Studies on formation mechanism of 3D Cu2O nanospheres through self-assembly of 0D nanodots

Abstract

Cu2O crystals with different morphologies (solid and porous) and sizes (from 25 to 282nm) were synthesized controllably through a facile solvothermal route. The growth mechanism was investigated by SEM and TEM with varying the concentration of poly (vinylpyrrolidone) (PVP, K30), CH3COO− (Ac−) and NO3− acid ions in the precursor solution. The self-assembly of three types of Cu2O nano-structures was observed through a general route of zero-dimensional (0D)→2D→3D. When Cu(Ac)2⋅H2O was used as the copper sources, 0D Cu2O nanodots with size of 2–7nm were firstly assembled to 2D quasi-spherical and bookmark-like structures via Oriented attachment (OA), and then converted into 3D hierarchical Cu2O nanoclusters (a few tens of nm) and porous sub-microspheres with an average size of 282nm, respectively. While Cu(NO3)2⋅3H2O was used instead of Cu(Ac)2⋅H2O, the similar assembly process occurred leading to the formation of Cu2O porous nanospheres of 40–140nm which exhibit better adsorption ability toward methyl orange compared with activated carbon. In addition, we also investigated the dependence of Cu2O crystals on the concentration of acid ions (Ac− and NO3−). Compared with Ac−, the size and morphology of the obtained products were less dependent on the concentration of NO3− acid ions. This study might provide a new insight into the growth mechanism of Cu2O based micro- or nanostructures.