Scientists from Japan's Nagoya Institute of Technology discovered a new method for converting fish waste into extremely high-quality carbon nano-onions (CNOS). The new advancement could result in lower-cost next-generation LED lighting and QLED displays.
CNOs are a type of carbon-based nanomaterial that is low in toxicity, has good chemical stability, and has good electrical and optical properties. They are made up of concentric shells of fullerenes that look like cages within cages. Their main advantage over other carbon-based nanomaterials is their large surface area, as well as their high electrical and thermal conductivities.
Attempts to manufacture CNOs have encountered significant challenges since their discovery in the 1980s. For example, some CNOs require high temperature or vacuum conditions during the manufacturing process. Others take an inexorably long time to produce.
The Nagoya Institute of Technology team describes their simple new method for converting fish waste into CNOs in a new study published in the journal Green Chemistry. The researchers devised a method for converting fish scales extracted from fish waste into CNOs in a matter of seconds. Microwave pyrolysis is the key to this.
Interestingly, the researchers are still looking into the reason for their discovery - they don't yet fully understand why fish scales can be converted into CNOs so easily. What they do know is that it could be due to the collagen in fish scales absorbing enough microwave radiation to cause a rapid rise in temperature. This, in turn, causes thermal decomposition, also known as "pyrolysis." Pyrolysis generates gases that aid in the formation of CNOs.
The new method is impressive in that it does not require high temperatures or complex catalysts and takes only 10 seconds. According to the researchers' paper, the process also produces CNOs with extremely high crystallinity, which is extremely rare for processes involving biomass waste.
The researchers also mention that their method generates CNOs that are selectively and thoroughly functionalized with (COOH) and (OH) groups. One of the advantages of their CNOs' functionalization and high crystallinity is that they have excellent optical properties.
Associate Professor Takashi Shirai, who worked on the new study, stated, "CNOs emit ultra-bright visible light with a 40 percent efficiency (or quantum yield). This value, which has never been achieved before, is approximately ten times greater than that of previously reported CNOs synthesized using conventional methods."
The efficiency of their fish-based CNOs was demonstrated in the lab by using them in LEDs and blue-light-emitting thin films. They claimed to have produced a highly stable emission. "The stable optical properties may allow us to fabricate large-area emissive flexible films and LED devices," Dr. Shirai explained.
These discoveries will pave the way for the development of next-generation displays and solid-state lighting. Not only would using fish waste be a more environmentally friendly way of producing electronics, but it could also lower production costs for next-generation displays.
