Structural and conductivity changes during the pyrolysis of polyaniline base

Polyaniline base has been exposed to various temperatures between 100 °C and 1000 °C for 2 h in air. The mass loss has increased with increasing temperature. FTIR and Raman spectroscopies show the gradual destruction of the PANI structure, the possible formation of intermediate oxime and nitrile groups, and the final conversion to graphitic material. The elemental analysis confirmed the dehydrogenation while the content of nitrogen was nearly constant even after treatment at 800 °C. The conductivity of PANI base, 10⁻⁸ S cm⁻¹, increased to ∼10⁻⁴ S cm⁻¹ after treatment at 1000 °C; most of the products, however, were non-conducting. Another series of experiments involved the polyaniline base heated at 500 °C for 1-8 h. The studies were performed in connection with the potential flame-retardant application of polyaniline.     

The role of acidity profile in the nanotubular growth of polyaniline

Conditions of polyaniline (PANI) nanotubes preparation were analyzed. Aniline was oxidized with ammonium peroxydisulfate in 0.4 M acetic acid. There are two subsequent oxidation steps and the products were collected after each of them. At pH > 3, neutral aniline molecules are oxidized to non-conducting aniline oligomers. These produce templates for the subsequent growth of PANI nanotubes, which takes place preferably at pH 2–3. At pH < 2, granular morphology of the conducting PANI is obtained. High final acidity of the medium should be avoided in the preparation of nanotubes, e.g., by reducing the amount of sulfuric acid which is a by-product. Reduction of the peroxydisulfate-to-aniline mole ratio was tested for this purpose in the present study. Lowering of the reaction temperature from 20°C to −4°C had a positive effect on the formation of nanotubes.     

Microwave accelerated aza-Claisen rearrangements

The microwave-assisted thermal aza-Claisen rearrangement of allylic imidates and thiocyanates to the corresponding amides and isothiocyanates is investigated. Significant accelerations of the rearrangement of allylic imidates to amides and of allylic thiocyanates to isothiocyanates in comparison with standard thermal reactions is observed.     

Palladium Biosensor

In this paper we proposed a palladium(II) biosensor. The biosensor is based on determining of interactions between palladium(II) and metallothionein modified hanging mercury drop electrode by means of differential pulse voltammetry. We studied influence of two supporting electrolytes (potassium or sodium chloride) on the signals of the biosensor. Based on the results obtained we found potassium chloride (0.05 M) as the most suitable supporting electrolyte to determine palladium(II). The detection limit of the biosensor for palladium ions was evaluated as 100 nM with RSD about 10%. Moreover, we utilized the biosensor for measurement of the target molecule in the presence of human blood serum and human urine.     

Colored pI standards and gel isoelectric focusing in strongly acidic pH

Colored, low molecular weight pI markers have been developed for isoelectric focusing (IEF) in acidic pH range. Their isoelectric points (pIs) were determined by direct measurement of the pH of the focused bands after completion of IEF on polyacrylamide gels. The practicable suitability of the proposed pI markers as pI standards for IEF was tested by applying gel IEF. The acidic pH gradient was created either by commercial synthetic carrier ampholytes or by mixture of simple buffers consisting of acids (non-ampholytes) and ampholytic buffers. By applying simple acids, it was possible to extend the acidic pH range beyond those achievable with commercial synthetic carrier ampholytes. By using an experimental arrangement without electrode electrolyte reservoirs with electrodes creating the fixed end of the gel, the strongly acidic pH gradient was stable even for prolonged focusing time.     

The three‐dimensional coordination polymer tetra­ethyl­ammonium (ethyl­ene­di­amine)­cadmium(II) hexa­cyano­ferrate(III), (Et4N){[Cd(en)]4[Fe(CN)6]3}

The title compound, tetra­ethyl­ammonium dodeca‐μ‐cyano‐hexa­cyano­tetrakis­(ethyl­ene­di­amine)­tetra­cadmium(II)­tri­fer­rate(III), (C₈H₂₀N)[Cd₄Fe₃(CN)₁₈(C₂H₈N₂)₄], was pre­pared from a reaction mixture containing CdCl₂, K₃[Fe(CN)₆], ethyl­ene­di­amine (en) and [Et₄N]Br in a 1:1:3:1 molar ratio. The crystal structure consists of a negatively charged three‐dimensional framework of {[Cd(en)]₄[Fe(CN)₆]₃} anions, with [Et₄N]⁺ cations located in the cavities of the framework. The Cd atom is octahedrally coordinated by one disordered chelating en mol­ecule [mean Cd—N = 2.35 (3) Å] and four N‐­bonded bridging cyano groups [Cd—N distances are in the range 2.283 (2)–2.441 (2) Å]. There are two crystallographically independent [Fe(CN)₆]³⁻ anions in the structure and in each the Fe atom lies on a twofold axis. In the first [mean Fe—C = 1.941 (5) Å], all the cyano groups are bridging ligands, while in the second [mean Fe—C = 1.945 (2) Å], there are two terminal cyano ligands in trans positions. The Cd—N—C angles range from 128.6 (2) to 172.8 (2)°.     

Magnetic poly(glycidyl methacrylate) particles prepared in the presence of surface‐modified γ‐Fe2O3

Maghemite (γ‐Fe₂O₃) colloid has been synthesized by coprecipitation of ferrous and ferric salts in alkaline medium and oxidation. The obtained nanoparticles were complexed with a phosphate macromonomer—penta(propylene glycol) methacrylate phosphate (PPGMAP). Complexes with the weight ratio PPGMAP/γ‐Fe₂O₃ 0.01–10 were investigated using a range of characterization methods. The amount of PPGMAP attached to the particles was about 22 wt %. The size and size distribution of the γ‐Fe₂O₃ core particles in the dry state was measured by TEM. To complete the TEM images, the hydrodynamic size of the nanoparticles including polymer shell and the maghemite core was determined by DLS measurements in toluene. Magnetic poly(glycidyl methacrylate) (PGMA) nanospheres were obtained by Kraton G 1650‐stabilized and 2,2′‐azobisisobutyronitrile‐initiated polymerization of glycidyl methacrylate (GMA) in toluene or toluene/cyclohexane mixture in the presence of PPGMAP‐coated γ‐Fe₂O₃ colloid. The effect of Kraton G 1650 concentration on the morphology, PGMA nanosphere size and polydispersity was investigated. The particles were characterized also by both thermogravimetric analysis and magnetic measurements. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4982–4994, 2009     

Radiolysis of oxalic and citric acids using gamma rays and accelerated electrons

The radiation technique was tested as a method for degradation of organic complexants in spent decontamination solutions. Aqueous solutions containing oxalic and/or citric acid were irradiated under different conditions. Kinetics of radiolysis of both acids was studied; the effects of various parameters, presence of inorganic ions and saturation by various gases on their degradation were investigated. Results show that irradiation leads to a sufficient degree of removal of both acids from the solution.     

Whole genome amplification induced bias in the detection of KRAS‐mutated cell populations during colorectal carcinoma tissue testing

Whole genome amplification replicates the entire DNA content of a sample and can thus help to circumvent material limitations when insufficient DNA is available for planned genetic analyses. However, there are conflicting data in the literature whether whole genome amplification introduces bias or reflects precisely the spectrum of starting DNA. We analyzed the origins of discrepancies in KRAS (Kirsten rat sarcoma viral oncogene homolog gene) mutation detection in six of ten samples amplified using the GenomePlex® Tissue Whole Genome Amplification kit 5 (WGA5; Sigma‐Aldrich, St. Louis, MO, USA) and KRAS StripAssay® (KRAS SA; ViennaLab Diagnostics, Vienna, Austria). We undertook reextraction, reamplification, retyping, authentication, reanalysis, and reinterpretation to determine whether the discrepancies originated during the preanalytical, analytical, and/or interpretative phase of genotyping. We conclude that a combination of glass slide/sample heterogeneity and biased amplification due to stochastic effects in the early phases of whole genome amplification (WGA) may have adversely affected the results obtained. Our findings are relevant for both forensic genetics testing and massively parallel sequencing using preamplification.     

A stereoselective total synthesis of the HCl salts of mycestericins F,G and ent-F

The total synthesis of the HCl salts of two natural sphingolipid-related amino acid derivatives, mycestericins F 4 and G 5 together with unnatural ent-4·HCl, starting from the four crucial scaffolds 6, 8, 9, 11 and utilizing the Wittig reaction to build the C₂₀ backbone, has been achieved. The selection of selective functional group interconversions accompanied with suitable protection–deprotection protocols in the coupling products 20 and 34 gave the desired structures.