Sulphur Sensitization Research Articles

An Analysis of Sulfur Sensitization Centers and Fog Centers by Applying Diffuse Reflectance Spectroscopy to Thick Emulsion Layers

An Analysis of Sulfur Sensitization Centers and Fog Centers by Applying Diffuse Reflectance Spectroscopy to Thick Emulsion Layers

Laser remote sensing of sulfur dioxide and ozone with the mobile differential absorption lidar ARGOS

The paper describes the optimization of the wavelength pair to be used in differential absorption lidar measurements of tropospheric ozone. Along with the usual requirements for optimum lidar performance, aerosol and aerosol gradient effects and sulfur dioxide cross sensitivity have been given special attention. For the measurement and reference, laser-beam wavelengths of 280.91 and 282.72 nm are proposed. Ozone lidar verification measurements with a UV photometric analyzer show excellent agreement and confirm the theoretical finding that ozone concentration uncertainties due to aerosol effects are insignificant under visibility conditions like those prevailing on a warm summer day directly above a deciduous-coniferous mixed forest canopy. The lidar used is described in some detail, and a few examples of measured gas distributions are presented.

Luminescence of quantum-dimensional centers with spatially ordered molecules of organic compounds adsorbed on their surfaces

A dimensional effect in the luminescence of a narrow-band silver sulfide semiconductor (with the width of the forbidden band E{sub g} = 0.9 eV) was discovered in 1977, when a luminescent method was used to study the nature and functions of the centers appearing as a result of sulfur sensitization of halogen-silver photographic emulsions. As is known, during the indicated sensitization, certain sulfur-containing compounds (usually, sodium thiosulfate) are introduced into a melted emulsion containing microcrystals of silver halide, thus promoting an increase in the photosensitivity of the emulsion layers. The reason for the observed increase in photosensitivity is the fact that during the interaction between sulfur-containing compounds and silver halide silver-sulfide centers arise on the surface of the emulsion microcrystals, which serve as deep traps for electrons and therefore determine the possibility for silver centers of latent image to be formed near them by a two-stage electron-ion mechanism. Measurement of the low-temperature (T = 77 K) luminescence spectra of different photographic emulsions containing AgBr, AgBr (I), or AgCl microcrystals made it possible to establish that the introduction of sulfur sensitizers (sodium thiosulfate or thiourea) into emulsion to increase its photosensitivity is accompanied by the appearance of new luminescence bands inmore » the near IR spectral region.« less

Study of Sulphur Sensitization Products on the Surface of Tabular Grains of Silver Halide Emulsions by Means of Analytical Electron Microscopy and Image Analysis

AbstractFormation of Ag2S specks on the surface of uniform AgBr and core(AgBr)-shell (AgBr0,96l0.04) tabular emulsion grains was investigated bp means of analytical electron microscopy and quantitative image analysis. Sulphide nucleation in the course of ripening was found to proceed mainly on the defects of the network of stacking faults and twinning dislocations on the (111) faces of the tabular emulsion grains, where sulphide specks combined to form fractal aggregates. The elemental composition of sulphide specks was identified by energy dispersive X-ray emission spectrometry. Detectable mass of the speck with size 4 nm was 2.5x10-19 g with error about 33%. The extent of Ag2S aggregation decreased after iodide incorporation into the crystal shell. The mass fractal dimension of sulphide aggregates characterizing self-similarity of a randomly chosen population of aggregates after 150 minutes of ripening was estimated as 1.49 ±0.07 for the uniform and 1,39±D.07 for the core-shell tabular grains respective...

MICROANALYSIS OF HUMAN NAILS BY PIXE MEASUREMENT USING HEAVY ION MICROPROBES

Human nails were analyzed by PIXE measurements using focused 3MeV Si2+ and 2MeV proton beams. It was found that the 3MeV Si2+ ions have a higher sensitivity for sodium and aluminium, on the other hand, 2MeV protons have a higher sensitivity for sulfur, potassium and calcium in nails. By using 3MeV Si2+ microprobe, it was observed that the sodium is distributed uniformly with some depletion areas and that aluminium segregates in grains. It shows an advantage of a heavy ion microprobe over a proton microprobe.

臭化銀粒子上での硫黄，金＋硫黄増感核の形成過程

臭化銀粒子上での硫黄，金＋硫黄増感核の形成過程

Effect of Sulphur Sensitization on the Delayed Formation of Latent Image Specks

AbstractThe phenomenon of the delayed formation of latent image specks in sulphur sensitized emulsions with cubic and octahedral grains was studied. The degree of delayed formation changed only a little with sensitization level and then increased slightly at the highest level, while sensitivity increased gradually at first and then decreased. Development rate measurements revealed that the degree of dispersion of the silver specks increased with sensitization level. Conditions where the dispersion was large did not enhance the delayed formation process. The rate of delayed formation was measured and the kinetics are discussed. The rate constant at the optimum exposure region was decreased by sulphur sensitization but then increased at the highest sensitization level. The rate constant in the low exposure region did not change with level of sensitization. The product of the numbers of latent sub-image specks and single silver atom species was estimated from the rate constants. It decreased with sensitizati...

写真科学研究会 "硫黄増感を考える" より

写真科学研究会 "硫黄増感を考える" より

Solid State Properties and Photographic Activity of Crystalline Ag2S- and (Ag, AU)2S-Specks at the Surface of Silver Halide Crystals

AbstractIn the present paper a model is proposed according to which the photographic activity of silver sulphide specks is explained on behalfof the solid state properties of crystalline cubic silver sulphide, Epitaxial deposit ion of the laller is cia imed to occur at least partly at the (III) faces of AgBr during chemical sensitization, The disorder of the cation sublallice in cubic silver sulphide is con idered to be the physical base of highly efficient electron trapping, whereas the high electronic conductivity is rcsponsible for its catalytic activity towards developmcnt (fog). Excess silvcr in non stoichiometric cubic silver sulphide plays a very important role in its photographic behaviour inclUding development kinetics, The model provides a coherent explanation of a great number of experimental facts including the effects introduced by gold ions during sulphur sensitization.

A Study of Effects of Sulfur Sensitization and a Cyanine Dye upon Physical Properties of Cubic Silver Bromide Emulsion Grains

A Study of Effects of Sulfur Sensitization and a Cyanine Dye upon Physical Properties of Cubic Silver Bromide Emulsion Grains

Sulfur Sensitization of Large Crystals of AgCl Doped with Sulfur in the Melt

Sulfur Sensitization of Large Crystals of AgCl Doped with Sulfur in the Melt

Drift mobility, electron trapping, and diffusion-limited kinetics in sulfur-sensitized AgBr microcrystals

The room-temperature photoelectron kinetics in 1.3- and 0.4-μm AgBr octahedral emulsion microcrystals have been investigated for time scales ranging from several nanoseconds to several microseconds after exposure. Two first-order decay processes were observed in 1.3-μm octahedra. The fast process is attributable to relatively shallow electron trapping that equilibrates with thermal detrapping after ∼60 nsec; the longer decay may involve ionic processes. Sulfur sensitization of the emulsion enhanced the fast electron decay rate (decay time=14 nsec). At higher levels of sulfur sensitization, the decay rate did not change with increasing sulfur levels; such behavior can indicate diffusion-limited surface trapping. A bulk-to-surface electron drift mobility of 0.8 cm2/V sec on nanosecond time scales has been deduced from these kinetics. Implications of the data to current theories of photographic image formation and sulfur sensitization are discussed.

Long range transport and transformation of anthropogenic pollutants observed in a PIXE-based monitoring network

An automated PIXE system was used to determine the elemental concentrations on particulate samples collected in a monitoring network of 40 remote sites covering 2 million square kilometers in the western United States from 1979 to 1981. PIXE's good sensitivity for sulfur permitted the measurement of this key element in a region of low concentrations. Sulfate particles comprise the major component of the fine mass and represent the largest threat to visibility in the region. Two cases of sulfate transport into the pristine, scenic areas of northern Arizona and southern Utah from sources around 600 km away are described: copper smelters to the south and urban center to the southwest. Evidence is also presented for the transport of sulfate to the northern Great Plains from industrial centers over 1000 km to the east. The simultaneous measurement of a wide range of elements by PIXE has permitted estimates of the conversion rates of SO 2 to sulfate in a clean, dry atmosphere. The most important result was the large variation between summer and winter. This indicates that SO 2 emissions in winter are much less serious than similar emissions in summer.

A Study of Mechanism of Sulfur Sensitization by Delayed Development Method

A Study of Mechanism of Sulfur Sensitization by Delayed Development Method

Quantitative comparison of direct and derivative AES with XPS of metal sulfides

AbstractIntegral area measurements of Auger intensities for various metal sulfides give comparable quantitative results to those obtained from derivative peak‐to‐peak heights. Highest precisions for sulfur sensitivity factors were obtained by: (a) intensity measurements involving integration of background‐subtracted N(E) lineshapes, (b) matrix corrections for electron mean free path and backscattering factor, (c) the use of XPS‐derived surface stoichiometries rather than assumed bulk stoichiometries for the metal sulfide standards. Despite the inherent inaccuracies of XPS quantitation, the XPS results help to correct for surface deviations from bulk stoichiometry owing to surface contamination, facile S surface oxidation, and preferential S loss usually observed during Ar+ sputter cleaning. The integral area Auger measurement techniques are particularly promising for electron‐beam sensitive materials which often cannot be characterized using high primary electron doses and conventional energy‐analyzer potential modulation differentiation.

A Grain-Size Series of Ammoniacal Emulsions and their Chemical Sensitization

Abstract. A grain size series of ammoniacal emulsions in the range 0-05 - lOµm2 mean grain projective area were prepared and then sensitized with sodium thiosulphate and sodium lelrachloroaurale. The grains were all of roughly spherical shape and exhibited a covering power that was inversely proportional to the mean linear grain dimension.The relation between the concentration of sulphur sensitizer, C, and the time of digestion, ts, for optimum speed is shown to take the form C0-8ts = constant for a single emulsion which when applied to ihe series as a whole implied that the concentration was inversely proportional to mean grain projective area. In the case of sulphur and gold sensitization these relations were much more complex.The level of sulphur sensitizer inherent to the gelatin was comparable to the levels added in the case of the emulsions of large grain size. When the total sulphur content was taken into consideration the ratio of sulphur to gold for optimum speed to light was approximately 9, reg...

A Computer Simulation of Latent Image Formation in Photographic Emulsion by a Monte Carlo Method

A digital computer analysis has been made of photon absorption, chemical sensitization and latent image distribution in a silver halide photographic emulsion, using the Bayer Hamilton model but with a different approach in treating the positive holes.In discussing the effect of sulphur sensitization it has been assumed that silver sulphide molecules can play a dual role in latent image formation, undergoing partial thermal dissociation to increase both the number of electron traps by providing more interstitial silver ions and that of positive hole traps by forming AgS-. The increased interstitial silver ion concentration has also been supposed to lead to an increase in the stability of single silver atoms. As to gold sensitization, it has been assumed that the main effect of gold is to enhance the developahility of latent image centres.Parameter values for simulation under various conditions of chemical sensitization have been calculated, based upon the above assumptions. The results have, as expected, reproduced in many respects those shown by experiments. Finally, a relation between the concentration of interstitial silver ions and the sulphur content in the emulsion grain has been derived.

On the Molecular Mechanism of Photographic Stabilization

Measurements of the kinetics of sulphur sensitization and its retardation by stabilizers support a mechanism for photographic stabilization in which the essential stabilization efTect involves the interaction of the stabilizer molecule with adsorbed sulphide rather than its precursor, the sulphur sensitizer. The effect of stabilizer on the sulphur sensitizer is incidental. It is proposed that the growth of sulphide specks is retarded by stabilizer. A mechanism is suggested in which the decreased capture rate of adsorbed sulphide by the growing speck is due to the formation of an equilibrium controlled ternary surface chelate complex of stabilizer and sulphide with a bridging metal (silver) ion. Because this complex is immobile the diffusion rate of the adsorbed sulphide is decreased. This modifies the speck size distribution, besides retarding the digestion rate, so that above a certain stabilizer quantity the sensitivity achieved is reduced. The structural requirement for stabilizers is that they arebi(or multi)-dentate nucleophilic ligands which can coordinate metal ion bonded to adsorbed sulphide as well as that on the crystal surface. Adsorption is only part of the requirement for stabilization. This treatment supports the model of sulphur sensitization by nucleation and growth of specks from adsorbed sulphide. The evidence described includes the consideration of compounds which are both stabilizers and sulphur sensitizers and sensitization kinetics measured with stabilizer added after as well as before sulphide formation.

Sulphur Sensitization: The Chemical Mechanism

The observed kinetic order of sulphur sensitization varies with sensitizer near a value of 0.5, in contrast to the first-order formation of sulphide. Several examples are illustrated. The kinetic difference between sulphide formation and sensitization is demonstrated by the complete kinetic separation of the processes in examples in which sensitization continues for as long as lOOmin from sulphide formed within 2min. Sensitization and sulphide speck growth must involve further processes following sulphide formation. A mechanism of nucleation and growth of specks via two-dimensional diffusion of adsorbed sulphide explains the kinetics of sulphur sensitization. This mechanism leads to a characteristic asymmetric speck size distribution in terms of which the photographic characteristics can be explained. The implications of the chemical mechanism of sulphur sensitization on the effect of varying digestion conditions on the number of specks and their size distribution are indicated.

Photographic Stabilization: A Kinetic Analysis

AbstractThe relative retardation. ∆ log t. of sulphur sensitization by photographic stabilisers is independent of sulphur sensitizer or sensitizer quantity It vanes with stabilizer and stabilizer quantity (B) according to t/to = 1 + KstabB, for tetraazaindense stabilizers. The digestion time with sensitizer (Q) in the presence of stabilizer (B) is given by 1t=cQm1+KstabB A quantitative kinetic analysis of stabilization with a number of stabilizers is made and a measure of stabilizer effectiveness, Kstab, can be determined for each stabilizer. The effect of substituents supports a stabilization mechanism involving coordination of silver by the tctraazaindene ring. A hypothetical chelated complex of stabilizer with adsorbed sulphide and coordinated silver (BAgS) at the surface is suggested. The observed kinetics of stabilization can be explained in terms of the formation of this complex in equilibrium.