Photonic Crystals and Spectroscopic Methods for Studying Complex Systems

Interview conducted by April Cashin-Garbutt, MA (Editor)Apr 19 2016

Please can you give an introduction to your research and what you presented at Pittcon 2016?

My research areas involve optical materials and the development of photonic crystals and spectroscopic methods, especially laser methods, to study complex systems. The areas I work in involve developing chemical sensors and developing UV resonance Raman spectroscopy, for areas such as protein folding, explosives detection, and material understanding of the internal properties.

I gave two talks at Pittcon 2016: one talk on the photonic crystal materials, and then second talk on development methods for detecting trace explosives.

Detection of Trace Explosives with Laser Excitation from AZoNetwork on Vimeo.

How and why are you developing deep UV resonance Raman standoff spectrometers to detect trace explosives?

The idea is that there is a worldwide effort to prevent terrorists from killing people. What you would like to be able to do is to detect the presence of explosives before they explode, and to know where the threats are.

You need a way to determine very small amounts of explosive contamination. For example, a vehicle carrying explosives, the whole idea is to detect the trace quantities that are likely to be left over by terrorists who are handling large amounts of explosives.

The approach we are using is to utilize excitation with the laser in the deep ultraviolet. This is a frontier area of spectroscopy, because it's been hard to access deep ultraviolet light, we have developed new laser sources for this. These laser sources then excite a Raman spectrum of these materials.

We use a telescope to collect and analyze the light, and then to look at the spectrum that we measure and to look for evidence of trace explosives. When we find that, we need to be alert and avoid any explosions.

What are the potential applications?

The initial application is for the Department of Homeland Security in the U.S. to monitor terrorist events. Similar technologies will be developed for bad molecules, drugs, and a variety of hazardous species. First responders may be able to use the technology we have developed.

This is a methodology that we have developed, utilizing the basic research that we have carried out over the last 20 years. We have pioneered this theory of research. We originally pioneered it to look at biological structure and function.

We have a parallel effort, which utilizes this approach to study protein folding. This is probably the most important area of research, to understand how a synthesized protein folds into its native state and allows people to function, and how an error in protein folding leads to human disease. This is an area we continue to work on.

What methodologies are you using?

In the case of the UV Raman work, we use UV resonance Raman spectroscopy. For our photonic crystal work, we develop optical materials that scatter and diffract the light. The way the lengths of light diffracted tell you about the materials and what they are sensing.

How accurately can explosives be identified from their spectroscopic signatures and photochemistries?

They can be definitively identified from the spectroscopic peaks and from the spectra. Each explosive has its own fingerprint. If you see a pattern of bands, which corresponds to the pattern of bands we already know for that explosive, then we'd have that well-identified, but the contribution to the spectrum depends on how much. The less, the smaller the contribution. There is always a detection limit.

What challenges do detecting explosives at standoff distances greater than 2m pose and how can they be overcome?

The further away you are, the less you get to see. You can compensate for that using a telescope, which are larger and larger. The bigger it is, the harder it is to move and the harder it is to utilize. This is a standard challenge of seeing something at a distance.

Is current technology limiting your research in any way? What do you think the future holds for this field?

Of course it does. In order to make progress, you have to define what the available technology is. We develop new laser sources; we build new spectrometers; we create a new state-of-the-art, and we push the state-of-the-art.

It's going to be more and more important, as we are more and more successful. Hopefully, the need will decrease, as we defeat terrorism.

Which talks at Pittcon have you found particularly interesting and relevant to your research?

All of the talks at Pittcon have some relevance. Unfortunately, as people get busier and busier, they have to focus deeper and more tightly. Unfortunately, I go only as far at Pittcon to talks in the general area I'm working in. It was a big disadvantage not to be able to go to the general talks. You have to pick and choose.

What are the key benefits you believe people gain from attending Pittcon? What does Pittcon mean to you?

The benefits of Pittcon is that it's a very large program, a lot of diversity in science. The exhibit is fantastic. If you want to know what the state-of-the-art is in commercialized instrumentation, you just have to walk out there and see what they've got.

Pittcon for me, is special. I live in Pittsburgh. I have contact with the people who organize it. I'm a little bit involved in the organization. I have lots of inside information. It really is a wonderful meeting with the people involved, who really attempt to do the best job possible for the people who come to Pittcon. I get to see that.

About Pittcon

Pittcon^® is a registered trademark of The Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy, a Pennsylvania non-profit organization. Co-sponsored by the Spectroscopy Society of Pittsburgh and the Society for Analytical Chemists of Pittsburgh, Pittcon is the premier annual conference and exposition on laboratory science.

Proceeds from Pittcon fund science education and outreach at all levels, kindergarten through adult. Pittcon donates more than a million dollars a year to provide financial and administrative support for various science outreach activities including science equipment grants, research grants, scholarships and internships for students, awards to teachers and professors, and grants to public science centers, libraries and museums.

What Pittcon Can do for You from AZoNetwork on Vimeo.

About Prof. Sanford Asher

Prof. Sanford A. Asher, BA 1971 is Professor of Chemistry at the University of Pittsburg and Adjunct Professor of Chemistry at Carnegie Mellon University, and has been very successful in his almost 25-year career there.

Prof. Asher received the Chancellor’s Distinguished Research Award at the University of Pittsburgh in 1996, the Bomen Michelson Award of the Coblenz Society in 1998 and the American Chemical Society Pittsburgh Award in 2003.

He was the UM-St. Louis Department of Chemistry's inaugural Distinguished Alumni Lecturer in 1988.

Prof. Asher received a Ph.D. in chemistry at the University of California, Berkeley, in 1977 and served as research fellow in applied physics at Harvard between 1977 and 1980, prior to joining the University of Pittsburg.