Hierarchically rosette-like In₂O₃ microspheres for volatile organic compounds gas sensors

Nanosheet-based three-dimensional (3D) hierarchical rosette-like In ₂O₃ microspheres and hollow microspheres are successfully prepared by a hydrothermal and subsequent annealing process. The formation mechanism of In(OH)₃(En)₂ microsphere precursors is investigated systematically, and the possible chemical reactions at each stage are proposed. The complexing agent and the surfactant are the two important factors to control the morphologies and microstructures of the final products. The as-synthesized hierarchical In₂O₃ microspheres show excellent sensing response to volatile organic compounds such as acetone and toluene gases. The detection limit can be as low as ∼500 ppb level in atmosphere. In addition, the sensing mechanism based on the change of surface resistance is discussed. Such novel In₂O₃ microspheres may be a promising candidate for sensor application in detecting acetone or toluene in different environments.