Engineering nanoparticle shape and reaction rates: Multiscale modeling, simulation and applications


Nanoparticles show new and interesting properties different from bulk materials due to their extremely small size (diameter), large specific surface area and spatial anisotropy. It is thus critical to understand the variables that control its synthesis, leading to a desired application. Control of mean nanoparticle size, particle size distribution and specially, anisotropic particle shapes - like cylindrical nanorods, is the first step in many of these applications, involving enhanced adsorption and reaction rates.

To gain further insight into the mechanism of formation of nanoparticles, we have already developed models on how individual nanoparticles form by processes like multiphase mass transfer, reaction, nucleation, Brownian collision, surface growth, coagulation and Ostwald ripening, followed by interparticle forces and differential growth rates along different crystal facets, leading to anisotropic particles, like nanorods.

With the above mechanism in place, in this project, one has to build on Rajdip Bandyopadhyaya (RB) research group's existing mesoscale mathematical models (population balance equations) and computer simulation (kinetic Monte Carlo) codes to apply for different anisotropic nanoparticles. In conjunction, one can also carry out experiments, if required, involving other complex nanostructures, like core-shell or oval and flower-shaped nanoparticles, besides cylindrical nanorods. Copper/silver/gold as metallic and iron oxide/zinc oxide/silica as metal oxide nanoparticles will be considered as typical model systems, since we are already using them, for different applications, like, chemical sensing, water purification devices or for drug delivery.

This will be coupled with molecular level simulations of Abhijit Chatterjee (AC) research group's repertoire, using molecular dynamics and equilibrium Monte Carlo simulations, which will give the requisite information for calculating the nucleation, nanoparticle growth rates and coagulation kernels, respectively, required as inputs for the mesoscale models of RB group. So, this will be a collaborative project between RB and AC groups, with joint supervision by both.

Thus, the student can only perform multiscale computational research (using molecular dynamics, population balance equation or Monte Carlo simulation) or do a combination of experiments and modeling. Depending on the student's interest, there would be further scope to use the model and simulation predictions with available or new experimental data, for improving these exciting applications of nanotechnology.

Finally, exploring whether anisotropic particles, like nanorods, can display enhanced reactivity, is of paramount importance, as it will open up a new paradigm in reaction engineering. This will lead to enhancement in rates of existing or new chemical reactions, utilizing nanorods as catalysts. Modeling different atomic migration/diffusion rates on different crystal facets (AC group) of nanorods will be a key input to explain the different chemical reactivities of different nanostructure shapes, like nanorods (RB group).