(2en) Multi-Scale Design of Hybrid Materials for Chiral Photonics

In nature, we often see seemingly disordered but aesthetically pleasing structures such as butterfly wings, chameleon skin, and spiderwebs. Simple, non-linear rules of self-replicating building units across multiple length scales give rise to complex architectures that make butterfly wings and chameleon skin iridescent while spiderwebs are both strong and flexible. However, replicating nature’s complexity from the nano-macro scale by guided self-assembly of nanoparticles is not a trivial task. Interaction forces between particles transition from electrostatic to van der Waals to dispersion to gravitational pull as size increases making it difficult to engineer structures from nanometer to centimeter scale in a single reaction. Several decades of research have developed symmetric building blocks in the form of quantum dots (QDs) of different shapes and sizes that have been self-assembled into thin films and supraparticles. One of the applications for these nanocrystals and their thin films is found in current QD-OLED displays. However next-generation technologies such as encryption, data transmission, and holography will be based on chiral photonics which requires the design of scalable chiral materials. To this end, my research poses the following questions –

• How do chiral interactions affect the packing of nanoparticles into superstructures?
• What is the relationship between chiral morphology and optical response?
• How do photonic properties of chiral architectures differ from their achiral counterparts?

In this presentation, my focus will be on single-pot synthesis strategies for complex architectures made from hybrid metal-amino acid complexes. I will demonstrate how electrostatics and van der Waals forces compete during self-assembly and how they can be tuned using various physical-chemical parameters to design desired chiral architectures. I will draw an analogy between the bandgap tuning of QDs and the multi-spectral (THz to UV-Vis) tuning of chiroptical response. I will present a vision for my research group which would employ multi-scale colloidal synthesis, characterization, and computational tools to design chiral materials from the bottom-up for next-generation photonic devices.

Teaching interests

I believe framing a question requires an in-depth knowledge of concepts. As a materials chemist, my goal is to impart a fundamental understanding of material properties so that my students can pose the following questions from even a mundane observation like the tearing of a plastic grocery bag - Why does the bag stretch before snapping? How much weight can the bag withstand? Could I design another polymer that is equally convenient but environmentally friendly? Subsequently, they should be able to break the problem into parts and seek out interdisciplinary teams to engineer solutions to their questions.

I have a strong desire to teach and mentor students from diverse backgrounds. At the University of Minnesota, I have taught a material testing laboratory course at the undergraduate level and served as a teaching assistant for both undergraduate and graduate courses. At the University of Michigan, I have completed a semester-long certificate program on teaching and mentoring methodologies with the Center for Research on Learning and Teaching. I have mentored three undergraduate and three graduate students which has resulted in co-authored, and first-author peer-reviewed publications highlighted below. As a teacher, I want to share my atomic-scale perspective of materials chemistry with chemical engineering students through introductory and advanced courses such as Separation Processes, Thermodynamics, Transport Phenomena, and Particle Science and Technology.

Background

I am a Materials Scientist developing materials at the interface of chemical and biomolecular engineering for separation of isomers, single-atom catalysis, and chiroptical sensing of biomolecules. I received training in the Departments of Chemical Engineering and Materials Science at the University of Minnesota, along with a minor degree in the Department of Chemistry. My doctoral research, advised by Prof. K. Andre Mkhoyan and Prof. Michael Tsapatsis, was focused on developing the area of two-dimensional (2D) porous materials using analytical transmission electron microscopy (TEM). This body of work benefits the field of energy-efficient molecular separation, in terms of achieving the highest separation selectivity for xylene isomers by designing the optimized material. I graduated with my Ph.D. in August 2018 and started working with Prof. Nicholas A. Kotov at the Biointerfaces Institute at the University of Michigan, Ann Arbor. My ongoing work can be broken down into three themes: 1) the synthesis of chiral architectures of cadmium-cystine and gold-cysteine complexes, 2) the mechanisms of chirality transfer from the atomic scale to macroscale, 3) the structure-optical property correlation for hierarchically assembled chiral bundles (bowties) and spherulites (hedgehogs).

Selected Publications

Prashant Kumar, Thi Vo, Minjeong Cha, Anastasia Visheratina, Ji Young Kim, Wenqian Xu, Jonathan Schwartz, Alexander Simon^±, Daniel Katz^±, Emanuele Marino, Wonjin Choi, Si Chen, Christopher Murray, Robert Hovden, Sharon Glotzer, Nicholas A. Kotov. Photonically Active Bowtie Nanoassemblies with Chirality Continuum. DOI: 10.21203/rs.3.rs-1614619/v1 (Under Review)

Prashant Kumar, Alexander Simon^±, Emanuele Marino, Daniel Katz^±, Christopher Murray, Nicholas A. Kotov. Optical Vortices in Birefringent Chiral Supraparticles. (Under Preparation)

Prashant Kumar^¶, Dae Woo Kim, Neel Rangnekar, Hao Xu, Evgenii Fetisov et. al. One-dimensional intergrowths in two-dimensional zeolite nanosheets and their effect on ultra-selective transport. Nature Materials, 19, 443–449 (2020).

Wenfeng Jiang, Zhibei Zhu, Prashant Kumar, Drew Vecchio et. al. Emergence of complexity in Hierarchically Organized Chiral Particles. Science, 368, 6491, 642-648 (2020).

Supriya Ghosh^±, Hwanhui Yun, Prashant Kumar, Sabrina Conrad, Michael Tsapatsis, and K. Andre Mkhoyan. Two Distinct Stages of Structural Modification of ZIF-L MOF under Electron-Beam Irradiation. Chemistry of Materials. 33, 14, 5681–5689 (2021).

Xiaoli Ma*, Prashant Kumar*, Nitish Mittal*, P. Douditis, K. Andre Mkhoyan, Michael Tsapatsis. Zeolitic imidazolate framework membranes made by ligand-induced permselectivation. Science, 361, 6406, 1008-1011 (2018).

Mi Young Jeon*, Donghun Kim*, Prashant Kumar*, Pyung Soo Lee*, Neel Rangnekar, Peng Bai et. al. Ultra-selective high-flux membranes from directly synthesized high aspect ratio zeolite nanosheets. Nature, 543, 690-694 (2017).

Prashant Kumar, Kumar Varoon Agrawal, Michael Tsapatsis, K Andre Mkhoyan. Quantification of thickness and wrinkling of exfoliated two-dimensional zeolite nanosheets. Nature Communications, 6, 7128 (2015).

(^¶ Corresponding author, * Co-first Author, ^± Undergraduate/Graduate Mentee)