Jul 17, 2002
CdTe nanowires make themselves up
Scientists from Oklahoma State University, US, and the Hahn-Meitner-Institut in Germany have developed a new technique for creating semiconductor nanowires. The researchers used nanoparticles of CdTe that spontaneously self-assembled into crystalline nanowires.
"The process of self-assembly is unique," Nicholas Kotov of Oklahoma State University told nanotechweb.org. "It demonstrates that there are long-range forces between the nanoparticles. Additionally, the nanowires that are produced have strong luminescence, which is a pertinent feature for many photonic devices - for instance, sensors."
As a starting point, the team used CdTe nanocrystals stabilized by thioglycolic acid. The scientists removed the stabilizer and then left the crystals in darkness at room temperature for several days. As a result, the nanoparticles reorganized into chains and then recrystallized into nanowires. Kotov says that preparing nanowires in aqueous media in this way is much safer and more convenient than using organic solvents.
The nanowires were uniform in diameter and exhibited good optical properties. The researchers found that they could determine both the diameter and luminescence of the wires by changing the size of the initial nanoparticles. The team made green nanowires, which were 2.5 nm in diameter, yellow nanowires 3.5 nm in diameter, orange nanowires with a diameter of 4.2 nm, and 5.6 nm diameter red nanowires. The green nanowires had luminescence quantum yields as high as 29%.
The scientists, who reported their work in Science, also made CdSe nanowires using a similar process.
"The process is easy to realize in a commercial setting, although we are still quite far - more than 5 years - from the first commercial nanowire device," added Kotov. He says that since one of the most obvious applications of the nanowires is nanoelectronics, the plan now is to organize them first in 2D and then in 3D space.
About the author
Liz Kalaugher is editor of nanotechweb.org.