Thailand's nanotech research tackles disaster prevention

Nano-sacks could replace traditional sandbags for flood control

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[BANGKOK] Recent flooding in Thailand has given the country's nanotechnology research centre an opportunity to show how nano products ranging from antimaterial bednets to flood prevention technology could help mitigate the impact of future natural disasters.

One example is the nano-sack or N-Sack, a product that resembles giant, superabsorbent diapers (nappies). It uses hydrogel and nano coating to absorb water, and is being promoted as a potential replacement for traditional sandbags for flood control.

"It is our hope that the nano-sack development will be refined and can be used before the next rainy season," Sirirurg Songsivilai, executive director of the state-run National Nanotechnology Center told SciDev.Net.

"The 2011 flood in Thailand was an eye opener for both the public and the government sector. It provided our research institution with an opportunity to participate in relief efforts," he said.

For example, Sirirurg said that the research centre distributed bednets, mosquito-repellent gel and powder, all making use of nanotechnology. The net material contains a nano-scale formulation of the chemical deltamethrin, which is absorbed by receptor cells at the tips of the legs of mosquitoes and kills them within minutes.

In association with the Petroleum Authority of Thailand, the research centre has also manufactured nanotechnology-based surface-cleaning solutions for homes and offices, which have been distributed to flood victims.

Sirirurg described these as more environment-friendly than conventional cleaning solutions as they consist of biodegradable materials, are locally sourced and are inexpensive. They also reinforce the government's efforts to promote nanotechnology as an internationally competitive industry.

The centre has also showcased a test kit for leptospirosis, a disease spread through contaminated water.

For the past decade, the Thai government has been investing in nanotechnology research and development, which seeks to create novel products that operate at the molecular level. Its goal is to make Thailand a major hub of nanotechnology research in Asia.

These efforts rose to prominence after Thailand's economy suffered from the 1997 Asian financial crisis, prompting the government to identify and promote industries that would make the country more globally competitive. Nanotechnology was identified as one of these industries, which led to the creation of the Bangkok-based centre in 2003.

Since its establishment, the nanotechnology centre has been developing a range of nano-products, particularly those that might support the agriculture sector. This is seen as a strategic move, as Thailand is one of the world's biggest exporters of rice, sugar and rubber.

After the 2011 flooding, the centre has designated disaster prevention and management as a priority

Sirirurg has acknowledged the importance of using nanotechnology to help flood victims and limit the spread of flood-borne diseases such as malaria. He hopes that the nanotechnology centre can also develop products, such as the N-Sacks, that can prevent this type of flooding from recurring.

fuente: http://www.scidev.net/es/new-technologies/nanotechnology/news/tailandia-nanotecnolog-a-y-prevenci-n-de-desastres.html

Tansistores de alto rendimiento con la impresión de inyección de tinta

Un equipo de investigadores de Japón ha desarrollado una nueva técnica de impresión por inyección de tinta para la fabricación de transistor es de película fina de alto rendimiento.

Tatsuo Hasegawa, del Instituto Nacional de Tecnología y Ciencia Industrial Avanzada (AIST) de Tsukuba, y sus colegas han ideado un nuevo proceso de impresión que combina una tinta de semiconductores y otra de cristalización en una sola. La primera es un semiconductor en un disolvente y la segunda, un "antidisolvente" (un líquido en el que el semiconductor es insoluble). El método produce películas delgadas policristalinas o de un solo cristal excepcionalmente uniformes que se forman en la interfase líquido-aire sobre un substrato.

El proceso a temperatura ambiente se puede utilizar para fabricar dispositivos electrónicos impresos de grand superficie, incluyendo pantallas flexibles, células solares, papel electrónico y láminas sensoras.

Fuente: http://nanotechweb.org/cws/article/tech/46558

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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