SCIENCE & TECHNOLOGY CONCENTRATES
Carbon capture methods can cut power plant CO2 emissions by up to 90%. But the leading technology is expensive and energyintensive, and it requires extensive retrofits to divert power plant steam to drive the reactions. Amine solutions, which bind CO2 in an absorption column, are steam heated in a separate chamber to regenerate the solutions by driving off the CO2 for subsequent processing. Regenerating via an electrochemical process instead could reduce the needed retrofits and halve energy use yet retain the capture method’s effectiveness (Energy Environ. Sci. 2013, DOI: 10.1039/ c3ee41165f ). Developed by Michael Stern, Howard Herzog, and T. Alan Hatton of MIT, the process involves separating CO2 from the amine solution using a device featuring copper electrodes. Applying a positive voltage releases copper ions, which bind the amines, displacing CO2. The copper ions are recovered by reductively plating them back onto the electrode, freeing the amines for reuse. The electrically powered system, intended to be easily installed, is drawing power-company interest but would need to be scaled up, the researchers say.—PK
GREEN AMINATIONS WITHOUT PALLADIUM One of the largest classes of reactions used in medicinal chemistry is the palladiumcatalyzed cross-coupling of aryl halides with amines to make N-arylamines. During the past 20 years, this efficient method has largely replaced the classical nucleophilic aromatic substitution (SNAr) approach to N-arylations. One team of researchers is now suggesting that chemists have become so dependent on palladium-catalyzed N-arylations that they blindly use the method without giving SNAr a chance. Katie Walsh and Christopher J. Moody at the University of Nottingham, in England, and Helen F. Sneddon of GlaxoSmithKline note that heteroaryl substrates such as chloropyrimidines and chloropyrazines are highly reactive via SNAr, more so than chlorobenzene, and don’t need a palladium catalyst. With their thoughts on green chemistry, the researchers set out to optimize SNAr reactions of the heteroaryl chlorides (ChemSusChem 2013, DOI: 10.1002/cssc.201300239). They found that using potassium fluoride as a base and water as the solvent leads to
SENSOR DETECTS BACTERIA DEAD OR ALIVE To determine whether a particular bacterial species is resistant to an antibiotic, scientists try to grow the microbe in the medicine’s presence. For a slow-growing bacterium such as Mycobacterium tuberculosis, a doctor who sends a sample off to the lab might wait days or weeks for an answer. A team led by Giovanni Dietler, Sandor Kasas, and Giovanni Longo of ETH Lausanne, hopes to speed things up with a simple nanomechanical sensor that can distinguish between live and dead pathogens within an hour (Nat. Nanotechnol. 2013, DOI: 10.1038/nnano.2013.120). The device uses an atomic force microscope’s cantilever, which is a tiny diving-board-like probe. When the silicon nitride cantilever has bacteria such as Escherichia coli stuck to it, the device’s lowLive bacteria bound frequency oscillations (< 1 kHz) to a cantilever increase in amplitude. The scientists induce oscillation Detector believe this increase results from the changes, which are measured by microbes’ metabolic activity. When reflecting a laser the team flows the antibiotic ampicilbeam from the lin over cantilever-bound E. coli, the device’s surface. amplitude of the device’s oscillations decreases 20-fold in about five minLaser beam utes, indicating bacterial death, the Bacterium researchers say. For ampicillin-resistant E. coli, however, the oscillations dampen initially but then recover within 15–20 minutes.—LKW Cantilever
N-arylamines in yields comparable with the palladium-catalyzed method and avoids the palladium catalyst, phosphine ligand, and organic solvent.—SR
15TH-CENTURY PAINT RECIPES DISCOVERED Most art enthusiasts look at a Renaissance masterpiece and enjoy the painting’s aesthetics. But John K. Delaney, a conservation scientist at the National Gallery of Art, studies artworks’ binders, the material that suspends the pigments and makes up the paint’s bulk. Delaney’s team reports a noninvasive way of mapping the chemical identity of a painting’s binders via an absorption spectroscopy technique common in remote sensing called near-infrared reflectance imaging spectroscopy (Analyst 2013, DOI: 10.1039/c3an00926b). The team showed that a painting made in 1475 by Cosimo Tura used paints that were composed of egg yolk binders, animal skin glue binders, and mixtures of these binders and other ingredients. They showed that the near-IR spectroscopy technique accurately identified the painting’s binders by comparing CEN.ACS.ORG
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their results with results obtained previously via conventional, and destructive, sampling and analysis methods.—SE
ZINC PROTECTS TEA FROM DROUGHT Served over ice with a slice of lemon or hot with milk and a spoonful of sugar, tea is the world’s most popular beverage, after water. So when droughts hit tea-growing regions, such as India and Africa, prices of this prized potable rise. Now, researchers in India have discovered that zinc can ameliorate the effects of drought on tea plants (J. Agric. Food Chem. 2013, DOI: 10.1021/ jf304254z). Hrishikesh Upadhyaya of Karimganj College, along with Biman Kumar Dutta and Sanjib Kumar Panda of Assam University, found that watering Camellia sinensis tea plants with a solution of zinc sulfate followed by a week without water seemed to lessen the harmful effects of the dry spell. Tea plants treated with the zinc solution had greater mass, higher levels of antioxidants, and lower levels of reactive oxygen species after droughtlike conditions as compared with the control group.—BH
ADAPTED FROM NAT. NANOTECHNOL.
STREAMLINING CARBON CAPTURE
