Applications of Molecular Structural Aspects of Gemini Surfactants in Reducing Nanoparticle-Nanoparticle Interactions.

Oppositely charged nanoparticle (NP)-nanoparticle (NP) interactions were studied by titrating sodium dodecyl sulfate (SDS) stabilized NPs with cetyltrimethylammonium bromide (CTAB) stabilized NPs at constant temperature with the help of UV-visible and dynamic light scattering measurements. CTAB stabilized NPs were systematically replaced with a series of cationic gemini surfactants to demonstrate the effect of head group and hydrocarbon tail modifications on the electrostatic interactions with SDS stabilized NPs. Introduction of the dimeric gemini head group (alkylammonium or imidazolium), spacer length, and double tail hydrocarbon length all significantly reduced the NP-NP interactions and delayed their salting-out process. They lead to the formation of stable colloidal aqueous solubilized NP-NP complexes. The results concluded that NP-NP interactions can be overcome if appropriately stabilized NPs are used to maintain their colloidal stability so as to achieve maximum applicability.