A Shape-Controlled Method to Functionalize Multiwalled Carbon Nanotubes with Ni₃S₂

In this paper, we report the funtionalization of multiwalled carbon nanotubes (MWCNTs) with Ni₃S₂ using a solvent−thermal approach. The nanocomposites synthesized without ammonia show that the MWCNTs' outer surface was uniformly coated with a Ni₃S₂ film appearing like centipede-shaped objects when characterized by scanning transmission electron microscopy and transmission electron microscopy images. Meanwhile, the Ni₃S₂ layer thickness can be changed by simply altering the concentration of reaction precursors and keeping the other reaction conditions constant. Interestingly, clustered Ni₃S₂ nanoparticles were formed along the outside surfaces of the MWCNTs when ammonia was added to the reaction solution while keeping all other conditions unchanged. Also, the sizes of Ni₃S₂ nanoparticles can be varied through varying the amount of ammonia in our reaction system. On the basis of our experimental results, we propose a dynamic-controlled Oswald ripening mechanism to elucidate the formation of the MWCNTs composites with centipede-shaped and clustered Ni₃S₂ morphologies.