Abstract: Adsorption is one of the important techniques in arsenic removal from aqueous solutions. In this study, the As removal efficiency of Leonardite char by a prepared Leonardite carbonized at 450ºC was investigated as a function of solution pH, contact time, kinetic and As(III) or As(V) concentration. The surface complexation modeling was used to describe As(III) and As(V) adsorption on the minerals which found in Leonardite char. In the batch experiment, 10.0 mg/L As(III) or As(V) pH 7.0 and 50 mL of aqueous solution was as high as 90% adsorbed. The results showed that Leonardite char could be used as effective adsorbent for the removal of arsenic from aqueous solution. This research supports effort to water with arsenic level lower than 10 mg/L. The maximum adsorption capacity was calculated by fitting the Langmuir and Freunchlich equations to the adsorption isotherms. The Leonardite char will be used as a low-cost adsorbent, for arsenic ions removal in water.
Abstract: A simple, rapid, selective and highly sensitive spectrophotometric method is described for the quantitative determination of the tricyclic antidepressant drugs, desipramine hydrochloride (DPH), clomipramine hydrochloride (CPH) and imipramine hydrochloride (IMH) in pure and in pharmaceutical preparations. The proposed method is based on the bromination of above drugs with known excess of bromine. The unreacted bromine is determined based on its ability to bleach the dye Eiochrome blue black R quantitatively at 530 nm for all the three drugs obeying Beer's law in the range, 0.0 - 8, 0.0 - 10 and 0.0 - 9.0 μg ml-1 for DPH, CPH and IMH, respectively. The molar absorptivity values were found to be 1.61 x 10(4), 1.62 x 10(4) and 1.57 x 10(4) l mol-1cm-1, respectively with the corresponding Sandell's sensitivity values 0.0187, 0.0216 and 0.0202 μg cm-2. The limits of detection and (LOD) and quantification (LOQ) are also reported for the developed method. Intra- and inter-day precision and accuracy of the method were established according to the current ICH guidelines. Applications of the procedure to the analysis of various pharmaceutical preparations gave reproducible and accurate results. Further, the validity of the procedure was confirmed by applying the standard addition technique and the results were evaluated in terms of Student's t-test and variance ratio F-test to find out the significance of proposed method over the reference method.
Abstract: An ionic exchange high resolution liquid chromatography (IE-HPLC) method for determination of cations and anions in interstitial water of sediments, affluent and effluent of dams is proposed in this paper. Cations: Na+, Ca2+, K+, and Mg2+ and anions: Cl-, CO3(2-), NO3- and SO4(2-) were analyzing by IE-HPLC method. Optimized analytical conditions were validated in terms of accuracy, recovery and detection limit. The method of flame spray atomic absorption spectrophotometer (AAS) was used as an additional method for the determination of Ca and Mg. It must be indicated that cations may be analyzed by several analytical methods such as AAS, ICP, etc., but there are not enough methods to analyze anions; IE-HPLC methods are good alternative to determine these ions. The aim of this study was to determine ions in interstitial water in the affluent and effluent of the Chilean dams Cogotí, Corrales, La Paloma, Rapel and Recoleta in order to determine if the water is suitable for irrigation or human consumption and estimate the effect of dams on water quality. The results indicate that the highest concentrations observed were for the cations: Ca2+ (mean 43.5 mgL-1), Na+ (mean 16.4 mgL-1), Mg2+ (mean 12.6 mgL-1), and K+ (mean 2.3 mgL-1). The highest concentration of anions was found for CO3(2-) (mean 55.9 mgL-1); the concentrations of SO4(2-), Cl- and NO3- reached 59.3 mgL-1, 12.8 mgL-1 and 27.0 mgL-1, respectively. The results indicate that although the origin of soluble salts is lithogenic, the high concentrations of these salts found in some places indicate anthropogenic effect, either by direct or indirect discharges or by diffuse pollution. These high concentrations may be significant, considering that these waters are used mainly for irrigation, which would affect the quality of agricultural soils irrigated with this moderately saline water.
Abstract: The effect of virgin heterophasic PP copolymer (vPP) content on moisture absorption, as well as on thermal and mechanical properties of recycled polyethylene/ wood flour composites was investigated. The polymer matrix of recycled post-consumed plastic waste (rPE) was composed of a matrix of LDPE and a part of PP. Wood flour of Pinus radiata was used as filler at a constant loading of 45 wt.%. rPE/vPP blends and their composites were manufactured by melt blending, and then by injection molding. The morphology of the blends and composites was analyzed by means of scanning electron microscopy. The addition of vPP improved tensile and flexural moduli and flexural strength of wood plastic composites (WPC). The highest increase of these properties was observed for a WPC sample with a rPE/vPP ratio of 19. WPC made with higher virgin PP content (rPE/vPP ratio = 9 and 5.7) showed lower increase of mechanical properties compared to polymer matrix and WrPE samples. The moisture uptake of WPC made of rPE/vPP blend was higher than those of rPE, and their mechanical properties were more adversely affected by immersion in water. TGA results indicate that rPE are thermally more stable than rPE/vPP blends. The incorporation of heterophasic PP copolymer into the recycled polymer matrix of WPC delays the starting of wood flour degradation.
Abstract: The synthesis of 3-aryl-5-pentyl-1,2,4-oxadiazoles from carboxylic acid esters and arylamidoximes in the presence of potassium carbonate is described. The reaction was carried out in a microwave oven without any solvent in much shorter time and in good yields. The structures of the synthesized compounds were elucidated using IR, ¹H and 13C NMR spectroscopy and elemental analysis and their antiproliferative activities was evaluated against three different human cell lines.
Abstract: The aim of the present study was to analyzed chemical constituents of the essential oil, obtained by hydro distillation of the roots of Crassocephalum crepidioides (Benth.) S. Moore. The oil was analyzed using gas chromatography equipped with flame ionization detector (GC-FID) and gas chromatography coupled with mass spectrometry (GC/MS). Forty-seven compounds were identified, representing 93.2 % of the total oil. The main constituents were (E)-β-farnesene (30.6%), α-humulene (10.3%), β-caryophyllene (7.2%), cis-β-guaiene (6.1%) and α-bulnesene (5.3%). The oil was constituted mainly of sesquiterpene hydrocarbons (77.6%), followed by oxygenated sesquiterpenes (8.7%), oxygenated monoterpenes (3.5%), monoterpene hydrocarbons (2.8%) and phenyl derivatives (0.6%). This is the first report on the essential oil composition of the roots of C. crepidioides.
Abstract: In recent years Chile has experienced a significant increase in mining activities, which has resulted in an increase in waste generation. The dispersion of these residues in the air, water and soil has led to negative changes in the environment. This main objective of this study is to identify the influence of the copper mine Los Pelambres (station E2) located in the Choapa River Basin (IV Region Coquimbo). To achieve this goal we performed an analysis of the physical and chemical composition of sediment samples in the summer season taken from the rithron to potamon areas of the watershed. River sediments can provide information and influence the degree of pollution in a given area due to mining discharges. The analysis was based on two types of determinations: total metal content, which provides an assessment of the level of contamination, and studies of different chemicals in which the metal is associated with the sediment. The results of this study showed that station E2 (Cuncumen River) has a particular behavior in the basin, showing higher content of metallic trace elements; for example, the concentration of Cu (total fraction) was 4814.1 μgg-1. In the rest of the stations the metal content was less than in E2 (total Cu from 42.4 μgg-1 in E1 to 136.2 μgg-1 in E5), therefore it is concluded that there is no direct influence of the mining activity of Los Pelambres station (E2) in the rest of the basin. BCR sequential extraction of sediments, developed under the auspices of the Community Bureau of Reference, indicated metal mobility. Metal mobility is closely associated with the chemical conditions of the system. In general, metals that could have greatest mobility in the basin are: Cu, Cd, Zn and Mn, found in the soluble acid fraction, together with oxidant (organic matter) and reducing (Fe and Mn oxides) conditions. The cluster analysis of the total fraction of metal content in sediments indicates that the mine discharge site (E2), has a unique behavior in the basin. Station E2 showed a similarity below 50%, while the rest of the basin showed a similarity above 70%. Overall the results indicate that the Los Pelambres Mine is not a direct source of heavy metals in the Choapa River Basin, which does not imply that station E2 (Cuncumen River) has no influence on the metal content of sediments. To determine the area of this season, the study area should be narrowed to Cuncumen River (E2) section of the Choapa River Basin, since the physical conditions of the system, hydrographic conditions and climatic do not allow a high rate of discharge and mobility of heavy metals from the mining area with high discharge to the last station (Huentelauquen).
Abstract: Lignocellulosic biomass (LB) has been recognized as potential raw for bioethanol production. To facility LB bioconversion a pretreatment is applied, followed by simultaneous or separated saccharification and fermentation (SSF or SHF, respectively) steps. Characterization of pretreated materials, needed to evaluate their ethanol yields, involves laborious and destructive methodologies. Therefore, saccharification is also time consuming and expensive step and some pretreated samples have not suitable characteristics to obtain high ethanol yields. Since bioethanol production aims to be a multivariable process respect to lignocellulosic resources, this work attempts to use NIR spectroscopy as alternative to wet chemical analysis to characterize samples from multiple pretreatments and lignocellulosic resources simultaneously and estimate their ethanol yield after a SSF process using multivariate calibration. Selection of suitable samples to obtain high ethanol yields using a classification method is also evaluated. Partial least squares (PLS) and discriminant partial least squares (PLS-DA) were used as calibration and classification techniques, respectively. Results showed ability of NIR spectroscopy to predict the chemical composition of samples and their ethanol yields, even if different lignocellulosic materials were used in the models, with low prediction errors and high correlation coefficients with reference methods (r>0,96) in PLS models and low misclassification rates (20- 30%) in classification models. Use of these models could facility the fast selection of high number of samples with suitable characteristics to obtain high ethanol yields and as predictive tool of these ethanol yields after a SSF process under controlled conditions.
Abstract: Ammonium nickel sulphate [(NH4)2SO4.NiSO4.6H2O] was found as a new catalyst to synthesis 2-aryl benzimidazole, 2-aryl benzothiazole and 2-aryl benzoxazole in aqueous media under sonication irradiation. The procedure is an eco-friendly, efficient and provides simple workup and good yield.
Abstract: A new ionic liquid (IL) based micro-extraction method was developed for the spectrophotometry and spectrofluorometry determination of curcumin in curry products. ILs can effectively extract curcumin from aqueous solution which were used instead of large-scale organic solvents to reduce environmental pollution and production cost. Results show that the fluorescence of curcumin is considerably enhanced in 1-hexyl-3-methylimidazolium hexafluorophosphate ([Hmim][PF6]). Under optimized conditions, the absorbance of curcumin is proportional to the concentration of curcumin in the range of 18.4 ng/mL to 494 ng/mL, and the detection limit is 6.1 ng/mL. In addition, the fluorescence intensity of curcumin is proportional to the concentration of curcumin in the range of 0.050 ng/mL to 120.1 ng/mL, and the detection limit is 0.002 ng/mL. Therefore, an efficient spectrophotometry and spectrofluorometry method for the determination of curcumin was established, and the actual concentration in curry products was satisfactorily determined. The content of curcumin in curry sauce were 14.10±0.40 and 14.32±0.37 mg/g when using the spectrophotometry and spectrofluorometry, the content of curcumin in curry powder were 2.50±1.73 and 2.75±1.40 mg/g when using the spectrophotometry and spectrofluorometry.
Abstract: Two adducts SF4AsF5 and SF4SbF5 have been studied in this work. Their structures, thermodynamic functions, and heats of formation were studied using density functional theory (DFT) method in gas phase and using the force field method and the DFT GGA-RPBE method in crystal state. The obtained crystal structures have the P2(1)lc space group. The lattice energies, sublimation enthalpies and heats of formation in crystal state were estimated. Based on the optimized crystal structures, the electronic energy band and density of state were predicted and the results indicate that they are semiconductors with the band gap between 2.3 ~ 2.5 eV.
Abstract: The mechanism of the Diels-Alder reaction of 1-(2-furyl)-3-(dimethylamino)-2-propene-1-thione with various dienophiles resulting in the formation of 2H-thiopyran derivatives were discussed by evaluating global and local electrophilicity and nucleophilicity descriptors for whole series of diene and dienophiles at B3LYP/6-31G* level of theory. The results preluded that the polarity and charge transfer flow between diene and dienophiles was consistent with the global reactivity descriptors and substitutional pattern. The local descriptors based on Parr functions proposed by Domingo were found to be quite promising to explain the regioselectivity of cycloaddition processes. For symmetrical dienophiles viz., 2, 5, 8, 11a, 11b, 13 and 14 the local descriptors concentrates equally (50%) at both interacting sites, to allocate non-regioselective cycloadditions. However, unsymmetrical dienophiles 16,18a-e and 21 have shown a preference towards a particular regioisomer and shown high regioselectivity during cycloaddition reaction. Regional nucleophilicity at the interacting site of diene were evaluated using local nucleophilicity descriptor Nk. These outcomes were found to be in exact correlation with the experimental outcomes achieved by Bogdanowicz et al.
Abstract: The synthesis and characterization of the Fe(III) complex of sulfathiazole, is presented herein. The compound was prepared by using a conventional precipitation technique, and was characterized by thermogravimetric analysis (TGA), differential thermal (DTA), differential scanning calorimetry (DSC) under oxygen atmosphere, chemical analysis, infrared spectroscopy, powder ray-X diffraction (PXRD), and scanning electron microscopy (SEM). The antibacterial activity of the complex was screened against S. aureus, showing an appreciable activity, compared with the free ligand.
Abstract: Aluminium sulfate has mild acidity, yet the acidity of aluminium sulfate is not taken advantage of in organic synthesis. Here, we utilized aluminium sulfate for the first time in a multicomponent reaction for the synthesis of polyhydroquinoline. A four-component one-pot synthesis of polyhydroquinoline was carried out by condensing dimedone, aromatic aldehyde, ethyl acetoacetate, and ammonium acetate using a catalytic amount of aluminium sulfate (10%) refluxed in ethanol. The present protocol using aluminium sulfate a mild solid catalyst has several merits, such as low cost, high yield, and shorter reaction time, with no byproducts.
Abstract: A series of 3,4-dihydropyrimidin-2(1H)-one(thione) derivatives was synthesized using Co(NO3)2.6H2O in solvent-free condition. Avoiding organic solvents during the chemical reactions leading to an economic approach is effective. The reaction is characterized by high efficiency, short reaction time, high yields, simple experimental procedure, availability of catalyst and environmentally friendly reaction conditions.
Abstract: A kinetic spectrophotometric method based on the initial rate measurement has been developed for the determination of N-acetyl L-cysteine. The developed method is based on the oxidation of N-acetyl L-cysteine with iodate. The reaction product was studied and characterized using the mass spectrometry and the structure of the product was proposed. From the mass spectrometric studies it was concluded that the oxidation of the drug resulted in the formation of a disulfide. The developed method was validated as per the guidelines of international conference on harmonization. The developed initial rate method was found to be linear in the concentration range of 1.25 - 30 µg ml-1. The detection and quantitation limits were found to be 0.018 and 0.056 µg ml-1. In the current study, the degradation product of N-acetyl L cysteine was also prepared and identified using mass spectrometry.
Abstract: We report two selective morphologies of CaCO3 crystals using poly(potassium 2-acrylamido-2-methylpropanesulfonate) [poly(KAMPS)] as template through gas diffusion method. The presence of anionic sulphonte groups on poly(KAMPS) determined the kinetic crystallization and was fundamental for stabilizing oriented triangle and tubular shape of calcite. The modified CaCO3 were followed by SEM and XRD techniques. Inorganic architectures with hierarchically complex shape and optimized properties have great potential as agents in optical, electronic, magnetic and biomedical applications.
Abstract: The crystalline structure of spinels is extremely flexible due to the presence of several sublattices in which the cations can be distributed and localized in different crystallographic sites depending on their sizes, oxidation states or coordination numbers. Cationic substitution and ions-extraction are appropriate tools to change the oxidation state inside the spinel structure, thus substantially modifying the magnetic properties. The spinel sulfide CuCr2S4 is a metallic ferromagnet with T C = 377 K, where Cr is mixed-valence Cr3+/Cr4+, while CuTi2S4 is a Pauli paramagnet, with Ti in a mixed-valence state (singlet ground state for Ti3+; nonmagnetic, S = 0, state for Ti4+). The copper ion Cu+ is in a closed-shell configuration. The mixed spinel CuCr2-xTi xS4 gives the possibility to change the oxidation state of Cr ions when titanium ions are introduced. Another way to control the oxidation state of the ions is by copper extraction from the lattice, thus producing a change in the magnetic behavior of the material. We report the synthesis, crystallographic and magnetic properties of the solid solution CuCr2-xTi xS4 and its deficient-spinel structure obtained by copper extraction. Powder samples of CuCr2-xTi xS4 were prepared in quartz ampoules at 900 °C. Deficient spinels Cu1-y□yCr2-xTi xS4 were prepared by mild treatment with oxidizing agents such as iodine in acetonitrile at 50 °C.
Abstract: The Luffa acutangula Var. amara (Cucurbitaceae) is climbing shrub; commonly known as wild ridge gourd. Its aerial parts are used traditionally in diverse health ailments. Four successive extracts of L. amara pericarp (LAP) were evaluated for antioxidant using in vitro for DPPH, ABTS, superoxides radical, reducing power and phosphomolybdenum assay. The bioactive ethanol extract was evaluated for immunomodulatory activity by in vivo phagocytosis using carbon clearance and neutrophil adhesion test. The bioactive ethanolic extracts showed potent in vitro antioxidant ability, increased phagocytic index (0.028 ± 0.002), and increased the % neutrophil adhesion (24.63 ± 0.87%). Furthermore, the potent plant phenolics such as gallic acid and p-hydroxybenzoic acid were isolated and identified spectroscopically. The presence of these plant phenolics and like constituents would be responsible for their potent antioxidant and immunomodulatory activity.
Abstract: This study is concerned to elucidate the interaction behavior of films consisted of gelatin and carboxymethylcellulose, which are polyelectrolytes and have applications in tissues engineering. These films were chemically cross-linked using glutaraldehyde. The decrease of framework in triple helix of gelatin in the presence of polysaccharide and/or the cross-linking agent increases until a total disappearance was showed by XRD, the disappearance of macroporous gelatin structure in the presence of additives has been confirmed by SEM and AFM. According to DSC analysis, glass transition temperature (Tg) increases and decreases as GTA and CMC were added, respectively. It was shown that swelling of macroporous structure in pseudophysiological mediums was more absorbent and used electrolytes exert an osmotic pressure or ionic strength inducing higher swelling. Also, it was found that diffusion mechanism is directly related to gelatin structure. On the other hand, the incorporation of CMC improves the flexibility of matrice.
Abstract: Synthesis of flavones from 2'-allyloxy-α, β-dibromochalcones has been described. The iodine induced oxidative cyclization of 2'-allyloxy-α, β-dibromochalcones results into the formation of 3-bromoflavanones which ultimately gives flavones. Dehydrobromination of 3-bromoflavanone to give flavone is the preferred reaction over dehydrogenation.
Abstract: Among the secondary metabolites of pharmacological, chemical and biotechnological interest, triterpenoidal compounds are widely distributed throughout the fungi kingdom. Triterpenoids produced by species of the genus Pleurotus, basidiomycetes characterized by their important biological actions and excellent nutritional quality, can be obtained by fermentation processes that stimulate the production of the bioactive compounds. This study evaluates the effect of using 12 non-conventional carbon sources (CS) on the production of triterpenoids from 3 Pleurotus species: P. ostreatus, P. djamor and P. pulmonarius obtained in submerged culture. The variations found among these species with regard to their quantities and structural differences were dependent on the CS as well as the species, and it was concluded that the cultivation of the mycelium of P. pulmonarius with wheat bran promotes the production of the compounds of interest. In addition no direct influence of the C/N ratio of the substrate on the biosynthesis of the triterpenoids was observed, as reported in the case of other secondary metabolites such as polysaccharides and statins.
Abstract: Sulfonic acid functionalized SBA-15 (SBA-Pr-SO3H) with a pore size of 6 nm is an efficient catalyst in the green three-component condensation of phthalhydrazide, dimedone and aldehydes to give 2H-indazolo[1,2-b]plithalazine-triones under solvent-free conditions in excellent yields and short reaction times.
Abstract: A series offive new 4-phenyldiazenyl-4'-[(4-chlorobenzyl)oxy]biphenyls have been synthesized by condensing different sodium salts of some 4'-phenyldiazenyl-biphenyl-4-ols with 1-chloro-4-(chloromethyl)benzene. These compounds have been characterized by elemental analysis (C, H, N) and electronic, IR, ¹H NMR and mass spectrometry studies. The obtained compounds were assayed for their antibacterial activity against some bacteria by disk diffusion method.
Abstract: Five spectrophotometric methods for determination of Amitriptyline HCl have been developed, validated and applied for the assay of the drug in pharmaceuticals. Methods A, B and C are based on ion pair complexation of drug, in acidic buffers, with triphenylmethane dyes viz., Bromothymol blue (BTB), Bromophenol blue (BPB) and Bromocresol purple (BCP). The complexes are extracted into chloroform and absorbance is measured around at 415 nm as function of concentration of the drug. The stoichiometry of the complex is found 1:1 in each case. Method D depends upon charge transfer complexation of neutralized drug with iodine which produces iodide ion whose absorbance at 366 nm is measured as function of concentration of the drug. This complex, too, has 1:1 composition as determined by Job's method. Method E is developed on the basis of oxidation of the drug with alkaline KMnO4 which generates green colored manganate ion with λmax 610 nm. As the intensity of green color increased with increasing time kinetics of the reaction is followed and calibration curves are constructed by using initial rate and fixed time methods. Excellent recovery studies with high accuracy and precision indicate that the methods can be successfully used in industries for the assay of drug in pure form and pharmaceuticals.
Abstract: Aminomethylated polystyrene (PSCH2-NH2) reacts with 3-ethoxysalicylaldehyde in equimolar amounts to produce monobasic bidentate (ON donor) polystyrene-anchored Schiff base (PS-LH). The latter upon refluxing with metal the ions in 1:2 molar ratios gives polystyrene-anchored coordination compounds of types: [PSCH2-LM(OAc)(DMF)] (where M = Cd, Co, Cu, Zn, UO2), [PSCH2-LNi(OAc)(DMF)3], [PSCH2-LFeCl2(DMF)2], [PSCH2-LMCl(CH3OH)] (where M = Cd, Zn) and [PSCH2-LMoO2(acac)]. The polystyrene-anchored compounds have been characterized on the basis of elemental analyses, spectral (IR, reflectance, ESR) and magnetic susceptibility measurements. The polystyrene-anchored Co(II), Cu(II), Ni(II) and Fe(III) compounds are paramagnetic, while others are diamagnetic. Co(II) and Cu(II) compounds are square-planar; Zn(II) and Cd(II) compounds are tetrahedral; Ni(II), Fe(III), MoO2(VI) and UO2(VI) compounds are octahedral.
Abstract: In the present article, a simple, rapid, selective, sensitive and economical method has been developed for the separation/preconcentration of the trace amounts of Pd(II) in different real samples using alumina coated magnetite nanoparticles modified by sodium dodecyl sulfate and its determination by flame atomic absorption spectrometry after eluting with 1.0 mol L-1 thiourea. Under the optimal experimental conditions, the preconcentration factor, detection limit, linear range and relative standard deviation of Pd(II) were 280 (for 700 mL of sample solution), 4.3 ng mL-1, 6.0 - 120.0 ng mL-1 and 4.6% (for 10 ng mL-1, n=10), respectively.
Abstract: In this work we have performed a QSAR study of atmospheric reactions with hydroxyl radical, at the B3LYP level of theory with 6-31G(d) basis set. Molecular descriptors selected by applying multiple linear stepwise regression (MLR) analysis were used to predict the reaction rate constants (-logkOH) of OH radicals with organic compounds in the atmosphere, including 98 alkenes and 80 aromatic compounds. For setting our reactions, we have calculated 98 alkenes and 80 aromatic compounds. A four-descriptor MLR model (rms = 0.102 and R²= 0.938) for 98 alkenes was developed based on the number of R=CHX functional group counts, E HOMO parameter, and Fukui indices of the double-bonded C atoms. We found vinyl chemicals with conjugated double bonds and electron-donor substituents are the most reactive systems; while alkenes with multiple halogen substitutions are the least reactive molecules. Additionally, a three-descriptor MLR model (rms = 0.282 and R²= 0.910) was built to predict OH radical rate constants for 80 aromatic compounds, which was dominated by the E HOMO parameter, a topological descriptor for steric hindrance, and the most positive net atomic charge on hydrogen atoms. Aromatics with electron-donor and electron-acceptor groups, respectively, possess high and low degradation rates. The halogen aromatics are less reactive, especially for aromatics with multiple halogen substitutions. In comparison to existing models, the two models obtained in this paper show better statistical quality.
Abstract: Polypropylene composites with 5 to 10% of SiO2, Al2O3 y TiO2 nanoparticles were synthesized. The oxides were obtained using the sol-gel technique and were added to the molten polypropylene. The morphology of nanoparticles was observed by scanning electron microscopy and showed that the incorporation of TiO2 and SiO2 gels produces high dispersion of the filler, while the use of Al2O3 results in aggregates of these nanoparticles in the polymer matrix. The X-ray diffractogram of the composites revealed a displacement of characteristics lines of polypropylene and an increment of the interplanar spaces, indicating some interaction between the components and the predominance intercalation of oxides. Through FT-IR it was noticed the presence of functional groups attributable to the filler nanoparticles. The crystallization, the fusion behaviour and the thermal stability of the composites was studied using differential scanning calorimetry and thermogravimetric analysis it was found a reduction in the crystallization temperature and increment in the thermal stability of the polypropylene matrix due to the action of the silica, alumina an titania nanoparticles.
Abstract: The present work deals with copolymers synthesized by reacting aniline units or blocks with 2,6-di(thiophen-2-yl)aniline and 2,2'-(thiophen-2,5-diyl)dianiline monomers. Characterization by spectroscopic techniques such as FT-IR, UV-vis, 1H-NMR corroborated the formation of true copolymers. Synthesized products showed improved solubility and better photovoltaic efficiency than the respective homopolymers. The latter is due to the presence of a greater number of quinoid units, capable of promoting charge carriers generation. However, the low mobility of the charge carriers, that increases copolymers resistivity, would be responsible for an efficiency improvement of just one order of magnitude with respect to the homopolymers.
Abstract: A commercial ammonia solution was introduced in the buffer gas of an ion mobility spectrometer and the mobilities of tetramethylammonium (TMA), tetraethylammonium (TEA), tetrapropylammonium (TPA), and tetrabutylammonium (TBA) ions, tribenzylamine (TBzA), tributylamine (TBtA), 2,4-dimethyl pyridine (2,4-lutidine), 2,6-di-tert-butyl pyridine (DTBP), serine, atenolol, and valinol decreased depending on their structures. Electrospray ionization-ion mobility spectrometry-quadrupole mass spectrometry was used in these experiments. Analyte ion mobilities decreased to different extents with the amount of ammonia introduced in the mobility spectrometer. When the amount of ammonia increased from 0.0 to 22 mmol m-3 (with a concomitant concentration of water of 106 mmol m-3), percentage reductions in mobilities were: -4.8% (serine), -1.9% (reactant ions), -1.1% (TBtA), -0.9% (TBzA), -0.5% (TEA), -0.4% (valinol and TBA), -0.3% (TEA, TMA, and 2,4-lutidine), and 0% (atenolol and DTBP). These selective variations in mobilities were due to formation of large analyte ion-ammonia-water clusters. The small change in mobility of tetraalkylammonium ions, TBzA, TBtA, atenolol, and DTBP with the introduction of ammonia into the buffer gas was explained by steric hindrance of bulky substituents which shielded the positive charge of the ion from the attachment of ammonia and water molecules, and delocalized the positive charge. Ammonia in the buffer gas produced ion clusters with one or two ammonia molecules in compounds with little steric hindrance such as serine. At concentrations of ammonia of 4.4 mmol m-3 or higher (at 150°C), ligand-saturation with ammonia and water molecules occurred on the positive charge of some ions; when the positive charge saturated, no significant reductions in ion mobility occurred when increasing the concentration of ammonia in the buffer gas.
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