Selene Sepulveda-Guzman

Use of Silica Tubes as Nanocontainers for Corrosion Inhibitor Storage

A new alkyd paint anticorrosion smart coating was developed by using silica nanoparticles as corrosion inhibitor nanocontainers. Silica particles were mixed with the paint at different concentrations to study their performance and ensure their free transportation to the damaged metal. The filling up of silica particles was done preparing three solutions: distilled water, acetone, and a mixture of both, with Fe(NO3)3 and silica particles immersed in each of the solutions to adsorb the inhibitor. Acetone solution was the best alternative determined by weight gain analysis made with the inhibitor adsorbed in silica nanocontainers. Steel samples were painted with inhibitor silica nanocontainer coatings and immersed in an aqueous solution of 3% sodium chloride. Polarization curves and electrochemical noise techniques were used to evaluate the corrosion inhibitor system behavior. Good performance was obtained in comparison with samples without inhibitor nanocontainer coating.

Immobilization of TiO2 nanoparticles on montmorillonite clay and its effect on the morphology of natural rubber nanocomposites

Natural rubber/organoclay/titanium dioxide nanocomposites were obtained via mechanical blending using rubber latex, organically modified montmorillonite clay (cloisite 30B) and titanium dioxide (TiO2). Glycerol was utilized as a dispersant for the inorganic components. Scanning electron microscopy analysis shows that TiO2 nanoparticles were deposited on the clay surface and that the clay–TiO2 combination was homogeneously dispersed on the natural rubber. The high aspect ratio and the polar character of the clay layers allowed interactions with individual nanoparticles of TiO2. The X-ray diffraction patterns reveal an increment of the crystalline character of the NR/C30B/TiO2 nanocomposites as a consequence of the nanoscale dispersion of the TiO2 particles. Infrared Spectroscopy spectra indicate compatibility between natural rubber and glycerol due to the formation of hydrogen bonds. A mechanism in particle–natural rubber compatibility, in which glycerol is involved, is proposed. However, nanoscale dispersion was largely dependent on the clay–TiO2 interactions. This work proposes an easy method to immobilize TiO2 nanoparticles on clay layers, which allows their dispersion in polymers. Nanocomposites obtained by this method can be used for supports of photocatalyst molecules.

Enhancement of electrochemical properties on TiO2/carbon nanofibers by electrospinning process

In the present work, we report the preparation of TiO2–carbon/carbon dual nanofibers using an electrospinning technique. The dual nanofibers were synthesized using a modified side-by-side spinneret, which allowed the fabrication of the desired dual nanofiber architecture in a one-step process. A subsequent heat treatment permitted the control on the crystal structure of the synthesized dual nanofibers. Scanning electron microscopy and transmission electron microscopy results confirmed the continuity and duality of the obtained nanofibers. The difference in composition between the fibers composing the dual fibers was clearly observed by energy dispersive X-ray spectroscopy. The effect of heat treatment on crystallinity was evident on the results obtained from the X-ray diffraction and selected area electron diffraction studies; where, depending on the heat treatment conditions, clear signals for anatase and rutile phases of TiO2 were observed. Electrochemical studies suggest an improvement on the conduction properties of TiO2–carbon/carbon dual nanofibers compared to single TiO2–carbon nanofibers, attributed to the carbon nanofiber contribution attached to the TiO2 nanofibers. Based on the morphological and structural features of this novel nanostructured material, and to the electrochemical performance observed, it has a wide range of potential applications.

Iron Oxide Nanoparticles Obtained from a Fe(II) - Chitosan Polymer Film

In this work, iron oxide nanoparticles (~5 nm) embedded in a chitosan polymer film, were synthesized. In order to obtain this nanostructured material, firstly a homogenous film of Fe(II)-chitosan was prepared. The resulting composite film has a thickness of ~140μm. Iron oxide nanoparticles were in-situ synthesized by treating the composite film with H2O2 under alkaline conditions. The morphological analysis by Transmission Electron Microscopy (TEM) shows the nanoparticles were embedded and stabilized in chitosan polymer film. The magnetic behavior was studied by magnetization measurements. The magnetization curves at room temperature showed that iron oxide nanoparticles have a superparamagnetic behavior.

Synthesis and Properties of Monometallic and Bimetallic Silver and Gold Nanoparticles

ABSTRACT Au, Ag monometallic, and Au-Ag bimetallic nanoparticles have been synthesized by two different methods, the first one was the polyol method and stabilized with poly(vinylpyrrolidone) (PVP), modifying the temperature of synthesis. Interesting structure changes were observed in the nanoparticles as the temperature was varied. The second method consisted of successive reduction of metal salts with ascorbic acid on premade seeds in the presence of a cationic surfactant, cetyltrimethylammonium bromide (CTAB). In the first method at low temperatures, no bimetallic nanoparticles were detected, but as the temperature increased bimetallic nanoparticles started to appear, commonly obtaining core-shell nanoparticles, always covered by the polymer. This originates the modification of the optical response of the system in the ultraviolet (UV)-visible region. An absorption peak centered at 520 nm at low temperatures was observed (100–110°C); at higher temperatures (130–170°C) there were nondetectable absorptio...

Mesoporous titania nanofibers by solution blow spinning

Fast and large-scale production of mesoporous titania nanofibers was achieved by solution blow spinning. The blow spinning setup provides a method to prepare titania nanofibers in a safe and scalable way without using a high-voltage electric field. Titania microstructure and porosity can be modified by adding a suitable template, such as pluronic polymers. The blow spun titania nanofibers had a good performance on the photocatalytic degradation of tetracycline and could be easily removed from the tetracycline aqueous solution due to their large aspect ratio. Solution blow spinning method has a great potential for the large-scale production of titania nanofibers with good photocatalytic properties.Graphical Abstract

Synthesis and Properties of Tin Sulfide Thin Films from Nanocolloids Prepared by Pulsed Laser Ablation in Liquid

Tin sulfide (SnS) nanoparticles were synthesized by pulsed laser ablation in liquid (PLAL) technique using an Nd:YAG laser operated at 532 nm. SnS thin films were deposited by spraying the colloidal suspension onto the heated substrates. The influence of different liquid media (dimethyl formamide and isopropyl alcohol) on the thin film properties were studied. Morphology, crystalline structure, and chemical composition of the nanoparticles were identified using transmission electron microscopy with energy dispersive X-ray analysis. The crystalline structure of the thin films was analyzed by using grazing incidence X-ray diffraction, and the chemical states by X-ray photoelectron spectroscopy. Scanning electron microscopy was employed for the morphological analysis of the thin films. Annealing the films at 380 °C improved the crystallinity of the films exhibiting a layered morphology, which may be useful in optoelectronic and sensing applications. Cyclic voltammetry studies showed that the films have good electrochemical properties.

Microstructure, vibrational and visible emission properties of low frequency ultrasound (42 kHz) assisted ZnO nanostructures

Size and shape tuneable ZnO nanostructures were prepared by a low frequency ultrasound (42 kHz) route using various organic solvents as the reaction media. The crystalline nature, lattice parameters and microstructural parameters such as microstrain, stress and energy density of the prepared ZnO nanostructures were revealed through X-ray diffraction (XRD) analysis. The organic solvents influenced the size and morphology of the ZnO nanostructures, and interesting morphological changes involving a spherical to triangular shaped transition were observed. The visible emission properties and lattice vibrational characteristics of the nanostructures were drastically modified by the changes in size and shape. Raman spectral measurements revealed the presence of multiphonon processes in the ZnO nanostructures. The intensity of the visible emission band was found to vary with the size and morphology of the structures. The strongest visible emission band corresponded to the structure with the largest surface/volume ratio and could be attributed to surface oxygen vacancies. The control over the size and morphology of ZnO nanostructures has been presented as a means of determining the intensity of the visible emission band.

The Effect of a Chemically Modified Graphene in Water Based Corrosion Coating.

Research in the development of new corrosion coatings is of major economic importance. Recently, nanocomposite based corrosion coatings containing nanostructures limiting diffusion of aggressive corrosion species, have been reported. Graphene is a one atom thickness sheet, formed by a hexagonal arrangement of carbon atoms with excellent thermal, electric and mechanical properties. This work investigates the use of chemically modified graphene (CMG) as an additive in commercial vinylic corrosion coatings. It is expected as the diffusion of aggressive species diminishes through the coating from the presence of graphene, therefore the coating corrosion protection behaviour improves and so the metal damage reduces. The CMG was prepared by graphite oxide thermal self reduction. Afterwards a coating was formulated based on a vinyl acrylic paint and 1, 3, 5 and 10% wt CMG mixture. Ferric nitrate was added as an inhibitor. The coating was then applied to 1045 carbon steel sheet and dried at room temperature. Electrochemical evaluation was performed in 3% NaCl solution and coatings were evaluated electrochemically and characterized using electron scanning microscopy (SEM) to observe their morphology.

Eco-friendly isolation of cellulose nanoplatelets through oxidation under mild conditions

Agave is recognized as a low recalcitrant material, which makes it a potential source to obtain nanocellulose. Aqueous dispersions (in water, H2O2, H2O2/H2SO4) of agave powder were heated at 120°C under vapor pressure (1kg/cm2). The resultant materials were observed with an optical microscope (OM), a laser scanning microscope (LSM) to obtain the thickness measurement and a scanning electron microscope (SEM) to observe morphology. Raman spectroscopy, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) were used to obtain the chemical structure. Cellulose nanoplatelets (CNPs) from Agave salmiana were successfully isolated under mild conditions. Physicochemical analysis indicates that lignin was removed in a single step oxidation with hydrogen peroxide in presence of sulfuric acid at low concentration (0.17M). The CNPs images revealed the presence of entangled cellulose nanofibrils (Ø≈14nm) along the nanoplatelets (thickness ≈80nm).