Phase Transition in Monodisperse Gold Sol. Microscopic Observation of Gas, Liquid and Solid States

摘要

A gold sol of narrow size distribution with particles 120 nm in aver- age diameter undergoes phase transition from gaseous (dispersed) state to solid (crystalline) state via liquid state when the concen- tration of the counterions in the medium is increased. The phe- nomenon takes place in a very thin layer of the settled sol, as ob- served with a microscope at 2000× magnification. The transition from the gaseous to the liquid state occurs at the ion concentration of ≈0.02 mol dm~-3 in a deposit of a number of small drops of a few mi- crometers in diameter. These 《drops》 start to crystallize at ≈0.03 mol dm~-3.