NOVELTY - The article comprises a matrix material, copper nanoparticles (10-99.9%) that are provided in the matrix material and partially fused together by applying heat or pressure to the article, and a filler material. A size of the copper nanoparticles is 1-5 nm. The copper nanoparticles comprise a surfactant system, and a thermally conductive percolation pathway in the matrix material. The article is heated at a temperature of 100 degrees C to partially fuse the copper nanoparticles together. The filler material consists of flame retardants, UV protective agents, antioxidants and graphite.    USE - The article including copper nanoparticles is useful in heat transfer applications, microelectromechanical and nanoelecttromechanical devices, biomaterials, biomarkers, diagnostic imaging devices, sensors, coatings, composite materials, textiles, fuel cells, solar cells and antimicrobial and antifungal compositions.    ADVANTAGE - The article including copper nanoparticles exhibits prolonged lifespan, improved stability against oxidation and excellent optical and electrical properties.    DETAILED DESCRIPTION - The article comprises a matrix material, copper nanoparticles (10-99.9%) that are provided in the matrix material and partially fused together by applying heat or pressure to the article, and a filler material. A size of the copper nanoparticles is 1-5 nm. The copper nanoparticles comprise a surfactant system, and a thermally conductive percolation pathway in the matrix material. The article is heated at a temperature of 100 degrees C to partially fuse the copper nanoparticles together. The filler material consists of flame retardants, UV protective agents, antioxidants, graphite, graphite oxide, graphene, carbon nanotubes, fiber materials and/or ceramic materials. The article has a thermal conductivity of 50-400 watts/m-K. The matrix material consists of a polymer matrix, a rubber matrix, a glass matrix, a ceramic matrix and a metal matrix. INDEPENDENT CLAIMS are included for:    (1) a method for producing an article; and    (2) a composition.    DESCRIPTION OF DRAWING(S) - The diagram shows a scanning electron microscope image of copper nanoparticles.