In a method for preparing copper salts from at least one cupriferous and one additional reactant, the reactants are used to prepare micro-emulsions while employing at least one block polymer, the intermediate products obtained this way are mixed and reacted together so as to form a micro-emulsion. The preparation of the starting micro-emulsion as well as the subsequent joint reaction preferably occur either with ultrasound or in a high-pressure homogenizer. The copper salts obtained this way exhibit a particle size of less than 50 nm, preferably 5 to 20 nm and can be adjusted to specific applications through the appropriate doping of foreign ions.