Scientists with the University of Chicago have demonstrated a way to create infrared light using colloidal quantum dots. The researchers said the method demonstrates great promise; the dots are already as efficient as existing conventional methods, even though the experiments are still in early stages.

The dots could someday form the basis of infrared lasers as well as small and cost-effective sensors, such as those used in exhaust emissions tests or breathalyzers.

“Right now the performance for these dots is close to existing commercial infrared light sources, and we have reason to believe we could significantly improve that,” said Philippe Guyot-Sionnest, a professor of physics and chemistry at the University of Chicago, member of the James Frank Institute, and one of three authors on the paper published in Nature Photonics. “We’re very excited for the possibilities.”

The right wavelength
Colloidal quantum dots are tiny crystals—you could fit a billion into the period at the end of this sentence—that emit different colors of light depending on how big you make them. They’re very efficient and easy to make and are already being used in commercial technology; you might already have bought a quantum-dot TV without knowing it.

However, those quantum dots are being used to make light in the visible wavelength—the part of the spectrum humans can see. If you wanted quantum dot light in the infrared wavelength, you’ve mostly been out of luck.

But infrared light has a lot of uses. In particular, it is very useful for making sensors. If you want to know whether harmful gases are coming out of your car exhaust, or test whether your breath is above the legal alcohol limit, or make sure methane gas isn’t coming out of your drill plant, for example, you use infrared light. That’s because different types of molecules will each absorb infrared light at a very specific wavelength, so they’re easy to tell apart.

“So a cost-effective and easy-to-use method to make infrared light with quantum dots could be very useful,” explained Xingyu Shen, a graduate student and first author on the new study.