Luminescence spectra fine structure for uranyl sulfate and oxalate crystals

Quasi-line low-temperature (T = 77 and 4.2 K) luminescence spectra of uranyl sulfates and oxalates have been recorded and analyzed. It has been shown that the spectral structure is determined by the manifestation of the internal and external vibrations of both the uranyl ion and molecular groups (SO₄)^2– and (C₂O₄)^2–bonded to the uranyl ion. The spectral line half-width is of the order of ≈5–7 cm^–1; the line shape, close to Lorentzian. The fluorescence spectra may be complicated by structural defects in the crystals.     

Spectral and Structural Regularities Exhibited by Tri- and Tetranitrate Uranyl Complexes in the Crystalline State

Based on an analysis of the low-temperature luminescence spectra of tri- and tetranitrate uranyl compounds, the influence exerted by the nature of outer-sphere cations (Na, K, Rb, NH₄, and Cs) on the position of a purely electron transition in the uranyl ion has been studied. Linear correlation dependences of the position of a purely electron transition on the value of the ionization potential of cations have been established. It is shown that the upper occupied molecular orbital, whose position is determined by the total donating capacity of ligands and their number, is essentially of ligand character.     

Origin of near constant loss (NCL) in ion conducting polymer blends

We report a novel observation pertaining to scaling behavior and near constant loss response in ion conducting polymer blends. This type of response evidenced by linear plot of conductivity spectrum at high frequency has rarely been reported for polymer blends. It is noted that at a fixed cation concentration in the polymer blends high frequency dielectric loss remains constant irrespective of temperature confirming near constant loss (NCL). However the onset of such response is prominent in sub-ambient temperature limit vis-à-vis ambient condition. It is also noted that low temperature NCL response depends on cation loading in the polymer blend matrix. These results, reported for the first time for an ion conducting polymer blend has been explained using Kramer–Kröinig (KK) and Haveriliak Negami (HN) equation.     

First-principles molecular dynamics simulations of uranyl ion interaction at the water/rutile TiO2(110) interface

The effects of temperature and solvation on uranyl ion adsorption at the water/rutile TiO₂(110) interface are investigated by Density Functional Theory (DFT) in both static and Born–Oppenheimer molecular dynamics approaches. According to experimental observations, uranyl ion can form two surface complexes in a pH range from 1.5 to 4.5. Based on these observations, the structures of the complexes at 293 K are first calculated in agreement with vacuum static calculations. Then, an increase in temperature (293 to 425 K) induces the reinforcement of uranyl ion adsorption due to the release of water molecules from the solvation shell of uranyl ion. Finally, temperature can modify the nature of the surface species.     

Electronic Spectra and the Mechanism of Complexing of Uranyl Nitrate in Water–Acetone Solutions

Based on the analysis of electronic absorption and luminescence spectra, the processes of complexing in an aqueous solution of uranyl nitrate hexahydrate (UO₂(NO₃)₂·6H₂O) on gradual addition of small amounts of acetone have been investigated. In a pure aqueous solution, uranyl exists as the UO₂·5H₂O complex. It is shown that addition of acetone to the solution leads to displacement of some water molecules from the first coordination sphere of uranyl and formation of uranyl nitrate dihydrate complexes, UO₂(NO₃)₂·2H₂O. It has been established that the stability of these complexes is determined by the decrease in both the water activity and the degree of hydration of uranyl and nitrate. This is the result of the local increase in the concentration of the molecules of acetone (due to its hydrophobicity) in those regions of the solution in which there are uranyl and nitrate ions. The experimental facts supporting the proposed mechanism are given.     

Vibrational Spectra of Oxalate Complexes of Uranyl with Neutral Organophosphorus Ligands

The vibrational spectra of a number of polycrystalline oxalate complexes of uranyl with neutral organophosphorus ligands have been investigated. Based on the empirical formula of the compounds, the results of the analysis of experimental IR absorption spectra and Raman spectra, and the data of calculation of the frequencies and forms of normal vibrations, a possible structure of the complexes is suggested. A fragment of the structure of any member of this series can be represented as a polymer chain formed by bridge C₂O₄ ^2– groups. The coordination sphere of uranyl is complemented by the oxygen of phosphine oxide, and the hydrocarbon radical is positioned on either side of the polymer chain.     

Photoconversion and photocatalytic activity of uranyl in acetone solutions

We have studied the effect of irradiation on the uranyl nitrate — acetone and uranyl perchlorate — acetone systems. We have established that when the uranyl perchlorate — acetone system is irradiated, polymerization of the acetone occurs and the catalyst for the process is excited uranyl complexes. In the polymer, uranium is found in the form of nanoclusters of pentavalent and tetravalent uranium, formed as a result of photochemical reactions. Polymerization does not occur in the uranyl nitrate — acetone system. We consider possible factors responsible for the noted differences. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 5, pp. 565–568, September–October, 2007.     

Radical-Recombination Luminescence of the Uranyl Nitrate Complex in the Adsorbed State

We have investigated the luminescence of uranyl nitrate molecules on the surface of powdery SiO₂ upon excitation by UV light (PhL) and hydrogen atoms (radical-recombination luminescence (RRL)). It has been found that the PhL and RRL spectra have a clearly defined vibrational structure. The luminescence peaks of the adsorbed UO₂ ^2– ion are characterized by a systematic longwave shift from the same peaks of crystalline uranyl nitrate (by 230–430 cm^–1 at 130 K). Moreover, in the adsorption centers the vibration frequencies of UO₂ ^2– are 20–80 cm smaller than in crystalline salt and the RRL bands are 150–350 cm^–1 (130 K) wider than the corresponding PhL bands.     

Lithium ion conductivity and dielectric properties of P(VdCl-co-AN-co-MMA)-LiCl-EC triblock co-polymer electrolytes

Lithium ion conducting polymer electrolytes based on triblock polymer P(VdCl-co-AN-co-MMA)–LiCl were prepared using a solution casting technique. XRD studies show that the amorphous nature of the polymer electrolyte has been increased due to the addition of LiCl. The maximum amorphous nature has been observed for 40 m% P(VdCl-co-AN-co-MMA)/60 m% LiCl samples. The FTIR study of the lithium ion conducting polymer membrane confirms the complex formation between the polymer P(VdCl-co-AN-co-MMA) and LiCl. The lithium ion conductivity is found to be 1.6 × 10^?5 Scm^?1 for the 40 m% P(VdCl-co-AN-co-MMA)/60 m% LiCl sample at room temperature. This value is found to be greater than that of pure polymer whose conductivity is found to be 1.5 × 10^?8 Scm^?1. To improve ionic conductivity, ethylene carbonate has been added as a plasticizer to the 40 m% P(VdCl-co-AN-co-MMA)/60 m% LiCl sample. When we add 0.6 m% of ethylene carbonate, it has been observed that the lithium ion conductivity has increased to 1.3 × 10^?3 Scm ^?1 . This value is two orders of magnitude greater than the 40 m% P(VdCl-co-AN-co-MMA)/60 m% LiCl sample. It is also observed from XRD patterns of 40 m% P(VdCl-co-AN-co-MMA)/60 m % LiCl/0.6 m % EC that the amorphous nature has been increased further. A dielectric study has been performed for the above membranes.     

A comparative study of the structure and cytotoxicity of polytetrafluoroethylene after ion etching and ion implantation

The ion-plasma treatment has been widely used for modifying the surface structure of polymers in order to improve their properties, but it can lead to destruction of the surface and, as a consequence, to an increase in their toxicity. A comparative study of the structure and cytotoxicity of polytetrafluoroethylene (PTFE) after the ion etching (IE) and ion implantation (II) for 10 min with energy densities of 363 and 226 J/cm², respectively, has been performed. It has been shown that, unlike the ion implantation, the ion etching results in the destruction of the polymer and in the appearance of the cytotoxicity. The factors responsible for this effect, which are associated with the bulk and surface treatment, as well as with the influence of the temperature, have been discussed.     

Generation of ions in a pulsed ion source with an interface based on a polymer track membrane

The time-of-flight spectra of ions generated during the extraction of negative ions from the KI solution in water–glycerin mixture by high-strength electric field pulses are studied using a source with an interface based on a polymer track membrane. It has been shown that the ions formed in secondary processes of bombardment of the membrane surface make a considerable contribution to the observed spectra. It has been found that the peaks of negative hydrogen ions have the highest intensity in the spectrum, indicating effective emission of these ions during the bombardment of polyethylene terephthalate by secondary ions with an energy of about 6 keV. The main trends in the modification of the membrane interface to reduce the fraction of secondary ions in the ion beam have been outlined.     

Luminescent Hybrid Materials Based on Polymers of Poly(Alpha-Fluoroacrylates) Doped with Tb(III) Complex

This study is devoted to the development of efficient luminescent hybrid materials excited by UV radiation and featuring narrow luminescence lines as well as light, humidity, and temperature resistance. As a luminescent material, a terbium ion coordination compound introduced into the matrix of an organofluorine polymer is used. It has been shown that efficient excitation transfer to electronic levels of the terbium ion can be achieved by proper ligand selection. The polymer matrix material does not affect the luminescence properties of the Tb(III) coordination compound.     

The effect of angle of incidence to low damage sputtering of organic polymers using a C60 ion beam

The effect of angle of incidence of C₆₀ ion beam for low damage polymer depth profiling on TOF-SIMS and XPS has been investigated. In this study, TOF-SIMS and XPS depth profiles were taken at several angles of incidence of C₆₀ ion beam and the results were compared with each other. By using a higher angle of incidence, in XPS analysis, the changes of atomic concentration for polyethyleneterephthalate (PET) were suppressed. In TOF-SIMS analysis, the degradations of fragment ion intensity for PET and polystyrene (PS) were also suppressed at a higher angle of incidence. Although the information depth of TOF-SIMS is different from that of XPS, both results suggested that a higher angle of incidence is a better condition for low damage polymer depth profiling.     

Luminescence of uranyl nitrate trihydrate crystals at high exciting-light intensities

The characteristic features of the luminescence of uranyl nitrate crystals at high excitation power densities have been considered. It is shown that there occurs accumulation of excitations in a system of uranyl centers, whereas the presence of forced absorption enhances the migration processes over the uranyl complexes. An increase in the power density of excitation leads to the amplification of interaction of the lower excited electronic states and to an increase in the degree of the system nonadiabaticity. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 6, pp. 743–746, November–December, 2005.     

Raman spectra of solutions of uranyl compounds

The frequencies of the spectra of aqueous and nonaqueous solutions of a number of uranyl salts were analyzed. The previous assignment of the frequency of 200 cm^–1 to the deformational vibrations of the uranyl ion [1] was confirmed. The activity of this frequency in the Raman spectrum is determined by the structure of the complex compounds.     

Donor Properties of Ligands and the Structure and Spectra of Uranyl Halogenides in the Solid State

Complexes of uranyl halogenides with neutral organic ligands in the solid state have been obtained, the luminescence spectra at T = 77 K have been recorded, and the dependences of them on the composition of the complex have been investigated. The linear dependence of the change in the frequencies of electron and vibronic transitions on the donor number of the neutral ligands has been revealed, thus allowing us to propose a spectral method for determining the structure of the system studied. It is shown that the increased strength of the bond of some halogen ligands (in particular, fluorine) with uranyl favors the nonsaturation of their inner coordination sphere. At the same time, the most stable complexes of the substances considered are formed when two halogen ions are supplemented with three molecules of organic ligand.     

Polymer electrolytes for lithium ion batteries: a critical study

Polymer electrolytes (PEs) are an essential component being used in most energy storage/conversion devices. The present review article on a brief history, advantage, and their brief application of polymer electrolyte systems. It consists of a glimpse on liquid, gel, and solid polymer electrolyte and a contrast comparison concerning benefits/disadvantages among the three. The article started with a brief introduction of polymer electrolytes followed by their varieties and extreme uses. The role of host polymer matrix by taking numerous examples of polymer electrolyte published by the different renowned group of the concerned field has been explored. The criteria for selection of appropriate host polymer, salt, inorganic filler/clay, and aprotic solvents to be used in polymer electrolyte have been discussed in detail. The mostly used polymer, salt, solvents, and inorganic filler/clay list has been prepared in order to keep the data bank at one place for new researchers. This article comprises different methodologies for the preparation of polymer electrolyte films. The different self-proposed mechanisms (like VTF, WLF, free volume theory, dispersed/intercalated mechanisms, etc.) have been discussed in order to explain the lithium ion conduction in polymer electrolyte systems. A numerous characterization techniques and their resulting analysis have been summarized from the different published reports at one place for better awareness of the scientific community/reader of the area.     

Extraction of local coordination structure in a low‐concentration uranyl system by XANES

Obtaining structural information of uranyl species at an atomic/molecular scale is a critical step to control and predict their physical and chemical properties. To obtain such information, experimental and theoretical L₃‐edge X‐ray absorption near‐edge structure (XANES) spectra of uranium were studied systematically for uranyl complexes. It was demonstrated that the bond lengths (R) in the uranyl species and relative energy positions (ΔE) of the XANES were determined as follows: ΔE₁ = 168.3/R(U—O_ax)² ? 38.5 (for the axial plane) and ΔE₂ = 428.4/R(U—O_eq)² ? 37.1 (for the equatorial plane). These formulae could be used to directly extract the distances between the uranium absorber and oxygen ligand atoms in the axial and equatorial planes of uranyl ions based on the U L₃‐edge XANES experimental data. In addition, the relative weights were estimated for each configuration derived from the water molecule and nitrate ligand based on the obtained average equatorial coordination bond lengths in a series of uranyl nitrate complexes with progressively varied nitrate concentrations. Results obtained from XANES analysis were identical to that from extended X‐ray absorption fine‐structure (EXAFS) analysis. XANES analysis is applicable to ubiquitous uranyl–ligand complexes, such as the uranyl–carbonate complex. Most importantly, the XANES research method could be extended to low‐concentration uranyl systems, as indicated by the results of the uranyl–amidoximate complex (～40 p.p.m. uranium). Quantitative XANES analysis, a reliable and straightforward method, provides a simplified approach applied to the structural chemistry of actinides.     

一种新型锂离子电池聚合物电解质的光谱学研究

本文主要利用Raman光谱对由丙烯碳酸酯(PC)/聚丙烯腈(PAN)/双三氟甲基碘酸酰亚胺锂(LiTFSI)组成的锂离子电池聚合物电解质进行了研究,通过研究发现:Li+离子与PC的缔合和PC对TFSI-阴离子结构的影响导致了Li+-PC-TFSI-离子团的生成。而在所有的PC分子和盐发生缔合之前,PAN却不能溶到PC中。一旦PAN开始溶于PC,电解质内与PC相关的微观结构将不再随盐的浓度的增加而改变。但Li+离子与PAN之间的作用却显得异常激烈。     

Graft polymerization into the latent tracks of some perfluoropolymers films irradiated by heavy ions

The results of the graft polymerization of methacrylic acid into perfluoropolymers (the copolymer of tetrafluoroethylene with hexafluoropropylene, copolymer of tetrafluoroethylene with perfluoroallylether) irradiated with heavy ions (Kr, 430 MeV) are presented. It has been found that the graft polymer quantity depends upon the polymer nature and the ion fluence. The graft polymer amount and its penetration depth were measured by the weighting methods, the dye sorption and electron microscopy methods. The graft polymerization results in significant changes in the polymer volume and structure.