Cheap, non-toxic carbon nanodots are going to be quantum dots in the future

CHAMPAIGN, Ill. – Tiny fluorescent semiconductor dots, called quantum dots, are useful in many health and electronic technologies but are made of toxic, expensive metals. Non-toxic and economical carbon-based dots are easy to make, but emit less light. A new study using ultrafast nanometric images found good and bad emissions among numbers of carbon dots. This observation suggests that, by simply selecting super-emitters, carbon nanodots can be purged to replace toxic metal quantum dots in many applications, the researchers said.

The findings, published in the Proceedings of the National Academy of Sciences, brought together researchers from the University of Illinois Urbana-Champaign and the University of Delaware, Baltimore County in a collaborative project through the Beckman Institute for Advanced Science and Technology in Illinois.

“Coming into this study, we didn’t know if all of the carbon dots were just medium emitters or whether some were perfect and some were bad,” Illinois chemistry professor Martin Gruebele said. conduct the study. “We knew that if we could show that there are good ones and bad ones, maybe we could eventually find a way to pick the perfect ones out of the mix.”

Determining whether there are good carbon dots or good light emissions starts with seeing them, Gruebele said. The dots are less than 10 nanometers in diameter and, when excited, decide whether they should fluoresce in a case in picoseconds – or one thousandth of a billionth of a second.

“Using our previously developed single-molecular tunnel microscope, we were only able to design excited states without time resolution,” Gruebele said. “In this study, however, we can now record quantum dots while in an interesting state by combining the true resolution of a nanometer space with a femtosecond time resolution. “

The team found that the energy excitation takes one of two paths: either emit light or turn off the energy as heat before they get fluorescence.

“We have found that, in large numbers, about 20% of a specific population of carbon nanodots are perfect emissions, and about 80% are in a state of light emissions very short before they emit heat, “said Gruebele. “By seeing that there are different numbers we are told that it may be possible to clean up carbon dot numbers by just choosing the perfect light vents.”

The ability to select the perfect dots could realize the concept of efficient carbon-based dots, Gruebele said. “Metal quantum dots are often used to monitor the health of living cells, which are far from ideal, and a non-toxic, economical option would be a major improvement.”

The new imaging technology also allows the researchers to see why some dots do not light up, noting that there is hope that researchers can produce perfect carbon dots that emit put together a light.

“We now know we have an instrument that recognizes the problem,” Gruebele said. “Whether we use it to clean groups of carbon dots or to help synthesize light-emitting carbon dots now, the only question is where do we want to go? forward. “

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This study was supported by Chairman James R. Eiszner in Chemistry, a department of chemistry in Illinois, the National Institute of Biomedical Imaging and Bioengineering, and the National Institute of Heart, Lung, and Blood.

Gruebele is also affiliated with the physics department, the Center for Advanced Study, the Beckman Institute and the Carle Illinois College of Medicine in Illinois.

Editor’s notes:

To reach Martin Gruebele, call 217-333-1624; post-d [email protected].

The paper “Ultrafast nanometric image of energy flow within and between single carbon dots” is available from the U. of Bureau of Press.