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[en] In the compacted bentonite containing Ag2O, the transport of iodide ion was investigated by Through-diffusion method. It is confirmed that Iodide ion is transported by diffusion process in the compacted bentonite containing Ag2O as well as in the compacted bentonite without Ag2O. However, the lag-time of iodide ion in the compacted bentonite containing Ag2O is larger than that in the compacted bentonite without Ag2O. The increase of the lag-time was observed in pure iodide ion solution and also in 0.1M NaCl-iodide ion solution. The apparent diffusion coefficient of iodide ion in the compacted bentonite containing Ag2O has lower value than that in the compacted bentonite without Ag2O. The effect of Ag2O on the effective diffusion coefficient was not clearly investigated in the compacted bentonite containing Ag2O while the values of effective diffusion coefficient of iodide ion in the compacted bentonite without Ag2O obtained in this study were similar to those in the compacted bentonite reported in the literature
[en] Colorimetric solid-phase extraction (C-SPE) has been previously explored as a means to monitor the iodine-based disinfectant used in the water systems on board the space shuttle. This same disinfectant is baselined for eventual deployment in the US water recovery system planned for node 3 of the International Space Station (ISS). With C-SPE, the I2 concentration is determined from the diffuse reflectance spectrum (DRS) of the yellow iodine-poly(vinylpyrrolidone) (PVP) complex using the Kubelka-Munk function. However, the solution chemistry of iodine is very complex and results in a variety of inorganic species (e.g., I-, I2, I3-, HOI) that have very different biocidal capabilities. Thus, the nature of the interaction of iodine with PVP, and more specifically, the identity of the iodine species involved in the interaction, requires more elucidation. This paper reports the findings from a series of detailed experiments conducted to elicit a more complete understanding of the iodine-PVP system employed in C-SPE. The results indicate that I2, one of the two dominant biocidal forms of iodine, is the species responsible for the analytical signal in our C-SPE platform. These findings lay the ground work for the planned development of a multiplexed iodine determination and speciation platform for in-flight analysis of spacecraft water samples
[en] A prototype system was developed to investigate an isotope-selective laser photodetachment technique for a 129I accelerator mass spectrometer. A pulsed ion source for negative iodine ions (I−) that employed laser ablation proved to be suitable for isotope-selective laser photodetachment. Laser photodetachment of pulsed negative iodine ions was estimated to have an efficiency of about 81% based on a model calculation for the prototype system with a tunable pulsed Ti:sapphire laser. -- Highlights: •We investigated 129I-AMS assisted by isotope selective laser photo-detachment. •We developed proto-type apparatus for laser photo-detachment. •Developed pulsed negative ion source seems to be suitable for proposal method. •The efficiency of laser photo-detachment was estimated
[en] As a part of evaluating the volatility of iodide ions subjected to gamma irradiation, I2 evaporation experiments were performed with I2 and I– mixed solutions in the temperature range 26–80°C in an open, well-ventilated space. The evaporation of I2 was observed to follow primarily first order kinetics, depending on the I2 concentration. The evaporation rate constant increased rapidly with increase in temperature. The presence of I– slightly reduced the evaporation rate of I2 by forming relatively stable I3−. The effect of Cl– at <1.0 wt% on I2 evaporation was insignificant. The evaporation rate constants of I2 were 1.3 × 10−3 min−1 cm−2, 2.4 × 10−2 min−1 cm−2, and 8.6 × 10−2 min−1 cm−2, at 26°C, 50°C, and 80°C, respectively
[en] As the impact of aromatic rings and fluorine substituents in commercial drugs is attributed to their electronic distribution and structure rigidity that determine metabolic stability and toxicity, 30 quaternary ammonium salts (QAS) of the form [X-CH2N(CH3)2(CH2)nCH = C(Ar2)]+I− (where X=H, Cl or I, n = 2 or 3, and Ar = m-C6H4CF3, p-C6H4CF3, m-C6H4F, p-C6H4F or C6H5) were tested as potential trypanocidal agents and assessed their cytotoxicity on U-937 cells. CF3-substituted QASs exhibited LC50 values in the range of 0.5 to 6.4 μg/mL and trypanocidal EC50 values between 0.6 and 7.0 μg/mL, while the LC50 values for F-substituted analogs are between 7.0 and 207 μg/mL and EC50 values range from 3.8 to 40.9 μg/mL. As a general trend, the more effective are those bearing an N-iodomethyl moiety or having a longer tether, and para-substituted ones. Few drugs therapies are in use for Chagas disease, so this study becomes a promising contribution.
[en] An alkyl-thiophene functionalized D-π-A porphyrin (LW16) is designed and synthesized for dye-sensitized solar cells (DSSCs). Two hexyl-thiophene groups are attached to the meta-position of each meso-phenyl with a motivation to increase the light-harvesting ability as well as retarding the aggregation of porphyrins dyes. For comparison, none-alkyl substituted (LW14) and octyloxy substituted (LW15) porphyrin dyes are also synthesized to fully investigate the influence of porphyrin chromophore modification. These porphyrins present similar spectrum while the oxidation potentials vary as the functionalized group changes from the meta-position to ortho-position. The DSSCs based on the alkyl-thiophene functionalized (LW16), none-alkyl substituted (LW14), and octyloxy substituted (LW15) porphyrins can be achieved a power conversion efficiency of 8.5%, 6.9%, and 8.2% using I"–/I_3"–redox electrolyte under full sunlight irradiation (AM 1.5 G, 100 mW cm"−"2), respectively. It is found that by tailoring the porphyrin chromophore with hexyl-thiophenes, the photocurrent of the corresponding devices could be increased without sacrifice the photovoltage. Detailed investigation, including spectroscopy, electrochemical and transient photovoltage decay measurement, provides general influence of π-conjugation extension at the meso-position onto the optoelectronic features of porphyrins dyes.
[en] A new method has been developed for the investigation of endoergic ion--molecule-collision processes of negative ions. This method is, in effect, an extension of an earlier one developed by Refaey and Chupka used in connection with positive ions. An ion source with separate ionization and collision chambers was constructed and mounted on a Bendix time-of-flight mass spectrometer. I- ions produced in the ionization chamber by electron resonance capture of HI are pulsed to the desired energy where they enter a collision chamber containing a different gas. Cross sections for various endoergic ion--molecule-collision processes are measured as a function of the incident ion (I-) energy. Collision of I- on SO2 gives the secondary ions SO2-, IO-, O-, SO-, and S- and/or O2- in the energy range 2--25 eV (cm). Experimental thresholds were used to determine heats of formation as well as the electron affinities of various species. The electron affinities of SO2, IO, SO, and S were determined as 1.05, 2.3, 1.2, and 2.0 eV. The onset for the formation of O- indicates that it is accompanied by the neutral ISO. This onset leads to ΔH/sub f/(ISO) =-16 kcal mole/sup -1/. IS has been suspected as a product in two separate cases. A fairly good estimate of ΔH/sub f/(IS) can be set as 74 kcal mole/sup -1/
[en] A high brightness contact ionization source of negative iodine ions has been developed for use in an ion beam microprobe mass analyzer. The contact ionization process was selected instead of the conventional electron attachment technique because of the small ion energy spread, the low gas load, and the high efficiency of the contact source. The source is a planar LaB6 cathode which is mounted in a modified Pierce ion optics geometry. A molecular beam of iodine vapor is directed toward the cathode surface. The negative ions and electrons emitted from the surface are accelerated and focused into a narrow beam. A transverse electromagnetic field is used to separate the ion and electron fractions. Ion current densities of 5 to 10 mA/cm2 were generated at cathode temperatures of 1650 to 17750K. The electron-to-ion ratios were on the order of 100 to 300. Ionization efficiencies of 5 to 45 percent were observed in this temperature range. The ion source was operated at a brightness level estimated to be 100 A/ cm2-sr at 10 kV