Chemistry Associate Professor Finds Fundamental Behavioral Difference in Methanol Thin Films

Ding-Shyue (Jerry) Yang and Postdoctoral Researcher Xing He Publish Findings in Nano Letters

In a new publication in the American Chemical Society’s Nano Letters, University of Houston associate professor of chemistry Ding-Shyue (Jerry) Yang and postdoctoral researcher Xing He find a fundamental behavioral difference in the energy transport of solid-supported methanol thin films. Their findings could have implications in the behavior of both inorganic 2D materials and organic materials, such as solar panels and human cells.

Ding-Shyue (Jerry) Yang
Associate professor of chemistry Jerry Yang’s research is interdisciplinary, involving materials and surface sciences.

Yang and He explain that understanding energy transport in different nanostructures is crucial to both a foundational understanding of, and practical applications for, heat management.

“We did not anticipate what we found,” Yang said. “In this study, we had a smooth, solid surface, a supporting solid surface, and we had methanol thin film samples grown on top. We wanted to understand how energy moves across this interface.”

A Faster Energy Transport

Yang and He were curious to see the difference in the energy transport of methanol’s two structures. They used ultrafast electron diffraction to reach their conclusion, which Yang and his research group use frequently to study 2D materials. Yang’s laboratory is one of the few labs in the world that can conduct such experiments.

“Our experimental method prepares the methanol samples in two major structures,” said Yang. “One is a 3D crystal structure. This means each sheet in the methanol thin film is a hydrogen-bonded layer, and neighboring sheets are also aligned,” essentially docking into each other and connecting well.

“We can also prepare the methanol sample in a 2D layered structure,” he adds. However, this structure does not allow the sheets of methanol to dock or fit together well. Instead, “they just kind of pile together.”

Yang and He found thermal diffusion is the energy transport mechanism across methanol’s 2D layered structure; whereas much faster, and more efficient ballistic energy transport is observed in the 3D crystal structure.

“Their structural difference seems subtle, but their dynamical responses to energy transport show a drastic difference,” said Yang.

Similarities to Tungsten Diselenide

In their publication, Yang and He write that the contrast observed in methanol’s thin film structure may be similar to the large thermal conductivity difference seen in tungsten diselenide, which may provide further understanding about structural impacts on energy conduction in organic optoelectronic materials.

More broadly, the two explain it is also important to examine energy transport dynamics and structure-property relations in a variety of molecular systems.

“Working on this project was exciting because we found thermal conductivity changes drastically with just a slight change in the structural order of methanol molecular assemblies,” said He, who has been working with Yang for almost eight years. “This is a very important finding for various applications such as heat management in nanoscale electronics.”

Applying Yang’s Experimental System Elsewhere

Seeing the impact that the structure of molecular thin film has on its properties, Yang said, leads his group to consider other molecular thin films, such as our cells.

“Our cell membrane is a molecular assembly. We need something that can transport across the cell membrane. A different structure could lead to different efficiency.”

Because Yang and He have a system that allows them to draw a connection between a structure and a property, Yang said they will think about other systems that have this kind of molecular thin film with factors they could modify.

Yang thanks the National Science Foundation and the Welch Foundation for their continued funding of his research.

- Rebeca Trejo, College of Natural Sciences and Mathematics