Controlled synthesis of triangular and hexagonal Ni nanosheets and their size-dependent properties

Abstract

A solution phase method has been used to synthesize triangular and hexagonal Ni nanosheets with different edge lengths by controlling the reaction kinetics. This procedure is realized by introducing Fe(CO)5 into the reaction system to slow the formation rate of Ni(0). The introduced Fe(CO)5 exists as Fe(III) ions in the solution, which could oxidize Ni(0) back to Ni(II). By controlling the nucleation density, the sheet edge lengths could be changed from 19 nm to several hundreds of nanometres. The Ni nanosheets exhibit the transition from superparamagnetism to ferromagnetism with increasing sheet edge lengths. Their blocking temperature decreases with applied field and increasing sheet edge lengths. The Ni nanosheets also exhibit a surface plasmon resonance (SPR) feature, which is quite different from that of the Ni nanoparticles.