NEUROSCIENCE
3-D PRINTING
▸ Understanding
Silver ink flies in 3-D metal writing
‘chemo brain’ About 30% of cancer patients who receive chemotherapy later suffer from so-called chemo brain, a condition characterized by memory loss, attention deficits, and decreased problem-solving abilities. Scientists know little about how anticancer drugs lead to this cognitive decline. But a new study reports that treating rats with the drug carboplatin impairs the release of dopamine and serotonin, which are neurotransmitters that play key roles in many cognitive functions affected by chemo brain (ACS Chem. Neurosci. 2016, DOI: 10.1021/acschemneuro.5b00029). Michael A. Johnson of the University of Kansas and colleagues observed that rats receiving carboplatin injections for four weeks performed slightly worse in a test of spatial memory than did animals receiving just saline solution. When the team studied brain slices from the carboplatin-treated rats, they found that dopamine and serotonin release had decreased by 42% and 55%, respectively, compared with slices from rats getting saline. However, the total amount of dopamine and serotonin within neurons did not differ, suggesting that carboplatin treatment didn’t alter production of the neurotransmitters but instead affected the ability to release the neurotransmitters into synapses, Johnson says.—MICHAEL TORRICE
CATALYSIS
CREDIT: JAMES WEAVER (BUTTERFLIES)
▸ Core-shell nanocatalysts stretch out noble metals The high cost of noble metals often drives researchers to seek more efficient ways of using them to make catalysts for applications such as fuel cells and catalytic converters. One team’s effort has led to a procedure for preparing nanoparticle catalysts consisting of an atomically thin noble-metal shell wrapped around an inexpensive metal-carbide core (Science 2016, DOI: 10.1126/ science.aad8471). Sean T. Hunt and Yuriy Román-Leshkov of MIT and coworkers treated tungsten oxide nanoparticles with (NH4)2PtCl6 and encapsulated the particles with silica nanospheres. They then subjected the material to a mixture of methane and hydrogen while gradually raising the temperature to 900 °C. At the lowest tem-
When Mark A. Skylar-Scott says he Harvard researchers used their new and his Harvard University colleagues metal-writing technique to create can make metal filaments in midair, he these 3-D silver butterflies, which stresses that they aren’t defying gravity. are about 2 mm wide. The team’s silver strands start attached to a substrate, but the researchers can draw them out through three-dimensional space to create intricate patterns. Led by Skylar-Scott and Jennifer A. Lewis, the researchers are forging the 3-D silver wires on demand using a nanoparticle ink and laser light (Proc. Natl. Acad. Sci. USA 2016, DOI: 10.1073/pnas.1525131113). The approach could help create custom transmitters and electrical connections for biosensors and other miniaturized devices, the researchers say. The ink consists of silver nanoparticles mixed with polyacrylic acid. The polymer chains prevent the silver particles from clumping while also serving as a binder to give the ink the consistency of toothpaste, Skylar-Scott says. A computer-controlled nozzle moves in 3-D to squeeze the ink into the focal point of an infrared laser, which moves in concert with the nozzle. The laser’s heat vaporizes the polymer and sinters the nanoparticles into a solid metal wire. This laser-assisted method enables the team to directly write wire patterns onto low-cost substrates that can’t support conventional high-temperature annealing.—MATT DAVENPORT
peratures, platinum nanoclusters formed on tungsten oxide. As things heated up, the surface material transitioned into mixtures of platinum and tungsten and then to platinum and tungsten carbide. Because noble metals are insoluble in transition-metal carbides, the platinum segregated and formed a shell around a tungsten carbide core. The team also devised mixed-metal shells and cores. Methanol electrooxidation tests show that platinum-ruthenium- and Pt-coated tungsten titanium carbide catalysts are more stable and 10 times as active as current commercial catalysts.—MITCH JACOBY
ORGANIC SYNTHESIS
Aryl fluorosulfonates set new electrophile standard ▸
mental chemistry is hard to do, yet Patrick S. Hanley and coworkers at Dow Chemical have reported a breakthrough by developing an in situ method for generating aryl fluorosulfonates as alternative electrophiles in aminations (ACS Catal. 2016, DOI: 10.1021/ acscatal.6b00865). The Dow team and other research groups previously reported using premade aryl fluorosulfonates for Suzuki couplings with aryl boronates. But the team’s one-pot amination method goes further. The researchers treated phenols with sulfuryl fluoride and a base at room temperature followed by addition of an amine coupling partner to create amination products. They found that aryl fluorosulfonates outperform other common electrophiles. In addition, the phenols can be sourced from biobased materials that are less expensive and more sustainable than petroleum-derived reagents, and the reactions can be carried out with a palladium or a nickel catalyst. The Dow researchers are now considering how to take advantage of this underexplored class of electrophile for preparing specialty chemicals, Hanley says.—STEVE RITTER
Palladium-catalyzed amination in which an aryl halide or aryl triflate electrophile is coupled with an aryl or NH2 H alkyl amine is one OH SO F O S F N 2 2 of the most popular Base Pd or Ni O O reactions in organic catalyst R R R chemistry. Streamlining this fundaOne-pot sulfuryl fluoride amination of phenols
MAY 23, 2016 | CEN.ACS.ORG | C&EN
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