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1.
Theoretical K-shell photoionization and K X-ray fluorescence (K XRF) cross sections have been fitted empirically in polynomials of photon energy E and atomic number Z. This has been used to develop a computer code KCSPIF to generate K-shell photo-ionization and K XRF cross-sections for any element in the range 5≤Z≤95 and for photon energies, above K-edge–1500 keV, when only the atomic number and photon energy are supplied as the input. 相似文献
2.
Sthanumoorthy Regupathy Madhavan Sivasankaran Nair 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2010,75(2):656-663
Equilibrium studies on the ternary complex systems involving ampicillin (amp) as ligand (A) and imidazole containing ligands viz., imidazole (Him), benzimidazole (Hbim), histamine (Hist) and histidine (His) as ligands (B) at 37 °C and I = 0.15 mol dm?3 (NaClO4) show the presence of CuABH, CuAB and CuAB2. The proton in the CuABH species is attached to ligand A. In the ternary complexes the ligand, amp(A) binds the metal ion via amino nitrogen and carbonyl oxygen atom. The CuAB (B = Hist/His)/CuAB2 (B = Him/Hbim) species have also been isolated and the analytical data confirmed its formation. Non-electrolytic behavior and monomeric type of chelates have been assessed from their low conductance and magnetic susceptibility values. The electronic and vibrational spectral results were interpreted to find the mode of binding of ligands to metal and geometry of the complexes. This is also supported by the g tensor values calculated from ESR spectra. The thermal behaviour of complexes were studied by TGA/DTA. The redox behavior of the complexes has been studied by cyclic voltammetry. The antimicrobial activity and CT DNA cleavage study of the complexes show higher activity for ternary complexes. 相似文献
3.
《The Journal of chemical thermodynamics》2004,36(1):7-16
The apparent molar volumes Vφ of glycine, alanine, valine, leucine, and lysine have been determined in aqueous solutions of 0.05, 0.5, 1.0 mol · kg−1 sodium dodecyl sulfate (SDS) and 1.0 mol · kg−1 cetyltrimethylammonium bromide (CTAB) by density measurements at T=298.15 K. The apparent molar volumes have also been determined for diglycine and triglycine in 1 mol · kg−1 SDS and CTAB solutions. These data have been used to calculate the infinite dilution apparent molar volumes V20 for the amino acids and peptides in aqueous SDS and CTAB and the standard partial molar volumes of transfer (ΔtrV2,m0) of the amino acids and peptides to these aqueous surfactant solutions. The linear correlation of V20 for a homologous series of amino acids has been utilized to calculate the contribution of the charged end groups (NH3+, COO−), CH2 group and other alkyl chains of the amino acids to V20. The results on the partial molar volumes of transfer from water to aqueous SDS and CTAB have been interpreted in terms of ion–ion, ion–polar and hydrophobic–hydrophobic group interactions. The volume of transfer data suggests that ion–ion or ion–hydrophilic group interactions of the amino acids and peptides are stronger with SDS compared to those with CTAB. Comparison of the hydration numbers of amino acids calculated in the present studies with those in other solvents from literature shows that these numbers are almost the same at 1 mol · kg−1 level of the cosolvent/cosolute. Increasing molality of the cosolvent/cosolute beyond 1 mol · kg−1 lowers the hydration number of the amino acids due to increased interactions with the solvent and reduced electrostriction. 相似文献
4.
Jian-ying Wang Xiang-jing Zhang Yong-qi Hu Guo-di Qi Li-ya Liang 《The Journal of chemical thermodynamics》2012,45(1):43-47
The density and surface tension of the pure ionic liquid n-butylpyridinium nitrate ([BuPy]NO3) were determined at temperature range from T = (293.15 to 338.15) K. The coefficient of thermal expansion, molecular volume and lattice energy of [BuPy]NO3 were calculated from the experimental values of density. The surface entropy and enthalpy of [BuPy]NO3 were investigated. The IL studied show much lower surface enthalpy and lattice energy in comparison with fused salts. The densities and surface tensions of binary mixtures of [BuPy]NO3 with water have been measured within the whole composition range at T = 298.15 K and atmospheric pressure. Excess molar volumes VE and surface tension deviations δγ were then deduced from the experimental results as well as partial molar volumes and excess partial molar volumes. Excess molar volumes have a negative deviation from ideal behavior and the surface tension deviations are negative over the whole compositions range. VE and δγ were correlated with suitable equation respectively. 相似文献
5.
The heat capacity of Ir(C5H7O2)3 has been measured by the adiabatic method within the temperature range (5 to 305) K. The thermodynamic functions (entropy, enthalpy, and reduced Gibbs free energy) at 298.15 K have been calculated using the obtained experimental heat capacity data. A connection has been found between the entropy and the volume of the elementary crystalline cell for β-acetylacetonates of some metals. The reasons for this interdependence are discussed. The values of entropies at T = 298.15 K have been calculated for all the metal acetylacetonates on which there are structural data. 相似文献
6.
《Solid State Sciences》2007,9(9):817-823
Double layered La2−2xCa1+2xMn2O7 manganite has been synthesized using solid state reaction method for different dopant concentration x = 0.0–0.5. Their temperature dependence of resistivity (ρ − T) has been studied in the semiconducting region. The experimental observations were compared with the theoretically simulated temperature dependence of resistivity curves based on nearest neighbour hopping, Efros–Shklovskii variable range hopping, and Mott's 2D and 3D variable range hopping models. From the analysis of these results, Mott's 3D variable range hopping mechanism seemed to be most suitable mechanism describing the semiconducting behaviour of these double layered manganites. Temperature dependent activation energy also supported the Mott's 3D variable range hopping model. The Mott's activation energy was found to vary with the dopant concentration x and it showed a minimum value for x = 0.3. 相似文献
7.
《Fluid Phase Equilibria》2005,233(1):34-46
A series of bicanonical ensemble Monte Carlo (BC MC) simulations has been performed to calculate Na+ hydration Gibbs energy in aqueous solution. The hydration Gibbs energy of Na+ ion in aqueous solution is the difference between formation free energies of Na+ (H2O)n and (H2O)n clusters at n → α. The convergence of the hydration free energy to bulk water value is fast, and the results at n = 60 turned out to be in good agreement with experimental ones and those calculated using free energy perturbation method [1]. The ion–water interaction has been described by Aqvist's pair potential [1] and SPC model [2] has been used for water–water interactions. The behaviour of the absolute Gibbs energy, the entropy, the internal energy of the clusters and the development of hydration shells’ structure with the increase of the number of water molecules are discussed. 相似文献
8.
《Polyhedron》2007,26(9-11):1811-1819
Seven kinds of polynuclear complexes of [Cu(hfac)2] (Hhfac = 1,1,1,5,5,5-hexafluoropentane-2,4-dione) with diazaaromatic rings have been prepared. The crystal structures of [{Cu(hfac)2(μ-L)}n] (L = 2,5- and 2,6-dimethylpyrazines, propylpyrazine (prpyz), quinoxaline, phenazine, 4,6-dimethylpyrimidine, and 1,6-naphthyridine) have been determined. These complexes consist of a one-dimensional chain structure, and the geometry around the copper ion is approximately an octahedral structure. The relations between the magnetic properties and coordination structure were discussed from the magnetic measurements. In the μ-prpyz complex, one nitrogen atom is coordinated to a copper ion at an axial position, and at the same time the other coordinated at an equatorial site of a neighboring copper ion. This complex showed antiferromagnetic interaction with J/kB = −0.086(3) K estimated from the Bonner–Fisher model. Weak magnetic interaction is caused by the somewhat long Cu–N distances due to the steric effect from the bridging ligands. 相似文献
9.
C.K. Modi D.H. Jani H.S. Patel H.M. Pandya 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2010,75(4):1321-1328
Fluorescence properties of five 4-acyl pyrazolone based hydrazides (H2SBn) and their Fe (III) heterochelates of the type [Fe(SBn)(L)(H2O)]·mH2O [H2SBn = nicotinic acid [1-(3-methyl-5-oxo-1-phenyl-4,5-di hydro-1H-pyrazol-4yl)-acylidene]-hydrazide; where acyl = –CH3, m = 4 (H2SB1); –C6H5, m = 2 (H2SB2); –CH2–CH3, m = 3 (H2SB3); –CH2–CH2–CH3, m = 1.5 (H2SB4); –CH2–C6H5, m = 1.5 (H2SB5) and HL = 1-cyclopropyl-6-fluoro-4-oxo-7-(piperazin-1-yl)-1,4-dihydroquinoline-3-carboxylic acid] were studied at room temperature. The fluorescence spectra of heterochelates show red shift, which may be due to the chelation by the ligands to the metal ion. It enhances ligand ability to accept electrons and decreases the electron transition energy. The kinetic parameters such as order of reaction (n), energy of activation (Ea), entropy (S*), pre-exponential factor (A), enthalpy (H*) and Gibbs free energy (G*) have been reported. 相似文献
10.
A new apparatus for the determination of VLE has been constructed which works for absolute pressure measurements as well as for measuring differential pressures. The first results obtained are (vapor + liquid) equilibria (VLE) of binary mixtures containing acetonitrile or tetrahydrofuran and the ionic liquid (IL) 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [EMIm][NTf2] by using the absolute pressures method. VLE measurements were carried out over the whole concentration range at four different temperatures between 293.15 K and 313.15 K. Activity coefficients (γ1) of the solvents in [EMIm][NTf2] and their osmotic coefficients (ϕ1) have been determined from the VLE data. 相似文献
11.
《The Journal of chemical thermodynamics》2003,35(4):677-687
Partition coefficients Kc of phenol between an aqueous solution containing different salts and a compressed CO2 phase have been determined at T=313 K. For NaCl and (CH3)4NBr a pressure range from 8 MPa to around 30 MPa was investigated, for KCl and NaBr measurements were performed at a pressure of 22 MPa. The salt concentration has been varied between (0.25 and 3.0) mol·dm−3. With increasing pressure a rise in Kc is observed which typically is also found in systems free of salt. Salting-out was observed for the alkali salts, salting-in has been found for the ammonium salt, both effects increased with increasing salt concentration. From the concentration dependence of the Kc values Setschenow coefficients kS have been derived. At p>10 MPa values are obtained as found in two phase mixtures of water with other organic solvents at ambient pressure. This conclusion was confirmed with both literature and own experimental data in the case of salting-out by NaCl as well as for the salting-in by (CH3)4NBr from measurements with phenol in (water + cyclohexane) at T=313 K. 相似文献
12.
《Fluid Phase Equilibria》2005,227(2):197-213
CO2 solubility was measured in a wetted-wall column in 0.6–3.6 molal (m) piperazine (PZ) and 2.5–6.2 m potassium ion (K+) at 40–110 °C. Piperazine speciation was determined using 1H NMR for 0.6–3.6 m piperazine (PZ) and 3.6–6.2 m potassium ion (K+) at 25–70 °C. The capacity of CO2 in solution increases as total solute concentration increases and compares favorably with estimates for 7 m (30 wt.%) monoethanolamine (MEA). The presence of potassium in solution increases the concentration of CO32−/HCO3− in solution, buffering the solution. The buffer reduces protonation of the free amine, but increases the amount of carbamate species. These competing effects yield a maximum fraction of reactive species at a potassium to piperazine ratio of 2:1.A rigorous thermodynamic model was developed, based on the electrolyte nonrandom two-liquid (ENRTL) theory, to describe the equilibrium behavior of the solvent. Modeling work established that the carbamate stability of piperazine and piperazine carbamate resembles primary amines and gives approximately equal values for the heats of reaction, ΔHrxn (18.3 and 16.5 kJ/mol). The pKa of piperazine carbamate is twice that of piperazine, but the ΔHrxn values are equivalent (∼−45 kJ/mol). Overall, the heat of CO2 absorption is lowered by the formation of significant quantities of HCO3− in the mixed solvent and strongly depends on the relative concentrations of K+ and PZ, ranging from −40 to −75 kJ/mol. 相似文献
13.
Han SY Guo QH Xu MM Yuan YX Shen LM Yao JL Liu W Gu RA 《Journal of colloid and interface science》2012,370(1):51-57
Novel lanthanum borate (LaBO3) hollow nanospheres of size 34 ± 2 nm have been reported for the first time by soft-template self-assembly process. Poly(styrene-b-acrylic acid-b-ethylene oxide) (PS-PAA-PEO) micelle with core–shell–corona architecture serves as an efficient soft template for fabrication of LaBO3 hollow particles using sodium borohydride (NaBH4) and LaCl3?7H2O as the precursors. In this template, the PS block (core) acts as a template of the void space of hollow particle, the anionic PAA block (shell) serves as reaction field for metal ion interactions, and the PEO block (corona) stabilizes the polymer/lanthana composite particles. The PS-PAA-PEO micelles and the resulting LaBO3 hollow nanospheres were thoroughly characterized by dynamic light scattering (DLS), transmission electron microscope (TEM), X-ray diffraction, magic angle spinning-nuclear magnetic resonance (11B MAS NMR), energy dispersive X-ray analysis, thermal analyses, Fourier transform infra red spectroscopy, and nitrogen adsorption/desorption analyses. The nitrogen adsorption/desorption analyses and TEM observation of the hollow particles confirmed the presence of disordered mesopores in the LaBO3 shell domain. The solid state 11B MAS NMR spectra of LaBO3 hollow nanospheres revealed that the shell part contains both trigonal and tetrahedral boron species. The LaBO3 hollow particles were applied to anode materials in lithium-ion rechargeable batteries (LIBs). The hollow particles exhibited high coulombic efficiency and charge–discharge cycling capacities of up to 100 cycles in the LIBs. 相似文献
14.
Optical transmittance in the range from 200 nm to 1100 nm is measured for fresh and γ-irradiated thermally evaporated chalcogenide films of GeSe3, Sb2Se3, ZnSe, (GeSe3)80(Sb2Se3)20 and (GeSe3)70(Sb2Se3)10(ZnSe)20. The effect of ZnSe incorporation with both GeSe3, Sb2Se3 results in amorphous γ-radiation sensitive (GeSe3)70(Sb2Se3)10(ZnSe)20 composition as obtained from the estimated optical parameters. Optical energy gap, Eg, for (GeSe3)70(Sb2Se3)10(ZnSe)20 film shows a noticeable decrease from 1.81 eV at 0 kGy to 1.52 eV at 690 kGy and conversely the corresponding band tail width, Ee, increases from 0.123 eV at 0 kGy to 0.138 eV at 690 kGy. By contrast, the estimated values of Eg and Ee for (GeSe3)80(Sb2Se3)20 compositions, show no change with different γ-irradiation doses in the same range. The obtained results could be explained in terms of the band edge shift into the energy gap due to either the formation of localized states at the edges or weakening in the composition cohesive energy as reformation of new weaker bonds appear. 相似文献
15.
Ce(H2O)(PO4)3/2(H3O)1/2(H2O)1/2, a second entry in the structural chemistry of cerium(IV) phosphates
《Solid State Sciences》2007,9(8):672-677
A cerium(IV) phosphate has been prepared using precipitation methods and its structure has been solved by single crystal X-ray diffraction (R1 = 0.0292 for 3092 reflections with I>2σ(I) and wR2 = 0.0540). Ce(H2O)(PO4)3/2(H3O)1/2(H2O)1/2 crystallises in the monoclinic space group C2/c (a = 15.7058(17) Å, b = 9.6261(9) Å, c = 10.1632(4) Å, ß = 121.623(7)°, and V = 1308.4 (2) Å3). Its structure is based on a negatively charged 3D framework, made of cerium atoms connected by PO4 tetrahedra. There are two types of PO4 units; one shares only corners with the cerium coordination polyhedra while the other one shares edges and corners. This structure also includes hydronium cations, to balance the framework charge, and water molecules. One special feature of this 3D framework is the formation of interconnected tunnels which extend along the c axis and contain the hydronium cations and the water molecules. This open framework and the presence of cationic species in the tunnels are in perfect agreement with the previously reported ion exchange properties. 相似文献
16.
M.-M. Bagheri-Mohagheghi N. Shahtahmasebi M.R. Alinejad A. Youssefi M. Shokooh-Saremi 《Solid State Sciences》2009,11(1):233-239
In this paper, we report structural, electrical, optical, and especially thermoelectrical characterization of iron (Fe) doped tin oxide films, which have been deposited by spray pyrolysis technique. The doping level has changed from 0 to 10 wt% in solution ([Fe]/[Sn] = 0–40 at% in solution). The thermoelectric response versus temperature difference has exhibited a nonlinear behavior, and the Seebeck coefficient has been calculated from its slope in temperature range of 300–500 K. The Hall effect and thermoelectric measurements have shown p-type conductivity in SnO2:Fe films with [Fe]/[Sn] ≥ 7.8 at%. In doping levels lower than 7.8 at%, SnO2:Fe films have been n-type with a negative thermoelectric coefficient. The Seebeck coefficient for SnO2:Fe films with 7.8 at% doping level has been obtained to be as high as +1850 μV/K. The analysis of as-deposited samples with thicknesses ~350 nm by X-ray diffraction (XRD) and scanning electron microscopy (SEM) has shown polycrystalline structure with clear characteristic peak of SnO2 cassiterite phase in all films. The optical transparency (T%) of SnO2:Fe films in visible spectra decreases from 90% to 75% and electrical resistivity (ρ) increases from 1.2 × 10?2 to 3 × 103 Ω cm for Fe-doping in the range 0–40 at%. 相似文献
17.
Radhey M. Naik Basant Kumar Abhas Asthana 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2010,75(3):1152-1158
A kinetic spectrophotometric method for the determination of thiocyanate, based on its inhibitory effect on silver(I) catalyzed substitution of cyanide ion, by phenylhydrazine in hexacyanoferrate(II) is described. Thiocyanate ions form strong complexes with silver(I) catalyst which is used as the basis for its determination at trace level. The progress of reaction was monitored, spectrophotometrically, at 488 nm (λmax of [Fe(CN)5PhNHNH2]3?, complex) under the optimum reaction conditions at: 2.5 × 10?3 M [Fe(CN)6]4?, 1.0 × 10?3 M [PhNHNH2], 8.0 × 10?7 M [Ag+], pH 2.8 ± 0.02, ionic strength (μ) 0.02 M (KNO3) and temperature 30 ± 0.1 °C. A linear relationship obtained between absorbance (measured at 488 nm at different times) and inhibitor concentration, under specified conditions, has been used for the determination of [thiocyanate] in the range of 0.8–8.0 × 10?8 M with a detection limit of 2 × 10?9 M. The standard deviation and percentage error have been calculated and reported with each datum. A most plausible mechanistic scheme has been proposed for the reaction. The values of equilibrium constants for complex formation between catalyst–inhibitor (KCI), catalyst–substrate (Ks) and Michaelis–Menten constant (Km) have been computed from the kinetic data. The influence of possible interference by major cations and anions on the determination of thiocyanate and their limits has been investigated. 相似文献
18.
《The Journal of chemical thermodynamics》2003,35(3):475-492
Low-temperature calorimetric measurements have been performed on DyBr3(s) in the temperature range (5.5 to 420 K ) and on DyI3(s) from T=4 K to T=420 K. The data reveal enhanced heat capacities below T=10 K, consisting of a magnetic and an electronic contribution. From the experimental data on DyBr3(s) a C0p,m (298.15 K) of (102.2±0.2) J·K−1·mol−1 and a value for {S0m (298.15 K) − S0m (5.5 K)} of (205.5±0.5) J·K−1·mol−1, have been obtained. For DyI3(s), {S0m (298.15 K) − S0m (4 K)} and C0p,m (298.15 K) have been determined as (226.9±0.5) J·K−1·mol−1 and (103.4±0.2) J·K−1·mol−1, respectively. The values for {S0m (5.5 K) − S0m (0)} for DyBr3(s) and {S0m (4 K) − S0m (0)} for DyI3(s) have been calculated, giving S0m (298.15 K)=(212.3±0.9) J·K−1·mol−1 in case of DyBr3(s) and S0m (298.15 K) =(233.1±0.7) J·K−1·mol−1 for DyI3(s). The high-temperature enthalpy increment has been measured for DyBr3(s) in the temperature range (525 to 799 K) and for DyI3(s) in the temperature range (525 to 627 K). From the results obtained and enthalpies of formation from the literature, thermodynamic functions for DyBr3(s) and DyI3(s) have been calculated from T→0 to their melting temperatures at 1151.0 K and 1251.5 K, respectively. 相似文献
19.
A. Agarwal A. Sheoran S. Sanghi V. Bhatnagar S.K. Gupta M. Arora 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2010,75(3):964-969
Glasses with compositions xNb2O5·(30 ? x)M2O·69B2O3 (where M = Li, Na, K; x = 0, 4, 8 mol%) doped with 1 mol% V2O5 have been prepared using normal melt quench technique. The IR transmission spectra of the glasses have been studied over the range 400–4000 cm?1. The changes caused by the addition of Nb2O5 on the structure of these glasses have been reported. The electron paramagnetic resonance spectra of VO2+ ions in these glasses have been recorded in X-band (9.14 GHz) at room temperature (300 K). The spin Hamiltonian parameters, dipolar hyperfine coupling parameter and Fermi contact interaction parameter have been calculated. It is observed that the resultant resonance spectra contain hyperfine structures (hfs) due to V4+ ions which exist as VO2+ ions in octahedral coordination with a tetragonal compression in the present glasses. The tetragonality of V4+O6 complex decreases with increasing concentration of Nb2O5. The 3dxy orbit contracts with increase in Nb2O5:M2O ratio. Values of the theoretical optical basicity, Λth, have also been reported. 相似文献
20.
The apparent molar volumes and isentropic compressibility of glycine, l-alanine and l-serine in water and in aqueous solutions of (0.500 and 1.00) mol · kg?1 di-ammonium hydrogen citrate {(NH4)2HCit} and those of (NH4)2HCit in water have been obtained over the (288.15 to 313.15) K temperature range at 5 K intervals at atmospheric pressure from measurements of density and ultrasonic velocity. The apparent molar volume and isentropic compressibility values at infinite dilution of the investigated amino acids have been obtained and their variations with temperature and their transfer properties from water to aqueous solutions of (NH4)2HCit have also been obtained. The results have been interpreted in terms of the hydration of the amino acids. In the second part of this work, water activity measurements by the isopiestic method have been carried out on the aqueous solutions of {glycine + (NH4)2HCit}, {alanine + (NH4)2HCit}, and {serine + (NH4)2HCit} at T = 298.15 K at atmospheric pressure. From these measurements, values of vapour pressure, osmotic coefficient, activity coefficient and Gibbs free energy were obtained. The effect of the type of amino acids on the (vapour + liquid) equilibrium of the systems investigated has been studied. The experimental water activities have been correlated successfully with the segment-based local composition Wilson model. Furthermore, the thermodynamic behaviour of the ternary solutions investigated has been studied by using the semi-ideal hydration model and the linear concentration relations have been tested by comparing with the isopiestic measurements for the studied systems at T = 298.15 K. 相似文献