Synthesis of Indium and Indium Oxide Nanoparticles from Indium Cyclopentadienyl Precursor and Their Application for Gas Sensing

摘要

Decomposition of the organometallic precursor [In(η~5-C_5H_5)] in toluene in the presence of methanol (8 vol. -%) at room temperature leads to the immediate formation of aggregates of indium nanoparticles of 15 ± 2 nm mean diameter. The aggregates are roughly spherical with a mean size of 400 ± 40 nm. The particles were characterized by means of transmission electron and high-resolution transmission electron microscopies (TEM and HRTEM) and X-ray diffraction (XRD) studies indicate that the powder consists of the tetragonal phase of indium. The thermal oxidation in air of these nanoparticles yields well-crystallized nanoparticles of In_2O_3 with unchanged morphology (aggregates of nanoparticles of 16.6 ± 2 nm mean diameter with aggregate mean size of 400 ± 40 nm) and without any sing of coalescence. XRD pattern shows that the powder consits of the cubic phase of In_2O_3. The electrical conductivity measurements demonstrate that this material is highly sensitive to an oxidizing gas such as nitrogen dioxide and barely sensitive to a reducing gas as carbon monoxide. Its association with SnO_2-based sensors allows the selective detection of carbon monoxide (30 ppm) and sub-ppm amounts of nitrogen dioxide (400 ppb) in a mixture at 20 ℃ and at a relative humidity of 60%.