Synthesis and growth mechanism of GeO2 particles in AOT reversed micelles

GeO2 particles with a narrow size distribution were synthesized using hydro lyzing germanium tetraethoxide (GTE) in a 2,2,4-trimethylpentane solution o f sodium bis(2-ethylhexyl) sulfosuccinate (AOT) as a function of water cont ent (R-w=[H2O]/[AOT]). Their shape was observed to be polyhedral in the abs ence of excess water, whereas it was cubic in the presence of bulk-like wat er. The size and shape varied with R-w such that the solubilized state of w ater in effect determined the growth process. In addition, by examining the time-dependent growth of GeO2, particles in a W/O microemulsion (R-w=20), we clarified that water condensation of hydrolyzed GTE is the rate-limiting step in particle growth. (C) 1999 Elsevier Science B.V. All rights reserve d.