Quantum-dot-like states in molybdenum disulfide nanostructures due to the interplay of local surface wrinkling, strain, and dielectric confinement

The observation of quantum light emission from atomically thin transition metal dichalcogenides has opened a new field of applications for these material systems. The corresponding excited charge-carrier localization has been linked to defects and strain, while open questions remain regarding the microscopic origin. We demonstrate that the bending rigidity of these materials leads to wrinkling of the two-dimensional layer. The resulting strain field facilitates strong carrier localization due to its pronounced influence on the band gap. Additionally, we consider charge carrier confinement due to local changes of the dielectric environment and show that both effects contribute to modified electronic states and optical properties. The interplay of surface wrinkling, strain-induced confinement, and local changes of the dielectric environment is demonstrated for the example of nanobubbles that form when monolayers are deposited on substrates or other two-dimensional materials

Intermolecular interactions in crystalline 1-(adamantane-1-carbonyl)-3-substituted thioureas with Hirshfeld surface analysis

The conformationally congested species 1-(adamantane-1-carbonyl)-3-(2,4,6-trimethylphenyl)thiourea has been prepared and fully characterized by elemental analyses, FTIR, 1H NMR, 13C NMR and mass spectrometry. Its crystal structure was determined by single-crystal X-ray diffraction. The dihedral angle between the plane of the 2,4,6-trimethylphenyl group and the plane of the thiourea fragment was optimized by theoretical calculations applying the B3LYP/6-311++G(d,p) level for the purpose of investigating the conformational effects on the stabilization of the crystal packing. A detailed analysis of the intermolecular interactions in a series of six closely related phenylthiourea species bearing the 1-(adamantane-1-carbonyl) group has been performed based on the Hirshfeld surfaces and their associated two-dimensional fingerprint plots. The relative contributions of the main intermolecular contacts as well as the enrichment ratios derived from the Hirshfeld surface analysis establish the 1-acyl thiourea synthon to be a widespread contributor.Fil: Saeed, Aamer. Quaid-I-Azam University; PakistánFil: Bolte, Michael. Goethe Universitat Frankfurt; AlemaniaFil: Erben, Mauricio Federico. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Química Inorgánica "Dr. Pedro J. Aymonino". Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Centro de Química Inorgánica "Dr. Pedro J. Aymonino"; ArgentinaFil: Pérez, Hiram. Universidad de La Habana; Cub

Intermolecular interactions in crystalline 1-(adamantane-1-carbonyl)-3-substituted thioureas with Hirshfeld surface analysis

The conformationally congested species 1-(adamantane-1-carbonyl)-3-(2,4,6-trimethylphenyl)thiourea has been prepared and fully characterized by elemental analyses, FTIR, 1H NMR, 13C NMR and mass spectrometry. Its crystal structure was determined by single-crystal X-ray diffraction. The dihedral angle between the plane of the 2,4,6-trimethylphenyl group and the plane of the thiourea fragment was optimized by theoretical calculations applying the B3LYP/6-311++G(d,p) level for the purpose of investigating the conformational effects on the stabilization of the crystal packing. A detailed analysis of the intermolecular interactions in a series of six closely related phenylthiourea species bearing the 1-(adamantane-1-carbonyl) group has been performed based on the Hirshfeld surfaces and their associated two-dimensional fingerprint plots. The relative contributions of the main intermolecular contacts as well as the enrichment ratios derived from the Hirshfeld surface analysis establish the 1-acyl thiourea synthon to be a widespread contributor.Facultad de Ciencias ExactasCentro de Química Inorgánic

On the roles of close shell interactions in the structure of acyl-substituted hydrazones: An experimental and theoretical approach

The 2-(phenyl-hydrazono)-succinic acid dimethyl ester compound was synthesized by reacting phenylhydrazine with dimethylacetylene dicarboxylate at room temperature and characterized by elemental analysis, infrared, Raman, 1H and 13C NMR spectroscopies and mass spectrometry. Its solid state structure was determined by X-ray diffraction methods. The X-ray structure determination corroborates that the molecule is present in the crystal as the hydrazone tautomer, probably favored by a strong intramolecular N-H···O=C hydrogen bond occurring between the carbonyl (-C=O) and the hydrazone -C=N-NH- groups. A substantial fragment of the molecular skeleton is planar due to an extended π-bonding delocalization. The topological analysis of the electron densities (Atom in Molecule, AIM) allows characterization of intramolecular N-H···O interaction, that can be classified as a resonant assisted hydrogen bond (RAHB). Moreover, the Natural Bond Orbital population analysis confirms that a strong hyperconjugative lpO1 → σ∗(N2-H) remote interaction between the C2=O1 and N2-H groups takes place. Periodic system electron density and topological analysis have been applied to characterize the intermolecular interactions in the crystal. Weak intermolecular interactions determine the crystal packing, and the prevalence of non-directional dispersive contributions are inferred on topological grounds. The IR spectrum of the crystalline compound was investigated by means of density functional theory calculations carried out with periodic boundary conditions on the crystal, showing excellent agreement between theory and the experiments. The vibrational assignment is complemented with the analysis of the Raman spectrum.Instituto de Física La PlataCentro de Química Inorgánic

On the roles of close shell interactions in the structure of acyl-substituted hydrazones: An experimental and theoretical approach

The 2-(phenyl-hydrazono)-succinic acid dimethyl ester compound was synthesized by reacting phenylhydrazine with dimethylacetylene dicarboxylate at room temperature and characterized by elemental analysis, infrared, Raman, 1H and 13C NMR spectroscopies and mass spectrometry. Its solid state structure was determined by X-ray diffraction methods. The X-ray structure determination corroborates that the molecule is present in the crystal as the hydrazone tautomer, probably favored by a strong intramolecular N-H···O=C hydrogen bond occurring between the carbonyl (-C=O) and the hydrazone -C=N-NH- groups. A substantial fragment of the molecular skeleton is planar due to an extended π-bonding delocalization. The topological analysis of the electron densities (Atom in Molecule, AIM) allows characterization of intramolecular N-H···O interaction, that can be classified as a resonant assisted hydrogen bond (RAHB). Moreover, the Natural Bond Orbital population analysis confirms that a strong hyperconjugative lpO1 → σ∗(N2-H) remote interaction between the C2=O1 and N2-H groups takes place. Periodic system electron density and topological analysis have been applied to characterize the intermolecular interactions in the crystal. Weak intermolecular interactions determine the crystal packing, and the prevalence of non-directional dispersive contributions are inferred on topological grounds. The IR spectrum of the crystalline compound was investigated by means of density functional theory calculations carried out with periodic boundary conditions on the crystal, showing excellent agreement between theory and the experiments. The vibrational assignment is complemented with the analysis of the Raman spectrum.Fil: Saeed, Aamer. Quaid-I-Azam University; PakistánFil: Ifzan Arshad, M.. Quaid-I-Azam University; PakistánFil: Bolte, Michael. Goethe Universitat Frankfurt; AlemaniaFil: Fantoni, Adolfo Carlos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; ArgentinaFil: Delgado Espinosa, Zuly Yuliana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Química Inorgánica "Dr. Pedro J. Aymonino". Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Centro de Química Inorgánica "Dr. Pedro J. Aymonino"; ArgentinaFil: Erben, Mauricio Federico. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Química Inorgánica "Dr. Pedro J. Aymonino". Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Centro de Química Inorgánica "Dr. Pedro J. Aymonino"; Argentin

Recommendations on the development, use and provision of Research Software

These recommendations describe challenges relating to research software and provide recommendations for the development, use and provision of this type of software. The relevance of research software to modern research should be clearly underlined, especially in the context of political debate on digital transformation in the sciences and humanities. This document was prepared by the Research Software Working Group, established in 2016, within the Alliance initiative

Intermolecular interactions in crystalline 1-(adamantane-1-carbonyl)-3-substituted thioureas with Hirshfeld surface analysis

The conformationally congested species 1-(adamantane-1-carbonyl)-3-(2,4,6-trimethylphenyl)thiourea has been prepared and fully characterized by elemental analyses, FTIR, 1H NMR, 13C NMR and mass spectrometry. Its crystal structure was determined by single-crystal X-ray diffraction. The dihedral angle between the plane of the 2,4,6-trimethylphenyl group and the plane of the thiourea fragment was optimized by theoretical calculations applying the B3LYP/6-311++G(d,p) level for the purpose of investigating the conformational effects on the stabilization of the crystal packing. A detailed analysis of the intermolecular interactions in a series of six closely related phenylthiourea species bearing the 1-(adamantane-1-carbonyl) group has been performed based on the Hirshfeld surfaces and their associated two-dimensional fingerprint plots. The relative contributions of the main intermolecular contacts as well as the enrichment ratios derived from the Hirshfeld surface analysis establish the 1-acyl thiourea synthon to be a widespread contributor.Facultad de Ciencias ExactasCentro de Química Inorgánic

Group-finding with photometric redshifts: The Photo-z Probability Peaks algorithm

We present a galaxy group-finding algorithm, the Photo-z Probability Peaks (P3) algorithm, optimized for locating small galaxy groups using photometric redshift data by searching for peaks in the signal-to-noise of the local overdensity of galaxies in a three-dimensional grid. This method is an improvement over similar two-dimensional matched-filter methods in reducing background contamination through the use of redshift information, allowing it to accurately detect groups at lower richness. We present the results of tests of our algorithm on galaxy catalogues from the Millennium Simulation. Using a minimum S/N of 3 for detected groups, a group aperture size of 0.25 Mpc/h, and assuming photometric redshift accuracy of sigma_z = 0.05 it attains a purity of 84% and detects ~295 groups/deg.^2 with an average group richness of 8.6 members. Assuming photometric redshift accuracy of sigma_z = 0.02, it attains a purity of 97% and detects ~143 groups/deg.^2 with an average group richness of 12.5 members. We also test our algorithm on data available for the COSMOS field and the presently-available fields from the CFHTLS-Wide survey, presenting preliminary results of this analysis.Comment: Accepted for publication by MNRAS, 16 pages, 11 color figure

Epigenetic rather than genetic factors may explain phenotypic divergence between coastal populations of diploid and tetraploid Limonium spp. (Plumbaginacaeae) in Portugal

BACKGROUND: The genus Limonium Miller comprises annual and perennial halophytes that can produce sexual and/or asexual seeds (apomixis). Genetic and epigenetic (DNA methylation) variation patterns were investigated in populations of three phenotypically similar putative sexual diploid species (L. nydeggeri, L. ovalifolium, L. lanceolatum), one sexual tetraploid species (L. vulgare) and two apomict tetraploid species thought to be related (L. dodartii, L. multiflorum). The extent of morphological differentiation between these species was assessed using ten diagnostic morphometric characters. RESULTS: A discriminant analysis using the morphometric variables reliably assigns individuals into their respective species groups. We found that only modest genetic and epigenetic differentiation was revealed between species by Methylation Sensitive Amplification Polymorphism (MSAP). However, whilst there was little separation possible between ploidy levels on the basis of genetic profiles, there was clear and pronounced interploidy discrimination on the basis of epigenetic profiles. Here we investigate the relative contribution of genetic and epigenetic factors in explaining the complex phenotypic variability seen in problematic taxonomic groups such as Limonium that operate both apomixis and sexual modes of reproduction. CONCLUSIONS: Our results suggest that epigenetic variation might be one of the drivers of the phenotypic divergence between diploid and tetraploid taxa and discuss that intergenome silencing offers a plausible mechanistic explanation for the observed phenotypic divergence between these microspecies. These results also suggest that epigenetic profiling offer an additional tool to infer ploidy level in stored specimens and that stable epigenetic change may play an important role in apomict evolution and species recognition