Synthesis and characterization of ultra-long and pencil-like copper nanowires with a penta-twinned structure by hydrothermal method

•Ultra-long copper nanowires have been prepared in a rich production using a simple hydrothermal method.•Pencil-like copper nanowire with a penta-twinned structure was firstly discovered by changing the amount of glucose.•Pencil-like nanowires experienced growth along both radial and axial directions.

Ultra-long copper nanowires with uniform diameters of 45 nm and good dispersity were successfully synthesized in a rich production by a simple hydrothermal method using green raw materials. High resolution transmission electron microscope (HRTEM) and selected area electron diffraction (SAED) results indicate that the ultra-long copper NWs are twinned crystals growing along [1 1 0] direction. A novel morphology of pencil-like nanowires with a penta-twinned structure emerged when reducing the amount of glucose. Results showed that the formation mechanism of pencil-like nanowires is that one dimension (1D) elongation of copper NWs with a five-twinned structure confined by hexadecylamine (HDA) is accompanied by the growth along the radial orientation in the same time.