Hydrothermal Synthesis of Aqueous Sols of Lactic Acid-Stabilized Nanocrystalline Hafnium Dioxide and Their Enzyme-Like Activity

A method was developed to produce aqueous sols of nanocrystalline hafnium dioxide (with a hydrodynamic diameter of 20–35 nm), which were stabilized by lactic acid (lactate ions) and characterized by high colloidal stability (ζ-potential –29 mV). The method is based on hydrothermal treatment of a preliminarily obtained complex compound of hafnium with lactic acid in the presence of urea at temperatures of 180 and 220°C for 48 and 96 h. Chemiluminescent analysis in a model reaction of luminol oxidation determined that nanocrystalline hafnium oxide in the sols exhibits dose-dependent prooxidant activity toward hydrogen peroxide and thus has peroxidase-like properties.