Potential Application and Molecular Mechanisms of Soy Protein on the Enhancement of Graphite Nanoplatelet Dispersion

A stable dispersion of graphitic nanofillers in aqueous solution is an important prerequisite for the applications and development in graphitic nanofiller-based nanocomposites. Traditional treatments of the graphitic surfaces with different chemicals are time and energy consuming, and more seriously raise great environmental concerns. In this study, through combination of simulations and experiments we demonstrate that the soy protein, one of the most widely available proteins from the renewable resource, when properly denatured by trifluoroethanol (TFE) and heat, can be utilized to effectively treat the graphite nanoplatelet (GNP) surface and improve the dispersion. Through molecular simulations we find that the tertiary structures of soy protein are mostly destroyed under the action of TFE at high temperature. As a consequence, most aromatic residues which are originally hidden inside the hydrophobic cores become accessible and form pp stacking interaction with the GNP surface, strengthening the adsorption of soy proteins onto the GNP surface. The adsorption of soy protein modifies the GNP surface energy, reduces the interaction force among GNPs and leads to better dispersion. Our simulation results agree with the experimental measurements on GNP dispersion. The work herein demonstrates the importance and the potential of the concept that a protein, when its structures are properly manipulated, can be exploited in nanotechnologies to improve performance and explore new functionalities.