Three-in-one: dispersant, emulsifier, and supporting electrolyte of hydrophobic ionic liquids for electrochemical collisions of single water droplets

We report the collisions of attoliter water-in-hydrophobic ionic liquid (IL) emulsion droplets as studied via an emulsion droplet reactor (EDR) on a carbon ultramicroelectrode (C-UME). The water-in-IL emulsion was prepared by the ultrasonic processing of a hydrophobic ionic liquid (1-decyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, [C10mim][NTf2]) and a potassium hydroxide solution containing guanine as the redox species. The ionic liquid is a three-in-one agent of dispersant, emulsifier, and supporting electrolyte. Under an appropriate potential, we observed the discrete collision behaviors of single emulsion droplets at the C-UME by chronoamperometry and obtained the current–time (i − t) curves of collisions. From the results of water-in-IL emulsion droplets collision, we discussed the collision frequency, size distribution, i − t decay behavior of emulsion droplets, and explored possible mechanisms. Furthermore, the effects of the aqueous phase supporting electrolyte and the viscosity of the ionic liquid on the collision behaviors of the emulsion droplets were investigated. Based on the results of single droplet collision, a water-in-IL emulsion collisional system was successfully established employing a hydrophobic ionic liquid without the addition of a hydrophobic supporting electrolyte.