Rice University researchers (from left) Yiming Huang, Eilaf Egap and Yifan Zhu are employing the power of the sun to build functional synthetic polymers using photosensitive, semiconducting quantum dots as a catalyst. Image: Jeff Fitlow/Rice University.Scientists at Rice University plan to employ the power of the sun to build functional synthetic polymers using photosensitive quantum dots – microscopic semiconducting particles – as a catalyst.
The luminescent quantum dots are only a few nanometers wide but have highly tunable optical and electronic properties. They are beginning to show up in modern displays, but lend themselves to industrial chemistry as well.
The Rice lab of materials scientist Eilaf Egap is focusing on industrial applications with its demonstration of a stable and economical method to make polymers through photo-controlled atom-transfer radical polymerization. This method could replace the molecular catalysts or expensive transition metals currently used to make polymer materials like methacrylates (common in plastics), styrene and block copolymers.
The work by Egap, Rice postdoctoral researcher and lead author Yiming Huang and graduate student Yifan Zhu is detailed in a paper in ACS Macro Letters.
The lab used various light sources, including the sun and even a household lamp, to illuminate a solution of dispersed cadmium selenide quantum dots. That prompted the generation of free radical atoms from a bromide-based initiator, which in turn triggered acrylate monomers in the solution to link together. Because the monomers tested in Egap's lab had no ability to terminate propagation of the chain, the process is called living polymerization.
"It will keep going until it consumes all the monomers or you decide to terminate," Egap said.
Egap, an assistant professor of materials science and nanoengineering and chemical and biomolecular engineering, said quantum dot polymerization shows promise for highly controlled growth of sophisticated polymers. "The beauty of this is if you have monomer A and you want to add monomers B and C in a specific sequence, you can do that," she said. "In a random polymerization, they would be randomly dispersed along the polymer backbone.
"The implication here – and part of our broader goal – is that we can synthesize organic-inorganic hybrid structures in a controlled and periodic way for many applications."
She anticipates the process could also lead to the discovery of novel polymers. One example might be a quantum dot photocatalyst with an attached semiconducting polymer that would simplify the manufacture of solar cells and other devices.
"These could also be relevant to light-emitting diodes, magnetoelectronics and bioimaging," she said. "We could grow them all at once. That's the dream, and I think we are within reach."
This story is adapted from material from Rice University, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.