Solid State Phenomena Vols. 121-123

Abstract: A new electron beam radiation method was developed to prepare spinel-type nanocrystalline ZnFe2O4 at room temperature and ambient pressure, without any kind of catalysts. The structure, morphology and size were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM), infrared spectroscopy (IR). The obtained Nanocrystalline ZnFe2O4 particles have Spinel structure, spherical shape morphology and a mean particle size distribution of 20 and 40 nm.

Abstract: Laser irradiated carbon nanotubes in vacuum can emit dazzling yellow light due to the laser heating effect. We investigated the phonon frequency shifts of as irradiated carbon nanotube bundles by Raman spectroscopy under ultraviolet laser illumination (325 nm, 2.4 mW), the G band peak position was found to shift 50 cm-1 to lower wave number. By considering the temperature coefficient of the G band shift, the local temperature of the illuminated spot was predicted to be nearly 2000K. This temperature had a linear relationship with the incident laser power, and also was greatly influenced by the pressure of the vacuum chamber. The photoluminescence of the CNT bundle was also studied, which exhibits an oscillation of 0.1 eV, a possible origin of the oscillation was discussed.

Abstract: A series of silica supported Co-Re catalysts was prepared and used as catalysts for the synthesis of single-walled carbon nanotubes (SWNT) by carbon monoxide disproportionation at 750 – 950 °C. The characterization of catalysts suggests that good quality of SWNT was obtained from partially reduced and completely reduced cobalt-rhenium oxide. The carbon products were characterized by Raman spectroscopy, temperature programmed oxidation (TPO) and transmission electron microscope (TEM). The effects of reaction parameters such as molar ratio of Co to Re, reduction temperature, and reaction temperature were investigated. It was found the the synergism of Co and Re in the catalytic production of SWNT leads to high selectivity of SWNT.

Abstract: Co-silica nanotubes were prepared with nanofibers of [Co(NH3)6](HCO3)(CO3)·2H2O as templates. The yield and morphology of Co-silica nanotubes were influenced by the pH value of the ammonia solution, the concentration of the Co salt solution as well as the rate of ethanol addition. The optimized sample contains 100% nanotubes with 150 – 300 nm in diameter and up to 30 -m in length.

Abstract: With a suitable growth condition using CVD method, single crystal ZnO nanorods grow on the well-defined bounded facets of the random shape ZnSe grains using Zn and Se powders without any metal catalyst. To our best knowledge, there is no report in growing ZnO nanostructures on in-situ synthesized ZnSe. The growth direction of ZnSe nanorods on a facet of a ZnSe grain is quiet uniform. The growth mechanism of the nanostructure will be discussed. Meanwhile, the photoluminescence of the nanostructures will be investigated.

Abstract: A novel technique has recently been presented for depositing metal layers onto a SAM. This is demonstrated here for Pd and Pt deposits on a mercaptopyridine (4-PyS) SAM. The SAMcovered Au(111) electrode is immersed into the metal-ion-containing solution without potential control. As a result, metal ions, e.g., Pd(II) (respectively Pt(II)) adsorb on the surface by forming a complex with the pyridine species. Subsequently, the electrode is transferred to a metal-ion-free solution, where the adsorbed metal ions are reduced electrochemically to its zero-valent state. Upon reduction, monoatomic high metal islands were observed in STM. Angle resolved XPS measurements show unequivocally that the reduced metal resides on top of the SAM.

Abstract: With scanning tunneling microscopy (STM), the intramolecular conformational and intermolecular ordering aspects have been investigated of a variety of organic molecules physisorbed at the liquid-solid interface. By balancing the interplay between intramolecular and intermolecular interactions (hydrogen bonding), leading to control of the molecular conformation, foldamers were created which order into well-defined two-dimensional crystals. The nature of the hydrogen bonding groups in conjugated oligomers leads to the formation of infinite stacks and cyclic multimers, expressing the chiral nature of the molecules.

Abstract: Organic molecular beam deposition (OMBD) is used for co-evaporation of copper phthalocyanine (CuPc) and C60 to form mixed films. Although pure single layers are crystalline, mixing leads to amorphous films in most cases, although phase segregation occurs for high concentrations of C60. An underlying CuPc single layer suppresses the segregation and leads to a homogeneous CuPc/C60 mixed film for all layer compositions. These effects are exploited in photovoltaic (PV) devices, where new architectures to improve device performance are investigated. Mixing the CuPc and C60 improves device performance, with the maximum efficiency (ηp = 1.17%) reached for devices containing 75% CuPc in the mixed layer, surrounded by pure layers at the electrode interfaces.