Advanced search


Knowledge area




136 results, page 1 of 10

BIOSYNTHESIS OF SILVER NANOPARTICLES BY USING NOPAL EXTRACT AND THEIR POLYMERIC ELECTROSPUN

VIRGINIA HIDOLINA COLLINS MARTINEZ (2012)

Silver nanoparticles (AgNps) have played an important role because of their strong bactericidal

and fungicidal activity. Within methods of synthesis for nanoparticles, the biological synthesis

represents a clean alternative, presumably non-toxic and friendly environment for the formation

of metal nanoparticles [1].

The incorporation AgNPps in polymeric matrices by process electrospinnig has generated

materials with improved bactericidal, physical and mechanical properties[2] . Electrospinning is a

low cost and continuous process to obtain polymeric nanofibers with different morphologies and

ultrathin diameter, which can be applied in many fields.

The use of plants and their extracts to obtain metallic nanoparticles has been developed recently,

in this work we present the results to synthesize AgNps by using the nopal extract (Opuntia sp) as

a reducing agent in the presence of biocompatible water-soluble polymers such as poly(vinyl

alcohol) (PVA), acting as stabilizing agents for the nanoparticles and then electrospun them to

obtain nanofibers charged with AgNps.

Conference poster

Nanoparticles BIOLOGÍA Y QUÍMICA QUÍMICA QUÍMICA FÍSICA OTRAS

SYNTHESIS OF MAGNETIC MIXED OXIDE NANOPARTICLES USING THE NOVEL OIL-IN-WATER MICROEMULSION REACTION METHOD

Kelly Pemartin MARGARITA SANCHEZ DOMINGUEZ (2011)

Recently, an oil-in-water microemulsion reaction method was developed for the

preparation of nanomaterials. This novel method allowed a better control of the

size and crystallinity of the obtained nanoparticles compared to other methods.

The system used in this study was water, n- alkyl fatty alcohol ethoxylated

surfactants and hexane. A selected microemulsion composition was used for

the synthesis of 5-10 nm Mn-Zn ferrite nanoparticles which were characterized

by High Resolution Transmission Electron Microscopy (HRTEM) and X-Ray

Diffraction. In addition, magnetic properties of the Mn-Zn ferrite nanoparticles

were assessed. Hence, magnetic nanostructured materials were synthesized in

a predominantly aqueous environmentally friendly media (oil-in-water

microemulsion). The properties of Mn-Zn ferrite nanoparticles were compared to

those prepared using the water-in-oil microemulsion reaction method.

Conference proceedings

magnetism Nanoparticles BIOLOGÍA Y QUÍMICA QUÍMICA OTRAS ESPECIALIDADES QUÍMICAS OTRAS

Reaction Parameters for Controlled Sonosynthesis of Gold Nanoparticles

Alma Laura González Mendoza LOURDES ISABEL CABRERA LARA (2015)

The synthesis of gold nanoparticles by sonochemical technique has been previously performed with excellent results. The synthesis has been carried out in the presence of citric acid, a strong reducing agent, which allows the nucleation and growth of gold nanoparticles, at the same time that controls particle size. In this work, we report the use of sodium tartrate as a mild reducing agent that allows a better understanding of the effect of the reaction parameters during gold nanoparticle synthesis. A conventional sonication bath (37 kHz) was used for the sonochemical synthesis. This work focuses on the reaction temperature effect and the effect of sodium tartrate concentration. It was confirmed that particle size, and particle morphology is dependent of these two reaction parameters. Equally, colloidal stabilization was related to reaction temperature and sodium tartrate concentration. It was also determined that Ostwald ripening takes place during sonochemical reaction under our conditions, allowing us to understand the mechanism that takes place during synthesis. Gold nanoparticles with main particle size of 17 nm were achieved by this method.

Article

Química Gold colloidal suspension nanoparticles sonosynthesis sodium tartrate BIOLOGÍA Y QUÍMICA

Synthesis, characterization and magnetic properties of Co@Au core-shell nanoparticles encapsulated by nitrogen-doped multiwall carbon nanotubes

Synthesis, Characterization and Magnetic Properties of N-doped multiwall carbon nanotubes encapsulated Co@Au core-shell nanoparticles

Emilio Muñoz Sandoval NESTOR PEREA LOPEZ RODOLFO LIMA JUAREZ GLADIS JUDITH LABRADA DELGADO BEATRIZ ADRIANA RIVERA ESCOTO Adalberto Zamudio Ojeda Héctor Gabriel Silva Pereyra EMMANUEL ROBLES AVILA MAURICIO TERRONES MALDONADO (2014)

"Co/Au bilayer thin films were deposited on Si/SiOx substrates using the magnetron sputtering method and used as a catalytic support to grow forests of aligned nitrogen-doped multiwalled carbon nanotubes (N-MWCNT) via chemical vapor deposition (CVD) at 850 °C, using benzylamine (C6H5CH2NH2) as a carbon and nitrogen source. Interestingly, the resulting N-MWCNT contains Co@Au core-shell nanoparticles located at their tips. We found that the metal particle cores consist of cobalt coated by an Au shell of few nanometers. Magnetic measurements revealed a ferromagnetic behavior of the system composed of Co@Au nanoparticles encapsulated inside N-MWCNT. The results are compared with pristine N-MWNT containing only Co nanoparticles encapsulated in their cores."

Article

Chemical vapor deposition Doping (additives) Multiwalled carbon nanotubes (MWCN) Nanoparticles Synthesis (chemical) BIOLOGÍA Y QUÍMICA QUÍMICA QUÍMICA

Synthesis of ZnMn2O4 nanoparticles by a microwave-assisted colloidal method and their evaluation as a gas sensor of propane and carbon monoxide

JUAN PABLO MORAN LAZARO ERWIN SAID GUILLEN LOPEZ FLORENTINO LOPEZ URIAS Emilio Muñoz Sandoval OSCAR BLANCO ALONSO Héctor Guillén Bonilla ALEX GUILLEN BONILLA VERONICA MARIA RODRIGUEZ BETANCOURTT Marciano Sánchez Tizapa María de la Luz Olvera Amador (2018)

"Spinel-type ZnMn2O4 nanoparticles were synthesized via a simple and inexpensive microwave-assisted colloidal route. Structural studies by X-ray diffraction showed that a spinel crystal phase of ZnMn2O4 was obtained at a calcination temperature of 500 °C, which was confirmed by Raman and UV-vis characterizations. Spinel-type ZnMn2O4 nanoparticles with a size of 41 nm were identified by transmission electron microscopy. Pellet-type sensors were fabricated using ZnMn2O4 nanoparticles as sensing material. Sensing measurements were performed by exposing the sensor to different concentrations of propane or carbon monoxide at temperatures in the range from 100 to 300 °C. Measurements performed at an operating temperature of 300 °C revealed a good response to 500 ppm of propane and 300 ppm of carbon monoxide. Hence, ZnMn2O4 nanoparticles possess a promising potential in the gas sensors field."

Article

ZnMn2O4 Nanoparticles Microwave Gas sensor BIOLOGÍA Y QUÍMICA QUÍMICA QUÍMICA

Nanopartículas de HfO2 embebidas en una matriz de óxido spin-on-glass como capa de atrapamiento de carga para dispositivos de memoria

RAFAEL ORTEGA HERNANDEZ (2012)

The technological progress and the scaling down of electronic devices have

carried out to new research in nonvolatile memory industry. The typical

silicon-oxide-nitride-oxide-silicon (SONOS) charge trapping-based nonvolatile

memories have been widely studied in past years. The main problem of

SONOS devices is the high leakage current due to scaling down of ONO

layers. There are a wide variety of films with higher dielectric constant values

(κ) other than SiO2 which seems to solve the leakage current problem. At this

time, interest is centered on films such as HfO2 with κ value of 25 which

appears to be a promising candidate to replace Si3N4 films as the charge

trapping layer of SONOS-type memory devices. These high-κ materials lead

to a new type of memory structure Metal/Oxide/High-κ oxide/Oxide/Silicon

(MOHOS) memory.

In this thesis we present the use of HfO2 nanoparticles (np-HfO2) embedded

in a spin-on glass oxide matrix as an active charge trapping layer for

MOHOS-type memory structures. The deposition of charge-trapping layer is

performed by the sol-gel technique and it is characterized at different np-HfO2

concentrations. Fourier Transform Infrared Spectroscopy (FTIR) in

absorbance mode is used to observe the presence of chemical bonding

presented in the high-κ layer. Also, different annealing temperatures are

experimented for final curing of this film. The top oxide of the structure is also

deposited by the sol-gel method. For this layer, the same spin-on glass that

was used for embedding np-HfO2 is used. For these reasons, the MOHOStype

structure is obtained by a very simple and low-cost deposition method.

Finally, figures of merit like programming (writing/erasing) times and retention

time are presented and correlated to obtain the general performance of the

MOHOS-type memory devices.

El progreso tecnológico y el escalamiento de los dispositivos electrónicos han

llevado a la investigación en nuevas áreas en la industria de dispositivos de

memorias no volátiles. La memoria no volátil de atrapamiento de carga silicio-xido-nitruro-óxido-silicio (SONOS) ha sido ampliamente investigada en años

anteriores. Sin embargo, el principal problema de los dispositivos de memoria

SONOS son las corrientes de fuga debido a la reducción en el espesor de la

estructura ONO. Existe una amplia variedad de materiales con una constante

dieléctrica (κ) mayor que la del dióxido de silicio (SiO2) que pueden resolver

el problema de corrientes de fuga. Por el momento, nuestro interés se centra

en el óxido de hafnio (HfO2), con un valor de constante dieléctrica κ≈25, el

cual parece ser un posible material para reemplazar la capa de nitruro de

silicio (Si3N4) como la capa de atrapamiento de carga en dispositivos de

memoria SONOS. Estos materiales de alta constante dieléctrica dan lugar a

un nuevo tipo de dispositivos de memoria Metal/Oxido/Oxido de alta

κ/Oxido/Silicio (MOHOS).

En esta tesis, se presenta el uso de nanopartículas de HfO2 (np-HfO2)

embebidas en óxido spin-on glass como carga de atrapamiento de carga en

estructuras de memoria tipo MOHOS. El depósito de la capa de atrapamiento

de carga se realiza mediante la técnica sol-gel y se experimenta con

diferentes concentraciones de np-HfO2. El estudio de composición química

de esta capa se lleva a cabo a través de Espectroscopia de Transformada de

Fourier en Infrarrojo (FTIR). También, se experimenta con diferentes

temperaturas de curado de la capa de alta constante dieléctrica. El óxido de

bloqueo se deposita por el método de sol-gel. De esta forma, la obtención de

la estructura tipo MOHOS se lleva a cabo de una manera sencilla y a bajo

costo. Finalmente, las figuras de mérito como el tiempo de programación

(escritura/borrado) y el tiempo de retención se presentan para obtener el

rendimiento de estos dispositivos de memoria.

Master thesis

Nanoparticles High-k dielectric thin films Semiconductor storage CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA FÍSICA ELECTRÓNICA

Preparation of nanoparticles of barium ferrite from precipitation in microemulsions

JOSE ANDRES MATUTES AQUINO (1999)

Magnetic nanoparticles of barium ferrite (BaFe12O19) have been synthesized using a microemulsion mediated process.

The aqueous cores of water-in-oil microemulsions were used as constrained microreactors for the precipitation

of precursor carbonate and hydroxide particles. These precursors were then calcined at 925C for 12 h, during

which time they were transformed to the hexagonal ferrite. The pH of reaction was varied between 5 and 12, and

it was found that the fraction of non-magnetic hematite (-Fe2O3) in the particles varied with the pH of reaction,

thus affecting the magnetic properties of the particles. The same precursor particles were also prepared by bulk

co-precipitation reaction for comparison. It was found that the microemulsion derived nanoparticles of barium ferrite

had both higher intrinsic coercivity (Hc) and saturation magnetization (s) than the particles derived from bulk

co-precipitation. Particles were analyzed by electron microscopy, X-ray diffraction, differential thermal analysis

(DTA), thermogravimetric analysis (TGA) and vibrating sample magnetometry (VSM). The best barium ferrite

particles produced by the microemulsion synthesis method yielded an intrinsic coercivity of 4310 Oe and a saturation

magnetization of 60.48 emu/g.

Article

nanoparticles microemulsions CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA FÍSICA OTRAS ESPECIALIDADES FÍSICAS OTRAS

NANO-ANTENNAS EXCITATION WITH VISIBLE LIGHT AND THEIR RESPONSE AS OBSERVED WITH A CONFOCAL MICROSCOPE

Daniel Luis (2019)

"A century has gone by since antennas were used for the first time to control emission and reception of many types of electromagnetic radiation. The reescalation of antennas to smaller sizes and the need of on a chip devices motivated the manufacture of the so called nano-antennas that can focus farther than the diffraction limit. It is well known that metallic particles sustain resonance plasmonic modes in visible wavelengths, making them natural optic antennas. As happened with the conventional radiative antennas, nowadays it is important to characterize the radiation pattern emitted by these nano-antennas. In this research, we pretend to characterize at least qualitatively the dynamic behavior of super paramagnetic nanoparticles by exposing them to an electromagnetic field generated by excited nano-antennas of the bowtie type. We use a confocal microscope since it is a technique that increases the contrast of an image by using a pinhole that obstructs the light that is out of the focal plane. This results in a system that not only discriminates field of view over the focal plane, but it also permits depth selection inside of the specimen under observation."

Conference poster

Confocal microscopy Nanoparticles CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA FÍSICA ÓPTICA ÓPTICA

Síntesis de nanopartículas de TiO2 con alta área superficial para degradación de contaminantes en agua

JESUS VARGAS HERNANDEZ Eduardo García Garcilazo Alejandro Barron Baza Karina Soriano Silverio (2016)

Síntesis de nanopartículas con baja aglomeración a partir del método sol-gel, con el uso de un surfactante Polivinilpirrolidona PVP.

El dióxido de titanio es uno de los materiales más importantes y básicos de nuestra vida diaria, ha emergido como un material con excelente propiedades fotocatalíticas para la purificación del medio ambiente. Sin embargo existen limitaciones debido a la naturaleza de la muestra que impiden que incremente su eficiencia de degradación de colorantes orgánicos. La originalidad de este proyecto consiste en sintetizar dióxido de titanio con alta área superficial. El preparar materiales a escala nanométrica tiene grandes ventajas debido a que para alguna aplicaciones los materiales incrementan sus propiedades enormemente. Sin embargo para el proceso de fotocatálisis existe un fenómeno que disminuye su eficiencia, llamado “aglomeración”. Dicho fenómeno consiste en que las partículas con tamaño nanométrico, se unen mediante fuerzas electrostáticas, reduciendo el área expuesta. En este proyecto se trabajaron con surfactantes orgánicos que tienen la función de evitar que las partículas se aglomeren y con ello aumenten su eficiencia fotocatalítica. Los resultados de microscopía electrónica de barrido de alta resolución muestran que el surfactante tiene el efecto que se deseaba debido a que se muestran partículas menos aglomeradas. Dicha propiedad aumento la eficiencia de degradación del azul de metileno general, el cual presenta deplorables condiciones.

Article

Nanoparticles Surface Area sol-gel BIOLOGÍA Y QUÍMICA

Synthesis of carbon nano-onions doped with nitrogen using spray pyrolisis

EDUARDO TOVAR MARTINEZ JOSE ADAN MORENO TORRES JORGE VALENTIN CABRERA SALAZAR MARISOL REYES REYES Luis Felipe Cházaro Ruiz ROMAN LOPEZ SANDOVAL (2018)

"In this work, we have synthesized carbon nano-onions (CNOs) doped with nitrogen and iron carbide core. These nanostructures were synthesized pyrolysing various alcohol-benzylamine reaction mixtures. These CNOs showed a certain degree of functionalization of their surfaces, depending of the solvent, as well as n-type doping due to the inclusion of N atoms in the graphene layers. Ratios of O atoms to C atoms as well as to N atoms of the pyrolyzed solution play an important role in the morphology of the CNOs and on the phase of the iron core. Differences in the morphology of the samples have an important effect on their electrical conductivity as well as in their electrochemical properties. Synthesized samples showing well-defined CNOs, the sintering between them is negligible, have a low conductivity and higher capacitance, while those samples showing the best conductivities and lower capacitances, the CNOs in samples are connected between them by turbostratic graphite ribbons, in similar way to the CNOs synthesized from carbon nanodiamond annealed in argon atmosphere."

Article

Electrochemical performance Raman-spectroscopy Oxygen Nanotubes Reduction Nanodiamond Nanoparticles Graphene Soot Microscopy BIOLOGÍA Y QUÍMICA QUÍMICA QUÍMICA