Synthesis and Characterisation of Polyol-Capped Transition Metal Oxide Nanoparticles

In-situ capped nanocrystalline -Fe₂O₃, Co₃O₄, and Cu₂O were prepared in 1,4-butanediol in aerobic conditions. X-ray diffraction (XRD)patterns show that the synthesised samples are nanocrystalline cubic oxides with crystallitesizes 9.5 nm, 13.4 nm, and 11 nm, respectively. Raman spectroscopy shows peaks at 350 cm⁻¹, 500 cm⁻¹, and 700 cm⁻¹, indicating that the iron oxide is-Fe₂O₃; Mössbauer spectroscopy shows the presence of twoFe³⁺ sites. Transmission electron microscopy images show that the particle sizes of -Fe₂O₃ and Co₃O₄ samples are 8.9 nm and 7 nm, respectively. The absence of agglomeration indicates that the synthesised nanoparticles are capped.FT-IR spectra show the presence of an organic moiety in the sample which acts as a capping agent. Thermogravimetry showsthat the capping is stable up to 873 K in -Fe₂O₃, and up to 400 K in Co₃O₄. The samples are soluble in water to form stablehydrosols. During synthesis of -Fe₂O₃ a 6-line ferrihydrite is formed as an intermediate, which is stable in solution up to 473 K, and transforms to -Fe₂O₃ at 483 K, by rapid dissolution-reprecipitation. In the syntheses of Co₃O₄andCu₂O, no intermediates are formed.