Silver Bromide Emulsions Research Articles

Investigation of decay characteristics of photoelectrons in nanoparticales of cubic AgBr sensitized by NiS

NiS nanoparticales as a sensitizer is added to cubic silver bromide emulsion for the chemical sensitization. The decay curves of free photoelectrons and shallow-trapped electrons in the cubic silver bromide emulsion sensitized by NiS nanoparticales with the continuous increase of sensitization time are measured by the microwave absorption and dielectric spectrum techniques. The courses of decay of photoelectrons in the cubic silver bromide emulsion sensitized by NiS nanoparticales vis sensitization time is analyzed. The influence of electron traps in silver bromide microcrystals on the behavior of the photoelectrons' movement is discussed. The relationships between the effects of electron traps and the depth of traps with sensitization time are analyzed. By comparing the decay characteristics of the unsensitized and the sensitized samples, the optimum sensitization time under the present experimental conditions is 80 min.

Silver Clusters of Photographic Interest: Formation of Silver Clusters During Precipitation of Silver Bromide Emulsion Grains

The formation of silver clusters due to reduction of silver ions by gelatin during precipitation process of AgBr grains in emulsions was studied from the point of view that it should take place when the potential of the silver half-cell (EAg) was more positive than the potential of the gelatin half-cell (EGel) in a reaction solution. Although the sensitivities of the prepared emulsions were independent of EAg of the bulk reaction solutions, they increased with increasing pH values, and reached the sensitivities of the corresponding reduction sensitized emulsions and hydrogen hypersensitized ones. These results indicate that the formed clusters were reduction sensitization centers. It is proposed that silver cluster formation takes place, not in the bulk reaction medium, but in the region into which an aqueous solution of silver nitrate has been introduced for precipitation, since this is the only region where EAg is more positive than EGel in a reaction vessel.

Enhancement of Silver Nuclei Formation by Sulfur Sensitization Centers on Silver Bromide Grains

Heavy hydrogen hypersensitization formed P centers, which were silver nuclei acting as electron traps on octahedral silver bromide grains in coated emulsion layers. The number of P centers was evaluated by measuring the diffuse reflectance spectrum of a stack of 10 coated emulsion layers. Sulfur sensitization centers increased the rate of formation of P centers, and decreased its activation energy. The observed activation energies were 0.87 eV in a primitive emulsion and 0.52 eV in an excessively sulfur sensitized one. This result supports an idea that sulfur sensitization centers formed on silver bromide emulsion grains catalyze silver nuclei formation, and that this is one of the essential functions of sulfur sensitization centers.

The spectral sensitization properties of indolenium squarylium cyanine dyes in silver bromide emulsion

The spectral sensitization behaviour of a class of donor acceptor donor (D-A-D) molecules, bis(5-substitucnt-2,3,3,-trimethylindolenium-2-ylidcne) Squaraine (Sqel 8), has been inspected. In silver bromide tabular grain, all the dyes exhibited desensilization. The C-5 subslitucnt affects the desensitization efficiency to a large extent. Especially for the dye with the C-5 nitro group, an unexpectedly high desensitization efficiency is found. The dye aggregation properties in emulsion were determined. The high desensitization efficiency was attributed to an aggregation state, of which the dye-AgBr interaction is the most common. The sensitization mechanism was discussed and attributed to electron transfer.

Study on the Progress of Development of a Silver Bromide Emulsion by a Simulation of Developed Silver-Time Curves

Study on the Progress of Development of a Silver Bromide Emulsion by a Simulation of Developed Silver-Time Curves

A holographic sensor based on a rationally designed synthetic polymer.

A new silver halide-containing holographic recording material has been designed and developed specifically for holographic chemical sensors. The hologram enables very small volume changes to be measured in a polymer layer throughout which the hologram is located. The holographic film is based on a fine-grain silver bromide emulsion suspended in a poly(vinyl alcohol) matrix crosslinked with Cr(III) ions. Cross-linking gives the material sufficient spatial integrity to allow a holographic image to be recorded, while maintaining adequate porosity and elasticity of the polymer matrix for sensing applications. The new material has been characterized with respect to its response to pH and compared with a traditional gelatin holographic film. The response to some ions and small molecules typically found in analytical samples has also been measured. Functional groups introduced covalently into the poly(vinyl alcohol) matrix transform the base matrix into a pH-responsive polymer with predictable swelling properties and which can be further derivatized to incorporate specific ligands. A rationally designed holographic sensor for trypsin has been developed from chemically synthesized artificial polymers. A trypsin substrate, the poly(amino acid) poly(L-lysine), was incorporated into poly(vinyl alcohol) holograms to create a 'designed' holographic material which was degraded in a concentration-dependent manner by trypsin. Extensions of this approach to other hydrolytic enzymes are briefly discussed.

Desensitization Due to Enhancement of Dispersion of Image Centers by Dyes, III. Effect of Crystal Defects

In this series of investigations with a sulfur-sensitized cubic silver bromide emulsion with 9-methylthiacarbocyanine dye as a spectral sensitizer, we propose a new mechanism of dye desensitization according to which the enhancement of dispersion of image centers by cyanine dyes brings about a decrease in sensitivity. In the light of the fact that introduction of crystal defects into emulsion grains depressed the dispersion of image centers, a study was made of the dependence of the desensitization on the crystal defects introduced into the emulsion grains without causing any change in their size, shape, and halogen composition, effected by adding a solution of the dye during their growth process. The observation that the crystal defects actually depressed the desensitization strongly supports the proposed mechanism of dye desensitization.

Silver Clusters of Photographic Interest IV: Reduction Sensitization of Silver Chloride and Silver Bromide Emulsions

Digestion of AgBr emulsions with increasing amounts of reduction sensitizers achieved stepwise increase in sensitivity corresponding to the formation of two kinds of sensitization centers, designated R centers, acting as positive-hole traps, and P centers, acting as electron traps. It has been proposed that R and P centers are silver dimers formed at electrically neutral and positively charged surface sites on AgBr grains, respectively. The formation of P centers was depressed by addition of TAI and PMT, which are preferably adsorbed to positively charged surface sites on the grains, and enhanced by cyanine dyes, which are preferably adsorbed to negatively charged surface sites. Reduction sensitization of AgCl emulsions was less effective than that of AgBr emulsions in that the former brought about less increase in sensitivity and more increase in fog density than the latter with increasing amounts of sensitizers. Reduction sensitization of AgCl emulsions was significantly improved by digesting the emulsions for reduction sensitization in the presence of PMT and TAI. From the fact that the sensitivity increase of AgCl emulsions was not associated with a decrease in photoconductivity with photoelectrons as carriers and was not observed in the presence of hydrogen hypersensitization centers acting as positive-hole traps, it is considered that, in AgCl emulsions, reduction sensitization centers were solely R centers, while P centers acted as fog centers. The developability of P centers in AgCl emulsions was however very weak. It was found that R centers exhibited their absorption band, whose peak wavelength (420 nm) was close to that of the absorption band of Ag2 in rare gas (412 nm). This result supports the proposed model where an R center is a silver dimer at a neutral site that physically interacts with the surface of silver halide.

Mechanistic Studies of a New Nucleated Infectious Development System Using Pyridinium Salts: Nucleation of Silver Halide Grains by Dihydropyridines

Photographic properties of 1-benzyl-1,4-dihydronicotinamide (BNAH) are studied for better understanding of the mechanism of the production of high contrast by the infectious development induced by the combination of a pyridinium salt and Metol-ascorbate developer. Treatment of silver bromide emulsion or silver chlorobromo emulsion by BNAH and redox buffer followed by development gave high fog density. It has been suggested that the oxidation product of BNAH by redox buffer nucleates silver halide grains and makes them developable. Results support the hypothesis that dihydropyridine works as an intermediate in the production of high contrast by the infectious development in the presence of a pyridinium salt.

Comprehensive Model for Sulfur Sensitization (2): Characterization of Sulfur Sensitization Centers and Fog Centers

In the previous work, the present author proposed a comprehensive model for sulfur sensitization according to which monomers and dimers of substitutional sulfide ions on silver halides are sulfur sensitization centers acting as positive hole traps and electron traps, respectively, while silver sulfide clusters are fog centers. The model was supported by characterizing those centers on octahedral and cubic silver bromide emulsion grains with equivalent circular diameter of 0.2 μm. The difference in oxidation potential and absorption spectrum between sulfur sensitization centers and fog centers was distinctive enough to be ascribed not merely to the difference in size, but also to the difference in the state of the sulfide ions. As many as 500 silver sulfide clusters (i.e, fog centers)/grain (i.e, 2400/μm2) were observed by an electron microscope in slightly fogged emulsions, indicating that the developability of each cluster was very low. The above concentration of fog centers was independent of the amount of silver sulfide formed among variously fogged emulsions, suggesting that sulfur sensitization centers as well as fog centers were formed at surface sites, where sulfide ions were stable and liable to be coagulated. The belief is that low developability of silver sulfide clusters makes it possible to achieve high sensitivity and stability without fog formation in sulfur-sensitized emulsions.

Silver Clusters of Photographic Interest (2): A New Model for R and P Centers

Reduction sensitization with various sensitizers, silver digestion, and hydrogen hypersensitization were applied to octahedral and cubic silver bromide emulsion grains to form P centers, identified by the observation of sensitivity increase and photoconductivity decrease caused by the centers, and absorption band characteristic of the centers. It was found that P centers decreased the ionic conductivity of the grains, which was proportional to the concentration of interstitial silver ions. By taking into account the fact that silver ions at kink sites are in equilibrium with interstitial silver ions, we propose that a P center was formed adjacent to a silver ion at a kink site and prevented it from going into an interstitial position in an emulsion grain. It is further proposed that a P center of a silver dimer is not merely Ag2 in adjacent to Ag+ at a kink site, but a center as expressed by Ag3+. The new model for an R center and a P center was successfully applied to the explanation of the formation, property, and behavior of silver clusters of photographic interest.

Preparation of Silver Bromide Emulsion Grains by Belousov-Zhabotinsky Reaction on Continuous Addition of Silver Nitrate Solution

In the Belousov-Zhabotinsky reaction system bromide ions are generated periodically. When AgNO3 solution was added to this system, AgBr grains were prepared and the periodical pBr oscillation was sustained during addition of the solution. In previous research we added drops of AgNO3 solution synchronously to the pBr oscillation. This time we added AgNO3 solution by continuous flow and observed the pAg (pBr) oscillation and grain shapes. The periodical pAg oscillation was also sustained. At some addition rates, dendrite grains with four, five, six, or eight long branches were formed. In some grains, secondary nucleation took place on the surface of branches and many warts aligned. We believe that the grain corners grew preferentially.

Preparation of Silver Bromide Emulsion Grains by the Belousov-Zhabotinsky reaction

Preparation of Silver Bromide Emulsion Grains by the Belousov-Zhabotinsky reaction

Quantum Efficiency Measurement for the Photo-induced Bleaching of Latent Image Centers by Positive Holes in Silver Bromide Emulsion

Quantum Efficiency Measurement for the Photo-induced Bleaching of Latent Image Centers by Positive Holes in Silver Bromide Emulsion

Atomic force microscopy studies of silver bromide emulsion grains

Atomic force microscopy studies of silver bromide emulsion grains

Sub-Image Centres in an AgBr Emulsion: Creation by Oxidation; Stability

AbstractWe attempted to determine the relative stabilities of latent image and sub-image centres in a sulphur- plus-gold-sensitized silver bromide emulsion by the Reinders technique in which exposed films are bathed in solutions containing both ferrous and ferric ions. The latent image centres were detected by development without latensification, whereas sub- image centres were detected by either gold or light latensification prior to development. Because oxidation of latent image centres by the ferric/ferrous solution creates sub-image centres simultaneously with the destruction of some sub-image centres, a new accounting of the net change in fraction of grains containing only sub-image centres is postulated. Within the experimental uncertainties of our results, we cannot conclude that sub-image centres are more stable than latent image centres.

Characteristic, Reciprocity and Intermittency Curves Obtained with Very Short Pulses Supplied by a Laser System

AbstractAn apparatus including an argon ion laser and various light modulators was built. This apparatus permits exposures to be made with one light pulse of a duration comprised between 10-8 s and 5 × 10-6 s or with a selected number of periodic short light pulses with a time interval between pulses comprised between 10-7 s and 5 × 10-6 s. The apparatus was used to determine the characteristic, reciprocity and intermittency curves of various unsensitized and chemically- sensitized silver bromide emulsions with grains of different crystal habits. The addition of tetraazain- dene to these emulsions was also studied. The results are shown and some conclusions are put forward.

High resolution electron microscopic study of silver sulfide microcrystals formed on silver bromide emulsion grains

Silver sulfide specks formed on the (111) plane of AgBr are examined by high resolution electron microscopy and the relationships in atom arrangement at their interface are revealed on the basis of the lattice images observed for the silver sulfide specks as well as their orientation relative to the direction of AgBr crystal axis. Silver sulfide are in contact with AgBr (111) plane with one of the four different planes, (100), (102), (104), and (103). In every interfaces, the b-axis of the microcrystal of silver sulfide is parallel with the [112] axis of AgBr. The atom arrangements of both the crystals are, similar to each other at the interface and the lattice misfits between them are so small that the formation of the silver sulfide specks is considered to occur epitaxially on the AgBr (111) plane. Silbersulfidflecken auf (111)-Ebenen von AgBr werden mittels hochauflosender Elektronenmikroskopie untersucht und die Beziehungen der Atomanordnung an ihren Grenzflachen werden anhand der fur Silbersulfidflecken beobachteten Gitterdiagramme sowie deren Orientierung bezuglich der AgBr-Kristallachscnrichtungen gefunden. Silbersulfid befindet sich mit der AgBr (111)-Ebene und einer der vier verschiedenen Ebenen (100), (102), (104) und (103) in Kontakt. In jeder der Grenzflachen ist die b-Achse des Silbersulfid-Mikrokristalls parallel zur [112]-Achse von AgBr. Die Atomanordnungen beider Kristalle sind einander ahnlich an der Grenzflache und die Gitterfehlanpassung zwischen ihnen ist so gering, das angenommen wird, das die Bildung der Silbersulfidflecken epitaktisch auf der AgBr (111)-Ebene erfolgt.

Photographic Action of Ph(II)-EDTA

AbstractBy turbidimetric and electron-microscopic methods the influence of Pb(II)-EDTA on the physical ripening of silver bromide and silver chloride emulsions, obtained in excess of halide or silver ions, was investigated. The effect of Pb(II)- EDTA on the photosensitivity, S, the contrast, and the maximum density, Dm, was also studied. The reagent was found to perform as an active sensitizer when introduced at a concentration of 2 × 10-4 M prior to precipitation.Investigations on hypersensitization were carried out by a known method for hypersensitization with Pb(II)-EDTA. It was also shown that Pb(II)-EDTA can be applied in practice as a hypersensitizer as well as a sensitizer.

Comparative Study of the Sensitivity Specks Formed During the Ripening of Silver Chloride Relative to Silver Bromide with Gold-198 and Gold-198 Plus Sulphur-35*†

AbstractBy means of radioactive tracers 35S and 198Au a comparative study of the composition of the sensitivity specks formed during the ripening of silver chloride and silver bromide emulsions with equal grain size (a = 0.2 //m) was made and related to their photographic response. The sensitizers used were gold chloride (198Au) and gold chloride combined with sodium thiosulphate (35Sext).A washing technique was required to differentiate between gold in a more or less soluble state adsorbed on the emulsion grains during ripening. A 10-4 M sodium sulphite solution was found to be useful. This gold-complexing solution was able to desorb gold ions from the grain surface, leaving undesorbed the presumed gold sulphide, silver gold sulphide, gold or gold oxide specks.The following conclusions could be drawn:(1) The ripening of silver chloride and silver bromide emulsions with gold chloride results in the formation of identical amounts of non-desorbable gold, but corresponding with higher fog values for the AgCI...