Synthesis and formation mechanism of self-assembled 3D flower-like Bi/γ-Fe2O3 composite particles

Composites with hierarchical structures have wide potential applications in the catalyst industry. In this paper, a self-assembled 3D flower-like architecture of the Bi/γ-Fe2O3 composite has been successfully synthesized without employing any surfactants and templates via a facile and economical hydrothermal method. Its formation process has been studied. X-ray diffraction (XRD), X-ray absorption fine structure (XAFS), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), and Raman spectroscopy techniques were used to monitor the formation process. The results demonstrate that the self-assembled 3D flower-like Bi/γ-Fe2O3 composite consists of a Bi metal nucleus and a γ-Fe2O3 shell. The Bi metal nucleus is identified to be an aggregate of Bi nanoparticles, while the γ-Fe2O3 shell results from the intercrossing of γ-Fe2O3 nanoslices. The time-dependent intermediate products in the self-assembly process were structurally characterized. The influence of concentration and the formation process have been carefully discussed. A possible formation mechanism has been proposed. By virtue of the structural understanding of the novel 3D flower-like Bi/γ-Fe2O3 composite, this work is expected to highlight its potential applications.