Visualizing Chemistry

This guest editorial is by Nancy B. Jackson, manager of the International Chemical Threat Reduction Department at Sandia National Laboratories, Albuquerque, N.M., and chair of the National Academies' committee that authored a recent study on chemical imaging.

I went with my family to the planetarium at Griffith Observatory in Los Angeles a few weeks ago. At the end of the show, as the planetarium sky was slowly brightening, the narrator gave several examples of why astronomy research is important to society and how the study of the stars helps people here on Earth.

I had to chuckle. That appeal for support of fundamental science sounded awfully familiar, but I had not heard it from astronomers before. When I was on the National Academies' Board on Chemical Science & Technology, we used to talk about how much we envied the astronomers, with their dramatic pictures hanging throughout the National Academies building and the Smithsonian National Air & Space Museum and shining from the pages of National Geographic magazines. If there was ever a field that captured the imagination of nonscientists, astronomy was it. If we had great pictures of chemistry, we thought, it would be easy to capture the public's imagination.

In this issue of C&EN—within the technical program between pages 14-TECH and TECH-15—is a poster derived from the National Academies study "Visualizing Chemistry: The Progress and Promise of Advanced Chemical Imaging," which I chaired. The poster contains just a few of the images that our committee believes are as awe-inspiring and eye-catching as those of our astronomer colleagues. We hope to capture the imagination of those who view this poster with the wonder of chemistry as well as the enormous promise it has to improve our future.

Part of the goal of the National Academies study on imaging was to fire up the nonscientist's imagination regarding chemistry. Of course, there were other reasons for the study as well. For example, human visual perception is quite remarkable. Have you ever encountered a dog with two different-colored eyes? It is immediately noticeable. Yet when eyes are the same color it is unremarkable and rarely noticed. What is the basis for this difference in perception?

The ability of humans to spot motion is well-recognized as an adaptation that allowed us to survive by hunting and avoiding predators. Human visual pattern recognition is also quite impressive. How do we so easily tell one face from another? While humans recognize one another with ease, development of facial recognition software for computers has been slow and difficult. Chemical imaging adds humans' powerful visual capabilities as yet another tool for aiding the process of scientific understanding.

Another motivation for the study was the timing. Chemical imaging is poised for great breakthroughs, and great breakthroughs in chemistry are waiting on developments in chemical imaging. Using X-rays to image the internal structures of a single cell, for example, is a task too delicate for the X-rays that Wilhelm Roentgen discovered. In fact, the X-rays used to carry out this feat are a "softer" variety than those used in medical radiography. Biological 3-D tomography of single cells is accomplished by using a specific band of X-ray wavelengths corralled from synchrotron radiation that fall in the "water window" (280–540 eV), where atoms such as carbon and nitrogen absorb strongly and water molecules are mostly transparent.

I first learned about atoms and molecules as a theoretical construct that had never been "seen" directly. Now, however, seeing individual atoms on a metal or metal oxide surface through atomic force microscopy (AFM) or scanning transmission electron microscopy (STEM) is routine. Although it is always awe-inspiring to see a neat row of atoms on an AFM or STEM image, what I'm waiting for is that same sort of clarity on a messy metal oxide catalyst surface under high pressure. I want to view reactions on surfaces under the industrial conditions in which we use them. My career in heterogeneous catalysis has always relied on inference—indirect evidence of the reactions taking place on the surface of a catalyst at high temperatures and pressures. One day, I hope to "see" those reactions.

I hope you enjoy the poster.

Nancy B. Jackson
Sandia National Laboratories