Self-assembly of single-crystalline α-Fe2O3 nanoplates into columnar superstructures: controllable synthesis, growth mechanism, and properties

Abstract

Self-assembly of crystalline α-Fe₂O₃ nanoplates into columnar one dimensional superstructures (CODS) was achieved in high yield by a simple hydrothermal route in the presence of glycerin. The α-Fe₂O₃ micro-/nanocrystals with controllable sizes and morphologies, such as nanospheres, nanoparticles, polyhedrons and plates, were also synthesized by this facile process. Contrast experiments indicated that the glycerin not only acted as a structure-directing agent for controlling growth of α-Fe₂O₃ plates but also played a role in assembling α-Fe₂O₃ individual plates into columnar superstructures. Based on the time-dependent experiments, a reasonable growth mechanism of α-Fe₂O₃ CODS has been proposed. The obtained α-Fe₂O₃ crystals displayed ferromagnetic behavior and their magnetic properties were dependent on their sizes and shapes. Furthermore, the coercivity values of the α-Fe₂O₃ single microplates (~2.5 μm in diameter) and CODS (~2.2 μm in length) were high up to 1872.6 Oe and 889.7 Oe, respectively. In addition, gas sensors based on plate-like α-Fe₂O₃ and their CODS exhibited high sensitivity for ethanol and formaldehyde, respectively.