Hydrogen from Acidic Water: Potential Low Cost Alternative to Platinum for Splitting Water

A technique for creating a new molecule that structurally and chemically replicates the active part of the widely used industrial catalyst molybdenite has been developed by researchers with the U.S. Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab). This technique holds promise for the creation of catalytic materials that can serve as effective low-cost alternatives to platinum for generating hydrogen gas from water that is acidic.

Christopher Chang and Jeffrey Long, chemists who hold joint appointments with Berkeley Lab and the University of California (UC) Berkeley, led a research team that synthesized a molecule to mimic the triangle-shaped molybdenum disulfide units along the edges of molybdenite crystals, which is . almost all of the catalytic activity takes place. Since the bulk of molybdenite crystalline material is relatively inert from a catalytic standpoint, molecular analogs of the catalytically active edge sites could be used to make new materials that are much more efficient and cost-effective catalysts.

Although commonly thought of as a lubricant, molybdenite is the standard catalyst used to remove sulfur from petroleum and natural gas for the reduction of sulfur dioxide emissions when those fuels are burned. Recent studies have shown that in its nanoparticle form, molybdenite also holds promise for catalyzing the electrochemical and photochemical generation of hydrogen from water. Hydrogen could play a key role in future renewable energy technologies if a relatively cheap, efficient and carbon-neutral means of producing it can be developed.

Currently, the best available technique for producing hydrogen is to split water molecules into molecules of hydrogen and oxygen using platinum as the catalyst. However, with platinum going for more than $2,000 an ounce, the market is wide open for a low cost alternative catalyst. Molybdenite is far more plentiful and about 1/70^th the cost of platinum, but poses other problems.

Chang, Long and their research team met this challenge using a pentapyridyl ligand known as PY5Me₂ to create a molybdenum disulfide molecule that, while not found in nature, is stable and structurally identical to the proposed triangular edge sites of molybdenite. It was shown that these synthesized molecules can form a layer of material that is analogous to constructing a sulfide edge of molybdenite.

In 2010, Chang and Long and Hemamala Karunadasa, who is the lead author on this new Science paper, used the PY5Me₂ligand to create a molybdenum-oxo complex that can effectively and efficiently catalyze the generation of hydrogen from neutral buffered water or even sea water. Molybdenite complexes synthesized from this new molecular analog can just as effectively and efficiently catalyze hydrogen gas from acidic water.

DOE/ Lawrence Berkeley National Laboratory. "Hydrogen from acidic water: Potential low cost alternative to platinum for splitting water." ScienceDaily, 9 Feb. 2012. Web. 12 Feb. 2012.

Synthesis and luminescent properties of Ln3+ (Ln3+ = Eu3+, Dy3+) –doped Bi2ZnB2O7 phosphors

Melilites, with the general formula A₂XZ₂O₇, are a series of significant compounds expected as excellent hosts for luminescent materials. Recently, the luminescent properties of Sm3+-doped Bi₂ZnB₂O₇ were investigated, Eu3+ and Dy3+ ion-activated Bi2ZnB2O7 were prepared by a solid-state reaction and the structural character and photoluminescent properties of these phosphors were studied.

The new phosphors Bi₂ZnB₂O₇: Ln3+ (Ln3+ = Eu3+, Dy3+) were synthesized by solid-state reaction technique. The obtained phosphors were investigated by means of X-ray powder diffraction (XRD), photoluminescence excitation and emission spectra with the aim of enhancing the fundamental knowledge about the luminescent properties of Eu3+ and Dy3+ ions in the Bi₂ZnB₂O₇ host lattice. XRD analysis shows that all these compounds are of a single phase of Bi₂ZnB₂O₇.

The photoluminescent emission spectra of Bi2ZnB2O7:Eu3+ phosphor exhibit a well-known characteristic Eu3+ emission and the dominant photoluminescent excitation line is around 465 nm due to the 7F0→5D2 transition. The emission spectra of Bi₂ZnB₂O₇:Dy3+ phosphor show three bands centered at 482, 576 and 667 nm that originate from the transitions of 4F9/2→6H15/2, 4F9/2→6H13/2 and 4F9/2→6H11/2 of Dy3+, respectively. The excitation spectra have several sharp lines in the range of 250~520 nm corresponding to the transitions from the ground state of Dy3+ (6H15/2) to different excitation levels

The excitation and emission spectra of Bi₂ZnB₂O₇: Ln3+ (Ln3+ = Eu3+, Dy3+) at room temperature show the typical 4f-4f transitions of Eu3+ and Dy3+, respectively. The hypersensitive transitions of 5D0→7F2 (Eu3+) and 4F9/2→ 6H13/2

(Dy3+) are relatively higher than those of the insensitive transitions in Bi₂ZnB₂O₇. It is conceivable that the Bi₂ZnB₂O₇ structure provides asymmetry sites for activators (Eu3+, Dy3+). The optimum concentrations of Eu3+ and Dy3+ ions in

Bi₂ZnB₂O₇ phosphors are both x =0.05.

Emission spectrum of (Bi1-xEux)2ZnB2O7 (x = 0.01, 0.03, 0.05, 0.07, 0.09) under 465 nm excitation

Reference.

Zhang, Q., Wang, J., Ni, H. Wang, L.(2012) Synthesis and luminescent properties of Ln3+ (Ln3+ = Eu3+, Dy3+) –doped Bi2ZnB2O7 phosphors Rare Metals. 1001-052. Vol. 31. P.35.

High frequency impedance spectroscopy on ZnO nanorod arrays.

High frequency impedance spectroscopy on ZnO nanorod arrays.

The radio-frequency (rf)-to-microwave impedance spectra of solution grown ZnO nanorods have been measured from 0.1 to 50 GHz using vector network analysis. To increase interaction with rf/microwave fields, the nanorods were assembled by dielectrophoresis into arrays on coplanar waveguides. 


The average complex impedance frequency response per nanorod in an array was accurately modeled as a simple three-element circuit composed of the inherent nanorod resistance in series with a parallel resistor-capacitor representing the contact. 


The nanorod resistance dominates at high frequencies while the contact impedance dominates at low frequencies, permitting a quantitative separation of contact effects from nanorod properties. The average inherent resistivity of a nanorod was found to be ∼10^-2 Ω cm, indicating the nanorods were unintentionally highly doped. Accuracy of the inherent resistance measurement was limited by the highly conductive nature of the nanorods used and the upper limit of the experimental frequency range. Determination of the nanorod resistance becomes more accurate for higher resistivity nanorods, so high frequency impedance spectroscopy will provide an increasingly valuable electrical characterization technique as the ability to synthesize more intrinsic (i.e., lower unintentional dopant density) ZnO nanorods improves.


fuente:
Scrymgeour, D. A., Highstrete, C., Lee, Y., Hsu, J. P., & Lee, M. (2010). High frequency impedance spectroscopy on ZnO nanorod arrays. Journal Of Applied Physics, 107

Atomic Antenna Behavior in Graphene

Atomic-level defects in graphene could be a path forward to smaller and faster electronic devices, according to a study led by researchers at the Department of Energy's Oak Ridge National Laboratory.

With unique properties and potential applications in areas from electronics to biodevices, graphene, which consists of a single sheet of carbon atoms, has been hailed as a rising star in the materials world. Now, an ORNL study published in Nature Nanotechnology suggests that point defects, composed of silicon atoms that replace individual carbon atoms in graphene, could aid attempts to transfer data on an atomic scale by coupling light with electrons.

"In this proof of concept experiment, we have shown that a tiny wire made up of a pair of single silicon atoms in graphene can be used to convert light into an electronic signal, transmit the signal and then convert the signal back into light," said coauthor Juan-Carlos Idrobo, who holds a joint appointment at ORNL and Vanderbilt University.

An ORNL-led team discovered this novel behavior by using aberration-corrected scanning transmission electron microscopy to image the plasmon response, or optical-like signals, of the point defects. The team's analysis found that the silicon atoms act like atomic-sized antennae, enhancing the local surface plasmon response of graphene, and creating a prototypical plasmonic device.

"The idea with plasmonic devices is that they can convert optical signals into electronic signals," Idrobo said. "So you could make really tiny wires, put light in one side of the wire, and that signal will be transformed into collective electron excitations known as plasmons. The plasmons will transmit the signal through the wire, come out the other side and be converted back to light."

Complete article in here

El juego del huesped

El juego del huesped

View more documents from José Juárez.

Delirium

DELIRIUM

Los altavoces de la sala de espera de la aerolínea AirElements anuncian el momento de abordar el vuelo a Normandia, Francia. En la cabina de primera clase la azafata se presenta con cada uno de los pasajeros, “Buena tarde señor Louis Nicolas Vauquelin”, el señor incomodado por la formalidad recibida, le responde de manera templada como un metal mientras que la tenue luz suavizaba el momento, “Madame, por favor llámeme Be”, en ese momento la azafata supo que de los 118 pasajeros el del lugar 4 era especial.

El avión despego, el señor Be leía un libro y tomaba notas muy especificas, en momentos parecía arrepentirse y tachaba sobre la hoja, claramente le apuraba terminar el libro ya que no paro, hasta el momento en que el aroma de la cena lo desconcentró. A su lado se encontraba la azafata con una suave mirada y una charola en manos, Be solo dejo su libro y sonrió diciendo “Madame usted sabe mi nombre pero yo no se el suyo” la azafata de origen francés se sonrojo contestando en voz baja “Señor me llamo Marie Curie, me permite servirle algo de tomar”, impresionado por su nombre tomo la charla y contesto “Marie sorprendame”.

Marie nerviosa caminó a la parte de trasera del avión, donde sirvió un vaso con dos hielos y un Valencia Reserva Especial, solo usado para los pasajeros más importantes. Al momento de servir el vaso le comento “Señor esta es una reserva especial le recomiendo que no espere más de dos minutos para tomarlo ya que se oxida y el sabor cambia”, una fija mirada se presento junto con un silencio confortable, momento que fue interrumpido cuando el pasajero del asiento 11 grito cuando un vaso de agua le callo encima. Marie corrió a asistir al pasajero 11, Be regresó a su libro, mientras lentamente bebía. Una y otra vez leía el mismo párrafo pero no lograba concentrar sus ideas, lo único que tenía en mente eran los ojos de Marie. Con una fuerte reacción, como un impulso eléctrico, azoto el vaso en la mesa, le dio un trago y antes de azotar de nuevo el vaso, se repitió en la mente “Be concentrate en la misión, no hay espacio para errores”, dejo el vaso suavemente y regreso a su lectura. Agarro la servilleta de la comida y con una pluma empezó a dibujar un plano, una y otra vez regresaba al libro a corroborar las medidas, .90 x .31 x 1.12.

El capitán anunció que a partir de ese momento ya podían hacer uso de equipos electrónicos, Be saco su computadora y comenzó a capturar toda la información, un programa muy moderno mostraba una estructura compleja, para acabar solo requería de la configuración electrónica, la cual tras una hora de estudiar su libro la obtuvo, 1s²2s², código que no dejo pasar ya que rápidamente se lo apunto en la mano. Marie se acerco ofreciendo de manera sigilosa más licor, Be con un movimiento de mano le indico “no más”.

Se encontraban volando a 2,770 pies sobre el nivel del mar, Be sabia que tenia que esperar a que el avión llegara a 1,277 pies. Se paro y camino a la parte trasera del avión, paro cuando vio que el pasajero del asiento 13 era tres veces más grande que él, lo único que le paso por la mente fue “si yo peso 9g seguro esté pesa como 26g”, el pasajero torno la mirada a el y sonrió, Be impactado solo regreso la sonrisa y continuo su camino. Al pasar por el asiento numero 29 Be tropieza con una maleta que estaba fuera de lugar, un señor moreno apenado por el hecho le ayuda a levantarse y se disculpa, Be se levanta rápidamente comentando, “no se preocupe, fue mi error, tantas horas sentado tal parece que ya no se como caminar, por suerte esto acabara pronto” Be se acomodo la ropa y continuo su camino.

Al llegar al fondo del avión vio a Marie sentada tomando un vaso con agua, Be no pudo resistir el sentarse a su lado, Marie sorprendida y sonrojada dijo, “Señor en que le puedo ayudar” Be de manera suave contesto, “Deja atrás las formalidades que con tu mirada me atas y bien lo sabes” Marie no se pudo contener y una carcajada soltó, Be acerco su mano a la de Marie, con tan solo las yemas de los dedos Be comenzó a acariciar la mano de Marie, ella nerviosa y el solo mostraba firmeza y una compleja mirada la cual no podía resistir.

Sin pensarlo dos veces Marie cerro los ojos, Be inclino la cabeza lentamente, con forme se acerco a los labios de Marie cerró los ojos y empezó a besarla suavemente, con un gentil beso de boca cerrada, Marie puso su brazos al rededor de la cabeza de Be, con una mano sobre la cabeza de Be, comenzó a alborotarle el cabello, el único sonido, la respiración de ambos. Be se había dado cuenta que estaba enamorado.

Con una misión en mente por cumplir, Be no espero un momento más y abrazando a Marie se levanto susurrando al oído de Marie. Abrió la puerta del baño, Marie impulsada por el sentimiento entro al baño, sus ojos ardían de pasión, mientras que con las yemas de sus dedos recorría el cuerpo de la mujer, provocando un descontrolado río de sensaciones que hasta ese momento nunca antes había experimentado, sus cuerpos rozaban delicada y apasionadamente mientras sus labios se unían, experimentaban lo prohibido, no importaba lo que pasara en ese momento solo eran ellos dos, ya estaban unidos, no había vuelta atrás, Be conoció lo que era el amor.

El capitán anuncio el descenso, Be sabia que el final estaba por llegar, Marie apresurada por estar preparada para el aterrizaje comenzó a vestirse, Be la abrazo y le dijo “Mi verdadero nombre es Fredrich Wohler. Hoy he nacido, tu me as hecho vivir” Marie desconcertada contesto “Be no comprendo que me quieres decir, como que tu nombre es Fredrich” Be extendió sus brazos, la rodio y abrazo, susurrando le al oído “Te amo…”, el reloj marcaba las 22:30 horas.

Nota del periódico del día siguiente:

Ataque terrorista

La Union Europea se encuentra de luto. El gobierno investiga como un terrorista abordo el avión portando explosivos, tras pasar los rayos x del aeropuerto.

Las primeras investigaciones muestran que el ataque terrorista con berilio responsable de daños en vías respiratorias, desarrollo de cáncer y daños en el ADN sufrido por los habitantes de la zona fue causado por una bomba en el avión que se desplomo a las 22:30 horas el día de ayer. Hasta el momento el gobierno sospecha de un pasajero conocido como Be, se cree que contaba con un cómplice que hasta el momento se desconoce su identidad.

Nombre Berilio

Número Atómico 4

Valencia 2

Estado de oxidación +2

Electronegatividad 1.5

Radio Covalente 0.90

Radio Ionico 0.31

Ratio atómico 1.12

Configuración electrónica 1s²2s²

Masa atómica 9,0122

Densidad 1.85

Punto de ebullición 2770

Punto de fusión 1277

Descubridor Fredrich Wohler

Environmentalists worried about nano-silver

Updated September 15, 2011 18:28:39

Datos de mapa - Términos de uso

Mapa

MAP: Melbourne 3000

Environmentalists want the Federal Government to investigate the health effects of the use of a common antibacterial ingredient.

Nano-silver has antibacterial properties and is used in a range of products including socks, children's toys and soap.

A report from Friends of the Earth said some of Australia's top microbiologists are worried about excessive use of the chemical.

The group's nanotechnology spokesman, Dr Gregory Crocetti, said the products could contribute to antibiotic-resistant viruses, which are responsible for a growing number of deaths.

"Now in Australian hospitals we see about 7,000 deaths from antibiotic resistant bacteria, these superbugs," he said.

"So these leading microbiologists are warning that this is just going to make this problem even worse."

Dr Crocetti said the Government should regulate the use of nano-silver.

"These products could easily say containing nano-silver, if the companies were forced to brand that on their products, they could label that.

"The Government needs to conduct some tests into that. There's been no testing into the use of silver or nano-silver products in the history of Australian regulation," he said.