Sorption of phosphate ions with materials based on titanium and lanthanum hydroxides

The possibility of preparing lanthanum(III) hydroxide and a 1:1 mixture of lanthanum(III) hydroxide with hydrated titania by precipitation from aqueous solutions was explored. The maximal sorption capacities of the mixture with respect to phosphate ions in acid and alkaline media were determined. The mechanism by which phosphates are removed was elucidated by IR spectroscopy.     

Gamma-induced radiation polymerization of kaolin composite for sorption of lanthanum,europium and uranium ions from low-grade monazite leachate

Gamma radiation polymerization method was used for the modification of kaolin to produce (poly acrylamide-acrylic acid)-Kaolin (PAM-AA-K). Monazite ore is one of the main resources of uranium and lanthanide elements, therefore, this work focused on sorption of uranium, lanthanum and europium ions from low grade monazite leachate. The removal percent for Eu³⁺, La³⁺ and UO₂ ²⁺ are 94.6, 91.6 and 73.4%, respectively. Monolayer capacity of Eu³⁺, La³⁺ and UO₂ ²⁺ were found to be 54.64, 45.87 and 37.59 mg/g, respectively. The sorption mechanism of lanthanum and europium ions on PAM-AA-K composite mainly takes place as Ln(OH)²⁺, and for uranium as uranyl ion, UO₂ ²⁺.     

Optical and structural investigation of the lanthanum β-alumina phase doped with europium

The lanthanum β-alumina phase doped with europium was investigated by X-ray diffraction and fluorescence. This nonstoichiometric phase exists over the composition range: $\text{11}\text{Al}{}_2\text{O}{}_3\text{1}\text{La}{}_2\text{O}{}_3$ to $\text{14}\text{Al}{}_2\text{O}{}_3\text{1}\text{La}{}_2\text{O}{}_3$. The unit cell is hexagonal hexagonal with a = 5.560 ± 0.003 Å, c = 22.001 ± 0.003 Å and belongs to the $\text{P6}{}_3\text{mmc}$ space group. X-ray diffraction patterns do not vary between both boundary compositions, but fluorescence spectra show that the structure of the mirror plane in which the lanthanide ions are located is deeply modified. The atomic structure of the mirror plane is of “β-type” (like β(Na) or β(Ag)) for the lower alumina contents; it gradually changes to a “magnetoplumbite type” for higher alumina contents.     

The influence of pH on the stability constants of lanthanum and europium complexes with humic acids

Complex formation of humic acids (HA)_n with La³⁺ and Eu³⁺ was studied. Commercial (HA)_n was purified and characterized. The stability constants were determined at several pH values and 0.2?M NaClO₄ ionic strength by the Shubert??s method of radiochemical ionic exchange. The slopes of the lines $ \log ((\lambda_{0} /\lambda ) - 1) = \log \beta_{\text{M,j(HA)n}}^{\exp } + {\text{j}} * \log \left[ { ( {\text{HA)}}_{\text{n}} } \right] $ were dependent on the [(HA)_n]. The values of log $ \beta_{\text{M,j(HA)n}}^{\exp } $ for j?=?1 were the following: 6.29?±?0.04 (pH 4.9?±?0.4) and 7.61?±?0.03 (pH 5.9?±?0.1) for lanthanum and 7.31?±?0.01 (pH 5.9?±?0.2) for europium. Log $ \beta_{\text{M,j(HA)n}}^{\exp } $ was determined as well for higher values of the j parameter and these values were: 12.2?±?0.1 (j?=?2, pH 7.7?±?0.2), 15.6?±?0.2 (j?=?3, pH 4.9?±?0.4) and 16.05?±?0.07 (j?=?3, pH 5.9?±?0.1), for lanthanum and 13.18?±?0.03 (j?=?2, pH 5.9?±?0.1) for europium. A discussion is presented about the complex formation regarding pH and [(HA)_n].     

Rapid naked-eye detection of mercury ions based on non-crosslinking aggregation of double-stranded DNA-carrying gold nanoparticles

Colorimetric detection of mercury ions (Hg(2+)) with the naked eye was accomplished within 1 min by a combination of non-crosslinking aggregation of double-stranded DNA-carrying gold nanoparticles and complex formation of thymine-Hg(2+)-thymine.     

Highly selectively monitoring heavy and transition metal ions by a fluorescent sensor based on dipeptide

Fluorescent sensor (DMH) based on dipeptide was efficiently synthesized in solid phase synthesis. The dipeptide sensor shows sensitive response to Ag(I), Hg(II), and Cu(II) among 14 metal ions in 100% aqueous solution. The fluorescent sensor differentiates three heavy metal ions by response type; turn on response to Ag(I), ratiometric response to Hg(II), and turn off detection of Cu(II). The detection limits of the sensor for Ag(I) and Cu(II) were much lower than the EPA's drinking water maximum contaminant levels (MCL). Specially, DMH penetrated live cells and detected intracellular Ag⁺ by turn on response. We described the fluorescent change, binding affinity, detection limit for the metal ions. The study of a heavy metal-responsive sensor based on dipeptide demonstrates its potential utility in the environment field.     

Electronic structure of brain: structure-activity relationships between electronic structure and neurotransmitters based on molecular hardness concept

In order to understand the relation between the electronic structure of neurotransmitters and the brain, a model of the brain based on absolute hardness (eta) and absolute electronegativity (chi) is described. It was found that the coordinate r(chi, eta) of electronic structures of neurotransmitters obtained using the parameters eta and chi can be graphically classified into three groups: catecholamine type (group I), gamma-aminobutanoic acid (GABA) type (group II), and acetylcholine (ACh) type (group III) in the eta-chi diagram. The results suggest that the brainstem and neocortex in the brain are chemically soft and hard, respectively, because they show that the myelinated nerve is chemically soft and the unmyelinated nerve is chemically hard. If one calculates the r(chi, eta) to understand which group a drug belongs to, one can predict the target receptors of the drug from the eta-chi diagram. Using eta-chi maps, one is then able to design medications like antidepressants, tranquilizers, and ACh agonists.     

Selective complexation and transport of europium ions at the interface of vesicles

The aim of the present work was to design functionalized lipidic membranes that can selectively interact with lanthanide ions at the interface and to exploit the interaction between membranes induced by this molecular-recognition process with a view to building up self-assembled vesicles or controlling the permeability of the membrane to lanthanide ions. Amphiphilic molecules bearing a beta-diketone unit as head group were synthesized and incorporated into phospholipidic vesicles. Binding of Eu(III) ions to the amphiphilic ligand can lead to formation of a complex involving ligands of the same vesicle membrane (intravesicular complex) or of two different vesicles (intervesicular complex). The effect of Eu(III) ions on vesicle behavior was studied by complementary techniques such as fluorimetry, light scattering, and electron microscopy. The formation of an intravesicular luminescent Eu/beta-diketone ligand (1/2) complex was demonstrated. The linear increase in the binding constant with increasing concentration of ligands in the membrane revealed a cooperative effect of the ligands distributed in the vesicle membrane. The luminescence of this complex can be exploited to monitor the kinetics of complexation at the interface of the vesicles, as well as ion transport across the membrane. By encapsulation of 2,6-dipicolinic acid (DPA) as a competing ligand which forms a luminescent Eu/DPA complex, the kinetics of ion transport across the membrane could be followed. These functional vesicles were shown to be an efficient system for the selective transport of Eu(III) ions across a membrane with assistance by beta-diketone ligands.     

Selective lanthanum ions optical sensor based on covalent immobilization of 4-hydroxysalophen on a hydrolyzed triacetylcellulose membrane

An optical sensor membrane is described for the determination of lanthanum(III) ions based on the immobilization of 4-hydroxysalophen on a hydrolyzed triacetylcellulose membrane. 4-Hydroxysalophen is covalently bonded to a transparent hydrolyzed triacetylcellulose film. The sensing membrane in contact with lanthanum ions at pH 4.0 changes color from white-yellow to orange (323 to 433 nm). Under the optimum conditions, the proposed membrane displayed a linear range from 1.0 × 10⁻⁶ to 1.0 × 10⁻² M La(III) with a limit of detection of 1 × 10⁻⁷ M. The response time of the membrane was within 5–6 min depending on the concentration of La(III) ions. The selectivity of the probe towards lanthanum ions was found to be excellent. The sensor was successfully applied to the determination of La(III) in water, industrial waste water, and in NIST-615 (glass matrix) and NIST-3127a (lanthanum solution) samples with satisfactory results.     

Effect of chelation to lanthanum ions on the photodynamic properties of hypocrellin A

Hypocrellin A (HA), an efficient phototherapeutic agent, can chelate with lanthanum ion to form a 1:1 complex, which exhibits enhanced 1O2 generation quantum yield, a red-shifted absorption window, greatly improved water solubility, a much lengthened triplet excited state lifetime, and an increased affinity to DNA with respect to HA. These effects in turn lead to a more potent photodamage ability on calf thymus DNA for La3+-HA than HA in both aerobic and anaerobic conditions, indicating the potential application of La3+-HA in the field of photodynamic therapy (PDT).     

Luminescence of terbium and europium ions in metal-polymer complexes based on poly(amido acids) with main-chain arylcarboxyamide groups

Poly(amido acids) with main-chain metal-binding ligands methylene-bis(anthranilic acid) and their linking fragments of a widely varied structure have been synthesized. The chemical structure of poly(amido acids) that affect the luminescence of Tb³⁺ and Eu³⁺ ions and interact with them is studied, and the mechanism of this effect is advanced.     

A fast assay of water hardness ions based on alkaline earth metal induced coacervation (HALC)

In this work, a rapid assay of water hardness is presented based on the formation of a coacervate phase made up of multilamellar vesicles and close bilayers produced upon the reaction of alkaline earth metals with a carboxylate anionic surfactant in the presence of a co-surfactant (methanol). The procedure exploits the light scattering abilities of the coacervate phase which can be logarithmically linked to total hardness as CaCO₃ equivalents via spectrophotometric detection at 350 nm. The method, abbreviated as HALC, stemming from hardness by alkaline earth metal coacervation, is straightforwardly applicable overcoming the requirement for regulation of the experimental parameters involved in the determination procedure. In total, 28 water samples with various matrix compositions and hardness contents were analyzed with satisfactory accuracy as evidenced by comparison of the results with EDTA complexometric titration. The method is free from interferences from environmentally significant metal cations and inorganic anions affording detection limits as low as 13.5 mg L⁻¹ CaCO₃ with the aid of a correction factor, which is determined by the non-linear absorbance properties of the solution mixture, and satisfactory reproducibility (RSD = 4.21-8.08%).     

Stereo structure-controlled and electronic structure-controlled estrogen-like chemicals to design and develop non-estrogenic bisphenol A analogs based on chemical hardness concept

The aim of this study was to elucidate the structure-activity relationship of bisphenol A (BPA) analogs using absolute hardness (eta) and absolute electronegativity (chi) (chemical hardness) and to design a non-estrogen active BPA. To determine the structure-activity relationships of BPA analogs, we investigated MCF-7 cell proliferation stimulated by BPA analogs and an eta-chi diagram based on the electronic structure of the BPA analogs. The results show that the actions of the environmental hormones BPA analogs have two chemical properties; (i) 'stereo structure-controlled' and (ii) 'electronic structure-controlled' estrogen-like chemical activities. Therefore, we designed and synthesized BPA analogs which do not possess these 2 characteristics, ((i) and (ii)), and demonstrate the non-estrogen activity of the analog.     

Prediction of endocrine disruptors based on a new structure-activity relationship for sex and environmental hormones using chemical hardness concept.

Classification of the relationship between electronic structures and biological activities of endocrine disruptors (so-called environmental hormones) was attempted using the parameters of absolute hardness (eta), absolute electronegativity (chi), and global softness (S), approximately defined as eta=1/2(epsilonLUMO-epsilonHOMO), chi=-1/2(epsilonHOMO+ epsilonLUMO), and S=1/eta, respectively, based on the hardness concept. The strength of binding affinity and toxicity of the chemicals were approximately proportional to the absolute hardness, and laterally toxic chlorinated PCDDs, PCBs, and DDTs are classified as chemically soft. Here we found that the electronic structures of environmental hormones can be classified into four main groups: 17beta-estradiol type (group I), testosterone type (group II), thyroxine type (group III), and HCH (hexachlorocyclohexane) type (group IV). Therefore, if we can predict the coordinate (chi, eta) of the electronic structure of one chemical on the eta-chi activity diagram, we would be able to predict the receptor with which the chemicals (environmental hormones) interact. For instance, 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) is classified in group II, therefore, it would bind with the thyroid receptor more than the estrogen receptor (group I). It appears that dibutyl phthalate would not interact with estrogen receptor because it does not belong to group I. In addition, the coordinates of these four groups do not complementarily overlap with the electronic structures of 20 natural amino acid residues. The eta-chi activity diagram is a new tool for the prediction of the toxicity and biological activity of environmental hormones.     

Direct detection and discrimination of double-stranded oligonucleotide corresponding to hepatitis C virus genotype 3a using an electrochemical DNA biosensor based on peptide nucleic acid and double-stranded DNA hybridization

Development of an electrochemical DNA biosensor for the direct detection and discrimination of double-stranded oligonucleotide (dsDNA) corresponding to hepatitis C virus genotype 3a, without its denaturation, using a gold electrode is described. The electrochemical DNA sensor relies on the modification of the gold electrode with 6-mercapto-1-hexanol and a self-assembled monolayer of 14-mer peptide nucleic acid probe, related to the hepatitis C virus genotype 3a core/E1 region. The increase of differential pulse voltammetric responses of methylene blue, upon hybridization of the self-assembled probe with the target ds-DNA to form a triplex is the principle behind the detection and discrimination. Some hybridization experiments with non-complementary oligonucleotides were carried out to assess whether the developed DNA sensor responds selectively to the ds-DNA target. Diagnostic performance of the biosensor is described and the detection limit was found to be 1.8 × 10⁻¹² M in phosphate buffer solution, pH 7.0. The relative standard deviation of measurements of 100 pM of target ds-DNA performed with three independent probe-modified electrodes was 3.1%, indicating a remarkable reproducibility of the detection method.     

Influence of temperature on the colloidal stability of the F-DPPC and DPPC liposomes induced by lanthanum ions

The influence of La(3+) on the colloidal stability of liposomes made up by two zwitterionic phospholipids, 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and 1-palmitoyl-2-[16-fluoropalmitoyl-phosphatidylcholine (F-DPPC), in aqueous media has been investigated by dynamic light scattering and electrophoretic mobility. The critical aggregation concentration (c.a.c.) of La(3+) for F-DPPC and DPPC liposomes were experimentally obtained, and the results were compared with theoretical predictions using the Derjaguin-Landau-Verwey-Overbeek theory. In order to evaluate the influence of the state of the bilayer on the stability of liposomes, all experiments were performed at temperatures below and above the chain-melting phase-transition temperature of lipids (transition temperature of lipids). Changes in the size of both types of liposomes and high values of polydispersity in the presence of La(3+) showed that these ions induce aggregation of liposomes at 25 °C and at 60 °C. At 25 °C, when the bilayer of F-DPPC liposomes is interdigited, DPPC liposomes are more resistant to aggregation than the liposomes formed with F-DPPC. However, this difference disappears at 60 °C, when both bilayers have the same conformation. The experimental results also indicate that the c.a.c. is higher at 60 °C than at 25 °C for both types of liposomes. In fact, it has been observed by dynamic light scattering measurements that aggregation of liposomes at 25 °C can be prevented by increasing the solution temperature for La(3+) concentrations near to the c.a.c. Moreover, the behavior of these liposomes in the presence of the ion was studied at temperatures above and below the transition temperature of the phospholipids.     

Molecular dynamics study of the hydration of lanthanum(III) and europium(III) including many-body effects

Lanthanides complexes are widely used as contrast agents in magnetic resonance imaging (MRI) and are involved in many fields such as organic synthesis, catalysis, and nuclear waste management. The complexation of the ion by the solvent or an organic ligand and the resulting properties (for example the relaxivity in MRI) are mainly governed by the structure and dynamics of the coordination shells. All of the MD approaches already carried out for the lanthanide(III) hydration failed due to the lack of accurate representation of many-body effects. We present the first molecular dynamics simulation including these effects that accounts for the experimental results from a structural and dynamic (water exchange rate) point of view.     

Photoionization of lanthanum and its ions in the region of the “giant” resonance

The photoionization cross sections of outer and intermediate shells including 4d of La and its ions are calculated in the region of the “giant” resonance. The prominent effects of both intershell correlational effects and rearrangement are demonstrated.     

Effect of sulfate additives on the 60Co gamma ray induced decomposition of lanthanum,europium and terbium nitrates in solid state

Gamma radiolysis of binary mixtures of La(NO₃)₃·6H₂O, Eu(NO₃)₃·6H₂O and Tb(NO₃)₃·6H₂O along with their respective sulfates have been studied over a wide range of absorbed doses up to 500 kGy. Radiolytic decomposition of the nitrate salts is affected by the concentration of the sulfate in the binary mixture as well as on the absorbed dose. G(NO₂⁻) values calculated on the basis of electron fraction of the nitrate salt in the binary mixture are enhanced by 10²–10³ times at >90 mol% of the sulfate additive. A study of binary mixtures of lanthanum nitrate with other mono-, bi-, tri- and tetra-valent sulfate additives shows that G(NO₂⁻) values are also affected by the nature and oxidation state of the cation including electron configuration. ESR and TL measurements suggest the formation of radical species, which may interact with the radical species of nitrate (NO₃²⁻, NO₂ etc.) causing enhanced decomposition by energy transfer. A possible mechanism of decomposition has been suggested. Anomalous behavior of Eu(NO₃)₃·6H₂O has been correlated with the electronic configuration and +2 oxidation state of Eu.