A method for the preparation of microvesicles useful as contrast agent in photoacoustic applications said method being characterised in that it comprises the steps of:- preparing a graphene water suspension, during which a water solution of graphene and of a first surfactant, which comprises an aromatic structure suited to interact with graphene and reactive functional groups suited to perform a cross-linking step, is subject to the action of ultrasounds- emulsion, during which at least one graphene suspension produced in the previous step, a low boiling point perfluorocarbon, a second surfactant, and a biodegradable polymer functionalised with reactive functional groups suited to cause a cross-linking reaction of the biodegradable polymer with the first surfactant present in the graphene suspension are added to and emulsified in water- cross-linking, during which the reactive functional groups present in the biodegradable polymer and in the first surfactant cause a cross-linking process with the formation of microvesicles which include the perfluorocarbon.
