Clay-fulleropyrrolidine nanocomposites

In this work, we describe the insertion of a water-soluble bisadduct fulleropyrrolidine derivative into the interlayer space of three layered smectite clays. The composites were characterized by a combination of powder X-ray diffraction, transmission electron microscopy, X-ray photoemission and FTIR spectroscopies, and laser flash photolysis measurements. The experiments, complemented by computer simulations, give insight into the formation process, structural details, and properties of the fullerene/clay nanocomposites. The reported composite materials constitute a new hybrid system, where C-60 differs from its crystals or its solutions, and open new perspectives for the design and construction of novel C-60-based organic/clay hybrid materials.</p

Carbon Nanotubes Encapsulating Superconducting Single-Crystalline Tin Nanowires

Superconducting low dimensional systems are the natural choice for fast and sensitive infrared detection, because of their quantum nature and the low-noise, cryogenic operation environment. On the other hand, monochromatic and coherent electron beams, emitted from superconductors and carbon-based nanostructured materials, respectively, are significant for the development of electron optical systems such as electron microscopes and electron-beam nanofabrication systems. Here we describe for the first time a simple method which yields carbon nanotubes encapsulating single crystalline superconducting tin nanowires by employing the catalytic chemical vapor deposition method over solid tin dioxide. The superconducting tin nanowires, with diameters 15-35 nm, are covered with well-graphitized carbon walls and show, due to their reduced diameters, a critical magnetic field (Hc) more than 30 times higher than the value of bulk metallic tin.

Carbon Nanotubes Encapsulating Superconducting Single-Crystalline Tin Nanowires. Nano Lett

ABSTRACT Superconducting low dimensional systems are the natural choice for fast and sensitive infrared detection, because of their quantum nature and the low-noise, cryogenic operation environment. On the other hand, monochromatic and coherent electron beams, emitted from superconductors and carbon-based nanostructured materials, respectively, are significant for the development of electron optical systems such as electron microscopes and electron-beam nanofabrication systems. Here we describe for the first time a simple method which yields carbon nanotubes encapsulating single crystalline superconducting tin nanowires by employing the catalytic chemical vapor deposition method over solid tin dioxide. The superconducting tin nanowires, with diameters 15−35 nm, are covered with well-graphitized carbon walls and show, due to their reduced diameters, a critical magnetic field (H c ) more than 30 times higher than the value of bulk metallic tin. The hot-electron phenomena in low-dimensional superconducting systems are of fundamental importance for high energy resolution bolometers. 1 Photon absorption in a superconducting detector creates an avalanche electron charge, 2 or 3 orders of magnitude higher than that in a semiconductor for the same photon energy. This results in an enhanced resolution in energy-resolving devices, such as superconducting tunnel junctions, 2 and extends the range of detectable energies

XRD, SAXS and PALS investigations of three different polymers reinforced with tetraoctylammonium exchanged montmorillonite

Byly připraveny tři rozdílné polymery s použitím jílu povrchově modifikovaného tetraoctylammoniem (4C8). Disperze jílových silikátových vrstev byla studována rentgenovou difrakcí (XRD) a maloúhlovým rozptylem (SAXS). Rozměry dutin byly měřeny pomocí spektroskopie doby života anihilace pozitronů (PALS). Rozptylové metody potvrdily rozvrat organizace všech polymerních lamel po přidání organojílu a vytvoření částečně mezikalcinačních systémů pro polyamidy a polycaprolactiny. Přitomnost organojílu v polymeru zvýšilo dolní hranici průměrné doby života pozitronu T3 polyamidu a snížilo horní hranici T3 pro polycaprolacton a polyethylen.Three different polymer nanocomposites were prepared using clay modified with tetraoctylammonium (4C8) surfactant. The dispersion of clay silicate layers were studied using X-ray diffraction (XRD) and small angle scattering (SAXS). Free volume cavity sizes were studied with positron annihilation lifetime spectroscopy (PALS). Scattering methods confirmed disruption of all polymer lamellae organization upon organoclay addition and the creation of partially intercalated systems for polyamide and polycaprolactone. Presence of the organoclay in the polymers enlarge the lower value of average positronium lifetime T3 of polyamide and reduce the higher value of T3 for the polycaprolactone and polyethylene

Formamide-Based Post-impact Thermal Prebiotic Synthesis in Simulated Craters: Intermediates, Products and Mechanism

Influx of matter from impacting meteoroids and hydrothermal crater weathering are important factors modifying the rock and mineral inventory of young planets undergoing heavy bombardment. These processes may have influenced not only the geochemical environment of, e.g., early Mars and other planets, but also the peculiar prebiotic chemistry on early Earth. Here, we present a synergistic experimental and computational investigation of the intermediates of chemical reactions of the formamide-based synthesis of canonical and non-canonical nucleobases by thermochemistry in hot hydrothermal crater environments. We put our findings into context with previously investigated plasma-initiated synthesis occuring directly during impact. Both processes result into the formation of all canonical nucleobases, hypoxanthine, purine, and into the onset of the simplest amino acid glycine. Furthermore, it turns out that radical species such as CN and H play a key role in the plasma-assisted impact chemistry. However, post-impact thermochemistry is essential for the origin of formamidine and 2-aminoacetonitrile, intermediate species detected in this study by means of FTIR spectroscopy

Clay-fulleropyrrolidine nanocomposites

In this work, we describe the insertion of a water-soluble bisadduct fulleropyrrolidine derivative into the interlayer space of three layered smectite clays. The composites were characterized by a combination of powder X-ray diffraction, transmission electron microscopy, X-ray photoemission and FTIR spectroscopies, and laser flash photolysis measurements. The experiments, complemented by computer simulations, give insight into the formation process, structural details, and properties of the fullerene/clay nanocomposites. The reported composite materials constitute a new hybrid system, where C-60 differs from its crystals or its solutions, and open new perspectives for the design and construction of novel C-60-based organic/clay hybrid materials