Solution Synthesis And Property Studies On Cobalt Oxide Nanomaterials With Different Morphology

The spinel structure cobalt oxide （Co₃O₄） is an important magnetic p-type semiconductor,which has broad application prospects. The development on its simple and mild preparationand morphology-controlled strategy are important topics, which are worthy of study fortheoretical research and application. The controlled synthesis of nanocrystals with a singlesize and shape is important for constructing nanostructured materials by bottom to toptechniques.In this paper, Co₃O₄nanoparticles were prepared via a green synthesis method in an opensystem and these nanomaterials possessed a series of characteristic parameters and wouldhave many potential applications. We also did in-depth mechanism study of each reactionsystem. The main research results and innovations of the thesis are given in the followingparts：Firstly, cobalt hydroxycarbonate nanorods were synthesized by precipitation of cobaltacetate （Co（CH₃COO）₂） and sodium carbonate （Na2CO3） with ethylene glycol （EG）. Co₃O₄nanorods with a diameter of10nm and a length of120nm were obtained by oxidation of thenanorod-shaped cobalt hydroxycarbonate precursor with oxydol （H2O2）. We studied theeffective synthetic conditions for the morphology and structure of samples, especially，westudied the role of ethylene glycol. Based on the diffusion principle of ultrasonic wave,samples were dispersed into different solvents, we studied their suspension stability. In thiswork, the adsorption and degradation of rhodamine B （RhB） by Co₃O₄nanorods were studiedby detecting UV-Vis spectral changes of RhB solution.Secondly, nanometic Co₃O₄powders made of150nm flakes were directly precipitatedfrom Co²⁺aqueous solutions under alkaline and oxidizing conditions. We added succinic acid（（CH₂COOH）₂） coordinating with Co²⁺to form complex, which may control the hydrolysisrate and thus significantly influenced the morphology of the products. We studied the effectsof succinic acid, sodium hydroxide, pH and the adding methods on the morphology andstructure of samples, and that could indicate the model of action. We also developed differentsynthetic routes of Co₃O₄nanoflakes. Suspension stability of samples and degradation ofrhodamine B were studied, too.Finally, Co₃O₄nanoparticles with a diameter of35nm were synthesized in aqueous atroom temperature. In this process, precursors were not synthesized. We added sodiumhydroxide （NaOH） to Co²⁺aqueous under oxidizing condition, Co₃O₄nanoparticles directlyprecipitated. We studied the effects of reaction time, surfactants, amount and concentration ofNaOH and so on. We found that PVP as surfactant was the best, the amount and concentration of alkaline drastically influenced the system. Co₃O₄nanoparticles could steadily suspend indifferent solvents due to their small size，but degradation of rhodamine B was insidiously.In conclusion，Co₃O₄nanomaterials with several dimensions and sizes were obtained byaqueous synthesis method. We innovatively synthesized small sized Co₃O₄nanoparticles atroom temperature. Our work gives an improved progress on the mild solution synthesis ofCo₃O₄nanomaterials. The synthesized methods used here are simple and the obtained cobaltoxide nanomaterials can be potential applied in areas as catalysis, degradation,electrochemistry and et al.