The Macromolecular, Supramolecular, and Nanochemistry (MSN) Program at NSF is supporting Professors Balaz, Dahnovsky, Kubelka, Varga and their respective groups to study the optical properties of semi-conductor quantum dots (QDs). These are nanometer size crystals made of semiconductor materials. Their spectroscopic properties, such as light absorption and light emission, are closely connected to their size, shape and environment. Amino acids are building blocks of proteins and can exist in two mirror-image structural forms: right-handed and left-handed. Yet, all essential amino acids are left-handed. Placing a left-handed amino acid on the surface of QDs causes the crystal to distinguish between "left-handed light" and "right-handed light". The project aims to understand this interesting phenomenon on a molecular level. The unique properties of mirror-image QDs promise a broad range of new applications in research and technology including memory devices and new light-emitting materials and sensors. The research provides graduate and undergraduate students at the University of Wyoming (UW) with new, exciting research and educational opportunities in a cutting-edge interdisciplinary scientific area. The outcomes of this research are shared in peer-reviewed publications, at regional, national and international meetings, as well as at Wyoming Community Colleges and High Schools. New experiments focusing on QDs are introduced into UW undergraduate curriculum.
Quantum dots (QDs) are semiconductor nanocrystals with potentially unique properties, which arise from the sensitivity of their electronic properties to the QD size and environment. Previous research in Balaz lab has shown that L- and D-enantiomers of the amino acid cysteine induce mirror image circular dichroism and circularly polarized luminescence in achiral QDs. Coupled with quantum size effect, the post-synthetic ligand exchange represents an appealing approach to induce and tune chiroptical characteristics of QDs. The objective of this project is to determine the origin of chiral capping ligand-induced chiroptical activity of achiral QDs using a combination of experimental and theoretical approaches. The project explores: (i) the structural and electronic requirements of QDs as well as chiral capping ligands to induce and tune chiroptical activity of QDs, (ii) the binding geometry of chiral ligands to the surface of QDs, and (iii) fundamental understanding of the origins of the induced chirality through theoretical simulations of ligand induced CD spectra in QDs and their comparison with the experimental CD data. Knowledge acquired within the proposed research is being applied for the development of chiral memory devices, light-emitting nanomaterials, and QD-based devices for chiroptical sensing of chiral biomolecules.
