Sonoluminescence of aqueous solutions of lanthanide salts

The influence of salts (TbCl₃, Tb(NO₃)₃, PrCl₃, EuCl₃, CeCl₃, and DyCl₃) on the spectrum and intensity of multi-bubble sonoluminescence (SL) of water was observed at a frequency of 20 kHz. Luminescence bands of the lanthanide ions were detected in the SL spectra of concentrated solutions of the Ce^III, Tb^III, and Dy^III chlorides (0.1—1 mol L^–1). No luminescence was observed for solutions of the other salts, and the shape of the spectra is due to the absorption of the water SL by the lanthanide ions. Possible mechanisms of the appearance of SL of lanthanides were considered. The first mechanism is the excitation of the lanthanide aqua ions in the solution bulk due to the absorption of the short-wave portion of glow of the excited water molecules and OH radicals emitted from the cavitation gas-vapor bubbles. The second mechanism involves the transfer of the lanthanide ions to the gas phase from the liquid layer adjacent to the cavitation bubble and their excitation in the bubble volume upon collisions with other hot or electron-excited particles.     

Sonoluminescence of aqueous solutions of sulfuric acid and sulfur dioxide

Sonoluminescence (SL) of aqueous solutions of sulfuric acid and sulfur dioxide enhances with an increase in their concentration and reaches a maximum at 16 and 0.05 mol L^–1, respectively. The further increase in the concentration of these substances decreases the SL intensity. The SL spectra of the solutions have a broad maximum at 450 nm. Excited SO₂ molecules formed in sulfuric acid due to sonolysis are luminescence emitters. The proposed mechanism of bright SL in these systems is based on the energy transfer from the electron-excited sonolysis products to the SO₂ molecules in cavitation bubbles.     

A pyrophosphate-responsive gadolinium(III) MRI contrast agent

This study shows that the relaxivity and optical properties of functionalised lanthanide‐DTPA‐bis‐amide complexes (lanthanide=Gd³⁺ and Eu³⁺, DTPA=diethylene triamine pentaacetic acid) can be successfully modulated by addition of specific anions, without direct Ln³⁺/anion coordination. Zinc(II)‐dipicolylamine moieties, which are known to bind strongly to phosphates, were introduced in the amide “arms” of these ligands, and the interaction of the resulting Gd–Zn₂ complexes with a range of anions was screened by using indicator displacement assays (IDAs). Considerable selectivity for polyphosphorylated species (such as pyrophosphate and adenosine‐5′‐triphosphate (ATP)) over a range of other anions (including monophosphorylated anions) was apparent. In addition, we show that pyrophosphate modulates the relaxivity of the gadolinium(III) complex, this modulation being sufficiently large to be observed in imaging experiments. To establish the binding mode of the pyrophosphate and gain insight into the origin of the relaxometric modulation, a series of studies including UV/Vis and emission spectroscopy, luminescence lifetime measurements in H₂O and D₂O, ¹⁷O and ³¹P NMR spectroscopy and nuclear magnetic resonance dispersion (NMRD) studies were carried out.     

Sonoluminescence of terbium chloride in an H2O-D2O mixture

The effect of solvent deuteration on the multibubble sonoluminescence (SL) of an aqueous solution of terbium chloride was studied. The dependence of the intensity of the characteristic SL of the Tb^III ion on the composition of an H₂O-D₂O mixture is similar to an analogous dependence of its photoluminescence (PL) but with a much smaller isotope effect. In pure D₂O, the SL intensity increases by 4 times only compared to the SL in water, while the PL intensity increases by 10 times. The mechanism of inner-bubble excitation of lanthanide ions is considered. According to this mechanism, an additional “heterogeneous” channel of quenching of excited Tb^III ions appears, which is absent for PL. The proposed model satisfactorily describes the experimental data on the effect of solvent deuteration on the SL intensity. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1074–1078, July, 2006.     

Dilute solution properties of poly(dimethyldiallylammonium chloride) in aqueous sodium chloride solutions

MW fractions of poly(dimethyldiallylammonium chloride) (PDMDAAC) were prepared by preparative size-exclusion chromatography and characterized by static and dynamic light scattering, viscometry, size-exclusion chromatography, and electrophoretic light scattering, in 0.50M NaCl solution. The behavior of fractions with MW < 2 × 10⁵ was as expected for a strong polyelectrolyte in a good solvent, with a Mark-Houwink exponent of ca. 0.8, and MW-dependencies of the hydrodynamic radius and the radius of gyration of corresponding magnitude. At higher MW, curvature appears in the MW-dependencies, which can be best explained by the presence of branching. While this notably lowers the intrinsic viscosity at high MW, the electrophoretic mobility is unchanged regardless of molar mass. Thus, the branched polymers display the electrophoretic free-draining behavior characteristic of linear polyelectrolytes. ©1995 John Wiley & Sons, Inc.     

Multibubble sonoluminescence of europium(III) chloride in heavy water

A weak glow in the region of the Eu³⁺ photoluminescence spectrum was detected against the background of the continuum of the solvent emission during multibubble sonolysis of air- or argon-saturated EuCl₃ solutions (0.1 mol L⁻¹) in heavy water. No characteristic sonoluminescence of the europium ion in aqueous solutions was observed earlier. Possible reasons for the low yield of Eu³⁺ sonoluminescence compared with other lanthanide ions (Ln³⁺) are discussed and the influence of europium on the spectrum of the solvent continuum related, in particular, to quenching of the electron-excited sonolysis products H₂O* (D₂O*) and Eu³⁺* in electron transfer reactions. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1793–1796, September, 2008.     

On the conductivity of an 0.01D aqueous potassium chloride solution

In a recent paper in this Journal, Saulnier and Barthel presented results for the electrolytic conductivity of 0.01 D potassium chloride solutions which they measured in a new type of conductance cell capable of absolute measurements at 0, 18 and 25°C. Their results disagreed by more than they expected from the results of Jones and Bradshaw at 18 and 25°C after they corrected the Jones and Bradshaw results to the absolute ohm and to the IPTS 1968. However their conversion was in error. The correct conversion is given and a recomparison is made with the Jones and Bradshaw results.     

Structure, stability, dynamics, high-field relaxivity and ternary-complex formation of a new tris(aquo) gadolinium complex

The tripodal hexadentate picolinate ligand dpaa3- (H3dpaa=N,N'-bis[(6-carboxypyridin-2-yl)methyl]glycine) has been synthesised. It can form 1:1 and 1:2 lanthanide/ligand complexes. The crystal structure of the bis(aquo) lutetium complex [Lu(dpaa)(H2O)2] has been determined by X-ray diffraction studies. The number of water molecules was determined by luminescence lifetime studies of the terbium and europium complexes. The tris(aquo) terbium complex shows a fairly high luminescence quantum yield (22 %). The [Gd(dpaa)(H2O)3] complex displays a high water solubility and an increased stability (pGd=12.3) with respect to the analogous bis(aquo) complex [Gd(tpaa)(H2O)2] (pGd=11.2). Potentiometric and relaxometric studies show the formation of a soluble GdIII hydroxo complex at high pH values. A unique aquohydroxo gadolinium complex has been isolated and its crystal structure determined. This complex crystallises as a 1D polymeric chain consisting of square-shaped tetrameric units. In heavy water, the [Gd(dpaa)-(D2O)3] complex shows a quite high HOD proton relaxivity at high field (11.93 s(-1) mM(-1) at 200 MHz and 298 K) because of the three inner-sphere water molecules. The formation of ternary complexes with physiological anions has been monitored by relaxometric studies, which indicate that even under conditions favourable to the formation of adducts with oxyanions, the mean relaxivity remains higher than those of most of the currently used commercial contrast agents except for the citrate. However, the measured relaxivity (r1=7.9 s(-1) mM(-1)) in a solution containing equimolar concentrations of [Gd(dpaa)(D2O)3] and citrate is still high. The interaction with albumin has been investigated by relaxometric and luminescence studies. Finally, a new versatile method to unravel the geometric and dynamic molecular factors that explain the high-field relaxivities has been developed. This approach uses a small, uncharged non-coordinating probe solute, the outer-sphere relaxivity of which mimics that of the water proton. Only a routine NMR spectrometer and simple mathematical analysis are required.     

Variation of luminescence properties of the reaction solution during preparation of a component of Ziegler-Natta catalyst by the reaction of Tb with Ph3CCl

Photoluminescence is used to test lanthanide-C bonds and to identify unstable intermediates in the synthesis of Ph₃CTbCl₂, a component of Ziegler-Natta catalyst.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2053–2055, October, 1995.     

Thermodynamics of calcium chloride in highly concentrated aqueous solution and in hydrated crystals

Measured values of the pressure of H₂O over saturated solutions in equilibrium with the dihydrate, tetrahydrate or hexahydrate of CaCl₂ are converted to osmotic coefficients and compared with literature values for solutions of smaller molality. It is found that the osmotic coefficient is constant, within the uncertainty, from about 7 mol-kg^–1 to soturation at all temperatures from 25 to 100°C. From this simple approximation, the activity coefficient is calculated for high molalities and at saturation. By combination of these results with other established data, entropies and Gibbs energies of formation are calculated for the crystalline hydrates of CaCl₂.     

Isopiestic measurements on aqueous mixtures of sodium chloride and strontium chloride

Isopiestic measurements have been made on NaCl–SrCl₂ mixtures at 25°C over the ionic strength range 0.6–6 mole-kg^–1. The results are interpreted in terms of current mixed-electrolyte treatments. The mixing behavior in this system is comparatively simple, but the Pitzer treatment is still clearly superior to the other treatments.     

双(2,4-二甲基戊二烯基)氯化钆的合成及晶体结构

合成双(2,4-二甲基戊二烯基)氯化钆{[2,4-(CH₃)₂C₅H₅]₂GD_cl}₂,并测定了晶体结构.晶体为单斜晶系,P2₁/n空间群.晶胞参数a=0.89141(18)nm,b=1.4486(3)nm,c=1.15925(15)nm,β=92.996(18)°,V=1.4949(4)nm³,Z=3.     

Enthalpy of crystallization of lithium chloride from aqueous solution at 25°C

The enthalpies of crystallization of LiCl and LiCl·H₂O from aqueous solutions at 25°C are reported as measured by a calorimetric method and derived from the previously published concentration dependence of the enthalpy of solution data. The results are compared with those obtained from the concentration dependence of activity coefficients and from the temperature dependence of solubilities.     

Thermal parameters associated to micellization of dodecylpyridinium bromide and chloride in aqueous solution

Electrical conductivity of aqueous solutions of dodecylpyridinium chloride and bromide have been determined. From these data the critical micelle concentration (cmc) was determined. The thermal properties as standard Gibbs free energy, enthalpy and entropy of micellization was estimated from a uncharged-phase separation model and enables to obtain another properties like heat capacity of micellization and the relevant parameters in the minimum of temperature dependence of cmc. The enthalpy-entropy compensation was shown for the studied compounds. This revised version was published online in July 2006 with corrections to the Cover Date.     

Adsorption of gadolinium on activated charcoal from electrolytic aqueous solution

Adsoprtion of gadolinium on activated charcoal has been studied as a function of shaking time, pH, concentration of adsorbate and temperature. Gadolinium adsorption obeys the Langmuir isotherm. H^o and S^o were calculated from the slope and intercept of the In K_D 1/T plot. The influence of different cations and anions on gadolinium adsorption has been examined. The adsorption of other metal ions on activated charcoal has been studied under optimum conditions to check the selectivity of gadolinium adsorption. Consequently, gadolinium was removed from Ni, V, Zn, Cu, Rb, Sr and Mn. More than 97% of the adsorbed gadolinium on activated charcoal can be recovered with 35 ml of 3M HNO₃ solution. Wavelength dispersive X-ray fluorescence spectrometer was used for measuring gadolinium concentration.     

Isopiestic study of the interactions between calcium chloride and methyl glycofuranosides in aqueous solution

Osmotic coefficients have been determined for three isomeric methyl glycofuranosides, viz. methyl -D-lyxo-, -D-ribo-, and -D-ribofuranosides in aqueous solution by the isopiestic comparison method. The method was further applied to measure the osmotic coefficients for the ternary system consisting of calcium chloride, methyl glycofuranoside, and water. The results are analyzed in terms of an excess function from which the salting constants for the glycosides are derived. Relationships between the salting constants and the complexing of methyl glycofuranosides with calcium ion are discussed.     

Sonoluminescence quenching by organic acids in aqueous solution: pH and frequency effects

The quenching of sonoluminescence from aqueous solutions by acrylic and methacrylic acids is dependent on whether the acid is ionised in solution, as controlled by the pH, but also by the frequency of ultrasound used.     

Hydration of lanthanoid(III) ions in aqueous solution and crystalline hydrates studied by EXAFS spectroscopy and crystallography: the myth of the "gadolinium break"

The structures of the hydrated lanthanoid(III) ions including lanthanum(III) have been characterized in aqueous solution and in the solid trifluoromethanesulfonate salts by extended X-ray absorption fine structure (EXAFS) spectroscopy. At ambient temperature the water oxygen atoms appear as a tricapped trigonal prism around the lanthanoid(III) ions in the solid nonaaqualanthanoid(III) trifluoromethanesulfonates. Water deficiency in the capping positions for the smallest ions starts at Ho and increases with increasing atomic number in the [Ln(H(2)O)(9-x)](CF(3)SO(3))(3) compounds with x=0.8 at Lu. The crystal structures of [Ho(H(2)O)(8.91)](CF(3)SO(3))(3) and [Lu(H(2)O)(8.2)](CF(3)SO(3))(3) were re-determined by X-ray crystallography at room temperature, and the latter also at 100 K after a phase-transition at about 190 K. The very similar Ln K- and L(3)-edge EXAFS spectra of each solid compound and its aqueous solution indicate indistinguishable structures of the hydrated lanthanoid(III) ions in aqueous solution and in the hydrated trifluoromethanesulfonate salt. The mean Ln--O bond lengths obtained from the EXAFS spectra for the largest ions, La-Nd, agree with estimates from the tabulated ionic radii for ninefold coordination but become shorter than expected starting at samarium. The deviation increases gradually with increasing atomic number, reaches the mean Ln-O bond length expected for eightfold coordination at Ho, and increases further for the smallest lanthanoid(III) ions, Er-Lu, which have an increasing water deficit. The low-temperature crystal structure of [Lu(H(2)O)(8.2)](CF(3)SO(3))(3) shows one strongly bound capping water molecule (Lu-O 2.395(4) A) and two more distant capping sites corresponding to Lu-O at 2.56(1) A, with occupancy factors of 0.58(1) and 0.59(1). There is no indication of a sudden change in hydration number, as proposed in the "gadolinium break" hypothesis.