Exploiting geometry to generate anisotropic interactions at the nanoscale and self-assembly of living clusters

Angelo Cacciuto, Columbia University, DMR 0846426

Self-assembly of nanoparticles into large, ordered aggregates holds promise for the fabrication of materials with novel functional, mechanical and optical properties. Generating new interactions between nanocomponents will greatly expand the number of structures that can be accessed via the process of self-assembly, and my group has been extremely active in this field. Among other very interesting results, these are our major accomplishments: (1)We have shown both theoretically and numerically how the curvature of nanoparticles can be exploited to control the behavior of ligands of different chemical composition tethered on its surface, thus providing a clear physical pathway to designing directionality and specificity in interparticle interactions. Fig(1).(2) We have elucidated the mechanism behind the formation of living clusters/crystals: a new active phase that forms when catalytically activated colloidal particles (nano-rockets) spontaneously assemble. These phases represent the first step towards providing functionality to synthetic nanocomponents and their finite-size aggregates. In fact, unlike the typical structures formed by Brownian particles, living crystals are able to dynamically reconfigure their structure thus mimicking the behavior of living organisms. Fig(2)

C. Tung and A. Cacciuto, J. Chem. Phys 139, 194902, (2013) [Cover of the issue] A. Cacciuto. et al. Phys. Rev. Lett. 111 245702 (2013) [Paper highlighted in Physical Review Focus and selected in the Editorial Highlights]

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Controlling the formation of anisotropic interactions byexploiting particle geometry. Here two ligands of differentlength spontaneously separate on the surface of an elongated (prolate) particle.

A snapshot of typical living clusters formed by attractive self-propelled nanoparticles.

Molecular Assembly

Angelo Cacciuto, Columbia University, DMR 0846426

Because of the National Science Foundation generous support I had the pleasure of mentoring several students in their research. Three graduate and four undergraduate students.

I have personally trained the undergraduate students in computer simulations of soft-matter, and through a computational program I have setup for this purpose, they have acquired significant skills in computer coding and numerical simulations. As such, they have actively participated in the ongoing research of my group.

We have also participated and helped developing activities for on-campus outreach organizations. We have been collaborating especially with WISC (Woman In Science at Columbia), to support their several initiatives including Girl’s Science Day, Science Saturday Starters, and other events focusing on providing high school students and under-represented groups with hands-on exposure to scientific knowledge and research in the greater New York area. Memorable were the student’s reactions to the experiments with the hydrophobic sand in water.

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a) High school students visiting our lab as part of the SummerHigh School Program:” Introduction to Materials Science and Nanotechnology” b) Some of the graduate students working in my lab.

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