engleski

Tailoring the morphology of lanthanum hydroxide nanostructures

Nonaqueous sol-gel routes provide a versatile tool to control morphology, crystallinity, stoichiometry and homogeneity of metal oxide nanoparticles [1, 2]. Investigations in the lanthanum-manganese-oxide system resulted in surprising results with respect to product composition and morphology. Starting from La(OiPr)3 and KMnO4 with different molar ratios in organic solvents like benzyl alcohol, 2-butanone and mixtures thereof, La(OH)3 nanostructures with different particle shapes ranging from nanospheres to nanorods and nanobelts were formed. We found that KMnO4 plays a crucial role in determining the particle morphology of La(OH)3. All the samples were investigated by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), combined high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED) and energy dispersive X-ray (EDX) analysis. Fourier transform infrared spectroscopy (FTIR) was used in order to investigate the organic-inorganic impurities attached to La(OH)3 as well as to evidence the presence of OH groups. The quantity of organic impurities is estimated using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Finally, the analysis with 1H and 13C nuclear magnetic resonance (NMR) was performed in order to elucidate possible reaction mechanisms. Since the morphology, phase purity and microstructure of the synthesized La(OH)3 nanostructures are strongly dependent on the synthesis conditions, it is possible to tailor these properties by adjusting the molar La(OiPr)3-to-KMnO4 as well as the benzyl alcohol-to-2-butanone ratio.

Nonaqueous sol-gel; Morphology; Microstructure

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