This thesis investigates and conveys the versatility and range of applications for Task-Specific Ionic Liquids (TSILs). A number of iron-based TSILs were prepared and their applications in the field of electrochemistry were studied using Cyclic Voltammetry (CV). Trihexyl(tetradecyl)phosphonium ferricyanide and trihexyl(tetradecyl)phosphonium ferrocyanide were prepared and characterised. Their rheological and electrochemical properties were investigated before the effectiveness of these TSILs in the phase separation of mixed aqueous-organic solvent solutions was briefly assessed. Given that ferro/ferricyanides are widely known to be effective in bioelectrochemistry as mediators for the oxidation of glucose by glucdse oxidase, the mediation ability of these . iron-based/phosphonium TSILs in this enzymatic reaction was stud)ed. The bioelectrochemical application of a ferrocene TSIL, 1-(ferrocenylhexyl)-3-methylimidazolium bis (trifluoromethanesulfonyl)imide, was also investigated. Successful mediation was confirmed and therefore, 1-(ferrocenylhexyl)-3-methylimidazolium bis(trifluoromethanesulfonyl)imide was studied further as a mediator in Dye Sensitised Solar Cells (DSSCs).