A new approach to studying the viscosity of water has revealed new discoveries about the behavior of water molecules and may even open new paths for liquid-based electronics.
Researchers, from the Department of Energy’s Oak Ridge National Laboratory, used a high-resolution inelastic X-ray scattering technique to measure the strong bond between a hydrogen atom sandwiched between two oxygen atoms. The hydrogen bond is a quantum-mechanical phenomenon that is responsible for various properties of water, including viscosity, which determines a liquid’s resistance to flow or changing shape.
While water is currently the most abundant substance on Earth, the behavior at a molecular level is not well understood.
"Despite all what we know about water, it is a mysterious, atypical substance that we need to better understand to unlock its vast potential, particularly in information and energy technologies," said Takeshi Egami, University of Tennessee-ORNL Distinguished Scientist/Professor working through the Shull Wollan Center — a Joint Institute for Neutron Sciences, an ORNL-UT partnership.
The study demonstrated that it is possible to probe real-space, real-time dynamics of water and other liquids. Other studies in the past have provided snapshots of water’s atomic structure, but little is known about how water molecules move.
"The hydrogen bond has a strong effect on the dynamic correlation between molecules as they move through space and time, but so far the data, mostly by optical laser spectroscopy, yielded broad or 'hazy' results with unclear specificity," Egami said.
For a clearer picture, the team used an advanced X-ray technique called inelastic X-ray scattering to determine molecular movement. They found that the dynamics of oxygen-to-oxygen bonding between water molecules is not random, but actually highly coordinated. When the bond between water molecules is disrupted, the strong hydrogen bonds work to maintain a stable environment over a specific period of time.
"We found that the amount of time it takes for a molecule to change its 'neighbor' molecule determines the water's viscosity," Egami said.
The discovery would stimulate further studies on exerting control over the viscosity of other liquids. Egami views the current work as a springboard to more advanced research that will leverage neutron scattering techniques at the Spallation Neutron Source at ORNL, a DOE Office of Science User Facility, in order to determine the origin of viscosity and other dynamic properties of liquids.
The research team’s approach could be used to characterize the molecular behavior and viscosity of ionic, or salty, liquids and other liquid substances, which could aid in the development of new types of semiconductor devices with liquid electrolyte insulating layers, better batteries and improved lubricants.
The paper on this research was published in Science Advances.