TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Method: In one step, the precursor substance solution undergoes the reduction reaction using the reducing agent solution and homogeneous nanoparticles are obtained. The method involves at least two steps, in which the precursor substance solution undergoes the reduction reaction using the reducing agent solution and layered nanoparticles of core-shell type are obtained. The pH of the neutralizing substance solution is adjusted by addition of a buffer, acid or base. The reduction reaction is carried out at 0-100 degrees C, preferably 40 degrees C. The particular tubing segments of the continuous flow system, through which the stream of the reagents, the reaction mixture and products flows in the flow system, are either thermostated or maintained at the room temperature. The particular tubing segments of the continuous flow system, through which the stream of the reagents, the reaction mixture and products flows are maintained at different temperatures. After the substance neutralizing the reducing agent is supplied to the system, the stream of products is cooled down. The stream of products is cooled down to room temperature. The method is carried out in the aqueous environment. The inner diameter of the tubes in the continuous flow system of 2'' to 1/64'', preferably 1/8'' to 1/32''. The length of tubes, in which the reduction reaction takes place, is 1 cm to 5 m, preferably 40-60 cm. The reagent flow rate in the continuous flow system is 1 ml/hour to 100 l/hour, preferably 200 ml/hour to 3200 ml/hour. The length of the tubes, in which the reduction reaction takes place, and the reagent flow rate in the continuous flow system are selected in such a manner, so that the reduction reaction time ranges from 0.01 second to 1 hour. In the first step, the solution of the precursor substance Cu(NO3)2 undergoes the reduction reaction using hydrazine solution, which results in formation of the copper core, and in the second step to the reaction mixture the solution of the precursor substance Pd(NO3)2 is supplied, whose reduction results in formation of the palladium shells on the copper nanoparticles formed in the first step, and the reduction is terminated by addition of hydrogen peroxide solution and a base, where the base concentration is sufficient to ensure neutral pH of the product stream. The reduction results in formation of homogenous nanoparticles of Pd/Pt alloy. The method additionally involves colloid nanoparticle centrifugation and/or drying step, where nanoparticle powder is obtained. Preferred Components: The precursor substance is metal precursor or its mixture (preferably metal salt or its mixture, especially salts of palladium, silver, gold, platinum, ruthenium, osmium, iridium, rhodium, nickel, cobalt, copper and iron, particularly AgNO3, AgClO4, AgHSO4, Ag2SO4, AgF, AgBF4, AgPF6, CH3COOAg, AgCF3SO3, CuCl2, Cu(NO3)2, CuSO4, Cu(HSO4)2, Cu(Cl04)2, CuF2, (CHCOO)2Cu, H2PtCl6, H6Cl2N2Pt, PtCl2, PtBr2, K2(PtCl4), Na2(PtCl4), Li2(PtCl4), H2Pt(OH)6, Pt(NO3)2, (Pt(NH3)4)Cl2, (Pt(NH3)4)(HCO3)2, (Pt(NH3)4)(OAc)2, (NH4)2PtBr6, K2PtCl6, PtSO4, Pt(HSO4)2, Pt(ClO4)2, H2PdCl6, H6Cl2N2Pd, PdCl2, PdBr2, K2(PdCl4), Na2(PdCl4), Li2(PdCl4), H2Pd(OH)6, Pd(NO3)2, (Pd(NH3)4)Cl2, (Pd(NH3)4)(HCO3)2, (Pd(NH3)4)(OAc)2, (NH4)2PdBr6, (NH3)2PdCl6, PdSO4, Pd(HSO4)2, Pd(ClO4)2, HAuCl4, AuCl3, AuCl, AuF3, (CH3)2SAuCl, AuF, AuCl(SC4H8), AuBr, AuBr3, Na3Au(S2O3)2, HAuBr4, K(Au(CN)2), CoF2, Co(NO3)2, CoCl2, CoSO4, Co(HSO4)2, Co(ClO4)2, (CHCOO)2Co, CoBr2, (Co(NH3)6)Cl3, (CoCl(NH3)5)Cl2, (Co(NO2)(NH3)5)Cl2, NiF2, Ni(NO3)2, NiCl2, NiSO4, Ni(HSO4)2, Ni(ClO4)2, (CHCOO)2Ni, NiBr2, Ni(OH)HSO4, Ni(OH)Cl, FeF2, Fe(NO3)2, FeCl2, FeSO4, Fe(HSO4)2, Fe(ClO4)2, (CHCOO)2Fe, FeBr2, FeF3, Fe(NO3)3, FeCl3, Fe2(SO4)3, Fe(HSO4)3, Fe(ClO4)3, (CHCOO)3Fe, FeBr3, RuCl2((CH3)2SO)4, RuCl3, (Ru(NH3)5(N2))Cl2, Ru(NO3)3, RuBr3, RuF3, Ru(ClO4)3, OsI, OsI2, OsBr3 , OsCl4, OsF5, OsF6, OsOF5, OsF7, IrF6, IrCl3, IrF4, IrF5, Ir(ClO4)3, K3(IrCl6), K2(IrCl6), Na3(IrCl6), Na2(IrCl6), Li3(IrCl6), Li2(IrCl6), (Ir(NH3)4Cl2)Cl, RhF3, RhF4, RhCl3, (Rh(NH3)5Cl)Cl2, RhCl(P(C6H5)3)3, K(Rh(CO)2Cl2), Na(Rh(CO)2Cl2), Li(Rh(CO)2Cl2), Rh2(SO4)3, Rh(HSO4)3, Rh(ClO4)3, and their salts and/or hydrates, more particularly Pd(NO3)2 and/or Cu(NO3)2). A concentration of the precursor substance solution is 1 mM to 1 M, preferably 10 mM. The reducing agent is selected from hydrazine, ascorbic acid, sodium borohydride, sodium hypophosphite, lithium tetraethylborohydride, methanol, 1,2-hexadecanediol, hydroxylamine and dimethylborazane DMAB (preferably hydrazine). A concentration of the reducing agent solution is 0.5 mM to 4 M, preferably 20 mM. The substance neutralizing the reducing agent is hydrogen peroxide, oxygen, ozone, NO2 or redox buffer (preferably hydrogen peroxide). The substance neutralizing the reducing agent is supplied to the system in the form of a solution. The solution of the substance neutralizing the reducing agent is the hydrogen peroxide solution. A concentration of the solution of substance neutralizing the reducing agent is 0.1 mM to 10 M, preferably 35 mM. The solution of the substance neutralizing the reducing agent additionally comprises 2.69 mm NaOH. EXAMPLE - Reduction reaction was carried out in continuous flow system in Teflon (RTM: polytetrafluoroethylene) tube having inner diameter of 1/32'' and length of 40 cm, where flow rate of the reagents in the reaction tube is 200 ml/hour. Aqueous solution of 10 mM Cu(NO3)2 was used to obtain stable colloid of copper (I) oxide nanoparticles. 20 mM aqueous solution of hydrazine was used as reducing agent. The reaction was carried out at 40 degrees C, and 3.79 mM solution of hydrogen peroxide with addition of 2.69 mM NaOH (pH=12) was used to terminate the reaction. The obtained colloid solution had pH of 7. A stable orange-yellow colloid of copper (I) oxide nanoparticles was obtained, which was stable for 2 weeks (or even longer) without a need for mixing and/or sonication in the ultrasonic bath.