OP: Plasmonic Enhancement of Chiral Forces for Enantiomer Separation

Trustees Of Boston University, Boston

Investigators

Abstract

In this project funded by the Macromolecular, Supramolecular, Nanochemistry program of the Chemistry Division, Professor Bjoern Reinhard of Boston University is developing a new approach to use light to sort chemical molecules based on their "handedness." Similar to the left and right human hand, chemical molecules can exist in different forms that cannot be superimposed. The term for this categorization is called "chirality." Because molecules with different chirality can show very different chemical and pharmacological behaviors it is often important to separate them. To achieve this goal, nanoscale antennas are being developed that, upon radiation with light, generate forces that point in different directions for molecules with different handedness. An outreach program developed by Professor Reinhard offers undergraduate students and inner city high school students opportunities to participate in this research program and to learn more about how light interacts with molecules. The broader impacts of this work include the development of universal chemical separation techniques that are applicable to a broad range of molecules and that can make pharmaceutical compounds safer and cheaper. Professor Reinhard is developing plasmonic antennas that provide strong enough gradients in optical chirality density to enable enantiomer-selective optical forces. The project addresses the design criteria of nanoantennas that generate enantio-selective forces in evanescent enhanced chiral fields of uniform sign. These structures are implemented and characterized, and their ability to separate enantiomers is tested experimentally. Throughout the project both simulations and experiments are applied to optimize plasmonic antennas and maximize chiral forces. This approach will lead to a quantitative understanding of how chiral light-matter interactions are enhanced by resonant plasmonic nanostructures.