New hardware for radio frequency powered glow discharge spectroscopies and its capabilities for analytical applications

A new radio frequency (rf) hardware is developed for glow discharge spectroscopic methods. The resulting features and its capabilities for analytical applications are discussed. The electrical equipment developed allows to work as quickly, stably, reliably and easily as known from the direct current (dc) mode. Moreover, the rf power measurement has been improved. The hardware has been developed, optimised and tested for glow discharge optical emission spectroscopy (GDOES), but nevertheless it is possible to use it for all procedures applying glow discharge sources.     

Regioselective Synthesis of Mixed Indole 2,3-Bis(sulfides). A Study of the Mechanism of the Second Sulfenylation of Indole

Sulfenylation of indole using sulfenyl chlorides leads to the initial formation of a 3-indolyl sulfide, while excess reagent introduces a second sulfide at the 2-position of the ring. The mechanism of this second sulfenylation has not, to date, been rigorously elucidated. The development of the first, regioselective synthesis of mixed indole 2,3-bis(sulfides) has allowed the study of the sulfenylation of 3-indolyl sulfides using a different sulfenyl chloride. Our results afford evidence that the reaction proceeds via an intermediate 3,3-disulfenylated indolenine species, with subsequent migration of one of the sulfide groups to the 2-position.     

An efficient synthesis of [1,1]ferrocenophane via 1,1′-bis(6-fulvenyl)ferrocene

[1,1]Ferrocenophane can be prepared by reduction of 1,1′-bis(6-fulvenyl)ferrocene with complex borohydrides to give the dianion of 1,1′-bis(cyclopentadienylmethyl)ferrocene. Reaction of this dianion with ferrous chloride produces the ferrocenophane in good yield.     

The acid-catalyzed and neutral solvolysis of benzoylphenyldiazomethane in water,aqueous t-butanol,and aqueous salt solutions

The acid-catalyzed and water-catalyzed solvolysis ofbenzoylphenyldiazomethane (1) have been studied in water and in t-butanol-water mixtures, the mole fraction of water (n_H2O) being varied from 0·75-1·00. Increasing t-butanol concentrations produce a pronounced decrease in both k_H⊕ and k_H2O. In the “water reaction” mutually compensatory changes of AH

and AS

are associated with the rate variations, with minima in AH

and AS

at about n_H2O = 0·95. In addition it was found that the magnitude of the salt effect of (n-Bu)₄NCl on the rate of hydrolysis of 1 in water at 25° is much larger than that of LiCl, NaCl and NaBr. Assuming that the rate of the “water reaction” is largely determined by water acidity, the data are suggestive for the existence of a relation between water acidity and solvent structural integrity in highly aqueous t-butanol-water solutions.     

Synthesis of 2,3′-biindolyls and indolo[3,2-a]carbazoles

Several highly activated 2,3′-biindolyls were prepared from methyl 5,6-dimethoxyindole-2-carboxylate and oxindoles. The 2,3′-biindolyls were further transformed into a hydroxy indolo[3,2-a]carbazole and a bisindole amide.     

Functionalization of Electrode Surfaces with Monolayers of Azocompounds and Gold Clusters

Properties of monolayers of azocrown compound self-assembled on gold substrates were studied using voltammetry and scanning tunneling microscopy. The surface concentrations of this compound in monolayers were determined from the area of the voltammetric reduction peaks. The area per one molecule estimated from voltammetry experiments is 0.65 nm². This value was comparable with the limiting molecular area of the compound in the Langmuir–Blodgett film at the air–water interface. We also observed the presence of gold clusters and other gold structures by STM when a gold electrode modified with azocrown compound was dipped into the tetrachloroaurate solution. Even better spectra of clusters were obtained following one voltammetric scan in the range 0.5 to ?0.6 V. After more cycles or if we condition the electrode at 0.4 V the clusters aggregate into wires.     

Quantitative depth profiling in glow discharge spectroscopies – A new deconvolution technique to separate effects of an uneven erosion crater shape

An algorithm is presented as a concept for the quantification in direct current and radiofrequency glow discharge (GD) modes for GD optical emission spectroscopy. The algorithm is divided into excitation and sputtering part and thus it is possible to distinguish between the different excitation processes and to consider equivalent sputtering crater formations in both modes. Intensity-time profiles are affected corresponding to the method by several effects. One important effect is that sputtering occurs at a single time in different depths because of curved crater bottoms, this is usually called crater effect. The main purpose is to introduce an iterative deconvolution technique which for the quantification numerically takes into account the curved sputtering crater bottom. Input data for the deconvolution technique are the calibrated mass-time profile, the partial densities of the sample constituents and the measured final shape of the sputtering crater. Using a relatively simple model for ion sputtering the deconvolution technique improves iteratively the calculated layer structure by means of information on crater formation. The mathematical handling is illustrated for the quantification of a depth profile of a multilayer sample of ten 100 nm layers. The resulting concentration-depth profile reflects excellently the real elemental distribution of the multilayer system.     

The heliobacteria, a new group of photosynthetic bacteria

A review is given of the photosynthetic properties of the heliobacteria, a new group of photosynthetic bacteria, discovered only 14 years ago. These bacteria contain a “new” pigment, bacteriochlorophyll g, and they have a relatively simple pigment system, consisting of a core-reaction center complex only. Like the green sulfur bacteria, they have a Photosystem I-type reaction center, with a chlorophyll a derivative as primary electron acceptor. Because of the absence of an extensive peripheral antenna system, the reaction center processes in these bacteria are much easier to study than those in the green sulfur bacteria.     

ESR study of monoalkylzinc-2,2′-bipyridine complexes RZn · Bipy

Paramagnetic species are formed when LiBipy is treated with various alkylzinc halides at ?100°C and the ESR spectra are discussed. The observation that the half-life times of the radical species appear to depend only on the nature of the alkyl group bound to zinc proves that monoalkylzinc-2,2′-bipyridine complexes are formed. The nature of the bonding between zinc and 2,2′-bipyridine is discussed.