Influence of NH<Subscript>3</Subscript> flow rate on pyridine-like N content and NO electrocatalytic oxidation of N-doped multiwalled carbon nanotubes

Nitrogen-doped multiwalled carbon nanotubes (N-MWCNTs) have been prepared by pyrolysis of pyridine and iron phthalocyanine over an iron catalyst at 850 °C at various ammonia gas (NH₃) flow rates. X-ray photoelectron spectroscopy results reveal that the pyridine-like nitrogen (N) content can be controlled by changing the flow rate of NH₃, and that pyridine-like N plays an important role: it can increase the electrocatalytic activity and the rate of nitric oxide (NO) electrooxidation and decrease the activation energy of NO electrooxidation. Cyclic voltammetry results demonstrate that the N-MWCNTs sample grown with 200 mL/min NH₃ flow has the maximum N content of 3.22 atomic %, and its content of pyridine-like N that is chemically active is also the highest among all the N-MWCNTs samples. Electrochemical impedance spectroscopy results indicate that two-step electron transfer process occurs at the N-MWCNT-modified electrode, and the control step is different in various potential regions. The stability of NO electrooxidation at the N-MWCNT-modified electrode is examined, and the reaction mechanism is discussed.     

On the role of the colloidal stability of mesoporous silica nanoparticles as gene delivery vectors

Mesoporous silica nanoparticles have been synthesized and functionalized with four different types of molecules containing amino groups, i.e., with primary amines only, with quaternary amines, with quaternized cyclic amines, or with polyethylenimine (PEI), which is formed by primary, secondary, and tertiary amines. These nanoparticles were then incubated with reporter plasmids and the ability of the resulting complexes to transfect human cells was studied. Only nanoparticles functionalized with PEI were efficient for transfection. The agglomeration behavior and the electrokinetic potential of the nanoparticle–plasmid complexes have been studied, as well as their cell internalization behavior using a fluorescent-labeled plasmid that allows its monitorization by confocal microscopy. The results indicate that the efficiency of PEI-functionalized nanoparticles for transfection resides to some extent in the different characteristics imparted to the nanoparticles regarding agglomeration and surface charge behavior.     

Synthesis of the chain-shaped carbon fibers decorated with SiO<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> beads by chemical vapor deposition

Chain-shaped carbon fibers decorated with SiO _x beads had been synthesized by using methyltriehlorosilane and normal carbon fibers as the raw materials, during which the chemical vapor deposition technique was applied. The products were characterized by scanning electron microscopy (SEM), energy dispersive spectrum (EDS), X-ray diffraction (XRD) and Raman spectroscopy. The as-received products show chain-shaped morphologies that have the normal carbon fibers as “strings” and possess regular SiO _x beads of 30–40 μm with relative smooth surface. The formation of the chain-shaped morphology is considered to involve the shrinkage of the absorbed silica layer and the possible growth mechanism is further proposed. It is thought that the chain-shaped carbon fibers are formed by two main stages.     

Synthesis and characterization of “mulberry”-like Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>/multiwalled carbon nanotube nanocomposites

Nanocomposites composed of multi-wall carbon nanotubes (MWNTs) and Fe₃O₄ nanoparticles were fabricated using solvothermal method. Transmission and scanning electron microscopy, energy dispersive spectroscopy, and X-ray powder diffraction measurements confirmed that these mulberry-like Fe₃O₄ microparticles which were combined with the MWNTs in a random pattern are constructed with tiny nanocrystallites (12 nm in average diameter). The magnetic properties of the Fe₃O₄/MWNTs nanocomposites were measured using a vibrating sample magnetometer. Results showed that the Fe₃O₄/MWNTs nanocomposites exhibited superparamagnetism at room temperature and possessed a lower saturation magnetization (around 27.6 emu/g) than that of the pure Fe₃O₄ nanoparticles (around 33.7 emu/g). The Fe₃O₄/MWNTs nanocomposites have potential applications in engineering and medicine.     

Determination of Total Antioxidant Capacity by a New Spectrofluorometric Method Based on Ce(IV) Reduction: Ce(III) Fluorescence Probe for CERAC Assay

A Ce(IV)-based reducing capacity (CERAC) assay was developed to measure the total antioxidant capacity (TAC) of foods, in which Ce(IV) would selectively oxidize antioxidant compounds but not citric acid and reducing sugars which are not classified as antioxidants. The method is based on the electron-transfer (ET) reaction between Ce(IV) ion and antioxidants in optimized acidic sulphate medium (i.e., 0.3 M H₂SO₄ and 0.7 M Na₂SO₄) and subsequent determination of the produced Ce(III) ions by a fluorometric method. The fluorescent product, Ce(III), exhibited strong fluorescence at 360 nm with an excitation wavelength of 256 nm, the fluorescence intensity being correlated to antioxidant power of the original sample. The linear concentration range for most antioxidants was quite wide, e.g., 5.0 × 10⁻⁷–1.0 × 10⁻⁵ M for quercetin. The developed procedure was successfully applied to the TAC assay of antioxidant compounds such as trolox, quercetin, gallic acid, ascorbic acid, catechin, naringin, naringenin, caffeic acid, ferulic acid, glutathione, and cysteine. The proposed method was reproducible, additive in terms of TAC values of constituents of complex mixtures, and the trolox equivalent antioxidant capacities (TEAC coefficients) of the tested antioxidant compounds gave good correlations with those found by reference methods such as ABTS and CUPRAC.     

Interplay of information quantifiers and the modified Jaynes-Cummings model

The dynamics of the Buck and Sukumar model (B. Buck and C. V. Sukumar, Phys. Lett. A 81, 132 (1981)) is investigated using different semi-classical information-theory tools. Their interplay reveals somewhat unexpected features. A new signature for the classical-quantum barrier is encountered thereby.     

Electro- and magneto-optical switching of defect modes in one- dimensional photonic crystals

The transmission spectra of polarized light waves in a photonic crystal/liquid crystal (PC/LC) cell placed between crossed polarizers and controlled by an electric or magnetic field have been studied experimentally and theoretically. Electro- and magneto-optical switching based on the interference of polarized defect modes has been demonstrated. The transmission spectra of the PC/LC cell have been calculated as a function of the voltage applied to the LC layer and the magnetic field strength. The results of the calculations agree well with the experimental data.     

Separation of different wave components in the Bethe–Salpeter wave function

The scalar products of polarization tensor and unit vectors are presented explicitly in spherical coordinate system expanded in terms of spherical harmonic functions. By applying the obtained formulae, different wave components in the Salpeter wave function can be shown explicitly, and the results are consistent with the results obtained by L–S coupling analysis. The cancelation formula is given, by which the terms with pure L = J + 1 wave components in the Salpeter wave function for the bound state with h_P=(-1)^J\eta_{\rm P}=(-1)^J can be obtained by separating the L = J − 1 wave components from mixing terms. This separation provides the basis for studying higher-order contributions from the coupling of L = J − 1 and J + 1 wave states, and for solving the Salpeter equation exactly without approximation.     

An Alternative to the Gauge Theoretic Setting

The standard formulation of quantum gauge theories results from the Lagrangian (functional integral) quantization of classical gauge theories. A more intrinsic quantum theoretical access in the spirit of Wigner’s representation theory shows that there is a fundamental clash between the pointlike localization of zero mass (vector, tensor) potentials and the Hilbert space (positivity, unitarity) structure of QT. The quantization approach has no other way than to stay with pointlike localization and sacrifice the Hilbert space whereas the approach built on the intrinsic quantum concept of modular localization keeps the Hilbert space and trades the conflict creating pointlike generation with the tightest consistent localization: semiinfinite spacelike string localization. Whereas these potentials in the presence of interactions stay quite close to associated pointlike field strengths, the interacting matter fields to which they are coupled bear the brunt of the nonlocal aspect in that they are string-generated in a way which cannot be undone by any differentiation.     

Phase-controlled preparation of iron (oxyhydr)oxide nanocrystallines for heavy metal removal

Obtaining cost-effective iron (oxyhydr)oxide nanocrystallines is the essential prerequisite for their future extensive applications in environmental remediation, such as the removal of heavy metals from contaminated waters. Here, various phases of iron (oxyhydr)oxide nanocrystallines were simply synthesized from the phase-controlled transformation of amorphous hydrous ferric- or ferrous-oxide in thermal solution with a certain ethanol/water ratio and with the presence of oleic acid. According to this method, goethite nanorods in diameter of 3–4 nm, hematite nanocubes sized 20–30 nm, and magnetite nanoparticles in diameter of 6–7 nm were successfully obtained. The final products of this transformation can be conveniently controlled by adjusting the reaction parameters, such as pH, temperature, and ethanol/water ratio. Due to the enhanced specific surface area and probably the modifications of the surface structure of nanocrystallines, the as-synthesized goethite nanorods and magnetite nanoparticles demonstrated extremely strong As(III) affinity, with 5.8 and 54 times of As(III) adsorption, respectively, higher than the micron-sized relatives. The cost-effective feature of as-synthesized nanocrystallines and their remarkably enhanced affinity toward arsenic made them potentially applicable for the removal of arsenic and such like heavy metals from the contaminated environment.