(4dw) Understanding Solutes, Surfactants, and Nano-Particles in Bulk and At Interfaces Using Molecular Simulations

Many enabling technologies haven been realized with the new class of materials (graphene, nanotubes, quantum dots, fullerenes, fullerene derivatives) within past couple of decades. However, the true potential of such materials is not fully exploited owing to the lack of understanding of how such materials aggregate and interact in bulk and at different interfaces. To understand such interactions at molecular level (from electronic, materials, and biological perspective) is becoming increasingly important to furthermore the increase in applications of these new class of materials.

Towards this end, we employed molecular dynamics simulations within my graduate studies to understand surfactant aggregates on nanotubes with different curvature,^[1-5] graphene,^[6] and compared them to other regular surfaces like graphite and silica with varying levels of hydroxylation.^[7-11] Our results from the simulations of sodium dodecyl sulfate, sodium dodecyl benzene sulfonate, and flavin mononucleotide surfactants on carbon nanotubes (CNTs) provided the understanding of the surfactants aggregate structure on CNTs and how those aggregate structures are affected by changing curvature, ions, and concentration. SDS aggregates on graphene substrate illustrated the effect of lateral confinement and edge effects of the substrate on the admicellar characteristics.

Understanding nano-particle interactions with the surface are important when such particles flow within pores, especially in hydraulic fracturing. We evaluated such flows in structured and unstructured porous media using Lattice-Boltzmann methodology and nano-particle flow was modeled by employing Lagrangian tracking methodology with different adsorption kinetics. Finally, with Prof. Brédas group at the Georgia Institute of Technology, we are trying to understand how molecules arrange in various solvents, mixing and aggregation of variety of small conjugated molecules for applications in organic photovoltaics using classical molecular dynamics, semi-empirical, and density functional simulation methods.^{[12, 13]} We are also trying to understand how the presence of fullerene derivatives affects the mechanical properties of thin films of polymer-fullerene photoactive layer.

Drawing from my experiences and expertise, apart from collaborating and continuing my previous research I am interested to expand my research into: 1.) Fundamental understanding of how molecular scale properties and interactions (shape, size, dispersion and electro-static) drive aggregation in various solvents. 2.) Effect of ligands on the diffusion limitations on nano-particle catalysts. 3.) The interfacial phenomenon of water and organic solvents next to graphene oxide, and various clay and shale surfaces at atomic level using both quantum and classical simulations. And also, study the transport of solutes in such nano-pores for understanding the shale-solvent interactions at both molecular level and continuum level using a combination of techniques like non-equilibrium molecular dynamics simulations and Lagrangian tracking methods. I would like to investigate shale-surfactant and shale-polymer interactions to better understand the fundamental processes involved in hydraulic fracturing.

PhD Advisor: (2005 - 2010)   Prof. Alberto Striolo (University of Oklahoma)

Post-Doctoral Advisor (2010 - 2011) Prof. Dimitrios Papavassiliou (University of Oklahoma)

Post-Doctoral Advisor (2011 - Present) Prof. Jean-Luc Brédas (Georgia Institute of Technology)

[1]          M. Suttipong, N. R. Tummala, B. Kitiyanan, A. Striolo, The Journal of Physical Chemistry C 2011, 115, 17286.

[2]        N. R. Tummala, B. H. Morrow, D. E. Resasco, A. Striolo, ACS Nano 2010, 4, 7193.

[3]        N. R. Tummala, A. Striolo, ACS Nano 2009, 3, 595.

[4]        N. R. Tummala, A. Striolo, Physical Review E (Statistical, Nonlinear, and Soft Matter Physics) 2009, 80, 021408.

[5]        M. Suttipong, N. R. Tummala, A. Striolo, C. S. Batista, J. Fagan, Soft Matter 2013, 9, 3712.

[6]        N. R. Tummala, B. P. Grady, A. Striolo, Physical Chemistry Chemical Physics 2010.

[7]        N. R. Tummala, L. Shi, A. Striolo, Journal of Colloid and Interface Science 2011, 362, 135.

[8]        L. Shi, N. R. Tummala, A. Striolo, Langmuir 2010, 26, 5462.

[9]        N. R. Tummala, A. Striolo, The Journal of Physical Chemistry B 2008, 112, 1987.

[10]      D. Argyris, N. R. Tummala, A. Striolo, D. R. Cole, The Journal of Physical Chemistry C 2008, 112, 13587.

[11]      R. Parthasarathi, N. R. Tummala, A. Striolo, The Journal of Physical Chemistry B 2012, 116, 12769.

[12]      B. H. Wunsch, M. Rumi, N. R. Tummala, C. Risko, D.-Y. Kang, X. Steirer, J. Gantz, M. M. Said, N. R. Armstrong, J. L. Brédas, D. Bucknall, S. R. Marder, Journal of Materials Chemsitry C 2013, Submitted.

[13]      N. R. Tummala, Y.-T. Fu, S. Mehraeen, C. Risko, J. L. Bredas, Adv. Funct. Mater. 2013, DOI:10.1002/adfm.201300918.