A method for the preparation of nanoparticles selected from the group consisting of metal nanoparticles, metal oxide nanoparticles and semiconductor nanoparticles, wherein said method is implemented in a device comprising: - at least one reacting chamber including at least one first inlet for admission of said liquid phase in said reacting chamber, at least one second inlet for admission of said gas phase in said reacting chamber, and an outlet for expulsion of said nanoparticles from said reacting chamber, - a liquid injector arranged upstream of the first inlet for injecting or spraying said liquid phase into said reacting chamber, - an injector of nanoparticles arranged downstream of the outlet for injecting or spraying said nanoparticles through an outlet of said nanoparticles injector, and - control means for controlling the injection or the spray of said liquid phase and/or said nanoparticles, and wherein said method comprises: - a step 1) of injecting a liquid phase comprising at least one nanoparticles precursor selected from the group consisting of precursors of metals, precursors of metal oxides and precursors of semiconductors in said reacting chamber through said liquid injector, - a step 2) of contacting said liquid phase with a gas phase comprising at least one carrier gas and at least one reacting gas, said step 2) being carried out in said reacting chamber, - a step 3) of reacting the nanoparticles precursor with the reacting gas so as to form nanoparticles, and - a step 4) of expulsion of the nanoparticles produced in step 3) from the reacting chamber through the nanoparticles injector, said nanoparticles being under the form of an aerosol at the outlet of the nanoparticles injector. wherein said method is implemented in a device comprising: - at least one reacting chamber including at least one first inlet for admission of said liquid phase in said reacting chamber, at least one second inlet for admission of said gas phase in said reacting chamber, and an outlet for expulsion of said nanoparticles from said reacting chamber, - a liquid injector arranged upstream of the first inlet for injecting or spraying said liquid phase into said reacting chamber, - an injector of nanoparticles arranged downstream of the outlet for injecting or spraying said nanoparticles through an outlet of said nanoparticles injector, and - control means for controlling the injection or the spray of said liquid phase and/or said nanoparticles, - at least one reacting chamber including at least one first inlet for admission of said liquid phase in said reacting chamber, at least one second inlet for admission of said gas phase in said reacting chamber, and an outlet for expulsion of said nanoparticles from said reacting chamber, - a liquid injector arranged upstream of the first inlet for injecting or spraying said liquid phase into said reacting chamber, - an injector of nanoparticles arranged downstream of the outlet for injecting or spraying said nanoparticles through an outlet of said nanoparticles injector, and - control means for controlling the injection or the spray of said liquid phase and/or said nanoparticles, and wherein said method comprises: - a step 1) of injecting a liquid phase comprising at least one nanoparticles precursor selected from the group consisting of precursors of metals, precursors of metal oxides and precursors of semiconductors in said reacting chamber through said liquid injector, - a step 2) of contacting said liquid phase with a gas phase comprising at least one carrier gas and at least one reacting gas, said step 2) being carried out in said reacting chamber, - a step 3) of reacting the nanoparticles precursor with the reacting gas so as to form nanoparticles, and - a step 4) of expulsion of the nanoparticles produced in step 3) from the reacting chamber through the nanoparticles injector, said nanoparticles being under the form of an aerosol at the outlet of the nanoparticles injector. - a step 1) of injecting a liquid phase comprising at least one nanoparticles precursor selected from the group consisting of precursors of metals, precursors of metal oxides and precursors of semiconductors in said reacting chamber through said liquid injector, - a step 2) of contacting said liquid phase with a gas phase comprising at least one carrier gas and at least one reacting gas, said step 2) being carried out in said reacting chamber, - a step 3) of reacting the nanoparticles precursor with the reacting gas so as to form nanoparticles, and - a step 4) of expulsion of the nanoparticles produced in step 3) from the reacting chamber through the nanoparticles injector, said nanoparticles being under the form of an aerosol at the outlet of the nanoparticles injector.