Bromide Grains Research Articles

The microdosimetric one-hit detector model to calculate the energy response of radiographic films

In the present work, the microdosimetric one-hit detector model is evaluated by calculating the relative energy response of radiographic films. A small sample of typical radiographic films including the covering paper and the polyester base coated on by one emulsion layer is simulated by Geant4 toolkit. Silver bromide grains with the same cubical shape and dimensions of 1 μm randomly positioned in the emulsion are considered as the targets of the model. The relative energy response for eleven photon energies between 20 keV and 1.25 MeV is determined using the microdosimetric distributions of single energy deposition events in the grains. Calculations are performed for a few weight fractions of the silver bromide in the emulsion. The results show that for the weight fraction 13.3% of the silver bromide in the emulsion, calculated values of the relative energy response are in agreement with the experimental data within 20% difference. It can be concluded that the microdosimetric one-hit detector model satisfactorily predicts the energy response of radiographic films.

AgBr粒子による2, 2'-キノシアニンの吸着とその脱着

AgBr粒子による2, 2'-キノシアニンの吸着とその脱着

One-Step Through-Mask Electrodeposition of a Porous Structure Composed of Manganese Oxide Nanosheets

Potentiostatic electrolysis of a mixed aqueous solution of Bu4NBr (Bu = C4H9) and MnSO4 at +1.0 V (vs Ag/AgCl) on Pt electrode resulted in the oxidation of Br- and Mn2+ ions, which was followed by the deposition of insulating crystals of bromide salt of Bu4N+ and the subsequent formation of layered manganese oxide in the interstitial spaces of the bromide grains already grown. Dissolution of the bromide crystals with water left a well-dispersed porous texture composed of manganese oxide nanosheets.

Measurement of Crystallite Size of Method and Evaluation of Crystal Defects

The size of crystallites in mono-dispersed cubic silver bromide grains was measured by applying a powder X-ray diffraction method and Scherrer's equation to grains that were suspended in swollen gelatin layers. In order to evaluate the existence of defects, the measured crystallite size was compared to those measured by using a scanning electron microscope. In the case of the grains prepared by the controlled double jet method, the size of crystallites was equal to the edge length of the grains that had edge lengths smaller than 400 nm. This result proved the usefulness of the above-stated method for measuring the size of crystallites and also evaluating the presence of any crystal defect in each grain. In the case of the grains, which were precipitated in the presence of a sensitizing dye and potassium iodide, the size of crystallites was smaller than the edge's length, indicating the discontinuities in the grains introduced during the precipitation process.

One-step through-mask electrodeposition of a porous structure composed of manganese oxide nanosheets with electrocatalytic activity for oxygen reduction

Potentiostatic electrolysis of a mixed aqueous solution of Bu 4NBr and MnSO 4 at +1.0 V (vs. Ag/AgCl) on Pt electrode led to the oxidation of Br − and Mn 2+ ions. X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and X-ray diffraction (XRD) revealed that this anodic process was followed by the deposition of insulating crystals of bromide salt of Bu 4N + and the subsequent formation of layered manganese oxide in the interstitial spaces of the bromide grains already grown. Dissolution of the bromide crystals in water left a well-dispersed porous texture composed of manganese oxide nanosheets. The resulting MnO x -modified electrode exhibited a larger catalytic current for the reduction of oxygen in alkaline solution, compared to the bare Pt electrode.

Development of a holographic sensor for the detection of calcium dipicolinate—A sensitive biomarker for bacterial spores

An enzyme-linked holographic sensor for the detection of spore-specific calcium dipicolinate (Ca-DPA) is described. Small, acid-soluble spore proteins (SASPs) extracted from dormant spores are exploited as holographic matrices. Reflection holograms are incorporated into SASP films using a diffusion method for the distribution of ultra-fine silver bromide grains into pre-formed polymers, followed by holographic recording using a frequency doubled Nd:YAG (532 nm) laser. Changes in holographic diffraction intensity are used to characterise the structural integrity of SASP-based matrices in response to proteolytic attack by recombinant germination protease (GPRS), following activation with Ca-DPA; the holographic response manifests as an irreversible reduction in diffraction intensity due to progressive fringe removal caused by SASP degradation. This work demonstrates proof-of principle of a Ca-DPA-activated enzyme-linked holographic sensor, highlighting the potential of a system whereby Ca-DPA released from germinating spores may activate GPR in the vicinity of an SASP-based holographic matrix; such a sensor system presents a novel platform for the selective detection of bacterial spores with intrinsic signal amplification.

Holographic sensors for the detection of bacterial spores

Holographic sensors for the detection of Bacillus species spore germination and vegetative growth are described. Reflection holograms were fabricated using a diffusion method for the distribution of ultra-fine silver bromide grains into pre-formed polymer films, followed by holographic recording using a frequency doubled Nd:YAG (532 nm) laser. Changes in holographic replay wavelength or diffraction intensity were used to characterise the swelling behaviour or structural integrity of a range of holographic matrices in response to various extracellular products of bacterial spore germination and vegetative metabolism. Divalent metal ion-sensitive holograms containing a methacrylated analogue of nitrilotriacetic acid (NTA) as the chelating monomer were successfully used to monitor Ca 2+ ions released during B. subtilis spore germination in real-time, which was within minutes of sample addition; the holographic response manifested as a 16 nm blue-shift in diffraction wavelength over the progress of germination. Similarly, pH-sensitive holograms comprising methacrylic acid (MAA) as the ionisable monomer were responsive to changes in pH associated with early vegetative metabolism following germination of B. megaterium spores; a visually perceptible blue-shift in holographic replay wavelength of 75 nm was observed. Casein and starch-based holographic matrices, prepared by co-polymerisation of the appropriate substrate with acrylamide, were used to detect exo-enzymes released during later stages of B. megaterium and B. subtilis vegetative cell growth; holographic responses of both matrices were visible as a reduction in diffraction intensity due to progressive fringe disruption caused by enzymatic cleavage. The combined monitoring of various germination and growth events using the range of aforementioned holographic sensors provides a novel, comprehensive means for the detection of viable bacterial spores.

Crystallization of Silver Carboxylates from Sodium Carboxylate Mixtures

Silver carboxylates can be made by the reaction of silver nitrate and the corresponding sodium carboxylates. The length of the alkyl chain has a significant impact on the product behavior. In this study, 18, 20, and 22 carbon chains (stearate, arachidate, and behenate, respectively) have been selected. All three sodium carboxylates are very insoluble in water at room temperature. Solutions are obtained above the Krafft temperature, which precipitates lamellar crystals if cooled at the proper cooling rate. Depending on the chain length, metastable morphologies, such as vesicles and tiny fibers, can be seen consecutively before hexagonal plates form. The carboxylate with the shorter chain length reaches equilibrium more quickly. All three silver carboxylates also take on a lamellar structure. Small-angle X-ray scattering (SAXS) shows that the d spacing of the crystals increases as the chain length increases. Cryo-TEM illustrates that the crystallites are the result of micelle nucleation and micelle aggregation. In addition, the crystallization process in the presence of silver bromide nanocrystals has been investigated. In the initial stage, an epitaxial interface is formed between the silver carboxylate crystallites and the cubic silver bromide grains. Budlike and strandlike structures grow because of it. The consequent strand enclosure restrains the crystal growth, which reduces the size and changes the morphology of the crystals.

Room temperature synthesis of silver nanowires from tabular silver bromide crystals in the presence of gelatin

Long silver nanowires were synthesized at room temperature by a simple and fast process derived from the development of photographic films. A film consisting of an emulsion of tabular silver bromide grains in gelatin was treated with a photographic developer (4-(methylamino)phenol sulfate (metol), citric acid) in the presence of additional aqueous silver nitrate. The silver nanowires have lengths of more than 50 μm, some even more than 100 μm, and average diameters of about 80 nm. Approximately, 70% of the metallic silver formed in the reduction consists of silver nanowires. Selected area electron diffraction (SAED) results indicate that the silver nanowires grow along the [111] direction. It was found that the presence of gelatin, tabular silver bromide crystals and silver ions in solution are essential for the formation of the silver nanowires. The nanowires appear to originate from the edges of the silver bromide crystals. They were characterized by transmission electron microscopy (TEM), SAED, scanning electron microscopy (SEM), and powder X-ray diffraction (XRD).

A Study of Location of Latent Image Centers Formed on Sulfur-Sensitized Silver Bromide Grains

A Study of Location of Latent Image Centers Formed on Sulfur-Sensitized Silver Bromide Grains

Observation and Characterization of Sulfur Sensitization Centers Formed on Octahedral Silver Bromide Grains

We observed sulfur sensitization centers, which were formed on octahedral silver bromide grains in emulsions and decorated with silver clusters by means of an amplification treatment with a special physical developer. The concentration of the centers increased with increasing the amount of the sensitizer, and reached a plateau with the amount that gave the maximum sensitivity. The concentration of the centers, which gave the maximum sensitivity, was as many as 3200 per μm2, and the same as the concentration of fog centers formed with excessive amount of the sensitizer. The comparison of the concentration of the observed centers with the amount of silver sulfide formed by sulfur sensitization revealed that each sulfur sensitization center contained two sulfide ions in the emulsion with the maximum sensitivity. This result supported the idea that the sulfur sensitization centers were dimers of silver sulfide, as proposed by Keevert and Gokhale,1 Kanzaki and Tadakuma,2 and Tani.3

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.

Spectral Sensitization and Supersensitization of AgBr Nanocrystals Studied by Ultrafast Fluorescence Spectroscopy

Spectral sensitization and supersensitization of the silver bromide nanocrystals were studied by the femtosecond fluorescence up-conversion technique. An annihilation-free fluorescence from J-aggregates of the Dye 1 (3,3‘-disulfopropyl-5,5‘-dichloro-9-ethylthiacarbocyanine) adsorbed on the silver bromide nanocrystals (edge-to-edge distance from 40 to 900 nm) of different shapes (cubic and octahedral) was measured. Very fast nonexponential fluorescence decays were observed with a fast component from 0.4 to 2.5 ps, and an average decay time from 1.1 to 5.5 ps, depending on the type and size of AgBr grains. The average fluorescence decay time is several times longer on the cubic grains than that on the octahedral grains. Upon addition of a supersensitizer (SS) (3,3‘-disulfopropyl-9-ethyl-4,5,4‘,5‘-dibenzothiacarbocyanine), which is coadsorbed on the surface of silver bromide grains, the fluorescence decay became several times faster with a mean decay time of 0.60−1.3 ps. Different models of supersensitization were examined. The results were analyzed in the framework of the “hole-trapping” supersensitization model. Octahedral grains with different sizes were examined. The effective hole-trapping (electron transfer from SS to the excited J-aggregate) rate constant was found to be independent of the grain size and equal to ∼0.60 ps-1. The increase of the electron injection rate (from the excited J-aggregate to the AgBr conduction band) with the increase of the grain size is observed and a possible mechanism is discussed.

Estimation of Trap Depth of Sulfur Sensitization Centers by Analyzing Long-Wavelength Sensitivity in Sulfur-Sensitized Silver Bromide Grains. Part 2, Effect of Silver Halide Crystal Faces

Estimation of Trap Depth of Sulfur Sensitization Centers by Analyzing Long-Wavelength Sensitivity in Sulfur-Sensitized Silver Bromide Grains. Part 2, Effect of Silver Halide Crystal Faces

Mechanistic Studies of a New Nucleated Infectious Development System Using Pyridinium Salts

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 which is induced by the combination of a pyridinium salt and Metol-ascorbate developer. Treatment of internally chemically sensitized silver bromide core/shell emulsion by BNAH and redox buffer followed by development gave high internal fog density. It has been suggested in that the oxidation product of BNAH by redox buffer injects electrons into the conduction band of silver bromide grains, resulting in the formation of fog centers inside the grains. 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.

Silver clusters of photographic interest Part 5: formation of R centres and P centres by reduction sensitization and light absorption of silver bromide grains

A model of silver clusters with R centres as traps for positive holes and P centres as traps for photoelectrons in silver halide grains was proposed in this series of papers, and provided several subjects for future studies after discussions at several international meetings. Considerations and some experimental examinations on those subjects by use of fine silver bromide grains were made in this study. With the amount of dimethylamine borane (DMAB) used for reduction sensitization, the sensitivity of these grains increased through two steps, as reported in this series of papers. At the beginning of the first step, the radiowave photoconductivity with positive holes as carriers at room temperature began to decrease, while the microwave photoconductivity with photoelectrons as carriers at room temperature began to decrease at the beginning of the second step. Thus, these experiments could clearly confirm the formation of R centres and P centres by reduction sensitization. It was observed by applying electron microscopy to gelatinate shells of the grains that reduction sensitization led to the formation of many silver clusters per grain, being highly contrasted with latent image formation, which led to the formation of only one silver cluster per grain regardless of exposure, owing to the concentration principle. The above-slated silver cluster formation by reduction was therefore not based on the concentration principle, but on the proposed mechanism without contributions from a free electron or a single silver atom to the cluster formation.

A diffusion method for making silver bromide based holographic recording material

A simple diffusion method for the distribution of ultrafine silver bromide grains in pre-coated gelatin and customized polymeric films for holographic recording has been developed. The method involves two steps: immersion of the pre-formed film in a solution of a silver salt, followed by agitation of the film in a solution of a bromide salt containing sensitizing dye. Repetition of the operation on the same film with different sensitizing dyes in the bromide bath enables the production of film with a panchromatic response. Transmission electron microscopy reveals a grain structure very suitable for use in holography. A reflection hologram made by this method has a similar brightness under the same exposure and processing conditions to one made from a proprietary hologram recording material currently available.

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.

A Study of Location of Latent Image Centers Formed on Sulfur-Sensitized Silver Bromide Grains. Part 2

A Study of Location of Latent Image Centers Formed on Sulfur-Sensitized Silver Bromide Grains. Part 2

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.