Viking Technology Could Aid in Nanoparticle Research

The National Science Foundation awarded Vignesh Sundaresan, assistant professor of chemistry and biochemistry, more than $382,000 to further his study of how and why nanoparticles change shape during electrochemical reactions.  

“We need to understand the fundamentals of this process,” he said. "We need to ask the question, “How does the dynamic change in the shape of nanostructures affect the electrochemical property of them? That’s the idea of this proposal.” 

To see the shapes of individual nanoparticles, researchers generally use an electron microscope, which can cost more than half a million dollars. Instead, Sundaresan is using a trick right out of the Viking Age to learn the same information at a fraction of the price.  

Calcite – also called Viking sunstone – is a natural crystalline mineral. It polarizes light and splits one ray of light into two, causing the observer to see two versions of the same object when looking through a calcite crystal.  

More than 1,000 years ago, Vikings used calcite to keep their vessels from getting lost when they traveled on cloudy days. Because calcite polarizes light, Vikings could locate the sun to within 2 degrees of accuracy by drawing a small dot on the back of a calcite crystal and then moving until the two refracted images have the same saturation.  

Using a sliver of calcite attached to a rotating platform, Sundaresan uses the mineral’s unique polarizing properties to determine the shape of single nanoparticles. The rotating lens and calcite can be used with virtually any microscope, he said.  

“People have tried to develop different optical methods to see whether we could be able to get structural information without relying on these high-end methods like electron microscopy, because one, it's expensive, and two, it's actually very slow,” Sundaresan said. “Our technique can do that at a cheaper price and in a high-throughput fashion.”  

Sundaresan named this new method “calcite-assisted localization and kinetics microscopy,” or CLocK. The technique allows researchers to observe and track the structural transformations of nanoparticles in real time at the single-particle level. 

“One of the many uses is using these nanoparticles as a catalyst to drive some of the chemical reactions more efficiently,” Sundaresan said. “That includes hydrogen reactions and carbon dioxide reduction reactions, which are all a part of creating renewable energy.” 

Differently shaped nano-structures – such as nano-cubes, nano-stars or nano-rods – perform differently as catalysts, but a nano-structure changes shape as it goes through an electrochemical reaction, slowing the catalyzation process.  

Understanding why nanoparticles change shape will help researchers improve and hasten the process of creating renewable energy, Sundaresan said.  

“Now can we ask a question, ‘How does the dynamic change in the shape of (nanoparticles) affect their electrochemical property?’” he said. “That's the overall idea of this proposal, is to get the structural information while it is catalyzing a reaction using the technique that we actually developed.” 

This report is based on work supported by the National Science Foundation grant No. 2404070. 

Top image: Vignesh Sundaresan, assistant professor of chemistry and biochemistry, recently received a $382,000 grant from the National Science Foundation to further his study of nanoparticles. Photo by Kevin Bain/Ole Miss Digital Imaging Services.