AgBr Emulsion Research Articles

Influence of Binder and Dyes on the Mechanism of Tunnel Luminescence of AgBr(I) Microcrystals

It has been previously found that, in the AgBr(I) emulsion microcrystals (with a silver content corresponding to pBr 4), the centers responsible for tunnel recombination at T = 77 K with a luminescence maximum at λmax ≈ 560 nm when excited by light from the absorption region of the AgBr(I) emulsion microcrystal (λ ≈ 450 nm) as a result of temperature “quenching” are subject to structural transformation into the centers that, under the same excitation, provide the tunnel recombination with a wavelength depending on a binder: λmax ≈ 720 nm for the AgBr(I) emulsion microcrystals obtained in water and λmax ≈ 750 nm for those obtained in gelatin. In this work, similar structural transformations of the centers that determine the tunnel recombination at λmax ≈ 560 nm to the centers with a glow at λmax ≈ 720 nm are implemented for the AgBr(I) emulsion microcrystals synthesized in polyvinyl alcohol at an increase in the content of silver ions in the emulsion from pBr 4 to pBr 7. The mobile interstitial silver ions Ag $$_{i}^{ + }$$ are responsible for this transformation, as follows from the results obtained. The effect of the binder on the recombination processes in the AgBr(I) emulsion microcrystals is manifested in changes in the kinetics of the increase in luminescence from λmax ≈ 560 nm when light is excited from the absorption region of the AgBr(I) emulsion microcrystal (λ ≈ 450 nm) to a stationary level. The increase in luminescence at λmax ≈ 560 nm occurs monotonously from zero to the maximum stationary level at the binder whose molecules do not interact with the centers Ag $$_{{in}}^{ + }$$ , n = 1, 2 (water, polyvinyl alcohol at pBr 4). The kinetics of the increase in luminescence in the AgBr (I) emulsion microcrystals to a stationary level at λ ≈ 560 nm and pBr 4 is characterized by the presence of “flash enhancement” at a binder (in our case, gelatin (G)) whose molecules form the (Ag $$_{{in}}^{0}$$ G+) complexes with the Ag $$_{{in}}^{ + }$$ (n = 1, 2) centers. The adsorption on the AgBr(I) emulsion microcrystal (polyvinyl alcohol) surface of the dye is manifested as follows: if the kinetics of increase in luminescence at λmax ≈ 560 nm when excited by light from the region of the AgBr(I) emulsion microcrystal absorption (λ ≈ 450 nm) to the stationary level demonstrates “flash enhancement” prior to the introduction of dye, then, after the introduction of dye, the increase in luminescence at λmax ≈ 560 nm occurs monotonically from zero to a maximum fixed level. Studies of the “flash” of the luminescence stimulated by infrared (IR) radiation have shown that, after the termination of the exciting light when the kinetics of the increase in luminescence from λmax ≈ 560 nm to a stationary level demonstrates “flash enhancement”, the “flash” stimulated by IR radiation is not observed at λ ≈ 560 nm. In the absence of “flash enhancement”, a “flash” at λ ≈ 560 nm is observed. The results obtained, from our point of view, indicate that “flash enhancement” is due to the presence of deep centers of the localization of the electrons with a small capture cross-section and not to a photochemical reaction stimulated by the exciting light.

Improvement of the Hydrogen Microprint Technique on AHSS Steels

Preferential hydrogen diffusion paths in low-carbon ferritic steel and transformation-induced plasticity (TRIP) steel characteristic of new advanced high strength sheet steels (AHSS) were evaluated via the hydrogen microprint technique (HMT). As a consequence of hydrogen diffusion and evolution from the sample after charging, the technique involves reduction of AgBr emulsion applied to the surface of a charged sample to produce discrete Ag grains which identify, via scanning electron microscope (SEM) imaging, locations where hydrogen evolved. Enhancements to the results are revealed through a newly developed image-before-etch HMT method, consisting of SEM imaging before and then again after etching. The modified technique was implemented to facilitate direct comparison of silver grains with the features of an etched multi-phase TRIP steel microstructure. Results from SEM imaging demonstrated the effectiveness of the image-before-etch method to avoid artifacts and to positively identify hydrogen evolution sites in AHSS TRIP steel microstructures.

Modeling of heavy ion collisions using radial basis function and generalized regression neural networks

Artificial neural networks (ANNs) have been applied to heavy ion collisions. In the present work, the possibility of using ANN methods for modeling the multiplicity distributions, P(ns), of shower particles produced from p, d, 4He, 6Li, 7Li, 12C, 16O, and 24Mg interactions with light (CNO) as well as heavy (AgBr) emulsions at 4.5 A GeV/c was investigated. Two different ANN approaches, namely radial basis function neural network (RBFNN) and generalized regression neural network (GRNN), were employed to obtain a mathematical formula describing these collisions. The results from RBFNN and GRNN models showed good agreement with the experimental data. GRNN models have a better performance than the RBFNN models. This study showed that the RBFNN and GRNN models are capable of accurately predicting the P(ns) of shower particles in the training and testing phases.

AgBr (I) 乳剤膜および微結晶の低温でのトリボルミネセンス

AgBr (I) 乳剤膜および微結晶の低温でのトリボルミネセンス

Target Fragmentation at 4.5 a GeV/c in 24Mg and 28Si with Emulsion Interaction

The correlations between the multiplicity distributions and the projectile fragments, as well as the correlations between the black and grey fragments were given and the analysis of the projection of the transverse momentum, angular characteristics and azimuthal alignment were analyzed for the presence collective flow of nuclear matter in interactions of 24Mg and 28Si with AgBr emulsion nuclei at 4.5 AGeV/c.

Photoprocess in AgBr microcrystals in the presence of Pt(II) and Pd(II) complex ions

Results of a systematic study of the chemical sensitization of cubic-faceted AgBr emulsion microcrystals with complex compounds K2[XY4] and Na6[XZ4] [X = Pd, Pt; Y = Br−, Cl−, SCN−; Z =(SO3)2−] were considered. The role of secondary dissociation of complex ions during the chemical sensitizing was established. Conditions were determined in which the compounds specified can be used as chemical sensitizers of AgBr. The effect of these complexes on the basic photographic characteristics was demonstrated.

On Differences in Photoluminescent and Photographic Characteristics of AgBr (100) and AgBr (111) Microcrystals I: Unsensitized and Reduction Sensitized Emulsions

A study has been carried out on photoluminescence (PL) and photoluminescence excitation (PLE) of unsensitized and reduction sensitized cubic and octahedral AgBr emulsions. It has been determined that the PL spectra of cubic and octahedral microcrystals differ. This difference is explained by the formation of polyhalogenoargentate complex anions (PHACA) during the synthesis of octahedral microcrystals. These PHACA adsorb on the microcrystal surface, resulting in appearance of PL bands which are not observed for cubic microcrystals. PHACA can be transformed, after capturing an electron from a reducing agent, into negatively charged fragments, which are efficient hole traps. It is found that Agl - 2 and AgBrl - complexes, which can be formed during the synthesis of nominally pure AgBr octahedral microcrystals, play an important role in reduction sensitization. The PLE spectra of the 550 and 590 nm PL bands, which appear upon reduction sensitization of octahedral AgBr microcrystals, have maxima at 3.75 and 2.80 eV for the 550 nm band and 3.81 and 2.88 eV for the 590 nm band. The energy difference between these PLE maxima corresponds to the energy of the spin-orbit splitting in the iodine atom ground state. This leads to the conclusion that the negatively charged fragments responsible for the 550 and 590 nm PL bands contain iodide ions. Finally, our results show that the AgBr emulsion PL consists not only of microcrystal PL but also of the emission due to impurity centers formed in gelatin during synthesis of AgBr microcrystals.

Cooperative sensitization by reduction and chemical sensitization in AgX core–shell emulsions

Cubic core–shell AgBr and AgBrI emulsions prepared by the twice emulsified method were used to observe the cooperative sensitization of reduction sensitization in the core and sulfur-plus-gold sensitization on the surface of core–shell grains through a space separation of different sensitizing centres by a AgBr shelled layer. The results showed: (1) that core–shell emulsions doped by Ag2 centres in cores reduced by DMAB exhibited a remarkable increase in sensitivity relative to the corresponding undoped emulsions; (2) that I− ions in AgBrI grains did not affect the sensitization of internal Ag2 centres, but were beneficial to the inhibition of fog density; (3) cooperative sensitization by the internal reduced Ag2 and the surface S+Au sensitizations was considered to result from two different mechanisms, i.e. trapping holes by the former and concentrating electrons by the latter, both of which were beneficial to the efficiency of latent image formation.

Characterization of Various Development Centers in Silver Halide Photography

In order to collectively study the factors influencing the developability of centers, the in situ measurement and analysis of the rate of development was made for various latent image centers and fog centers on AgBr grains with a variation of the kind of chemical sensitizations. The developability of these centers was analyzed from the viewpoints that the electron transfer from a developer to the electron-accepting level of a center should initiate the development, and that the height of the electron-accepting level of a center should be related to its size, chemical composition, band structure, the parity of the number of valence electrons in it, and the site for its formation. It was confirmed that the smallest developable center in AgBr emulsions was a fog center composed of two Au atoms while the smallest latent image centers in the emulsions with and without gold sensitization were Ag 2 Au and Ag 4 , respectively. The developabilities of these smallest centers were much smaller than those of larger ones. The developability of a center with a forbidden band as exemplified by Ag 2 S (i.e., a fog center in a sulfur sensitized emulsion) was so small that several hundreds of nanoclusters per grain were needed to initiate the development of the grain.

Electron and hole conductivities of silver halide emulsions

The electrical properties of unexposed silver halide emulsion were studied by applying Wagner polarization. The experiments proved that a few free electrons and holes existed in the unexposed silver halide emulsion microcrystals. These factors are essential for the formation of fog centres, and there were some relationships between the fog centre formation and the electrical properties. The changes in electron conductivity indicated the intrinsic factors of fog formation in AgBr emulsions. The changes in hole conductivity revealed the capability of iodide ion, used as a crystal conditional agent, to trap holes. When shallow electron-trap dopant was added to the silver halide crystals, the electron conductivity of the emulsion increased, while the hole conductivity decreased.

Gold–sulphide versus sulphide centres on (111) AgBr surfaces: characterization and mechanism

Octahedral core–shell AgBr emulsions sensitized by sulphur-plus-gold with gold added at 40°C either before or after sulphur sensitization were prepared and studied. The core emulsion was sensitized with a low level of dimethylamineborane (DMAB), and it enhanced the intrinsic sensitivity and long-wavelength sensitivity of the emulsion with an unsensitized shell. Oversensitization was observed for a high gold level in sulphur-plus-gold sensitization for both types of gold addition. The electronic effect of gold is small in these emulsions. Sulphur-plus-gold sensitization increases the long-wavelength sensitivity over sulphur-only sensitization, but generally more so for gold added before sulphur sensitization. To explain the enhancement of the long-wavelength sensitivity of the sulphur-plus-gold sensitization over sulphur sensitization, it is proposed that the energy level of the trapped electron in silver–gold–sulphide centres is slightly higher than in silver–sulphide centres. The dependence of long-wavelength sensitivity on the type of gold addition is explained by proposing that gold ions have to overcome an energy barrier to incorporate into the silver–sulphide centres. Gold ions decrease the long-wavelength sensitivity in gold-only sensitization, which is suggested to be due to a reaction with surface impurities or gelatin components that lead to the long-wavelength response in the unsensitized emulsion.

Specific Photographic and Luminescent Properties of Sulfur + Gold–Sensitized Silver Halide Emulsions

It was found that the introduction of univalent gold ions at the initial step of sulfur sensitization could lead to a dramatic fall in the light sensitivity (S) and a considerable increase in the intensity of low-temperature (Т = 77 K) luminescence (I) of silver sulfide clusters produced by sensitization. An increase in the hold time was accompanied by an increase in S and a decrease in I. The fall in S is associated with the oxidation of the silver moiety in (Ag2S)pAg+k or (Ag2S)qAg0n (q > p) clusters, which are light sensitivity centers. AgBr(I) emulsions subjected to sulfur + gold-sensitization exhibited a flash of IR-excited green luminescence from paired iodine centers. The appearance of this flash is due to the generation of deep electron traps by sulfur–gold sensitization.

Latent-image formation in tabular AgBr grains: experimental studies

Five tabular-grain AgBr emulsions of varying grain thickness were studied. Two were chemically sensitized in the presence of a blue spectral sensitizing dye, whereas the other three were chemically sensitized in the presence of a green spectral sensitizing dye. A companion set of emulsions chemically sensitized in the absence of dye was also prepared. Internal image development of the unsensitized emulsions showed substantial internal image in one emulsion, but minor amounts in the other emulsions. After chemical sensitization, there was no detectable internal image in any of the emulsions. Reciprocity failure data from 10−4 to 103 s showed that the emulsions sensitized in the presence of dye had little if any high-irradiance reciprocity failure, suggesting the minimum developable size of the latent image was three atoms for the development conditions used. Low-irradiance reciprocity failure commenced at 0.1–1 s. Long wavelength sensitivity studies showed that the chemical sensitization generally enhanced the sensitivity of three spectral regions in the emulsions sensitized in the absence of dye—550, 650 and 750 nm. These spectral regions are suggested to coincide with three distinct states of the sensitizer centres. Data for the emulsions chemically sensitized in the presence of dye were limited owing to the interference by dye absorption. The temperature dependence of the long wavelength sensitivity showed the activation energy for this process increased as the wavelength increased. Quantum sensitivity measurements were also made at the midpoint of the D−logE curve using 0.1 s exposures. Neglecting the polydisperse nature of these emulsions, values were 10–19 absorbed photons/grain for 400-nm exposures and 13–27 absorbed photons/grain for spectral exposures. An energy-level diagram was constructed for the emulsions sensitized in the absence of dye using their measured activation energies and the photon energies of the three spectral regions. The 550 centre is most likely a single-sulphide or single-selenide centre, with an unknown gold content and provides a shallow electron trap (0.1 eV maximum depth). The compositions of the 650 and 750 centres are most likely multiple sulphide or selenide or sulphide–selenide with unknown gold content. They provide deeper electron traps of depth 0.225–0.425 eV (650 centre) and 0.45–0.65 (750 centre), with the 650 centre probably the dominant of the two in terms of concentration.

Investigation of photoelectron temporal characteristics in silver halide microcrystals using the microwave absorption technique

The free photoelectron lifetime reflects to a large extent the latent image formation efficiency and sensitivity of silver halide material. The microwave absorption dielectric-spectrum technique enables measurement of the photoelectron decay process of silver halide emulsion exposed to 35ps laser pulse. For T-grain AgBr emulsion, the relationship between exciting energy and photoelectron action has been obtained and the influence of iodide dopants on photoelectron lifetime was measured and analysed. The photoelectron lifetime of dye-sensitized AgBr emulsion with tabular grains is shorter than that with cubic grains and the latent image formation efficiency of the former is higher than the latter.

Electronic Properties of Chemically Produced Silver Clusters: Photobleaching Studies

Chemically produced silver clusters lead to a 476 nm peak in the diffuse reflectance spectra (DRS) of AgBr emulsions. Earlier photobleaching studies have shown that this peak can be resolved into two component peaks—one at 474 nm which photobleaches, and a less intense one at 482 nm that does not. The 474 nm peak has been assigned to hole removing silver clusters. This interpretation has been questioned since photoproduced silver clusters, which are obviously electron trapping, are also known to photobleach (solarization). This possibility was examined with photoproduced silver clusters and photobleach conditions which were identical to those used for the earlier photobleach study. Such clusters are found to photobleach, but not to the extent that would explain the observed photobleaching of the 474 nm DRS peak. In the presence of a modest amount of hole removing silver clusters provided by reduction sensitization, the photoproduced silver clusters underwent minimal photobleaching. These results support the earlier assignment of the 474 nm DRS peak to hole removing silver clusters.

Central events in the interactions of 28Si and 32S with heavy emulsion targets

Data on the multiplicity of secondaries in central events of 28Si (14.6 AGeV) and 32S (3.7 AGeV) interactions with AgBr emulsion nuclei have been compiled and studied. The dependence of the multiplicities of the outgoing charged stripping particles on the number of interacting nucleons and therefore on the impact parameter, as indicated by the target size, and consequently, on the degree of centrality is investigated. The resultant multiplicity distribution of the produced pions for each studied case is fitted by both Negative Binomial (NB) and Poisson distributions. The NB distribution is valid for most of the considered cases. The transparency of the target for a projectile was found to become more pronounced as the incident energy increased.

Electronic properties of chemically produced silver clusters: grain morphology studies

The electronic properties of silver clusters formed on the surface of reduction- sensitized octahedral and cubic AgBr emulsions were studied. Prior to sensitization with dimethylamineborane, SnCl2 or high pH, these emulsions had the same efficiency. The results suggest that the octahedral emulsion has more potential to achieve a higher maximum speed increase. This difference may be due to fewer available sites for silver cluster formation on cubic surfaces. Gelatin concentration studies showed that the gelatin and/or impurities do play a role in silver cluster formation by high pH treatment. The precise role of OH− is uncertain.

Dopant boosts AgBr emulsion photosensitivity

RETURN TO ISSUEPREVNewsNEXTDopant boosts AgBr emulsion photosensitivityMICHAEL FREEMANTLECite this: Chem. Eng. News 2000, 78, 1, 8Publication Date (Print):January 3, 2000Publication History Published online12 November 2010Published inissue 3 January 2000https://doi.org/10.1021/cen-v078n001.p008Copyright © 2000 AMERICAN CHEMICAL SOCIETYArticle Views11Altmetric-Citations-LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (170 KB) SUBJECTS:Emulsions,Halogens,Inorganic compounds,Silver Get e-Alerts

The Effects of Iodide Addition on Fog Characteristics of Cubic Silver Bromide Grains

Dependence of fog on chemical sensitization and iodide amount in cubic AgBr emulsions has been studied. Similar fog curve shapes were obtained from the iodide-covered AgBr emulsions by varying the iodide amount and the sulfur-sensitized AgBr emulsions by varying the sulfur amount. Subsequent gold sensitization of the two kinds of emulsions produces two fog peaks in the curves with varying the iodide or sulfur amount. The surface properties of the emulsion grains have been discussed with reference to fog formation. The origin of fog is attributed to the reactivity difference between the chemical site and the bulk crystal surface. The reactivity sequences of different chemical sites were derived: Ag2S > AgI > AgBr > AgCl and Aun > Agn, etc. Direct electron transfer development (DETD) and indirect electron transfer development (IETD) were supposed to be the two processes in development. Based on the proposed mechanisms, the main experimental results were successfully explained with a distribution model of chemical impurities at the cubic AgBr grain surface.

Crystal Habit and Rounding of Cubic Silver Bromide Grains

The results of two analytical procedures, viz., percent cubicity by dye adsorption and supersphere roundness index, Q , by electron image analysis (electron microscopy) were compared for a series of cubic AgBr emulsions. A linear, least square, correlation, % cubicity = -110.7 Q + 99.96, was obtained in the range 0.25 < Q < 0.65. The zwitterionic dye, 3-ethyl, 3'-(3-sulfo-butyl)-9- methyl-thiacarbocyanine, as used in the cubicity test, adsorbs on rounded AgBr cubes either as single molecules or as J-aggregates.When cubes are slightly or moderately rounded, the demarcation of these two modes of adsorption can be identified with a “tilt” of the grain surface between 9° and 13°: only small deviations from the {100} crystal habit suffice to cause the dye to adsorb as J-aggregates.