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The difference between the surface and the bulk shell of [Ce.sub.x][Pr.sub.1-x][O.sub.2-delta] mixed oxides is studied by Raman spectroscopy with four different excitation lasers. The results have shown that the surface region and the bulk shell are different and the thickness of the surface layer with rich Pr increases with the decrease in the Ce content.

In this work, we demonstrate the capability of controllingthe crystallographic orientation of ZnO nanostructure arrays grownalong nonpolar [11̅00] orientation. The Au catalyst was usedto initiate and guide the growth of ZnO nanostructures on (100) γ-LiAlO2substrate. The morphology, structure, and optical propertiesof the as-synthesized ZnO nanostructures were characterized by fieldemission scanning electron microscopy, X-ray diffraction, field emissiontransmission electron microscope, monochromatic cathodoluminescenceimage, and photoluminescence spectroscopy. The ZnO nanostructure arraysexhibited special shape and were aligned vertically on the (100) γ-LiAlO2substrate. A cooperative of Au-catalyzed VLS vertebral columngrowth along [11̅00] orientation, zinc-self-catalyzed VLS growthalong [0001], and ZnO VS lateral expansion growth process was proposedfor the special ZnO nanostructures. [ABSTRACT FROM AUTHOR]

Arsenic (As) contaminated soils and waters are becoming major global environmental and human health risks. The identification of natural hyperaccumulators of As opens the door for phytoremediation of the arsenic contaminant. Pteris vittata is the first identified naturally evolving As hyperaccumulator. More than a decade after its discovery, we have made great progress in understanding the uptake, transport, and detoxification of As in the fern. The molecular mechanisms controlling As accumulation in P. vittata are now beginning to be recognized. In this review, we will try to summarize what we have learned about this As accumulator, with particular emphasis on the current knowledge of the physiological and molecular mechanisms of arsenic phytoremediation. We also discuss the potential strategies to further enhance phytoextraction abilities of P. vittata. [ABSTRACT FROM AUTHOR]

Safe incineration of harvested hyperaccumulators containing high content of heavy metals to avoid secondary environmental pollution is a problem for popularizing phytoremediation technology. The As volatilization behavior and its mechanism during incineration of Pteris vittata, an As-hyperaccumulator, was investigated. Incineration results reveal that 24% of total As accumulated by P. vittata (H-As) containing high As content (1170 mg/kg) is emitted at 800 °C, of which 62.5% of the total emitted As is volatilized below 400 °C. A study of the extended X-ray absorption fine structure (EXAFS) shows that part of As(III) was identified in the thermal decomposition residue of dried P. vittata (H-As), As2O5 + P. vittata (L-As) containing low As content (14.7 mg/kg), and As2O5 + charcoal (C) at 200 °C, suggesting that carbon originating from biomass incineration might catalyze As(V) reduction. This speculation was tested through thermogravimetric experiments, in which either C or P. vittata (L-As) markedly catalyzed the volatilization of pure As2O5 at low temperature. Therefore, the reduction of As(V) to As(III) is responsible for As volatilization during incineration of P. vittata below 400 °C. This study provides important insights into As behavior during incineration of As-hyperaccumulators, which is helpful to safely dispose harvested biomass with high As content. [ABSTRACT FROM AUTHOR]

The difference between the surface and the bulk shell of CexPr1-xO2-mixed oxides was studied by Raman spectroscopy with four different excitation lasers. Two Raman peaks appear at 465 and 570 cm-1under all of the four lasers. The former is attributed to the Raman active F2gmode of CeO2, while the latter is attributed to oxygen vacancy. On the basis of the fact that the laser with shorter wavelength is closer to the electronic adsorption of samples, it is found that the Raman information detected by excitation laser with shorter wavelength is more sensitive to the surface region of samples. An inflection is observed in the relationship of the value I570/I465to the Ce content in CexPr1-xO2-. With the increase in the wavelength of excitation laser, the Ce content corresponding to the inflection decreases. Combined with the surface concentration obtained by XPS, it can be deduced that the composition of CexPr1-xO2-mixed oxide particles in the surface region and the bulk shell are different, the former is enrichment of Pr component and the latter is enrichment of Ce component. The thickness of the surface layer with rich Pr component decreases with the increase in the Ce content. [ABSTRACT FROM AUTHOR]