CAREER: Molecular-Based Engineering of Nanoparticle Self-Assembly

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ABSTRACT - 0448767The goal of the CAREER proposal is to establish a rigorous scientific base that enables better control of nanoparticle self-assembly for nanotechnology. Possessing novel properties unavailable in either isolated molecules or bulk materials, nanometer-sized particles are one of the most important ingredients in nanotechnology and have been recognized as an ideal basis for next-generation nanodevices and smart materials. To fully realize their potential, nanoparticles must be fabricated into multidimensional ordered arrays and predesigned nanostructures. Significant progress has been made recently. However, current avenues of nanoparticle fabrication still remain highly empirical and produce only partially satisfactory results. Existing studies nevertheless revealed clearly the pivotal role of atomic-scale characteristics in nanoparticle self-assembly. This points out not only the value of fundamental research but also a fruitful direction for future studies. The proposed research will first perform molecular dynamics simulations with atomistic models that incorporate important atomic-scale characteristics to focus on early self-assembly stages of surfactant-capped nanoparticles. The results will provide microscopic insights into the initial phase of self-assembly and will be utilized as input to Brownian dynamics simulations to investigate larger-scale phenomena and issues in nanoparticle self-assembly, and to statistical mechanics for the attempt to identify favorable self assembly conditions. New nanobuilding unit (nanochain) and nanofabrication strategies (stepped and grooved surfaces) are also proposed based on theoretical analyses. Their feasibilities and processing protocols will be carefully assessed in this project.Intellectual merit: Theoretical study in the respect of nanoparticle self-assembly is important but still scarce. Because of the complexity in microscopic detail and in the time and length scales involved, it is a major challenge not only to conventional macroscopic theories but also to molecular simulation. This proposal employs a multi-scale, multi-phenomena modeling approach that combines the advantages of finer-scale molecular dynamics simulation, larger-scale Brownian dynamics simulation, and a new framework of statistical mechanics. The roles and relative importance of atomic-scale characteristics in nanoparticle self-assembly will be investigated in detail. The new framework of statistical mechanics for nanoparticle systems will be substantiated. The new nanofabrication ideas will be carefully assessed. The proposed research thus presents a range of theoretical studies that has not been attempted for the investigation of nanoparticle self-assembly.Broader impact: The proposed research will provide a comprehensive characterization and understanding of nanoparticle self-assembly at a level that has not been achieved before. Thegenerated results and insights will be useful to improve current nanofabrication avenues and to offer suggestions for future nanotechnological development. The proposal also has a strong educational component that effectively integrates the PI's research expertise into education at several levels on a continuous basis. It enriches Chemical Engineering education with molecular simulation by implementing a required undergraduate course entitled "Molecular Chemical Engineering" and a senior/graduate elective course entitled "Molecular Simulation in Engineering and Science." A Molecular Simulation Laboratory is also being developed to bring molecular simulation closer to students. These efforts are entirely new in the Department of Chemical and Biological Engineering and at the University of Missouri-Rolla, and will begin to put in place a new culture for students to look at engineering systems and problems from molecular perspectives. The PI will continue to engage undergraduate students in fundamental research and encourage them to pursue advanced studies. Two undergraduate researchers will be sponsored by the project and part of their job is to talk to high school students to promote their interest in engineering education and fundamental research. The educational plan will have a significant impact because molecular simulation has evolved into a practical tool of tremendous academic and industrial significance and because modern technologies have made molecular perspectives imperative by adopting bottom-up approaches.