Nanomaterials Design
We design nanomaterials with advanced functionality.
- Controlling nanocrystal shape and composition
- Directional entropic and enthalpic forces
- Amorphous photonic band gap materials
Controlling nanocrystal shape and composition
The application of nanocrystals as heterogeneous catalysts and plasmonic nanoparticles requires fine control of their shape and chemical composition. A promising idea to achieve synergistic effects is to combine two distinct chemical and/or physical functionalities in bimetallic core@shell nanocrystals. Although techniques for the synthesis of single-component nanocrystals with spherical or anisotropic shape are well-established, new methods are sought to tailor multicomponent nanocrystals. We probed etching in a controlled redox environment as a synthesis technique for multicomponent nanocrystals. We also proposed a route towards nanocatalysts with high durability by depositing an alloyed phase on top of intermetallic seeds and analyzed the etching of core-shell particles using in-situ liquid cell transmission electron microscopy.
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Lei Chen, Alberto Leonardi, Jun Chen, Muhan Cao, Na Li, Dong Su, Qiao Zhang, Michael Engel, Xingchen Ye
Imaging the Kinetics of Anisotropic Dissolution of Bimetallic Core-Shell Nanocubes using Graphene Liquid Cells
Nature Communications 11, 3041 (2020) -
Jocelyn T. L. Gamler, Alberto Leonardi, Xiahan Sang, Kallum M. Koczkur, Raymond R. Unocic, Michael Engel, Sara E. Skrabalak
Effect of Lattice Mismatch and Shell Thickness on Strain in Core@Shell Nanocrystals
Nanoscale Advances 2, 1105-1114 (2020) -
Jocelyn T. L. Gamler, Alberto Leonardi, Hannah M. Ashberry, Nicholas N. Daanen, Yaroslav Losovyj, Raymond R. Unocic, Michael Engel, Sara E. Skrabalak
Achieving Highly Durable Random Alloy Nanocatalysts through Intermetallic Cores
ACS Nano 13, 4008-4017 (2019) -
Alberto Leonardi, Michael Engel
Particle Shape Control via Etching of Core-Shell Nanocrystals
ACS Nano 12, 9186-9195 (2018)

Directional entropic and enthalpic forces
Directional binding is the foundation of organic chemistry, molecular biology, and can lead to liquid crystalline order. More recently directionality was studied in the context of colloidal and nanoscale building blocks, which are called patchy particles if they exhibit preferential geometric attachment. We introduced the concept of directional entropic forces and entropically patchy particles, in which the particle shape itself is the cause of the geometric attachment. Entropic patchiness is a means to rationalize the phase behavior of many anisotropic particles.
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Lilian C. Hsiao, Benjamin A. Schultz, Jens Glaser, Michael Engel, Megan E. Szakasits, Sharon C. Glotzer, Michael J. Solomon
Metastable Orientational Order of Colloidal Discoids
Nature Communications 6, 8507 (2015) -
Greg van Anders, N. Khalid Ahmed, Daphne Klotsa, Michael Engel, Sharon C. Glotzer
Understanding Shape Entropy through Local Dense Packing
Proceedings of the National Academy of Sciences 111, E4812-E4821 (2014) -
Greg van Anders, N. Khalid Ahmed, Ross Smith, Michael Engel, Sharon C. Glotzer
Entropically Patchy Particles: Engineering Valence through Shape Entropy
ACS Nano 8, 931-940 (2014) -
Pablo F. Damasceno, Michael Engel, Sharon C. Glotzer
Crystalline Assemblies and Densest Packings of a Family of Truncated Tetrahedra and the Role of Directional Entropic Forces
ACS Nano 6, 609-614 (2012)

Amorphous photonic band gap materials
Photonic materials create fascinating structural color effects in plants, insects, and mammals. An important characteristic is the appearance of a photonic band gap, a frequency band where the propagation of light is strictly prohibited. We study photonic band gap formation in amorphous dielectric materials. We used numerical calculations of the photonic density of states in materials where the dielectric structure is derived from hard and hyperuniform disk patterns. A central goal is to better understand the role of short-range order for tailoring Bragg scattering at the isotropic Brillouin zone.
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Luis S. Froufe-Perez, Michael Engel, Juan José Saenz, Frank Scheffold
Band Gap Formation and Anderson Localization in Disordered Photonic Materials with Structural Correlations
Proceedings of the National Academy of Sciences 114, 9570-9574 (2017) -
Luis S. Froufe-Perez, Michael Engel, Pablo F. Damasceno, Nicolas Muller, Jakub Haberko, Sharon C. Glotzer, Frank Scheffold
Role of Short-Range Order and Hyperuniformity in the Formation of Band Gaps in Disordered Photonic Materials
Physical Review Letters 117, 053902 (2016)
