TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Method: In the method (M1), the reaction takes place under continuous conditions. The residence time is 2-10 seconds. The reactor tube comprises greater than or equal to 1 additional inlet downstream of the first inlet, and a cooling section between the inlet and the outlet. The suspension of the support material and/or the reactive solvent comprises a dispersion agent. The method (M1) further involves step of cooling the mixture of the solution of the precursor compound and the suspension of the support material in the reactor tube to liquefy the mixture. The reactive solvent has a temperature at or within 100 degrees C below, or above the temperature of the critical point (Tcr) of the reactive solvent and the reactive solvent is at a pressure at or within 30% below, or above the pressure of the critical point (Pcr) of the reactive solvent (preferably the reactive solvent has a temperature above the Tcr of the reactive solvent and the reactive solvent is at a pressure above Pcr of the reactive solvent). The ratio of the precursor compound to the support material is 1:100 to 100:1. The reactive solvent comprises a component to activate the support material. Preferred Components: The precursor compound is selected from H2PtCl6.6H2O, H2PtCl6.xH2O, PtCl2, PtCl4, PtO2, PtBr2, PtI2, platinum (IV) oxide hydrate (PtO2.xH2O), ammonium hexachloroplatinate(IV) ((NH4)2PtCl6), potassium hexachloroplatinate(IV) (K2PtCl6), RuCl3, ruthenium (III) chloride hydrate (RuCl3.xH2O), ruthenium iodide (RuI3), ruthenium (IV) oxide hydrate (RuO2.xH2O), ruthenium (III) bromide (RuBr3), and/or hexaamine ruthenium(II) chloride ((Ru(NH3)6)Cl2). The catalyst nanoparticles are metallic, such as a transition metal, a lanthanide, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Gd, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, Pt, Au, Ir, W, and/or Sr. The catalyst nanoparticles comprise a metal compound, where the metal compound comprises a metal atom and a partner atom, such as an atom from groups 13, 14, 15 or 16 of the periodic table of the elements, and/or a ligand molecule (preferably the metal is a transition metal or a lanthanide; especially the metal compound is selected from MgO, CoxOy, FexOy, Fe2O3/NiO, YxFeyOz, FeTiO3, CuFe2O4, ZnFe2O4, ZrFe2, CuZnFe4O4, Zr4Sc1Fe10, TiO2, CeO2, ZrO2, MoxSy, CoSx-MoS2, Fe1-xSx, and/or Ni(Co)Mo1-xWxS2) (where x, y and z are not defined). The partner atom is selected from boron (B), carbon (C), silicon (Si), germanium (Ge), nitrogen (N), phosphorus (P), arsenic (As), antimony (Sb), oxygen (O), sulfur (S), selenium (Se), tellurium (Te), and/or halogen. The specific surface area of the support material is greater than or equal to 10 m2/g (preferably greater than or equal to 100 m2/g). The support material is a carbon material, selected from graphene, reduced graphene oxide, graphene oxide, carbon nanotubes (CNT), carbon black or carbon aerogel; or is selected from aerogels, ceramic materials, metals, zeolites, tungsten carbide, metal oxides and metal sulfides. The component to activate the support material is H2O, H2O2, H2SO4, and/or HNO3. Preferred Catalyst: The catalytic structure formed by the method (M1) comprises platinum or platinum-ruthenium nanoparticles formed on a carbon support material.    TECHNOLOGY FOCUS - METALLURGY - Preferred Components: The support material is selected from metal alloys.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Components: The precursor compound is selected from cis-dichlorobis(pyridine)platinum(II), platinum(II) acetylacetonate (Pt(C5H7O2)2) (Pt(acac)2), dichloro(ethylenediamine)platinum(II) (H2NCH2CH2NH2)PtCl2), trans-platinum(II)diamine dichloride (Pt(NH3)2Cl2), and/or Ru(acac)3. The reactive solvent is a reducing solvent or an oxidizing solvent (preferably ethanol, methanol, isopropanol, and/or ethylene glycol). EXAMPLE - Synthesis of catalytic platinum nanoparticles directly onto KetjenBlack EC600jd (RTM: carbon black support) was carried out as follows. The synthesis was performed in supercritical regime with ethanol as reactive solvent. The platinum precursor comprising 357 mg H2PtCl6.6H2O was dissolved in 50 ml ethanol leading to solution of metal precursor. 135 mg Carbon support (for 50:50 Pt:C ratio) was dispersed in 50 ml mixture of ethanol and ethylene glycol (containing 1-25 vol.% ethylene glycol), and sonicated for 10 minutes to achieve good particle dispersion. The ethylene glycol improved carbon dispersion in solvent, while also acted as reducing agent. The metal precursor solution was pumped through reaction pump, whereas dispersed carbon support was pumped through reaction pump into pressurized system at 290-310 Bar. The solvent heater was kept at 450 degrees C while vertical heater was kept at 400 degrees C. At mixing point cold reactant streams mixed with super critical preheated solvent i.e. ethanol, leading to mixing temperature near or above supercritical temperature of ethanol, were easily adjusted by pump flow rates. The exact temperature was recorded. The rapid increase in temperature, lead to fast homogenous nucleation resulting in monodisperse nanoparticles. The continuous flow of produced nanoparticles on carbon support was withdrawn from system using pressure release valve, which also kept system pressurized. The synthesis products were characterized. The results when varying ethylene glycol content in carbon support solution, showed that good dispersion was observed at only 1 vol.% ethylene glycol, minimizing chance of pump-stop compared to 0% ethylene glycol. The powder X ray diffraction (PXRD) and electrochemical surface area (ECSA) showed most promising results of mean size of catalyst nanoparticles of 5 nm and ECSA (Hupd) of 65 m2/g.