A ToF-MS with a Highly Efficient Electrostatic Ion Guide for Characterization of Ionic Liquid Electrospray Sources

We report on the development of a time-of-flight (ToF) mass spectrometer with a highly efficient electrostatic ion guide for enhancing detectability in ToF mass spectrometry. This 65-cm long ion guide consists of 13 cascaded stages of Einzel lens to collect a large fraction of emitted charges over a wide emission angle and energy spread for time-of-flight measurements. Simulations show that the ion guide can collect 100% of the charges with up to 23° emission half-angle or 30% energy spread irrespective of their specific charge. We demonstrate this ion guide as applied to electrospray ion sources. Experiments performed with tungsten needle electrospraying the ionic liquid EMI-BF₄ showed that up to 80% of the emitted charges could be collected at the end of the flight tube. Flight times of monomers and dimers emitted from the needles were measured in both positive and negative emission polarities. The setup was also used to characterize the electrospray from microfabricated silicon capillary emitters and nearly 30% charges could be collected even from a 40^° emission half-angle. This setup can thus increase the fraction of charge collection for ToF measurement and spray characteristics can be obtained from a very large fraction of the emission in real time.      

Bis(Saccharinato)Nickel(II) Complexes with 2-Aminomethyl and -Ethylpyridines. Syntheses,Crystal Structures,Spectral and Thermal Analyses of trans-[Ni(sac-N)2(ampy-N,N′)2] and trans-[Ni(sac-O)2(aepy-N,N′)2]

The trans-bis(saccharinato)nickel(II) complexes with 2-aminomethylpyridine (ampy) and 2-aminoethylpyridine (aepy) have been prepared and characterized by elemental analyses, i.r., u.v.–vis., magnetic measurements and single crystal X-ray diffraction. Both structures consist of discrete molecules of the title complexes, in which the nickel(II) ion lies on an inversion centre and is octahedrally coordinated by two bidentate (N,N) ampy or aepy ligands and two anionic sac ligands, occupying trans positions. The most interesting feature of the complexes is the coordination of sac. In [Ni(sac)₂(ampy)₂], sac is N-bonded, whereas it is O-coordinated in [Ni(sac)₂(aepy)₂]. The i.r. spectra and thermal behaviour of both complexes are discussed in detail.     

Microstructural, optical and electrical studies on sol gel derived ZnO and ZnO:Al films

ZnO and ZnO:Al films were deposited onto glass substrates by the sol gel method using spin coating technique. The effects of aluminum dopant on the crystalline structure and orientation of the ZnO films have been investigated by X-ray diffraction (XRD) study. Surface morphology of the films has also been analyzed by a field emission scanning electron microscope (FESEM) and atomic force microscope (AFM). The average optical transmittance values of all the films is over >83% in the visible region. The optical band gap and Urbach energy values of these films were determined. The absorption edge shifted to the lower energy depending on the Al doping level. The shift of absorption edge is associated with shrinkage effect. The electrical conductivity of the ZnO film enhanced with the Al dopant. From the temperature dependence of conductivity measurements, the activation energy of the films was also calculated.     

A spectroelectrochemical study on single-oscillator model and optical constants of sulfonated polyaniline film

The optical properties of sulfonated polyaniline (SPAN) thin film prepared by electrochemical method have been investigated. Polychromic behavior of SPAN thin film (transparent yellow-green-dark blue) was observed when the cyclic voltammograms were taken between -0.25 V and +1.90 V (vs. Ag/AgCl, sat.) during the growth of polyaniline film. In situ UV-vis spectra of the polymers-indium tin oxide (ITO) glass electrode were taken during the oxidation of the polymers at different applied potentials. The direct band gap values of SPAN thin film changed from 3.771 eV to 3.874 eV with the applied potentials. From in situ UV-vis spectra, the optical constants such as refractive index and dielectric constant of the SPAN thin film were determined. The important changes in absorption edge, refractive index and the dielectric constant were observed due to the applied potentials. The refractive index dispersion curves of the film obey the single-oscillator model and oscillator parameters changed with the applied potentials. The most significant result of the present work is in situ spectroelectrochemical method, which can be used to modify the optical band gaps and constants.     

Model for Gas–Condensate Phase Equilibria for Estimating C7+ Critical Properties Using Genetic Algorithm

A reliable prediction of the phase behavior is necessary in determining the compositions of the gas and liquid phases at various pressures. These calculations require stepwise computational procedure using a cubic equation of state (EOS). Since the heavy components in the petroleum mixtures have the strongest effect on the characteristics of the fluids, critical properties must be estimated for the petroleum fractions making up heptanes-plus. A phase equilibria calculation of a gas–condensate system with Peng–Robinson equation of state was done by satisfying the condition of chemical equilibrium. A genetic algorithm was used to determine the optimum critical properties of heptanes-plus (C₇₊) fraction. The predictions of the model are compared with the experimental results of the constant volume depletion (CVD) test.