| 11. |
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| 12. |
- Nascimento, V. B., et al.
(author)
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Surface-Stabilized Nonferromagnetic Ordering of a Layered Ferromagnetic Manganite
- 2009
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In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 103:22, s. 227201-
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Journal article (peer-reviewed)abstract
- An outstanding question regarding the probing or possible device applications of correlated electronic materials (CEMs) with layered structure is the extent to which their bulk and surface properties differ or not. The broken translational symmetry at the surface can lead to distinct functionality due to the charge, lattice, orbital, and spin coupling. Here we report on the case of bilayered manganites with hole doping levels corresponding to bulk ferromagnetic order. We find that, although the hole doping level is measured to be the same as in the bulk, the surface layer is not ferromagnetic. Further, our low-energy electron diffraction and x-ray measurements show that there is a c-axis collapse in the outermost layer. Bulk theoretical calculations reveal that, even at fixed doping level, the relaxation of the Jahn-Teller distortion at the surface is consistent with the stabilization of an A-type antiferromagnetic state.
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| 13. |
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| 14. |
- Tian, Haining, et al.
(author)
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A triphenylamine dye model for the study of intramolecular energy transfer and charge transfer in dye-sensitized solar cells.
- 2008
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In: Advanced Functional Materials. - : Wiley. - 1616-301X .- 1616-3028. ; 18:21, s. 3461-3468
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Journal article (peer-reviewed)abstract
- A novel dye (2TPA-R), contg. two triphenylamine (TPA) units connected by a vinyl group and rhodanine-3-acetic acid as the electron acceptor, is designed and synthesized successfully to reveal the working principles of org. dye in dye-sensitized solar cells (DSSCs). 2TPA and TPA-R, which consist of two TPA units connected by vinyl and a TPA unit linked with rhodanine-3-acetic acid, resp., are also synthesized as refs. to study the intramol. energy transfer (EnT) and charge transfer (ICT) processes of 2TPA-R in CH2Cl2 soln. and on a TiO2 surface. The results suggest that the intramol. EnT and ICT processes show a pos. effect on the performance of DSSCs. However, the flexible structure and less-adsorbed amt. of dye on TiO2 may make it difficult to improve the efficiency of DSSCs. This study on intramol. EnT and ICT processes acts as a guide for the design and synthesis of efficient org. dyes in the future. [on SciFinder(R)]
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| 15. |
- Yao, Mingguang, et al.
(author)
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Raman signature to identify the structural transition of single-wall carbon nanotubes under high pressure
- 2008
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In: Physical Review B. Condensed Matter and Materials Physics. - : American Physical Society. - 1098-0121 .- 1550-235X. ; 78:20
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Journal article (peer-reviewed)abstract
- Raman spectra of single-walled carbon nanotubes (SWNTs) with diameters of 0.6–1.3 nm have been studied under high pressure. A “plateau” in the pressure dependence of the G-band frequencies was observed in all experiments, both with and without pressure transmission medium. Near the onset of the G-band plateau, the corresponding radial breathing mode (RBM) lines become very weak. A strong broadening of the full width at half maximum of the RBMs just before the onset of the G-band plateau suggests that a structural transition starts in the SWNTs. Raman spectra from SWNTs released from different pressures also indicate that a significant structural transition occurs during the G-band plateau process. Simulations of the structural changes and the corresponding Raman modes of a nanotube under compression show a behavior similar to the experimental observations. Based on the experimental results and the theoretical simulation, a detailed model is suggested for the structural transition of SWNTs, corresponding to the experimentally obtained Raman results in the high-pressure domain.
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| 16. |
- Zhang, Wei, et al.
(author)
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Synthesis and characterization of some new mononuclear ruthenium complexes containing 4-(un) substituted dipyridylpyrazole ligands
- 2008
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In: Polyhedron. - : Elsevier BV. - 0277-5387 .- 1873-3719. ; 27:4, s. 1168-1176
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Journal article (peer-reviewed)abstract
- A mononuclear ruthenium complex [Ru(bpy)(2)(bpp)](PF6) (1) and its halogenated and nitro derivatives [Ru(bpy)(2)(Xbpp)](PF6) (bpy = 2,2'-bipyridine; bpp = 3,5-bis(2-pyridyl)pyrazole; X = Cl, 2; X = Br, 3; X = I, 4; X = NO2, 5) have been synthesized and characterized by H-1 NMR, C-13 NMR, HRMS, elemental analysis. Complexes 2-5 have been further confirmed by X-ray diffraction. Their UV-Vis and emission spectroscopies, electrochemical measurements and acid-base properties are described. The results presented here reveal that the introduction of Cl, Br, I and NO2 groups to the coordinated bpp(-) ligand makes the absorption and emission maxima of the parent complex 1 blue-shifted, the oxidation potential of the Ru-II/Ru-III couple increased and the pK(a) value decreased obviously. In addition, significant quenching of the emission by these groups is also observed.
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