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Unravelling the origin of the giant Zn deficiency in wurtzite type ZnO nanoparticles.

ABSTRACT: Owing to its high technological importance for optoelectronics, zinc oxide received much attention. In particular, the role of defects on its physical properties has been extensively studied as well as their thermodynamical stability. In particular, a large concentration of Zn vacancies in ZnO bulk materials is so far considered highly unstable. Here we report that the thermal decomposition of zinc peroxide produces wurtzite-type ZnO nanoparticles with an extraordinary large amount of zinc vacancies (>15%). These Zn vacancies segregate at the surface of the nanoparticles, as confirmed by ab initio calculations, to form a pseudo core-shell structure made of a dense ZnO sphere coated by a Zn free oxo-hydroxide mono layer. In others terms, oxygen terminated surfaces are privileged over zinc-terminated surfaces for passivation reasons what accounts for the Zn off-stoichiometry observed in ultra-fine powdered samples. Such Zn-deficient Zn1-xO nanoparticles exhibit an unprecedented photoluminescence signature suggesting that the core-shell-like edifice drastically influences the electronic structure of ZnO. This nanostructuration could be at the origin of the recent stabilisation of p-type charge carriers in nitrogen-doped ZnO nanoparticles.

SUBMITTER: Renaud A

PROVIDER: S-EPMC4558607 | biostudies-literature | 2015

REPOSITORIES: biostudies-literature

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Unravelling the origin of the giant Zn deficiency in wurtzite type ZnO nanoparticles.

Renaud Adèle A Cario Laurent L Rocquelfelte Xavier X Deniard Philippe P Gautron Eric E Faulques Eric E Das Tilak T Cheviré François F Tessier Franck F Jobic Stéphane S

Scientific reports 20150903

Owing to its high technological importance for optoelectronics, zinc oxide received much attention. In particular, the role of defects on its physical properties has been extensively studied as well as their thermodynamical stability. In particular, a large concentration of Zn vacancies in ZnO bulk materials is so far considered highly unstable. Here we report that the thermal decomposition of zinc peroxide produces wurtzite-type ZnO nanoparticles with an extraordinary large amount of zinc vacan ...[more]

PMID: 26333510

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Project description:Purpose: To examine the gene expression within the spinach root tissues as a response to exposure to nanoparticles. Methods: Sequenced reads were processed using CLC Genomics Workbench 7.0. The reads were trimmed based on quality, length and ambiguity. Resulting reads were assembled into transcript assemblies. Sequence reads were mapped back to the constructed transcriptome. TAs were BLAST searched against a local blast database of coding sequences of Arabidopsis thaliana. Statistical analysis was performed using Baggerley’s test. Transcript assemblies were tested for gene enrichment using GO annotations and the functional categories were determined. MapMan was used to visualize gene expression data of TAs and study the biological pathways. Results: De novo assembly of the trimmed reads yielded 147,733 Transcript Assemblies (TA) with an average length of 645 bp. Largest TA was 16,379 bp. Approximately 89% of the quality trimmed reads from the different samples mapped successfully to the assembly reference. Gene expression data for spinach TAs homologous to Arabidopsis genes show upregulation of protein degradation pathways in the nano-ZnO treatment compared to the non-nanoZnO, this upregulation is coupled with a down regulation of the genes in the protein synthesis pathways crucial role in the spinach plant responses to ZnO nanoparticle exposure. Genes associated (REDOX, signaling and transcription factors) with responses to stresses (both abiotic and biotic) were upregulated upon exposure to ZnO nanoparticles. Additionally genes in biosynthesis pathways of jasmonate and gibberellins genes were up-regulated upon exposure to ZnO nanoparticles in spinach. Conclusions: A de novo transcriptome was developed for spinach. When spinach plants were exposed to ZnO nanoparticles, they seem to sense the nanoparticles similarly to external chemicals or pathogens and induced production of reactive oxygen species. Hormone signaling pathways were activated leading to the induced expression of hormones with different roles in defense.

Project description:Zinc oxide nanoparticles (ZnO-NPs) hold promise as novel fertilizer nutrients for crops. However, their ultra-small size could hinder large-scale field application due to potential for drift, untimely dissolution or aggregation. In this study, urea was coated with ZnO-NPs (1%) or bulk ZnO (2%) and evaluated in wheat (Triticum aestivum L.) in a greenhouse, under drought (40% field moisture capacity; FMC) and non-drought (80% FMC) conditions, in comparison with urea not coated with ZnO (control), and urea with separate ZnO-NP (1%) or bulk ZnO (2%) amendment. Plants were exposed to ? 2.17 mg/kg ZnO-NPs and ? 4.34 mg/kg bulk-ZnO, indicating exposure to a higher rate of Zn from the bulk ZnO. ZnO-NPs and bulk-ZnO showed similar urea coating efficiencies of 74-75%. Drought significantly (p ? 0.05) increased time to panicle initiation, reduced grain yield, and inhibited uptake of Zn, nitrogen (N), and phosphorus (P). Under drought, ZnO-NPs significantly reduced average time to panicle initiation by 5 days, irrespective of coating, and relative to the control. In contrast, bulk ZnO did not affect time to panicle initiation. Compared to the control, grain yield increased significantly, 51 or 39%, with ZnO-NP-coated or uncoated urea. Yield increases from bulk-ZnO-coated or uncoated urea were insignificant, compared to both the control and the ZnO-NP treatments. Plant uptake of Zn increased by 24 or 8% with coated or uncoated ZnO-NPs; and by 78 or 10% with coated or uncoated bulk-ZnO. Under non-drought conditions, Zn treatment did not significantly reduce panicle initiation time, except with uncoated bulk-ZnO. Relative to the control, ZnO-NPs (irrespective of coating) significantly increased grain yield; and coated ZnO-NPs enhanced Zn uptake significantly. Zn fertilization did not significantly affect N and P uptake, regardless of particle size or coating. Collectively, these findings demonstrate that coating urea with ZnO-NPs enhances plant performance and Zn accumulation, thus potentiating field-scale deployment of nano-scale micronutrients. Notably, lower Zn inputs from ZnO-NPs enhanced crop productivity, comparable to higher inputs from bulk-ZnO. This highlights a key benefit of nanofertilizers: a reduction of nutrient inputs into agriculture without yield penalities.

Dataset Information

Unravelling the origin of the giant Zn deficiency in wurtzite type ZnO nanoparticles.

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Unravelling the origin of the giant Zn deficiency in wurtzite type ZnO nanoparticles.

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