Colloids in supercritical fluids over the last 20 years and future directions

In this work, the history of colloids in supercritical fluids in the last two decades and future directions in several promising areas are discussed. The primary focus of this article is on microemulsions and emulsions, although new developments are described involving protein colloids, electrostatic stabilization of inorganic particles and the use of CO2 as an antisolvent for separation of metal colloids. The focus on the CO2–water interface is related to the fact that, historically, the studies of colloids in supercritical fluids began with microemulsions and emulsions, and then evolved to polymer latexes and inorganic dispersions. Moreover, many of the same types of stabilizers have been used for the various types of colloids.