Novel synthetic approach to heteroatom doped polycyclic aromatic hydrocarbons: Optimizing the bottom-up approach to atomically precise doped nanographenes

The success of the rational bottom-up approach to nanostructured carbon materials and the discovery of the importance of their doping with heteroatoms puts under the spotlight all synthetic organic approaches to polycyclic aromatic hydrocarbons. The construction of atomically precise heteroatom doped nanographenes has evidenced the importance of controlling its geometry and the position of the doping heteroatoms, since these parameters influence their chemical–physical properties and their applications. The growing interest towards this research topic is testified by the large number of works published in this area, which have transformed a once “fundamental research” into applied research at the cutting edge of technology. This review analyzes the most recent synthetic approaches to this class of compounds

Hydrothermal synthesis and characterization of ethylenediamine-containing molybdenum oxides

Thesis (Master)--İzmir Institute of Technology, Chemistry, İzmir, 2006Includes bibliographical references (leaves: 86-92)Text in English; Abstract: Turkish and Englishxii, 92 leavesRecently, hydrothermal synthesis and characterization of organic-inorganic hybrid materials has attracted great attention.A novel organic-inorganic hybrid material, [Cu(en)MoO4], was hydrothermally synthesized as blue crystals. A mixture of Na2MoO4 CuCl2 NaCl, ethylenediamine and water was loaded into a 23 mL autoclave and heated at 170°C for 72 h. The compound crystallizes in the space group P2(1)/c of the monoclinic system with four formula units in a cell of dimensions a . 7.6743(15) b . 9.4364(19)c . 9.9538(2) . 72.266(3) V . 686.6(2) The structure is composed of {MoO4}tetrahedra and {CuN2O4} octahedra. Each pair of copper octahedra forms a binuclear edge-sharing unit through a {Cu2O2} interaction. The binuclear octahedral units are interconnected through the bridging {MoO4} yielding a layer structure.Purple crystals of a known hybrid material, [Cu(en)2]2[Mo8O26], was hydrothermally obtained under different reaction conditions. A mixture of Na2MoO4 ethylenediamine and water was loaded into the autoclave and heated at 170°C for 72 crystallizes in the space group Pbca of the orthorhombic system with eight formula units in a cell of dimensions a . 13.516 b . 15.548(3) c . 16.725(3) V . 3514.7(12) The structure consists of linked through groups. Each unit forms covalent interactions with two units.Green and black crystals were obtained from the reaction of with different ratios. Via the reaction of NaCl, ethylenediamine and yellow crystals were obtained

Vibrational spectroscopy as a tool to understand plant silicification

Die Ablagerung von Siliziumdioxid ist ein verbreitetes Phänomen, das mit der Toleranz von Pflanzen gegenüber Belastungen korreliert. Die Pflanzen akkumulieren das amorphe Siliziumdioxid in mikroskopischen Partikeln, den Phytolithen, jedoch ist der exakte Mechanismus nicht vollständig aufgeklärt. Um ein besseres Verständnis über die Ablagerung von Siliziumdioxid zu erlangen, wurden verschiedene spektroskopische Techniken an Sorghumblättern und molekularen Modellen angewandt. Festkörper Kernspinresonanz und thermogravimetrische Analysen zeigen, dass die Siliziumdioxidstruktur von der Phytolithe-Extraktion abhängt. Basierend auf Raman- und IR-Daten einzelner Phytolithe lassen sich die Änderungen dieser Strukturen ermitteln. Das deutet auf unterschiedliche biologische Prozesse der Ablagerung des Siliciumdioxids hin. Die Pflanzengewebe in denen Siliciumdioxid abgelagert ist, wurden mit einem multimodalen Ansatz charakterisiert, welcher Fluoreszenz-, Hellfeld- und Rasterelektronenmikroskopie beinhaltet. Die chemische Zusammensetzung der Pflanzengewebe wurden mit Raman- und FTIR-Mikrospektroskopie kartiert. Ein neuartiger Ansatz zur Untersuchung von Pflanzengeweben wurde verwendet, basierend auf der optischen Nahfeldmikroskopie im mittleren IR-Bereich. Dieser ermöglicht eine kombinierte Analyse von mechanischen Materialeigenschaften sowie der chemischen Zusammensetzung und Struktur. Um die Rolle der organischen Matrix zu verstehen, wurden Modellverbindungen betrachtet, die die Ablagerung von Kieselsäure in den Pflanzen induzieren können. In-vitro-Reaktionen konnten eine gleichzeitige Präzipitation von Lignin und Siliciumdioxid sowie eine Polymerisation zusammen mit Peptiden simulieren. Die Ergebnisse lassen starke Wechselwirkungen zwischen diesen Verbindungen vermuten. Neben einem besseren Verständnis verschiedener Aspekte der Silifizierung von Pflanzen werden in dieser Arbeit neue Methoden zur Charakterisierung von Pflanzenproben vorgeschlagen.Silica deposition is a common phenomenon that correlates with plant tolerance to various stresses. Plants accumulate amorphous silica in microscopic particles termed phytoliths, through yet unclear mechanisms. With the aim to gain better understanding of the processes that govern silica deposition, different vibrational techniques were used on sorghum leaves and molecular models to obtain chemical and structural information addressing different length scales. Solid-state Nuclear Magnetic Resonance and thermogravimetric analysis showed that phytolith extraction methods affect silica structure. Nevertheless, Raman and IR analysis of individual phytoliths revealed differences in the structure and composition between phytolith types, suggesting the existence of different biological pathways for silica deposition. The environment of sorghum tissues where silica is deposited was assessed using a multimodal approach consisting of fluorescence, brightfield and scanning electron microscopies, while chemical composition was mapped using Raman and Fourier transformed Infrared microspectroscopy. Scattering-type near-field optical microscopy in the mid-infrared region was used to characterize the plant tissues, in both fixed and native plant samples. The nano-IR images and the mechanical phase image enabled a combined probing of mechanical material properties together with the chemical composition and structure of both the cell walls and the phytolith structures. In vitro reactions simulating lignin-silica co-precipitation and silica polymerization with peptides revealed strong interaction between these compounds and silica, and their possible involvement in silica deposition in the plant. This thesis provides a better understanding of the chemical process that control plant silicification, suggests new methodologies to characterize plant samples, and evaluates the current methods used in plant science

Resolving the chemical substructure of Orion-KL

The Kleinmann-Low nebula in Orion (Orion-KL) is the nearest example of a high-mass star-forming environment. For the first time, we complemented 1.3 mm Submillimeter Array (SMA) interferometric line survey with IRAM 30 m single-dish observations of the Orion-KL region. Covering a 4 GHz bandwidth in total, this survey contains over 160 emission lines from 20 species (25 isotopologues), including 11 complex organic molecules (COMs). At a spatial resolution of 1200 AU, the continuum substructures are resolved. Extracting the spectra from individual substructures and providing the intensity-integrated distribution map for each species, we studied the small-scale chemical variations in this region. Our main results are: (1) We identify lines from the low-abundance COMs CH3COCH3 and CH3CH2OH, as well as tentatively detect CH3CHO and long carbon-chains C6H and HC7N. (2) We find that while most COMs are segregated by type, peaking either towards the hot core (e.g., N-bearing species) or the compact ridge (e.g., O-bearing species like HCOOCH3 and CH3OCH3), while the distributions of others do not follow this segregated structure (e.g., CH3CH2OH, CH3OH, CH3COCH3). (3) We find a second velocity component of HNCO, SO2, 34SO2, and SO lines, which may be associated with a strong shock event in the low-velocity outflow. (4) Temperatures and molecular abundances show large gradients between central condensations and the outflow regions, illustrating a transition between hot molecular core and shock-chemistry dominated regimes. Our observations of spatially resolved chemical variations in Orion-KL provide the nearest reference source for hot molecular core and outflow chemistry, which will be an important example for interpreting the chemistry of more distant HMSFRs.Comment: 51 pages, 17 figures, accepted on 12 March 2015 Dashed lines in Figure 10 of the published paper was missin

Studies on High-Performance Sustainable Blends from Lignin, a Low- Cost Renewable Feedstock

Demand for plant-derived materials has increased in recent years not only to boost the economics in US Agricultural and Forestry sectors, but also to address environmental concerns. Lignin, an aromatic polymer, extracted from biomass has the potential to be used for preparing innovative materials. Developing high-performance polymers from lignin is attractive, but often requires additional lignin modification and cost-intensive functionalization that creates chemical wastes. The overarching goal of this study was the development of sustainable high-performance alloys from thermoplastic and lignin without chemical modification using melt-blending technique, which is technically the most convenient and inexpensive method. Thus, the approach aimed to find value for lignin, a low-cost byproduct of modern biorefineries and woody biomass pulping industry. More specifically, we conducted comprehensive study on thermal, rheological, morphological, and structural properties of the thermoplastic-lignin blends together with lignin’s chemistry and thermal behavior to understand and improve the materials’ performance.The first part of the study involved exploiting lignin’s miscibility with polyethylene oxide (PEO) to enhance the compatibility between lignin and acrylonitrile-butadiene-styrene (ABS) polymer under reactive mixing conditions and develop a recyclable renewable matrix for sustainable composite applications.The second part consisted on manipulating the melt behavior of polyethylene terephthalate (PET) polyester from pre-consumer wastes using a renewable plasticizer tall oil fatty acid (TOFA). To avoid lignin degradation and devolatilization during amalgamation with plasticized PET we devised thermal treatment of lignin that not only improved the stability but also reduced dispersed lignin domains in the matrix.The last part was based on understanding the effect of source-dependent lignin chemistry on its compatibility with a renewable polyester. Organosolv lignin from oak, methanol fractionated Kraft pine lignin, and methanol fractionated acetic acid extracted wheat straw lignin give equivalent melt processability. Blends of these lignins with polylactic acid (PLA) were studied to understand the relationship between the lignin chemistry and resulting blends’ thermal stability, mechanical properties, and melt-rheology.This study answered questions on the role of lignin chemistry that affects the properties of thermoplastic/lignin blends and developed methods to modify melting behavior of both thermoplastic matrices and lignin without thermal degradation

Structural and chemical properties of solid organic inclusion compounds

Urea and thiourea form inclusion compounds in which organic and organometallic guest molecules are confined within non-intersecting, unidirectional tunnels within a solid urea or thiourea host structure. In this thesis, studies have been undertaken using a variety of techniques to examine the properties of urea and thiourea inclusion compounds, with a view to improving the understanding of the forces controlling the ordering of these systems on a molecular scale. From single crystal X-ray diffraction studies of urea inclusion compounds carried out at room temperature, different modes of ordering between guest molecules in adjacent tunnels, dependent on the guest species present, have been observed. Extension of these studies to low temperature, in conjunction with powder X-ray diffraction, has revealed information on phase transitions in both the host and guest substructures of urea inclusion compounds. Computer modelling, using a mathematical model developed for application to one-dimensional inclusion compounds, has been applied to model properties of n-alkane/urea and dimethylketone/urea inclusion compounds. The model has also been applied to the chlorocyclohexane/thiourea inclusion compound. EXAFS spectroscopy has been carried out on α,w-dibromoalkane/urea inclusion compounds to examine the local structural properties of the guest molecules. Halogenocyclohexane/thiourea and halogenocyclohexanes included within the pores of several zeolite-type hosts have also been investigated to determine the conformation of the guest molecules when constrained to occupy a confined environment. Additional studies have examined the potential for the polymerisation of monomeric guest molecules within the tunnels of the organic host structure of perhydrotriphenylene, and a solid state NMR investigation on the effect of magic angle spinning on the observed NMR spectrum for metallocenes

The Present and Future of Planetary Nebula Research. A White Paper by the IAU Planetary Nebula Working Group

We present a summary of current research on planetary nebulae and their central stars, and related subjects such as atomic processes in ionized nebulae, AGB and post-AGB evolution. Future advances are discussed that will be essential to substantial improvements in our knowledge in the field.Comment: accepted for publication in RMxAA; 37 page

Characterisation and treatability of natural organic matter in groundwaters used for drinking water

Natural organic matter contributes to various potable water issues and is present in relatively high concentrations in Western Australian water supplies. Characterising natural organic matter is important for treatment of these waters, and this Thesis contributes to the body of characterisation studies providing a detailed understanding of the origins, structural features and reactivity of natural organic matter, along with its behaviour in drinking water treatment processes, allowing improved catchment management practices and optimisation of treatment processes