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Bright Lights of Purity: Berkeley Lab Researchers Discover Why Pure Quantum Dots and Nanorods Shine…
Please note, release from US government laboratory. (Copyright concerns are nil.)
http://newscenter.lbl.gov/feature-stories/2012/01/30/nanocrystal-luminescence/
[font face=Times, Serif][font size=5]Bright Lights of Purity:[/font]
[font size=4]Berkeley Lab Researchers Discover Why Pure Quantum Dots and Nanorods Shine Brighter[/font]
January 30, 2012
Lynn Yarris (510) 486-5375 lcyarris@lbl.gov
[font size=3]To the lengthy list of serendipitous discoveries – gravity, penicillin, the New World – add this: Scientists with the U.S. Department of Energy (DOE)’s Lawrence Berkeley National Laboratory (Berkeley Lab) have discovered why a promising technique for making quantum dots and nanorods has so far been a disappointment. Better still, they’ve also discovered how to correct the problem.
A team of researchers led by chemist Paul Alivisatos, director of Berkeley Lab, and Prashant Jain, a chemist now with the University of Illinois, has discovered why nanocrystals made from multiple components in solution via the exchange of cations (positive ions) have been poor light emitters. The problem, they found, stems from impurities in the final product. The team also demonstrated that these impurities can be removed through heat.
“By heating these nanocrystals to 100 degrees Celsius, we were able to remove the impurities and increase their luminescence by 400-fold within 30 hours,” says Jain, a member of Alivisatos’ research group when this work was done. “When the impurities were removed the optoelectronic properties of nanocrystals made through cation-exchange were comparable in quality to dots and nanorods conventionally synthesized.”
Says Alivisatos, “With our new findings, the cation-exchange technique really becomes a method that can be widely used to make novel high optoelectronic grade nanocrystals.”
…
As Jain tells the story, he was in the process of disposing of CdSe/CdS nanocrystals in solution that were six months old when out of habit he tested the nanocrystals under ultraviolet light. To his surprise he observed significant luminescence. Subsequent spectral measurements and comparing the new data to the old showed that the luminescence of the nanocrystals had increased by at least sevenfold.
…[/font][/font]
http://dx.doi.org/10.1002/ange.201107452[font size=4]Berkeley Lab Researchers Discover Why Pure Quantum Dots and Nanorods Shine Brighter[/font]
January 30, 2012
Lynn Yarris (510) 486-5375 lcyarris@lbl.gov
[font size=3]To the lengthy list of serendipitous discoveries – gravity, penicillin, the New World – add this: Scientists with the U.S. Department of Energy (DOE)’s Lawrence Berkeley National Laboratory (Berkeley Lab) have discovered why a promising technique for making quantum dots and nanorods has so far been a disappointment. Better still, they’ve also discovered how to correct the problem.
A team of researchers led by chemist Paul Alivisatos, director of Berkeley Lab, and Prashant Jain, a chemist now with the University of Illinois, has discovered why nanocrystals made from multiple components in solution via the exchange of cations (positive ions) have been poor light emitters. The problem, they found, stems from impurities in the final product. The team also demonstrated that these impurities can be removed through heat.
“By heating these nanocrystals to 100 degrees Celsius, we were able to remove the impurities and increase their luminescence by 400-fold within 30 hours,” says Jain, a member of Alivisatos’ research group when this work was done. “When the impurities were removed the optoelectronic properties of nanocrystals made through cation-exchange were comparable in quality to dots and nanorods conventionally synthesized.”
Says Alivisatos, “With our new findings, the cation-exchange technique really becomes a method that can be widely used to make novel high optoelectronic grade nanocrystals.”
…
As Jain tells the story, he was in the process of disposing of CdSe/CdS nanocrystals in solution that were six months old when out of habit he tested the nanocrystals under ultraviolet light. To his surprise he observed significant luminescence. Subsequent spectral measurements and comparing the new data to the old showed that the luminescence of the nanocrystals had increased by at least sevenfold.
…[/font][/font]