Effects of Oxidizing Media on the Composition, Morphology and Optical Properties of Colloidal Zirconium Oxide Nanoparticles Synthesized via Pulsed Laser Ablation in Liquid Technique.

In this work, pulsed laser ablation in liquid (PLAL) technique was applied to synthesize colloidal nanoparticles of zirconium oxide (ZrO2) in three different aqueous media (de-ionized water, ethanol and acetone). The structure, morphology, composition and optical properties of the synthesized nanoparticles were characterized by XRD, SEM, TEM, XPS, UV-Vis spectrophotometer and FT-IR analysis respectively. The structural analysis by XRD reveals the formation of mixture of monoclinic and tetragonal phases of nanocrystalline zirconia. The average crystallite sizes of ZrO2 by using Scherrer's formula were estimated to be 41.8, 42.6 and 40.3 nm in water, ethanol and acetone respectively for monoclinic phase while 20.1, 24.8 and 18.9 nm were for tetragonal phase of ZrO2 in water, ethanol and acetone respectively. Microstructure of our starting materials was confirmed from SEM analysis and morphology of the synthesized nanostructured ZrO2 was studied by TEM. TEM images show that the average particle size is less than 10 nm with spherical shapes. The XPS analysis reveals the elemental compositions of ZrO2 nanoparticles and their stoichiometric ratios. Optical properties of the synthesized ZrO2 nanoparticles were studied by UV-Vis absorption spectroscopy and Fourier transform infrared spectroscopy (FT-IR). Uv-Vis absorption spectroscopy revealed that the nanoparticle produced in water has higher absorption due to higher NPs concentrations suspended in water. The band gap of the synthesized ZrO2 nanoparticles in water, ethanol and acetone were estimated from Tauc's plot to be 5.19, 5.22 and 4.94 eV respectively. FT-IR analysis also ascertained the functional groups of ZrO2 nanoparticles in the three liquid media.