Synthesis of new donor-acceptor polymers containing thiadiazoloquinoxaline and pyrazinoquinoxaline moieties: low-band gap, high optical contrast, and almost black colored materials

Two low band gap conjugated polymers, poly[4,9-bis(4-hexylthien-2-yl)-6,7-di(thien-2-yl)-[1,2,5]thiadiazolo[3,4-g]quinoxaline] (PHTTQ) and poly[5,10-bis(4-hexylthien-2-yl)-2,3,7,8-tetra(thien-2-yl)pyrazino[2,3-g]quinoxaline] (PHTPQ), consisting of alternating electron-rich 3-hexylthiophene and electron-deficient 6,7-di(thien-2-yl)-[1,2,5]thiadiazolo[3,4-g]quinoxaline (TTQ) and 2,3,7,8-tetra(thien-2-yl)-2,3-dihydropyrazino[2,3-g]quinoxaline (TPQ) units were synthesized electrochemically. The structures of the π-conjugated monomers were tailored using thiophene as the pendant group on the acceptor units (TTQ and TPQ). The electrochemical and optical properties of the polymers were investigated by cyclic voltammetry and UV-vis-NIR spectroscopy. The absorption spectra of PHTPQ, revealing a 1.0 eV band gap, exhibited three maxima at 352 nm, 535 nm, and 750 nm. Consequently, its absorption spectra cover the region between 400 and 800 nm, which make the polymer almost black in appearance. PHTTQ shows a λ_max value of 820 nm and a band gap of 0.8 eV which is very low among other [1,2,5]thiadiazolo[3,4-g]quinoxaline-containing donor-acceptor type polymers.     

Determination of some phthalate acid esters in artificial saliva by gas chromatography-mass spectrometry after activated carbon enrichment

The determination of six phthalate acid esters was achieved in artificial saliva using gas chromatography-mass spectrometry following activated carbon enrichment of samples. Central composite experimental design was applied to optimize method parameters, such as pH, adsorption time and amount of activated carbon. The best compromise of analytical conditions for the simultaneous determination of analytes from spiked artificial saliva were found to be: pH (3), adsorption time (30 min), activated carbon amount (1.8 g L⁻¹) and elution solvent (chloroform). These conditions were applied to study the migration of phthalate acid esters from different children's toys into saliva. A horizontal agitation method was applied to extract the analytes from plastic toys into saliva for 2 h at 37 °C. The detection limits of the method were in the range of 1.3-5.1 μg L⁻¹, while the relative standard deviation (%) values for the analysis of 100 μg L⁻¹ of the analytes were below 3.0% (n = 5). Di-2-ethylhexyl phthalate was the main analyte found in these samples.     

Partial purification and characterization of protease enzyme from Bacillus subtilis and Bacillus cereus

The aim of this experimental study was to isolate and partially purify protease enzyme from Bacillus cereus and Bacillus subtilis. Protease enzyme is obtained by inducing spore genesis of bacteria from Bacillus species in suitable nutrient plates. The partial purification was realized by applying, respectively, ammonium sulfate precipitation, dialysis, and DEAE-cellulose ion-exchange chromatography to the supernatant that was produced later. Optimum pH, optimum temperature, pH stability, and temperature stability were determined, as well as the effects of pH, temperature, substrate concentration, reaction time, and inhibitors and activators on enzyme activity. In addition, the molecular mass of the obtained enzyme was investigated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The specific activity of partially purified enzyme from B. subtilis was determined to be 84 U/mg. The final enzyme preparation was eight-fold more pure than the crude homogenate. The molecular mass of the partially purified enzyme was found to be 45 kDa by using SDS-PAGE. The protease enzyme that was partially purified from B. cereus was purified 1.2-fold after ammonium sulfate precipitation. The molecular mass of the partially purified enzyme was determined to be 37 kDa by using SDS-PAGE.     

Using a similarity measure for credible classification

This paper concerns classification by Boolean functions. We investigate the classification accuracy obtained by standard classification techniques on unseen points (elements of the domain, {0,1}ⁿ, for some n) that are similar, in particular senses, to the points that have been observed as training observations. Explicitly, we use a new measure of how similar a point x∈{0,1}ⁿ is to a set of such points to restrict the domain of points on which we offer a classification. For points sufficiently dissimilar, no classification is given. We report on experimental results which indicate that the classification accuracies obtained on the resulting restricted domains are better than those obtained without restriction. These experiments involve a number of standard data-sets and classification techniques. We also compare the classification accuracies with those obtained by restricting the domain on which classification is given by using the Hamming distance.     

Experimental and theoretical studies on the functionalization reactions of 4-benzoyl-1,5-diphenyl-1H-pyrazole-3-carboxylic acid and acid chloride with 2,3-diaminopyridine

The 1H-pyrazole-3-carboxylic acid 2 was converted in good yield (69%) into the corresponding 1H-pyrazole-3-carboxamide 5 via reaction of the acid chloride 3 with 2,3- diaminopyridine (4). A different product, the 3H-imidazo[4,5-b] pyridine derivative 6, was formed from the reaction of 3 with 4 and base in benzene for 5 hours. The structures of the synthesized compounds were determined spectroscopically. The mechanism of the reaction between 3 and 4 was examined theoretically.     

Flow injection determination of catechol based on polypyrrole–carbon nanotube–tyrosinase biocomposite detector

A flow injection catechol biosensor based on tyrosinase entrapped in carbon nanotube modified polypyrrole biocomposite film on a glassy carbon surface has been developed. Amperometric response was measured as a function of concentration of catechol, at a fixed bias voltage of −50 mV at a flow rate of 1 mL/min. The proposed biosensor exhibited impressive analytical performance such as a linear range between 3 and 50 μM, a short response time (10 s), a detection limit of 0.671 μM and an excellent operational (with a relative standard deviation of 0.54%) and long-term stability (85% remained after 10th week). A comparison of the analytical parameters of the developed biosensor with polypyrrole/tyrosinase film electrode was performed in the study. CNT was shown to enhance the electron transfer between the electrode and enzyme and capable to carry higher bioactivity owing to its intensified surface area.     

Accurate,sensitive determination of omega-6 and omega-3 polyunsaturated fatty acids in human plasma,urine samples

Quantitative determination of omega-6 and omega-3 polyunsaturated fatty acids in human plasma and urine with high accuracy and precision provides significant information to monitor the underlying etiology of several diseases. In this regard, liquid chromatography-mass spectrometry is a good choice owing to its great selectivity and sensitivity. Additionally, the hybrid quadrupole–time of flight–mass spectrometer systems provides easy identification of target compounds with superior mass measurements. In this study, an analytical method has been developed for simple, accurate and simultaneous determination of linoleic acid, arachidonic acid, docosahexaenoic acid and eicosapentaenoic acid in a short chromatographic analysis period. The developed method is suitable for the quantitative detection of these four compounds with detection limits ranging between 1.1–3.0 ng ml⁻¹ and its applicability was assessed in human urine and plasma samples. As a result, acceptable accuracy (between 83 and 111%) and good precision (<6%) were obtained for target compounds using matrix matching calibration strategy.     

Interactions of Imidazolium Based Ionic Liquids with Water Studied by Density and Speed of Sound Measurements: Effect of the Chain Length of an Alkyl Substituent on the Imidazolium Ion

Densities and speeds of sound of three ionic liquids (ILs), 1-ethyl-3-methyl imidazoliumtetrafluoroborate (C₂mimBF₄), 1-butyl-3-methylimidazoliumtetrafluoroborate (C₄mimBF₄) and 1-hexyl-3-methylimidazoliumtetrafluoroborate (C₆mimBF₄) were measured in aqueous solutions at (288.15, 293.15, 298.15, 303.15 and 308.15) K. These data were used to calculate the volumetric properties apparent molar volume and apparent molar isentropic compression as a function of molality. Infinite dilution values for these properties were evaluated by an extrapolation procedure based on Redlich–Meyer type equations. Apparent molar isobaric expansions at infinite dilution were also obtained from the slopes of the apparent molar volume at infinite dilution versus temperature. All these properties are interpreted in terms of IL–water interactions. The hydrolysis of the \( {\text{BF}}_{4}^{ - } \) anion of the ILs and its effects on the results is discussed.     

Sterically hindered N-aryl/benzyl substituted piperidoimidazolin-2-ylidene palladium complexes and their catalytic activities

A series of N-aryl (2a,b) or benzyl (2c,d) substituted piperidoimidazolinium salts and their palladium complexes (3a-d) were prepared and characterized by ¹H, ¹³C NMR, IR spectroscopy and elemental analysis. The crystal structures of 3a and 3c have been determined by X-ray crystallography. Thermogravimetric analysis (TGA) was applied to complexes (3a–d). The palladium complexes have been employed as catalyst for Suzuki-Miyaura cross coupling. The N-aryl substituted complex 3b was a highly efficient precatalyst and successfully employed in Suzuki-Miyaura cross coupling reactions of (hetero)aryl chlorides with arylboronic acids in air. In addition, the oxidative addition step of the reaction mechanism involving chlorobenzene and the catalysts 3a, 3b, 3c and 3d were computationally investigated by the DFT-$\omega$-B97X-D method and complete agreement were obtained with the catalytic results. To measure σ-donating and π-acceptor properties of the new ligands, the rhodium carbonyl complexes were also prepared.