Editorial Open Access

Chemistry congress : 2019-Short range order, crystal nucleation and crystal growth in liquid colloidal suspensions - Dieter M Herlach

Abstract

 Deputy Chairman German Society of Materials Science and Engineering The chemistry of graphene is growing rapidly in last decade and broad range of graphene derivates was prepared. Nevertheless, only two stoichiometric derivates are currently known: hydrogenated and fluorinated graphene (graphane and fluorographene). Compared to graphene, these materials exhibit significantly different properties, e.g. higher reactivity as well as large differences in physical properties. Especially fluorographene can be applied as a substrate for nucleophilic substitution reactions, which significantly extend the possible chemical modifications of graphene. Currently, the chemistry of the other 2D materials starts to be explored. However, the chemistry of inorganic 2D materials like pnictogens and transition metal dichalcogenides is not well known and only several procedures were already reported. In comparison with graphene, new synthetic protocols have to be applied because the chemistry of these materials is extremely variable. In the case of transition metal dichalcogenides, the formation of the M-X-C bond (M is a metal, X is any chalcogenide) can be used as a starting point for exploring their chemistry and for further derivatisation. The chemistry of layered pnictogens is significantly different. In this case, various reactions including nucleophilic substitution can be applied, however, the bonding through the oxygen functionalities on pnictogen surface is observed in many cases. Graphene is that the only sort of carbon (or solid material) during which every atom is out there for reaction from two sides (due to the 2D structure). Atoms at the sides of a graphene sheet have special chemical reactivity. Graphene has the very best ratio of edge atoms of any allotrope. Defects within a sheet increase its chemical reactivity. The onset temperature of reaction between the basal plane of single-layer graphene and oxygen gas is below 260 °C (530 K). Graphene combusts at 350 °C (620 K). Graphene is usually modified with oxygen- and nitrogen-containing functional groups and analyzed by infrared spectroscopy and X-ray photoelectron spectroscopy. However, determination of structures of graphene with oxygen-and nitrogen- functional groups requires the structures to be controlled. Contrary to the perfect 2D structure of graphene, chemical applications of graphene need either structural or chemical irregularities, as perfectly flat graphene is chemically inert. In other words, the definition of a perfect graphene is different in chemistry and physics. Soluble fragments of graphene are often prepared within the laboratory[ through chemical modification of graphite. First, microcrystalline graphite is treated with an acidic mixture of vitriol and aqua fortis . A series of oxidation and exfoliation steps produce small graphene plates with carboxyl groups at their edges. These are converted to acid chloride groups by treatment with thionyl chloride; next, they're converted to the corresponding graphene amide via treatment with octadecylamine. The resulting material is soluble in tetrahydrofuran, tetrachloromethane and dichloroethane. Nucleic acid analogues are compounds which are analogous (structurally similar) to present RNA and DNA, utilized in medicine and in biology research. Nucleic acids are chains of nucleotides, which are composed of three parts: a phosphate backbone, a pentose sugar, either ribose or deoxyribose, and one among four nucleobases. An analogue may have any of those altered. Typically the analogue nucleobases confer, among other things, different base pairing and base stacking properties. Examples include universal bases, which may pair with all four canonical bases, and phosphate-sugar backbone analogues like PNA, which affect the properties of the chain (PNA can even form a triple helix). macromolecule analogues also are called Xeno macromolecule and represent one among the most pillars of xenobiology, the planning of new-to-nature sorts of life supported alternative biochemistries. Artificial macromolecule s include peptide nucleic acid

 Dieter M Herlach

To read the full article Download Full Article