Homo- and heteronuclear 2D NMR approaches to analyse a mixture of deuterated unlike/like stereoisomers using weakly ordering chiral liquid crystals

We describe several homo- and heteronuclear 2D NMR strategies dedicated to the analysis of anisotropic (2)H spectra of a mixture of dideuterated unlike/like stereoisomers with two remote stereogenic centers, using weakly orienting chiral liquid crystals. To this end, we propose various 2D correlation experiments, denoted "D(H)(n)D" or "D(H)(n)C" (with n=1, 2), that involve two heteronuclear polarization transfers of INEPT-type with one or two proton relays. The analytical expressions of correlation signals for four pulse sequences reported here were calculated using the product-operators formalism for spin I=1 and S=1/2. The features and advantages of each scheme are presented and discussed. The efficiency of these 2D sequences is illustrated using various deuterated model molecules, dissolved in organic solutions of polypeptides made of poly-gamma-benzyl-L-glutamate (PBLG) or poly-epsilon-carbobenzyloxy-L-lysine (PCBLL) and NMR numerical simulations.     

Role of recording geometry in the performance of spectral diversity filters with spherical beam volume holograms

We present experimental demonstrations of spectral diversity filters with spherical beam volume holograms for multimodal multiplex spectroscopy. Major properties of filters under diffuse-light illumination are discussed. The comparisons of spectral diversity between the transmission geometry holograms and the reflection geometry holograms are also studied. The results show that there is a trade-off between the degree of the spatial coherence of the source and the spectral diversity of the filter. We also conclude that the reflection geometry holograms have better spectral diversity and less sensitivity to the spatial coherence of the source.     

Effects of plasticiser on the lithium ionic conductivity of polymer electrolyte PVC-LiCF3SO3

Solid polymer electrolyte films based on poly(vinyl chloride)-lithium triflate (PVC-LiCF₃SO₃) have been prepared by the solution-cast technique in various concentrations. The film with the highest conductivity was used to prepare plasticised polymer electrolyte films by using poly(ethlene glycol) (PEG) of different molecular weights, i.e., 200, 400 and 600 gmol⁻¹. These films were prepared to study the effects of addition of low molecular weights PEG on the lithium ionic conduction of the PVC based polymer electrolyte. The films were characterised by electrochemical impedance spectroscopy (EIS) and Fourier transform infrared-spectroscopy (FTIR). Results indicate that the molecular weight has an inverse effect on the conductivity and this has been accounted for by FTIR. Paper presented at the International Conference on Functional Materials and Devices 2005, Kuala Lumpur, Malaysia, June 6 – 8, 2005.     

Waveguide electro-optic modulator in fused silica fabricated by femtosecond laser direct writing and thermal poling

An integrated electro-optic waveguide modulator is demonstrated in bulk fused silica. A Mach-Zehnder interferometer waveguide structure is fabricated by direct writing with a femtosecond laser followed by thermal poling. A 20 degrees electro-optic phase shift is achieved at an operating wavelength of 1.55 microm with an applied voltage of 400 V and an interaction length of 25.6 mm, which correspond to an estimated effective electro-optic coefficient of 0.17 pm/V for the TE-polarized mode.     

Optical time-domain analog pattern correlator for high-speed real-time image recognition

The speed of image processing is limited by image acquisition circuitry. While optical pattern recognition techniques can reduce the computational burden on digital image processing, their image correlation rates are typically low due to the use of spatial optical elements. Here we report a method that overcomes this limitation and enables fast real-time analog image recognition at a record correlation rate of 36.7 MHz--1000 times higher rates than conventional methods. This technique seamlessly performs image acquisition, correlation, and signal integration all optically in the time domain before analog-to-digital conversion by virtue of optical space-to-time mapping.     

Sonochemical syntheses of a new nano-plate cadmium(II) coordination polymer as a precursor for the synthesis of cadmium(II) oxide nanoparticles

Nanoplates of the three-dimensional coordination polymer, {[Cd(3)(3-pyc)(4)(N(3))(2)(H(2)O)](n) (1), 3-pyc(-)=pyridine-3-carboxylate), have been synthesized by a sonochemical process and characterized by scanning electron microscopy, X-ray powder diffraction, IR spectroscopy and elemental analyses. Cadmium(II) oxide nanoparticles were prepared from thermal decomposition in oleic acid and direct calcination of compound 1 at different temperatures. The thermal stability of nano-sized compound 1 was studied by thermal gravimetric (TG) and differential thermal analyses (DTA). Results show that the size and morphology of the CdO nanoparticles are dependent upon the particles size of compound 1 and the thermolysis temperature. A decrease in the particle size of compound 1 leads to a decrease in the particle size of the CdO, while an increase in the processing temperature leads to an increase in the particle size of the produced cadmium(II) oxide nano-particles.     

A selective sensor for nanolevel detection of lead (II) in hazardous wastes using ionic-liquid/Schiff base/MWCNTs/nanosilica as a highly sensitive composite

An effective potentiometric sensor had been fabricated for the rapid determination of Pb²⁺ based on carbon paste electrode consisting of room temperature ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate (BMIM-PF₆), multiwalled carbon nanotubes (MWCNTs), nanosilica, synthesized Schiff base, as an ionophore, and graphite powder. The constructed nanocomposite electrode showed better sensitivity, selectivity, response time, response stability, and lifetime in comparison with typical Pb²⁺ carbon paste electrode for the successfully determination of Pb²⁺ ions in water and in waste water samples. The best response for nanocomposite electrode was obtained with electrode composition of 18% ionophore, 20% BMIM-PF₆, 49% graphite powder, 10% MWCNT, and 3% nanosilica. The new electrode exhibited a Nernstian response (29.76?±?0.10 mV decade^?1) toward Pb²⁺ ions in the range of 5?×?10^?9?C1.0?×?10^?1 mol L^?1 with a detection limit of 2.51?×?10^?9 mol L^?1. The potentiometric response of prepared sensor is independent of the pH of test solution in the pH range of 4.5?C8.0. It has quick response with response time of about 6 s. The proposed electrode show fairly good selectivity over some alkali, alkaline earth, transition, and heavy metal ions.     

Time-stretch oscilloscope with dual-channel differential detection front end for monitoring of 100 Gb/s return-to-zero differential quadrature phase-shift keying data

Optical performance monitoring of high-capacity networks is one of the enabling technologies of future reconfigurable optical switch networks. In such networks, rapid performance evaluation of data streams becomes challenging due to the use of advanced modulation formats and high data rates. The time-stretch enhanced recording oscilloscope offers a potential solution to monitoring high-rate data in a practical time scale. Here we demonstrate an architecture with a differential detection front end for simultaneous I/Q data monitoring of a 100 gigabits/s return-to-zero differential quadrature phase-shift keying signal. This demonstration shows the potential of this technology for rapid performance monitoring of high-rate optical data streams that employ advanced modulation formats.     

Evolution of Zn based high purity phases under NH3 gas atmosphere and their PL properties

We report here the evolution of zinc based high purity phases with novel morphologies such as Zn₃N₂ hollow structures, ZnO nanowires and nanopowders, as well as metallic Zn layered hexagonal microparticles at progressively increased reaction temperature of 600 °C, 700 °C, 800 °C under NH₃ gas atmosphere using Zn powder precursor and keeping all other experimental parameters unchanged. Growth mechanism for Zn₃N₂ obtained by nitridation, ZnO by oxidation and Zn microparticles via thermal evaporation & condensation process are discussed briefly. The as-synthesized products were characterized by X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS) and scanning electron microscopy (SEM). Photoluminescence (PL) studies have revealed very interesting and infrequently observed emission bands at 378 and 661 nm for Zn₃N₂, 359 and 396 nm for ZnO as well as 389 nm for Zn polyhedral microparticles.