Study Reveals First Glimpse of a Light-Driven Chemical Reaction

A new study revealing how light-driven reactions unfold at a microscopic level could represent a step forward in producing fuels with renewable processing methods.

In a publication Wednesday in the journal Matter, University of Maryland chemical and biomolecular engineering Associate Professor Taylor Woehl and collaborators developed an advanced electron microscopy technique to image how “plasmonic photocatalysis” reactions occur at the nanometer scale. During such reactions, the interactions between particles of light (known as photons) and microscopic metals (known as plasmonic nanoparticles) are converted into chemical reactants known as “hot carriers.” Previously, it remained unclear how nanoparticle properties like size, shape and material influenced how photons were converted into hot carriers.

Photocatalysis, which drives chemical reactions with light, offers an environmentally friendly alternative to burning fossil fuels and alleviates other risks associated with their extraction and transportation. At least 24% of global greenhouse gas emissions are attributed to burning fossil fuels, according to the latest data gathered by the U.S. Environmental Protection Agency.

Woehl’s group demonstrated how gold nanorods convert light into hot carriers. To do this, they used a technique known as “liquid phase transmission electron microscopy,” which illuminates gold nanorods in liquid with electrons that act as a surrogate to light, and also images the nanorods in real time. They utilized a probe reaction to directly visualize the generation of hot carriers on the nanoparticle surface, and in doing so, they became the first to observe how plasmonic photocatalysis unravels at the nanoscale.

“We were able to watch the reaction in real time, which enabled measuring how efficiently hot carriers were generated at different positions on the nanoparticle surface, which nobody had done before,” said Woehl. “Our experiments will enable establishing design rules for how to engineer more efficient photocatalysts.”