Suspension Stability and Aggregation Kinetics of Sol-Gel Titania Nanoparticle Doped with Rare Earth (Er, Yb) Element: The Effect of pH and the Ultrasound

Hydrothermally assisted sol-gel has been successfully used to prepare pure and doped titanium dioxide (TiO2) nanopowders with ytterbium (Yb) and/or erbium (Er). Co-doped nanopowders were prepared with varying Yb concentrations of 5 and 10 mol% and a fixed 5 mol% Er concentration. Doped nanopowders were made with a 5 mol% Er or 5 mol% Yb concentration. The effect of pH and ultrasound has been determined after the preparation of nanoparticles (NPs) suspensions in water, ethanol, methanol and butanol. Without causing any structural changes, the dopants are integrated into the TiO2 matrix through the crystallization of the resulting nanopowders in an anatase form. These are spherical in shape and in size between 10 nm and 15 nm. The prepared suspensions show an improvement in stability with ultrasound and with a pH = 3. After measuring the absorption with UV-Vis spectrophotometry, it can be noted that the suspensions of Er-Yb (5–10%):TiO2 nanoparticles obtained are relatively stable more than 20 days.