Joel Yuen-Zhou harnesses photons to control chemical reactions and properties

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Joel Yuen-Zhou harnesses photons to control chemical reactions and properties
Joel Yuen-Zhou harnesses photons to control chemical reactions and properties

Credit: Elisa Ferrari Photography

Joel Yuen-Zhou

Joel Yuen-Zhou spends his time solving scientific puzzles and developing entirely new ways of driving chemical reactions using quantum effects. The University of California San Diego theoretical chemist says he found his career through a series of happy accidents in childhood.

Vitals

Hometown: Mexico City

Education: BSc, chemistry and mathematics, Massachusetts Institute of Technology, 2007; PhD, chemical physics, Harvard University, 2012

Current position: Associate professor, University of California San Diego

Professional advice: Avoid being too busy; otherwise, great ideas won’t come to you.

What reminds me of home: I miss Mexican pan dulce.

Memorable books: On Earth We’re Briefly Gorgeous, by Ocean Vuong; Imperio, by Héctor Zagal

I am: Asian-Latino, gay

As a child, however, Yuen-Zhou assumed he’d end up working in a job that he didn’t enjoy. His parents, who immigrated from China to Mexico, never graduated from high school. Unaware of the breadth of career opportunities available to their son, they encouraged him to pursue one of the few professions they knew about, such as architecture or dentistry, he says. None of these career options interested Yuen-Zhou in the slightest.

Yuen-Zhou’s bleak view of his future changed when he was 14 and competed in a math contest. He liked it so much that he immediately signed himself up for a chemistry competition, the first of many he would partake in.

At the chemistry olympiad, he met mentors who saw his potential and encouraged his love for and curiosity about science. He also decided to make a career out of entertaining himself with fun molecular problems. “I feel very fortunate that that’s something that I am able to do nowadays,” Yuen-Zhou says.

Yuen-Zhou is investigating a new class of chemistry fueled by light. He uses theoretical calculations to model the behavior and interactions of molecules inside an optical cavity, a minuscule area created by mirrors spaced only a few hundred nanometers apart. It traps photons by forcing them to ricochet back and forth. When his team places molecules in the cavity, they absorb the bouncing photons, generating what Yuen-Zhou calls “a continuous exchange of energy between light and matter.” Under the right experimental conditions, quantum effects emerge; light and matter become indistinguishable from each other and create a hybrid state called a polariton.

The molecules that make up polaritons interact with ricocheting photons over and over again. That action creates a dynamic different from what chemists observe in traditional photoexcited molecules. In polaritons, “you create new energy states that differ drastically from what you would get outside the cavity,” Yuen-Zhou says. Over the past few decades, researchers have taken advantage of these states to modify the conductivity, reactivity, and other properties of compounds.

Yuen-Zhou and his group have been expanding the space of possibilities for polariton research, says Raphael F. Ribeiro, a theoretical chemist at Emory University who did a postdoc in Yuen-Zhou’s lab. In 2019, the two scientists published a theoretical study suggesting that optical cavities can mediate reactions between two molecules that never physically touch. For example, when glyoxylic acid and cis-nitrous acid are placed in adjacent optical cavities that share a central mirror, the photons act like a wire, connecting the two systems and, subsequently, promoting the isomerization of nitrous acid (Chem 2019, DOI: 10.1016/j.chempr.2019.02.009).

Since then, Yuen-Zhou says, other collaborators have demonstrated this concept experimentally, showing that two molecules can “start talking to each other” in a reaction that is made possible only by polaritons. He adds that in the future, this new type of reaction vessel could aid synthetic chemists by significantly improving reaction rates or allowing researchers to break bonds that they wouldn’t otherwise be able to.

Science is a space that allows for coexistence of people of diverse backgrounds, interests, and beliefs.

But because of the cutting-edge nature of some of the experiments used to probe polaritons and their potential chemical applications, chemists wonder, “Is this right? Is this real?” says Keith A. Nelson, a chemist at the Massachusetts Institute of Technology and a longtime collaborator of Yuen-Zhou’s. By developing the mathematics and computer algorithms that researchers can use to understand and model their observations, “Joel has really played a pretty leading role in helping get to the core of what is going on.”

Ribeiro says he was initially drawn to Yuen-Zhou’s group because of the interesting research his lab was producing. He believes that Yuen-Zhou is “pushing the frontiers of chemistry.”

Joel Yuen-Zhou stands parallel to a whiteboard and writes.

Credit: Elisa Ferrari Photography

Joel Yuen-Zhou uses theoretical calculations to study new ways to drive chemical reactions.

But Yuen-Zhou contributes much more to the chemistry community than trailblazing research. Ribeiro says Yuen-Zhou is conscious of biases in academia against people from marginalized racial and ethnic groups, LGBTQ+ communities, and other groups and takes action to address them. For example, when Yuen-Zhou organizes conferences, he always scans the list of invited people to make sure it’s a balanced, diverse group. And when Ribeiro was in his lab, Yuen-Zhou would regularly discuss strategies for combating bias in group meetings and personal conversations.

Yuen-Zhou’s passion for inclusivity was driven by his own experiences growing up Asian Latino in Mexico. “There are not many Chinese people in Latin America,” he says. As a result, “I experienced a lot of racism and bullying in school.”

The chemistry olympiads frequently acted as a refuge from this reality. “I witnessed early on that science is a space that allows for coexistence of people of diverse backgrounds, interests, and beliefs,” he says. At UC San Diego, Yuen-Zhou appreciates the opportunity to mentor a wide range of students and trainees, including many Asian and Latin American researchers. He hopes he can inspire them to pursue chemistry, the same way his mentors did for him.

“Those people were so generous with their time and with their efforts, and they really made a huge impact in my life,” he says. To pay it forward, he says, he wants to use his platform to inspire and empower the next generation of scientists.

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