J. G. Bañuelos

National Autonomous University of Mexico, Ciudad de México, The Federal District, Mexico

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Publications (19)21.45 Total impact

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    ABSTRACT: In the present work, oxalic amorphous porous anodic alumina membranes (AAM) with highly ordered porous arrays and average nanometric porous dimensions of 70 nm in diameter and 37 microns in depth (nanotubes) were prepared and successfully used as hosting matrix for C60 and C70 fullerene compounds. Atomic force microscopy (AFM) studies were performed on the hybrid samples in order to explore surface morphology and optimal insertion of these molecular systems into the AAM environment. The cubic nonlinear optical (NLO) properties, such as nonlinear refraction and absorption of the hybrid samples were studied via the Z-Scan technique in order to evaluate their NLO-performance. Hybrid AAM with fullerene compounds have shown outstanding NLO-activity with positive NLO-refractive coefficients.
    Proc SPIE 08/2011;
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    ABSTRACT: Phthalocyanines (Pc) based compounds having central metallic atoms of Ni were successfully embedded in mesoporous silica gels via a catalyst-free sol-gel (sonogel) process in order to fabricate optically active solid-state hybrid glasses in both bulk and thin film formats at different dopant concentrations. The organic-inorganic hybrid composites obtained at room temperature processing showed stable mechanical performance, controllable geometrical shapes, good transparency and homogeneity suitable for linear and nonlinear optical (NLO) characterizations. Hybrid samples were studied via the NLO third-harmonic generation (THG) technique. AFM studies, epi-microscopy surface evaluation, refractive-index measurements and UV-Vis spectroscopy studies were also performed in selected bulk and film samples. The morphological and spectroscopic results showed a homogeneous dispersion of the organometallic compounds within the highly pure SiO2-sonogel network. Moreover, Brewster's angle measurements have demonstrated the feasibility of tuning the refractive index of the samples by varying the chromophore dopant concentration. Additionally, the electronic absorption spectra showed band shifts in the two characteristic bands of the organometallic compound within sonogel environment, which evidence the formation of molecular H-aggregates for the developed hybrids and the consequent modifications of their optical properties. Finally, THG measurements in hybrid film samples exhibited an important NLO activity. We conclude that the optical effects of these composites can be tuned as function of the nickel-Pc concentration and that the sonogel matrix mainly acts as an inert protective shell, giving stable mechanical and thermal properties to the guest dopant compounds.
    22nd Congress of the International Commission for Optics: Light for the Development of the World; 01/2011
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    ABSTRACT: Amorphous anodic alumina membranes (AAM) comprising highly ordered nanometric porous arrays (porous anodic aluminas: PAA) with 1D-nanotube dimensions of ∼75nm in diameter and 45microns in depth were successfully prepared and used as nanostructured host networks for different functionalized octupolar chromophores (named here Oct-(n)). Atomic force microscopy (AFM) studies performed on the developed hybrid systems confirmed a homogeneous insertion of these organic molecules into the PAA nanotube-arrays. Samples with high structural quality were selected for several photophysical characterizations: Comprehensive X-ray diffraction (XRD) and optical spectroscopic characterizations performed according to UV–vis absorption, photoluminescent (PL) and Raman measurements revealed the structural and optical performance of these molecules within the PAA-confinement. Since the implemented optical chromophores were specifically functionalized for nonlinear optical (NLO) applications, the obtained Oct-(n)/PAA-based amorphous hybrids were also characterized according to cubic NLO-techniques such as third harmonic generation (THG) and the Z-Scan method. PAA-confined octupolar chromophores have shown interesting linear and NLO optical properties which have not yet been intensively investigated in bulk hybrid systems; hence, the obtained hybrid nanostructures represent a promising field of investigation in the route to functional octupolar-based materials, where different self-assembled molecular structures may be formed, giving rise to enhanced linear and NLO-properties.
    Materials Science and Engineering B-advanced Functional Solid-state Materials. 01/2011; 176(18):1479-1496.
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    ABSTRACT: The catalyst-free sonogel route was implemented to fabricate highly pure, optically active, hybrid azo-dye/SiO2-based spin-coated thin films deposited onto ITO-covered glass substrates. The implemented azo-dyes exhibit a push-pull structure; thus chromophore electrical poling was performed in order to explore their quadratic nonlinear optical (NLO) performance and the role of the SiO2 matrix for allowing molecular alignment within the sonogel host network. Morphological and optical characterizations were performed to the film samples according to atomic force microscopy (AFM), ultraviolet-visible (UV-Vis) spectroscopy and the Maker-fringe technique. Regardless of absence of a high glass transition temperature (Tg) in the studied monomeric liquid crystalline azo-dyes, some hybrid films displayed stable NLO activity such as second harmonic generation (SHG). Results show that the chromophores were homogeneously embedded within the SiO2 sonogel network, where the guest-host molecular and mechanical interactions permitted a stable monomeric electrical alignment in this kind of environment.
    Journal of Modern Optics 01/2010; 57(1):65-73. · 1.16 Impact Factor
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    ABSTRACT: SiO2-based bulk and film sol-gel hybrid materials were prepared with a family of novel liquid crystalline (LC) amphiphilic azo-dyes bearing oligo(ethylene glycol) spacers (named here RED-PEG-n, n = 2, 3, 4, 6). The catalyst-free-sonogel route was implemented to produce optically active hybrid monoliths and spin-coated films with these materials. Comprehensive morphological, thermal, photo-acoustic and spectroscopic sample characterizations were performed in order to elucidate the physical properties of these novel compounds within the sonogel environment. Film samples were also studied via the nonlinear optical (NLO) second harmonic generation (SHG)-Maker fringes technique. Results show that the chromophores were homogeneously embedded within the highly pure SiO2-sonogel network, showing a clear thermotropic mesogenic behavior. The push-pull structure of the implemented azo-dyes allowed effective electrically-induced monomeric alignment within the sonogel confinement; thus, stable quadratic NLO-SHG-activity in the organic-inorganic film samples was achieved despite the lack of glass transition temperature (Tg) of the guest LC-compounds
    Journal of Sol-Gel Science and Technology 01/2010; 56(1):7-18. · 1.66 Impact Factor
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    ABSTRACT: The shape and size of nanostructures formed by the precipitation of europium ions in KBr single crystal has been analyzed using optical absorption (OA), luminescence (LM) and atomic force microscopy (AFM). This work reports a relationship between the emission band peak (EBP) and the nanostructure size. The shift of the t2g absorption band towards longer wavelengths and a larger 10 Dq value reveals the growth of the nanostructures (NS). The AFM images show that the precipitates have circular shape and ∼ 20 to 400 nm diameter according to the position of EBP at around 428–433 nm. The AFM technique allowed us to relate the shape and size of the nanostructures with our previous research by OA and LM. To our knowledge, the topography of europium ions forming NS of different diameter is observed for first time.
    Solid State Communications 03/2009; 149(11):445-447. · 1.53 Impact Factor
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    ABSTRACT: The EuBr2 nanostructures self-assembled (SA) in ring form are presented in this letter. The atomic force microscopy (AFM) images show rings of ~190 to 2500 nm diameter formed on [100] surface. The sample optical response with rings displays an emission band peak (EBP) at 435 nm. The europium absorption bands reveal structural changes and shift toward infraredwavelength. Theemission bandwidth of EuBr2 nanostructures in ring form is narrower than dispersed nanostructures of similar size. To our knowledge, is the first time that there is clear evidence of the arrangement in ring form in the KBr:Eu2+ crystal samples.
    Materials Letters 01/2009; 63(no. 5):554-556. · 2.27 Impact Factor
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    José Gualupe Bañuelos, Elena V. Basiuk, José Manuel Saniger-Blesa
    Revista Mexicana de Física, ISSN 0035-001X, Vol. 49, Nº. 4, 2003, pags. 310-316. 01/2009;
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    ABSTRACT: Chemically sprayed fluorine-indium-doped zinc oxide thin films (ZnO:F:In) were deposited on glass substrates. A mixture of zinc pentanedionate, indium sulfate, and fluoride acid was used in the starting solution. The influence of both the dopant concentration in the starting solution and the substrate temperature on the transport, morphological, linear, and nonlinear optical (NLO) properties were fully characterized with atomic force microscopy (AFM), scanning-electron microscopy (SEM), UV-VIS, and photoluminescence (PL) spectroscopies, and the second-harmonic generation (SHG) technique, respectively. A decrease in the resistivity was observed for increasing substrate temperatures, reaching a minimum value of 1.2 × 10−2 Ω cm for samples deposited at 500°C. The surface morphology was also dependent on the dopant concentration in the starting solution and on the substrate temperature. The X-ray diffraction (XRD) patterns revealed that the ZnO:F:In thin solid films are polycrystalline in nature fitting with a hexagonal wurtize type and showing (002) preferential growth for all of the studied samples. The optical transmittance of these films was found to be higher than 80%, from which the optical band gap of these samples was determined. Finally, a clear dependence on the quadratic NLO properties of the developed semiconducting ZnO:F:In thin films with the substrate temperatures was established, where huge x (2)-NLO coefficients on the order of x 33(2) = 37 pm V−1 were measured for high substrate temperatures. PACS numbers68.55.-a–68.55.Jk–81.10.Dn–42.65.-k
    Laser Physics 01/2008; 18(3):283-291. · 1.03 Impact Factor
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    ABSTRACT: Fullerene C60 films deposited by sublimation were irradiated with Kr-F laser in a wide fluence interval from 15 to 40 mJ/cm2. In situ photoacoustic analysis was applied to study the phase transformation during the irradiation. The results obtained were discussed in conjunction with atomic force microscopy (AFM) and Raman spectroscopy data. It was found that for a irradiation fluence interval from 22 to 30 mJ/cm2, 80% of C60 undergoes photopolymerization (presumably through 2 + 2 cycloaddition). For a laser energy higher than 30 mJ/cm2, a new amorphous carbon phase forms, having a large content of diamond-like, tetra-amorphous carbon (ta-C).
    Journal of Nanoscience and Nanotechnology 03/2007; 7(4-5):1414-8. · 1.15 Impact Factor
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    ABSTRACT: The effects of different components on the performance of a selected polymer inclusion membrane (PIM) system developed for copper transport were assessed by means of different analytical techniques. Copper(II) transport data, thermal analysis, transmission infrared mapping microspectroscopy (TIMM) and AFM were used to characterize chemical and physical behavior of PIMs with different compositions. The prepared membranes, made using cellulose triacetate (CTA) as support, tris(2-n-butoxyethyl) phosphate (TBEP) as plasticizer, together with an additive (ethanol), and LIX® 84-I, LIX® 984 or LIX® 54-100 as carrier, showed increasing copper(II) permeabilities in the order LIX® 54-100 < LIX® 984 < LIX® 84-I. Membrane permeabilities increased up to 2.6-fold in the strip solution side for LIX® 84-I PIMs cast with ethanol, and Cu(II) accumulation within the membrane was observed to vary with the amount of additive. The modifications of the transport properties of the PIMs were satisfactorily correlated with the distribution profiles of the membrane components (obtained by TIMM), glass transition temperatures, casting method and topographic structure of the films with the aid of a Teas graph implemented for PIM applications. From this graph it was possible to interpret the interactions between the different membrane components in a phenomenological way, thus contributing to improve the understanding of the role played by each one in the development of a more efficient PIM system for copper transport when using LIX® reagents as carriers.
    Materials Science and Engineering B 10/2006; 434 (1-2):30-38. · 1.85 Impact Factor
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    ABSTRACT: The synthesis of sol-gel materials induced by ultrasonic action (sonolysis) is implemented as an alternative method for the fabrication of highly pure organic-inorganic composites with good monolithic and optical properties. A newly synthesized liquid crystalline mesogen (named here RED-PEGM-7) was introduced as dopant specie within the SiO2 matrix in order to create an active nonlinear optical hybrid material at room temperature. A comparative characterization of the structural properties between a pure reference sample and several doped composites was performed by X-ray diffraction (XRD) and atomic force microscopy (AFM); where, an optimal dissolution concentration of tetraethoxysilane (TEOS) and the liquid crystalline (LC) mesogen, to obtain good mechanical and nonlinear optical properties in thin film layers has been found.
    Molecular Crystals and Liquid Crystals. 08/2006; 449(2006: pp. 161–177):161-177.
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    ABSTRACT: Chemically sprayed indium-doped zinc oxide thin films (ZnO:In) were deposited on glass substrates starting from zinc pentanedionate and indium sulfate. The influence of both the dopant concentration in the starting solution and the substrate temperature on the transport, morphology, composition, linear and nonlinear optical (NLO) properties of the ZnO:In thin films were studied. The structure of all the ZnO:In thin films was polycrystalline, and variation in the preferential growth with the indium content in the solution was observed: from an initial (002) growth in films with low In content, switching to a predominance of (101) planes for intermediate dopant regime, and finally turning to a (100) growth for heavily doped films. The crystallite size was found to decrease with doping concentration and range from 36 to 23 nm. The film composition and the dopant concentration were determined by Rutherford backscattering spectrometry; these results showed that the films are almost stoichiometric ZnO. The optimum deposition conditions leading to conductive and transparent ZnO:In thin films were also found. In this way a resistivity of 4 × 10−3 Ω cm and an average transmittance in the visible spectra of 85%, with a (101) preferential growth, were obtained in optimized ZnO:In thin films.
    Journal of Physics Condensed Matter 05/2006; 18(22):5105. · 2.22 Impact Factor
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    ABSTRACT: The synthesis of sol-gel materials induced by ultrasonic action (sonolysis) is implemented as an alternative method for the fabrication of highly pure organic-inorganic composites with good monolithic and optical properties. A newly synthesized liquid crystalline mesogen (named here RED-PEGM-7) was introduced as dopant specie within the SiO2 matrix in order to create an active nonlinear optical hybrid material at room temperature. A comparative characterization of the structural properties between a pure reference sample and several doped composites was performed by X-ray diffraction (XRD) and atomic force microscopy (AFM); where, an optimal dissolution concentration of tetraethoxysilane (TEOS) and the liquid crystalline (LC) mesogen, to obtain good mechanical and nonlinear optical properties in thin film layers has been found.
    Molecular Crystals and Liquid Crystals - MOL CRYST LIQUID CRYST. 01/2006; 449(1):161-177.
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    ABSTRACT: Comprehensive optical characterization of C60 films on semiconductor substrates has been performed by means of ellipsometry, Raman and photoluminescence spectroscopy. The films have been prepared by the sublimation of C60 in vacuum. The morphology of these films and the C60–substrate interaction were investigated by atomic force microscopy. Both flat and patterned wafers of Si, Ge, and InP have been used as substrates. It was found formerly that the strong interaction occurs between C60 molecules and Si surface, and the C60 films on patterned InP surface grow with grains arrayed in [011] and [101] perpendicular directions. Initial optical characterization was performed by means of ellipsometry to determine thickness and optical constants of the films. Raman spectra have been measured at room temperature under argon laser excitation. It was shown to be very useful for structural characterization and estimation of stress. Observed increase of Raman signal from patterned samples and its possible connection with surface enhanced Raman scattering effect are under discussion. Raman spectra and low temperature photoluminescence provide information on dimer formation and polymerization.
    Carbon 09/2004; 42, 5-6:1089-1093. · 6.16 Impact Factor
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    ABSTRACT: Ag/Fe and Cu/Fe bilayers were deposited onto Si substrates and irradiated at room temperature with 2MeV Cu and 2.5MeV Au ions in order to study the ion beam induced surface roughening. We have used contact atomic force microscopy (AFM) to study the surface topography and observed that film grains grow slowly, in a uniform way, but simultaneously, individual grains aggregate to each other to form complex structures. This suggests that two different mechanisms take place during ion bombardment contributing to surface roughening. One is a thermally activated mechanism, while the second is a non-uniform process that might be related with the fractal nature of ion bombardment. The former predominates at temperatures where surface defects are mobile across grain boundaries and produces uniform spherical grains, whereas the latter is always present and produces non-uniform structures that give evidence of fractal aggregation patterns. No roughness increase due to surface sputtering was observed.
    Applied Surface Science. 02/2003; 206(1-4):178-186.
  • J. G. Bañuelos, E. V. Basiuk, J. M. Saniger-Blesa
    Revista Mexicana de Fisica 01/2003; 49:310-316. · 0.35 Impact Factor
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    ABSTRACT: Titanium oxide films were deposited by the ultrasonic spray pyrolysis process using titanium oxide acetylacetonate (TAAc) as source material dissolved in pure methanol. As-deposited films show the anatase crystalline structure, while annealed samples at 850°C have the rutile phase. Rutherford backscattering measurements indicate that the deposited films are formed by stoichiometric TiO2 material. Root-mean-square (rms) roughness depends on the substrate temperature and on the annealing process. Refractive index has values of the order of 2.36 for as-deposited films and 2.698 for annealed films. This change is associated with the anatase to rutile phase change. IR analyses show well-defined absorption peaks located at 433 and 638cm−1 for anatase phase and peaks located at 419, 466, 499 and 678cm−1 for rutile phase. In general, the titanium oxide films show high optical transmission. The energy band gap calculated for the anatase phase is of the order of 3.4eV. The current density–electric field characteristics of MOS structures show current injection across the titanium oxide film even for low applied electric fields. However, electric breakdown was not observed for applied fields up to 5MVcm−1.
    Materials Chemistry and Physics 05/2002; 9486:1-7. · 2.07 Impact Factor
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    ABSTRACT: Resumen Para el apropiado depósito de diversos materiales en plantillas de alúmina porosa, es indispensable realizar un cuidadoso tratamiento y caracterización de las mismas, para obtener así un ensamble ordenado de estructuras 1D en el interior de sus poros. En este trabajo se presenta un seguimiento de las diferentes etapas a las que se somete el sustrato de aluminio y la membrana de alúmina porosa hasta que se encuentra preparada para el depósito electroquímico por CD de los nanoalambres. El estudio de las muestras a través de las diferentes etapas de su preparación se realiza fundamentalmente mediante microscopía de fuerza atómica (AFM). La configuración final de la plantilla conteniendo los nanoalambres metálicos es aplicable para la preparación de dispositivos de cátodos de emisión de campo. Abstract Careful preparation and characterization of porous alumina templates are necessary in order to obtain an appropriate deposit of different materials inside its ordered array of 1D pores. In this work an overview is presented of the different preparation steps of aluminum substrates and porous alumina membranes until they are ready for the DC electrochemical deposition of nanowires. The different steps of this study were followed by Atomic Force Microscopic (AFM). The alumina template-metallic nanowires system could be useful for the preparation of cathodic field emission devices.