SCIENCE CONCENTRATES Landing Page | April 26, 2004 Issue - Vol. 82 Issue 17 | Chemical & Engineering News
Volume 82 Issue 17 | p. 22 | Concentrates
Issue Date: April 26, 2004

SCIENCE CONCENTRATES

Department: Science & Technology
Credit: SCIENCE © 2004
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Credit: SCIENCE © 2004

Ancient microbes leave ‘tracks’

Scientists have found fossilized traces of ancient microbes in 3.5 billion-year-old lava. Geochemistry professor Harald Furnes at the University of Bergen, in Norway, and colleagues examined the rocks, known as "pillow lava" because of their puffy shapes, from the Barberton Greenstone Belt in South Africa [Science, 304, 578 (2004)]. The micrometer-sized tubules etched as the microbes tunneled through the lava are clearly visible (shown). Inside the tube walls is carbon, which the researchers judge to be of biogenic origin partly because the carbon is not bound in carbonate. This phenomenon has been studied in much younger rocks, but now researchers have new options for further investigating the earliest life on Earth.

Nanoparticles in ionic liquids

A simple process for obtaining well-defined metal nanoparticles in ionic liquids has been described by chemists in Taiwan. Associate professor Guor-Tzo Wei and coworkers at National Chung Cheng University, in Chia-Yi, transferred gold nanoparticles from an aqueous solution to the water-immiscible ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate by vigorously shaking the biphasic mixture [J. Am. Chem. Soc., 126, 5036 (2004)]. "To our knowledge, this is the first example of using a room-temperature ionic liquid as the medium in phase transfer of metal nanoparticles," Wei says. The researchers prepared the aqueous solution of gold nanoparticles by reducing a solution of HAuCl4 with citrate. Transmission electron microscopy images of the nanoparticles before and after phase transfer revealed that their size does not change. Similarly, TEM images of gold nanorods showed that the shape of the nanorods is preserved following phase transfer to the ionic liquid. "The advantage of this process over other phase transfer processes is that no capping agent, such as thiol or amine, is required for phase transfer," Wei notes. The group has also shown that the process can be applied to the phase transfer of nanoparticles of other metals, such as palladium, to ionic liquids. "We are now using the process to explore the potential for extracting environmental nanopollutants," Wei says.

Green tea meets green machining

The unlikely combination of green tea and computer components is usually the unfortunate result of a spill. But Ventana Research hopes to make a more amicable match between the two with its green-tea-based slurry for polishing computer hard-drive components. The South Tuscon, Ariz.-based company makes the machining fluid by combining green tea and plant extracts with synthetic proteins derived from common commercial chemicals. The fluids are used to bind polishing debris and remove tiny particles from the polishing surface—a critical step for making high-quality hard-drive read-write heads. According to Ventana, not only is the biodegradable fluid more environmentally friendly than its industry-standard counterparts, it is also three to four times more effective. Furthermore, the fluid is cost competitive with other machining fluids because its plant-derived chemicals are both abundant and easy to extract.

Rf matches up as a group 4 element

Rutherfordium fluoride distribution coefficients measured by a rapid chromatographic method have provided stronger evidence that the chemistry of element 104 matches that of its lighter group 4 homologues zirconium and hafnium when relativistic effects are considered. An international team of scientists led by Hiromitsu Haba of Japan's Atomic Energy Research Institute, in Tokai, carried out the experimental studies along with relativistic molecular orbital calculations [J. Am. Chem. Soc., 126, 5219 (2004)]. The team generated short-lived 85Zr, 169Hf, and 261Rf isotopes that were dissolved in HF solution, eluted one at a time through an automated chromatography system, and identified by spectroscopy. The distribution coefficient for Rf on the ion-exchange column is significantly less than that of Zr and Hf, the researchers note, a difference not observed in previous Rf studies carried out with HCl or HNO3. They deduced that Zr, Hf, and Rf form MF62- complexes at low HF concentrations, but ZrF73- and HfF73- are formed at high HF concentration. The lower distribution coefficient and coordination number for Rf suggest that relativistic effects, which can alter usual electron configurations and oxidation states of heavier elements, influence the strong complexing ability of the fluoride ion.

Nanoparticle pictures in 3-D

Credit: ANGEWANDTE CHEMIE PHOTO
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Credit: ANGEWANDTE CHEMIE PHOTO

Using a focused femtosecond laser, researchers can make detailed, 3-D images inside Au2O3-doped silicate glass (shown) [Angew. Chem. Int. Ed., 43, 2230 (2004)]. Shanghai Institute of Optics & Fine Mechanics' Jianrong Qiu and colleagues developed the two-step process. First, the group irradiates the doped glass with a laser, essentially using the beam to draw pictures or patterns within the glass. The high-energy irradiation reduces the gold ions to gold atoms through a multiphoton process and forms tiny, gray dots wherever the beam strikes the glass. The scientists then anneal the glass at 550 ºC, causing the gold atoms to precipitate and form gold nanoparticles. Depending upon the size of the nanoparticle, the gray patterned areas will turn violet, red, or yellow after annealing. The group can control the nanoparticles' size by varying the irradiation conditions and can "erase" the drawing after the first step by annealing at a lower temperature. Qiu's team hopes to use the technique to make 3-D gold nanocircuits.

 

 
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