| 1. |
- Hartmann, Nanna B., et al.
(författare)
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Are We Speaking the Same Language? Recommendations for a Definition and Categorization Framework for Plastic Debris
- 2019
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Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 53:3, s. 1039-1047
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Tidskriftsartikel (refereegranskat)abstract
- Copyright © 2019 American Chemical Society. The accumulation of plastic litter in natural environments is a global issue. Concerns over potential negative impacts on the economy, wildlife, and human health provide strong incentives for improving the sustainable use of plastics. Despite the many voices raised on the issue, we lack a consensus on how to define and categorize plastic debris. This is evident for microplastics, where inconsistent size classes are used and where the materials to be included are under debate. While this is inherent in an emerging research field, an ambiguous terminology results in confusion and miscommunication that may compromise progress in research and mitigation measures. Therefore, we need to be explicit on what exactly we consider plastic debris. Thus, we critically discuss the advantages and disadvantages of a unified terminology, propose a definition and categorization framework, and highlight areas of uncertainty. Going beyond size classes, our framework includes physicochemical properties (polymer composition, solid state, solubility) as defining criteria and size, shape, color, and origin as classifiers for categorization. Acknowledging the rapid evolution of our knowledge on plastic pollution, our framework will promote consensus building within the scientific and regulatory community based on a solid scientific foundation.
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| 2. |
- Hlukhyy, Viktor, et al.
(författare)
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Extreme differences in oxidation states : Synthesis and structural analysis of the germanide oxometallates A 10[Ge 9] 2[WO 4] as well as A 10+x[Ge 9] 2[W 1-xNb xO 4] with A = K and Rb containing [Ge 9] 4- polyanions
- 2012
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Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 51:7, s. 4058-4065
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Tidskriftsartikel (refereegranskat)abstract
- Semitransparent dark-red or ruby-red moisture- and air-sensitive single crystals of A 10+x[Ge 9] 2[W 1-xNb xO 4] (A = K, Rb; x = 0, 0.35) were obtained by high-temperature solid-state reactions. The crystal structure of the compounds was determined by single-crystal X-ray diffraction experiments. They crystallize in a new structure type (P2 1/c, Z = 4) with a = 13.908(1) Å, b = 15.909(1) Å, c = 17.383(1) Å, and α = 90.050(6)° for K 10.35(1)[Ge 9] 2[W 0.65(1)Nb 0.35(1)O 4]; a = 14.361(3) Å, b = 16.356(3) Å, c = 17.839(4) Å, and α = 90.01(3)° for Rb 10.35(1)[Ge 9] 2[W 0.65(1)Nb 0.35(1)O 4]; a = 13.8979(2) Å, b = 15.5390(3) Å, c = 17.4007(3) Å, and α = 90.188(1)° for K 10[Ge 9] 2WO 4; and a = 14.3230(7) Å, b = 15.9060(9) Å, c = 17.8634(9) Å, and α = 90.078(4)° for Rb 10[Ge 9] 2WO 4. The compounds contain discrete Ge 9 4- Wades nido clusters and WO 4 2- (or NbO 4 3-) anions, which are packed according to a hierarchical atom-to-cluster replacement of the Al 2Cu prototype and are separated by K and Rb cations, respectively. The alkali metal atoms occupy the corresponding tetrahedral sites of the Al 2Cu prototype. The amount of the alkali metal atoms on these diamagnetic compounds corresponds directly to the amount of W substituted by Nb. Thus, the transition metals W and Nb appear with oxidation numbers +6 and +5, respectively, in the vicinity of a [Ge 9] 4- polyanion. The crystals of the mixed salts were further characterized by Raman spectroscopy. The Raman data are in good agreement with the results from the X-ray structural analyses.
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| 3. |
- Palma, Carlos-Andres, et al.
(författare)
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Photo-induced C-C reactions on insulators towards photolithography of graphene nanoarchitectures
- 2014
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 136, s. 4651-4658
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Tidskriftsartikel (refereegranskat)abstract
- On-surface chemistry for atomically precise sp2 macromolecules requires top-down lithographic methods on insulating surfaces in order to pattern the long-range complex architectures needed by the semiconductor industry. Here, we fabricate sp2-carbon nm-thin films on insulators and under ultra-high vacuum (UHV) conditions from photo-coupled brominated precursors. We reveal that covalent coupling is initiated by C-Br bond cleavage through photon energies exceeding 4.4 eV, as monitored by laser desorption ionization (LDI) mass spectrometry (MS) and X-ray photoelectron spectroscopy (XPS). Density functional theory (DFT) gives insight into the mechanisms of C-Br scission and C-C coupling processes. Further, unreacted material can be sublimed and the coupled sp2-carbon precursors can be graphitized by e-beam treatment at 500°C, demonstrating promising applications in photolithography of graphene nanoarchitectures. Our results present UV-induced reactions on insulators for the formation of all sp2-carbon architectures, thereby converging top-down lithography and bottom-up on-surface chemistry into technology.
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