Fabrication and characterization of thin films of single-walled carbon nanotube bundles on flexible plastic substrates

A convenient method to obtain patterns of films of single-walled carbon nanotubes (SWNT) bundles on flexible plastic is described. Using the Line Patterning method SWNT films of thickness ranging from approximately 300-1500 nm can be obtained from aqueous surfactant-supported dispersions of chemically purified SWNT bundles synthesized by the pulsed-laser ablation method. These films are strongly adherent and are competitive in performance with commercially available films of indium-tin-oxide (ITO) on plastics. For example, an approximately 1500 thick film of SWNT on poly(ethylene terephthalate) (PET) shows a surface resisitvity of approximately 80 Omega/sq, optical transparency >80%, and robust flexibility. Unlike ITO/PET, films of SWNT/PET can be folded and bent to a crease without cracking. The simple techniques involoved in obtaining these films (i.e., those without requiring lithography or ink-jet printing) could help facilitate the rapid fabrication of transparent, flexible electronic devices, heralding what promises to be a new approach towards the development of next-generation optoelectronic devices.     

Liquid anion exchanger study of gold (III) from aqueous halide media with N-n-octylaniline

N-n-octylaniline in xylene is used for the extractive separation of gold(III) from halide media. Gold(III) was extracted quantitatively with 10 ml of 2% reagent in xylene from 0.5-10 M and 0.5-8 M hydrochloric acid and hydrobromic acid, respectively. It was stripped from the organic phase with ammonia buffer solution (pH 10.1) and estimated spectrophotometrically with stannous chloride. The effect of metal ion, acids, reagent concentration and of various foreign ions has been investigated. Method is applicable to the analysis of synthetic mixtures containing platinum metals and alloy samples. The method is fast, accurate and precise.     

Synthesis, spectral, and single crystal X-ray structural studies on (2,2′-bipyridyl)bis(dimethyldithiocarbamato) zinc(II) and (1,10-phenanthroline) bis(dimethyldithiocarbamato)zinc(II)

Synthesis, spectral, and single crystal X-ray structural studies on (2,2-bipyridyl)bis (dimethyldithiocarbamato)zinc(II) (1) and (l,10-phenanthroline)bis(dimethyldithiocarbamato)zinc(II) (2) complexes are reported in this paper. The complex (1) crystallizes in the orthorhombic lattice, space group Pcca, a = 18.456(3), b = 6.529(2), and c = 17.092(2) Å. The complex (2) crystallizes in the monoclinic space group C2/c, a = 13.372(2), b = 13.850(2), c = 24.680(3) Å, and = 102.71(4)°. IR spectra of the complexes (1) and (2) show the thioureide (C-N) bands at 1489 and 1510 cm^–1, respectively, which are lower than the value observed for the parent bisdithiocarbamate. Reduction in the thioureide stretching frequency is due to the increase in coordination around the zinc ion and the resultant increase in electron density. Thermal studies indicate that the 1,10-phenanthroline adduct is marginally more stable than the other complex. X-ray crystal structures of the two adducts show them to be octahedrally coordinated and monomeric in nature. The Zn-S distances are longer than those observed in the parent bisdithiocarbamate. The thioureide C-N bond distances in (1) and in (2) indicate the partial double bond character. The most important structural changes as a result of the adduct formation are observed in the Zn-S bond distances and S-Zn-S bond angles, in terms of very significant increases in Zn-S bond distances and reductions in S-Zn-S angles, compared to the parent bisdithiocarbamate. The observed changes are indicative of a strong steric force in operation in the adducts rather than electronic effects.     

Reactions involving selenium metal as an electrophile: Scope and limitations of the enolate-selenolate transformation

When lithium enolates are allowed to react with selenium metal, selenolate (selenide) ions are formed. Alkylation of these selenolate ions produces the corresponding α-alkylselenenyl carbonyl derivatives. These derivatives can then be converted to their unsaturated counterparts using the same type of protocols that are employed with arylselenenyl derivatives.     

Activity coefficient measurements of the system HCl−ZnCl2−H2O at 25 and 35°C

Electromotive force measurements were carried out on the HCl–ZnCl₂–H₂O system at constant total ionic strengths of 0.1, 0.2, 0.5, 1.0 and 2.0 mol-kg^–1 at 25 and 35°C using a cell consisting of Pt, H₂(g, 1 atm)|HCl(m_A), ZnCl₂(m_B)|AgCl/Ag. The data were interpreted by the mixed electrolyte equations of Pitzer and Kim in order to evaluate mixing ion-interaction parameters. The activity coefficients of ZnCl₂ and the Gibbs excess free energies of mixing are calculated and presented at I=2.0 mol-kg^–1 and compared with similar systems containing transition metal chlorides.     

Frequency stabilization of a diode laser using electromagnetically induced transparency in a V-configuration cesium atom

An electromagnetically induced transparency (EIT) signal is observed in a V-type energy level scheme in a cesium vapor cell at room temperature. The effects of frequency detuning and the intensity of the pump laser on the EIT signal have been investigated. The performance of the probe-diode laser system, which is frequency stabilized on the EIT signal by using electrical feedback, is explored. The first derivative of the EIT signal offers a steeper slope and better S/N ratio for laser frequency stabilization than that of the Doppler-free hyperfine and crossover resonances. A comparative study of the frequency stability of an external-cavity diode laser stabilized at EIT and at the crossover resonance is presented. The square root of the Allan variance (σ) vs. integration time (τ) plot shows about a tenfold improvement in the frequency stability of the EIT-locked laser (σ ～ 2.043 × 10^?13τ^?1/2) over that of the crossover-locked laser under a short integration time (1–10 ms), whereas a twofold improvement is found under a long integration time (～1 s).     

Crystal Structure of the Orthorhombic Modification of a Mononuclear Peroxotitanium(IV) Dipicolinate

The deep red diaquoperoxotitanium dipicolinate [TiO₂(C₇H₃O₄N) (H₂O)₂]2H₂O crystallises in a pleochroic triclinic and a nonpleochroic orthorhombic modification. The structure of the former has been reported earlier. The structure of the latter, described in this paper, has been determined from X-ray diffractometer data and refined to R = 0.034. In both forms the complex occurs as the free acid, but the modes of packing are completely different. Bond lengths and angles agree closely. As in the other peroxotitanium(IV) chelate structures so far determined, titanium has an approximately pentagonal bipyramidal coordination with the peroxo group and the chelate ligand occupying equatorial sites and the waters forming the apices. The relationship proposed earlier between the basicity of the ligands and the bond lengths and colours of the related compounds is substantiated. The final difference Fourier maps obtained with normal and modified refinement procedures clearly reveal bonding electron densities. They indicate a pentagonal bipyramidal sp³d³ hybridisation of titanium with bent Ti-O_peroxo bonds, again in agreement with the triclinic form and other peroxotitanium chelates.     

Performance of a cobalt oxide catalyst in the oxidation of NH3 to NO

The cause for a fall in the conversion of NH₃ to NO within 73 hours from 97% to 78% with a cobalt oxide catalyst was investigated. Results show that sintering, change in valence and cation distribution in Co₃O₄ contribute to the decrease in activity. Incorporation of ThO₂ and K₂O improves the performance of the catalyst.

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NH₃ NO 73 97% 78%. , , Co₃O₄. ThO₂ K₂O NH₃ NO.