Transient magnetic fields in silicon ions traversing thin foils of Fe and Gd at high velocity

Spin precessions of the²⁸Si first 2⁺ state, caused by transient magnetic fields in thin Fe and Gd foils, were measured at a mean ion velocity of 7.5v ₀ (v ₀=c/137). Transient fields of 1.8 (3) kT and 1.1 (2) kT have been deduced for Fe and Gd, respectively. The observed field strengths are discussed in terms of the electron mean polarization in the SiK shell.     

Time-resolved determination of Fe(II) ions using cysteine-bridged Mn-doped ZnS quantum dots as a phosphorimetric probe

A time-resolved phosphorescence (TRP) is applied to the highly sensitive determination of Fe(II) ions. The method is based on the use of a phosphorescent probe consisting of cysteine-bridged Mn-doped ZnS quantum dots (Mn/ZnS QDs). The presence of cysteine enhances the phosphorescence of the QDs and also increases the efficiency of quenching caused by Fe(II) ions. This results in strongly improved selectivity for Fe(II). The linear response is obtained in the concentration range of 50–1000 nM with a 19 nM detection limit. Phosphorescence is recorded at excitation/emission peaks of 301/602 nm. The interference of short-lived fluorescent and scattering background from the biological fluids is eliminated by using the TRP mode with a delay time of 200 μs. The determination of Fe(II) in human serum samples spiked at a 150 nM level gave a 92.4% recovery when using the TRP mode, but only 52.4% when using steady-state phosphorescence. This demonstrates that this probe along with TRP detection enables highly sensitive and accurate determination of Fe(II) in serum.

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Graphical abstract Schematic of a novel phosphorescent method for the detection of Fe²⁺ ions based on cysteine-bridged Mn-doped ZnS quantum dots. The sensitivity of this assay greatly increases due to the addition of cysteine. Interferences by short-lived auto-fluorescence and the scattering light from the biological fluids is eliminated by using time-resolved phosphorescence mode.

     

Detection of mercury and phenylmercury ions using DNA-based fluorescent probe

A DNA probe labeled with a 4-([4-(dimethylamino)phenyl]azo)benzoic acid (DABCYL) quencher and a carboxyfluorescein (FAM) donor at its 5'- and 3'-termini can be used for the detection of Hg(2+) ions and phenylmercury ions (PhHg(+)). This DNA probe possesses a random coil structure that changes into a hairpin-like structure upon binding Hg(2+) and PhHg(+) ions. As a result, the fluorescence of the FAM unit decreased through quenching between the donor and the quencher. In the presence of ethylenediaminetetraacetic acid (EDTA), the DNA probe allowed the selective detection of PhHg(+) ions at concentrations as low as 70.0 nM, mainly as a result of T-Hg(2+)-T coordination and π-π stacking between the Ph unit and DNA bases. A linear correlation existed between the fluorescence intensity and the concentration of PhHg(+) ions over the range from 0.10 to 1.0 μM (R(2) = 0.99). After acid hydrolysis and neutralization of the samples, all of the mercury species are converted to Hg(2+) ions, allowing us to use the DNA-based probe to determine the concentrations of total mercury species at the nM level. The practicality of this probe has been validated by the analyses of pond water and fish samples, showing its advantages of sensitivity, selectivity, and simplicity.     

Thiacalix[4]arene based fluorescent probe for sensing and imaging of Fe3+ ions

A thiacalix[4]arene based fluorescent chemosensor 3 in the cone conformation has been synthesized and its recognition behaviour is evaluated toward various metal ions in mixed aqueous media. The chemosensor 3 showed high selectivity towards Fe(3+) ions by fluorescence quenching of excimer emission. Further, evaluation of the 3·Fe(3+) complex prepared in situ demonstrated great promise for the detection of the Fe(3+) ion in the presence of amino acids, blood serum and bovine serum albumin (BSA) solution. The compound 3 has suitable permeability into the PC3 cells and can be utilized as a Fe(3+) selective sensor in living cells (PC3 cells).     

Regulating the size and stabilization of lipid raft-like domains and using calcium ions as their probe

We apply a means to probe, stabilize, and control the size of lipid raft-like domains in vitro. In biomembranes the size of lipid rafts is ca. 10-30 nm. In vitro, mixing saturated and unsaturated lipids results in microdomains, which are unstable and coalesce. This inconsistency is puzzling. It has been hypothesized that biological line-active surfactants reduce the line tension between saturated and unsaturated lipids and stabilize small domains in vivo. Using solution X-ray scattering, we studied the structure of binary and ternary lipid mixtures in the presence of calcium ions. Three lipids were used: saturated, unsaturated, and a hybrid (1-saturated-2-unsaturated) lipid that is predominant in the phospholipids of cellular membranes. Only membranes composed of the saturated lipid can adsorb calcium ions, become charged, and therefore considerably swell. The selective calcium affinity was used to show that binary mixtures, containing the saturated lipid, phase separated into large-scale domains. Our data suggests that by introducing the hybrid lipid to a mixture of the saturated and unsaturated lipids, the size of the domains decreased with the concentration of the hybrid lipid, until the three lipids could completely mix. We attribute this behavior to the tendency of the hybrid lipid to act as a line-active cosurfactant that can easily reside at the interface between the saturated and the unsaturated lipids and reduce the line tension between them. These findings are consistent with a recent theory and provide insight into the self-organization of lipid rafts, their stabilization, and size regulation in biomembranes.     

Monte Carlo simulation of Cu,Ni and Fe grade determination in borehole by PGNAA technique

A prompt gamma neutron activation analysis borehole logging method for copper, nickel and iron grade estimation is proposed. The performance of the method was simulated by MCNP5 code. Based on the theory of neutron–gamma distribution on the borehole condition, the BGO scintillator and ³He neutron tube are adopted to record gamma ray spectrum and thermal neutron simultaneously, and least square method is used for the characteristic gamma ray counts calculation in the high energy range. The results of detection limit of metal grade in borehole condition indicate that the effectiveness of this logging method.     

Homogeneous electro-mediated reduction of unsaturated compounds using Ni and Fe as mediators in DMF

The homogeneous electro-mediated reduction (HEMR) of several organic compounds (cyclohexene, cyclohexanone, acetophenone, benzaldehyde, styrene, linalool, 1,3-cyclohexadiene, citral, trans-4-phenyl-3-buten-2-one, and piperine) was carried out using Fe²⁺, Ni²⁺, and [Ni^II(bpy)]Br₂ (bpy=2,2′-bipyridine) as electron mediators. An electrochemical system composed of sacrificial anode (Fe, Ni or Zn), nickel cathode, NaI (0.2 M) as supporting electrolyte in DMF and an undivided cell, was used. A constant current ≤100 mA was applied with a maximum cell potential of 2.0 V. Non-conjugated olefins are not reactive, but ketones may be easily reduced to the respective alcohol. In the case of conjugated olefins and ketones, [Ni^II(bpy)]Br₂ or Ni²⁺ mediator presented good reactivity and selectivity in most cases. Fe²⁺ more efficiently mediates the reduction of carbonyl containing systems. Preliminary electroanalytical studies indicate the complexation of the organic substrate by Fe²⁺ and Ni²⁺ ions and [Ni^II(bpy)]Br₂ complex.     

Selective colorimetric assay of cyanide ions using a thioamide-based probe containing phenol and pyridyl groups

The selective assay of cyanide ions with a thioamide compound (HNPTU) containing phenol and pyridine as a chemosensor is reported using absorbance changes in a buffered aqueous solution (50 mM HEPES, pH 7.4) containing ethanol. Upon treatment with cyanide ions, the colorless solution of HNPTU turned yellow. No significant changes were observed with other comparable anions, such as F⁻, Cl⁻, Br⁻, I⁻, and CH₃COO⁻. The color change of HNPTU upon treatment with CN⁻ was maintained even in the presence of the comparable monovalent anions. The complex stability constant (K_a = 2.6 × 10³) for the stoichiometric 1:1 complexation of HNPTU with cyanide ions was obtained based on absorbance titrations. The interaction of HNPTU with cyanide ions was proposed to be deprotonation, as shown by NMR and Cu(II) treatment experiments.     

荧光分析中铁镍锌对铜Kα射线强度的影响

能量色散X荧光分析(EDXRF)过程中,存在吸收增强效应影响分析准确性的问题。利用EDXRF测量Fe、Ni、Zn三种元素与Cu的六组伪二元系样品,根据实验结果对元素间的影响特征和影响程度进行了分析。并利用La-chance-Trail算法得到三组元素间的影响因子数值,Cu和Fe以及Cu和Zn之间的影响效应随元素含量变化较明显,分别在0.38～0.70和0.43～0.65之间,Cu和Ni之间的影响效应不明显。对Cu-Zn二元系中Cu含量实际计算结果相对误差均在5%以内。     

Measurement of sugars using the laser spray technique with a gold capillary

A gold (Au) capillary has higher thermal conductivity than a stainless steel capillary and can withstand capillary over-heating induced by high CO(2) laser irradiation (over 2.5 W) better than a stainless steel capillary. For this study, a laser spray using an Au capillary was applied for the detection of sugars. The signal of cationized compounds [M+Na](+) can be detected with higher sensitivity than with conventional laser sprays using high laser power (over 2.7 W). Using 3.5 W of laser power, the signal intensity is 15 times higher than the maximum value with stainless steel (2.3 W) in a 10(-5) M maltose aqueous solution. It is considered that almost all the water molecules evaporate by laser irradiation, which is impossible to achieve using a stainless steel capillary.     

Isolation and quantification of Fe and Ni in reactor effluents using extraction chromatography and liquid scintillation analysis

A novel extraction chromatographic resin based on diisobutyl ketone has been developed for the isolation of ⁵⁵Fe. This material has been used in conjunction with a dimethylglyoxime-based resin for the sequential separation of ⁵⁵Fe and ⁶³Ni and isolation of these radionuclides from associated contaminants. The preparation and characterisation of these resins is described along with an assessment of their performance for the isolation of ⁵⁵Fe and ⁶³Ni from a mixture of nuclear activation products. In addition, a refined approach for the measurement of these nuclides by liquid scintillation counting is discussed. The findings of these studies have been combined to develop a robust procedure for the analysis of ⁵⁵Fe and ⁶³Ni in reactor effluents which is now the preferred method for a number of UK analytical laboratories.     

IR-spectroscopic characterization of acetophenone complexes with Fe+, Co+, and Ni+ using free-electron-laser IRMPD

The gas-phase complexes M(+)(acet)(2), where M is Fe, Co, or Ni and acet is acetophenone, were studied spectroscopically by infrared multiple-photon dissociation (IRMPD) supported by density functional (DFT) computations. The FELIX free electron laser was used to give tunable radiation from approximately 500 to 2200 cm(-1). The spectra were interpreted to determine the metal-ion binding sites on the ligands (oxygen (O) or ring (R)) and to see if rearrangement of the ligand(s) to toluene plus CO occurred. For Ni(+), O binding was found to predominate (similar to the previously studied Cr(+) case), with less than approximately 10% of R-bound ligands in the population. For Co(+), a roughly equal mixture of R-bound and O-bound ligands was present; based on the computed thermochemistry, the OR complex was considered likely to predominate. Fe(+) complexes appeared largely O-bound, but with clear evidence for some R-binding. The exceptionally large extent of R binding for Co(+) highlights the special affinity of this metal ion for aromatic ring ligands. In contrast, the predominant O binding for Ni(+) emphasizes the especially high metal-ion affinity of the O site of acetophenone compared with other ligands such as anisole where R binding of Ni(+) predominates. The spectra did not indicate significant intracomplex rearrangement of ligands to toluene plus CO, and in particular for the Co(+) case the absence of a metal-bound C triple bond O stretching peak near 2100 cm(-1) strongly ruled out such a rearrangement.     

Direct determination of metals associated with airborne particulates using a graphite probe collection technique and graphite probe atomic absorption spectrometric analysis

A new analytical method has been developed for direct analysis of solid samples of airborne particulate matter by a graphite probe collection technique coupled with graphite furnace atomic absorption spectrometry. A porous graphite probe is used as a filter for air particles. The probe is then subjected to atomization by being inserted into a graphite furnace which has been pre-heated to a constant atomization temperature. Some aspects of the method have been tested by recovery studies using NBS Urban Particulate Matter, SR M No. 1648, and found to give recoveries of 91–107% for Pb, Cd, Ni, Cu and Mn. By combining a highly efficient filtering medium with the extremely high relative sensitivity of solid sampling, this method has the potential of monitoring sources of air particulate emission with sufficient temporal and spatial resolution for unequivocal identification of the pollution source (at least on a local scale).     

A novel nanoaggregation detection technique of TNT using selective and ultrasensitive nanocurcumin as a probe

Here, for the first time, we designed an ultrasensitive nanocurcumin based nanomaterials surface energy transfer (NSET) probe for detection of trace amount of TNT with excellent sensitivity (1 nM) and selectivity over other nitro explosives via nanoaggregation and we found the largest fluorescent enhancement to date for sensing TNT (upto 800 fold).     

Measurement of the neutron capture cross-section of 238U using the neutron activation technique

The ²³⁸U(n, ??)²³⁹U reaction cross-section at average neutron energy of 3.7?±?0.3?MeV from the ⁷Li(p, n)⁷Be reaction has been determined using activation and off-line ??-ray spectrometric technique. The ²³⁸U(n, ??)²³⁹U and ²³⁸U(n, 2n)²³⁷U reaction cross-sections at average neutron energy of 9.85?±?0.38?MeV from the same ⁷Li(p, n)⁷Be reaction have been also determined using the above technique. The experimentally determined ²³⁸U(n, ??)²³⁹U and ²³⁸U(n, 2n)²³⁷U reaction cross-sections were compared with the evaluated data of ENDF/B-VII, JENDL-4.0, JEFF-3.1 and CENDL-3.1. The experimental values were found to be in general agreement with the evaluated value based on ENDF/B-VII, and JENDL-4.0 but not with the JEFF-3.1 and CENDL-3.1. The present data along with literature data in a wide range of neutron energies were interpreted in terms of competition between different reaction channels including fission. The ²³⁸U(n, ??)²³⁹U and ²³⁸U(n, 2n)²³⁷U reaction cross-sections were also calculated theoretically using the TALYS 1.2 computer code and were also found to be in agreement experimental data.     

Intercombination lines of Mg I-, Al I- and Si I-like ions in the beam foil spectra of Ti,Fe, Ni and Cu

In delayed spectra of foil-excited beams of Ti, Fe, Ni and Cu ions lines have been observed which are identified with intercombination transitions 3s ^{2 1} S ₀ — 3s 3p ³ P ₁ ⁰ , 3s ² 3p ² P ⁰ — 3s 3p ^{2 4} P and 3s ² 3p ^{2 3} P — 3s 3p ^{3 5} S ₂ ⁰ in magnesiumlike, aluminiumlike and siliconlike spectra, resp. Wavelengths and decay properties have been determined. The results are compared to recent theoretical predictions.     

TDCR measurements of 3H, 63Ni and 55Fe using Hidex 300SL LSC device

The commercial Hidex LSC system has been used to measure triple to double coincidence ratio (TDCR), experimental counting efficiency (CE) and the absolute activity for radioactive standards of pure beta emitters viz. ³H, ⁶³Ni and ⁵⁵Fe, an electron capture nuclide. Colour and chemical quench measurements of ⁶³Ni and ⁵⁵Fe have been done. An excellent match between TDCR and CE has been obtained for beta emitters, while very large deviations have been observed for ⁵⁵Fe. The deviation between TDCR and experimental efficiency has been found to be nearly uniform. Based on this, an empirical correction factor for TDCR which gives the correct efficiency has been evaluated, to enable efficient application of this commercial instrument for ⁵⁵Fe estimation. These TDCR correction factors were further validated by applying for ⁵⁵Fe activity measurements in ASTM standard steel samples irradiated to a fixed neutron flux in research reactor CIRUS. Finally, ⁵⁵Fe activity in steel sample from APSARA reactor decommissioning waste was successfully estimated using this modified TDCR.     

Calculated electron impact cross sections for the K-shell ionization of Fe,Co, Mn,Ti, Zn,Nb, and Mo atoms using the DM formalism

We used the Deutsch-Märk (DM) formalism to calculate atomic K-shell electron impact ionization cross sections for the elements Fe, Co, Mn, Ti, Zn, Nb, and Mo. The calculated K-shell ionization cross sections are compared with recently measured K-shell ionization cross sections. Good to satisfactory agreement was found for all atoms with the exception of Ti. Moreover, when compared to other available K-shell ionization cross sections for these atoms, calculated using other theoretical methods and semiempirical formulae, the predictions of the DM formalism achieve a level of agreement with experimental data that is as good or better than the predictions from the other methods.