Method of preparing carrier liquids

A method for the preparation of a carrier liquid which comprises the steps of:

• (I) preparing a single phase solution comprising:
• a) a solvent or a mixture of miscible solvents,
• b) a liquid carrier material, which is soluble in solvent (a), and
• c) a dopant material which is also soluble in solvent (a), wherein the solvent or the mixture of miscible solvents (a) is relatively more volatile than the liquid carrier material (b) and the dopant material (c),
• (II) cooling the single phase solution produced in step (I) to a temperature at which at least both the solvent (a) and carrier material (b) become solid, and
• (III) removing solid solvent (a) from the cooled single phase solution in vapour form, such that the remaining cooled carrier material (b) and dopant material (c) are returned to ambient temperature thus providing a product of liquid carrier material (b) having dopant material (c) dispersed therein.