Evolution of Dispersed Systems of Metal Oxide Nanoparticles Obtained in Plasma Discharge in Liquids under the Effect of Ultrasound

In this work, nanoparticles of aluminum, copper, and titanium oxides were obtained by plasma discharge in the liquid phase (ethylene glycol, water) under the influence of intense ultrasound. Particular procedures have been developed for creating sedimentation-stable aqueous dispersed systems of nanoparticles of copper(II), aluminum, and titanium(IV) oxides. Nanoparticles are stabilized by the nonionic surfactant Tween 85 at its optimal concentration of 3 mmol/L and with a metal oxide content of up to 0.2 g/L. It has been shown that stable dispersed systems of particles are obtained by adding a surfactant to the initial system, followed by diluting it with distilled water and ultrasonic dispersion. Using scanning electron microscopy, it was shown that nanoparticles of copper, aluminum, and titanium oxides have a spherical shape. Highly stable dispersed systems with a narrow particle size distribution were obtained: 20 nm for Al₂O₃, 40 nm for CuO, and 30 nm for TiO₂ after membrane filtration of the initial dispersed systems. Electrokinetic studies have shown that the surface of nanoparticles of copper, aluminum, and titanium oxides becomes negatively charged when stabilized by Tween-85. The average value of the ξ-potential was –20 ± 5 mV. The study of the kinetics of growth and stability of nanoparticles showed that titanium oxide nanoparticles, under equal conditions, have higher aggregation stability compared to copper and aluminum oxides. The stability time of the obtained samples was approximately 1.5 months.