Ultrasound assisted method was used for synthesis of 3D hierarchical CuO microrods.
Ultrasound was found favoring oriented self-assembly of nanowires, forming 3D rods.
NO3− ions was found playing an important role on formation of 3D CuO rods.
The 3D CuO rod has strong light harvesting ability with a narrow band gap 1.54 eV.
The 3D CuO rod emits strong purple-blue light.