of Mn (x= 0.25, 0.50) have been synthesized by citrate route method. The effect of annealing temperature on structural and magnetic properties of as-synthesized materials was studied. The X-ray diffraction (XRD) analysis revealed the improved crystallinity and purity of the samples at high temperature annealing. Also, the increase in the annealing temperature yielded nanocrystals with bigger crystallite size. The samples annealed at higher temperature were analyzed by TEM which showed the formation of irregular polycrystalline particles with average size in the range of 150-180 nm. The magnetic measurements were taken using vibrating sample magnetometer and displayed the superparamagnetic behavior of the prepared materials. Also, the increase in magnetization was observed with Mn substitution.

Magnetic nanoparticles were obtained by chemical coprecipitation technique from aqueous solutions of iron salts, the synthesis was carried out in an alkaline medium, obtaining magnetic nanoparticles of around 2-10 nm in size. The nanoparticles obtained were stabilized with polyvinylpirrolidone (PVP), the particle size was measured by transmission electron microscopy (TEM), the crystal structure of the magnetic nanoparticles obtained was verified by X-ray diffraction (DRX). The chemical composition of the nanoparticles powder was investigated using electron scanning microscope with energy dispersive X-ray spectroscopy (EDX) equipment. Optical properties as absorption was studied by UV-Vis spectroscopy.

In the present investigation, nanostructured ceramic HfN coatings were deposited onto silicon (100) wafer by magnetron sputtering DC method, from a metallic Hf target. The deposition process followed by a similar pattern as the multilayer film deposition, using cycles with the nitrogen gas turned on for 90 s and turned off for 15 s; four sets of samples were obtained using 5, 10, 15 and 20 cycles. The X ray diffraction (XRD) identified the presence of two different cubic crystalline phases of HfN, corroborated by Rietveld analysis. The Vickers hardness test showed that the hardness values increases with more cycles, due to a higher compressive stress evaluated by Stoney formula. All samples were investigated with no visible fracture until 10 grf for the 5 cycles sample; however, no fractures were visible at all for the 15 and 20 cycle samples for that given load, instead fractures started to appear at 25grf for the 10 and 15 cycles coating. Eventually it is distinguished that, the thickness and morphology of the coatings were measured by field emission scanning electron microscopy FE-SEM. As well as, the thickness increased from 0.4 µm to almost 1.33 µm as the number of cycles also increased, where we can observe the formation of columnar growth, moreover it is possible to distinguish the formation of two different clusters which might be related to different phases.

Graphene is a two dimensional material of special interest due to its unusual electronic, mechanical, chemical, optical among other properties, which suggest a wide range of applications in optoelectronics, computer, ecology, etc. The study of the optical properties of graphene is important due to its potential applications such as ultrafast photonics, optical filters, composite materials, photovoltaics and energy storage device. In this work we study the transmission and absorption properties of a quasi-regular multilayer dielectric-graphene-dielectric system. The multilayer structure is built on the quasi-regular Period-Doubling (PD) sequence. The optical response of graphene takes into account intra-band and inter-band transitions. We use the transfer-matrix method to calculate the transmission and absorption spectra. It is obtained a strong dependence on the number of layers in the system, the width of dielectric media and the optical contrast. Furthermore, we calculate the spectra for both transverse magnetic (TM) and transverse electric (TE) polarization in the infrared region.