2017 Volume 64 Issue 12 Pages 667-672
Conductive inks that are composed mainly of metal nanoparticles are used as core materials for printed electronics. We developed a production method of new copper complex solutions, which by reductive heating yielded copper nanoparticles dispersion liquids of less than 100 nm in particle diameter. The copper complex solutions are grouped into three classes according to the ratio of two absorbance maxima in their extinction spectra, which determines the average particle diameter of the product copper nanoparticles. We found that Class II copper complex solution contains ultrafine copper nanoparticles of only ~1 nm in diameter as secondary species. They serve as effective nuclei allowing a size-controlled copper nanoparticle growth from the copper complex solution, thereby limiting the average size of the product copper nanoparticles to ~20 nm.
