Enhanced Optical Properties of FeS2 Using Ni@Cu Doping and Characterization of the Structural and Chemical Compositions for Solar Cell Applications

Crystallography Reports - Transition metals doped FeS2 thin films are promising materials for optoelectronics, energy saving and storage applications. This is a first time report on the...     

Perovskite-sensitized solar cell utilizing TiO2 nanograss: Effect of dipping time of CH3NH3PbI3 perovskite

Organic perovskite has potential to replace organic dye as light absorber in solar cell since it possesses better optical absorption in visible region than organic dye. This work is concerned with the investigation of the influence of CH₃NH₃PbI₃ perovskite dipping time on the performance of perovskite-sensitized solar cell (PSSC). The effect of the dipping time on the morphology and photoluminescence of the sample has also been investigated. It was found that the device achieved a power conversion efficiency (PCE) as high as 5.57 ± 0.4% at the optimum dipping time of 4 h. The highest PCE is due to the highest IPCE, lowest R_ct and the longest carrier lifetime (τ).     

Quenchofluorimetric Determination of Mercury Trace with Murexide

 A sensitive and fairly selective quenchofluorimetric method for the determination of mercury ultra-trace with murexide (ammonium purpurate) has been developed. The method is based on the instantaneous quenching action of the metal-ion upon the native fluorescence of murexide [λ_ex(max) = 360 nm; λ_em(max) = 445 nm] in the optimum pH range of 5.8 to 6.6 at room temperature (25±0.5) °C. The fluorescence quenching is collinear in the range of 5 μg/L to 100 μg/L mercury. The developed method is very precise and accurate (RSD = 2.2% for 11 determination of 50 μg/L Hg(II). Large excesses of more than 50 cations, anions and complexing agents were found to have no interference. The developed method was successfully tested over synthetic mixtures of various compositions, certified reference materials and factory effluents. Received November 16, 1999. Revision March 30, 2001.     

Finite automata based algorithms on subsequences and supersequences of degenerate strings

In this paper, we present linear-time algorithms for the construction two novel types of finite automata and show how they can be used to efficiently solve the Longest Common Subsequence (LCS), Shortest Common Supersequence (SCS) and Constrained Longest Common Subsequence (CLCS) problems for degenerate strings.     

Douglas algebras which are invariant under the Bourgain map

Part of this work was done while the second author was visiting the University of Georgia, Athens/Georgia, USA.     

Optically-active bis(methyl-1-naphthylphenylsilyl)mercury

(+)-Bis(methyl-1-naphthylphenylsilyl)mercury has been prepared, though probably in an optically impure state. Racemization without decomposition takes place at about 150°, and stereospecific cleavages of the Si—Hg bonds are possible.     

Low frequency surface resonance modes in electron energy loss spectroscopy

Electron energy loss spectroscopy has proved a powerful probe of vibrational modes of a wide variety of adsorbed species. Here the primary focus has been on modes with frequency well above the maximum phonon frequency of the substrate. Examples are internal vibration modes of adsorbed molecules, possibly shifted significantly in frequency from their gas phase analogues, and high frequency vibrations of an adsorbed molecule or atom against the substrate. Recent experiments explore features in the energy loss spectrum with frequency below the maximum phonon frequency of the substrate, for ordered overlayers of atoms adsorbed on low index metal surfaces. We shall summarize our theoretical studies of such spectra for several adsorbate/substrate combinations, with emphasis oh the physical origin of the features which appear in the calculations. We obtain a good account of the existing data, within the framework of a rather simple lattice dynamical model, and the calculations show that the features which appear are quite sensitive to the symmetry of the adsorption sits, and other details of the surface geometry. We shall illustrate this with several specific examples.