Development of ‘Green and Clean’ Reaction Media for Inorganic and Organic Nanomaterials

We have developed new water-in-CO₂ microemulsions under supercritical conditions of CO₂ bulk phase. Using fluorinated AOT surfactants and hydrogenated n-butanol as a cosurfactant, microemulsion solutions were obtained which could dissolve large amount of water as large as W₀=49 at 35°C. Where W₀ is the molar ratio of water-to-surfactant. Using varieties of surfactants and amount of cosurfactant, the composition of microemulsion has been established which gives capabilities to prepare different size nanomaterials in the range of 3 to 10 nm depending on the size of the core of microemulsion droplets. Size of the nanomaterials can be controlled with narrow size distribution by adjusting the W₀ values of microemulsion solution. In this presentation, I shall describe the preparation of water-in-CO₂ microemulsions as a function of water content, pressure of CO₂, surfactant concentration, and amount of cosurfactant added. The new CO₂ microemulsions will replace the existing conventional media used for preparation of nanomaterials until now because of non-toxic, cheap, easily recyclable bulk phase CO₂ used in these solutions at moderately low temperature of 35°C.