Discussion:
Luminescent nanodots are useful materials for cell imaging, optoelectronics and solar cells; however, highly toxic chemicals are needed to prepare these materials, raising concerns over their safety. Now, scientists from Taiwan have developed a less toxic way to create luminescent carbon nanodots by using waste coffee grounds. Photoluminescent quantum dots (QDs) such as CdS and CdSe are good for imaging and sensing because of their high quantum yields, but toxic cadmium species leaching into biological systems is a big concern. Gold and silver nanodots have also shown potential for use as sensors, but their quantum yields are lower and they are more expensive. The advantage of using carbon nanodots (C-dots) over other types of QDs are that they are biocompatible and have good chemical and photostability. The method developed by Huan-Tsung Chang and co-workers from the National Taiwan University, Taipei, takes advantage of a waste feedstock to produce these potentially useful
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Luminescent carbon nanodots from coffee
http://rsc.org/chemistryworld/News/2012/March/carbon-dots-from-waste-coffee.asp