Seminar Speaker: Nicholas Kotov, University of Michigan

Chiral Nanostructures

Abstract

The early observation of exceptionally high circular dichroism in chiral nanostructures has led to the rapid development of this field, encompassing particles and assemblies from nanoscale metals, semiconductors, ceramics, and allotropes of carbons. The chiral nanoparticles and nanoassemblies display all chiral geometries in organic stereochemistry, biological chemistry, and structural biology, such as tetrahedrons, helices, twisted rods, and propellers, but at larger scales. It is the larger dimensions and the greater polarizability of inorganic nanomaterials than organic chiral compounds that result in the giant optical activity. Chiral nanostructures’ size, geometry, and composition can be tuned to resonate with a wide range of photon energies from ultraviolet to terahertz. The high intensity and sharpness of circular dichroism peaks of chiral nanostructures facilitated their use in biosensing.

Recent studies have revealed additional unique aspects of chiral nanostructures. Their absolute three-dimensional geometry can be accurately established by electron microscopy. Unlike chiral molecules that exist as binary enantiomers, nanostructures display a chirality continuum. Also, chiral nanoparticles are essential for understanding the complexity of biological matter because nanoscale chirality enforces reproducible self-assembly patterns while enabling adaptability to environmental conditions. And chiral nanoparticles selectively interact with biological counterparts of similar scale. The strength and selectivity of their interactions can be varied by nanoparticle geometry, surface ligands, and chemical
composition.

Future research directions in the field of chiral nanostructures include the utilization of their multiscale chirality for chiral catalysis. The giant optical activity can be harnessed for detecting and emitting circularly polarized light for emerging information technologies, including those under extreme conditions and 6G/7G telecommunications, as well as polarization-based perception systems, and real-time holography. These possibilities can be enabled by the intense circularly polarized black body radiation from chiral nanostructures.

Biography

Nicholas A. Kotov is Irving Langmuir Distinguished University Professor in Chemical Sciences at the University of Michigan. He is a pioneer of theoretical foundations and practical implementations of complex systems from ‘imperfect’ nanoparticles including composites from polydispersed colloids of graphene oxide, clay, cellulose, and other materials. Chiral nanostructures and graph theoretical representations are the focal points in his current work. Nicholas is a recipient of more than 60 awards and recognitions. Nicholas founded six startups that commercialized self-assembled nanostructures for energy, healthcare and automotive industry. Nicholas is a Fellow of America Academy of Arts and Sciences and National Academy of Inventors. He is an advocate of scientists with disabilities.