Silver Iodide Research Articles

The Structure of Water Condensate Nuclei in the Field of Surface Crystalline Defects on the Basal Face of β-AgI

The basal face of the silver iodide crystal in the absence of defects in unsaturated water vapors is covered with a continuous monomolecular film with a marked honeycomb-like cellular structure. Nanoscopic surface defects in the shape of a rectangular tower lead to the complete destruction of the film, so that the adsorption mechanism is changed entirely. The adsorption begins on the lateral faces of the defects, where the crystalline electric field prevents the formation of intermolecular hydrogen bonds. Water molecules are held by direct interactions with the crystal lattice ions and are aligned in the form of chains along the force lines of the electric field of the defect without forming stable clusters. At the next stage, the molecules are attached to the top of the defect, and only then the carrying surface between defects is filled. The adsorbate structure is resistant to temperature variations in the range from the freezing point to the boiling point of water. Computer simulation is performed by the Monte Carlo method using a detailed model implying the summation of polarization interactions over large distances.

Specific Features of Enzymatic Degradation of Chitosan Acetate and Chitosan Succinamide in Polymer-Colloid Dispersions with Silver Iodide Sols

Enzymatic degradation of polymer-colloid dispersions of chitosan acetate and chitosan succinamide with silver iodide sols was studied. The enzymatic degradation rate both in solutions and in film samples decreases in the presence of charged particles of the lyophobic sol. This fact is due to the enzyme inhibition by silver ions and to changes in the conformational and supramolecular state of the polymers.

Stacking Disorder by Design: Factors Governing the Polytypism of Silver Iodide upon Precipitation and Formation from the Superionic Phase

Silver iodide (AgI) is used for a wide range of applications from photocatalysis and antimicrobial coatings to photography and ice nucleation. By fitting powder X-ray diffraction patterns with DIFFaX, we show that AgI displays a strong tendency to form stacking-disordered materials. Its polytypism is determined by the silver cation to iodide molar ratio upon precipitation. Under iodide-rich conditions, fully hexagonal β-AgI is obtained, whereas a maximal percentage of cubic stacking of 81% is obtained at a 2:1 molar ratio in the silver cation-rich regime. These findings are explained on the basis of a concentration-dependent competition between kinetically and thermodynamically favored adsorption processes. Furthermore, the previously reported memory effects, observed upon transforming hexagonal and cubic AgI to the high-temperature superionic phase and back, are now followed quantitatively. We propose that the memory effects originate from excess ions at the surfaces of AgI crystals that stabilize the pyroelectricity of AgI associated with hexagonal stacking. The ability to “design” the polytypism of AgI by tuning the precipitation conditions provides the first example where the stacking disorder of a material can be controlled in a continuous fashion. Future studies will clarify if this design principle can be applied to other materials as well.

Factors Affecting the Adsorption of Some Ionic Dyes on the Surface of Modify CaO from Eggshell

In this paper, calcium oxide (CaO) was produced by the thermal treatment of eggshell. The doping process with silver iodide (AgI), oxygen (O), sulfur(S) and nitrogen (N) was achieved by adsorbents. The adsorption of Acid fuchsine (AF), Indigo Carmine (IC), Nigrosine (NG) and Alizarine Red S (AR) on the surface of these particles was studied. The different conditions affecting the adsorption process, such as the time of equilibrium, the primary concentration of the studied dyes, the amount of the adsorbent, the acidic function, the speed of the pruning motion and the temperature were studied. The pH stability time (5-10 minutes), IC and NG (30 minutes) and AR were (90 minutes). The effect of temperature was also studied within the range (25-45 ° C). The results showed that the adsorption capacity increased by increasing the temperature, ie the reaction is endothermic. The study showed the effect of the acidic function on the percentage of pigmentation. The percentage was increased by increasing the acidic function in the basal circles on the surfaces except for the AR dye. It decreased the percentage by increasing the acidic function. The effect of the weight of the adsorbent was studied on the percentage of adsorption.

Anion–cation dynamic cooperation in a paradigmatic ionic conductor around its superionic transition

Silver iodide (AgI) is one of the most extensively studied superionic conductors. In this work, we have applied the standard Buckingham pair potential and standard charge. For the first time the microscopic dynamic events that allow the achievement of the superionic transition are revealed. A collaborative effect among cations and anions that makes possible the hopping mechanism within the appropriate timescale is revealed.

Matrix-Independent Highly Conductive Composites for Electrodes and Interconnects in Stretchable Electronics.

Electrically conductive composites (ECCs) hold great promise in stretchable electronics because of their printability, facile preparation, elasticity, and possibility for large-area fabrication. A high conductivity at steady state and during mechanical deformation is a critical property for ECCs, and extensive efforts have been made to improve the conductivity. However, most of those approaches are exclusively functional to a specific polymer matrix, restricting their capability to meet other requirements, such as mechanical, adhesive, and thermomechanical properties. Here, we report a generic approach to prepare ECCs with conductivity close to that of bulk metals and maintain their conductivity during stretching. This approach iodizes the surfactants on the commercial silver flakes, and subsequent photo exposure converts these silver iodide nanoparticles to silver nanoparticles. The ECCs based on silver nanoparticle-covered silver flakes exhibit high conductivity because of the removal of insulating surfactants as well as the enhanced contact between flakes. The treatment of silver flakes is independent of the polymer matrix and provides the flexibility in matrix selection. In the development of stretchable interconnects, ECCs can be prepared with the same polymer as the substrate to ensure strong adhesion between interconnects and the substrate. For the fabrication of on-skin electrodes, a polymer matrix of low modulus can be selected to enhance conformal contact with the skin for reduced impedance.

Visible light photocatalytic conversion of CO2 in aqueous solution using 2D-structured carbon-based catalyst-coated β,γ-AgI nanocomposite

Solar-light-driven carbon-based photocatalysts have been widely used for CO2 conversion reaction. In this work, silver iodide (AgI)-decorated 2D structure graphitic carbon nitride (GCN) composite was prepared using nitrogen-rich melamine precursor and the characterization results reveal that the mixture of hexagonal wurtzite and cubic phases of β,γ-AgI are incorporated on GCN surface. Consequently, the photoconversion of CO2 over AgI/GCN composite was tested under visible light irradiation in triethanolamine medium. The main products from CO2 conversion were methane, acetone and ethanol. Besides, the effects of metal AgI loading (0.5–1.5%), the amount of photocatalyst (1–4 g/L) and irradiation time for CO2 photoconversion were evaluated. Furthermore, the charge separation mechanism associated with the AgI/GCN composite for CO2 photoconversion was also discussed.

Comparison of electrodeposition and precipitation for the preparation of samples for iodine analysis by AMS

Sample preparation for Accelerator Mass Spectrometry (AMS) analysis of 129I from environmental samples typically involves isolation and purification of the iodine followed by precipitation as silver iodide. The silver iodide is mixed with silver or niobium powder as a binder and medium for electrical conductivity and approximately 3 mg of the mixture pressed into a cathode for AMS analysis. Electrodeposited silver iodide on a silver clad niobium 50 µm diameter wire provides an attractive alternative to precipitation. Six inches of wire and electrodeposited silver iodide are easier to handle when pressing cathodes and minimizes possible cross contamination between samples. Although electrodeposition onto pure silver wires has been recently reported, the usage of silver clad niobium wires could offer an additional advantage. The use of niobium in the silver iodide matrix has been reported to result in higher intensity and long term stability of the iodide ion current. This paper presents a comparison of electrodeposition methods using silver and silver clad niobium wires to the traditional precipitated silver iodide mixed with silver and niobium powders. The comparison was done using materials with 129/127I ratios having nominal values of 5 × 10−10 and 5 × 10−11.For each 129/127I ratio material, eight samples were analyzed for each preparation method on three days, with seven replicate AMS measurements per sample. For each ratio, the measurements of the separate days were combined for each method, yielding 168 measurements per method. An analysis of variance indicated minor statistical differences between the precipitated and electro-deposited materials, with the pooled standard error of the means being 0.2% for both ∼5 × 10−10 and ∼5 × 10−11 ratios.

A Transformational Approach to Winter Orographic Weather Modification Research: The SNOWIE Project

AbstractThe Seeded and Natural Orographic Wintertime Clouds: The Idaho Experiment (SNOWIE) project aims to study the impacts of cloud seeding on winter orographic clouds. The field campaign took place in Idaho between 7 January and 17 March 2017 and employed a comprehensive suite of instrumentation, including ground-based radars and airborne sensors, to collect in situ and remotely sensed data in and around clouds containing supercooled liquid water before and after seeding with silver iodide aerosol particles. The seeding material was released primarily by an aircraft. It was hypothesized that the dispersal of the seeding material from aircraft would produce zigzag lines of silver iodide as it dispersed downwind. In several cases, unambiguous zigzag lines of reflectivity were detected by radar, and in situ measurements within these lines have been examined to determine the microphysical response of the cloud to seeding. The measurements from SNOWIE aim to address long-standing questions about the efficacy of cloud seeding, starting with documenting the physical chain of events following seeding. The data will also be used to evaluate and improve computer modeling parameterizations, including a new cloud-seeding parameterization designed to further evaluate and quantify the impacts of cloud seeding.

A visible-light-driven photoelectrochemical molecularly imprinted sensor based on titanium dioxide nanotube arrays loaded with silver iodide nanoparticles for the sensitive detection of benzoyl peroxide.

A novel ultrasensitive photoelectrochemical sensor for benzoyl peroxide (BPO) was constructed under visible light irradiation. A novel nanostructured material made of molecularly imprinted polymer (MIP)-modified silver iodide nanoparticle-titanium dioxide nanotube arrays (AgINPs-TiO2 NTs) was designed as a photoactive electrode (denoted as MIP@AgINPs-TiO2 NTs). AgI-sensitized TiO2 nanotube arrays were prepared by a simple dissolution-precipitation-calcination process and then employed as a matrix to graft the MIP recognition element. Such a newly designed molecularly imprinted photoelectrochemical sensor exhibits high sensitivity and selectivity for the determination of BPO. The photoelectrochemical analysis is highly linear over the BPO concentration range from 1 × 10-12 mol L-1 to 5 × 10-10 mol L-1 with a detection limit of 2.53 × 10-13 mol L-1 (S/N = 3, n = 11). The sensor designed based on a low cost and highly sensitive assay was successfully applied in the determination of BPO in spiked samples.

Nucleation of Condensed Phase in Water Vapor on the Nanostructured Surface of a β-AgI Crystal. 2. Free Energy

The free energy and work of nucleation of condensed water phase from vapor on a nanostructured basal face of a silver iodide crystal at 260 and 400 K have been calculated from the first principles of statistical mechanics by the Monte Carlo bicanonical statistical ensemble method. Relatively large structural elements have been represented by regularly repeating truncated pyramids with a base size of 8 nm and a height of 3 nm. For the interactions, a detailed model has been employed, which comprises the Ewald summation of long-range electrostatic and polarization interactions with the substrate. The dependences of the free energy and work of nucleation on the sizes of nuclei have been compared with the corresponding dependences for a smooth basal face of the crystal. Surface nanostructuring increases the thermodynamic stability of the nuclei by an order of magnitude and “extends” the process of their growth by five to six orders of magnitude to the region of lower pressures. Relatively large sizes of the nanostructure elements promote a decrease in the free energy of the uptake of water molecules at an initial stage of nucleation.

Nucleation of Condensed Phase in Water Vapor on the Nanostructured Surface of a β-AgI Crystal. 1. Spatial Organization

The Monte Carlo method has been employed to carry out computer simulation of condensed water phase nuclei on a basal face of a silver iodide crystal at temperatures of 260 and 400 K. Comparison between the calculated spatial correlation functions of molecules located on nanostructured and smooth substrates has indicated a destructive action of the electric field of the nanostructure on molecular clusters. At the initial stage of absorption, vapor molecules are retained on the nanostructured surface without the formation of interparticle bonds; therewith, initially absorbed molecules are bonded to the structured substrate substantially more strongly than to the smooth surface, on which intermolecular interactions play a significant role in their retention. The electric field of the nanostructured surface has a destructive effect on intermolecular hydrogen bonds. The temperature dependence of the number of hydrogen bonds exhibits an inverse pattern, at which an increase in the temperature within some region of conditions is accompanied by the recovery of some bonds rather than their rupture. A simplified model has been proposed to explain this effect.

Computer Simulation of Water Vapor Adsorption on the Surface of a Crystal β-AgI Regular Shape Nanoparticle

The Gibbs free energy and water vapor adsorption isotherms on the surface of a silver iodide nanoparticle at a temperature of 260 K have been calculated via the bicanonical statistic ensemble at the molecular level. The profiles of dependences reveal the capability of a surface to retain microdroplets in water vapors, as well as evidencing the condensation scenario of the formation of the contact between the dense phase and the solid surface as the most feasible way of heterogeneous nucleation under atmospheric conditions.

Molecular Cycles (H2O)n on the Substrates with Hexagonal Crystal Structure

Formation of molecular cycles on the surface of crystalline silver iodide in contact with water vapor is simulated by the Monte Carlo method. The pictures of molecular chains and rings formed on the crystalline substrate are obtained. The stability of molecular associates under thermal fluctuations is analyzed in terms of free energy and entropy calculated from the first principles of statistical mechanics. An improved model is used to describe the molecular forces of adhesion to the crystalline substrate by taking into account long-range polarization and dispersion interactions. The field of the crystalline substrate facilitates formation of five- and six-molecule rings and prevents formation of four-molecule rings. The displacement of five-molecule rings by six-molecule rings is a collective effect requiring that a sufficient number of molecules be accumulated on the surface.

Ultrafast fabrication of thermally stable protein-coated silver iodide nanoparticles for solid-state superionic conductors.

Solid-state ionic conductor is an essential and critical part of electrochemical devices such as batteries and sensors. Nano-sized silver iodide (AgI) is the most promising ionic conductor due to its superionic conductivity at room temperature. In recent years, proteins have been used as organic templates to obtain high-performance solid-state ionic conductors as well as to extend their applications in a biosensor. Here, we report the unprecedented ultrafast synthesis of thermally stable protein-coated AgI nanoparticles (NPs) through the photo-irradiation method for solid-state electrolyte. The synthesis was performed using a hyperthermostable bacterial β-glucosidase. The protein-coated AgI NPs with an approximate diameter of 13 nm showed that the controllable transition from the α- to β-/γ-phase was drastically suppressed down to 41 °C in the cooling process. After drying, the product represents a thermally stable organic-inorganic hybrid system with superionic conductivity. It is noteworthy that the superionic conductivity (σ ˜ 0.14 S/cm at 170 °C) of thermally stable protein-coated AgI NPs is maintained during several thermal cycles (25-170 °C). To our knowledge, this is the first report showing the diffusion of mobile Ag+ ions on the surface of the AgI NPs through a protein matrix. The facile synthesis method and high performance of the protein-coated AgI NPs may provide a latent application in the mass production of nanobatteries and other technological applications.

Rapid Sonochemically Assisted and Environmentally Benign Green Synthesis of Silver Iodide Nanoparticles with Photocatalytic Properties

Rapid Sonochemically Assisted and Environmentally Benign Green Synthesis of Silver Iodide Nanoparticles with Photocatalytic Properties

Reversible Photocurrent Switching in Ionic and Superionic Conductors of Polycrystalline Silver Iodide

Photocurrent switching effect plays vital roles in a number of optoelectronic devices especially for the construction of various logic gates. In the conventional photocurrent switching materials, electrons and holes are the charge carriers. Here we propose that the ionic and superionic photocurrent in some polymorphs of silver iodide is also switchable. We observed that the polarity of photocurrent in the polycrystalline γ-AgI is positive when an area near the negative electrode is irradiated with visible light and photocurrent switched to negative values while area near the positive electrode is photoirradiated. Polycrystalline α-AgI derived from γ-AgI also shows the photocurrent switching effect, depending on the photoirradiation position. Such a complete polarity switching phenomenon was not obtained in polycrystalline β-AgI as well as the α-AgI derived from β-AgI. Usually, the polarity of the photocurrent is changed by reversing photoelectrode potential or by using light of different wavelengths or in...

Big bore and extremely flexible mid-infrared hollow waveguide for gas absorption module

Big-bore, low-loss, and extremely flexible hollow waveguides were fabricated for mid-infrared spectroscopic gas sensing. The waveguide with inner/outer diameter of 1.4/2.0 mm can be curved with a bending radius as small as 1.4 cm A module of gas absorption cell for spectroscopic sensing was proposed with the hollow waveguide curved into a channeled substrate. Hollow waveguide with inner coatings of silver and silver iodide films attains low loss in the mid-infrared region for methane gas detection. Sensing properties for the module was experimentally discussed. Limit of detection of 6 ppm was obtained by using an FTIR (Fourier Transform infrared spectroscopy) system and DTGS (deuterated triglycine sulfate) detector. Comparisons were made to metallic hollow waveguide only with silver inner coating.

Evaluation of the Wyoming Weather Modification Pilot Project (WWMPP) Using Two Approaches: Traditional Statistics and Ensemble Modeling

AbstractThe Wyoming Weather Modification Pilot Project randomized cloud seeding experiment was a crossover statistical experiment conducted over two mountain ranges in eastern Wyoming and lasted for 6 years (2008–13). The goal of the experiment was to determine if cloud seeding of orographic barriers could increase snowfall and snowpack. The experimental design included triply redundant snow gauges deployed in a target–control configuration, covariate snow gauges to account for precipitation variability, and ground-based seeding with silver iodide (AgI). The outcomes of this experiment are evaluated with the statistical–physical experiment design and with ensemble modeling. The root regression ratio (RRR) applied to 118 experimental units provided insufficient statistical evidence (p value of 0.28) to reject the null hypothesis that there was no effect from ground-based cloud seeding. Ensemble modeling estimates of the impact of ground-based seeding provide an alternate evaluation of the 6-yr experiment. The results of the model ensemble approach with and without seeding estimated a mean enhancement of precipitation of 5%, with an inner-quartile range of 3%–7%. Estimating the impact on annual precipitation over these mountain ranges requires results from another study that indicated that approximately 30% of the annual precipitation results from clouds identified as seedable within the seeding experiment. Thus the seeding impact is on the order of 1.5% of the annual precipitation, compared to 1% for the statistical–physical experiment, which was not sufficient to reject the null hypothesis. These results provide an estimate of the impact of ground-based cloud seeding in the Sierra Madre and Medicine Bow Mountains in Wyoming that accounts for uncertainties in both initial conditions and model physics.

Reactivity of Silver Iodide (β-AgI) Surfaces: A Density Functional Theory Study

Silver iodide (AgI) aerosols may be produced in severe nuclear accidents and are typically used to favor the formation of droplets, inducing rain. To elucidate their behavior, we study surface stab...