0936384_Brock_y

1. It Only Takes a Drop:  Programmable nanoparticle monolayers at the air-solution interfaceJoel D. Brock, Cornell University, DMR 0936384 Broader Impacts: DNA-coated nanoparticles can be regarded as highly functionalizable and programmable agents to rationally design new metamaterials. This study revealed the part of the phase diagram where nanoparticle assembly via DNA binding becomes most favorable and also indicates how electrostatic screening can be used to fine tune DNA conformation, affecting the lattice constant of the whole nanoparticle assembly. The investigators also proved that “lab-on-a-drop” measurements constitute a unique opportunity to study the response of the Gibbs layers to nanoparticle and counterion concentration. This can be done without lattice distortions that may occur, if the layer is stuck to a solid substrate, or in some other non-equilibrium situation, as temperature and vapor pressure were stabilized by the sample cell.   Michael J. Campolongo, Shawn J. Tan, Detlef-M. Smilgies, Mervin Zhao, Yi Chen, Iva Xhangolli, Wenlong Cheng, and Dan Luo; "Crystalline Gibbs Monolayers of DNA-Capped Nanoparticles at the Air–Liquid Interface", ACS Nano 5, 7978-7985 (2011). DNA chains were anchored on the surface of citrate-coated gold nanoparticles by ligand exchange via a thiol bond. Particles were kept in thermal equilibrium using a “lab-on-a-drop” method that allows x-rays to study the interaction of the DNA coronae undisturbed by environmental influences. CHESS DMR-0936384 2012_1