13C‐labeled dicarboxylic acids HO213C‐(CH2)n‐13CO2H (n = 10, 12, 14, 16, 18, 20, 22, 24, 26, 28) have been synthesized as internal standards for LC‐MS and GC‐MS analysis of cutin and suberin monomer degradation by soil‐based microorganisms. Different synthetic strategies had to be applied depending on the chain length of the respective synthetic target and because of economic considerations. 13C‐labels were introduced by nucleophilic substitution of a suitable leaving group with labelled potassium cyanide and subsequent hydrolysis of the nitriles to produce the corresponding dicarboxylic acids. All new compounds are characterized by GC/MS, IR, and NMR methods as well as by elemental analysis.

Amorphous hydrogenated carbon (a-C:H) films are applied 500 nm thick on Si(100) via plasma-enhanced chemical vapor deposition (PECVD) using ethyne. Present plasma conditions enrich the sp 2 -content especially toward the outermost a-C:H layers, which in turn are used to attach a photoactive Ru-polypyridyl complex to the surface. An azo-bridged dinuclear Ru-polypyridyl complex is optimized in synthesis and the final mononuclear fragment attached on a-C:H photochemically under UV-irradiation with concomitant N 2 release. The Ru-polypyridyl complex is characterized by MS, NMR, IR, UV/vis, fluorescence spectroscopy, and time-dependent density functional theory (DFT) calculations. Crystallographic data for the intermediate 4-nitro-2-(pyridin-2-yl)pyridine 1-oxide as essential precursor are established. Morphological characteristics of the a-C:H @ Si and final Ru(complex) @ a-C:H @ Si combinations are determined by atomic force microscopy (AFM) revealing individual grain-like structures. The presence of Ru on the a-C:H @ Si surface is initially verified qualitatively by laser-induced breakdown spectroscopy (LIBS) and by inductively coupled plasma-sector field mass spectrometry (ICP-SF-MS) after chemical digestion. With laser ablation-ICP-MS mapping, full Ru coverage is proven, also revealing inhomogeneities in terms of "Ru hot spots". The current investigation proves the successful attachment of a Ru-complex on a-C:H and indicates a starting point for the development of further material combinations for feasible sunlight to energy conversions. Surface FunctionalizationThe ORCID identification number(s) for the author(s) of this article can be found under https://doi.

The transformation and turnover time of medium- to long-chain dicarboxylic acids (DCA) in soil is regulated by microbial uptake and mineralization. However, the chain length of n-alkyl lipids may have a remarkable influence on its microbial utilization and mineralization and therefore on the formation of stable soil organic carbon from e.g. leave- needle- and root-derived organic matter during decomposition. To investigate their size dependent mineralization and microbial incorporation, four DCA of different chain lengths (12–30 carbon atoms), that were 13C labeled at each of their terminal carboxylic groups, were applied to the Ah horizon of a Fluvic Gleysol. Incorporation of 13C into CO2 and in distinct microbial groups classified by phospholipid fatty acid (PLFA) analysis was investigated. Mineralization of DCA and incorporation into PLFA decreased with increasing chain length, and the mineralization rate was highest during the first days of incubation. Half-life time of DCA carbon in soil increased from 7.6 days for C12 DCA to 86.6 days for C18 DCA and decreased again to 46.2 days for C22 DCA, whereas C30 DCA had the longest half-life time. Rapid and efficient uptake of C12 DCA as an intact molecule was observable. Gram-negative bacteria incorporated higher amounts of DCA-derived 13C compared to other microbial groups, especially compared to actinomycetes and fungi during the first phase of incubation. However, the incorporation of C12 DCA derived 13C into the PLFA of actinomycetes, and fungi increased steadily during the entire incubation time, suggesting that those groups take up the 13C label from necromass of bacteria that used the C12 DCA for formation of their lipids before.

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Funding informationUniversity Koblenz -Landau 13 C-labelled ω-hydroxy-carboxylic acids HO 2 13 C-(CH 2 ) n -CH 2 OH or HO 2 C-(CH 2 ) n -13 CH 2 OH (n = 12, 16, 20, 28) with 13 C labels selectively introduced either at the carboxy group or at the primary alcohol function at the end of the hydrocarbon chain have been synthesized. Different synthetic strategies had to be applied depending on the position of the label, the chain length of the respective synthetic target and due to economic considerations. 13 C labels in general were introduced by nucleophilic substitution of a suitable leaving group with labelled potassium cyanide and subsequent hydrolysis of the nitriles to produce the corresponding labelled carboxy functions, which may also be reduced to give the labelled primary alcohol group. All new compounds are characterized by GC/MS, IR and NMR methods as well as by elemental analysis.