Multi-ion and pH sensitivity of AgGeSe ion selective electrodes

Many chalcogenide glasses have been found to combine benefits such as good chemical durability, selectivity, and reproducibility for applications as solid-state sensitive membranes of ion selective electrodes (ISEs). In previous works, we have shown that ISEs with ionic conductive AgGeSe membranes have good sensitivity to Ag⁺ ions. In the present work, we explore the Ag_x(Ge_0.25Se_0.75)_100−x, 10≤x≤30 (at%) system as candidate for ISEs applications detecting several other ions (K⁺, Mg²⁺, Cr³⁺, Fe³⁺, Ni²⁺, Cd²⁺, Hg²⁺, and Pb²⁺). We evaluated ISEs fabricated with bulk as well as with thin film membranes. We found no dependence of the sensing properties on the Ag content of the ionic conductive membranes. Thin films exhibited the same properties than bulk membranes, indicating that these chalcogenide glasses have great potential for miniaturization. The ISEs showed a high response (Nernstian or super-Nernstian) to the presence of Hg²⁺, Pb²⁺, and Fe³⁺, a low response (sub-Nernstian) to the presence of Cr³⁺, and a total lack of response to the presence of Cd²⁺, Ni²⁺, Mg²⁺, and K⁺. We also tested how the pH of the solution affected the response of the ISEs. The potentials of the ISEs were practically constant in neutral or acidic solutions, while decreased drastically in basic solutions when the primary ion was not present. The latter phenomenon was caused by the slow dissolution of the membrane into the solution, meaning that long-term basic environments should be avoided for these ISEs. We concluded that ISEs with ionic conductive AgGeSe membranes are good candidates to integrate multi-electrode systems.     

化合物和合金中离子投影射程分布矩的计算(Ⅱ)——轻离子(Z1≤10)的射程分布矩

本文根据离子在固体材料中电子阻止截面的实验资料,给出了低能Li⁺,Be⁺,B⁺,C⁺,N⁺,O⁺,F⁺,Ne⁺等离子在固体中电子阻止截面S_e的经验公式。这些经验公式既能够很好地反映电子阻止本领的Z₁和Z₂振荡、又能正确地给出S_e随离子能量E的变化关系。用这种以实验为基础的S_e经验公式和符合于WHB势的核散射函数,计数了从H⁺到Ne⁺十种轻离子在非晶Al₂O₃,SiO₂,20/25/Nb不锈钢,LiNbO₃和UO₂等材料中的投影射程分布的一次至三次矩。将计算值与近几年的实验测量及其他人的计算结果进行了比较,在低能端,我们计算的平均投影射程R_p与实验符合得更好。 关键词：     

New books

Under low energy sputtering conditions (e.g. Ar⁺ ions, 300 eV, 10^?8A cm^?2) the Secondary Ion Mass Spectra show almost only those polyatomic ions which correspond to the arrangement of the atoms in the crystal structure. This method for obtaining structural information is demonstrated on a single crystal of cubic ZnS. In the SIMS for this pure ZnS crystal mainly polyatomic ions such as (ZnS)⁺, (ZnS)^?, (ZnSZn)⁺, (SZnS)^?, etc. were observed. Other polyatomic ions such as (Zn₂)⁺ or (S₂^?), which are not originally present in the crystal, are observed only in a very low counting rate ratio. An increase in the energy of the primary ions causes larger clusters of atoms of the crystal to be taken off, as well as polyatomic ions which do not correspond to the original structure. These effects and the influence of the crystallographic orientations are demonstrated on single crystals of CaF₂. Two applications of this method are discussed: the determination of S₂ content in thin films of ZnS and the identification of “FeAl₂O₄” clusters in activated ammonia catalysts (α-Fe+ 3%Al₂O₃).     

Density functional investigation of metal encapsulated X@C12Si8 heterofullerene (X=Li, Na, K, Be, Mg, Ca, Al, Ga)

The stability and the possible application of our recently reported SiC heterofullerenes inspire the investigation of their further stabilization through ion encapsulation. The endohedral complexes X@C₁₂Si₈, where X=Li⁺, Na⁺, K⁺, Be²⁺, Mg²⁺, Ca²⁺, Al³⁺, and Ga³⁺, are probed at the MPWB1K/6-311G? and B3LYP/6-311G* levels of theory. The optimized geometries show the expanding or contracting capability of C₁₂Si₈ in order to accommodate metal ion guests. The inclusion energies indicate the stability of the complexes compared to the components. Meanwhile, the calculated binding energies show the stabilization of C₁₂Si₈ through the inclusion of Be²⁺, Mg²⁺, Al³⁺, and Ga³⁺. The host-guest interaction that is probed through NBO atomic charges supports the obtained results. This study refers to “metal ion encapsulation” as a strategy for stabilization of SiC heterofullerenes.     

Luminescent Cu2+ Probes Based on Rare-Earth (Eu3+ and Tb3+) Emissive Transparent Cellulose Hydrogels

Cellulose hydrogels are biodegradable materials that can be applied as accommodating hosts for various species. Here we report the preparation of novel thin films based on luminescent cellulose hydrogels. The spectroscopic behavior of these soft materials and their sensing effects are investigated. Interestingly, we found that these films only give selective signal changes in the presence of Cu²⁺ in water in comparison with Na⁺, K⁺, Ag⁺, Mn²⁺, Co²⁺, Ca²⁺, Cd²⁺, Hg²⁺, Pd²⁺, Mg²⁺, Ni²⁺, Fe²⁺, and Fe³⁺. High visible-light transmittance and good flexibility for these films can be observed. More importantly, the thermal stability of rare-earth complexes could be significantly enhanced in aqueous solution as result of the protection by hydrogel matrix.     

Fluorescence Sensors for Selective Detection of Hg2+ Ion Using a Water-Soluble Poly(vinyl alcohol) Bearing Rhodamine B Moieties

The novel water-soluble poly(vinyl alcohol) with pendant rhodamine B moiety as colorimetric and fluorescene chemosensor for Hg²⁺ ions was prepared by grafting poly(vinyl alcohol) using rhodamine B hydrazide and hexamethylenediisocyanate as fluorescent dye and coupling agent, respectively. Because of their good water-solubility, the polymers binding rhodamine B can be used as chemosensors in aqueous media. With the addition of Hg²⁺ ions into the aqueous solution, visual color changes and fluorescence enhancements were detected. In addition, we also noticed that other metal ions such as Ag⁺, Cd²⁺, Co²⁺, Cu²⁺, K⁺, Mg²⁺, Ba²⁺, Fe²⁺, Ni²⁺, Pb²⁺, Cr³⁺, Fe³⁺ and Zn²⁺ cannot induce obvious changes to the fluorescence spectra of the polymer chemosensors. The combination of water solubility and positive fluorescence response as well as color change are hence particularly promising for the practical utility of the sensors.     

A New Fluorescent Chemosensor Detecting Co<Superscript>2+</Superscript> and K<Superscript>+</Superscript> in DMF Buffered Solution

A new fluorescent chemosensor 2-(2-thiophene)imidazo [4,5,f]-1,10-phenanthroline (L) was prepared and characterized. By adding univalent or divalent metal ions such as Na⁺, K⁺, Mg²⁺, Ba²⁺, Mn²⁺, Fe²⁺, Co²⁺, Ni²⁺, Cu²⁺, Ag⁺, Zn²⁺, Cd²⁺ and Hg²⁺ ions into the solution of L in DMF under buffered conditions with the working pH ranging from 7.0 to 8.0, we found that L could be used to detect K⁺ ratiometricly and it could also be applied to sense Co²⁺ with the phenomenon of fluorescence quenching of L. While the response behavior of L was not discernibly affected by other examined metal ions.     

Electron impact total ionization cross sections of beryllium and boron isoelectronic ions

A simple user-friendly empirical formula is proposed to calculate the electron impact total single ionization cross sections of beryllium-like Be, B⁺, C²⁺, N³⁺, O⁴⁺, Ne⁶⁺, Fe²²⁺, Hg⁷⁶⁺, and U⁸⁸⁺ and boron-like B, C⁺, N²⁺, O³⁺, Ne⁵⁺, Fe²¹⁺, Kr³¹⁺, and Xe⁴⁹⁺ targets. A simplified and modified version of the Bell formula is used in the present model incorporating the ionic correction factor. The predicted ionization cross sections are compared with the available experimental and theoretical results. Excellent agreements are found for the incident energies ranging from threshold to 10⁶ eV considered herein. The presented results achieve a level of agreement that is better than the calculations from the existing theoretical methods and empirical models. Hence, this model may be an excellent choice, due to its simplicity, for the practitioners in the fields of applied sciences and technologies.     

How water and counterions diffuse into the hydrated montmorillonite

Molecular dynamics simulations have been performed to study the diffusive transport properties of water and counterions in 1-, 2- and 3-layer hydrated Wyoming-type montmorillonite (MMT). The considered counterions included in the clay are monovalent cations, such as Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺, and divalent cations, such as Ca²⁺, Ni²⁺, Zn²⁺ and Pb²⁺. The diffusion simulation results of Li-, Na-, K-, Cs-MMT, based on NVE ensemble and SPC/E water model, compared well to available experimental quantities and previous simulations, which permit us to study the diffusion behaviour of heavy metal counterion including in the different hydrated montmorillonite. Our simulation results show that the diffusion coefficients of both water molecule and counterions increase versus the quantity of water content. At the same hydrated state, the diffusion of cations strongly depends on their size, weight and capacity of attracting water. Monovalent cations diffuse always much faster than divalent ones. Although the increasing of hydrate degree can raise the diffusion coefficient of divalent heavy cations, the activity of these heavy counterions is still very weak. The diffusion of cations in the interlayer space of clay is much weaker than that in bulk water. That means the presence of charged clay has great influence on the diffusion of cations, which change totally the diffusion behaviour of cations.     

High resolution laser spectroscopy of metallic atoms and molecules: Storage of singly and doubly charged ions transferred from externally generated laser plasmas

A radio-frequency (RF) ion trap has been constructed for high resolution laser spectroscopy of metallic ions. Ions in externally generated laser plasma have been directly introduced into the RF ion trap. An Nd:YAG laser is used to vaporize and ionize sample metals placed behind a ring electrode. Both hyperbolic and cylindrical electrodes are successfully used for confinement of the ions. Trapped ions are detected either with a quadrupole mass spectrometer or with a photomultiplier for the measurement of laser-induced fluorescence. Metallic ions such as Ca⁺, Ba⁺, La⁺, Nd⁺, Tm⁺, Lu⁺, and Ta⁺ have been confined for the time range of several to 20 minutes in the presence of He buffer gas, and a doubly charged ion Ba²⁺ for several seconds. Some ions like Nd⁺, Lu⁺, Hf⁺, and Ta⁺ are found to be highly reactive with background gaseous molecules.     

N2微空心阴极放电特性及其阴极溅射的PIC/MC模拟

采用两维PIC/MCC模型模拟了氮气微空心阴极放电以及轰击离子 (N₂⁺,N⁺) 的钛阴极溅射. 主要计算了氮气微空心阴极放电离子 (N₂⁺,N⁺) 及溅射原子Ti的行为分布, 并研究了溅射Ti 原子的热化过程. 结果表明: 在模拟条件下, 空心阴极效应是负辉区叠加的电子震荡; 在对应条件下, 微空心较传统空心放电两种离子 (N₂⁺,N⁺) 密度均大两个量级, 两种离子的平均能量的分布及大小几乎相同; 在放电空间N⁺的密度约为N₂⁺的1/6, 最大能量约大2倍; 在不同参数 (P, T, V)下, 轰击阴极内表面的氮离子(N₂⁺,N⁺)的密度近似均匀, 其平均能量几乎相等; 从阴极溅射出的Ti原子的初始平均能量约6.8 eV, 离开阴极约0.15 mm处几乎完全被热化. 模拟结果为N₂微空心阴极放电等离子体特性的认识提供了参考依据. 关键词： 微空心阴极放电 PIC/MC模拟 2等离子体')" href="#">N₂等离子体     

MeV重离子在固体靶中的平均投影射程计算

根据Biersack角扩散模型,建立了计算MeV重离子在固体靶中的平均投影射程的方法。与新近发表的1.0MeV的In⁺,Xe⁺,Ta⁺和1.0—2.0MeV的Pb⁺在Si中的平均投影射程实验数据相比,本文计算值与实验值的最大偏离为8％,而Monte-Carlo(TRIM′86)和PRAL的计算值与实验值的最大偏离分别为23％和22％。这表明本文的计算在预言1.0—2.0MeV的重离子(In⁺,Xe 关键词：     

Optical absorption of s2-configuration ions in alkali halide crystals—III: The A band in Sn2+-doped crystals

The line shape of the A band in KCl:Sn²⁺, KBr:Sn²⁺, KI:Sn²⁺, RbCl:Sn²⁺ and RbBr:Sn²⁺ has been measured as a function of temperature between about 15 K and room temperature. As the spectra for all these systems are similar detailed results are presented only for RbCl: Sn²⁺, RbBr:Sn²⁺ and KBr: Sn²⁺. The experimental data resemble those of a previous study on KBr:In⁺ and KG:In⁺ in that the A band consists of two broad, overlapping components designated A₁ (the low energy component) and A₂. The separation between A₁ and A₂ is more marked at low temperature for Sn²⁺ than for In⁺, and no inversion of the ratio of the peak heights of A₁ and A₂ occurs as the temperature is varied, as was so for In⁺. Detailed calculations of the line shape are presented for KBr:Sn²⁺. These calculations show that one cannot account for the line shape purely in terms of the dynamical Jahn-Teller effect and that there is in addition a static splitting of the A state caused by a lowering in the symmetry of the crystal field.     

Boron-, nitrogen-, aluminum-, and phosphorus-doped graphite electrodes for non-lithium ion batteries

Intercalation of Li⁺, Na⁺, K⁺, Mg²⁺, Ca²⁺, Zn²⁺, and Al³⁺ ions into B-, N-, Al-, and P-doped graphite has been studied using density functional theory calculations. While the intercalation of Li⁺, K⁺, and Ca²⁺ ions into graphite is thermodynamically favorable, that of Na⁺, Mg²⁺, Zn²⁺, and Al³⁺ ions into graphite is unfavorable. When doped in the form of graphitic structure, B, Al, and P dopants significantly stabilize the ion-intercalated graphite compounds. As a result, Na⁺ ions that are unable to intercalate into graphite can intercalate into B-, Al-, and P-doped graphite. The electron transfer from B, Al, and P dopants to host C atoms reinforces the ion–graphene electrostatic interaction, enhancing the thermodynamic driving force for ion intercalation. The catalytic activity of the dopant to promote the ion intercalation increases in the order of N < B < P < Al, which is associated with the electronegativity of the dopant.     

8-Hydroxyquinoline Functionalized Graphene Oxide: an Efficient Fluorescent Nanosensor for Zn<Superscript>2+</Superscript> in Aqueous Media

A nanosensor, based on 8-hydroxyquinoline functionalized graphene oxide, was developed for the fluorescence detection of Zn²⁺. It showed high selectivity and sensitivity for Zn²⁺ion in aqueous solution over other metal ions such as Li⁺, Na⁺, Ca²⁺, Mg²⁺, Al³⁺, Cd²⁺, Co²⁺, Cu²⁺, Hg²⁺, Ni²⁺, Pb²⁺, Fe²⁺, Fe³⁺and Cr³⁺. Due to the linearity of the emission intensity toward Zn²⁺ concentration, fluorescent technique could be used for the detection of Zn²⁺ ion even at very low concentrations.     

Rhodamine B-based “turn-on” fluorescent and colorimetric chemosensors for highly sensitive and selective detection of mercury (II) ions

Two novel macromolecules based on 2-[3-(2-aminoethylsulfanyl)propylsulfanyl]ethanamine covalently bound to one and two units of rhodamine-B moieties, 1 and 2, were prepared and utilized as fluoroionophores and chromophores for the optical detection of Hg²⁺ ions. The sensors were readily prepared by a conventional two-step synthesis. Especially, sensor 1 exhibits high sensitivity and selective OFF–ON fluorescence enhancement and chromogenic change upon binding to Hg²⁺, which served as a “naked-eye” indicator by a noticeable color change of the solution (from colorless to pink–red color). 1 is shown to discriminate various competing metal ions, particularly Ag⁺ and Cu²⁺, as well as Cd²⁺, Na⁺, Li⁺, K⁺, Ba²⁺, Co²⁺, Ni²⁺, Mg²⁺, Mn²⁺ and Al³⁺, with a detection limit of 10 ppb.     

Luminescence enhancement of ZnGa2O4:Mn by Ge and Li doping

Structural and optical properties of ZnGa₂O₄:Ge⁴⁺ and ZnGa₂O₄:Ge⁴⁺, Li⁺, Mn²⁺ phosphors were investigated by using X-ray diffraction (XRD), photoluminescence (PL) and cathodoluminescence (CL) measurements. The XRD patterns show that Ge-doped ZnGa₂O₄ has a spinel phase and its lattice constant increases with respect to ZnGa₂O₄. Emission wavelength shifts from 400 to 360 nm in comparison with ZnGa₂O₄ when Ge is doped in ZnGa₂O₄ and a peak related with oxygen defect was observed in Ge-doped ZnGa₂O₄. The CL luminance of ZnGa₂O₄:Ge⁴⁺, Li⁺, Mn²⁺ phosphors is seven times brighter than that of ZnGa₂O₄:Mn²⁺. This drastic luminance improvement can be attributed to Ge doping in ZnGa₂O₄ acting as donor ion and Li doping resulting in increasing conductivity of ZnGa₂O₄. These results indicate that ZnGa₂O₄:Ge⁴⁺, Li⁺, Mn²⁺ phosphors hold promise for potential applications in field-emission display devices with high brightness operating in green spectral regions.     

A many-body calculation of the hyperfine interaction in the lowest2 S and2 P states of li-like systems

A non-relativistic perturbation method of Brueckner-Goldstone type is used to calculate the hyperfine interactions in the lowest² S and² P states of the Li-like systems, Li, Be⁺, B²⁺, C³⁺, N⁴⁺, O⁵⁺ and F⁶⁺. The effect of the polarization of the closed shell is treated to all orders of perturbation, while the correlation effect is calculated in the lowest order, i.e. in the third order of the perturbation expansion. Experimental data are at present available only for Li, Be⁺ and F⁶⁺, and the agreement with the calculated values is in these cases very good, usually within the experimental uncertainties. This implies that the predictions made in the remaining cases should be quite reliable, which may simplify the experimental determination of these quantities. Theoretical values are also given for the quadrupole interaction, which can be used to determine the nuclear quadrupole moments, when accurate experimental information becomes available.     

A many-body calculation of the hyperfine interaction in the lowest2S and2P states of li-like systems

A non-relativistic perturbation method of Brueckner-Goldstone type is used to calculate the hyperfine interactions in the lowest² S and² P states of the Li-like systems, Li, Be⁺, B²⁺, C³⁺, N⁴⁺, O⁵⁺ and F⁶⁺. The effect of the polarization of the closed shell is treated to all orders of perturbation, while the correlation effect is calculated in the lowest order, i.e. in the third order of the perturbation expansion. Experimental data are at present available only for Li, Be⁺ and F⁶⁺, and the agreement with the calculated values is in these cases very good, usually within the experimental uncertainties. This implies that the predictions made in the remaining cases should be quite reliable, which may simplify the experimental determination of these quantities. Theoretical values are also given for the quadrupole interaction, which can be used to determine the nuclear quadrupole moments, when accurate experimental information becomes available.