Composite nanoparticles and manufacturing method thereof

A method for manufacturing composite nanoparticles, comprising a step of obtaining composite nanoparticles containing at least silver and copper in a single particle by

• heat treating a mixture containing an organic silver compound and an organic copper compound at a temperature of 150° C. or more in a non-oxidative atmosphere in the presence of:
• a tertiary amine compound represented by the general formula R1R2R3N, wherein R1 to R3 independently represent an alkyl group or aryl group that may have a substituent, R1 to R3 may be linked together to form a cyclic structure, and the number of carbon atoms in each of R1 to R3 is 1 through 18 and may be the same or different, and
• a 1,2-alkanediol having 10 or more carbon atoms and/or a derivative thereof,
• wherein the X-ray diffraction pattern of the composite nanoparticles shows peaks of silver and peaks of copper.