Stop-frame filming and discovery of reactions at the single-molecule level by transmission electron microscopy

We report an approach – named chemTEM – to follow chemical transformations at the single-molecule level with the electron beam of a transmission electron microscope (TEM) applied as both a tuneable source of energy and a sub-Angstrom imaging probe. Deposited on graphene, disk-shaped perchlorocoronene molecules are precluded from intermolecular interactions. This allows monomolecular transformations to be studied at the single-molecule level in real time and reveals chlorine elimination and reactive aryne formation as a key initial stage of multi-step reactions initiated by the 80 keV e-beam. Under the same conditions, perchlorocoronene confined within a nanotube cavity, where the molecules are situated in very close proximity to each other, enables imaging of intermolecular reactions, starting with the Diels-Alder cycloaddition of a generated aryne, followed by rearrangement of the angular adduct to a planar polyaromatic structure and the formation of a perchlorinated zigzag nanoribbon of graphene as the final product. ChemTEM enables the entire process of polycondensation, including the formation of metastable intermediates, to be captured in a one-shot ‘movie’. A molecule with a similar size and shape but with a different chemical composition, octathio[8]circulene, under the same conditions undergoes another type of polycondensation via thiyl biradical generation and subsequent reaction leading to polythiophene nanoribbons with irregular edges incorporating bridging sulphur atoms. Graphene or carbon nanotubes supporting the individual molecules during chemTEM studies ensure that the elastic interactions of the molecules with the e-beam are the dominant forces that initiate and drive the reactions we image. Our ab initio DFT calculations explicitly incorporating the e-beam in the theoretical model correlate with the chemTEM observations and give a mechanism for direct control not only of the type of the reaction but also of the reaction rate. Selection of the appropriate e-beam energy and control of the dose rate in chemTEM enabled imaging of reactions on a timeframe commensurate with TEM image capture rates, revealing atomistic mechanisms of previously unknown processes

Detailed Analysis of Dorsal-Ventral Gradients of Gene Expression in the Hippocampus of Adult Rats

We performed RNA sequencing of the dorsal and ventral parts of the hippocampus and compared it with previously published data to determine the differences in the dorsoventral gradients of gene expression that may result from biological or technical variability. Our data suggest that the dorsal and ventral parts of the hippocampus differ in the expression of genes related to signaling pathways mediated by classical neurotransmitters (glutamate, GABA, monoamines, etc.) as well as peptide and Wnt ligands. These hippocampal parts also diverge in the expression of axon-guiding molecules (both receptors and ligands) and splice isoforms of genes associated with intercellular signaling and cell adhesion. Furthermore, analysis of differential expressions of genes specific for astrocytes, microglia, oligodendrocytes, and vascular cells suggests that non-neuronal cells may also differ in the characteristics between hippocampal parts. Analysis of expression of transposable elements showed that depletion of ribosomal RNA strongly increased the representation of transposable elements in the RNA libraries and helped to detect a weak predominance of expression of these elements in the ventral hippocampus. Our data revealed new molecular dimensions of functional differences between the dorsal and ventral hippocampus and points to possible cascades that may be involved in the longitudinal organization of the hippocampus

Innovating Carbon Materials Open New Possibilities For Increasing Performance Of Li-ion Batteries

The purpose of research and development, the results of which are presented in this publication is the modification of carbon materials for use in anode and cathode materials Li batteries with non-aqueous electrolytes. Innovative carbon materials will provide increased energy and safety of lithium current sources, while at the same time reducing the cost of lithium current sources

Porous metal-organic polyhedra:Morphology, porosity, and guest binding

Designing porous materials which can selectively adsorb CO2 or CH4 is an important environmental and industrial goal which requires an understanding of the host-guest interactions involved at the atomic scale. Metal-organic polyhedra (MOPs) showing permanent porosity upon desolvation are rarely observed. We report a family of MOPs (Cu-1a, Cu-1b, Cu-2), which derive their permanent porosity from cavities between packed cages rather than from within the polyhedra. Thus, for Cu-1a, the void fraction outside the cages totals 56% with only 2% within. The relative stabilities of these MOP structures are rationalized by considering their weak nondirectional packing interactions using Hirshfeld surface analyses. The exceptional stability of Cu-1a enables a detailed structural investigation into the adsorption of CO2 and CH4 using in situ X-ray and neutron diffraction, coupled with DFT calculations. The primary binding sites for adsorbed CO2 and CH4 in Cu-1a are found to be the open metal sites and pockets defined by the faces of phenyl rings. More importantly, the structural analysis of a hydrated sample of Cu-1a reveals a strong hydrogen bond between the adsorbed CO2 molecule and the Cu(II)-bound water molecule, shedding light on previous empirical and theoretical observations that partial hydration of metal-organic framework (MOF) materials containing open metal sites increases their uptake of CO2. The results of the crystallographic study on MOP-gas binding have been rationalized using DFT calculations, yielding individual binding energies for the various pore environments of Cu-1a