Monodisperse and 1D Cross-Linked Multi-branched Cu @ Ni Core–Shell Particles Synthesized by Chemical Reduction

We report on a two-step wet chemical route for producing Cu@Ni core–shell particles with multiple needle-like branches on the surface. Using the usual synthesis process, urchin-like Ni shells were formed on the surface of spherical Cu cores and monodisperse particles were obtained. Under the direction of a static magnetic field, one-dimensional, well-aligned Cu@Ni particles were assembled through cross-linking the branched Ni shells. The monodisperse Cu@Ni particles show stable and uniform field electron emission, having a low turn-on field of 3.3 V/μm and a large current density of 1 mA/cm² under an applied field of about 5.33 V/μm.