Application of Infrared Emission Spectroscopy to the Thermal Transition of Indium Hydroxide to Indium Oxide Nanocubes

Cubic indium hydroxide nanomaterials were obtained by a low-temperature soft-chemical method without any surfactants. The transition of nano-cubic indium hydroxide to cubic indium oxide during dehydroxylation has been studied by infrared emission spectroscopy. The spectra are related to the structure of the materials and the changes in the structure upon thermal treatment. The infrared absorption spectrum of In(OH)₃ is characterized by an intense OH deformation band at 1150 cm⁻¹ and two O–H stretching bands at 3107 and 3221 cm⁻¹. In the infrared emission spectra, the hydroxyl-stretching and hydroxyl-bending bands diminish dramatically upon heating, and no intensity remains after 200 °C. However, new low intensity bands are found in the OH deformation region at 915 cm⁻¹ and in the OH stretching region at 3437 cm⁻¹. These bands are attributed to the vibrations of newly formed InOH bonds because of the release and transfer of protons during calcination of the nanomaterial. The use of infrared emission spectroscopy enables the low-temperature phase transition brought about through dehydration of In(OH)₃ nanocubes to be studied.