Controlled Nucleation of K3Fe(CN)6in Isolated Microdroplets at Liquid−Liquid Interface

Abstract

We have investigated the crystal nucleation behavior of potassium hexacyanoferrate(III) (KFC) in an isolated aqueous microdroplet surrounded by a decanol medium which is isothermally driven to supersaturation by water transport from the droplet, to examine the influence upon KFC nucleation by self-assembled surfactant monolayers at the liquid−liquid interface. The nucleation behavior was studied by measurement of the level of supersaturation required for the onset of crystallization (Sonset) based on microscopic observation. For KFC crystallization in the absence of surfactant, it was found that Sonset was 1.74 ± 0.13. This value was independent of droplet initial size (80−160 μm) and initial KFC concentration (10−40%). In the presence of a minimum threshold concentration of octadecylamine (ODA) in decanol, the Sonset value was diminished significantly (1.41 ± 0.06), indicative of templated nucleation acceleration. Additionally, the crystal habit for KFC grown in the presence of ODA monolayer was markedly...