Formation Of AgI Research Articles

Evaluation of imidazole blocking layers for perovskite stability

The prevention of AgI formation is critical for ensuring long term stability of perovskite solar cells. While sputtered metal oxide films are known for uniform dense film formation, solution phase nanoparticle coatings of metal oxides are prone to pinholes through which free iodide can migrate leading to AgI formation at the back contact. Iodide migration can be prevented through the addition of passivator or blocking layers at the perovskite/charge transport or charge transport/Ag interfaces. In this paper we evaluated a series of imidazoles as interfacial layers to prevent iodide migration from the perovskite to the Ag back contact through solution phase deposited Y:SnO2. We identified structural features of the imidazoles that contribute to an effective blocking layer. Specifically, it was found that imidazoles with conjugated planer systems and hydrogen bonding heteroatoms were able to prevent ion migration while retaining device performance. Of the materials evaluated 4-(Imidazol-1-yl)phenol had the best performance with a 60 % increase in stability verse the control under illumination at short circuit conditions.

Simultaneous resistance switching and rectifying effects in a single hybrid perovskite

AbstractHalide perovskites with naturally coupled electron‐ion dynamics hold great potential for nonvolatile memory applications. Self‐rectifying memristors are promising as they can avoid sneak currents and simplify device configuration. Here we report a self‐rectifying memristor firstly achieved in a single perovskite (NHCINH3)3PbI5 (abbreviated as (IFA)3PbI5), which is sandwiched by Ag and ITO electrodes as the simplest cell in a crossbar array device configuration. The iodide ions of (IFA)3PbI5 can be easily activated, of which the migration in the bulk contributes to the resistance hysteresis and the reaction with Ag at the interface contributes to the spontaneous formation of AgI. The perfect combination of n‐type AgI and p‐type (IFA)3PbI5 gives rise to the rectification function like a p–n diode. Such a self‐rectifying memristor exhibits the record‐low set power consumption and voltage. This work emphasizes that the multifunction of ions in perovskites can simplify the fabrication procedure, decrease the programming power, and increase the integration density of future memory devices.image

Concurrence of Late Triassic lithostratigraphic, radioisotopic, and biostratigraphic data support a Carnian age for the Popo Agie Formation (Chugwater Group), Wyoming, USA

The Upper Triassic Popo Agie Formation of the Chugwater Group of Wyoming, northeastern Utah, and northwestern Colorado has been an enigmatic unit since its definition and is commonly excluded from large-scale studies of continental Upper Triassic strata in the western USA. Lithostratigraphic correlations of Popo Agie Formation outcrops are documented from west-central Wyoming through northeastern Utah and northwestern Colorado, which demonstrates the presence of the Popo Agie Formation throughout this region. Unique detrital zircon age distributions have led previous workers to hypothesize a paleodrainage connecting basal units of the Dockum in west Texas and eastern New Mexico, USA, with the Gartra Grit, a basal unit of the Popo Agie in northeastern Utah. Biostratigraphically informative taxa such as parasuchid phytosaurs in the absence of leptosuchmorph phytosaurs support an assignment of the Gartra Grit and Popo Agie Formation to the Otischalkian estimated holochronozone. We present the first detrital zircon age distributions for the Popo Agie Formation. Multidimensional scaling analysis of zircon populations shows that the Popo Agie samples are similar to other Upper Triassic units surrounding the Ancestral Uncompahgre Highlands, Central Colorado Trough, and the Ancestral Front Range. Additionally, we present the first maximum depositional ages (youngest population) for the Popo Agie Formation at a location where the top of the ochre unit is no older than 225 ± 4 Ma, and the upper purple to ochre transition is no older than 230 ± 5 Ma. By leveraging existing biostratigraphy, regional lithostratigraphy, and new radioisotopic ages we temporally constrain the Popo Agie Formation, enabling us to integrate the upper Chugwater Group, Chinle Formation, and Dockum Group strata into a testable Late Triassic chronostratigraphic framework for the western USA. The consilience of data support a Carnian age for the majority (if not entirety) of the Popo Agie Formation, making this—and equivalent strata in the Dockum Group (i.e., Camp Springs Conglomerate, and strata of the Tecolotito and Los Esteros members of the Santa Rosa Formation)—among the oldest continental Late Triassic stratigraphic units in the western USA.

A New Rhynchosaur Taxon from the Popo Agie Formation, WY: Implications for a Northern Pangean Early-Late Triassic (Carnian) Fauna

New discoveries in the lower Popo Agie Formation (lower carbonate unit) of central Wyoming necessitated a reevaluation of USNM 494329 from the same unit, the only known hyperodapedontine rhynchosaur in western North America. Well known from Gondwanan deposits, hyperodapedontines appear to be restricted to the Carnian age (Late Triassic), with the exception of Teyumbaita in the earliest Norian age (Late Triassic) of Brazil. Initially assigned to c.f. ‘Hyperodapedon’ sanjuanensis, our phylogenetic analyses reject this hypothesis, in support of a sister relationship between USNM 494329 (Beesiiwo cooowuse, gen. et. sp. nov.) and Oryctorhynchus bairdi forming an early-diverging clade that is only distantly related to ‘H.’ sanjuanensis. Five additional specimens recovered from the lower Popo Agie are described. Three are referred to B. cooowuse, and another two are placed closer to Hyperodapedon and the remainder of Hyperodapedontinae. Our analysis demonstrates potential temporal distinction between a grade of earliest-diverging hyperodapedontines (including all Wyoming taxa) and a exclusively Late Carnian, Southern Pangaean hyperodapedontine clade (including ‘H.’ sanjuanensis). We consider the lower Popo Agie Formation to represent the first nonmarine Late Triassic unit of Western North America that can be confidently restricted to the Carnian age.

Analysis of Iodide Transport on Methyl Ammonium Lead Iodide Perovskite Solar Cell Structure Through Operando Hard X-ray Photoelectron Spectroscopy

To analyze the dynamic of ion species through a MAPbI3–xClx (HaP) solar cell, an operando hard X-ray photoelectron spectroscopy (HAXPES) study was proposed. Stacked Au/Ag/AZO/PCBM/HaP/NiO/ITO/glass structures, where AZO, PCBM, NiO, and ITO stand for Al-doped zinc oxide, phenyl-C61-butyric acid methyl ester, nickel oxide, and indium tin oxide, respectively, were evaluated. Experimental core level analysis under an applied bias voltage highlighted that a certain threshold voltage (above the open-circuit voltage (VOC)) is required to trigger the iodide (I–) migration from the HaP to the adjacent electron and hole transport layers. Study also demonstrated that the diffusion of I– in AZO/PCBM over time is unidirectional and follows the gradient descent in concentration. We observed that the irreversibility of the I– transport leads to the absorption of I– by the Ag layer to form a silver iodide (AgI) compound. Furthermore, this work also pointed out the efficiency of an ITO layer when deposited between Ag and AZO to serve as the ion diffusion barrier layer. Finally, the results demonstrated that the presence of ITO restrains the AgI formation and contributes to improving cell performances.

Highly Sensitive Adsorption and Detection of Iodide in Aqueous Solution by a Post-Synthesized Zirconium-Organic Framework

Effective methods of detection and removal of iodide ions (I-) from radioactive wastewater are urgently needed and developing them remains a great challenge. In this work, an Ag+ decorated stable nano-MOF UiO-66-(COOH)2 was developed for the I- to simultaneously capture and sense in aqueous solution. Due to the uncoordinated carboxylate groups on the UiO-66-(COOH)2 framework, Ag+ was successfully incorporated into the MOF and enhanced the intrinsic fluorescence of MOF. After adding iodide ions, Ag+ would be produced, following the formation of AgI. As a result, Ag+@UiO-66-(COOH)2 can be utilized for the removal of I- in aqueous solution, even in the presence of other common ionic ions (NO2-, NO3-, F-, SO42-). The removal capacity as high as 235.5 mg/g was calculated by Langmuir model; moreover, the fluorescence of Ag+@UiO-66-(COOH)2 gradually decreases with the deposition of AgI, which can be quantitatively depicted by a linear equation. The limit of detection toward I- is calculated to be 0.58 ppm.

Stability and degradation in triple cation and methyl ammonium lead iodide perovskite solar cells mediated via Au and Ag electrodes

Perovskite solar cells (PSCs), particularly based on the methyl ammonium lead iodide (MAPbI3) formulation, have been of intense interest for the past decade within the photovoltaics (PV) community, given the stupendous rise in power conversion efficiencies (PCEs) attributed to these perovskite formulations, where PCEs have exceeded 25%. However, their long-term stability under operational conditions and environmental storage are still prime challenges to be overcome towards their commercialization. Although studies on the intrinsic perovskite absorber stability have been conducted previously, there are no clear mechanisms for the interaction of electrode-induced absorber degradation pathways, which is the focus of this study. In this report, we have conducted a comprehensive analysis on the impact of the electrode collector layer, specifically Ag and Au, on the degradation mechanism associated with the MAPbI3 and a triple cation absorber, Cs0.05FA0.79MA0.16PbI2.45Br0.55. Notably, Au-based PSCs for both absorbers in an n-i-p architecture showed superior PCE over Ag-based PSCs, where the optimized PCE of MAPbI3 and triple cation-based PSCs was 15.39% and 18.21%, respectively. On the other hand, optimized PCE of MAPbI3 and triple cation-based PSCs with Ag electrodes was 3.02% and 16.44%, respectively. In addition, the Ag-based PSCs showed a rapid decrease in PCE over Au-based PSCs through operational stability measurements. We hypothesize the mechanism of degradation, arising from the Ag interaction with the absorber through the formation of AgI in the PSCs, leads to corrosion of the perovskite absorber, as opposed to the benign AuI when Au electrodes are used in the solar cell stack. Additionally, novel use of photoluminescence spectroscopy (PL) here, allowed us to access key features of the perovskite absorber in situ, while it was in contact with the various layers within the n-i-p solar cell stack. A quenching in the PL peak in the case of Ag-contacted MAPbI3 provided direct evidence of the Ag corrupting the optical properties of the absorber through the formation of AgI which our X-ray diffraction (XRD) results confirmed. This was supported by the fact that an emission peak was still present in the triple cation Ag-device. For the Au-contacted MAPbI3 the presence of a well-defined PL peak, though attenuated from the triple cation Au-device, suggested the AuI does not quell the emission spectrum for either the triple cation or the MAPbI3 absorber. The findings should aid in the understanding and design of new electrode materials with PSCs, which will help accelerate their introduction into the commercial sector in the future.

Synthesis of TiO2/Ti3C2Tx/AgI Z-scheme photocatalyst for tetracycline hydrochloride photocatalytic degradation

A ternary composite photocatalyst with high catalytic activity (TiO2/Ti3C2Tx/AgI) was synthesized using the simple solvothermal and coprecipitation methods. The structure, morphology, photoelectric properties, and photocatalytic activity of the prepared materials were studied using various characterization techniques. The composite catalysts TiO2/Ti3C2Tx/AgI with different proportions of TiO2/Ti3C2Tx to AgI of 10%, 20%, 50%, 70%, and 90% were prepared by varying the amounts of AgNO3 and KI. Compared to AgI and TiO2/Ti3C2Tx, TiO2/Ti3C2Tx/AgI demonstrated a superior photocatalytic degradation activity for tetracycline hydrochloride (TCH) under simulated sunlight. The degradation rate of TCH with 70% TiO2/Ti3C2Tx/AgI composite photocatalyst reached 97%. The photoluminescence (PL) emission spectra showed that the recombination of photogenerated electrons of 70% TiO2/Ti3C2Tx/AgI was effectively inhibited after the formation of AgI, TiO2, and Ti3C2Tx heterojunctions. The electrochemical impedance spectroscopy (EIS) indicated that a rapid interfacial charge transfer of the 70% TiO2/Ti3C2Tx/AgI composite to the electron acceptors (Ti3C2Tx). Ti3C2Tx had high conductivity and can effectively accelerate the transfer and separation of photogenerated carriers as a charge medium. Therefore, the enhancement of photocatalytic activity of TiO2/Ti3C2Tx/AgI can be attributed to the Z-scheme heterojunction with non-metal Ti3C2Tx as the solid medium. In addition, the trapping agent experiment showed that superoxide radicals, singlet oxygen, and holes were the main active substances in the photocatalytic degradation of TCH by the TiO2/Ti3C2Tx/AgI composite.

Inhibition of iodide ion migration in flexible perovskite solar cells using oxide–metal–oxide transparent electrode

Oxide–Metal (Ag)–Oxide films (OMO) are good candidates as flexible transparent electrodes for the perovskite solar cells (PSCs) because of their higher transmittance (∼86%), lower sheet resistance (∼7 Ω/sq), and superior bending property compared to those of the conventional indium tin oxide transparent electrodes. However, when OMO is used in PSCs, the iodide ions of the perovskite layer diffuse into the silver layer, resulting in the formation of AgI, an insulator. The formation of AgI lowers the conductivity of the OMO. As a result, the power conversion efficiency (PCE) and long-term driving stability of PSCs are decreased. To solve this problem, we introduced diethanolamine (DEA), known as an anti-corrosion additive, into the electron transport layer to prevent the binding between iodine and silver. To investigate the effect of DEA, we observed the change of sheet resistance of OMO films and photovoltaic performance of OMO-based PSCs according to DEA addition in SnO2. Furthermore, X-ray photoelectron spectroscopy was performed to confirm the formation and inhibition of AgI. We found that upon adding DEA, the PCE of PSCs increased to 11.3% and the operational stability improved from the existing 12 h to a maximum of 60 h, while maintaining more than 70% of the initial efficiency. Therefore, we think that the results of this study might suggest guidelines to use OMO transparent electrode for PSCs, and is helpful for the commercialization of PSCs.

Rhodanine-based fluorometric sequential monitoring of silver (I) and iodide ions: Experiment, DFT calculation and multifarious applications

A simple rhodanine derived fluorophoric unit has been designed for selective detection of Ag+ and I- ions in DMSO-H2O medium. The sensor R1 showed an obvious “turn-on” fluorescence response toward Ag+ due to the inhibition of both C-N single bond free rotation, internal charge transfer (ICT) and the formation of chelation enhanced fluorescence (CHEF) effects. The fluorescence quantum yield (Φ) was increased from 0.0013 to 0.032 for receptor R1 upon the Ag+-complexation. In addition, the 1:1 complexing stoichiometry was employed based on Job’s plot analysis with detection limit of 24.23 × 10−7 M. Conversely, receptor R1+Ag+ particularly detects I- ion over other co-existing anions by the “turn-off” fluorescence response due to the formation of AgI, displacing the receptor R1 with the quantum yield of 0.0014. The detection limit was calculated to be 22.83 × 10−7 M. The sensing behaviour of receptor R1 toward Ag+ was also supported by density functional theory (DFT) calculations. Moreover, the sensing ability of reported receptor R1 could be exercised in multifarious applications like paper strip, silica-supported analysis, staining test for latent finger print, logical behaviour, smartphone-assisted quantitative detection and real water samples studies.

A novel phosphorus oxide quantum dots as an emissive nanomaterial for inorganic ions screening and bioimaging

In this work, a novel blue-green fluorescence phosphorous oxide quantum dots (PO QDs) was synthesized by solvothermal method in N-methyl-2-pyrrolidone (NMP) solution without any protection treatment during synthesis. Upon excitation at 400 nm, PO QDs emitted blue-green fluorescence with quantum yield of 0.28. PO QDs exhibited the high inertness to air or moisture, the excellent water solubility, and stable emission intensity in a wide pH range and in high ionic strength solution. Interestingly, PO QDs could give the positive optical response to iron ions (Fe3+) and iodine ion (I−). The photoluminescence (PL) of PO QDs could be directly quenched by Fe3+. While I− quenched the PO QDs PL by means of Ag+-mediated PO QDs system via the internal filtration effects (IFE) induced by the formation of AgI. Moreover, the biocompatibility and low toxicity of PO QDs verified in bean sprout and Hela cells indicated the promising application of PO QDs in medicine related fields. Furthermore, PO QDs could also be utilized in luminescent composite film for various application scenarios

Reevaluation of the holotypes of Koskinonodon princeps Branson and Mehl, 1929, and Borborophagus wyomingensis Branson and Mehl, 1929 (Temnospondyli, Metoposauridae)

ABSTRACT Metoposaurids are some of the most commonly occurring tetrapods in non-marine Upper Triassic sediments in the northern hemisphere of Pangea. Since the first description of a metoposaurid in 1842, nearly two dozen species have been named, but many of these have been regarded with increasing skepticism by modern workers because of minor differences used to validate novel species and sometimes novel genera. More recent comprehensive descriptions and evaluations of intraspecific variation from several presumed monospecific bonebeds of metoposaurids have prompted reevaluation of holotypes due to variation in proposed apomorphies. Four metoposaurid species were named from the Popo Agie Formation exposures of Wyoming, U.S.A., but at present, only a single species, Anaschisma browni, is considered valid following a recent redescription of two of these taxa (An. browni and An. brachygnatha). The other two taxa, Borborophagus wyomingensis and Koskinonodon princeps, have not been redescribed since their original description in 1929. A redescription of the holotypes of these two taxa is presented here to assess their historic synonymy with An. browni and to provide a detailed, updated record of the Popo Agie Formation metoposaurids in light of a historic relative lack of attention compared with other North American deposits. Our confirmation of the conspecificity of all four Popo Agie Formation metoposaurids permits a detailed discussion of potential ontogenetic variation in the Popo Agie Formation metoposaurids and latitudinal variability in An. browni.

The osteology and phylogenetic position of the loricatan (Archosauria: Pseudosuchia) Heptasuchus clarki, from the ?Mid-Upper Triassic, southeastern Big Horn Mountains, Central Wyoming (USA).

Loricatan pseudosuchians (known as “rauisuchians”) typically consist of poorly understood fragmentary remains known worldwide from the Middle Triassic to the end of the Triassic Period. Renewed interest and the discovery of more complete specimens recently revolutionized our understanding of the relationships of archosaurs, the origin of Crocodylomorpha, and the paleobiology of these animals. However, there are still few loricatans known from the Middle to early portion of the Late Triassic and the forms that occur during this time are largely known from southern Pangea or Europe. Heptasuchus clarki was the first formally recognized North American “rauisuchian” and was collected from a poorly sampled and disparately fossiliferous sequence of Triassic strata in North America. Exposed along the trend of the Casper Arch flanking the southeastern Big Horn Mountains, the type locality of Heptasuchus clarki occurs within a sequence of red beds above the Alcova Limestone and Crow Mountain formations within the Chugwater Group. The age of the type locality is poorly constrained to the Middle—early Late Triassic and is likely similar to or just older than that of the Popo Agie Formation assemblage from the western portion of Wyoming. The holotype consists of associated cranial elements found in situ, and the referred specimens consist of crania and postcrania. Thus, about 30% of the osteology of the taxon is preserved. All of the pseudosuchian elements collected at the locality appear to belong to Heptasuchus clarki and the taxon is not a chimera as previously hypothesized. Heptasuchus clarki is distinct from all other archosaurs by the presence of large, posteriorly directed flanges on the parabasisphenoid and a distinct, orbit-overhanging postfrontal. Our phylogenetic hypothesis posits a sister-taxon relationship between Heptasuchus clarki and the Ladinian-aged Batrachotomus kupferzellensis from current-day Germany within Loricata. These two taxa share a number of apomorphies from across the skull and their phylogenetic position further supports ‘rauisuchian’ paraphyly. A minimum of three individuals of Heptasuchus are present at the type locality suggesting that a group of individuals died together, similar to other aggregations of loricatans (e.g., Heptasuchus, Batrachotomus, Decuriasuchus, Postosuchus).

Redescription of Anaschisma (Temnospondyli: Metoposauridae) from the Late Triassic of Wyoming and the phylogeny of the Metoposauridae

Metoposaurids are non-marine temnospondyls that are among the most common constituents of Late Triassic deposits, but despite their abundance, the evolutionary relationships of the group are poorly resolved and have not been fully addressed with modern phylogenetic methods. The genus Anaschisma is one of a number of poorly resolved metoposaurid taxa and was erected to describe two species from the Popo Agie Formation (Carnian) in Wyoming: Anaschisma browni and Anaschisma brachygnatha. Since being named, the genus has been repeatedly synonymized and separated with other taxa in the context of broader revisions of the Metoposauridae. At present, Anaschisma is considered to be an indeterminate metoposaurid. Extensive descriptive work of metoposaurids since the erection of Anaschisma in 1905 and the last taxonomic review of the clade in 1993, including the naming of several new taxa and the reappraisal of several others, has generated a sufficiently detailed database through which to re-evaluate the taxonomy of the Metoposauridae as part of the analysis of phylogenetic relationships of Anaschisma. Here we reappraise and redescribe the holotypes of A. browni and A. brachygnatha to determine their taxonomic status and relationships in the context of an updated and revised metoposaurid phylogenetic framework. Anaschisma browni and Anaschisma brachygnatha are synonymized under the former species, as all previously listed diagnostic differences are compatible with intraspecific variation. Additionally, the well-known Koskinonodon perfectus is found to be a junior synonym of Anaschisma browni, which takes taxonomic precedence given its earlier description. Poor phylogenetic resolution of the Metoposauridae is likely the product of marked morphological conservatism within the clade and limited character sampling, although some patterns of regional clustering are apparent from the analysis.

Adsorption of volatile organic and iodine compounds over silver-exchanged mordenites: A comparative periodic DFT study for several silver loadings

The ability of Ag-exchanged mordenite (Ag-MOR) to capture iodine species such as I2 and CH3I as released for instance during a nuclear accident could be severely limited by the presence of volatile organic compounds (VOCs) that can disrupt their adsorption in the zeolite. Here, using density functional theory (DFT), we investigate in detail the adsorption process of several hydrocarbons (methane, cyclohexane, benzene, and 1,3-dimethylbenzene) and oxygenated compounds (methanol, ethanol, propan-2-ol and propanone) and compare it with the adsorption of I2 and CH3I for different values of the Si/Al ratio of the Ag-exchanged mordenite. It is found that the adsorption process of the iodine species becomes favorable as the Si/Al ratio is decreased. Indeed at high Si/Al ratio, some VOCs such as benzene, 1, 3-dimethylbenzene and propan-2-ol exhibit strong inhibiting effects, while at low Si/Al ratio, only the adsorption of CH3I is limited by the presence of aromatic hydrocarbons. Also, in addition to the elongation of the II bond upon the adsorption of the iodine molecule in Ag-MOR with a high silver content, we found that there is a significant electron transfer between the Ag and I atoms. Thus, our results indicate that the II bond becomes weaker during the adsorption and therefore the formation of AgI precipitates is favored.

Effect of quenching rate on electrical conductivity and glass formation of AgI–Ag2SO4–TeO2–B2O3 system

Effect of quenching rate on electrical properties and glass formation of 60AgI–40[0.6667Ag2SO4–0.3333(0.4TeO2–0.6B2O3)], 20AgI–80[0.6667Ag2SO4–0.3333(0.4TeO2–0.6B2O3)] systems was studied. Two systems of samples were prepared by melt quenching method with three different quench media such as air, ice and liquid nitrogen. X-ray diffraction and AC conductivity results show that cooling rate heavily effect the periodic order of atoms and electrical properties of samples respectively. Phase transition, glass transition and crystallization temperatures were determined from Differential scanning calorimetry results. The average AC conductivity of quenched samples increases with increasing the quenching rate. DC conductivity results show that the activation energy decreases with quenching rate. From the impedance spectroscopy, real and imaginary parts of impedances (Z′, Z″), conductivities were obtained and plotted Cole–Cole plots and these plots reveal grain and grain boundary resistance. The dielectric response of the system has been studied with frequency at different temperature, quenching media and activation energy calculated from loss tangent peak shift, which agrees with activation energy obtained from DC conductivity.

Effect of hydrocarbon production on reflection amplitude properties of reservoirs—a case study of Kov Field, Niger Delta, Nigeria

A better understanding of how hydrocarbons and other fluids such as brine move in the reservoirs within the Kov Field will enable the improved application of secondary recovery methods such as water and gas injections and also highlight areas within the field that have remaining hydrocarbons. This work focuses on the two major sandstone reservoir intervals, the AG-I and the AG-II all within the Agbada Formation, since they showed prominent amplitude changes. In the AG-I Formation, the results obtained from the production data and rock physics modeling show an increase in the amplitude impedance (AI) contrast around injection wells and a decrease in AI contrast around production wells due to fluid replacement, and it also deals with the pressure changes in correlation to the water injection performed to maintain the reservoir pressure, while in the AG-II Formation, the effect of hydrocarbon production serves to visualize and map the oil-water contact (OWC) as it evolves with the production time; the OWC is not observable on later seismic vintages because the reservoir drops below the OWC. Conclusively, the effect of hydrocarbon production throughout the reservoir and across the entire Field would be beneficial in mapping fluid changes in the Kov Field, which can be utilized for enhanced oil recovery and improved reservoir management.

Effect of NOx on AgI formation in Ag-mordenite

Ag loaded mordenite can be used as a trap for radio-iodine arising from nuclear reprocessing operations. Typically, iodine is trapped in the Ag loaded mordenite by the formation of AgI in the pores of the mordenite, through a solid-vapour reaction. In the presence of NOx and water vapour, AgI is most likely formed by liquid-vapour reaction between AgNO3 and I2. This reaction results in the formation of large aggregates of AgI crystals on the surface of the mordenite, also leading to a yellow colouration of the mordenite, which is not observed when NOx and water vapour is absent.

Study on the Preparation and Characteristics of Cellulose/Silver Iodide Nanocomposite Film.

In this study, the structure and properties of an organic-inorganic composite material prepared from cellulose doped with fine particles of silver iodide (AgI) were examined. The preparation of the composite involved the complexation of cellulose with polyiodide ions, such as I- and 13-, by immersion in iodine/potassium iodide (I2/KI: 0.2, 0.4, 0.6, 0.8, 1.0 M) or potassium iodide (KI: 0.6, 1.2, 1.8, 2.4, 3.0 M) aqueous solutions followed by reaction in a silver nitrate (AgNO3:1.0 M) aqueous solution. These procedures resulted in the in situ formation of fine β-AgI particles within the cellulose matrix. The characteristics and conductivities of prepared cellulose/silver iodide (AgI) nanocomposite films with different I2/KI and KI concentrations were investigated. AgI particle formation and aggregation increased on increasing I2/KI and KI concentrations as determined by SEM. X-ray results showed that KI could penetrate the cellulose crystal region and form AgI particles. The electrical conductivities of nanocomposite films treated with KI were higher than that of I2/KI at < 1.0 M of I2/KI and 3 M of KI, although the weight gain by AgI formation was lower than that of I2/KI. This was also attributed to the formation of smaller AgI particles and crystal defects. Highest electrical conductivity (3.8 x 10(-7) Ω(-1) cm(-1)) was obtained from the cellulose films (1.25 x 10(-11) Ω(-1) cm(-1)) treated with the aqueous solutions of 1.0 M I2/KI and 1.0 M AgNO3.

Sacrificial Silver Nanoparticles: Reducing GeI2 To Form Hollow Germanium Nanoparticles by Electroless Deposition.

Herein we report the electroless deposition of Ge onto sacrificial Ag nanoparticle (NP) templates to form hollow Ge NPs. The formation of AgI is a necessary component for this reaction. Through a systematic study of surface passivating ligands, we determined that tri-n-octylphosphine is necessary to facilitate the formation of hollow Ge NPs by acting as a transport agent for GeI2 and the oxidized Ag(+) cation (i.e., AgI product). Annular dark-field (ADF) scanning transmission electron microscopy (STEM) imaging of incomplete reactions revealed Ag/Ge core/shell NPs; in contrast, completed reactions displayed hollow Ge NPs with pinholes which is consistent with the known method for dissolution of the nanotemplate. Characterization of the hollow Ge NPs was performed by transmission electron microscopy, ADF-STEM, energy-dispersive X-ray spectroscopy, UV-vis spectrophotometry, and Raman spectroscopy. The galvanic replacement reaction of Ag with GeI2 offers a versatile method for controlling the structure of Ge nanomaterials.