PNNL: News - Halving hydrogen

PNNL: News - Halving hydrogen

Like a hungry diner ripping open a dinner roll, a fuel cell catalyst that converts hydrogen into electricity must tear open a hydrogen molecule.

Now researchers have captured a view of such a catalyst holding onto the two halves of its hydrogen feast. The view confirms previous hypotheses and provides insight into how to make the catalyst work better for alternative energy uses.

This study is the first time scientists have shown precisely where the hydrogen halves end up in the structure of a molecular catalyst that breaks down hydrogen, the team reported online April 22 in Angewandte Chemie International Edition. 

The design of this catalyst was inspired by the innards of a natural protein called a hydrogenase enzyme.

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Neutron crystallography shows this iron catalyst gripping two hydrogen atoms (red spheres). This arrangement allows an unusual dihydrogen bond to form between the hydrogen atoms (red dots).

High-tech Materials Purify Water with Sunlight

Sunlight plus a common titanium pigment might be the secret recipe for ridding pharmaceuticals, pesticides and other potentially harmful pollutants from drinking water. 

Scientists combined several high-tech components to make an easy-to-use water purifier that could work with the world’s most basic form of energy, sunlight, in a boon for water purification in rural areas or developing countries.

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Graphene (above), along with sunlight and titanium dioxide, can purify drinking water.

 Credit: Tyndall National Institute

Recovering Metals and Minerals from Waste

Scarcity of clean water is one of the most serious global challenges. In its spearhead programme, VTT Technical Research Centre of Finland developed energy-efficient methods for reuse of water in industrial processes and means for recovering valuable minerals and materials from waste for recycling. 

Rapid tools were also developed for identification of environmental pollutants. 

When water and wastewater systems are developed in a comprehensive manner, it is possible to recover valuable metals and other materials and secure availability of clean water. 

Cleaning and treatment processes can also be linked to energy production, and the processes and urban structures designed in such a manner that wastewater treatment does not consume energy or cause extra costs. 

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Credit: Prof. Mona Arnold, et al.

Researchers Describe Oxygen’s Different Shapes

Oxygen-16, one of the key elements of life on earth, is produced by a series of reactions inside of red giant stars. 

Now a team of physicists, including one from North Carolina State University, has revealed how the element’s nuclear shape changes depending on its state, even though other attributes such as spin and parity don’t appear to differ. 

Their findings may shed light on how oxygen is produced.

Carbon and oxygen are formed when helium burns inside of red giant stars. 

Carbon-12 forms when three helium-4 nuclei combine in a very specific way (called the triple alpha process), and oxygen-16 is the combination of a carbon-12 and another helium-4 nucleus.

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The shape of oxygen-16 in its ground and first excited state. Credit: Dean Lee et al.

 

Boron, Discovered in 1808, Gets a Nano Refresh

The National Nanotechnology Initiative defines nanotechnology as the understanding and control of matter at the nanoscale, at dimensions of approximately 1 and 100 nanometers, where unique phenomena enable novel applications. Nanotechnology is taking the world by storm, revolutionizing the materials and devices used in many applications and products. That’s why a finding announced by Xiang-Feng Zhou and Artem R. Oganov, Group of Theoretical Crystallography in the Department of Geosciences, are so significant. 

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Projections of 2 × 2 × 1 supercell of Pmmn-boron structure along [001] and [100] directions.

Graphene’s Love Affair with Water

Graphene has proven itself as a wonder material with a vast range of unique properties. Among the least-known marvels of graphene is its strange love affair with water.

Graphene is hydrophobic – it repels water – but narrow capillaries made from graphene vigorously suck in water allowing its rapid permeation, if the water layer is only one atom thick – that is, as thin as graphene itself.

This bizarre property has attracted intense academic and industrial interest with intent to develop new water filtration and desalination technologies.

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Credit: Dr Rahul Nair and Prof Andre Geim, The University of Manchester

Diamond Film Possible Without the Pressure

Perfect sheets of diamond a few atoms thick appear to be possible even without the big squeeze that makes natural gems.

Scientists have speculated about it and a few labs have even seen signs of what they call diamane, an extremely thin film of diamond that has all of diamond’s superior semiconducting and thermal properties.

Now researchers at Rice University and in Russia have calculated a “phase diagram” for the creation of diamane. The diagram is a road map. It lays out the conditions – temperature, pressure and other factors – that would be necessary to turn stacked sheets of graphene into a flawless diamond lattice.

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The phase diagram developed by scientists at Rice University and in Moscow describes the conditions necessary for the chemical creation of thin films of diamond from stacks of single-atomic-layer graphene. (Credit: Pavel Sorokin/Technological Institute for Superhard and Novel Carbon Materials)

Molecular Collisions Now Imaged Better Than Ever

Molecular physicists from Radboud University Nijmegen have produced images of the changes in direction of colliding nitrogen monoxide molecules (NO) with unprecedented sharpness. 

By combining a Stark decelerator with advanced imaging techniques, they were able to obtain very high resolution images of the collision processes. 

The results were published in Nature Chemistry on 9 February. 

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Visualisation of the collisions between NO and helium (left) and NO and neon (right). The top images show the research results of Van de Meerakker and his colleagues; the bottom images show the visualised theoretical predictions of the collisions. Red indicates a high probability of change of direction; blue indicates a low probability. The small peaks show the diffraction oscillations (Credits: Image Courtesy of Nature Chemistry).

Graphene-like material made of boron a possibility, experiments suggest

Graphene has been heralded as a wonder material. Made of a single layer of carbon atoms in a honeycomb arrangement, graphene is stronger pound-for-pound than steel and conducts electricity better than copper. 

Since the discovery of graphene, scientists have wondered if boron, carbon’s neighbor on the periodic table, could also be arranged in single-atom sheets. 

Theoretical work suggested it was possible, but the atoms would need to be in a very particular arrangement.

Boron has one fewer electron than carbon and as a result can’t form the honeycomb lattice that makes up graphene. 

For boron to form a single-atom layer, theorists suggested that the atoms must be arranged in a triangular lattice with hexagonal vacancies — holes — in the lattice.

 

Unlocking the secrets of the B₃₆ cluster A 36-atom cluster of boron, left, arranged as a flat disc with a hexagonal hole in the middle, fits the theoretical requirements for making a one-atom-thick boron sheet, right, a theoretical nanomaterial dubbed “borophene.” Credit: Wang lab/Brown University

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Steering Electrons Along Chemical Bonds

Electron motions induced by a strong electric field are mapped in space and time with the help of femtosecond x-ray pulses. An x-ray movie of the crystal lithium hydride shows that the electric interaction between electrons has a decisive influence on the direction in which they move. An ionic crystal is a regular arrangement of positively and negatively charged ions in space. 

Crystals with rock salt structure. Upper crystal: sodium chloride (NaCl) with blue balls for Na+ ions and green balls for Cl- ions. Lower crystal: lithium hydride (LiH) with small blue balls for Li0.5+ ions and white balls for H0.5- ions. The grey-shaded plane indicates the sectional views. (Credit: MBI)

Credit: http://www.fv-berlin.de

Scientists ID New Catalyst for Cleanup of Nitrites

Chemical engineers at Rice University have found a new catalyst that can rapidly break down nitrites, a common and harmful contaminant in drinking water that often results from overuse of agricultural fertilizers.

Nitrites and their more abundant cousins, nitrates, are inorganic compounds that are often found in both groundwater and surface water. The compounds are a health hazard, and the Environmental Protection Agency places strict limits on the amount of nitrates and nitrites in drinking water. While it’s possible to remove nitrates and nitrites from water with filters and resins, the process can be prohibitively expensive.

Researchers at Rice University's Catalysis and Nanomaterials Laboratory have found that gold and palladium nanoparticles can rapidly break down nitrites. (Credit: M.S. Wong/Rice University)

Credit: http://news.rice.edu

Q-Glasses Could Be a New Class of Solids

There may be more kinds of stuff than we thought. A team of researchers has reported possible evidence for a new category of solids, things that are neither pure glasses, crystals, nor even exotic quasicrystals. Something else.

"Very weird. Strangest material I ever saw," says materials physicist Lyle Levine of the National Institute of Standards and Technology (NIST).

The research team from NIST and Argonne National Laboratory has analyzed a solid alloy that they discovered in small discrete patches of a rapidly cooled mixture of aluminum, iron and silicon. 

The material appears to have none of the extended ordering of atoms found in crystals, which would make it a glass, except that it has a very defined composition and grows outward from "seeds"—things that glasses most assuredly do not do.

 

The odd microstructure of this aluminum-iron-silicon mixture is seen in this image. The round nodules are the q-glass, not crystalline but with a well-defined chemical composition. The spherical shape indicates that they grow from an initial seed. The nodules use up iron and silicon in the mixture until the surrounding concentration of aluminum gets high enough to start forming aluminum crystals, seen as long bright lines radiating from the nodules. (Color added for clarity.) (Credit: Bendersky/NIST)

Credit: http://www.nist.gov

18-Crown-6

• 18-Crown-6 is an organic compound with the formula [C₂H₄O]₆ and the IUPAC name of 1,4,7,10,13,16-hexaoxacyclooctadecane. 
• It is a white, hygroscopic crystalline solid with a low melting point. 
• Like other crown ethers, 18-crown-6 functions as a ligand for some metal cations with a particular affinity for potassium cations (binding constant in methanol: 10⁶M^-1). 
• The synthesis of the crown ethers led to the awarding of the Nobel Prize in Chemistry to Charles J. Pedersen.
• Crown ethers are used in the laboratory as phase transfer catalysts. 
• In general however it is not widely used; cheaper and more versatile phase transfer catalysts are known. 
• In the presence of 18-crown-6, potassium permanganate dissolves in benzene giving the so-called "purple benzene", which can be used to oxidize diverse organic compounds. 
• More details are here. 

Credit: http://en.wikipedia.org/wiki/18-Crown-6

Organometallic Compounds

Compounds that contain a metal-carbon bond, R-M, are known as "organometallic" compounds.

• Organometallic compounds of Li, Mg (Grignard reagents) are amongst some of the most important organic reagents.

• Many other metals have been utilised, for example Na, Cu and Zn.

• Organometallic compounds provide a source of nucleophilic carbon atoms which can react with electrophilic carbon to form a new carbon-carbon bond. This is very important for the synthesis of complex molecules from simple starting materials.

• To rationalise the general reactivity of organometallics it is convenient to view them as ionic, so R-M = R-M+

• The most important reactions is this chapter are the reactions of organolithiums, RLi, and Grignard reagents, RMgX, with the carbonyl groups in aldehydes, ketones and esters to give alcohols. However, we will also look at some useful reactions involving Cu, Zn and Hg (mercury).

 For more details click here.

 Credit: Dr. Ian Hunt, Department of Chemistry, University of Calgary

Sodium Chloride Solution Formation

 


Credit: http://www.mhhe.com/physsci/chemistry/essentialchemistry

Solvay Process

 

For more click here.

Credit: http://www.chem.tamu.edu

Chemistry of Glass

Obsidian, a black volcanic glass, is probably the best known of the naturally occurring glasses. It was used by early man to form cutting tools, arrowheads and spearheads and is now used by modern man to make the sharpest surgical blades.

Synthetic glass was originally prepared by heating a mixture of sodium oxide (or sodium carbonate), calcium oxide and silicon dioxide (sand). If calcium oxide was not added to the melt, soda glass was obtained. Pure soda glass is not usable because of its high solubility in water. Soda lime glass has a large coefficient of expansion when heated and a low resistance to the effects of acids and bases. It usually has a green color due to the presence of iron oxide in the sand. It was later discovered that this color could be removed by adding manganese oxide to the melt when a colorless glass was desired. 

Manufactured glass is presumed to have been first used as a glaze for pottery. The earliest known glaze is on stone beads of the Badarian age of Egypt. These beads ranked in value with precious metals and stones at the time! The Egyptians first made vessels out of glass by the laborious process in which the glass was applied over a wooden or metal rod bit by bit. A cylinder of light blue glass made by this method dates back to the Akkad dynasty in 2600 B.C. Glass was first pressed into open molds in 1200 B.C. There is some evidence that Mesopotamia was the location where glass was first manufactured.

For more details click here.

Credit: Prof. Richard Banks, http://chemistry.boisestate.edu

Introduction to Supramolecular Chemistry

The emergence of supramolecular chemistry has had a profound effect on how efficiently chemists prepare structures of different sizes and shapes with dimension in the range of 1 to 100 nm using spontaneous secondary interactions such as hydrogen bonding, dipoledipole, charge transfer, van der Waals, and p-p stacking interactions. This so-called “bottom up” approach to construct nanostructures is advantageous over the “top down” approach such as microlithography which requires substantial effort to fabricate microstructures and devices as the target structures are extended to the range below 100 nm. For more details click here.

Image credit: Professor Kenneth N. Raymond
UC Berkeley Chancellor's Professor

Credit: http://scholar.lib.vt.edu

Valence Shell Electron Pair Repulsion Theory

VSEPR theory proposes that the geometric arrangement of terminal atoms, or groups of atoms about a central atom in a covalent compound, or charged ion, is determined solely by the repulsions between electron pairs present in the valence shell of the central atom. For more details click here.

Courtesy: http://intro.chem.okstate.edu

Valence Bond Theory and Hybrid Atomic Orbitals

The valence-bond approach considers the overlap of the atomic orbitals (AO) of the participation atoms to form a chemical bond. Due to the overlapping, electrons are localized in the bond region. The overlapping AOs can be of different types, for example, a sigma bond may be formed by the overlapping the following AOs.  For more details click here.

 Courtesy: http://www.science.uwaterloo.ca