Varying the Surface Charges of Gold Nanoparticles in Span 80, AOT, and Span 80 + AOT Micellar Systems in n-Decane

Gold nanoparticles with different diameters of the metal core are obtained by reducing HAuCl₄ with hydrazine in reverse emulsions stabilized by Span 80 (9.4 ± 0.4 nm), AOT (6.1 ± 0.2 nm), and an equimolar Span 80 + AOT mixture (10.0 ± 0.2 nm). After synthesis, only the nanoparticles in the AOT solutions (ζ potential 16.8 ± 0.9 mV) display electrophoretic mobility. Nanoparticles in the form of a small-volume liquid phase concentrate are also separated from excess reagents and by-products by concentration (non-aqueous electrophoresis, or centrifugation) and diluted with micellar solutions (Span 80, AOT, and Span 80 + AOT mixture) or pure solvents (n-decane and chloroform). As a result, 24 organosols are obtained, including ones with positive (11), negative (8), and uncharged (5) nanoparticles. Of particular potential interest are organosols that have the same macrostructure in terms of surfactants, but with oppositely charged gold nanoparticles (7 pairs of organosols are obtained).