Extensive substituent scrambling in substituted diphenylacetylenes on electron impact

Extensive randomization of the substituents is found in mono- and disubstituted diphenylacetylenes under electron impact conditions. The study of diphenylacetylenes with a variety of substituents indicates that the electron-withdrawing groups favour the substituent scrambling, AH the substituted diphenylacetylenes give an ion at m/z 176, having a common ion-structure, arising as a result of the expulsion of a hydrogen radical and the substituent in monosubstituted diphenylacetylenes and the expulsion of both the substituents in disubstituted diphenylacetylenes. A ring-expanded structure is postulated for this common fragment.     

Determination of stoichiometry of cadmium telluride by XPS

Summary The stoichiometry of cadmium telluride has been determined by the non-destructive technique of XPS. The determination has been based on differential photoionisation cross-sections, electron mean free paths and areas due to M₅ electrons of Cd and Te. The stoichiometry of Cd and Te determined by XPS has been found to be in good agreement with that obtained by analysing Cd and Te independently by chemical methods.     

Photochemical reduction of thallium(III) with hydrogen peroxide

A convenient method for determination of thallium(III) is based on photochemical reduction with hydrogen peroxide in the presence of bromide as catalyst, followed by oxidation of thallium(I) with potassium bromate.     

Electron-impact-induced hydrogen migration in organic molecules I–Substituent effects in the mass spectra of pivlanilides

Substited pivalanilides give rise to fragments corresponding to anilies on electron-impact, which is due to the migration of a hydrogen atom from the t-butyl group to the nitrogen. The Hammett correlation indicates that the formation of this fragment is favoured by electron-donating groups. The other interesting feature of these spectra is the migration of the aryl group to the t-butyl carbon with the elimination of the neutral ketemine.     

1H and 13C NMR spectra of cyclic trimers,tetramers and pentamers derived from p-substituted phenylacetylenes

The ¹H and ¹³C spectra of p-substituted 1,3,5-triarylbenzenes, 7- and p-substituted 1,3,9-triaryl-9-methyl-fluorenes and 2-, 10- and p-substituted 6,12,13a-triaryl-12-methylbenzo(6,7)cycloheptadieno[1,2,3-jk]fluorenes have been examined. p-Substituents were methoxy, methyl and fluorine groups. The ¹H spectra were recorded at 300 MHz and permitted assignments for the aromatic protons by selective proton decouplings. Partial assignment of the carbon atoms in the ¹³C spectra was also possible.     

Thin-layer chromatography of aluminium: quantitative densitometric determination of Fe2+, Ni2+, Cu2+, and Si4+

Thin-layer chromatography in combination with scanning densitometry is used as a tool for the quantitative determination of some impurity and additive elements in aluminium. Microgram levels of iron, silicon, copper, nickel, titanium, magnesium, manganese, and zinc present in a high concentration aluminium matrix is detected, and selective separations of some of these elements are achieved on silica gel H layers developed with a mobile phase containing aqueous sodium chloride solution. The quantitative determination of iron, silicon, nickel, and copper are obtained from the densitometric evaluation of chromatograms and are compared with the respective optical emission spectral analytical data.     

Polyaniline nanostructures expedient as working electrode materials in supercapacitors

Granular type polyaniline (PANi), PANi nanofibers (NFs), and PANi nanotubes (NTs) expedient as working electrode materials for supercapacitors are synthesized. The synthesis procedure used in this work facilitates not only the synthesis of solid powders of the PANi nanostructures, but also thin films constituted by the same PANi nanostructures in the same experiment. PANi NFs are found to exhibit faster electrode kinetics and better capacitance when compared to PANi NTs and granular PANi. Specific capacitance and energy storage per unit mass of PANi NFs are 239.47 Fg^?1 (at 0.5 Ag^?1) and 43.2 Wh?kg^?1, respectively. Electrical conductivity of PANi NFs is also better when compared to the other two nanostructures. Properties of the three PANi nanostructures are explicated in correlation with crystallinity, intrinsic oxidation state, doping degree, BET surface area, and ordered mesoporosity pertaining to the nanostructures.     

Growth, microstructure and electrical properties of sputter-deposited hafnium oxide (HfO2) thin films grown using a HfO2 ceramic target

Hafnium oxide (HfO₂) thin films have been made by radio-frequency (rf) magnetron-sputtering onto Si(1 0 0) substrates under varying growth temperature (T_s). HfO₂ ceramic target has been employed for sputtering while varying the T_s from room temperature to 500 °C during deposition. The effect of T_s on the growth and microstructure of deposited HfO₂ films has been studied using grazing incidence X-ray diffraction (GIXRD), and high-resolution scanning electron microscopy (HR-SEM) coupled with energy dispersive X-ray spectrometry (EDS). The results indicate that the effect of T_s is significant on the growth, surface and interface structure, morphology and chemical composition of the HfO₂ films. Structural characterization indicates that the HfO₂ films grown at T_s < 200 °C are amorphous while films grown at T_s > 200 °C are nanocrystalline. An amorphous-to-crystalline transition occurs at T_s = 200 °C. Nanocrystalline HfO₂ films crystallized in a monoclinic structure with a (−1 1 1) orientation. An interface layer (IL) formation occurs due to reaction at the HfO₂-Si interface for HfO₂ films deposited at T_s > 200 °C. The thickness of IL increases with increasing T_s. EDS at the HfO₂-Si cross-section indicate that the IL is a (Hf, Si)-O compound. The electrical characterization using capacitance-voltage measurements indicate that the dielectric constant decreases from 25 to 16 with increasing T_s. The current-voltage characteristics indicate that the leakage current increases significantly with increasing T_s due to increased ILs.     

Tuning of ring laser by varying the Gouy phase

Tuning a ring laser by using the Gouy phase is explored. We find a sensitive capability by moving a lens in the ring cavity. Application of the effect to ring laser gyro is discussed.