Nearly monodispersed In(OH)3 hierarchical nanospheres and nanocubes: tunable ligand-assisted synthesis and their conversion into hierarchical In2O3 for gas sensing

Abstract

In(OH)₃ nanomaterials with different morphologies or hierarchical structures, such as nanoparticles, monodispersed hierarchical nanocubes and nanospheres, have been successfully synthesized via a ligand-assisted aqueous process. The shape and size of these as-prepared architectures can be tuned effectively by controlling the reaction conditions, such as the molar ratio of ligand/In³⁺ and different ligands. Further studies reveal that both Na₃cit and urea are necessary for the formation of monodispersed hierarchical nanospheres and nanocubes. Furthermore, In₂O₃ nanoparticles and monodispersed hierarchical nanocubes and nanospheres with well-defined morphologies of the precursors can be also obtained by annealing the corresponding In(OH)₃ samples. The gas sensing properties of the as-prepared In₂O₃ samples demonstrate that hierarchical In₂O₃ architectures exhibit a superior response to ethanol gas, and the hierarchical In₂O₃ nanocubes have excellent selectivity and sensitivity. Further more, XPS spectra and N₂ adsorption–desorption isotherms achieve a deeper understanding of the effects of the final product morphologies on their gas sensing properties.