Thermal and spectroscopic investigation of europium and samarium sulphates hydrates by TG-FTIR and ICP-MS techniques

The investigation of europium(III) sulphate hydrate and samarium(III) sulphate hydrate was performed by thermal analysis (TG-DTG) and simultaneous infrared evolved gas analysis-Fourier transformed infrared (EGA-FTIR) spectroscopy. The TG, DTG and DTA curves were recorded at the 25–1400 °C in the dynamic air atmosphere by TG/DTA analyser. The infrared evolved gas analysis was obtained on the FTIR spectrometer. Eu₂(SO₄)₃·nH₂O (n = 3.97) and Sm₂(SO₄)₃·nH₂O (n = 8.11) were analysed, the dehydration and decomposition steps were investigated and the water content was calculated. The formation of different oxysulphates was studied.

The trace rare earth elements in Eu and Sm sulphates were determined by ICP-MS. The concentration of trace Eu, Sm, La, Gd, Y and Ce ranged from 3.9 × 10⁻⁶ to 1.5 × 10⁻⁴% (m/m).     

Influences of evolved gases on the thermal decomposition of zinc carbonate hydroxide evaluated by controlled rate evolved gas analysis coupled With TG

The influences of atmospheric CO₂ and H₂O on the kinetics of the thermal decomposition of zinc carbonate hydroxide, Zn₅(CO₃)₂(OH)₆, were investigated by means of controlled rate evolved gas analysis (CREGA) coupled with TG. Although CO₂ and H₂O were evolved simultaneously in a single mass-loss step of the thermal decomposition, different effects of those evolved gases on the kinetic rate behavior were observed. No distinguished effect of atmospheric CO₂ was detected within the possible range of self-generated CO₂ concentration. On the other hand, apparent acceleration effect by the increase in the concentration of atmospheric H₂O was observed as the reduction of reaction temperature during the course of constant rate thermal decomposition. The catalytic effect was characterized by the decrease in the apparent activation energy for the established reaction with increasing the concentration of atmospheric H₂O, accompanied by the partially compensating decrease in the pre-exponential factor.     

Use of emanation thermal analysis and evolved gas analysis in thermal study of zinc(II) benzoate complex compounds

Volatile organic compounds (VOCs) are the main factors involved in pollution control and global warming in industrialized nations. Various treatment methods involving incineration, adsorption, etc., were employed to reduce VOCs concentration. Various absorbents, such as activated carbon, zeolite, silica gel or alumina, and so on were broadly used to adsorb VOCs in various industrial applications. Differential scanning calorimetry (DSC) was handled to analyze the thermal characteristics of absorbents. Typically, a scanning electron microscope (SEM) has been used to evaluate the structure variation of absorbents under high temperature situations. In view of pollution control and loss prevention, versatility and analysis of recycled adsorbents are necessary and useful for various industrial applications.     

La0.5>RE0.3Sr0.2FeO3－δ (RE = Nd、Ce、Sm)体系双稀土阴极材料的制备与电性能

采用甘氨酸-硝酸盐法(GNP)合成了La0.5RE0.3Sr0.2FeO3－δ(RE=Nd、Ce、Sm)系列复合氧化物粉体. 用X射线衍射(XRD)和TG-DSC分析了样品钙钛矿物相的形成过程, 用Archimedes排水法测量体积密度并计算烧结样品的相对密度, 用四端子技术测量电导率. 结果显示, 掺Nd的样品1200 ℃烧结2 h成为单一立方钙钛矿结构, 掺Ce样品有明显的CeO2立方相析出, 掺Sm样品主相为钙钛矿结构伴有微弱的杂峰. 1250 ℃烧结2 h的La0.5Nd0.3Sr0.2FeO3－δ在600 ℃时电导率高达100 S•cm-1以上, 明显高于La0.5Ce0.3Sr0.2FeO3－δ及La0.5Sm0.3Sr0.2FeO3－δ样品的电导率, 预示着La0.5Nd0.3Sr0.2FeO3－δ可能是一种良好的中温固体氧化物燃料电池(SOFC)阴极材料.     

Stability analysis of the neutral noble gas molecules FNgX and their anions FNgX− (Ng = He,Ar, Kr; X = O,S)

The structural stability and bonding energies of the neutral noble gas molecules FNgX and their anions FNgX^? (Ng = He, Ar, Kr; X = O, S) are discussed at the CCSD(T)/aug‐cc‐pVnZ (n = D, T) levels. Results reveal that only two neutral FKrX molecules are stable, whereas their FHeX and FArX counterparts are not. All their anions are stable and the stability mainly derives from the contribution of the extra electron, i.e., the attachment of the electron greatly enhances the orbital interactions of two bonds, F? Ng and Ng? X. Different from the anion counterparts, the electrostatic interaction energy plays a crucial role in the FKrX stability. Compared with those unstable FHeX and FArX counterparts, the enough charge distribution over each atom of FKrX ensures the effective bonding between F and Kr, and between Kr and X, consequently strengthen the stability of the neutral FKrX (X = O, S) structures. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2009     

Qualitative and quantitative investigation of chromium-polluted soils by laser-induced breakdown spectroscopy combined with neural networks analysis

Laser-induced breakdown spectroscopy (LIBS) has been applied to the analysis of three chromium-doped soils. Two chemometric techniques, principal components analysis (PCA) and neural networks analysis (NNA), were used to discriminate the soils on the basis of their LIBS spectra. An excellent rate of correct classification was achieved and a better ability of neural networks to cope with real-world, noisy spectra was demonstrated. Neural networks were then used for measuring chromium concentration in one of the soils. We performed a detailed optimization of the inputs of the network so as to improve its predictive performances and we studied the effect of the presence of matrix-specific information in the inputs examined. Finally the inputs of the network—the spectral intensities—were replaced by the line areas. This provided the best results with a prediction accuracy and precision of about 5% in the determination of chromium concentration and a significant reduction of the data, too. Awarded a poster prize on the occasion of the Euro-Mediterranean Symposium on Laser-induced Breakdown Spectroscopy (EMSLIBS 2005), Aachen, Germany, 6–9 September 2005.     

Mechanism of Insertion Reactions between Silylenoid H2SiLiF and GeH3R (R =F,OH, NH2): a Theoretical Study

Theoretical investigations on the insertion reaction mechanisms of three- membered-ring silylenoid H2 Si Li F with GeH 3R(R = F, OH, NH2) have been systematically carried out by combined density functional theory(DFT) and ab initio quantum chemical calculations. The geometries of all stationary points for these reactions were optimized using the B3 LYP method and then the QCISD method was used to calculate the single-point energies. The calculated results indicate that, there are one precursor complex(Q), one transition state(TS), and one intermediate(IM) which connect the reactants and the products along the potential energy surface. The insertion reactions of three-membered-ring silylenoid with Ge H3 R proceed in a concerted manner, forming H2RSi-Ge H3 and Li F. The calculated potential energy barriers of the three reactions are 29.17, 30.90, and 54.07 k J/mol, and the reaction energies for the three reactions are –127.05, –116.91, and –103.31 k J/mol, respectively. The insertion reactions in solvents are similar to those in vacuum. Under the same situation, the insertion reactions should occur easily in the following order: GeH 3-F GeH 3-OH GeH 3-NH2. The elucidations of the mechanism of these insertion reactions provided a new mode of silicon-germanium bond formation.     

Rapid Determination of Phenolics,Flavonoids, and Antioxidant Properties of Physalis ixocarpa Brot. ex Hornem. and Physalis angulata L. by Infrared Spectroscopy and Partial Least Squares

Physalis ixocarpa Brot. ex Hornem. and Physalis angulata L. are two edible species of the family Solanaceae, which have an important variety of antioxidant compounds present in their roots, stems, leaves, calyces, and fruits. This work reports the development of multivariate models based on the use of partial least square (PLS) analysis and Fourier transform infrared (FTIR) spectroscopy for the quantitative determination of total phenolics, total flavonoids, free radical scavenging activity, total antioxidant capacity, and reducing power in the extracts of roots, stems, and leaves of both P. ixocarpa and P. angulata. Standard chromatographic and colorimetric techniques were used to determine the quantitative actual values (references) in the extracts, which served as input data to develop the multivariate PLS models. Optimized FTIR-PLS models were realized by cross-validation procedures, obtaining the determination coefficients for prediction between 0.792 and 0.905 for P. ixocarpa, and between 0.756 and 0.893 for P. angulata. In this form, FTIR spectroscopy with multivariate analysis could represent a versatile tool to evaluate quantitatively concentrations of bioactive compounds and antioxidant properties in the extracts of both species, requiring a very short time at low cost.     

Synthesis,structure, network and thermal analysis of four 5-(pyrazinyl)tetrazolato copper(II) and cobalt(II) complexes

Three new copper complexes and one cobalt complex with 5-(pyrazinyl)tetrazolate anion, (pyztz)⁻, as chelating bidentate ligand, were obtained by the reaction of pyrazinecarbonitrile with sodium azide in the presence of copper(II) nitrate or cobalt(II)chloride. Complexes of composition [Cu(pyztz)₂(H₂O)] (1) deep blue crystals, [Cu(pyztz)₂(H₂O)₂] (2a) green crystals, [Co(pyztz)₂(H₂O)₂] (2b) orange crystals, [Cu(pyztz)₂(H₂O)₂] · (H₂O) (3) blue crystals were obtained. The single crystal X-ray diffraction revealed that complex 1 has square pyramidal structure with one water molecule at apical and two pyrazine-tetrazolato ligands at basal sites, while structures of 2a, 2b and 3 consist of octahedrally coordinated metal ions, where two pyztz anions act as bidentate ligands via one of the pyrazine-N atoms and one of the tetrazole-N atoms in trans-positions and two trans water molecules. Complex 3 contains one extra lattice water molecule. Hydrogen bonds of the types O–H?O and O–H?N connect the mononuclear units to a three-dimensional network structure in 2 (a and b are isostructural) and 3. Although the H-bond patterns look complex it is shown that they can be related to the well-known three- and six-connected rutile net (rtl) in 2 and the four- and six-connected fsh-net in 3.     

Phase Behaviour of Poly(styrene-co-methacrylic acid)/ Poly(styrene-co-N,N-dimethylacrylamide)/Poly(styrene-co-4-vinylpyridine) Ternary Blends by DSC and FTIR

Summary: we have investigated by DSC and FTIR the miscibility and phase behaviour of binary and ternary blends of different ratios of poly(styrene-co-methacrylic acid) containing 15 mol% of methacrylic acid (SMA15) with poly(styrene-co-N,N-dimethylacrylamide) containing 17 mol% of N,N,-dimethylacrylamide (SAD-17) and poly(styrene- co-4-vinylpyridine) containing 15 mol% of 4-vinylpyridine. SMA15 is miscible with both SAD17 and S4VP15 and interacts more strongly with S4VP15 than with SAD17 as evidenced by the positive deviations from linear average line observed with these blends and the appearance of new bands in the 1800–1550 cm⁻¹ region. This behaviour is known as ΔK effect. The FTIR study confirms that though the specific intermolecular interactions that occurred with each pair of the SMA15/S4VP15 and SMA15/SAD17 binary components are of different strength, they still exist in the ternary blend. Even though the three binary polymer pairs are individually miscible, the ternary system of SMA15/S4VP15/SAD17 exhibits only partial miscibility with small loop of immiscibility due to a significant ΔK effect. These results obtained by DSC and FTIR are in a fair agreement with theoretical prediction applying the Painter-Coleman association model.     

Temperature dependence of molecular conformation in uniaxially deformed isotactic polypropylene investigated by combination of polarized FTIR spectroscopy and 2D correlation analysis

Evolution of molecular conformation in uniaxially deformed isotactic polypropylene (iPP) as a function of temperature is investigated by time‐resolved polarized Fourier‐transform infrared spectroscopy. It is observed that oriented crystals (microfibrils) induced by deformation possess better thermal stability compared with isotropic spherulites. 2D correlation analysis reveals that the relaxation process of ordered helices in deformed iPP could be divided into two regions referring to the melting of different crystalline structures. No obvious sequential change of ordering conformations observed in low temperature region is attributed to melting of defective or destructed crystals. However, notable sequential changes of helices occur in the high temperature region; interestingly, long helices are more thermally stable than short helices. The central region of microfibrils is suggested to consist of a large amount of long helical bundles, and the short ordering segments are primarily located in the outer lateral surfaces. A physical picture of the conformational distribution in deformation‐induced microfibrils is thus gained. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 673–684     

A series of 1-D zinc(II) coordination polymers with 3-D supramolecular networks: synthesis,structural investigation,and NBO analysis

Abstract

N,N′-Bis(pyridin-4-ylmethylene)naphthalene-1,5-diamine (L) acts as a bipyridine analogue linker ligand towards {Zn₇(μ₄-O)₂(OAc)₁₀}, {Zn₂(NCS)₂(OAc)₂}, and {Zn(N₃)₂} nodes and allows construction of three new 1-D coordination polymers, the linear chain [Zn₇(μ₄-O)₂(OAc)₁₀(L)]_n (1), [Zn(NCS)(OAc)(L)]_n (2) in ladder-type geometry and the zigzag chain [Zn(N₃)₂(L)]_n (3). Structural characterization reveals that in 1 acetate anionic ligands connect seven Zn(II) ions through the bridging coordination modes μ₃-η¹,η² and μ₂-η¹,η¹. The resulting heptanuclear node is located on an inversion center and therefore consists of four crystallographically distinct cations; their coordination spheres correspond to distorted octahedra or tetrahedra. The Zn(II) ions in polymer 2 exhibit distorted trigonal bipyramidal {ZnN₃O₂} coordination; μ₂-η¹,η¹ coordinated acetate and terminal thiocyanate ligands lead to inversion-symmetric [Zn₂(NCS)₂(OAc)₂] secondary building units (SBU), which are further linked by the N,N′-bipyridine analogue L. Terminal coordination of two anionic azide ligands and the bridging bipyridine L result in coordination polymer 3, in which the cations adopt distorted tetrahedral {ZnN₄} coordination. In all crystalline solids 1–3, adjacent 1-D chains interact through π–π stacking and non-classical (C???H···O, C???H···π) hydrogen bonds, leading to 3-D supramolecular architectures. Differences in their 3-D arrangement are due to variations in the anionic co-ligands, subtle conformational differences in the semi-rigid linker and the variable coordination sphere about the zinc cations. Thermogravimetric investigations indicate differences in both thermal stability and decomposition mode. Natural bond orbital (NBO) analysis provides a convenient basis for investigating the intramolecular bonding interactions and delocalization effects in these molecular systems. Finally, solids 1–3 exhibit intense luminescence at room temperature.     

Loss of polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans and coplanar polychlorinated biphenyls during nitrogen gas blowdown process for ultra-trace analysis

This study examined standard solutions to assess the influence of the gas flow rate and organic solvent type on losses caused by gas blowdown of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/DFs) and coplanar polychlorinated biphenyls (Co-PCBs). Results obtained here will contribute to maintaining analytical method performance and system quality for PCDD/DFs and Co-PCBs analyses. An organic solvent (with 0.5 ml each of acetone, dichloromethane, n-hexane, and toluene), PCDD/DFs or Co-PCBs, and their ¹³C₁₂-labeled compounds were put separately into 10 ml pear-shaped flasks. The samples were blown to dryness at room temperature until the last trace of solvent disappeared. They were subsequently reconstituted in those flasks. Analyte recoveries were calculated by comparing blown samples to those that had not been blown. Recoveries of Co-PCBs were more affected than those of PCDD/DFs when the gas flow rates were set at 203, 261, 332, and 456 ml/min. Losses of Co-PCBs were least at 203-332 ml/min. Regarding losses of PCDD/DFs and Co-PCBs, the toluene solution showed the least variation in recovery. An actual soil sample extract was also examined using optimized conditions for the gas flow rate and solvent types obtained by experiments in standard solutions. Thereby, the blowdown conditions gave quantitative recoveries of ¹³C₁₂-labeled compounds in the sample extract.     

Mono and binuclear Ag(I), Cu(II), Zn(II) and Hg(II) complexes of a new azo-azomethine as ligand: synthesis, potentiometric, spectral and thermal studies

New azo-azomethine dyes were prepared by reaction of p-aminobenzoic acid, o-anisidine, o-nitroaniline, and p-bromoaniline with salicylaldehyde respectively to form azo compounds and then condensation by urea to form 4-(R-arylazo 2-salicylaldene)-urea azo-azomethine derivatives (I(a-d)). The complexes of these ligands with Ag(I), Cu(II), Zn(II) and Hg(II) metal ions were prepared. The structure of the free ligands and their complexes were characterized by using elemental analysis (C, H, N), (1)H NMR, IR and UV-Vis-spectra. The proton dissociation constants of the ligands and the stability constant of their complexes have been determined potentiometrically in 40% (v/v) alcohol-water medium as well as the stoichiometry of complexes were determined conductometrically. The data reveal that the stoichiometries for all complexes were prepared in molar ratios (1:1) and (1:2) (M:L). The electrolytic and nonelectrolytic natures of the complexes were assigned based on molar conductance measurements. The thermogravimetric (TG), and differential thermal analyses (DTA) were studied in nitrogen atmosphere with heating rate 10°C/min. The kinetic and thermodynamic parameters for thermal decomposition of complexes have been calculated by graphical method using Coats-Redfern (CR) method.     

Mechanistic investigation, kinetic modeling and analysis parameters of poly(3-hexylthiophene) degradation to fullerenes

Thermal degradation of Poly (3-hexylthiopene) (P3HT) was studied under nitrogen environment. Kinetic parameters of thermal degradation were determined using Vyazovkin model free method and model fitting method. Vyazovkin model free kinetic analysis is carried out to understand the variation of activation energy (E_α) required for degradation of polymer with conversion (α). Various reaction models have been tested for probable reaction mechanism using hybrid genetic algorithm (HGA). Diffusion model and nucleation & growth with n = 2/3 has prominent role in thermal decomposition of P3HT. A plausible degradation route is proposed based on the experimental details acquired from gas chromatography (GC), Raman spectroscopy, FTIR spectroscopy, powder X-ray diffractometry (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Degradation of P3HT starts at around 195 °C with release of lighter units like CS. Further increase in the temperature results in detachment of the hexyl chain from P3HT and the residue obtained at 1050 °C contains fullerenes mixed with amorphous carbon.     

Thiocyanation, Halogenation, Dehalogenation, Transhalogenation, and Nitration of 2-Substituted 4-(2-Furyl)thiazoles

Bromination and thiocyanation of 2-amino- and 2-acetylamino-4-(2-furyl)thiazoles when 1 mol of reagent is used at 10°C are directed to the 5 position. Formation of 5'-bromo-substituted derivatives when the reaction temperature is raised is the result of a secondary, thermodynamically controlled process. Monohalogenation and mononitration of 4-(2-furyl)-2-methylthiazole are directed to the 5' position. Nitration of 2-acetylamino-4-(5-nitro-2-furyl)thiazole by a nitrating mixture is accompanied by oxidative cleavage of the 5-nitrofuran moiety and leads to formation of 5,5'- and 3',5'-dinitro derivatives.     

Synthesis,characterization, and investigation of structure‐thermal cycloimidization relationship of novel poly(amide amic acid)s to poly(amide imide)s by thermogravimetric analysis

Novel diamic acids (DAAs) and poly(amide amic acid)s (PAAs) were prepared and their thermal cycloimidization to the corresponding imide form was investigated by thermogravimetric analysis under isothermal conditions at four different temperatures, that is, at 175, 200, 225, and 260 °C for 75 min. A general equation, 18NW/R_MW, where, the numerical 18 corresponds to the molecular weight of water, N is the number of water molecules, which would be eliminated per repeat unit of the PAA upon cycloimidization, W is the weight of PAA taken for TGA, and R is the molecular weight of the repeat unit of PAA, has been derived for the calculation of theoretical amount of weight loss of PAA upon complete cycloimidization. The degree of cycloimidization (DCI%) of PAAs to poly(amide imide)s (PAI) has been calculated from their isothermal TGA curves. The variation in DCI on temperature, time, and the structures of diamine and acid chloride, especially, with respect to meta‐ and para‐linkages and the presence of electron withdrawing groups has been discussed. Cycloimidization occurs at faster rate in the initial stages of about 20 min, curing and then proceeds in a gradual manner and reaches almost a plateau within an hour. The DCI was more at higher temperatures, and the final values were 22?60% at 175 °C, 34?78% at 200 °C, 50?96% at 225 °C, and 85?99% at 260 °C after 75 min of heating, depending on the nature of diamine and acid chloride in the PAA. The DCI of PAAs with meta‐linkages in either of diamine or diacid chloride was somewhat lower than those having para‐linkages. The DCI of PAAs containing electron withdrawing group like sulfone in the diamine is somewhat higher compared with those of others. The final DCI (%) values obtained from FT‐IR spectra and isothermal TGA curves were very close to each other. Further, the thermal and thermooxidative stabilities of the PAIs were discussed. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2937–2947, 2007     

Infrared study of νOD modes in isotopically dilute (HDO) isostructural compounds M(HCOO)2·2H2O (M=Mn,Fe,Co,Ni,Cu,Zn) with matrix-isolated guest ions (Cu in M(HCOO)2·2H2O and M in Cu(HCOO)2·2H2O)

The infrared spectra of isotopically dilute (matrix-isolated HDO molecules) isostructural compounds M(HCOO)₂·2H₂O (M=Mn,Fe,Co,Ni,Zn,Cu) are presented and discussed in the region of the OD stretching modes. According to the structural data the compounds under study are divided into two groups: in M(HCOO)₂·2H₂O (M=Mn,Ni,Zn) the H₂O(1) molecules form stronger hydrogen bonds as compared to H₂O(2); in M(HCOO)₂·2H₂O (M=Fe,Co,Cu) the H₂O(2) molecules form stronger hydrogen bonds as compared to the H₂O(1) molecules. The influence of the metal–water interactions (synergetic effect) and the unit-cell volumes (repulsion potential of the lattice) on the hydrogen bond strength within the isostructural series is discussed. The wavenumbers of the uncoupled OD stretching modes of the HDO molecules influenced by guest ions (Cu²⁺ ions matrix-isolated in M(HCOO)₂·2H₂O and M²⁺ ions matrix-isolated in Cu(HCOO)₂·2H₂O) are presented and commented. For example, the analysis of the spectra reveals that when Cu²⁺ ions are included in the structure of M(HCOO)₂·2H₂O the hydrogen bonds of the type M–OH₂OCHO–Cu are considerably weaker as compared to those of the same type formed when M²⁺ ions are included in the structure of Cu(HCOO)₂·2H₂O if the cations remain unchanged.     

Preparation and performance analysis of PE-supported P(AN-co-MMA) gel polymer electrolyte for lithium ion battery application

Copolymer, poly(acrylonitrile-co-methyl methacrylate) (P(AN-co-MMA)), was synthesized by solution polymerization with different mole ratios of monomers, acrylonitrile (AN) and methyl methacrylate (MMA). Polyethylene (PE) supported copolymer and gel polymer electrolyte (GPE) were prepared with this copolymer and their performances were characterized with FTIR, TGA, SEM, and electrochemical methods. It is found that the GPE using the PE-supported copolymer with AN to MMA = 4:1 (mole) exhibits an ionic conductivity of 2.06 × 10⁻³ S cm⁻¹ at room temperature. The copolymer is stable up to 270 °C. The PE-supported copolymer shows a cross-linked porous structure and has 150 wt% of electrolyte uptake. The GPE is compatible with anode and cathode of lithium ion battery at high voltage and its electrochemical window is 5.5 V (vs. Li/Li⁺). With the application of the PE-supported GPE in lithium ion battery, the battery shows its good rate and initial discharge capacity and cyclic stability.