NIRT: Multi-Scale Simulation of Nanoparticle Aggregation for Scale Up of High-Rate Synthesis Methods

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AbstractCTS-0403864R. Fox, Iowa State UniversityNIRT: Multi-Scale Simulation of Nanoparticle Aggregation for Scale Up of High-Rate Synthesis MethodsNanoparticles are the basic building blocks for many novel materials. In nearly all high-rate synthesis methods for nanoparticles, chemical precursors are brought together by turbulent mixing to form particle nuclei that grow rapidly due to surface addition and aggregation. Next-generation applications of nanoparticles will require precise control of product quality when synthesis methods are scaled up. Predicting nanoparticle aggregation starting with detailed knowledge of particle surface chemistry and the time-dependent shear rate in a turbulent flow is the key step for scale up of high-rate synthesis methods. In this project, an international, interdisciplinary team of scientists and engineers will develop and validate multi-scale computational tools based on fundamental chemical and physical models that can predict a priori the properties of nanoparticle clusters produced after scale up of high-rate synthesis methods.The computational approaches range from quantum calculations of particle surface chemistry (atomic to molecular scale), to Brownian dynamic simulations of nanoparticle aggregation with and without shear (nano to micron scale), to direct-numerical and large-eddy simulations of the particle size distribution in turbulent flow (micron to macro scale). The experimental validation approaches range from direct measurements of the interparticle potentials using atomic force microscopy, to measurements of the cluster size distribution in quiescent systems using light scattering, to in situ measurements of cluster size and fractal dimension in Taylor-Couette flow.The model system to be investigated is monodisperse colloidal functionalized latex nanoparticles. The nanoparticles will be synthesized in our lab with a view to carefully modulate and understand aggregation mechanisms in this system. Three types of functionalized nanoparticles will be investigated: (1) unmodified latex, (2) sulfonated latex, and (3) carboxylated latex; and the extent of surface coverage will be varied to probe the effect of surface chemistry on nanoparticle aggregation mechanisms. The addition of these functionalities modifies the hydrophobic surface of the latex particles, and enables interrogation of aggregation mechanisms in mixtures of unmodified and modified nanoparticles. The choice for the model system is also driven by our ability to perform detailed ab initio quantum calculations of surface-surface, surface-molecular, and molecular-molecular interactions between surface-modified latex nanoparticles.Using this detailed atomistic description of nanoparticle surface chemistry, we will develop coarse-grainedinterparticle potential models for use in Brownian dynamics simulations to predict cluster size distribution and cluster morphology in shear flow. From this information, aggregation kernels needed for the Smoluchowski equation will be extracted and implemented in the general dynamic equation for particle aggregation in turbulent flow. At each step of model development, appropriate experimental validation tests will be carried out to ensure that the multi-scale simulation tools agree with reality.Intellectual merit of the proposed activity: The rational design and scale up of nanoscale synthesis and processing methods is a crucial step towards the commercial viability of nanoparticles for widespread technological applications. By developing and validating multi-scale, multi-phenomena simulation tools, this project will demonstrate for the first time the capability to predict the properties of nanoparticles produced by high-rate synthesis methods after scale up starting from the fundamental chemical and physical theoretical models. The interdisciplinary team assembled to attack this problem is uniquely qualified to bridge the enormous range of length and time scales, and the corresponding numerical and experimental challenges, that are required to accomplish successfully this task.Broader impacts of the proposed activity: This project will lead to the development of new courses in Nanoscale science and technology at the participating universities. Undergraduate education will be enhanced through an REU program in computational chemistry, physics and mathematics at Iowa State; and outreach programs (CoS, APEXES, MCSRO) at the University of Minnesota. Graduate education will be enhanced by internship programs with industrial and international partners, and the IGERT for nanoparticle science and engineering at Minnesota. K-12 outreach and recruitment of minorities and women will be actively pursued through participation in the LEAD, Science Bound, and PWSE programs at Iowa State, and similar programs at Minnesota. Results from the project will be disseminated broadly through the industrial and international partnerships, dedicated sessions at professional meetings, annualnanoscale science and engineering workshops, and archival publications. Research and education themes addressed in this proposal: (in order of significance)1. Manufacturing Processes at the Nanoscale2. Multi-scale, Multi-phenomena Theory, Modeling and Simulation at the Nanoscale3. Nanoscale Processes in the Environment