Electrodes a few atoms wide made at Caltech
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News of the Week tion Division for consideration. The end result was last week's complete approval of the patent. U.S. patents were awarded in 1985 to both Biogen and Hoffmann-La Roche, which developed α-interfer- ons with Genentech. Roche and Schering-Plough, in what was called the defusing of a potentially major biotechnology patent fight, agreed not to sue each other over manufac- turing and sales of α-interferons worldwide, except in Japan. A new catalyst that converts meth- ane to C 2 hydrocarbons, with nearly 100% selectivity at atmospheric pres- sure and moderate temperatures, has been developed at Lawrence Berke- ley Laboratory. The reaction appears to be strictly catalytic and there are no carbon oxides formed, thereby ruling out gas-phase reactions. At present, the per-pass conversion is about 10% and steam is required in the conversion. Described recently in Catalysis Let- ters [6, 255 (1990)], the work was car- ried out at Lawrence Berkeley Labo- ratory's Center for Advanced Mate- rials by a research team that included chemists Heinz Heine- mann, Gabor A. Somorjai, Pedro Pereira, and S. H. Lee. It was funded by the U.S. Department of Energy's Office of Fossil Energy. Direct con- version of methane to higher hydro- carbons, particularly light olefins, is being pursued in catalytic research labs around the world. The new catalyst is a calcium, nickel, and potassium mixed oxide system requiring great care in prep- aration. Slight variations in the preparation produce materials with very different properties. The best experimental runs were done at 600 °C and 1 atm total pressure. Meth- ane conversion was 10%, and the se- lectivity to C 2 hydrocarbons was greater than 97%. The catalyst sur- face composition appears to be Ca:- Ni:K in a ratio of 2:1:0.1. A mechanism for direct methane conversion that has been proposed in the literature for previous tech- niques is one of methane oxidative dimerization in the presence of alka- li-earth oxide at high temperatures. The α-interferon market is shared by Roche and Schering-Plough, which market their products as Ro- feron-A and Intron A, respectively. Intron A sales by Schering-Plough, which says it has a majority share of the world market, nearly doubled between 1988 and 1989 to about $90 million. Analysts have projected that the company's worldwide sales for α-interferon will exceed $150 million in 1990. Ann Thayer The active species here is the meth- yl free radical that reacts almost ex- clusively in the gas phase. For ther- modynamic reasons, carbon oxides form. In the new reaction system, a dif- ferent mechanism is at work. The re- search team believes the active ad- sorbed species from methane forms on the catalyst surface at the low temperatures employed. Conse- quently, there is no carbon oxide formation. The reacting system typically in- cludes methane, oxygen, and steam in the ratio of 3:1:6.5. The role of the steam is still not understood and is under study. Joseph Haggin Electrodes a few atoms wide made at Caltech Electrodes as small as 10 Â in radi- us—the width of about four plati- num atoms—have been fabricated by Reginald M. Penner, Michael J. Heben, Teresa L. Longin, and Nathan S. Lewis of California Insti- tute of Technology [Science, 250, 1118 (1990)]. Ultramicroelectrodes used in elec- trochemistry have been made as small as 0.1 μια (1000 Â) in radius. However, the new electrodes, called nanodes, are as much as two orders of magnitude smaller. To make the nanodes, Lewis and coworkers use a cyanide solution to etch a platinum or platinum-iridium wire to a sharp point. The sharp- ened wire is then drawn through a droplet of molten glass, coating Nanode forms when glass coats sharpened Pt or Pt-Ir wire but leaves tip exposed most of the wire with an insulating glass layer but leaving an exposed area of controllable, variable size at the tip. "Think of the electrode as a pencil," says Lewis, "with pencil in- sulation everywhere but at the very tip." The tiniest such electrodes are "so small we can't find them with a scanning electron microscope," says Lewis, "so we can't measure their size directly." Instead, the research- ers estimate the size of the smallest nanodes mathematically from volta- metric data. The nanodes extend the range of measurable electron-transfer rate constants to values that are two or- ders of magnitude faster than those accessible with other techniques. Compared with a nanode of 10-A ra- dius, a hypothetical electrode com- posed of a single platinum atom would be capable of measuring rate constants that are only about six times faster. Nanodes might also prove advan- tageous in several other applica- tions. They could make it possible to observe chemical processes on a more localized scale and to deposit narrower metal lines on semicon- ductor surfaces, using scanning mi- croscopy techniques. In neurophysi- ological studies, they could make it easier to detect neurotransmitters in single nerve cells. In electrochemi- cal experiments, smaller electrodes provide better rejection of back- ground currents. In addition, na- nodes might provide higher resolu- tion flow detection for chromatogra- phy and electrophoresis. Stu Borman Catalyst converts methane to C> hydrocarbons 8 November 26, 1990 C&EN
Transcript of Electrodes a few atoms wide made at Caltech
News of the Week
tion Division for consideration. The end result was last week's complete approval of the patent.
U.S. patents were awarded in 1985 to both Biogen and Hoffmann-La Roche, which developed α-interferons with Genentech. Roche and Schering-Plough, in what was called the defusing of a potentially major biotechnology patent fight, agreed not to sue each other over manufacturing and sales of α-interferons worldwide, except in Japan.
A new catalyst that converts methane to C2 hydrocarbons, with nearly 100% selectivity at atmospheric pressure and moderate temperatures, has been developed at Lawrence Berkeley Laboratory. The reaction appears to be strictly catalytic and there are no carbon oxides formed, thereby ruling out gas-phase reactions. At present, the per-pass conversion is about 10% and steam is required in the conversion.
Described recently in Catalysis Letters [6, 255 (1990)], the work was carried out at Lawrence Berkeley Laboratory's Center for Advanced Materials by a research team that included chemists Heinz Heine-mann, Gabor A. Somorjai, Pedro Pereira, and S. H. Lee. It was funded by the U.S. Department of Energy's Office of Fossil Energy. Direct conversion of methane to higher hydrocarbons, particularly light olefins, is being pursued in catalytic research labs around the world.
The new catalyst is a calcium, nickel, and potassium mixed oxide system requiring great care in preparation. Slight variations in the preparation produce materials with very different properties. The best experimental runs were done at 600 °C and 1 atm total pressure. Methane conversion was 10%, and the selectivity to C2 hydrocarbons was greater than 97%. The catalyst surface composition appears to be Ca:-Ni:K in a ratio of 2:1:0.1.
A mechanism for direct methane conversion that has been proposed in the literature for previous techniques is one of methane oxidative dimerization in the presence of alkali-earth oxide at high temperatures.
The α-interferon market is shared by Roche and Schering-Plough, which market their products as Ro-feron-A and Intron A, respectively. Intron A sales by Schering-Plough, which says it has a majority share of the world market, nearly doubled between 1988 and 1989 to about $90 million. Analysts have projected that the company's worldwide sales for α-interferon will exceed $150 million in 1990.
Ann Thayer
The active species here is the methyl free radical that reacts almost exclusively in the gas phase. For thermodynamic reasons, carbon oxides form.
In the new reaction system, a different mechanism is at work. The research team believes the active adsorbed species from methane forms on the catalyst surface at the low temperatures employed. Consequently, there is no carbon oxide formation.
The reacting system typically includes methane, oxygen, and steam in the ratio of 3:1:6.5. The role of the steam is still not understood and is under study.
Joseph Haggin
Electrodes a few atoms wide made at Caltech Electrodes as small as 10 Â in radius—the width of about four platinum atoms—have been fabricated by Reginald M. Penner, Michael J. Heben, Teresa L. Longin, and Nathan S. Lewis of California Institute of Technology [Science, 250, 1118 (1990)].
Ultramicroelectrodes used in electrochemistry have been made as small as 0.1 μια (1000 Â) in radius. However, the new electrodes, called nanodes, are as much as two orders of magnitude smaller.
To make the nanodes, Lewis and coworkers use a cyanide solution to etch a platinum or platinum-iridium wire to a sharp point. The sharpened wire is then drawn through a droplet of molten glass, coating
Nanode forms when glass coats sharpened Pt or Pt-Ir wire but leaves tip exposed
most of the wire with an insulating glass layer but leaving an exposed area of controllable, variable size at the tip. "Think of the electrode as a pencil," says Lewis, "with pencil insulation everywhere but at the very tip."
The tiniest such electrodes are "so small we can't find them with a scanning electron microscope," says Lewis, "so we can't measure their size directly." Instead, the researchers estimate the size of the smallest nanodes mathematically from volta-metric data.
The nanodes extend the range of measurable electron-transfer rate constants to values that are two orders of magnitude faster than those accessible with other techniques. Compared with a nanode of 10-A radius, a hypothetical electrode composed of a single platinum atom would be capable of measuring rate constants that are only about six times faster.
Nanodes might also prove advantageous in several other applications. They could make it possible to observe chemical processes on a more localized scale and to deposit narrower metal lines on semiconductor surfaces, using scanning microscopy techniques. In neurophysi-ological studies, they could make it easier to detect neurotransmitters in single nerve cells. In electrochemical experiments, smaller electrodes provide better rejection of background currents. In addition, nanodes might provide higher resolution flow detection for chromatography and electrophoresis.
Stu Borman
Catalyst converts methane to C> hydrocarbons
8 November 26, 1990 C&EN
