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ZnO-ZrO2 nanocomposites using zinc (II) acetylacetonate and different ZnO contents (13, 25, 50, and 75% mol) were synthesized through sol-gel method. The synthesis process was strongly related to nanocomposite properties especially on their structural composition. The obtained ZnO-ZrO2 nanomaterials presented tetragonal crystalline structure for zirconia whereas hexagonal one was formed in ZnO. Raman spectroscopy and XRD patterns confirmed the formation of tetragonal zirconia whereas inhibition of monoclinic structure was observed. Addition of ZnO affected the pore size distribution of the composite, and the measured specific surface areas were from 10 m2/g (for pure ZnO) to 46 m2/g (pristine ZrO2). Eg values of ZrO2 were modified by ZnO addition, since calculated values using Kubelka-Munk’s function varied from 4.73 to 3.76 eV. The morphology and size of the nanomaterials investigated by electron microscopy showed formation of nanorods for ZnO with sizes ranging from 50 nm to 300 nm while zirconia was formed by smaller particles (less than 50 nm). The main advantage of using the nanocomposite for photocatalytic degradation of phenol was the mineralization degree, since 75ZnO-ZrO2 nanocomposite surpassed mineralization reached by pure ZnO and also inhibited formation of undesirable intermediates.

In this work the characterization and determination of mercury in HClO 4 media using carbon paste electrodes modified with a-and b-cyclodextrins (CPE a-CD and CPE b-CD ) at E d ¼À 0.7 V with a t d ¼ 20 s and a potential scan v ¼ 20 mV s À1 is studied.. The statistical results obtained indicate that the modified electrodes displayed a better analytical performance as compared to that obtained with the unmodified CPE. The detection limits for the CPE a-CD and for the CPE b-CD were 0.05 and 0.09 mM, respectively, while for the CPE it was 0.41 mM. The CPE b-CD exhibited greater sensitivity as compared to that of the CPE a-CD .

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In this work, the effect of Pd addition on nanostructured TiO2 powders is studied. The materials were obtained by the sol-gel method and characterized by XRD, Rietveld refinement, TEM, Raman and UV-vis spectroscopies. The crystal structure and the nature of the different TiO2 phases were modified by varying the palladium/TiO2 ratio: 0.01, 0.03, and 0.05. The XRD results revealed the presence of different combinations of TiO2 (B), anatase, rutile and PdO phases as well as their coexistence in the different samples. The Rietveld analysis showed that the composition of the phases is rather affected by the amount of Pd added to the TiO2 structure. The Raman spectroscopy confirmed the characteristic bands of the TiO2 phases in the samples and their variation depending on the Pd/TiO2 ratio. The TEM results indicated that the as-prepared samples displayed crystal sizes of nanometric order (˂ 80nm). The observed reduction of the band gap was also correlated with the combination of phases due to the palladium addition. All the Pd/TiO2 samples showed a significant improvement in the elimination of 4-chlorophenol during the application of water treatment technology.

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