Infrared Chiral Plasmons for Vibrational Circular Dichroism Spectroscopy

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With support from the Chemical Measurement and Imaging Program in the Division of Chemistry, Professor Jennifer Shumaker-Parry and her group at the University of Utah are working to improve capabilities for measuring the "handedness" (chirality) of molecules. Chirality arises when a molecule and its mirror image are not superimposable. Chirality is critically important in nature and medicine - for example, it is common for one molecular form of a drug to be effective while its mirror image is ineffective or even toxic. The Shumaker-Parry group is striving to enhance the utility of a chirality-sensitive method known as Vibrational Circular Dichroism (VCD) by utilizing the ability of certain metal nanostructures to selectively enhance the absorption of polarized infrared light by chiral molecules. The research incorporates elements of materials science, physics, surface chemistry, and engineering, thereby providing excellent interdisciplinary training opportunities for graduate and undergraduate students who work together on nanofabrication, materials characterization, optical studies, simulations, and calculations. Professor Shumaker-Parry and her students organize and participate in science education and outreach programs on campus and in the community to encourage students to participate in science. These hands-on nanoscience activities provide excellent opportunities for graduate and undergraduate students to mentor participants and learn to communicate their research to a broad audience.Professor Shumaker-Parry and her group are studying plasmonic nanostructures with tunable infrared (IR) plasmons and orientation-dependent chiroptical activity for plasmon-enhanced VCD spectroscopy. VCD combines IR spectroscopy and circular dichroism (CD) to provide information about chemical groups and local environment enabling chiral-based structural analysis of small molecules, biological molecules, and higher order assemblies. Nanostructures with both tunable IR plasmons and chiroptical behavior form the foundation of systematic studies of the impact of local electric and magnetic fields in VCD spectroscopy of chiral molecules. By manipulating chiroptical behavior of plasmonic nanostructures using control of structure and orientation, symmetric and asymmetric localized electric and magnetic fields are produced. The influence of these sculpted localized fields on chiral molecules will be probed through the IR and VCD spectra as the chiroptical behavior is turned on and off, as well as more finely manipulated. The studies aim to provide an understanding of how nanostructures with IR plasmonic and chiroptical activity impact molecular vibrational spectra of chiral molecules in VCD spectroscopy. The findings from these investigations will establish a foundation for plasmon-enhanced VCD for analysis of chiral molecules. Enhanced detection of chiral molecules would lower detection limits for trace impurities and could lead to highly sensitive real-time monitoring of products in asymmetric catalysis.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.