Synthesis of a Novel Family of Polysilsesquioxanes Having Oligothiophenes with Well-Defined Structures

Our recent results on the synthesis and properties of a novel family of polysilsesquioxanes having oligothiophenes were reviewed. The polymers anchored on SiO2 or ITO substrates showed excellent mechanical hardness due to the formation of a three-dimensional siloxane network structure and chemical linkage between polymer and the surface of metal-oxide substrates. Optical, electrochemical, and electrical properties of polymers were also investigated

A history of mild shocks experienced by the regolith particles on hydrated asteroid Ryugu

Micrometeorites, a possible major source of Earth’s water, are thought to form from explosive dispersal of hydrated chondritic materials during impact events on their parental asteroids. However, this provenance and formation mechanism have yet to be directly confirmed using asteroid returned samples. Here, we report evidence of mild shock metamorphism in the surface particles of asteroid Ryugu based on electron microscopy. All particles are dominated by phyllosilicates but lack dehydration textures, which are indicative of shock-heating temperatures below ~500 °C. Microfault-like textures associated with extensively shock-deformed framboidal magnetites and a high-pressure polymorph of Fe–Cr–sulfide have been identified. These findings indicate that the average peak pressure was -2 GPa. The vast majority of ejecta formed during impact on Ryugu-like asteroids would be hydrated materials, larger than a millimetre, originating far from the impact point. These characteristics are inconsistent with current micrometeorite production models, and consequently, a new formation mechanism is required

Oxygen isotope evidence from Ryugu samples for early water delivery to Earth by CI chondrites

The delivery of water to the inner Solar System, including Earth, is still a debated topic. A preferential role for hydrated asteroids in this process is supported by isotopic measurements. Carbonaceous chondrite (CC) meteorites represent our main source of information about these volatile-rich asteroids. However, the destruction of weaker materials during atmospheric entry creates a bias in our CC data. The return of surface materials from the C-type asteroid 162173 Ryugu by the Hayabusa2 spacecraft provides a unique opportunity to study high-porosity, low-density, primitive materials, unrepresented in the meteorite record. We measured the bulk oxygen isotope composition from four Ryugu particles and show that they most closely resemble the rare CI (CC Ivuna-type) chondrites, but with some differences that we attribute to the terrestrial contamination of the CI meteorites. We suggest that CI-related material is widespread among carbonaceous asteroids and a more important source of Earth’s water and other volatiles than its limited presence in our meteoritic collection indicates

A pristine record of outer Solar System materials from asteroid Ryugu’s returned sample

Volatile and organic-rich C-type asteroids may have been one of the main sources of Earth’s water. Our best insight into their chemistry is currently provided by carbonaceous chondritic meteorites, but the meteorite record is biased: only the strongest types survive atmospheric entry and are then modified by interaction with the terrestrial environment. Here we present the results of a detailed bulk and microanalytical study of pristine Ryugu particles, brought to Earth by the Hayabusa2 spacecraft. Ryugu particles display a close compositional match with the chemically unfractionated, but aqueously altered, CI (Ivuna-type) chondrites, which are widely used as a proxy for the bulk Solar System composition. The sample shows an intricate spatial relationship between aliphatic-rich organics and phyllosilicates and indicates maximum temperatures of ~30 °C during aqueous alteration. We find that heavy hydrogen and nitrogen abundances are consistent with an outer Solar System origin. Ryugu particles are the most uncontaminated and unfractionated extraterrestrial materials studied so far, and provide the best available match to the bulk Solar System composition

Optical absorption spectrum of pentacene cation radicals measured by charge-modulation spectroscopy

Charge-modulation spectroscopy was applied to vacuum-sublimed films of pentacene in the metal-insulator-semiconductor configuration with Parylene-C or cross-linked polymer as insulator. The spectrum exhibited several peaks in the wavelength range of 300-800 nm. The signal in the visible was ascribed to the field-modulation effect of a neutral pentacene film, while the three broad peaks in the UV exhibited field and frequency dependences different from those in the visible and were ascribed to the optical absorption due to a monocation radical of pentacene. This assignment was supported by the calculation reported earlier on the basis of the time-dependent density functional theory

Periodic mesoporous organosilica materials incorporating various organic functional groups: Synthesis, structural characterization, and morphology

We describe the syntheses and characterization of a series of periodic mesoporous organosilica (PMO) materials containing various organic functional groups prepared using the direct synthesis method under basic conditions. This synthetic method allows the production of mesoporous organosilicas that have large surface areas and contain several different functional groups, such as a bridged amino, vinyl, ethyl, glycidoxypropyl, and cyanopropyl units. Moreover, the type of organosilane used as a co-precursor has a great influence on the final particle shape and modulates the overall properties of the resulting materials. By changing the precursor type, along with its concentration, the particles can adopt various morphologies, including rod-shaped and wormlike particles that have different degrees of bending. We propose a plausible mechanism to explain the formation of these shapes. We have used X-ray diffraction (XRD) patterns, nitrogen sorption properties, scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), and 13C and 29S magic angle spinning (MAS) NMR spectroscopy to characterize the structures and organic functionalities present in the resulting functionalized PMO materials. © 2005 American Chemical Society