Kinetic Analyses of Colloidal Crystallization in Alcoholic Organic Solvents and Their Aqueous Mixtures As Studied by Reflection Spectroscopy

Abstract

Reflection spectroscopy is used for the kinetic analyses of the nucleation and growth process of colloidal crystals of silica spheres (110 nm in diameter) in exhaustively deionized suspensions of purely alcoholic organic solvents (methyl alcohol, ethyl alcohol, and ethylene glycol) and aqueous mixtures with alcohols (methyl, ethyl,n-propyl, andn-butyl alcohols and ethylene glycol). Sphere concentrations studied range from 0.001 to 0.01 in volume fraction, rather high compared with those in water. Induction periods are from 5 to 2000 s and are prolonged with decreasing sphere concentration. Nucleation rates are 10−3to 103mm−3s−1and increase sharply as sphere concentration increases. The crystal growth rates,vhave been determined from the increase of intensity in the sharpened reflection peaks. Values ofvrange from 1 to 27 μm/s and decrease linearly as the reciprocal sphere concentration increases. Nucleation and crystallization rates decrease sharply as the fraction of the organic solvents increases in the mixtures with water. The importance of the electrostatic intersphererepulsionthrough the electrical double layers and the cooperative and synchronized fluctuation of colloidal spheres in the crystallization processes is supported.