NEWS OF THE WEEK NANOSCIENCE
SHIP IN A BOTTLE SEEING SPOTS TEM image and corresponding model of a Gd atom (blue) lodged at the oxidized tip of a n a n o h o r n .
Metal clusters are grown inside a nanohorn through a hole in its side I T S NOT JUST BECAUSE CARBON ly control the size and location of
nanotubes usually are empty I that researchers try to trap
atoms or molecules inside them. Scientists suspect that nanotubes filled with metal atoms could have promising applications as catalysts and semiconductors. Now, a research group injapan has devised a method to precise-
metal clusters within a singlewalled carbon nanohorn—a megaphone-shaped type of nanotube [Proc. Natl. Acad. Sci. USA, 101, 8527 (2004)}. University of Tokyo chemistry professor Eiichi Nakamura and Sumio Iijima of N E C Corp. andjapan's Research Center for Advanced Carbon Materials spearheaded the research. To construct the metal-encapsulated structures, the group begins by heating the nanohorns at 420 to 580 °C in the presence of 0 2 . Under these conditions, the nanohorns become pierced and the edges ofthe new openings are oxidized, creating small regions
AWARDS
NSF Bestows Teaching And Research Honors
T
he National Science Foundation will semble items such as photocopiers to learn present eight educators with the Direcengineering concepts. tor's Award for Distinguished Teaching Susan E. Powers, civil and environmental Scholars at a ceremony on June 2. The recipiengineering professor at Clarkson University, ents, who are being honored for excellence in Potsdam, N.Y., concentrates on the transport both teaching and research, will each receive of contaminants in subsurface environments. a grant worth about $300,000. She directs a program that brings graduate students into elementary and secondary Four of the award winners have ties to schools to help with instruction. chemistry or chemical engineering. Walter C. Oechel, a biology professor who heads the Julio J. Ramirez, a psychology professor Global Change Research Group at San Diego and neuroscientist at Davidson College, State University, studies factors that affect productivity and growth of plants and ecosystems, including C02 regulation and balance. He will use his grant to design Webbased lessons on climate change. Oechel Ollis Powers Ramirez David F. Ollis, a ~" chemical engineering professor at North Davidson, N.C., investigates the recovery of Carolina State University, Raleigh, is interestmemory after injury to the central nervous ed in biotechnology and photocatalysis. Ollis, system. His grant will help support a sumwho is a proponent of hands-on learning, has mer research program in neuroscience for created a course in which freshmen disasundergraduates.—SOPHIE R0VNER
of hydrophilicity in the hydrophobic graphene structure. W h e n the perforated nanohorns are placed in a methanolic solution with Gd(OAc) 3 (H 2 0) 4 , the hydrophilic Gd(III) ions accumulate one by one at the oxidized openings. The researchers expect that other metal ions will behave in a similar fashion. By observing this process, they conclude that the size and location of the opening ultimately determine how many metal ions will aggregate there and whether they will be encapsulated by the tube. "Thanks to the availability of the first scanning transmission electron microscope (STEM) capable of performing high-resolution electron energy loss spectrometry for a 3- X 3-Â area, we could identify for the first time, metals trapped within the graphene wall or within the interior of the nanohorn," Nakamura says. The group noted that metal ions won't travel through openings at the tapered tips of a nanohorn, but instead, a lone atom can become lodged there. However, metal clusters will form inside the structure if the opening is in t h e nanohorn's side. There, a cluster of metal ions will develop inside the tube until the aggregate extends to the internal hydrophobic wall opposite the opening. T h e researchers call the technique a "ship-in-bottle" synthesis. "The impact of such a technique lies in our ability to control defect dynamics in nanotube structures and hence controllably create hybrid nanotube-based structures," comments Pulickel M. Ajayan, a materials engineering professor at Rensselaer Polytechnic Institute, Troy Ν . Υ He describes the report as "a very nice demonstration ofhow in situ microscopy can be used to reveal real-time events and follow the dynamics ofreactions, defect cre ation, and encapsulation. Kudos go to the masterly microscopy and amazingly clear images."— BETHANY HALFORD
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