Nearly monodispersed In(OH) ₃ hierarchical nanospheres and nanocubes: tunable ligand-assisted synthesis and their conversion into hierarchical In ₂ O ₃ for gas sensing

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.