A formulation containing particulate matter including nanometric metallic copper particles, at least 10% of the particulate matter being single-crystal metallic copper particles, the particulate matter having an average secondary particle size (d50) within a range of 20 to 200 nanometers, the nanometric metallic copper particles being at least partially covered by at least one dispersant; a concentration ratio of crystalline cuprous oxide particles to the nanometric metallic copper particles, within the particulate matter, being at most 0.4; the formulation including a solvent, the particulate matter and the solvent forming a dispersion.