TECHNOLOGY FOCUS - CHEMICAL ENGINEERING - Preferred Method: In preparing the substrate surface structured with thermally stable metal alloy nanoparticles, the amphiphilic molecules are selected from compounds of the general formula R-X, and bifunctional compounds the general formula Y-R-X.For formula R-X; X=a polar or charged functional group, in particular COOH, OH, SH, NHR' (R' being alkyl), NH2, PHR' (R' being alkyl), PH2, PO, SO2H, SO3H, SO4H and salts; andR=a straight other branched carbon chain with 5 or more C atoms, e.g. sodium dodecyl sulfate (SDS), trioctylphosphinoxide (TOPO), cetyltrimethylammoniumbromide (CTAB), and tetradecyl-trimethyl ammoniumbromide (TTAB).For formula Y-R-X; X and Y=are different, being a polar or charged functional group, in particular COOH, OH, SH, NHR' (R' being alkyl), NH2, PHR' (R' being alkyl), PH2, PO, SO2, SO3H, SO4H and salts; andR=a straight other branched carbon chain with 5 or more C atoms, dendrimers, in particular hydroxyl- and/or thiol- functionalized fourth generation polyamidodamine dendrimers (G4-PAMAM), organic diblock or multiblock copolymers, thiolated oligonucleotides and polyethylene glycols.The amphiphilic molecules are organic diblock or multiblock copolymers and the method comprises providing a micellar solution of an organic diblock or multiblock copolymer in a suitable solvent; loading the micelles of the micellar solution with metal ions of a first metal salt; loading the micelles of the micellar solution with metal ions of at least one second metal salt; depositing the metal ion-loaded micellar solution onto a substrate surface to form a polymer film comprising an ordered array of polymer domains; co-reducing the metal ions contained in the deposited domains of the polymer film by way of a plasma treatment to form an ordered array of nanoparticles consisting of an alloy of the metals used for loading the micelles on the substrate surface. The first metal is a noble metal, preferably gold (Au) or rhodium (Rh), or nickel (Ni), and the second metal is selected from noble metals, in particular platinum (Pt), palladium (Pd), Rh, preferably Pt, and transition metals, in particular Ni. The molar ratio of the first metal to the second metal is in the range of 9:1 to 1:9, preferably in the range of 8:2 to 2:8. The diblock or multiblock copolymer is selected from polystyrene-b-polyethylenoxide, polystyrene-b-poly (2-vinylpyridine), polystyrene-b-poly (4-vinyl- pyridine) or mixtures. The plasma treatment is effected for a time period of at least 60 minutes, preferably at least 90 minutes. The co-reduction of the metal ions is effected by way of a gas plasma comprising hydrogen. The gas plasma is selected from pure hydrogen and a mixture of hydrogen/inert gas, in particular hydrogen/noble gas, such as hydrogen/argon, or hydrogen/nitrogen. The nanoparticles are thermally stable up to a temperature at least 450 degrees C, preferably at least 700-750 degrees C. The substrate surface is selected from silicon (Si), Si coated with a native oxide layer, silicon dioxide (SiO2), glass, titanium dioxide (TiO2), zinc oxide (ZnO), alumina, silica/alumina, carbon and carbon-based materials. In nanostructuring the substrate surface which is the bead or particle, in step (a) the micelles are loaded with a salt of a first metal and a salt of at least one second metal different from the first metal and step (c) comprises a co-reduction of the different metal ions to form alloy nanoparticles. In the alloy nanoparticles the first metal is a noble metal, preferably Au or Rh, or Ni, and at least one second metal is selected from the group comprising noble metals, in particular Pt, Pd, Rh, preferably Pt, and transition metals in particular Ni. The alloy nanoparticles are Au/Pt nanoparticles, Rh/Pt nanoparticles or Ni/Pt nanoparticles. Preferred Surface: In the substrate surface, the metal alloy is an alloy of Au and Pt, in particular Au80Pt20 and/or Au20Pt80, an alloy of Rh and Pt, or an alloy of Ni and Pt. The substrate surface is a bead or particle having a diameter in the micrometer range, mesoporous material comprising particles or aggregates of particles, or a fibrous material, such as a mesh of fibers. The mesoporous material comprises silica, alumina or silica/alumina. In using the substrate surface, the catalyst is a catalyst for treating/decontaminating car exhaust emissions or a catalyst for fuel cells. EXAMPLE - No suitable example given.