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

Abstract

A water/supercritical CO 2 microemulsion (W/scCO 2 μE) with a fluorinated double-tail surfactant bis (1H,1H,2Η,2H-heptadecanuorodecyl)-2-sulfosuccinate (8FS(EO) 2 ) was evaluated in terms of its nanoreactor performance for synthesizing semiconductor ultrafine particles of TiΟ 2 , ZnS, and CdS. By the addition of tetraisopropylorthotitanate (TIP) in W/scCO 2 μE, TiO 2 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, TiO 2 particle syntheses in liquid-crystal-like (LC-like) surfactant precipitant phase yielded a dendritical morphology of TiO 2 . For metal sulfide synthesis, the addition of metal nitrates as precursors in W/scCO 2 μE was found to lower the maximum W 0 value at which W/scCΟ 2 μE can form, which would result from the promoted aggregation and fusion between reverse micelles, i.e., LC formation. After mixing both the W/scCΟ 2 μEs containing metal nitrate and Na 2 S, metal sulfide ultrafine particles were yielded with spherical shape and sizes of several tens of nanometers. These results suggested that W/scCΟ 2 μE with 8FS (EO) 2 may become a valuable nanoreactor when further investigations reveal size-control techniques for the products.