Water/Supercritical CO2 Microemulsions with a Fluorinated Double-tail Surfactant for Syntheses of Semiconductor Ultrafine Particles

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A water/supercritical CO2 microemulsion (W/scCO2 μE) with a fluorinated double-tail surfactant bis (1H, 1H, 2H, 2H-heptadecafluorodecyl)-2-sulfosuccinate (8FS(EO)2) was evaluated in terms of its nanoreactor performance for synthesizing semiconductor ultrafine particles of TiO2, ZnS, and CdS. By the addition of tetraisopropylorthotitanate (TIP) in W/scCO2 μE, TiO2 ultrafine particles were successfully synthesized with a spherical shape and sizes of several tens of nanometers, which were similar to those synthesized in W/cyclohexane μE with a typical hydrocarbon double-tail surfactant AOT. Interestingly, in contrast to the μE system, TiO2 particle syntheses in liquid-crystal-like (LC-like) surfactant precipitant phase yielded a dendritical morphology of TiO2. For metal sulfide synthesis, the addition of metal nitrates as precursors in W/scCO2 μE was found to lower the maximum W0 value at which W/scCO2 μE can form, which would result from the promoted aggregation and fusion between reverse micelles, i.e., LC formation. After mixing both the W/scCO2 μEs containing metal nitrate and Na2S, metal sulfide ultrafine particles were yielded with spherical shape and sizes of several tens of nanometers. These results suggested that W/scCO2 μE with 8FS(EO)2 may become a valuable nanoreactor when further investigations reveal size-control techniques for the products.
Japan Society of Colour Materialの論文