Takeshi Hanada

Metal and size effects on structures and photophysical properties of porphyrin-modified metal nanoclusters

Three-dimensional (3D) porphyrin monolayer protected metal nanoclusters (MPCs) have been prepared to examine the effects of metal (Au, Ag, Au–Ag alloy, Pd and Pt) and size (1–3 nm) on the structures and photophysical properties. The quenching rate constants of the porphyrin excited singlet state by the surfaces of mono-metal nanoclusters and gold nanoclusters with different diameters are virtually the same. In contrast, the quenching rate constant of the gold–silver alloy nanocluster is half that of the corresponding mono-metal clusters (i.e. Au or Ag). This reveals that interaction between the surface of the gold–silver alloy and the porphyrin excited singlet state is attenuated as compared wtih the mono-metal systems. Thus, porphyrin metal alloy nanoclusters are potential candidates as a new type of artificial photosynthetic materials and photocatalysts.

Organic Light-Emitting Diode with TiOPc Layer. A New Multifunctional Optoelectronic Device.

An organic light-emitting diode containing titanyl phthalocyanine (TiOPc) and tris-(8-hydroxy quinoline) aluminum (Alq3) layers has been fabricated. The device exhibits green emission from the Alq3 emissive layer under ambient conditions. Below the turn-on voltage, the green emission is instantaneously switched on by laser irradiation at 650 nm, indicating that the device can be used as a red-to-green light converter. Above the turn-on voltage, the green emission is greatly enhanced by laser irradiation, while the current-voltage characteristics are significantly modified. Amplification factors of the emission intensity as well as the current density upon laser irradiation are found to greatly depend on the TiOPc layer thickness. The TiOPc layer acts as a hole generation layer rather than as a buffer layer.

Development of a Process for Cleaning a TEM Column by Chemical Etching of Oxygen Radicals

Contamination deposition on a specimen during the irradiation of the electron beam in a TEM column interferes accurate elemental analysis and high-resolution imaging. Such specimen contaminations are mainly caused by the interactions of an electron beam with hydrocarbons existing in a high-vacuum TEM chamber introduced by high-vacuum pumping system, specimen damage, and leaks. Therefore, an effective process for the cleaning and removal of the contaminants in a TEM column has been desired

Structure of Multi-Walled and Single-Walled Carbon Nanotubes. EELS Study

Publisher Summary This chapter reviews several structural characterizations of carbon nanotubes (CNTs) with the cylindrical graphite from the viewpoint of transmission electron microscopy (TEM). Especially, electron energy loss spectroscopy (EELS) by using an energy-filtered TEM is applied to reveal the dependence of fine structure of EELS on the diameter and the anisotropic features of CNTs. Although CNTs showed similar EELS pattern in plasmon-loss and core-loss regions to graphite, SWCNT and fine MWCNT with a diameter less than 5 nm had different features. Furthermore, it has been found out that the angular dependent EELS along the direction normal to the longitudinal axis of CNT shows stronger contribution from π electrons than a electrons. It has been confirmed that the anisotropy of CNT exists in the structure and electronic property. Although it is scarcely able to obtain a lattice image of the graphitic structure from a single-walled CNT (SWCNT), whole the CNT should be aligned normal to the incident electrons without any inclination and bending. Therefore, it is difficult to detect the helicity in a CNT from the images. Some investigations have been devoted to the structures at the end and around the bends of CNTs. There could be the presence of pentagons or heptagons, but it is also not easy to distinguish the individual polygons by TEM.