Following the people and events that make up the research community at Duke

Tag: chemistry

Researchers created a tiny circuit through a single water molecule, and here’s what they found

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Graphic by Limin Xiang, Arizona State University

Many university labs may have gone quiet amid coronavirus shutdowns, but faculty continue to analyze data, publish papers and write grants. In this guest post from Duke chemistry professor David Beratan and colleagues, the researchers describe a new study showing how water’s ability to shepherd electrons can change with subtle shifts in a water molecule’s 3-D structure:

Water, the humble combination of hydrogen and oxygen, is essential for life. Despite its central place in nature, relatively little is known about the role that single water molecules play in biology.

Researchers at Duke University, in collaboration with Arizona State University, Pennsylvania State University and University of California-Davis have studied how electrons flow though water molecules, a process crucial for the energy-generating machinery of living systems. The team discovered that the way that water molecules cluster on solid surfaces enables the molecules to be either strong or weak mediators of electron transfer, depending on their orientation. The team’s experiments show that water is able to adopt a higher- or a lower-conducting form, much like the electrical switch on your wall. They were able to shift between the two structures using large electric fields.

In a previous paper published fifteen years ago in the journal Science, Duke chemistry professor David Beratan predicted that water’s mediation properties in living systems would depend on how the water molecules are oriented.

Water assemblies and chains occur throughout biological systems. “If you know the conducting properties of the two forms for a single water molecule, then you can predict the conducting properties of a water chain,” said Limin Xiang, a postdoctoral scholar at University of California, Berkeley, and the first author of the paper.

“Just like the piling up of Lego bricks, you could also pile up a water chain with the two forms of water as the building blocks,” Xiang said.

In addition to discovering the two forms of water, the authors also found that water can change its structure at high voltages. Indeed, when the voltage is large, water switches from a high- to a low-conductive form. In fact, it is may be possible that this switching could gate the flow of electron charge in living systems.

This study marks an important first step in establishing water synthetic structures that could assist in making electrical contact between biomolecules and electrodes. In addition, the research may help reveal nature’s strategies for maintaining appropriate electron transport through water molecules and could shed light on diseases linked to oxidative damage processes.

The researchers dedicate this study to the memory of Prof. Nongjian (NJ) Tao.

CITATION: “Conductance and Configuration of Molecular Gold-Water-Gold Junctions Under Electric Fields,” Limin Xiang, Peng Zhang, Chaoren Liu, Xin He, Haipeng B. Li, Yueqi Li, Zixiao Wang, Joshua Hihath, Seong H. Kim, David N. Beratan and Nongjian Tao. Matter, April 20, 2020. DOI: 10.1016/j.matt.2020.03.023

Guest post by David Beratan and Limin Xiang

New Course Offers Lessons from Lasering Priceless Art

Duke graduate student Tana Villafana and chief conservator at the NC Museum of Art William Brown stand over The Crucifixion (inset). (Photo: Martin Fischer)

Duke graduate student Tana Villafana and chief conservator at the NC Museum of Art William Brown stand over The Crucifixion (inset). (Photo: Martin Fischer)

By Erin Weeks

A group of chemists at Duke University has gained recognition in recent years for shooting lasers at medieval artwork — technology that allows a harmless peek at the many layers and materials in a painting and offers insight into long gone eras and artists. Now, Duke students will have the chance to learn from this pioneering work at the intersection of chemistry and art history in a new course on the science of color.

The course coincides with the publication of the first scientific measurements from the laser work, reported Jan. 20 in the Proceedings of the National Academy of Sciences.

“The images we have now are enormously better than a year ago,” said Warren S. Warren, head of the lab performing the imaging and the James B. Duke professor of chemistry. He and fellow Duke authors, grad student Tana Villafana and associate research professor Martin Fischer, have not only demonstrated the technology works — they’ve shown it works at an incredible level of detail, telling the difference, for example, between nearly identical pigments.

But lasering The Crucifixion by Puccio Cappano was just the start, as the team envisions countless more cultural applications of the technology. Given enough funding and manpower, they could visualize ancient scrolls of text too fragile to unroll, reveal the bright colors that once adorned Greek statues, learn the secrets of China’s terracotta warriors, and even detect the beginnings of pigment degradation in aging artwork.

There are talented people in art conservation, Warren said, whose work could benefit from more advanced technology, and there are talented people at the cutting-edge of laser science looking for meaningful ways to apply their inventions. For the past several years, Warren’s lab has brought these people together.

Now, he hopes to accomplish something similar with students at Duke. Warren, Fischer, and another chemistry instructor, Adele DeCruz, are teaming up to teach “The Molecular, Physical, and Artistic Bases of Color” in the second half of spring semester.

The class will visit the Nasher Museum of Art, the North Carolina Museum of Art in Raleigh, and possibly even the National Gallery of Art in Washington, D.C, to learn first-hand from art conservators and working artists. Students can expect to learn about how humans have used and made pigments over the millennia; how color works at a molecular level; and the basics of how human vision, microscopes, cameras, and lasers all see or image color.

Students can register for the half course, CHM 590, until the add/drop deadline for classes on January 22. “Students should not be scared off by the course number,” Warren said. “The prerequisite is one college-level science course, and the intent is to make both the science and artistic components accessible to a broad audience.”

Funding for the research was provided by National Science Foundation grant CHE-1309017.

CITATION: “Femtosecond pump-probe microscopy generates virtual cross-sections in historic artwork.” Tana E. Villafana, William P. Brown, et al. Proceedings of the National Academy of Sciences, Jan. 20, 2014. Doi: 10.1071/pnas.1317230111

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