Scientia Iranica
Volume:18 Issue: 6, 2011

We present a theoretical study of the differential conductance of a finite-length armchair single-wall carbon nanotube in the presence of electron–phonon interaction by employing a perturbative approach. It is shown that the nonlinear conductance measurement can be regarded as a novel method for detecting longitudinal optical phonon modes, which have non-negligible electron–phonon coupling in a proper applied bias range. Furthermore, it is found that at high temperatures, differential conductance depends on temperature, while this dependence is smeared out as temperature decreases.

The aim of this study was to investigate the thermal behavior of Mg-doped calcium phosphate compounds. Nanocrystalline HA and β-TCP mixtures containing different magnesium contents were synthesized via an alkoxide sol gel method. The ratio of (Ca+Mg)/P was kept constant at 1.67, and the Mg content ranged between 0 and 3 mol%. The influence of magnesium on the phase composition, chemical structure, thermal behavior and morphological characteristics of nanopowders was analyzed using X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR), Simultaneous Thermogravimetry and Differential Thermal Analysis (STA/DTA), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). Based on the results of this research, the presence of magnesium led to the formation of Mg-doped hydroxyapatite (Mg-HA) and Mg-doped tricalcium phosphate (β-TCMP) phases. The characteristic peaks of apatite structures have been identified in the FTIR spectra. It was found that both the presence of magnesium and low Ca/P ratio caused the formation of a biphasic mixture, even at 470 °C. In addition, the β-TCP to α-TCP transformation temperature increased due to the presence of magnesium ions. Morphological investigations showed that the synthesized powders were composed of nanoparticles, with sizes ranging from 40 to 100 nm.

Let G be a molecular graph. The Wiener indices of G are defined as the sum of the shortest paths between vertices of G. In this paper, the exact formulae for the Wiener indices of (Op(Q2.0(T)))−TU(3,0) are given.

Using poly(MAA-PEGMA)-coated superparamagnetic nanoparticles (PMNPs) as carrier, a rapid and sensitive immunoassay for quantitative determination of interleukin-6 (IL-6) has been developed for the first time. This protocol involved a sandwich format in which the IL-6 in samples was first captured by the primary monoclonal antibody (mAb) immobilized on the surface of PMNPs, and then recognized by the second monoclonal antibody labeled with horseradish peroxidase (HRP-mAb). The HRP-mAb dilution and immunoreaction time were examined and optimized. The linear range for IL-6 assay was 3.2–1000 pg mL−1, and the Limit Of Detection (LOD) was 1.0 pg mL−1. The developed immunoassay method showed high precision, high sensitivity, acceptable recovery and relatively good reliability, and could be used to detect serum IL-6 levels with consistent results in comparison with those obtained by the Enzyme-Linked Immunosorbent Assay (ELISA) method.

In this study, we present a biological method for synthesis of silver nanoparticles (AgNPs) using Streptomyces sp. ERI-3 cell-filtrate. AgNO3 solution (1 mM) was added to the cell-free culture supernatant and the mixture was incubated at 28 °C for 48 h in the dark in an orbital shaker. The AgNPs were characterized using UV–visible spectroscopy, X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM) and Scanning Electron Microscopy (SEM). The nanoparticles exhibited maximum absorbance at 430 nm in UV–Vis spectroscopy. The XRD spectrum exhibited 2⊖ values corresponding to the silver nanocrystals. TEM and SEM micrographs revealed the extracellular formation of spherical nanoparticles in the size range of 10–100 nm. AgNPs formed flower-like self-assembled structures after three months incubating at room temperature in the dark. The study provides the evidence that the factors in the cell-free culture supernatant facilitate synthesis of AgNPs. This study is the first report on the biosynthesis of AgNPs using supernatant of Streptomyces sp. ERI-3 bacterium.

This work investigates the potential of magnetic Fe3O4 nanoparticles as an adsorbent for simultaneous separation and preconcentration of trace amounts of palladium and rhodium from Pt–Ir alloy and dust samples, prior to flame atomic absorption spectroscopy determinations. The effect of pH on the adsorption of analyte ions over a pH range from 3 to 12 was studied. The analyte ions quantitatively were adsorbed on magnetic Fe3O4 nanoparticles in the pH range of 10–12 and, then, magnetic nanoparticles (MNPs) were easily separated from the aqueous solution by applying an external magnetic field. Thus, no filtration or centrifugation was necessary. After extraction and collection of MNPs, the analyte ions were eluted using HCl 1.0 mol L−1. Under the best experimental conditions, linearity was maintained between 0.01–5.5 μg mL−1 for palladium, and 0.005–3.0 μg mL−1 for rhodium. Detection limits for palladium and rhodium were 2.9 and 1.4 ng mL−1 based on 3Sb. The relative standard deviation of eight replicate measurements of 0.5 μg L−1 of Pd(II) and Rh(III) ions was 1.9% and 1.7%, respectively. Finally, the method was successfully applied to the extraction and determination of palladium and rhodium ions in Pt–Ir alloy and road dust samples.

A scanning tunneling microscope is a powerful tool for obtaining micrographs from conductive and semiconductive materials. The imaging technique has recently been improved for microscopy of nanostructured biomaterials on highly ordered atomic surfaces. We describe, here, high resolution imaging of individual IgM and IgG using a scanning tunneling microscope (Nama-STM) in air condition. The biomolecules were immobilized on the surface of Highly Ordered Pyrolytic Graphite (HOPG). Obtained micrographs could reveal structural details of immunoglobulins G and M on the atomically flat surfaces. Obtained results confirmed that STM could be more useful than other microscopy techniques for the analysis of single biomolecules.

The Electromagnetic Levitational Gas Condensation (ELGC) method was used to synthesize ZnO nanorods. In this paper, the formation mechanism of the synthesized nanorods is discussed. The ELGC method involved vaporization of the levitated Zn specimen, with subsequent condensation and oxidation of nuclei formed under Ar or He–0.2Ar and O2 atmospheres. The particles were characterized by X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). The presented results showed that the [0001]-oriented ZnO nanorods were directly produced by the ELGC process under different process conditions.

Herein, we report a safe, low cost and reproducible approach for the synthesis of antimony (Sb) nanostructures with most of them having prism like morphology and having well defined faces in the range of ∼70–210 nm. The organics free approach is based on a reaction of antimony powder and pure water at ∼210 °C without using any harmful additives and amines. The XRD pattern confirmed the composition and crystallinity of the grown nanostructures. The reported method besides being organics free is economical, fast and free of pollution, which will make it suitable for large scale production. Furthermore, it is well expected that such a technique could be extended to prepare many other important metal and metal oxide nanostructures. The prospects of the process are bright and promising.