Science Concentrates MICROFLUIDICS
Chemists have prepared fused ferrocene nanorings for the first time, including this six-membered version that is an organometallic analog of benzene.
▸ Diagnostic chip corrals bacteria with sound When a patient develops sepsis, a potentially fatal inflammatory response to an infection, doctors race to identify what bacterial strain is to blame so they can deliver the best antibiotic. This hunt can take days. Now, Thomas Laurell of Lund University and colleagues have developed a microfluidic chip that detects bacteria from a drop of blood within a couple of hours (Anal. Chem. 2016,
To enrichment
To waste
INORGANIC CHEMISTRY
Presenting a ferrocene Ferris wheel By fusing ferrocene molecules together, a research team has prepared new iron-based macrocycles that resemble a Ferris wheel. Ferrocene linear chains and macrocycles have been made before, but they contained spacer groups separating the metallocene units, which don’t allow much interaction between the iron atoms. Michael S. Inkpen, Nicholas J. Long, and Tim Albrecht of Imperial College London and their colleagues have now made examples in which five to nine ferrocene units are fused by direct cyclopentadienyl C–C linkages. These redox-active ferrous/ferric nanorings have substantial charge delocalization and are more stable than previous ferrocene-based macromolecules, with the six-membered version representing an organometallic analog of benzene (Nat. Chem. 2016, DOI: 10.1038/nchem.2553). The researchers made the ferrocene rings via copper-mediated Ullmann coupling reactions of dilute solutions of iodinated ferrocene or linear ferrocene oligomers. The internal cavity of the molecules provides opportunities for host-guest chemistry, and the charge delocalization could lead to electronic and magnetic applications, the researchers say. The team is now investigating more efficient synthetic routes to the macrocycles and methods for derivatizing the rings and potentially linking them together to form large-scale arrays.—STEVE RITTER
500 µm
DOI: 10.1021/acs. In a diagnostic analchem.6b00323). chip (top), sound The device has three waves separate stages. In the first blood cells from two, a piezoceramic the rest of a blood transducer that sample, allowing vibrates like a cell researchers to phone generates direct the cells to standing acoustic a waste chamber waves along the so bacteria can channels. The waves be enriched and focus blood cells detected (inset). into the center of the stream, allowing them to be directed into a waste compartment. The bacteria are too small to notice the sound waves, so they continue to the second stage, where they run into a honeycomb of polystyrene particles. Here, a force created by the sound waves causes the bacteria to stick to the particles. With the bacteria stuck, the remaining
10
C&EN | CEN.ACS.ORG | JULY 4, 2016
blood components wash away. Then the researchers turn off the transducer, releasing the bacteria from the particles so the cells can travel to the third stage where they are identified using a polymerase chain reaction method. The device successfully identified Escherichia coli in half of blood samples from septic patients.—ERIKA GEBEL BERG, spe-
to actinides and efficiently separate them from other nuclear fission by-products, even under harshly acidic and radioactive conditions (J. Am. Chem. Soc. 2016, DOI: 10.1021/jacs.6b03106). Alessandro Casnati
N
cial to C&EN R HO
NUCLEAR CHEMISTRY
▸ Ligands could help recycle nuclear waste Recovering and recycling actinides, such as plutonium, in spent nuclear fuel could potentially reduce nuclear waste and render it nonradioactive. Now researchers report a robust class of ligands that could aid in that recovery process: The ligands bind
1: R = H 2: R = OH
N N
N N N
N R
OH
Researchers designed ligands that bind to actinides and separate them from nuclear waste under harsh industrial conditions.
of the University of Parma, Elena Macerata of the Polytechnic University of Milan, and colleagues designed a series of nitrogen-based ligands with an aromatic backbone that show selectivity for actinides
CREDIT: NAT. CHEM. (NANORINGS); ANAL. CHEM. (CHIP)
To enrichment
over lanthanides, other periodic elements that are produced during fission and contaminate the fuel. The researchers tested the ligands’ binding ability on an organic solution of actinides and lanthanides extracted from samples of nuclear waste. They shook the extract with an aqueous solution of each ligand and allowed the mixture to separate into organic and aqueous layers. After five minutes, the aqueous layer contained almost 95% of the radioactive actinides, bound to the ligands. The ligands maintained their separation performance even while being bombarded with up to 200 kilograys of radiation, which is about 2,000 times the normal amount emitted by spent fuel.—XIAOZHI LIM, special to C&EN
CATALYSIS
▸ Catalyst duo could oxidize biomass alcohols A pair of catalysts can oxidize alcohols electrochemically in a relatively efficient and speedy manner. Such a catalyst system could find use in fuel cells powered by biomass. Organic alcohols are abundant in biomass derived from trees and other plants, and fuel cells could generate electricity by oxidizing
e-
[(bpy)CuII OH]+ + O· N
Electrode
R
OH
TEMPO [(bpy)CuI]+ + OH
R O + H2O
N
CREDIT: SHUTTERSTOCK
Cocatalyzed electrochemical alcohol oxidation generates electricity that could be used to run fuel cells. R = organic group and (bpy)Cu(II) = (2,2′-bipyridine) Cu(II). such alcohols electrochemically. TEMPO (2,2,6,6-tetramethyl-1-piperidine N-oxyl) is an effective catalyst for such oxidations, but it requires running fuel cells at high electrode potentials, which is not energy efficient. Shannon S. Stahl and Artavazd Badalyan at the University of Wisconsin, Madison, have now developed a dual electro-
FOOD
Low-fat chocolate could be a zap away By applying an electric field to melted chocolate, confectioners could alter its microstructure in a way that enables them to reduce the fat content simply and at low cost, according to a study supported in part by Mars Chocolate (Proc. Natl. Acad. Sci. USA 2016, DOI: 10.1073/pnas.1605416113). Chocolate, which can contain as much as 60% fat, is typically processed as a liquid and solidified just before packaging. The liquid is a suspension of roughly 2-µm-wide particles, containing cocoa, sugar, and milk solids, in a base of liquid fat and oil, mainly cocoa butter. Simply removing fat from the suspension concentrates the solids, which causes the liquid to become too viscous to flow through manufacturing equipment. To bypass the viscosity problem, Temple University physicist Rongjia Tao and coworkers applied an electric field to Chocolate can contain up chocolate along the direction it flowed. They to 60% fat, mainly in the found that the process aggregates the partiform of cocoa butter. cles, forming chainlike structures several micrometers in length oriented along the flow direction. This reduced the viscosities of brandname chocolates by 40 to 50%, allowing a roughly 10% reduction in fat and yielding “wonderful tasting chocolate,” Tao says.—MITCH JACOBY
catalyst system that overcomes this problem (Nature 2016, DOI: 10.1038/nature18008). They show that (2,2′-bipyridine)Cu(II) and TEMPO work cooperatively as catalytic redox partners in a two-electron oxidation of alcohols. The two-catalyst oxidations run at a more-efficient electrode potential—a reduction of a half-volt—and are nearly fivefold faster, compared with TEMPO-only reactions. Electrocatalysis expert Shelley D. Minteer of the University of Utah says that the next steps toward incorporating the cocatalysts in a fuel cell are demonstrating their long-term stability and that they can be immobilized on surfaces.—STU BORMAN
CHEMICAL BONDING
▸ All triple bonds are not the same Chemists consider dinitrogen inert because of its strong nitrogen-nitrogen triple bond. But acetylene is reactive, despite its even stronger carbon-carbon triple bond. Molecular orbital theory characterizes both triple bonds as having one σ and two π bonds, each containing a pair of electrons. A new
study explores those triple bonds using generalized valence bond theory and finds differences in their electronic structure that could explain the molecules’ reactivities (J. Phys. Chem. A 2016, DOI: 10.1021/ acs.jpca.6b03631). Lu T. Xu and Thom H. Dunning Jr. of the University of Illinois, Urbana-ChamN N paign, found that the bonding structure H H C C of dinitrogen closely matches the traditional The electronic view from molecstructures of the ular orbital theory. triple bonds in But acetylene’s dinitrogen (top) electronic structure and acetylene includes a signifi(bottom) may be cant contribution the cause of their from excited C–Hs different reactivity. that have three electrons with unpaired spin on each of the carbon atoms. That contribution likely affects acetylene’s reactivity. “Electron spin is usually only explicitly considered when describing radicals and excited states,” Dunning says. But, he says, acetylene shows that how spins couple can be important in ground states too.—JYLLIAN KEMSLEY JULY 4, 2016 | CEN.ACS.ORG | C&EN
11
