Deposition of Ni<Subscript> 13</Subscript> and Cu<Subscript> 13</Subscript> clusters on Ni(111) and Cu(111) surfaces

The soft deposition of Ni₁₃ and Cu₁₃ clusters on Ni(111) and Cu(111) surfaces is studied by means of constant-energy molecular-dynamics simulations. The atomic interactions are described by the Embedded Atom Method. It is shown that the shape of the nickel clusters deposited on Cu(111) surfaces remains rather intact, while the copper clusters impacting on Ni(111) surfaces collapse forming double and triple layered products. Furthermore, it is found that for an impact energy of 0.5 eV/atom the structures of all investigated clusters show the lowest similarity to the original structures, except for the case of nickel clusters deposited on a Cu(111) surface. Finally, it is demonstrated that when cluster and substrate are of different materials, it is possible to control whether the deposition results in largely intact clusters on the substrate or in a spreading of the clusters. This separation into hard and soft clusters can be related to the relative cohesive energy of the crystalline materials.     

Silver oligomer and single fullerene electronic properties revealed by a scanning tunnelling microscope

Clusters on surfaces have been investigated with low-temperature scanning tunnelling microscopy and spectroscopy. Constant current spectra acquired on Ag oligomers and one-dimensional chains on a Ag(111) reveal a single resonance peak whose energy shifts towards the Fermi level with increasing cluster size. Next, controlled and reproducible contact between a STM tip and a C₆₀ molecule adsorbed on Cu(100) is reported. The transition from tunnelling to contact is discussed in terms of local heating of the tip-molecule junction.     

Optical and photoelectron spectroscopic studies of alkyl-passivated silicon nanoparticles

We have performed the optical and photoelectron spectroscopic studies of alkyl-passivated Si nanoparticles synthesized by a solution route. The alkyl-passivated Si nanoparticle with mean diameter less than about 2 nm exhibits a strong ultraviolet-blue photoluminescence. Furthermore, we have directly investigated their electronic structures in the vicinity of Fermi level by means of valence-band photoemission measurements using synchrotron radiation. From these results, the detailed optical properties and electronic structures of alkyl-passivated Si nanoparticles are discussed.     

Enhanced cycling properties of transition metal molybdates, Li x M2(MoO4)3 {0?≤ x

K. M. Begam  M. S. Michael  S. R. S. Prabaharan 《Ionics》2007,13(6):467-471

Anisotropic ferromagnetism induced in rutile single crystals by Co implantation

The magnetic and electrical properties of Co-implanted single crystalline TiO₂ rutile are presented. For fluences of the order of 10¹⁷ cm^-2 and implantation energy of 150 keV the maximum atomic concentration of cobalt is 13 at% at a depth of 65 nm from the surface. The as implanted single crystals exhibit superparamagnetic behaviour attributed to the formation of nanosized cobalt clusters. After annealing at 1073 K an anisotropic ferromagnetic behaviour emerges with the easy magnetization axis lying in the (001) plane of rutile. The ferromagnetic behaviour is associated with oriented cobalt aggregates. Electrical conductivity of the implanted samples annealed in vacuum also exhibits anisotropic behaviour at low temperatures, but no magnetoresistive effects were detected.     

Orbital contribution to the magnetic properties of nanowires: is the orbital polarization ansatz justified?

We show that considerable orbital magnetic moments and magneto-crystalline anisotropy energies are obtained for a Fe monatomic wire described in a tight-binding method with intra-atomic electronic interactions treated in a full Hartree Fock (HF) decoupling scheme. Even though the use of the orbital polarization ansatz with simplified Hamiltonians leads to fairly good results when the spin magnetization is saturated this is not the case of unsaturated systems. We conclude that the full HF scheme is necessary to investigate low dimensional systems.     

Enhanced Efficiency of Polymer Light-Emitting Diodes by Dispersing Dehydrated Nanotube Titanic Acid in the Hole-buffer Layer

Efficiency of polymer light-emitting diodes (PLEDs) with poly(2-methoxy-5-(2-ethyl hexyloxy)-p-phenylene vinylene) (MEH-PPV) as an emitting layer was improved if a dehydrated nanotubed titanic acid (DNTA) doped hole-buffer layer polyethylene dioxythiophene (PEDOT) was used. Photoluminescence (PL) and Raman spectra indicated a stronger interaction between DNTA and sulfur atom in thiophene of PEDOT, which suppresses the chemical interaction between vinylene of MEH-PPV and thiophene of PEDOT. The interaction decreases the defect states in an interface region to result in enhancement in device efficiency, even though the hole transporting ability of PEDOT was decreased.     

Temperature dependent magnetic spin and orbital moments of mass-filtered cobalt clusters on Au(111)

Mass-filtered cobalt clusters with a size of 8 nm have been deposited in-situ under soft-landing conditions onto Au(111). The spin and orbital moments of the Co nanoparticles on a Au (111) single crystal have been investigated as a function of the temperature using the element-specific method of X-ray magnetic circular dichroism in photoabsorption. The results hint at an temperature-dependent spin-reorientation transition which is discussed with respect to different contribution to the magnetic anisotropy. Furthermore, by means of an in-situ oxidation experiment, the influence of an exposure to oxygen on the properties of the cobalt clusters has been investigated.     

简单的方法制备°-Fe2O3纳米粒子及其磁性质和电化学性质

报道了制备磁性Fe2O3纳米粒子的一种简单易行的方法．利用部分还原共沉淀法， 以Na2S2O4作为还原剂， 用FeCl3先制备出Fe2O3纳米微粒， 再在空气中直接煅烧， 成功地制备出粒径较均匀(约13 nm)的磁性Fe2O3微粒． 实验发现Na2S2O4在部分还原共沉淀法中起到了去氧剂兼还原剂的特殊作用．研究表明， 样品在室温下具有铁磁性， 其饱和磁化强度和矫顽力分别为70 emu/g和164 Oe； 产物具有好的电化学性质，在3.0?0.3 V(相对于金属锂)、0.2 mA/cm2时，样品的首次放电容量可达到933 mAh/g．同时还讨论了放电过程中金属锂与Fe2O3的反应机理．     

Three-dimensional photofabrication with femtosecond lasers for applications in photonics and biomedicine

A status report on rapidly advancing femtosecond laser technology, three-dimensional (3D) microstructuring by multiphoton illumination technique, is given. Taking its origin from multiphoton microscopy, this technique is now becoming an important microfabrication tool. In our work we apply near-infrared Ti:sapphire femtosecond laser pulses (at 800/780 nm) for 3D material processing. When tightly focused into the volume of a photosensitive material (or photoresist), they initiate 2PP process by, for example, transferring liquid into the solid state. This allows the fabrication of any computer generated 3D structure by direct laser “recording” into the volume of photosensitive material. 2PP of photosensitive materials irradiated by femtosecond laser pulses is now considered as enabling technology for the fabrication of 3D photonic crystals and photonic crystal templates. In particular, 2PP allows one to introduce defects at any desired locations, which is crucial for the practical applications. Recently, we studied possible applications of 2PP technique in biomedicine. 2PP is a very interesting technique for the fabrication of drug delivery systems, scaffolds for tissue engineering, and medical implants. These and other biomedical applications of 2PP will be reviewed.