Nanostructure materials have many special physical and chemical properties and potential important applications owing to their unique particle sizes and surface effects. In the past decades, many different techniques have been developed for preparation of nanoparticles. However, most research were focused on the preparation of noble metal and semiconductor nanoparticles. Little work on the preparation of nanocrystals of transitional metals and their oxides has been reported in the literature. Recently, the preparation, characterization, and application of some transitional metal oxide nanocrystals, such as various cobalt oxide nanocrystals, have attracted an increasing interest due to their importance in technological applications based on their magnetic or catalytic properties.
In recent years, to easily obtain crystalline Co3O4, many methods such as sol-gel, spray pyrolysis, chemical vapor deposition, chemical precursor routes, electrochemical and sonochemical synthesis were developed.
It is well known that the contact non-equilibrium plasma offers enhanced opportunities over solution chemistry for synthesis new nanomaterials and tailoring their functional properties. The use of contact non-equilibrium plasma and aqueous electrolytes system (low-temperature glow discharge electrolysis), when the cathode is in a liquid phase and the anode is at some distance from the liquid surface, makes it possible to carry out non-equilibrium oxidation processes in the liquid being treated. In the liquid media the oxidation processes occur which cannot be realized by using conventional electrolysis or by the action of arc-crown-, townsend- or barrier-discharge plasma on the liquid.
We report a simple method for preparation of cobalt oxide by usage contact non-equilibrium plasma. The theoretical and experimental exploration of cobalt chloride hydrolysis as a first step of receipt of cobalt compounds: the distribution of cobalt ions, its constituents and cobalt hydroxide solubility depending on the pH and ionic strength was calculated. It is found that the final pH of the precipitation of cobalt hydroxide has range 8.2-9.0 and depending on the ionic strength is equal to 8.2 and 9 when I = 0, I = 1, respectively.
The patterns of changes of the oxidation – reduction potential and pH of cobalt oxide when processing low-temperature non-equilibrium plasma were investigated. The phase composition of plasma-chemical obtained cobalt compounds investigated by X-ray and thermal analyzes. The main part of the obtained product was cobalt oxide Co3O4. X-ray diffraction (XRD) studies revealed pure phase with growth of Co3O4 particles along  and  directions. The microscopic analysis shows that the sizes of obtained cobalt compounds is in the nanometer range.