Towards molecular-scale electronics and biomolecular self-assembly

This paper provides an overview of recent research developments in the field of nanoelectronics with organic materials such as carbon nanotubes and DNA-templated nanowires. Carbon nanotubes and gold electrodes are chemically functionalized in order to contact carbon nanotubes by self-assembly. The transport properties of these nanotubes are dominated by charging effects and display clear Coulomb blockade behaviour. A different approach towards nanoscale electronics is based on the molecular recognition properties of biomolecules such as DNA. As an example, DNA is stretched between electrodes using a molecular combing technique. A two-step metallization procedure leads to the formation of highly conductive gold nanowires.     

A comparative study on the interaction between tin(II) porphyrin and selected group 8B metals for potential application as reduction catalysts

We study the interaction between tin(II) porphyrin (SnPor) with platinum and non-precious Group 8B metals (iron, cobalt and nickel) by density functional theory and discuss the electronic properties of the resulting products. We also model the interaction of the resulting compounds with water where applicable. Our studies indicate that, SnPor-Ni possesses electronic properties similar to SnPor-Pt, suggesting that it may possess similar photocatalytic properties for reduction reactions, such as converting water to hydrogen gas.     

Metastability of gold-carbonyl cluster complexes, Au N(CO) M -

Smaller gold-cluster anions, typified by Au ₇ ^- , adsorb multiple CO molecules in a high-pressure, room-temperature flow-reactor, tending toward previously unknown saturation compositions, Au₇(CO) ₄ ^- . The weakness of the gold-carbonyl adsorption bond is evidenced indirectly by the high CO partial pressure required and more directly by the high probability of fragmentation in the field-free flight region of the reflectron-type time-of-flight mass spectrometer. The analysis of this metastability reveals that the actual distribution f_N,M of products Au₇(CO) _M ^- in the reactor may be highly non-statistical, e.g. with only even-M species present. Received 17 April 2001     

稀土对金属纳米粒子-介质复合薄膜(Ag-BaO)光电发射性能的增强

用真空蒸发沉积的方法制备了掺杂稀土的金属纳米粒子介质复合薄膜(Ag-BaO薄膜).与不掺杂稀土的Ag-BaO薄膜相比,其光电发射能力提高了近40%.透射电镜分析表明,掺杂稀土后,Ag-BaO薄膜中的Ag纳米粒子明显细化、球化、密度增大.这表明Ag纳米粒子的细化,使得其在光作用下,光电子更容易通过隧道效应穿过界面位垒逸出,导致光电发射能力增强     

Ag/AgCl纳米粒子的制备及其共振散射光谱研究

以AgCl纳米粒子作晶种,在柠檬酸三钠存在条件下,AgCl纳米粒子表面结合的银离子被光化学还原而获得Ag/AgCl复合纳米粒子。研究了Ag/AgCl纳米粒子的光谱特性,在310和590nm处产生二个共振散射峰,在400nm处产生一个吸收峰。     

Pulling-induced rupture of ligand-receptor bonds between a spherically shaped bionanoparticle and the support

Contacts of biological or biologically-inspired spherically shaped nanoparticles (e.g., virions or lipid nanoparticles used for intracellular RNA delivery) with a lipid membrane of cells are often mediated by multiple relatively weak ligand-receptor bonds. Such contacts can be studied at a supported lipid bilayer. The rupture of bonds can be scrutinized by using force spectroscopy. Bearing a supported lipid bilayer in mind, the author shows analytically that the corresponding dependence of the force on the nanoparticle displacement and the effect of the force on the bond-rupture activation energy are qualitatively different compared to what is predicted by the conventional Bell approximation.     

Epoxy/Silica Nanohybrids or Nanocomposites: Atomic Force Microscopy and X-ray Photoelectron Spectroscopy Investigation of the Processing–Structure–Property Relationships

The structural and morphological features influencing the glass transition temperature of epoxy/silica nanohybrid and nanocomposite materials containing 25–30 phr of nanoscale silica phases are discussed in this letter to answer the questions related to the processing–structure–property relationships. X-ray photoelectron spectroscopy and atomic force microscopy are used to study the surface chemical structure and morphology of epoxy/silica nanohybrids and nanocomposites. Nanohybrids are synthesized via in situ sol-gel process, while the respective nanocomposites are prepared by mechanical blending of preformed silica nanoparticles into epoxy resin. Differential scanning calorimetry is used to determine glass transition temperature of different materials. The surface analytical characterizations reveal that in situ sol-gel process is more suitable for producing organic–inorganic hybrid materials with superior glass transition temperature owing to the achievement of stronger interfacial compatibility and greater crosslink density. A number of other factors affecting glass transition temperature are explored and discussed with reference to surface chemistry, microstructure, and morphology of epoxy/silica nanohybrids and nanocomposites, respectively.     

The study of transition on NiFe2O4 nanoparticles prepared by co-precipitation/calcination

In this study, the NiFe₂O₄ nanoparticles have been prepared by co-precipitation and calcination process. Using a vibrating sample magnetometer (VSM), transmission electron microscopy (TEM), X-ray diffraction (XRD), energy dispersive spectrometer of X-ray (EDX), and X-ray photoelectron spectroscopy (XPS), the samples obtained by co-precipitation and then by further calcination have been analyzed. The experimental results show that the precursor synthesized by co-precipitation is the composite of both amorphous FeOOH and Ni(OH)₂, but has no amorphous NiFe₂O₄. The results of both EDX and XPS revealed that the FeOOH species is wrapped up by Ni(OH)₂ species. In the calcination process, the amorphous composite is dehydrated and transformed gradually into crystalline NiFe₂O₄ nanoparticles, with the metal ions diffusing. The reaction is different from the one used to prepare other ferrite (e.g., CoFe₂O₄, MnFe₂O₄, Fe₃O₄, etc.) nanoparticles directly by co-precipitation. With increasing calcination temperature, the NiFe₂O₄ grains grow and the magnetization is enhanced.     

Chemical synthesis and magnetic properties of HCP and FCC nickel nanoparticles

In this study, we successfully synthesized single-phase hexagonal closed packed (HCP) and face-centered cubic (FCC) nickel nanoparticles via reduction of nickel nitrate hexahydrate and nickel acetate tetrahydrate, respectively, in polyethylene glycol-200. Structural information of the as-synthesized nickel nanoparticles are studied by X-ray diffraction (XRD) as a function of the molar concentration of the nickel precursor. XRD results reveal that low concentrations of nickel precursor (0.005?M and below) favor the HCP, while high concentrations favor the mixture of HCP and FCC crystal structures. Particle size of HCP structure is found in the range of ～15?nm via transmission electron microscope analysis. Vibratory sample magnetometer is employed to study its magnetic behavior and the results reveal that FCC crystalline phase shows ferromagnetic nature with high saturation magnetization (M _s?～?39.6?emu?gm^?1) as compared to metastable HCP crystalline structure (M _s?～?2?emu?gm^?1). The surfactants bonding on the surface of nickel nanoparticles are studied.     

氮吸附法测定纳米粒子的比表面积实验

在纳米粒子的性能表征中,比表面积是一个非常重要的参数。本文研究了用氮吸附法测定纳米粒子比表面积的实验方法。