Ultrafine particles of metallic single-crystalline copper were rarely reported before.

The ultrafine particles of metallic single-crystalline copper were synthesized here.

The octahedral single-crystalline copper with an average size of 776 nm were prepared.

The spherical single-crystalline copper with an average size of 92 nm were synthesized.

The ratio of NaCl to raw copper in the materials affected the particle shape and size.