Insights on ligand interactions with titanium dioxide nanoparticles via dynamic light scattering and electrophoretic light scattering

Abstract

Titanium dioxide nanoparticles (NPs) have become widely used and studied in industry, cosmetics, and water treatment; however, due to their surface charge and composition, uncoated nanoparticles often aggregate and settle in a solution. This leads to loss of function and suspension, abandoning the NPs' properties that make them ideal for many applications. Loss of NP suspension can also complicate analysis of solutions containing nanoparticles. Therefore, titanium dioxide nanoparticles are good candidates for surface coatings that enable hydrophilic interactions and improved suspension. Many coating processes require complex synthesis methods and begin with titanium dioxide precursors rather than with already synthesized nanoparticles. The method presented herein examines additive processes that may increase suspension capabilities and inhibit loss of function through aggregation of large nanoparticles (50±25nm). Nineteen chelating organic compounds were tested via a 1, 2, or 3 equivalent additions to pristine, unmodified TiO2 nanoparticles in solution. Furthermore, ligands that showed the best chelating behavior were diluted and the pH was modified to understand pH dependent behavior. Dynamic light scattering and electrophoretic light scattering were used in the study of the chemical behavior of the modified TiO2 nanoparticles. Results show that nanoparticles interacting with dimethylethanolamine, dimercaptosuccinic acid, sodium citrate, dimethylglyoxime, and oxalic acid showed improved ζ-potential at a pH of 5. Physico-chemical processes are discussed in the understanding of these results.