Iodide Ion Concentration Research Articles

Iodide ions concentration sensing using polymer-tipped optical fiber

The concentration of iodide (I − ) ions was determined by a fluorescence quenching method; a polymer-tipped optical fiber (PTOF) was used as the sensing head. The polymer tip, made by a free-radical photopolymerization method, combined the advantages of high sensitivity of the tapered fiber with a flexible and simple fabrication process. A sol–gel encapsulated fluorescein, used as the fluorescence indicator, was dip coated on the surface of the PTOF. Experimental results indicate that the backscatter fluorescence intensity collected by PTOF is 9.60 times higher than that of the flat-cut fiber. When the I − ions concentration changed from 6 to 36 mM, the backscatter fluorescence intensity collected by PTOF decreased linearly with a response time of 2 s. We demonstrate a method that can detect remote ion concentration with high repeatability, with stability, and which is simple to carry out. This method can be used in applications such as chemical production and water quality monitoring.

Development of a non-radioactive screening assay to detect chemicals disrupting the human sodium iodide symporter activity

Adequate concentration of iodide ions within thyroid epithelial cells, which is mediated by the sodium iodide symporter (NIS), is essential for proper thyroid hormone synthesis. Inhibition of NIS activity represents a potential mechanism by which goitrogens/toxicants can disrupt thyroid hormone physiology. It is necessary to develop a rapid, simple, inexpensive and sensitive screening assay to identify chemicals affecting NIS function. The current study compares the sensitivities of non-radioactive Sandell-Kolthoff (SK) reaction and radioactive iodide uptake (RAIU) in a previously described NIS assay. The EPAhNIS cell line (HEK293T stably transfected to over-express the human NIS) was tested with the reference NIS inhibitor (sodium perchlorate) across multiple log concentration range. The results from SK reaction in EPAhNIS cells showed similar performance to published RAIU results from the same cell line, in terms of assay screening coefficient (Z′) and variability (CV). Results from the reference chemicals tested in EPAhNIS cells revealed that SK reaction yielded IC50 and selectivity scores consistent with those observed for RAIU. However, RAIU seems marginally more sensitive than the SK reaction, as RAIU consistently detected weaker NIS inhibitors among the test chemicals. We developed a second hNIS assay based on the MCF-7 cell line. Applying reference anions and chemicals to MCF7hNIS cells, we found that in comparison with results from EPAhNIS cells, the SK reaction with MCF7hNIS: 1) yielded similar Z′ and CV; 2) had similar IC50 and selectivity scores for reference chemicals; 3) identified more NIS inhibitors among reference chemicals than SK reaction, but less than the RAIU assay in EPAhNIS cells. In conclusion, the SK reaction can be used with both EPAhNIS and MCF7hNIS cells to measure iodide uptake and identify NIS inhibitors, except for those presenting an extremely weak potency.

Microbial community structure in deep natural gas-bearing aquifers subjected to sulfate-containing fluid injection

In the natural gas field located in central Japan, high concentrations of natural gases and iodide ions are dissolved in formation water and commercially produced in deep aquifers. In the iodine recovery process, the produced formation water is amended with sulfate, and this fluid is injected into gas-bearing aquifers, which may lead to infrastructure corrosion by hydrogen sulfide. In this study, we examined the microbial community in aquifers subjected to sulfate-containing fluid injection. Formation water samples were collected from production wells located at different distances from the injection wells. The chemical analysis showed that the injection fluid contained oxygen, nitrate, nitrite and sulfate, in contrast to the formation water, which had previously been shown to be depleted in these components. Sulfur isotopic analysis indicated that sulfate derived from the injection fluid was present in the sample collected from near the injection wells. Quantitative and sequencing analysis of dissimilatory sulfite reductase and 16S rRNA genes revealed that sulfate-reducing bacteria (SRB), sulfur-oxidizing bacteria, and anaerobic methanotrophic archaea (ANME) in the wells located near injection wells were more abundant than those in wells located far from the injection wells, suggesting that fluid injection stimulated these microorganisms through the addition of oxygen, nitrate, nitrite and sulfate to the methane-rich aquifers. The predominant taxa were assigned to the ANME-2 group, its sulfate-reducing partner SEEP-SRB1 cluster and sulfur-oxidizing Epsilonproteobacteria. These results provide important insights for future studies to support the development of natural gas and iodine resources in Japan.

Concentration Determination of Volatile Molecular Iodine and Methyl Iodide

Appropriate and reliable methods are necessary for routine determination of the concentrations of molecular iodine (I2) and methyl iodide (CH3I), and methods including ultraviolet–visible spectrophotometry on aqueous solution samples for I2 detection and gas chromatography on toluene solution samples for CH3I detection may be used. In this study, we examined the adequacy of the existing spectrophotometric method in terms of absorption coefficients at specific light wavelengths for several pH values of the aqueous solutions and selected iodide ion concentrations, and confirmed it finding no dependence of the absorption coefficients on the solution pH and the iodide ion concentration. Additionally, we established methods for CH3I analysis using toluene as a sampling solvent for either capture of CH3I from a gaseous solution or extraction of CH3I from an aqueous solution, and found that using gas‐tight syringes, CH3I could be extracted without a significant CH3I loss even at ambient temperature.

Determination of Mass Concentration of Bromide, Iodide and Nitrate Ions in Water

Developed are projects of State Standards of Ukraine referring to determination of bromide, iodide, and nitrate ions in waters of different types. The method of determination of bromide,ions is based on registration of reflection spectra of products of bromination of phenol red, iodide ions—on the oxidation of the latter to iodine, its gas extraction to the solution of luminol and registration of chemiluminescence in the flow of carrier gas, nitrate ions—on chemiluminescence after reduction of nitrates to nitrites and gas extraction of nitrogen dioxide to the solution of luminol. The methods make it possible to determine bromide ions within the interval 0.02–0.5, iodide ions—0.006–0.5, nitrate ions—0.05–10 mg/dm3. A special attention is given to the study of interfering impact of water components and methods to remove it.

Cyclic Voltammetry Stripping Analysis to Determine Iodide Ion Concentration in Cu Plating Bath

Accurate monitoring of an electroplating bath's chemical balance is a key factor for maintaining its performance during a long-term plating operation. In this paper, a method is suggested to measure the concentration of iodide ion (I−), an inorganic leveler for through-silicon via (TSV) filling, based on its electrochemical response. During the operation of plating, I− was consumed via the reaction with Cu+ (Cu+ + I → CuI), an oxidation reaction (2I− → I2 + 2e), as well as a physical incorporation. The I− concentration decrease resulted in a degradation of the bath, while the major byproducts (CuI and I2) rarely influenced on bath performance. In order to monitor the I− concentration by cyclic voltammetry stripping (CVS) analysis, the electrochemical response of I− was examined at various conditions. I− suppressed the Cu electrodeposition rate; this response was dependent on the mass transport of I− and the applied potential of cathode. A subsequent effective coverage analysis revealed that not only I− but also Cu(I) iodide (CuI) was a key inhibitor, demonstrating that the inhibition of I− becomes weaker at a negative potential. With a responsive curve (RC)-CVS analysis conducted at an optimized condition, a linear relationship between the real and measured concentrations could be found, irrespective of other additives’ concentrations. The method suggested in this paper enabled the direct monitoring of the I− concentration in a Cu plating bath.

Highly sensitive and selective assay method for iodide ion determination based on gold nanoparticles conjugated with glycol chitosan

ABSTRACTA sensitive colorimetric method for the determination of iodide ions was developed using gold nanoparticles (AuNPs) functionalised with glycol chitosan (GCS). The iodide ions were at the centre of the O–I––O coordination structure, formed with the GCS-AuNPs, reducing their interparticle distance and inducing aggregation. Time-of-flight secondary ion mass spectrometry analyses showed that the bound iodide ions were coordinated to the oxygen atoms of the ethylene glycol in GCS, with this aggregation leading to a considerable variation in colour from light red to dark violet. Using this GCS-AuNP probe, the iodide ion concentration in environmental, biological and pharmaceutical samples could be determined by both the naked eye and UV-Vis spectroscopy. Additionally, the sensitivity of the detection was found to be markedly enhanced at pH 6, where a more pronounced colour change was observed. The absorption ratio A700/A521 of the functionalised AuNP solution correlated linearly with the iodide ion concentration within the range 0.0–10.0 mg/L, and the limits of detection in tap water, pond water, and bovine serum solution were 3.5, 3.6, and 3.4 μg/L, respectively. The present assay method can thus be utilised to rapidly measure the concentration of iodide ions in aqueous samples.

Self-Assembled Liquid-Crystalline Ion Conductors in Dye-Sensitized Solar Cells: Effects of Molecular Sensitizers on Their Performance.

Dye-sensitized solar cells employing nonvolatile liquid-crystalline (LC) electrolytes that form nanostructures capable of efficient ion transport are reported. The LC electrolyte consists of a cyclic carbonate-functionalized mesogen and an iodide-based ionic liquid that nanosegregates into lamellar structures exhibiting over four times higher ion conductivities parallel to the layers than perpendicular to the layers. The self-assembled ion pathways allow efficient ion transport in the semi-solid LC state. When used together with organic dyes, DSSCs employing these LC electrolytes show higher power conversion efficiency (PCE) than metal-organic dyes. This behavior is not observed for devices containing standard liquid electrolytes. The higher PCEs of the LC-based devices can be attributed to longer electron lifetimes (τ) and higher electron densities in the photoelectrodes. The high concentration of iodide ions in the nanostructured pathways of the LC electrolyte is thought to induce reductive quenching of the ruthenium-based sensitizer, which competes with the electron injection process and lowers the τ and electron densities of the TiO2 .

Bimetallic Nanoparticles with Exotic Facet Structures via Iodide-Assisted Reduction of Palladium

Iodide is arguably the most challenging halide to control as a shape-directing additive in metal nanoparticle synthesis and the addition of iodide during bimetallic nanoparticle growth often leads to inhomogeneously stellated products. Through judicious control of low micromolar concentrations of iodide ions in solution in a seed-mediated approach, alloyed gold–palladium tetradecapod nanoparticles have been synthesized with a mixture of both well-defined convex and concave surfaces. Notably, these particles are uniform and symmetrical, and this unusual combination of convex and concave features in a single nanostructure is not simply an artifact of intersecting spikes, as would be the case with stellated particles. Further, an important new role for iodide in catalyzing the reduction of palladium ions is identified, particularly at the edge sites of the growing gold nanoparticles. This differs from the commonly accepted theory that iodide slows metal ion reduction, and thus opens up promising new routes to the synthesis of other bimetallic nanoparticles with exotic shapes and surface structures.

Synergistic interactions between tetra butyl phosphonium hydroxide and iodide ions on the mild steel surface for corrosion inhibition in acidic medium

The corrosion inhibitive action of tetra butyl phosphonium hydroxide (TBPH) on mild steel was investigated in 0.5M H2SO4. On adding the potassium iodide (KI) to the solution corrosion inhibition efficiency was significantly improved. The inhibitive action of TBPH was investigated at various inhibitor concentrations and at various temperatures; however, a synergistic improvement in the performance was seen when 10−3M KI was added to TBPH solution. Potentiodynamic polarization studies at various concentrations of TBPH and (TBPH+KI) inhibitor revealed that TBPH is a mixed type of inhibitor for mild steel in 0.5M H2SO4. Synergistic effect of TBPH and KI in corrosion inhibition of mild steel in 0.5M H2SO4 containing a low concentration of iodide ions has been evaluated by potentiodynamic polarization and the results suggest that the iodide ions in solution stabilized the adsorption of TBPH molecule on the metal surface and improved the inhibition efficiency of TBPH. The corrosion behavior of steel in 0.5M H2SO4 in the absence and with various concentrations of the inhibitor was studied from (298 to 328) K. It was found that the inhibition efficiency increases with inhibitor concentration and decreases with TBPH and (TBPH+KI) solution with an increase in temperature. Potentiostatic polarization study shows that TBPH and (TBPH+KI) are passivation type of inhibitor. The adsorption of TBPH is found to follow Frumkin adsorption isotherm whereas the adsorption of (TBPH+KI) follows the Temkin adsorption isotherm. Kinetic and thermodynamic parameters namely effective activation energy (Ea), and Gibbs free energy of adsorption (∆Goads) indicate that adsorption of TBPH and (TBPH+KI) on mild steel surface is primarily physical in nature. The results of scanning electron microscopy, atomic force microscopy, and quantum chemical analysis support the above inferences.

Coordination Chemistry Dictates the Structural Defects in Lead Halide Perovskites.

We show the influence of species present in precursor solution during formation of lead halide perovskite materials on the structural defects of the films. The coordination of lead by competing solvent molecules and iodide ions dictate the type of complexes present in the films. Depending on the processing conditions all PbIS5 (+) , PbI2 S4, PbI3 S3 (-) , PbI4 S2 (2-) , PbI5 S2 (3-) , PbI6 (4-) and 1D (Pb2 I4 )n chains are observed by absorption measurements. Different parameters are studied such as polarity of the solvent, concentration of iodide ions, concentration of solvent molecules and temperature. It is concluded that strongly coordinating solvents will preferentially form species with a low number of iodide ions and less coordinative solvents generate high concentration of PbI6 (-) . We furthermore propose that all these plumbate ions may act as structural defects determining electronic properties of the photovoltaic films.

Studying Equilibrium in the Chemical Reaction between Ferric and Iodide Ions in Solution Using a Simple and Inexpensive Approach

A laboratory experiment on the study of the chemical equilibrium based on the reaction between ferric and iodide ions in solution with the formation of ferrous ions, free iodine, and triiodide ions is developed. The total concentration of iodide and triiodide ions in the reaction mixture during the reaction is determined by the argentometric titration; the concentrations of the other reagents and products are calculated using the material balance equations. The dependence of the equilibrium constant on temperature is also considered. The average values of Kc are 2.5 × 104 M–1 (35 °C) and 4.5 × 104 M–1 (45 °C). The experiment uses common reagents and simple equipment and can be performed in any educational laboratory. The basic procedure of processing the experimental data is quite simple and can be easily performed even by first-year students; however, the experiment can be extended in several ways to be suitable for advanced laboratory courses for upper-year undergraduates. Possible extensions are discus...

Electronic tongue for simultaneous determination of cyanide, thiocyanate and iodide

Five cross selective electrodes comprising cyanide, thiocyanate, and iodide coated graphite electrodes CGEs were used as sensing parts of an electronic tongue for simultaneous determination of cyanide, thiocyanate, and iodide ions in the presence and the absence of chloride ion as a coexisting ion. The CGEs were constructed using poly(vinyl chloride) (PVC), o-nitrophenyl octyl ether (o-NPOE), cetyltrimethylammonium bromide (CTAB), and metal–porphyrin complexes as ionophores. The constructed electrodes were characterized to obtain their calibration curve, response time, and repeatability.A programmed switching system combined with an array of the five potentiometric coated graphite electrodes (i.e., ion-selective or cross-selective electrodes) were connected directly to a pH/potentiometer and a computer to sequentially acquire the potential corresponding to water sample mixtures. The acquired potentials were recorded and saved on the computer and were used as input variables for an artificial neural network to simultaneously yield the concentrations of cyanide, thiocyanate and iodide ions in simple and complex mixtures. A feed-forward, back propagation network with a Levenburg–Maquart algorithm was employed to optimize the network parameters.

On solubility of europium monoxide in melts of (NaBr + NaI) system at T = 973 K

Equilibria of EuO dissolution and dissociation in molten (NaBr+NaI) mixtures of 0.77:0.23 and 0.31:0.69 compositions at T=973K were studied by potentiometric titration method using Pt(O2)|ZrO2(Y2O3) indicator electrode. The solubility product indices of EuO are (7.81±0.08) and (8.43±0.16) in the melts of 0.77:0.23 and 0.31:0.69 compositions. The corresponding dissociation constant indices are (4.96±0.04) and (5.54±0.06), respectively (all the parameters are in molality). Non-dissociated EuO is the prevailing form in all the saturated solutions of europium monoxide. The decrease of the iodide ion concentration in the melts results in strengthening of EuO dissociation that is explained by introduction of harder Pearson’s base (Br−) in sodium iodide melt. In its turn this increases the fixation degree of Eu2+ in mixed halide complexes. The total solubility of EuO decreases going from NaI melt to the (bromide+iodide) mixtures that is caused by the decrease of ‘physical’ solubility of non-dissociated oxide which occupies hollow spaces of enough large size in the ionic solvents. The quantity of these hollow spaces diminishes at the sequential Br−→I− substitution.

Selective ligandless cloud point extraction of palladium from water and dust samples.

In this study, the phase-separation phenomenon of non-ionic surfactants was used for separation and preconcentration of Pd(II). The cloud point extraction (CPE) method is based on the formation of PdI2 which is then entrapped in the non-ionic surfactant Triton X-114. Ethanol acidified with 0.5 M HNO3 was added to the surfactant-rich phase prior to its analysis by flame atomic absorption spectrometry. The main factors affecting CPE efficiency, such as sample solution pH, concentration of iodide ion and Triton X-114, equilibration temperature and time, were all investigated and optimized. At optimum conditions, a calibration curve was constructed for the determination of palladium according to the ligandless CPE procedure. Linearity was maintained between 1.0 to 500.0 ng/mL. The LOD based on three times the SD of the blank divided by the slope of analytical curve, (3Sb/m) was 0.3 ng/mL. Seven replicate determinations of a solution containing of 4.0 μg palladium gave a mean absorbance of 0.359 with RSD±1.85%. The high efficiency of CPE to carry out the determination of palladium in complex matrixes was demonstrated. The proposed method has been applied to the determination of trace amounts of palladium in a platinum-iridium alloy, water, and dust samples, with satisfactory results.

Electrochemical quantification of iodide ions in synthetic urine using silver nanoparticles: a proof-of-concept.

Typical urinary iodide concentrations range from 0.3 μM to 6.0 μM. The conventional analytical method is based on the Sandell-Kolthoff reaction. It involves the toxic reagent, arsenic acid, and a waiting time of 30 minutes for the iodide ions to reduce the cerium(iv) ions. In the presented work, an alternative fast electrochemical method based on a silver nanoparticle modified electrode is proposed. Cyclic voltammetry was performed with a freshly modified electrode in presence of iodide ions and the voltammetric peaks corresponding to the oxidation of silver to silver iodide and the reverse reaction were recorded. The peak height of the reduction signal of silver iodide was used to plot a calibration line for the iodide ions. Two calibration plots for the iodide ions were obtained, one in 0.1 M sodium nitrate (a chloride-ion free environment to circumvent any interference from the other halides) and another in synthetic urine (which contains 0.2 M KCl). In both of the calibration plots, linear relationships were found between the reduction peak height and the iodide ion concentration of 0.3 μM to 6.0 μM. A slope of 1.46 × 10(-2) A M(-1) and a R(2) value of 0.999 were obtained for the iodide detection in sodium nitrate. For the synthetic urine experiments, a slope of 3.58 × 10(-3) A M(-1) and a R(2) value of 0.942 were measured. A robust iodide sensor with the potential to be developed into a point-of-care system has been validated.

Modeling study for oscillatory reaction of chlorite – iodide – ethyl acetoacetate

Chlorine dioxide based chemical oscillating behavior was modeled by a simple scheme consisting of three component reactions. Furthermore, little is known about the influence of the pH value. In this study, four component reactions were used to model the chlorite – iodide – ethyl acetoacetate oscillating reaction by dynamic analysis software. The oscillatory phenomenon is observed for concentration changes of triiodide ion, chlorite ion, and hydrogen ion. The initial concentration of ethyl acetoacetate, chlorite ion, iodide ion, and hydrogen ion has great influence on oscillations. The amplitude and number of oscillations are associated with the initial reactant concentrations. The equation of the reaction rate of triiodide ion, chlorite ion, or hydrogen ion changing with reaction time and initial concentrations in the oscillation stage was obtained. The bifurcation surface between oscillatory and nonoscillatory behavior with different pH values was obtained. The spatial zone for the occurrence of oscillation is reduced with an increase in the pH value. The range of oscillation as concentrations of chlorine dioxide, iodine, and ethyl acetoacetate is well described by an equation. There is a lower limit on ethyl acetoacetate initial concentration for oscillation. However, there is a higher limit on chlorine dioxide and iodine concentration for oscillation. The concentrations of chlorine dioxide and iodine for oscillation decrease with an increase in the pH value. The results provide new theoretical evidence of the importance of pH value, which can affect the bifurcation surface between oscillatory and nonoscillatory behavior.

Adsorption of iodide ions on liquid (Ga + In) electrode from mixed solutions with constant ionic strength in dimethylsulfoxide

The adsorption of iodide ions on a liquid (Ga + In) electrode of an eutectic composition (14.2 at % In) from mixed electrolyte (xc M NaJ + (1 − x)c M NaClO4) solutions in dimethylsulfoxide containing surface inactive ions ClO4− with the constant ionic strength of 0.1 M is studied by measuring differential capacitance curves at 305 K. The analysis of experimental data for the studied interval of iodide ion concentration shows that the charge of specifically adsorbed ions on the liquid electrode surface is much lower as compared with the charge found for their adsorption from aqueous solutions of the same electrolyte. The applicability of various adsorption isotherms for the description of experimental data is analyzed. The virial isotherm with the linear dependence of the adsorption free energy on the electrode charge provides the best description. The obtained data on adsorbability of iodide ions are compared with available literature data in aqueous and dimethylsulfoxide solutions on various electrodes.

Shape-controlled growth of surface-confined Au nanostructures for electroanalytical applications

We describe the growth of raspberry-like Au nanostructures by surface-confined seed-mediated growth approach at room temperature without using any polymer/surfactant or templates and their electroanalytical applications towards the enzyme-free sensing of glucose and detection of ultratrace amount of toxic Cr(VI). The growth of Au nanostructures involves the initial deposition of Au nanoseeds on a conducting support and the further growth of the seeds by chemical route using a growth solution containing hydroxylamine, potassium iodide and HAuCl4. Raspberry-like nanoparticles with an average size of 370nm was obtained at low concentration of iodide ions (10μM) whereas quasispherical nanoparticles with an average size of 220nm was obtained at high concentration (>100μM). The preferential adsorption of iodide ions on (111) plane inhibits the growth of nanoparticles in (111) direction. The raspberry-like nanoparticles has significantly high electrochemically accessible surface area of 0.29cm2 with respect to the other nanoparticles. The raspberry-like nanoparticles has excellent catalytic activity towards oxidation of glucose and reduction of Cr(VI). High sensitivity and wide linear response (0.5–12mM) towards glucose have been achieved in neutral pH without additional mediators or enzymes. The electrochemical detection of Cr(VI) was performed in acidic condition and the nanoparticle-based electrode could detect Cr(VI) at parts-per-billion level. The electrode is highly stable and can be used for repeated measurements without compromising the sensitivity and detection limit. The electrocatalytic performance of raspberry-like nanoparticles is significantly higher than the other nanoparticles. The surface morphology/structure and the particle coverage control the electrocatalytic performance of the particles.

Factors affecting the formation of iodo-trihalomethanes during oxidation with chlorine dioxide

Effects of water characteristics, reaction time, temperature, bromide and iodide ion concentrations, oxidant doses, and pH on formation of iodinated trihalomethanes (I-THM) during oxidation of iodide-containing water with chlorine dioxide (ClO2) were investigated. Among the water samples collected from ten water sources, iodoform (CHI3) was the predominant I-THM and trace amount of chlorodiiodomethane (CHClI2) was occasionally found. CHI3 yields correlated moderately with specific UV absorbance (SUVA) (R2=0.79), indicating that hydrophobic aromatic content were important precursors. Longer reaction time led to continued formation of CHI3. I-THM containing bromide was also found in waters containing both bromide and iodide, but CHI3 was dominant. The formation of CHI3 was higher at 25°C than 5°C and 35°C. CHI3 formation showed an increase followed by a decrease trend with increasing ClO2 doses and iodide concentrations and the highest yields occurred at iodide to ClO2 molar ratios of 1–2. pH 8 resulted in the highest CHI3 formation. It should be noted that a high iodide concentration was spiked to waters before adding ClO2 and the results may not reflect the formation yields of iodinated THMs in real conditions, but they provide information about formation trend of I-THM during oxidation of ClO2.