J. Appl. Cryst.の発刊に際して

▪ Abstract Our understanding of the evolution of organic molecules, and their voyage from molecular clouds to the early solar system and Earth, has changed dramatically. Incorporating recent observ...

/pdf/organic-molecules-in-the-interstellar-medium-comets-and-14nzw41xt5.pdf

Organic Molecules in the Interstellar Medium, Comets, and Meteorites: A Voyage from Dark Clouds to the Early Earth

Stellar nucleosynthesis of heavy elements, followed by their subsequent release into the interstellar medium, enables the formation of stable carbon compounds in both gas and solid phases. Spectroscopic astronomical observations provide evidence that the same chemical pathways are widespread both in the Milky Way and in external galaxies. The physical and chemical conditions—including density, temperature, ultraviolet radiation and energetic particle flux—determine reaction pathways and the complexity of organic molecules in different space environments. Most of the organic carbon in space is in the form of poorly-defined macromolecular networks. Furthermore, it is also unknown how interstellar material evolves during the collapse of molecular clouds to form stars and planets. Meteorites provide important constraints for the formation of our Solar System and the origin of life. Organic carbon, though only a trace element in these extraterrestrial rock fragments, can be investigated in great detail with sensitive laboratory methods. Such studies have revealed that many molecules which are essential in terrestrial biochemistry are present in meteorites. To understand if those compounds necessarily had any implications for the origin of life on Earth is the objective of several current and future space missions. However, to address questions such as how simple organic molecules assembled into complex structures like membranes and cells, requires interdisciplinary collaborations involving various scientific disciplines. Introduction Life in the Universe is the consequence of the increasing complexity of chemical pathways which led to stable carbon compounds assembling into cells and higher organisms.

/pdf/a-voyage-from-dark-clouds-to-the-early-earth-hw01qkx5z0.pdf

A voyage from dark clouds to the early Earth

Polyhedral oligomeric silsesquioxanes (POSS) thermal degradation

Highly fluorescent crystalline carbon nanoparticles (CNPs) have been synthesized by one step microwave irradiation of sucrose with phosphoric acid at 100 W for 3 min 40 s. This method is very simple, rapid and economical and hence can be used for large scale applications. The average particle sizes are 3 to 10 nm and they emit bright green fluorescence under the irradiation of UV-light. Therefore, the particles can be used as a unique material for bioimaging as well as drug delivery. To further increase the fluorescence property of the synthetic carbon nanoparticles we simply functionalized them by using different organic dyes, such as fluorescein, rhodamine B and α-naphthylamine; the maximum fluorescence intensity was observed for the particles functionalized with fluorescein. It is very interesting to note that all of those compounds show maximum fluorescence intensity at 225 nm excitation wavelength and for any excitation wavelength the peak positions are exactly same the position as that of CNPs itself, which is completely different from the individual precursors (dyes). All of the above compounds, including CNPs, have also been successfully introduced into the erythrocyte enriched fraction of healthy human blood cells with minimum cytotoxicity.

Synthesis, functionalization and bioimaging applications of highly fluorescent carbon nanoparticles

Carbon nanoparticles from laser pyrolysis

Infrared Laser Pyrolysis (IRLP) of gaseous molecules is a versatile method of synthesising a wide variety of nanopowders. The synthesis mechanism is based on conden- sation of heated gaseous precursors. This is the same mecha- nism as postulated for carbon dust formation in the envelopes of evolved C-rich stars. An advantage of this technique, in con- trast with furnace- or plasma-heated gas phase techniques, is its well-defined reaction zone and its infrared heating process. Using hydrocarbon molecules C2H4 or C4H6 as precursors, a series of carbon-based nanoparticles have been obtained in syn- thesis conditions corresponding to a variety of reaction temper- atures. The nanoparticles were characterised by Transmission Electron Microscopy (TEM) and infrared (IR) spectrometry. Both IR spectrum and molecular organisation appear to depend on the synthesis conditions: the lower the reaction temperature, the stronger the amorphous character and the more intense the IR bands. When present, IR bands are essentially due to aro- matic CC and CH groups. Our experimental results are com- pared with results reported on other carbonaceous compounds and with astronomical observations.

http://aa.springer.de/papers/8330003/2301127.pdf

Aymeric Galvez

Papers

Carbon nanoparticles from laser pyrolysis

Nanoparticles produced by Laser Pyrolysis of hydrocarbons: analogy with carbon cosmic dust

Optical properties of synthetic carbon nanoparticles as model of cosmic dust.