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Light Switches Chemistry for Nanomaterial Production

Could the manufacture of integrated circuits and chips for everyday electronic devices be made simpler, safer and cheaper simply by being able to switch coloured light on and off? Researchers have stepped towards this possibility by pioneering a system that modulates visible coloured light to change the reactions of a powerful chemical coupling agent.

The researchers used green laser light to control the reactivity of triazolinediones (TADs). These coupling agents swiftly create bonds with other chemicals, which is necessary to make new materials. Under green light the TADs stopped reacting; when the light was switched off, the TADs became highly reactive again. The light-switching process could be repeated multiple times, and the experiment showed that two different products could be created from the same set-up simply by switching coloured light on and off.

Prof Christopher Barner-Kowollik of Queensland University of Technology said the ability to use visible light as a remote-controlled on/off chemical reaction switch opened up possibilities for future industry applications in chemical and advanced manufacturing, including computer chip fabrication. “At the moment, ultraviolet (UV) light, which has shorter wavelengths than light in the visible spectrum, is used in industry to drive chemical processes,” he said.

“Industrial processes making use of less harmful visible light are scarce – a sharp contrast to what occurs in nature. For plants, visible light plays a critical role in chemical processes. Trees harvest light during the day and use this as an energy source to grow, releasing oxygen in the process. At night, however, when light is no longer available, the chemical process is altered and plants release carbon dioxide. We’ve been inspired by such natural processes and designed a completely light-switchable chemical reaction system for the first time.”

The research team’s new system can be applied to create light-sensitive materials for 3D laser lithography – a type of 3D printing using direct laser light that allows printing of nanoscale structures, such as scaffolds for cells or computer chips. “Contemporary chip fabrication is a complex and expensive system of chemical processes,” Barner-Kowollik explained. “Here, due to the so-called light diffraction limit, radiation with short wavelengths – which is very harsh UV light – is used.

“But what if we could use visible light to reversibly switch certain chemical processes and get around the light diffraction limit and print very, very small structures, for example 5 nm wide? Being able to switch chemical reactivity within 3D laser lithography could revolutionise chip printing, and make it cheaper, simpler and safer.

“There are substantial barriers to overcome, but potentially the system we have devised with visible light as a chemical deactivation mechanism could provide an avenue to achieve that.”

The research has been published in Nature Communications.