Preparation Of Carbon Coated Metal Oxide Nanoparticles Using ‘Nanoreactor' Based On Supercritical Fluid Technology

Metal oxide nanoparticles can exhibit excellent optical and electrical characteristics,which play an important role in the fields of catalysis,information storage,medicine,photoelectronics etc.Although traditional chemical synthesis method of metal oxide nanoparticles is simple,the problem of aggregation is still unresolved which results from poor dispersion of nanophase,products pollution occurring in the preparation process and so on.In recent years,using supercritical fluid technology to prepare metal oxide nanoparticles has attracted attention.In this work,supercritical carbon dioxide enhanced solution dispersion technology?SEDS?was used to produce‘nanoreactor'as precursor which meant metal inorganic salt embed in nanopolymer,and carbon coated metal oxide nanoparticles also gained by calcined at high temperature.The main conclusions are shown in the following:?1?Using supercritical carbon dioxide as anti-solvent and acetone as solvent,the impacts of reaction pressure,solution flow rate and SC-CO₂ flow rate on the nanoreactor size were studied with full factor experiments.The results indicated that under the conditions of reaction pressure at 12 MPa,solution flow rate at 0.5 mL·min^-1 and SC-CO₂ flow rate at 40 g·min^-1,the nanoreactor size of 40 nm could be prepared,and the nanoreactor was well-distributed and well-dispersed.Determination of residual acetone in nanoreactor by HS-GC showed that it had no residual in nanopolymer.?2?The impacts of calcination of temperature on crystalline of the carbon coated metal oxide nanoparticles;the impacts of concentration of metal inorganic salts on crystal type,particle size,surface morphology,crystallinity and absorbability of samples were analyzed.The results indicated that the carbon coated metal oxide nanoparticles was well-dispersed and its average size was 25 nm.Metal oxide nanoparticles were cladded in the amorphous carbon.Carbon coated metal oxide nanoparticles showed the better photocatalytic and antibacterial activities than the pure metal oxide nanoparticles under the visible light irradiation.After photothermal tests,the results indicated that carbon coated Co₃O₄ NPs had the steady and feasible conversion efficiency and its best conversion efficiency was 51.53%.?3?Used the same method to prepared the carbon coated metal oxide nanocomposites.The impacts of different ratios of the two metal salts on the carbon coated metal oxide nanocomposites was analyzed.The samples at different preparation conditions were tested to research its photocatalytic activities,antibacterial activities and photothermal conversion efficiency.The results showed that the shape of the carbon coated metal oxide nanocomposites was spherical or subglobose with uniform particle size of 20 nm.The carbon coated metal oxide nanocomposites showed the better photocatalytic,antibacterial activities and photothermal conversion efficiency than the carbon coated metal oxide nanoparticles.The cytotoxicity analysis of the carbon coated metal oxide nanocomposites synthesized showed that the carbon coated metal oxide nanocomposites possessed low cytotoxicity and good biocompatible.