LEDs Made from Food Waste

Michael Free (left) holds a light emitting diode and Prashant Sarswat (right) holds carbon dots in suspension.

Michael Free (left) holds a light emitting diode and Prashant Sarswat (right) holds carbon dots in suspension.

The list of ways engineers have turned trash into treasure just continues to grow. Over the last year, engineers have turned garbage into batteries, fuel, supercapacitors, and now—LED lights. Two engineers at the University of Utah created the building blocks for LEDs (light emitting diodes) from food and beverage waste. The benefits are twofold: the new method takes advantage of material that would otherwise be wasted, while also reducing the toxic elements in traditional LEDs.

In the experiment, the engineers turned waste material into quantum dots (QDs), which are luminescent nanocrystals that can be used to make LEDs (they are especially popular for making the newest televisions). Specifically, the team refined bread, tortillas, and soda into carbon dots (CDs) to create LEDs. First, the food and drinks were placed into a solvent under pressure and high temperature until CDs were formed. Next, the engineers had to determine the size of the dots, which correlates to their intensity of color and brightness. This was especially challenging since they are so small—you could fit 4,000 of CDs on the width of a human hair. To observe and measure the dots, the team illuminated them and performed several tests: Fourier transform infrared spectroscopy, x-ray photoelectron spectroscopy, as well as Raman and AFM imaging. Finally, the best CDs were suspended in epoxy resins, heated and hardened to solidify them for practical use in LEDs.

In the end, sugary soft drinks produced the bestCDs. Carbon dots made from food and beverage waste could provide an inexpensive and environmentally-friendly alternative to the toxic materials that are used in today’s LEDs. “QDs derived from food and beverage waste are not based on common toxic elements such as cadmium and selenium, which makes their processing and disposal more environmentally friendly than it is for most other QDs.  In addition, the use of food and beverage waste as the starting material for QDs allows for reduced waste and cost to produce a useful material,” said researcher Michael Free.

Source: University of Utah | Photo credit: Prashant Sarswat

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