Controlling Order within Nanoparticle Monolayers Fabricated by Electrophoretic Deposition James Dickerson, Vanderbilt University, DMR In this CAREER award work, we developed techniques to measure the degree of ordering that we achieved in monolayers of nanoparticles, produced by electrophoretic deposition. This insight will help us gain greater control over the arrangement of nanoparticles within these monolayer films. Highlights The first controllable fabrication of nanoparticle monolayers (across square millimeters of surface area) using electrophoretic deposition. The development of techniques to measure the ordering of the films, which will act as tools for understanding the mechanisms behind ordering. Control over ordering within the film, facilitated by using substrates with nanoscale features. The developed techniques will facilitate our understanding of the underlying forces (Coulomb, dipolar, van der Waals, etc.) that govern ordering among nanoparticles within a monolayer. Such insight could lead to the production of devices, based on ordered nanoparticle monolayers and multilayers. A. J. Krejci, J. Mandal, and J. H. Dickerson, Patterned Substrates to Facilitate Long-Range Ordering in the Formation of Nanoparticle Monolayers by Electrophoretic Deposition, Applied Physics Letters 101, , 2012.Applied Physics Letters 101, , (200) 2.3 Å b a c 2.35 Å (220) a) SEM image of monolayer film of 9.6 nm iron oxide nanoparticles. b) Voronoi pattern analysis of the SEM image found in a). The pattern is color coded based on the number of sides of each Voronoi cell. Most particles have 6-sided cells, indicating hexagonal packing among the particles. c) SEM image of a monolayer deposited on substrate patterned with lines that were 80 nm, and d) 105nm in length. White ovals identify the patterned feature on the substrate. The image suggest that the patterns help control the ordering of the film 1

Controlling Order within Nanoparticle Monolayers Fabricated by Electrophoretic Deposition James Dickerson, Vanderbilt University, DMR Over the past year, high school, undergraduate, and graduate students have worked on developing the techniques to measure and to control the formation of ordered and disordered monolayers and multilayers of nanomaterials, using electrophoretic deposition. Funding from this grant supported the summer research experiences of two excellent rising sophomores (Colin G. W. Thomas, top left, and Jyotirmoy Mandal, top right), both of whom are co-authors of manuscripts detailing the techniques for analyzing SEM images using Voronoi tessellations and the techniques to control ordering using patterned substrates.. Support from this grant has allowed the senior graduate student (Alex J. Krejci, bottom) to present his research in talks at the 4 th International Conference on Electrophoretic Deposition in Puerto Vallarta, Mexico and at the American Physical Society March Meeting in Boston, MA. Also, this grant has allowed the graduate student to travel to and conduct research at the Center for Functional Nanomaterials, Brookhaven National Laboratory.