Lightbulb moment for food waste

Chemists have found a way to create light emitting diodes – which can efficiently convert electricity to light – from food and beverage waste.

A research team at the University of Utah synthesised food, beverage, and combustion wastes and produced fluorescent semiconductor nanoparticles – quantum dots – in the form of luminescent carbon dots (CDs) which were then turned into LEDs.

“Synthesising and characterising CDs derived from waste is a very challenging task. We essentially have to determine the size of dots which are only 20nm or smaller in diameter, so we have to run multiple tests to be sure CDs are present and to determine what optical properties they possess,” said team leader Professor Prashant Sarswat.

In the study, published in Physical Chemistry Chemical Physics, the team used solvothermal synthesis on soft drinks, pieces of bread and tortilla. The waste was placed into a solvent under high pressure and temperature until CDs were formed. Then they illuminated the formed traces of CDs, monitored their formation and colour and found that sugars, sucrose and D-fructose, found in soft drinks, are the most effective sources for production of CDs. To create LEDs the team heated and hardened the CDs.

Currently, one of the most common sources of quantum dots is cadmium selenide, a compound comprised of a two toxic elements. The scientists believe this method to create quantum dots in the form of CDs will not only eliminate the concern over toxic waste but will also lower the cost.

“With food and beverage waste that are already there, our starting material is much less expensive. In fact, it’s essentially free,” said Professor Sarswat.

Next, the team will continue to study the produced LEDs from food and beverage waste for stability and long term performance.

“The ultimate goal is to do this on a mass scale and to use these LEDs in everyday devices. To successfully make use of waste that already exists, that’s the end goal,” added Professor Sarswat.