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The elucidation of a molecular structure of the active sites (i.e., the Co−Mo−S phase) of Co−Mo hydrodesulfurization catalysts has received extensive attention. In the present study, we unambiguously determined, for the first time, the NO adsorption behavior and magnetic property of the Co−Mo−S phase by preparing unique Co−Mo/Al2O3 catalysts (CVD−Co/MoS2/Al2O3), in which all the Co atoms are present as the Co−Mo−S phase. The catalysts were characterized by NO adsorption (pulse technique and FTIR), Co K-edge XANES, and the magnetic susceptibility and effective magnetic moment of Co. Nitric oxide molecules were adsorbed on 33% of the Co atoms in CVD−Co/MoS2/Al2O3 after sulfidation and on only half of the Co atoms even after an H2-treatment of the sulfided catalyst at 573−673 K. The Co atoms in CVD−Co/MoS2/Al2O3 exclusively exhibited an antiferromagnetic property, indicating that even-numbered Co atoms are interacting with each other in the Co−Mo−S phase. A Co−Mo/Al2O3 catalyst, prepared by a conventional impregnation technique, was composed of the antiferromagnetic Co sulfide species as observed in CVD−Co/MoS2/Al2O3 in addition to Co9S8. On the basis of the NO adsorption behavior and magnetic property, it is empirically proposed that the structure of the Co−Mo−S phase is represented as a Co sulfide dinuclear cluster located on the edge of MoS2 particles. The magnetic property of Co/Al2O3 sulfide catalysts depended on the preparation method.

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The electric-field distribution in Au/Zn-phthalocyanine(ZnPc)/3,4,9,10-perylene-tetracarboxylbis-benzimidazole(PTCBI)/In/Al heterojunction solar cells is studied by electroabsorption and photocurrent measurements. In the PTCBI surface region near the PTCBI/In interface, a large anomalous electric field exists which is nearly bias independent and does not contribute to the photocurrent generation. This anomalous electric field exists only for the PTCBI-film thickness ⩾35 nm. The electric fields in the bulk of the PTCBI and ZnPc layers are responsible for the photocurrent generation. The bulk electric field in the PTCBI layer changes its sign at a forward bias, Vbias, of 0.3 V, while that in the ZnPc layer disappears for Vbias⩾0.5 V. The latter may indicate that holes are hardly trapped in the ZnPc layer.

Spin-dependent recombination of photoinduced carriers in H 2 -phthalocyanine (H 2 Pc͒/C 60 heterojunctions is studied by electrically detected electron-spin resonance ͑EDESR͒ spectroscopy. The EDESR spectrum of the H 2 Pc/C 60 consists of two components A and B, the g values of which are 2.0018Ϯ0.0002 and 2.0010Ϯ0.0002, respectively. The two components are attributed to exchange-coupled localized electron-hole pairs trapped at different types of recombination centers. Component A has spin-flip satellites due to an interaction between the electron ͑or hole͒ spin, and its surrounding nuclear spins of protons which belong to the H 2 Pc rings. From the satellite intensity, the distance between the electron ͑or hole͒ and the protons is estimated to be 4.33Ϯ0.25 Å, indicating that the localized pairs for the component A locate close to the H 2 Pc rings. The spin dynamics of the localized pairs for the component A is studied by a microwave recovery experiment, in which the time dependence of the EDESR signal intensity is measured after turning the resonant microwave on and off. A theoretical model of the spin-dependent recombination of the exchange-coupled electron-hole pair is proposed with which the experimental results of the microwave recovery are explained. By a theoretical analysis, it is found that Rտ1ϫ10 6 s Ϫ1 and DϩW sl ϭ6.2 (Ϯ0.8)ϫ10 4 s Ϫ1 for component A at room temperature, where R is the recombination rate of the localized pair in the S z ϭ0 triplet sublevel, and D and W sl are the dissociation and the spin-lattice relaxation rates, respectively, of the pairs in the triplet sublevels. The photocurrent I 2 that is caused by the dissociation of the localized pairs for component A is about 5% of the total photocurrent.