Hiroo Inokuchi

Effects of Pressure and Shear Stress on the Absorption Spectra of Thin Films of Pentacene

The absorption spectra in an oriented film of pentacene have been studied up to 10 GPa under hydrostatic conditions. The absorption bands of this hydrocarbon rapidly shifted to a longer wavelength region. The Davydov splitting of the 0-0 band in the oriented film abruptly increased with increasing pressure up to 1.2 GPa. However, this splitting disappeared at around 1.5 GPa. The absorption spectrum at this pressure is similar to that of the amorphous film. The molecular arrangements in the oriented film of pentacene changed to the amorphous state at around 1.5 GPa. When the pressure was increased further, the absorption peaks disappeared at pressures greater than 6.6 GPa. When the pressure is reduced from 10 GPa to the ambient pressures, we cannot find the original absorption spectra of the oriented film of pentacene. The irreversible optical property arises from the solid-phase reaction at higher pressures. We have observed in situ shear stress effects on the oriented film of pentacene in the sapphire-anvil cell under the microscope. After the pressure is increased up to 2 GPa, one sapphire-anvil is rotated by applied force to generate shear stress at this pressure. The color of the thin film changed remarkably from blue to yellow at the outer part on the anvil, but the color at the center was blue, insensitive to shear stress. The absorption intensity of the visible bands sharply decreased, and the width vastly broadened in the outer part. The amorphization of the oriented film is accelerated under shear deformation. On the other hand, the intensity of the absorption band below 400 nm increased in the outer part. After shear stress was reduced, the original spectrum of pentacene did not recover completely. The conjugated system in pentacene is partly broken by shear stress. Thus, the solid-phase reaction is also induced by shear stress for the thin film.

Raman Spectroscopic Study of Bis(Diphenylglyoximato)Metal Complexes Under High Pressure

Raman spectra of bis(diphenylglyoximato)metal complexes M(dpg)2 (M = Pt and Ni) under high pressure have been studied. The C = N stretching bands remarkably moved with increasing pressure. The relationship between the Raman shift and pressure is almost linear. The rates of increase in the Raman shift with pressure were determined. The platinum complex was more sensitive to pressure than the nickel complex, which is consistent with the pressure dependence of absorption spectra. The shear stress effect applied on the Pt(dpg)2 thin film was quantitatively estimated by using the relationship between the Raman shift and pressure.

Shear Stress Effect on the Absorption Spectra of Organic Thin Films Under High Pressure

The effects of shear stress on the absorption spectra of a thin film of one-dimensional bis(diphenylglyoximato)platinum(II), Pt(dpg)2 have been studied under high pressure. The color of the thin film turns from red-brown at ambient pressure to green at 0.4 GPa. Then, one sapphire anvil is rotated by applied force in order to generate shear stress at 0.4 GPa. The color of the thin film at the outer part on the anvil changes remarkably from green to yellow, but the color at the center is green. The absorption spectra of Pt(dpg)2 have simultaneously been measured under shear deformation and non-hydrostatic conditions. The absorption intensity of the visible band decreases sharply at outer part, and this absorption peak abruptly shifts to the near-infrared region. The powder x-ray diffraction profiles of the thin film of Pt(dpg)2 at center and outer parts have been studied under shear deformation. The 110 and 200 lines at outer part markedly shift to the lower d-value region. In contrast, both diffraction lines at the center part are insensitive to shear stress. This behavior corresponds to the shift of the absorption band at outer part.

Rare gas storage and chemical reaction using nanospace in C60 lattice

We demonstrated that rare gas (RG) occluded in the C 60 lattice has a chemical interaction with C 60 . In order to evaluate the interaction between RG and C 60 , we calculated the electronic state of C 60 (RG) n (n = 1,2,3) crystals. RG atoms in C 60 (RG) (RG = He, Ne, Ar) are neutral, whereas those in C 60 Kr and C 60 Xe have positive Mulliken charges of 0.99 and 1.04, respectively. For C 60 (RG) 2 and C 60 (RG) 3 , a slightly positive charge of 0.02 appeared on Ar atom in C 60 Ar 2 and C 60 Ar 3 . The chemical reaction such as a hydrogenation of CO to CH 4 was found to occur in the nanospace of C 60 -sodium-hydrogen.

Organic Semiconductors and Conductors: Start of Research in Japan

I report why and how I became engaged in the study of organic semiconductors. My first step (1947) in the investigation of organic semiconductors was the measurement of electrical resistance of powdered graphite and carbon materials. Through this observation I accepted the property that carbon particles certainly conduct electric current. I noticed that functional groups bound to the edges of polycyclics in graphite do not cause swelling. I hit upon an idea that polycyclic aromatic compounds with molecular structures similar to fragments of graphite might be electrically conductive. Then, I started measuring the electrical resistance of violanthrone and hence found semiconductive behavior in organic solids (1954). Further I present my encounter with charge-transfer type organic semiconductors.

Characteristic interactions of gases in solid carbon nanotubes

The hydrogen desorption peak for NT appears at 820K, which is lower than C60. The desorption peak of nitrogen appears at around 500K for C60, while NT does not have significant desorption above 300K. Carbon monoxide shows the several desorption processes both for C60 and NT below 400K. The weak desorption peaks appear at around 500K and 750K for C60, and above 700K for NT. Van der Waals and chemical interactions depend on the carbon network and the lattice/site.

Three Component Organic Semiconductors, Conductors and Superconductors

In the 1940s, almost 50 years ago, phthalocyanines, several kinds of dyestuffs such as cyanines and polycyclic aromatic compounds were major objects of study, and the quantitative investigation of electrical conductivity of organic compounds was started. We started to observe the electrical conduction of polycyclic aromatic compounds in 1947. At the beginning of these works, we used violanthrone, isoviolanthrone and pyranthrone as examples of those polycyclics. [1] From the temperature dependency of conductivity measurements of the polycyclic aromatic series and also from their photoconductive characters, it was found that their electronic properties appeared to be semiconductive. From the accumulation of experimental results on the semiconductive character of this series, in 1954 we presented a paper to the Bulletin of the Chemical Society of Japan entitled Organic Semiconductors. [2] In the same year [3], we reported a conductive organic complex, the ‘perylene-bromine complex’, having only resistivity value of 8Ω cm.