Understanding Nitrogen-containing Polycyclic Aromatic Hydrocarbons (PAHs)

The American Chemical Society (ACS) Fall 2026 Meeting is taking place later this month at the McCormick Place Convention Center in Chicago, Illinois. Leading up to the conference, we sat down with Pavithraa “Pavi” Sundararajan, a postdoctoral fellow at NASA Ames Research Center, to discuss her latest research.^1,2 Sundararajan will present a talk titled, “Infrared Spectroscopy of Carbon Grains Formed from Nitrogen substituted Polycyclic Aromatic Hydrocarbons Precursors Under Astrophysical Conditions: Implications for Space Return Samples,” at the ACS Fall 2026 Meeting.^1,2

What does the interview segment cover?

In the interview, Sundararajan discusses the laboratory efforts currently underway to recreate and characterize interstellar carbonaceous dust under astrophysically relevant conditions. In her laboratory, small aromatic molecules are subjected to plasma discharge in vacuum and at low temperatures to synthesize carbonaceous dust grains. The resulting grains are preserved in an inert environment before undergoing detailed characterization using several complementary analytical techniques.

Sundararajan discusses several spectroscopic techniques in the interview that her team has used in their research. The first technique is infrared (IR) microspectroscopy, which probes molecular vibrations and produces characteristic spectral fingerprints. Because many ground- and space-based telescopes operate in the IR region, laboratory IR spectra can be directly compared with astronomical observations, helping researchers connect laboratory-produced materials with observations of extraterrestrial environments.

Second, she discusses how Raman microspectroscopy provides another important, complementary method. Although Raman spectroscopy of astronomical materials remains relatively underdeveloped, the technique has significant potential for identifying minerals in meteorites and extraterrestrial samples while revealing complex microstructures and mineral distributions. Raman spectra can also provide information about crystal orientation, stoichiometry, trace foreign ions, stress, and strain. Combined with IR spectroscopy, Raman analysis offers a powerful, nondestructive approach for chemically and physically characterizing extraterrestrial materials.

The third technique Sundararajan mentions in the clip is scanning electron microscopy (SEM), which has been used by her team to visualize the nanoscale dust grains produced in the laboratory. Doing so has allowed the researchers to examine grain morphology and size distributions.

Ultimately, the goal, Sundararajan says, is to create a comprehensive data set that can be shared through three major resources: the Optical Constant Database, the Nanograin Database, and NASA's Raman Spectral Database. Together, these resources will help researchers investigate connections among polycyclic aromatic hydrocarbons (PAHs), interstellar dust, organic materials, meteorites, and samples returned from space missions.

To view our coverage of the upcoming ACS Fall 2026 Meeting, you can access our previews of upcoming talks here: https://www.spectroscopyonline.com/conferences/acs-fall-meeting

References

1. Sundararajan, P. Infrared Spectroscopy of Carbon Grains Formed from Nitrogen substituted Polycyclic Aromatic Hydrocarbons Precursors Under Astrophysical Conditions: Implications for Space Return Samples. Presented at the American Chemical Society, Chicago, Illinois, August 26, 2026. Available at: https://acs.digitellinc.com/live/37/session/596644
2. Wetzel, W. Why Spectroscopists Should Attend the ACS Fall 2026 Conference. Spectroscopy Online, 2026. https://www.spectroscopyonline.com/view/why-spectroscopists-should-attend-the-acs-fall-2026-conference (accessed August 11, 2026).