Origin of Life: Aliphatic aldehydes in the Earth’s crust – remains of prebiotic chemistry?

The Origin of Life is a question that has not yet been solved in the natural sciences. Some promising interpretative approaches are related to hydrothermal activities. Hydrothermal environments contain all necessary elements for the development of precursor molecules. There are possibly catalytically active surfaces and wide ranges of pressure and temperature conditions. The chemical composition of hydrothermal fluids together with periodically fluctuating physical conditions should open up multiple pathways towards prebiotic molecules. Already in 2017, we detected prebiotic organic substances, including a homologous series of aldehydes in more than 3 billion years old Archean quartz crystals from Western Australia. In order to approach the question if the transformation of inorganic into organic substances is an ongoing process, we investigated a drill core from the geologically young Wehr caldera in Germany at a depth of 1000 m. Here we show the existence of a similar homologous series of aldehydes (C8 to C16) in the fluid inclusions of the drill core calcites, a finding that supports the thesis that hydrothermal environments could possibly be the material source for the origin of life.

Antibacterial Activity and Mesophase Identification of Azomethnine and Azo derivatives

A new mesogenic homologous series of liquid crystalline azomethnine and azo derivatives of 4ꞌ-nalkoxybenzylidiene- 4-aminoazobenzene has been synthesized and characterized by a combination of elemental analysis and standard spectroscopic methods. In the present series, nematic mesophase commences from n-propyloxy derivative as enantiotropic and persists up to the last member synthesized except in derivative C10. The smectic A (SmA) mesophases commences from n-pentyloxy derivative as enantiotropic and also persists up to ntetradecyloxy synthesized. Imine linkage (-CH═N-) between central and terminal benzene rings helping to understand the polarizability effect as well as nature of mesophase as stability gets reduced due to the presence of nitrogen in the ring. The mesomorphic properties of present series are of great importance to evaluate the effects of central linkage on mesomorphism. The mesomorphic properties of present series were compared with other structurally related mesogenic homologous series to evaluate the effects of central linkage on mesomorphism.

Bi8Te3, the 11-Atom Layer Member of the Tetradymite Homologous Series

Bi8Te3 is a member of the tetradymite homologous series, previously shown to be compositionally and structurally distinct from hedleyite, Bi7Te3, yet inadequately characterized structurally. The phase is identified in a sample from the Hedley district, British Columbia, Canada. Compositions are documented by electron probe microanalysis and structures are directly imaged using high-angle annular dark field (HAADF) scanning transmission electron microscopy (STEM). Results confirm that Bi8Te3 has an 11-atom layer structure, in which three Bi-Bi pairs are placed adjacent to the five-atom sequence (Te-Bi-Te-Bi-Te). Bi8Te3 has trigonal symmetry (space group R3¯m) with unit cell dimensions of a = ~4.4 Å and c = ~63 Å calculated from measurements on representative electron diffraction patterns. The model is assessed by STEM simulations and EDS mapping, all displaying good agreement with the HAADF STEM imaging. Lattice-scale intergrowths are documented in phases replacing Bi8Te3, accounting for the rarity of this phase in nature. These results support prior predictions of crystal structures in the tetradymite homologous series from theoretical modeling and indicate that other phases are likely to exist for future discovery. Tetradymite homologues are mixed-layer compounds derived as one-dimensional superstructures of a basic rhombohedral sub-cell. Each member of the series has a discrete stoichiometric composition and unique crystal structure.

Kinetics of Phase Separation Polyamic Acid (PAA) Solutions with Various Precipitants

A new method with limited layer of polymeric solution was used to study the kinetics of precipitation of highly concentrated solutions of PAA in various precipitants; it allows to quickly estimate the rate of formation of the polymer membrane, adequately evaluate its morphology without membrane casting and reduce the experimental time for the preparation of a membrane with required porous structure. It was shown that the rate of precipitation of 18 wt. % PAA solution and the morphology of a layer resulting from the phase separation formed upon contact with water differ significantly in a “limited” layer and in a layer of infinite thickness. It was shown that morphology of a layer formed during phase separation of 18 wt. % PAA solution with water in the “unlimited” layer corresponds to morphology, which is formed in precipitation by 50% NMP-water solution of the same polymer solution in a “limited” layer. This supports the assumption about the strong dilution of the precipitant with a solvent when an “unlimited” layer method is used. In addition, during the investigation of the kinetics of the phase separation by water it was found that the rate of precipitation of highly concentrated polymer solution in a “limited” layer (ν = 8.3 μm/s) is significantly higher than in “unlimited” (ν = 1.7 μm/s). Using this method with “limited” layer, the kinetics of the phase separation of 18 wt. % PAA solution in aliphatic alcohols was also investigated; the rate of precipitation of the polymer solution is inversely proportional to their viscosity. Approximately twofold increase of dynamic viscosity with the chain length for each subsequent alcohol in the homologous series, the rate of precipitation of the PAA solution in them was also reduced by about 2 times