Using light to revolutionise chemical reactions and advanced manufacturing.

With the flick of a switch, researchers use light to revolutionise how chemical reactions are controlled, with long reaching implications for advanced manufacturing including computer chip design and pharmaceutical production.

The research team from Queensland University of Technology (QUT), Karlsruhe Institute of Technology (KIT) and Ghent University published their findings in Nature Communications.

Light is used like a remote controlled on/off switch to reversibly change chemical reactions and produce two different products from the same chemical set-up.

Light (on) blocks a chemical reaction resulting in one product (product A). No light (off) produces a different chemical reaction which results in a different product (product B).

Read the research paper, Controlling Thermal Reactivity with Different Colors of Light, by Hannes A. Houck, Filip E. Du Prez & Christopher Barner-Kowollik.

Researchers from QUT, Karlsruhe Institute of Technology and Ghent University have pioneered a system that modulates visible, coloured light to change the reactions of TADs, powerful chemical coupling agenta. Their findings have been published in Nature Communications. Credit: QUT
  • Researchers used green laser light to control the reactivity of triazolinediones (TADs), coupling agents which swiftly create bonds with other chemicals, necessary to make 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
  • The experiment showed two different products can be created from the same set-up simply by switching coloured light on and off
TADs exposed to green laser light. Credit: QUT.
TADs exposed to green laser light. Credit: QUT

Light induced chemical switches are well-known in nature, according to Professor Christopher Barner-Kowollik from the QUT Science and Engineering Faculty.

“Trees use similar processes, yet synthetic analogues haven’t been replicated as effectively in science until now.

“During the day trees use light catching molecules such as chlorophyll to bind carbon dioxide through leaves, depleting it from the atmosphere.

“This complex chemical reaction ceases at night, and trees release carbon dioxide.

Lead author of the paper Hannes Houck (pictured) is conducting PhD studies across the three partner institutions, supported by the Research Foundation-Flanders (FWO). Credit: QUT

“We’ve been inspired by such natural processes and designed a completely light switchable chemical reaction system for the first time,” says Professor Filip Du Prez from Ghent University.

“Our technology can find applications, for example, in breaking the diffraction barrier in 3D laser lithography, enabling the printing of ultra-small objects.”

The team will now explore the 3D laser lithography application with world-leading physicist Professor Martin Wegener from KIT, says lead author, Hannes Houck, who performed many of the research experiments.

“By using such advanced sub-diffraction techniques, visible light could achieve what today needs x-ray to print such as computer chips.”

Professor Barner-Kowollik says Australia also had good conditions to harness natural light for production of highly selective, value-added specialty chemicals.

“In Australia, we could harness natural daylight and night to operate such photoswitchable chemical reactions.

“Daylight would produce one substance, and its absence during the night, another,” Professor Barner-Kowollik said.

The published findings are among the first research outcomes of the Australian Research Council (ARC) Australian Laureate Fellowship awarded to Professor Barner-Kowollik this year.

Hannes Houck, left, and Professor Christopher Barner-Kowollik. Credit: QUT

Abstract

Controlling thermal reactivity with different colors of light was published by Nature Communications on 30 November 2017, accessed via www.nature.com/articles/s41467-017-02022-0

The ability to switch between thermally and photochemically activated reaction channels with an external stimulus constitutes a key frontier within the realm of chemical reaction control. Here, we demonstrate that the reactivity of triazolinediones, powerful coupling agents in biomedical and polymer research, can be effectively modulated by an external photonic field. Specifically, we show that their visible light-induced photopolymerization leads to a quantitative photodeactivation, thereby providing a well-defined off-switch of their thermal reactivity. Based on this photodeactivation, we pioneer a reaction manifold using light as a gate to switch between a UV-induced Diels–Alder reaction with photocaged dienes and a thermal addition reaction with alkenes. Critically, the modulation of the reactivity by light is reversible and the individually addressable reaction pathways can be repeatedly accessed. Our approach thus enables a step change in photochemically controlled reactivity, not only in small molecule ligations, yet importantly in controlled surface and photoresist design. The ability to switch between thermally and photochemically activated reaction channels with an external stimulus constitutes a key frontier within the realm of chemical reaction control. Here, we demonstrate that the reactivity of triazolinediones, powerful coupling agents in biomedical and polymer research, can be effectively modulated by an external photonic field. Specifically, we show that their visible light-induced photopolymerization leads to a quantitative photodeactivation, thereby providing a well-defined off-switch of their thermal reactivity. Based on this photodeactivation, we pioneer a reaction manifold using light as a gate to switch between a UV-induced Diels–Alder reaction with photocaged dienes and a thermal addition reaction with alkenes. Critically, the modulation of the reactivity by light is reversible and the individually addressable reaction pathways can be repeatedly accessed. Our approach thus enables a step change in photochemically controlled reactivity, not only in small molecule ligations, yet importantly in controlled surface and photoresist design.