In recent years the applications of gold nanoparticles in biological and medical fields such as photothermal therapy, drug delivery, and biological sensing have increased drastically. However, there is little fundamental understanding of how these nanoparticles interact with small molecules inside and outside of the body. Our work focuses on the interactions of small hydrophobic solutes with the surfactant bilayer of gold nanoparticles. The nanoparticles are synthesized via a seed mediated growth mechanism, which utilizes cetyltrimethylammonium bromide (CTAB) as the capping agent, and results in a surfactant bilayer of CTAB on the surface of the gold. The goal of this research is to determine the partitioning coefficient of hydrophobic molecules into the CTAB bilayer of both nanospheres and nanorods. The molecules, 1,5-dihydroxynaphthalene and 2,3-dihydroxynaphthalene have been used to determine the amount of molecule that partitions at a specific gold nanoparticle to molecule ratio. By determining the partitioning of the molecule at several ratios both the partitioning coefficient (K) and the number of molecules that partition into the surfactant bilayer (C<sub>max</sub>) can be determined. Preliminary results suggest that the differences in size and polarity of the 1,5-dihydroxynaphthalene and 2,3-dihydroxynaphthalene cause a significant difference in the K and C<sub>max</sub> values of these molecules. This gives insight about the impacts that molecular properties have on the partitioning of molecules into the bilayer. In addition, data shows that differences in the partitioning between spheres and rods also exist.  Through the use of these partitioning experiments, it will be possible to indirectly probe the structure of the CTAB bilayer.

Characterizing the partitioning of hydrophobic solutes into the surfactant bilayer on gold nanorods

249th National Meeting (2015)

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