TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The reducing agent comprises sodium borohydride or sodium hypochlorite. The photocatalyst comprises titanium oxide, zinc oxide, tantalum oxide or fullerene.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Components: The oil phase comprises at least a non-aqueous dispersion medium and metal nanoparticles dispersed in the dispersion medium, where the metal nanoparticles are those obtained by an amine reduction method and coated with a protecting agent having a linear or branched 10-20C alkyl group. The reducing agent comprises ascorbic acid, ascorbates, citric acid, citrates, malic acid or hydrazine. The concentration of the reducing agent in the water phase is 0.001-1 mol/l. The oil phase and/or the water phase comprise polymer compound, a water-soluble solvent or ethylene carbonate.    TECHNOLOGY FOCUS - POLYMERS - Preferred Method: In the method (M1), the heat treatment is conducted under a temperature of 40-100 degrees C. EXAMPLE - An electrically conductive emulsion ink was prepared as follows: silver acetate (10 g) was added to oleylamine (250 ml), and was heated and dissolved in that at 60 degrees C. Then, the mixture was heated at 200 degrees C for 30 minutes under stirring. The mixture was left to stand still at room temperature, and then methanol was added to the resulting silver nanoparticle dispersion, and the produced silver nanoparticles were precipitated by a centrifuge and collected. A procedure of dissolving the resulting silver nanoparticles again in hexane and precipitating them in ethanol was repeated for purification. The obtained silver nanoparticles (1.5 g), naphthenic non-aqueous medium (1.5 g) and HEXAGLYN 5-O (RTM: emulsifier) (0.2 g) were mixed together, and the mixture was treated with an ultrasonic dispersion machine to obtain an oil phase. The obtained oil phase was ultrasonically dispersed, and aqueous ascorbic acid solution (6.87 g) that was separately prepared was added to it to obtain an emulsion ink.