Career Fair and Career Events

Nicholas Kotov

University of Michigan

Faculty host: Chen Yang

Student host: Nan Zheng

MSE Talks Website: www.bu.edu/eng/msetalks

Title: Chirality and Complexity of Engineered Nanostructures

Abstract:

The structural and functional complexity of biomimetic materials arises from the spontaneous hierarchical ordering of inorganic building blocks over multiple scales. Empirical observations of complex nanoassemblies are abundant, but physicochemical mechanisms leading to their geometrical complexity remain puzzling, especially for non-uniformly sized components. These mechanisms are discussed in this talk taking an example of hierarchically organized particles with twisted spikes and other morphologies from polydisperse Au-Cys nanoplatelets [1]. The complexity of these supraparticles is higher than biological counterparts or other complex particles as enumerated by graph theory (GT). Complexity Index (CI) and other GT parameters are applied to a variety of different nanoscale materials to assess their structural organization. As the result of this analysis, we determined that intricate organization Au-Cys supraparticles emerges from competing chirality-dependent assembly restrictions that render assembly pathways primarily dependent on nanoparticle symmetry rather than size. These findings open a pathway to a large family of colloids with complex architectures and unusual chiroptical and chemical properties. The design principles elaborated for nanoplatelets have been extended to engineering of other complex nanoassemblies. They include polarization-based drug discovery platforms for Alzheimer syndrome,[3] materials for chiral photonics,[5] biomimetic composites for energy and robotics [2,4], CO2-dispersable catalysis [6] and chiral antiviral vaccines.[7] Yet, the work on the generalization of the engineering principles for chiral biomimetic nanostructures is incomplete; further directions of these efforts will be discussed. References [1] W. Jiang, Z.-B. et al, Emergence of Complexity in Hierarchically Organized Chiral Particles, Science, 2020, 368, 6491, 642-648. [2] Wang, M.; Vecchio, D.; et al Biomorphic Structural Batteries for Robotics. Sci. Robot. 2020, 5 (45), eaba1912. [3] Jun Lu, et al, Enhanced optical asymmetry in supramolecular chiroplasmonic assemblies with long-range order, Science, 2021, 371, 6536, 1368. [4] D. Vecchio et al, Structural Analysis of Nanoscale Network Materials Using Graph Theory, ACS Nano 2021, 15, 8, 12847–12859. [5] L. Ohnoutek, et al, Third Harmonic Mie Scattering From Semiconductor Nanohelices, Nature Photonics, 2022, under embargo [6] L. Tang et al. Self-Assembly Mechanism of Complex Corrugated Particles" JACS, 2021 on the web. [7] L. Xu, et al Enantiomer-Dependent Immunological Response to Chiral Nanoparticles, Nature, 2022, under embargo.

Speaker Bio:

Prof. Kotov received his PhD from Moscow State University in 1990 on Reaction Kinetics, followed by a postdoc at Syracuse University. After starting his independent career at Oklahoma State University in 1996, he joined the University of Michigan in 2003. The research in the Kotov group revolves around biomimetic nanostructures and the self-organization of small building blocks into large structures with applications from energy materials to implantable biomedical devices. Prof. Kotov has received many rewards in his career, including an NSF CAREER award and the MRS Medal, and is an MRS and RSC fellow.