Formation Of AgI Research Articles

Structural Aspects and Ion Transport Properties of a New Mixed System BiI3 - Ag2WO4

An experimental attempt was made to analyze structural and ion transport properties in the case of a new mixed system viz ., (BiI 3)y - (Ag 2WO 4)100-y where y = 10, 20, 30, 40, 50, 60, 70, 80 and 90 mol% respectively. The samples synthesized by the rapid melt-quenching technique were analyzed using Fourier Transform Infrared (FT-IR) spectroscopy, differential scanning calorimetric (DSC) analysis and silver ionic transport number studies. The results of FT-IR and DSC studies have revealed the formation of AgI and other phases in various compositions of the system. The transport number measurements carried out by Wagner's and EMF methods have indicated that silver ions may be responsible for the observed ionic transport in these newly formed solid electrolyte phases.

SU‐E‐T‐270: Comparison of Different Methods of Iodine‐125 Fixation On Silver Substrate for a Brachytherapy Seed

Purpose: Brachytherapy treatment is a form of treatment in which source is in contact or placed within the patient. The iodine125 brachytherapy seeds can be used to treat prostate, brain and ophthalmic cancers. Most of the population has no access to this treatment because of its high cost ($ 60.00 each seed, 80 to 120 used for only one patient). For this reason, IPEN (Institute of Energy and Nuclear Research) develops new a seed.Methodology: Four different methods were compared: Method 1 and Method 2: Chemical deposition and eletrodeposition described in U.S. Pat. n. 4,323,055; Method 3: IPEN's new method presented in Development and production of radioactive sources used for cancer treatment in Brazil. Nukleonika, 2008; Method 4: New method developed in IPEN using oxidant agent that enforce the AgI formation. Results: Method 1: fixation efficiency 65.16%; process cost R $ 7.04Method 2: fixation efficiency 70.80%; process cost R $ 6.58 Method 3: fixation efficiency 55.80%; process cost R $ 8.24Method 4: fixation efficiency 90.11%; process Cost $ 5.00ConclusionThe fourth method achieved the efficiency, 90.11% and lowest cost $2,5. The results show that this is the best method to be implemented in IPENs new laboratory.

On the validity and phylogenetic position of Eubrachiosaurus browni, a kannemeyeriiform dicynodont (Anomodontia) from Triassic North America.

The large dicynodont Eubrachiosaurus browni from the Upper Triassic Popo Agie Formation of Wyoming is redescribed. Eubrachiosaurus is a valid taxon that differs from Placerias hesternus, with which it was previously synonymized, by greater anteroposterior expansion of the scapula dorsally and a very large, nearly rectangular humeral ectepicondyle with a broad supinator process. Inclusion of Eubrachiosaurus in a revised phylogenetic analysis of anomodont therapsids indicates that it is a stahleckeriid closely related to the South American genera Ischigualastia and Jachaleria. The recognition of Eubrachiosaurus as a distinct lineage of North American dicynodonts, combined with other recent discoveries in the eastern USA and Europe, alters our perception of Late Triassic dicynodont diversity in the northern hemisphere. Rather than being isolated relicts in previously therapsid-dominated regions, Late Triassic stahleckeriid dicynodonts were continuing to disperse and diversify, even in areas like western North America that were otherwise uninhabited by coeval therapsids (i.e., cynodonts).

Electrical and structural study of new antimony iodide-doped silver sulfate electrolytes

This paper deals with the preparation and ion transport characteristics of a series of compositions in the solid-state mixed system [(SbI3)100 − x –(Ag2SO4) x ] where x = 10, 20, 30, 40, 50, 60, 70, 80, and 90 mol%, respectively. These samples have been characterized by powder X-ray diffraction, differential scanning calorimetry, Fourier transform infrared spectroscopy, ionic transport number, and impedance spectroscopic measurements. Among various compositions investigated, significant ones have possessed AgI as one of the constituent phases. Detailed electrical conductivity studies have shown that the observed ionic conductivity attains a maximum value of 2.1 × 10−3 S cm−1 at room temperature (298 K) for the typical composition containing x = 60 mol%, whereas the corresponding values of transport number of silver ion as determined by Wagner’s and EMF methods are found to be nearly unity. Interestingly, the enhanced ionic conduction of the chosen composite system may be attributed to the feasibility of formation of AgI in several compositions as a consequence of ion exchange reaction between SbI3 and Ag2SO4.

Fission track ages of the Miocene Mizunami and Iwamura Groups in southeastern Gifu Prefecture, Central Japan

Fission track (FT) ages were determined for 14 tuff samples from the Miocene Mizunami and Iwamura groups in southeastern Gifu Prefecture, Central Japan. On the basis of FT ages for the Mizunami Group, the Hongo Formation was deposited ca. 17 Ma, and the Akeyo Formation was deposited at ∼17—16 Ma. For the Iwamura Group, the depositional age of the Agi Formation was found to be ca. 20—18 Ma and the lower part of the Toyama Formation was deposited at ∼17—16 Ma. Depositional FT ages for the Akeyo and Toyama formations are almost 1 Myr younger than their fossil ages.

Modulation of Localized Surface Plasmon Resonance of Nanostructured Gold Crystals by Tuning Their Tip Curvature with Assistance of Iodide and Silver(I) Ions

In this article, we describe a series of experiments that systematically addressed and clarified the effects of iodide, silver ions, and ascorbic acid (AA) concentration on the morphology of gold nanorods (Au NRs) during the overgrowth process. When iodide ions, silver ions, or both were present in the growth solution, a morphology of Au nanocrystals ranging from thick NRs, cuboidal shaped NRs, dogbone-like NRs, to dumbbell NRs, respectively, was obtained. The appearance of the third peak in the UV−vis spectra indicates the formation of lobes on the tips of Au NRs. In addition, when different seeds (such as Au NRs of short aspect ratio and spherical Au nanocrystals) whose {111} facets were covered by iodide ions were used, horns of different length on Au seeds were formed. Taken together, the results mentioned above and cross section change of the tips of Au NRs, two lobes instead of four formed on each tip of the Au NRs are explained for the first time, and their growth from {111} facets is assisted by the formation of AgI, which can catalytically reduce Au ions into atoms on those facets. The optical spectra of nanostructured Au crystals can be tuned from 520 to 955 nm by controlling their tip curvature or platinum coating. A wide color gamut can be readily obtained by using a random dispersion of nanostructured Au NR-based crystals.

Investigation of interfacial reaction kinetics of I −(aq) with Ag 2O(s) on Ag substrate: Determining mass transport and surface reaction rates

The reaction kinetics of AgI formation by reaction of Ag 2O films with aqueous iodide were followed by monitoring the open-circuit potential ( E OC). Previous studies have shown that complete conversion of Ag 2O to AgI is indicated by an abrupt transition in the E OC from a value close to the equilibrium potential for the Ag|Ag 2O|H 2O system to one close to that for Ag|AgI|I −, allowing an easy determination of the total reaction time, τ f . The solid–solution interfacial kinetic parameters can then be determined by measuring τ f as a function of the initial amount of Ag 2O and the I − concentration. In this study, the application of the technique was extended to examine the effect of I −(aq) transport to an Ag 2O surface by measuring τ f as a function of electrode rotation rate. By studying the chemical conversion as a function of electrode rotation rate we are able to separate mass transport effects from the reaction kinetics. The interfacial reaction follows kinetics typical of a sequential binary-reaction system consisting of mass transport to, followed by reaction at, the surface. The mass transport rate was proportional to the square root of the electrode rotation rate, consistent with the well-established diffusion-boundary layer model for a rotating disc. Varying the rotation rate allows a quantitative extrapolation of the data to the infinite rotation rate to determine the chemical reaction rate at the surface.

Influence of Iodide Ions on the Growth of Gold Nanorods: Tuning Tip Curvature and Surface Plasmon Resonance

This paper describes morphological and optical changes induced by seed-mediated growth of gold nanorods in the presence of iodide ions. Addition of small amounts of iodide to the growth solution results in the growth of nanoparticles with dumbbell-like structure, meaning that gold salt reduction takes place preferentially at the rod tips. However, when excess iodide is added, homogeneous rod growth is observed, and therefore the original shape is retained. By controlling the experimental conditions, the position of the longitudinal plasmon band of grown nanorods can be shifted up to as much as 250 nm. These optical effects were also simulated by means of the boundary element method (BEM), achieving an excellent agreement with the experimental spectra. X-ray photoelectron spectroscopy (XPS) and surface enhanced Raman spectroscopy (SERS) analysis of the gold nanorods before and after iodide addition revealed the presence of AuI and AgI at the particles surface. A growth mechanism is proposed on the basis of preferential iodide adsorption at the tips {111} facets, leading to the formation of AgI, followed by reduction of gold salt precursor due to a decrease in the surface redox potential.

Photo-induced morphological conversions of silver nanoparticles prepared using laser ablation in water—Enhanced morphological conversions using halogen etching

Our previous report showed that chloride ions enhanced photo(laser and fluorescent-light)-induced morphological conversions of silver nanoparticles prepared using laser ablation in pure water, in which spherical particles were converted to crystal-shaped nanoparticles such as nanoprisms or nanorods. In the present study, we investigated the morphological conversion of nanoparticles in iodide solutions and that of smaller nanoparticles in chloride solutions. In addition to the formation of crystal-shaped particles in photo-irradiated conditions, marked morphological changes in the dark conditions were observed in these solutions, which was different from the results of the previous study. Besides, the formation of AgI and AgCl 2 − was also detected. These findings confirm that halogen etching of silver plays a critical role in the morphological conversions. Photoirradiation at various wavelengths was also carried out to investigate the role of the photoirradiation. The formation of the crystal-shaped particles that occurred even by long wavelength (700 nm) irradiation indicates that the photoirradiation might control the interaction between silver atoms and the nanoparticle surface via electronic field excitation rather than the reduction rate of silver ions.

Galvanically coupled process for the conversion of Ag 2O to AgI

The conversion of Ag 2O, grown-on Ag substrates, to AgI has in been investigated, using open-circuit potential, linear polarization, and potentiostatic control measurements. Three distinct reaction stages were clearly identified from the time-dependent behaviour of the open-circuit potential, E OC, and the corrosion currents measured by linear polarization. In the early stages, when the silver surface was covered with a coherent Ag 2O film with low porosity, E OC ∼ ( E e ) Ag 2 O / Ag and only chemical conversion of Ag 2O to AgI was observed. As Ag 2O was consumed and the area of Ag exposed to I − solution increased, galvanic coupling of Ag 2O reduction to Ag and the oxidation of the Ag substrate to AgI also occurred. Once all the Ag 2O has been reduced, AgI formation stopped and E OC fell to ( E e) AgI/Ag. Chemical conversion was shown to produce fine particulate AgI whereas that formed anodically via galvanic coupling was in the form of large crystals. Since few larger crystals were observed, conversion via galvanic coupling appeared to be a minor process.

Steric hindrance as a rate controlling step in stress corrosion cracking

The effect of steric hindrance in the stress corrosion cracking (SCC) of Ag-15Pd (a/o) in AgI forming solutions was studied at room temperature. The solutions used were 1 M KI at a potential higher than that of AgI formation, and iodine dissolved in different n-alcohols. It was found that Ag-15Pd (a/o) is susceptible to intergranular stress corrosion cracking in those solutions. The SCC susceptibility measured as percentage of elongation to rupture and crack propagation rate is related to the size of the active species. While in KI aqueous solutions, as well as in iodine saturated benzene or iodine saturated toluene, the rate controlling step (RCS) was the reaction at the tip of the crack, in alcoholic-iodine solutions, the diffusion rate of the iodine containing molecules became the RCS.

In Vitro Corrosion of Dental Ag-based Alloys in Polyvinylpyrrolidone Iodine Solution

The corrosion and tarnish behaviors of three Ag-based alloys (Ag-Pd-Cu-Au alloy, Ag-In alloy, and Ag-Sn-Zn alloy) in polyvinylpyrrolidone iodine (povidone-iodine) solution were examined. The degree of tarnish was evaluated by visible-ray spectrocolorimetry. Corrosion potential measurements and analyses of corrosion products by X-ray diffractometry were carried out to elucidate the corrosion mechanism. The corrosion rate of the three Ag-based alloys in povidone-iodine solution at its practical concentration used as a gargle solution was so fast that the alloys tarnished within 10 seconds of immersion with the formation of AgI. Thermodynamic consideration and the results of surface analysis by X-ray diffractometry revealed that the main anodic and cathodic reactions were Ag + I(-)-->AgI + e- and I2 + 2e(-)-->2I- respectively.

Preparation of stable AsBr4+and I2As–PI3+salts. Why didn't we succeed to prepare AsI4+and As2X5+? A combined experimental and theoretical study

In analogy to our successful "PX2+" insertion reactions, an "AsX2+" insertion route was explored to obtain new arsenic halogen cations. Two new salts were prepared: AsBr4+[Al(OR)4]-, starting from AsBr3, Br2 and Ag[Al(OR)4], and I2As-PI3+[Al(OR)]4 from AsI3, PI3 and Ag[Al(OR)4](R=C(CF3)3). The first cation is formally a product of an "AsBr2+" insertion into the Br2 molecule and the latter clearly a "PI2+" insertion into the As-I bond of the AsI3 molecule. Both compounds were characterized by IR and NMR spectroscopy, the first also by its X-ray structure. Reactions of Ag[Al(OR)4] with AsI3 do not lead to ionization and AgI formation but rather lead to a marginally stable Ag(AsI3)2+[Al(OR)]4 salt. Despite many attempts we failed to prepare other PX-cation analogues such as AsI4+, As2X5+ and P4AsX2+(X=Br, I). To explain these negative results the thermodynamics of the formation of EX2+, EX4+ and E2X5+(E = As, P; X = Br, I) was carefully analyzed with MP2/TZVPP calculations and inclusion of entropy and solvation effects. We show that As2Br5+ is in very rapid equilibrium with AsBr2+ and AsBr3(DeltaGo((CH2Cl2))=+30 kJ mol(-1)). The extremely reactive AsBr2+ cation available in the equilibrium accounts for the observed decomposition of the [Al(OR)4]- anion. By contrast, the stability of AsI3 against Ag[Al(OR)4] appears to be kinetic and, if prepared by a suitable route, As2I5+ would be expected to have a stability intermediate between the known P2I5+ and P2Br5+.

Trimer formation of AgI. A gas-phase FT-IR and theoretical study

The vapour above AgI has been investigated in the range of 375–70 cm −1 by FT-IR spectroscopy. The spectrum shows two close-lying bands attributed to the stretching modes of silver iodide monomer (AgI) and trimer (Ag 3I 3). The bands have been assigned on the basis of thermodynamic and quantum chemical calculations. The thermodynamic analysis of the vapour composition revealed the major contribution of Ag 3I 3(g) up to 900 K while its abundance decreases at higher temperatures. This trend is in agreement with the observed relative band intensities in the IR spectrum. A comparative theoretical study of the analogous Ag 3Br 3 and Ag 3Cl 3 trimers justified the interchanging relative order of the stretching frequencies of AgX and Ag 3X 3 when going from X=Cl to I.

Complex impedance and structural analyses of the mixed system 40(Cu 1− xAg xI)–30(Ag 2O)–30(SeO 2), (0.05≤ x≤0.25)

Using complex impedance analysis, temperature-dependent electrical conductivity studies of various compositions of the mixed system 40(Cu 1− x Ag x I)–30(Ag 2O)–30(SeO 2), (0.05≤ x≤0.25) over the temperature region 295–445 K have been carried out. All the chosen compositions of the system exhibit Arrhenius type of conductivity as a function of temperature and their activation energies for conduction lie in the range 0.27–0.42 eV. The values of ionic transport number of these materials are greater than 0.96. The presence of AgI in these materials has been inferred from the β→α phase transition of AgI, which is characterized by an endothermic peak at around 416 K in the DSC traces of these specimens. While the structural analysis carried out by means of X-ray diffraction has revealed the formation of AgI, Ag 2SeO 4 and new phases involving glassy and crystalline compounds, the Fourier transform infrared (FTIR) spectroscopic results have indicated the presence of SeO 4 2−, SeO 3 2− and Se 2O 7 2− species thus confirming the ionic nature of the phases.

Determination of iodide in urine by ion-pair chromatography with electrochemical detection.

A variety of parameters affecting the determination of iodide in biological materials by ion-pair chromatography and electrochemical detection were examined in detail. It became apparent that the pH value, the ion-pair concentration, the proportion of organic solvent and of organic bases as a component of the buffer solution, as well as the salt concentration in the eluent system could effectively influence the retention characteristics of iodide in the chromatographic system, resulting in the separation of potential interfering substances. The presence of other anions in the sample matrix has to be taken into consideration, particularly thiocyanate because of its long retention time. Investigations of the electrochemical detection mechanism revealed that the reaction hitherto assumed to be responsible for detector signal generation (formation of AgI) is incorrect. In addition, a much more sensitive detection of iodide than that cited in the literature to date is possible if the detector potential is optimally selected and any anticipated interfering substances are removed by chromatography. Use of a gold electrode rather than a silver electrode also considerably enhances the reliability of the procedure.

Preparation and characterization of fast ionic solids in new ternary system CuI–Ag 2O–PbO 2

An experimental attempt was made to characterize a variety of compositions in a ternary system (CuI) x –(Ag 2O–PbO 2) 100− x where x=25, 30, 35, 40, 45, 50, 55, 60, 65 and 70 mol%. The samples were analysed using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, differential thermal analysis (DTA) and silver ionic transport number studies. The results of XRD, FTIR and DTA studies have revealed the formation of AgI and other phases in the various compositions of the system. The transport number measurements carried out by Wagner's and EMF methods have also indicated that silver ions are the majority charge carriers in these compositions.

The role of iodide promoter in selective oxidation of methanol to formaldehyde

The interaction of a CH3I promoter and a commercial electrolytic silver catalyst was investigated using XPS, UPS and in situ confocal microprobe Raman spectroscopy. XPS and UPS results show evidence for formation of AgI on the surface of the silver catalyst. Interestingly, XPS results show no evidence for formation of any carbon species on the silver catalyst at room temperature, implying that CH3I can be used as a “pure” I‐modifier in the catalytic oxidation of CH3OH to HCHO. UPS results show a positive work function change (Δφ > 0) for the I‐modified catalysts. In situ Raman studies show that both the adsorption and reaction of methanol were promoted on the modified silver surface. The present experimental results provide not only an understanding of the surface chemistry of the silver catalyst but also a further understanding of the promotion effect of CH3I in the selective oxidation of CH3OH to HCHO.

Fast ion transport in the new mixed system (CuI)x·[(Ag2O)2·(V2O5)]100−x (40≤x≤80)

The new mixed system (Cul)x·[(Ag2O)2·V2O5)]100−x where x=40, 45, 50, 55, 60, 65, 70, 75 and 80 mol% was investigated as a possible glassy fast ion conductor by preparing molten mixtures and quenching them to low temperatures. The analysis of their composition was carried out using differential scanning calorimetry (DSC) and powder X-ray diffraction (XRD) techniques. These studies have confirmed the formation of new substances. Formation of AgI in some samples was also revealed by XRD analysis and by the occurrence of a characteristic β → α phase transition temperature around 420 K identified through DSC experiments as well. Detailed temperature-dependent a.c. electrical conductivity studies were carried out on the new materials by a.c. impedance analysis in the frequency range 65.5 kHz-1 Hz and over the temperature range 293 to 398 K. It has been found that the highest electrical conductivity of 3.64×10−3 S cm−1 at 305 K due to the migration of Ag+ ions and the lowest activation energy of 0.1 eV in the above temperature range of investigation could be realized for the composition 40CuI-40Ag2O-20V2O5 in the mixed system.

X-ray diffraction and differential scanning calorimetry of a novel CuI Ag oxysalt solid electrolyte

Abstract Solid electrolytes of the system : xCuI(1−x) (Ag 2 O + MoO 3 ) have been prepared for various values of x, the molar fraction. X-ray Diffraction data has revealed the presence of AgI and Differential Scanning Calorimetry has confirmed this by the presence of an endothermic peak characteristic of the superionic transition of AgI at 150°C. The transport number for silver ions was nearly unity, and preliminary conductivity results showed a value of 10 −3 (Ωcm) −1 at room temperature. The formation of AgI by an exchange reaction between CuI and the silver oxysalt facilitates superionic behaviour similar to AgIag Oxysalts.