Nanoscale particles have shown broad applications in energy, coatings, sensors, medicine, and optoelectronics. Realizing their enormous potential requires the organization of nanoparticles in specific one-, two- or three-dimensional patterns that can enhance their properties or even provide new properties. In nature, molecules can spontaneously organize into larger structures with fascinating complexities and functions. However, there remain challenges in self-organizing nanoparticles into hierarchically ordered nanostructures as molecule does. The NSF project entitled, “Molecular-mimicking Self-assembly of Inorganic Nanoparticles Tethered with Charged Block Copolymers,” aims to develop a deeper understanding of the interactions between nanoparticles grafted with block copolymers in order to achieve better organization of these particles. Herein specific objectives include (i) organization of polymer-modified nanoparticle into molecular-like clusters; (ii) further organization of these nanoscale clusters into larger ordered structures; and (iii) exploitation of the collective properties of assembled nanoparticles.

In the three-year period of this project, we have successfully accomplished our project objectives. We first explored the interactions between two types of nanoparticles modified with block copolymers carrying different charges and functional groups. Our results showed that appropriate design of polymer ligands (e.g., molecular weight, block length, functional group density, grafting density) enabled the formation of defined clusters with controlled size and symmetry. A correlation between building block design and assembly structures was established on the basis of our characterization and simulation studies. We further studied the self-organization of nanoparticle clusters with designed surface chemistry into nanoparticle ensembles at the liquid-liquid interface. The association modes of the clusters were found to be determined by the regional hydrophobicity on the surface of the clusters. Moreover, we evaluated the optical coupling interaction between nanoparticles in the clusters and in the larger assembled structures. Our results indicate that the collective response of nanoparticle ensembles is strongly dependent on the interparticle spacing and spatial organization of nanoparticles.          

The project has supported one female PhD student over the grant period, as well as two male PhD students for certain period of time. Among them, one student is working towards his PhD graduation; and two students received their PhD degrees in the Fall of 2015 and 2017, respectively. The project has also provided research opportunities for three undergraduate students and one local high school student. Results have been published on scientific journals and shared on international meetings including on the 253^th and 254^th American Chemical Society National Meeting, the 7th International Conference for Colloids and Interfaces, the 2016Nano Korea Symposium, and the Mid-Atlantic Micro/Nano Alliance (MAMNA) Symposium.

Last Modified: 09/29/2018
Modified by: Zhihong Nie