NSF Award
2425696
Nontechnical Description<br/><br/>The double-helix of DNA is a classic example of the geometric property known as chirality. While a chiral structure may look like its mirror image, it cannot be transformed into its mirror image by any combination of rotation or translation. Molecules with chiral structures have unique optical behaviors. Notably, they absorb left-handed or right-handed circularly polarized light differently, a phenomenon known as circular dichroism with applications such as 3D displays, drug discovery, and quantum optics. The focus of this project is to create a new class of chiral materials based on metal halide perovskites, hybrid semiconductors with both organic and inorganic components. Investigators will integrate chiral and achiral organic cations into two-dimensional hybrid perovskites, thereby engineering novel materials with tunable circular dichroism. Students involved in the project will be trained in interdisciplinary research at the interface of physical chemistry and materials science. Investigators will seek to broaden participation in STEM through outreach to K-12 students and using established mechanisms to recruit students from HBCUs.<br/><br/>Technical Description<br/><br/>This project is based on the recent demonstration of a new approach to achieve chiral two-dimensional hybrid metal halide perovskites (MHPs) via mixing chiral cation and non-chiral (achiral) cations. A chiral cation in can transfer chirality to the inorganic framework and that introducing an achiral cation would not diminish the circular dichroism. This project aims to develop chiral 2D hybrid perovskites with tunable circular dichroism by incorporating large, conjugated achiral organic cations via the mixed cations-based approach. To further expand the chiroptical properties of 2D hybrid perovskites, a new 'chirality transfer' concept would be combined with appropriate energy level alignments via a mixed cation approach. There objectives for this project are: (1) Synthesis and characterization of new chiral 2D hybrid MHPs that combine large, conjugated achiral cations with smaller chiral cations. (2) Investigating chiroptical properties of these newly synthesized hybrid perovskites, potentially leading to novel chiroptic behaviors, such as extending the response range and amplifying the response amplitude. (3) Understanding the mechanism of chirality transfer. The success of this project will offer new strategies to achieve new chiral hybrid perovskites, together with new mechanistic insights. The results will not only contribute to our understanding of chirality transfer, but also potentially open new avenues for applications such as circular polarized light detection and emission.<br/><br/>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.
