The world hasn’t quite figured out what to do with the millions of tonnes of its plastic waste, Scientists estimate that only 9 percent of plastic waste is recycled. Another 12 percent ends up burnt in incinerators. The plastics industry is turning to new chemical recycling technologies as a seeming answer to our plastic woes. But these technologies are far from a haven and instead they create problems of their own.
Researchers have now turned to a new tool in the fight against plastic waste: lasers. By zapping plastic with laser pulses, engineers from the University of Austin and Tohoku University break down plastic molecules into its elemental building blocks, and produce useful carbon nanomaterials.
Plastics are long, tough chains of molecules strung together like beads in a necklace. Those organic molecules are made of various elements such as carbon, oxygen, hydrogen, and nitrogen.
The new work, reported in the journal Nature Communications, focuses on a reaction called C–H activation, in which the bonds between the carbon and hydrogen atoms are selectively broken and transformed into new chemical bonds.
The key to the method’s success is another material that is only atoms-thick. This two-dimensional material is known as a transition metal dichalcogenide onto which the researchers first layer plastic before laser-treatment. When exposed to the low-power laser light, this 2D material triggers the C–H activation reaction, which frees carbon and hydrogen.
The hydrogen atoms bond to each other to form hydrogen that is released as gas. And the carbon atoms bond with each other to form tiny nanosized crystals known as carbon dots that are luminescent. These carbon dots could potentially be used as memory storage devices in next-generation computer devices.
The researchers used low-power light to break the chemical bonding of the plastics and create new chemical bonds that turned the materials into luminescent carbon dots. Carbon-based nanomaterials are in high demand because of their many capabilities, and these dots could potentially be used as memory storage devices in next-generation computer devices.
In a press release, the team says that they will need to do further research and development to optimize the light-driven C-H activation process and scale it up for industrial applications.
But this laser and 2D material-driven breakdown of carbon and hydrogen bonds “in complex organic molecules will open up new possibilities for applications in chemical synthesis, photonics, the degradation of organic pollutants, and plastic recycling,” they write in the paper.
Source: Jingang Li et al. Light-driven C–H activation mediated by 2D transition metal dichalcogenides. Nat. Commun. 2024.
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