Aqueous solutions of AOT as a dispersion medium for stabilization of SiO2 nanoparticles

• The mechanism of ionization of aqueous solutions of AOT has been determined in a wide range of concentrations. • In accordance with the DLVO theory the determining factor of stability is electrostatic repulsion. • The hydrosols formed coffee rings during evaporation of sessile droplets. • The obtained SiO 2 -AOT hydrosols can be used for the formation of various 2D materials and substrates in biosensorics. SiO 2 nanoparticles and surfactant sodium bis-(2-ethylhexyl) sulfosuccinate (AOT) are widely used in modern nanochemistry to obtain novel materials in various processes. However, only a few publications are devoted to investigation of the stabilization mechanisms of SiO 2 dispersions in aqueous AOT solutions. In this work, the surface electrical properties of SiO 2 nanoparticles and the nature of free charges in aqueous solutions were studied over a wide range of AOT concentrations (2.5∙10 –6 ÷ 2.5∙10 –2 M). The absolute value of ζ-potential of the particles increased from –42 to –58 mV, while the hydrodynamic radius remained constant and equal to ca. 40 nm. Calculations within the Derjaguin–Landau–Verwey–Overbeek (DLVO) theory revealed that stability of hydrosols is caused by the electrostatic component of disjoining pressure. Due to the repulsion of similarly charged nanoparticles and glass substrate, the hydrosols formed coffee rings during evaporation of sessile droplets. The results obtained make it possible to control surface properties of the particles, thus opening the possibility to use SiO 2 -AOT hydrosols for the formation of various 2D materials and substrates in photonics, catalysis and biosensorics.