Exposure Addition Effects and Their Terminology

Studies of the increases in overall sensitivity, in red light sensitivity, and in silver sulphide during sulphur sensitization of a photographic emulsion have been carried out. They suggest that there are two quite distinct mechanisms by which the silver sulphide can give rise to increase of light sensitivity.     

The Cluster Mechanism in Sulphur Sensitization

. The production of silver sulphide on two cubic silver halide emulsions has been followed using sodium thiosulphate sensitizer with the outer sulphur atom labelled ³⁵S. It is found that the position of sensitizer adsorption on the silver halide grain has an effect upon its rate of breakdown to yield silver sulphide. The concentration of sensitizer added to the emulsion affects the photographic response. At optimum sensitivity the quantity of silver sulphide present depends upon the initial sensitizer level, the silver sulphide becoming less efficient with increasing sensitizer. Clusters of silver sulphide are probably produced as a result of preferential adsorption of sensitizer by silver sulphide.     

Adsorption of Photographic Sulphur Sensitizers to Silver Bromide and Silver Sulphide

Heats of adsorption of thiosulphate, thiosulphatoargentate and p-toluenethiosulphonate to silver bromide, silver bromo"dide, silver chloride and silver sulphide were measured using a slow microcalorimeter. The results did not confirm previous evidence for the cluster mechanism for silver sulphide formation during sulphur sensitization. The possibility of this model was discussed. Heats of adsorption of silver and sulphide ions were also measured.     

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.     

The Behaviour of Large Silver Bromide Crystals on Exposure and Development

The behaviour of large silver-bromide crystals (approximately 5-20_μ in diameter) on exposure and development has been studied. The principal characteristic curves, analogous to those of silver bromide sols, have been obtained, which show that these crystals behave photographically like sols. Since the grain sizes of sols and large crystals span the range normally investigated in photographic research, it is considered that the behaviour of sols and crystals is characteristic of silver-bromide crystals in general, any quantitative variations being due to differences in surface-to-volume ratio. The suggestion that spontaneous sensitization by gelatin is due to reduction is rejected. The notion that silver sulphide functions primarily as a bromine (positive hole) acceptor is not confirmed.     

Thiosulphate Reactions at the Surface of Developed Silver

The detection of silver sulphide in processed photographic images has been attributed to the silver adsorbing a monomolecular layer of thiosulphate ions, which react to form silver sulphide when the silver image is bleached in acid dichromate solution. By studying adsorption with thiosulphate having the inner sulphur atom labelled, it has now been shown that most of the thiosulphate ions believed to be adsorbed by the silver image had already suffered rupture at the sulphur-sulphur bond, even before the bleaching step. Treatment of the silver image with a cyanide solution was relatively ineffective in removing the adsorbed sulphur, and it is thus doubtful whether it can be considered to be present in the form of silver sulphide.     

Industrial Radiology,Past, Present and Future

A new model for sulphur sensitization has been developed. It is based on the surface double layer which has previously been shown to occur in silver halides. The charge present in this double layer causes the energy bands to bend downward or upward according to whether silver sulphide is present on the crystal surface or not. Where silver sulphide is not in contact with the surface the bands bend upward, thus impeding the motion of photo-electrons towards the surface. Conversely in points where silver sulphide is adsorbed onto the Srystal surface, the bands bend downwards, thus yielding an attracting force driving the photoelectron towards the silver sulphide speck. The bending of the bands may have the additional effect of increasing the lifetime of electrons in traps which are near to a silver sulphide Speck, thus holding the trapped electron for a long enough time as to allow the “ionic step” to take place. Our experimental results as well as others reported in the literature are explained with this model.     

The Eleventh Renwick Memorial Lecture: The Nature Of Photographic Sensitivity

This paper reviews the work on photographic sensitivity which has been carried out by the author and his colleagues, and presents the conclusions which have been drawn from it. The earlier concept of the sensitivity speck has been replaced by that of the sensitivity centre. The sensitivity speck was assumed to consist of silver or of silver sulphide and to have the function of concentrating silver atoms: the sensitivity centre is a region of enhanced reactivity associated with a crystal imperfection. The conclusion is now that the principal function of the silver sulphide is to trap positive holes and thus to prevent the regression of latent image specks. The theory of dye sensitization has been extended and a number of new features introduced. According to present ideas, the latent image is formed in two stages. In the primary stage, electrons and positive holes are liberated and the positive holes are trapped with the production of interstitial silver ions. In the secondary stage these combine with the conduction electrons to form first latent pre-image specks, then latent sub-image specks, and finally stable latent image specks. A discussion of reciprocity failure is given. The new approach to the theory of photographic sensitivity, in which the role of kink sites Is emphasized throughout, leads to the enunciation of four basic principles which must be satisfied by any theory of the formation of the latent image. Of these, only the Gurney-Mott principle has previously been recognized.     

About the Nature and the Role of the Sensitivity Speck Formed during Gold Ripening

After a critical survey of recent literature about the present state of the mechanism of gold sensitization, there are presented new experimental results obtained by tracer techniques using 1,8Au, which lead us to believe that during a gold + sulphur ripening in addition to gold sulphide or silver gold sulphide metallic gold specks are formed. These specks are to be considered as real sensitivity specks.

It seems likely that the function of gold in latent image formation is more related to better catalytic properties and better stability of the latent silver specks than to an increasing efficiency of the electron trapping at the grain surface.     

新型的2-硫代苯并咪唑磺酰亚胺盐类化合物在氯化银乳剂中的增感

通过染料的极谱分析以及在乳剂中的应用试验,对文题化合物与５－甲基－７－羟基－１．３,４－三氮吲哚利嗪、氧－硫海因二甲川份菁染料进行研究。结果化合物在乳剂中使用具有一定的增感和与防灰雾作用。其增感作用与该类化合物的极谱半波氧化电人闰值有关半波氧化电值低,光谱增感效果好。     

Analytical Evidence Bearing on the Halogen Acceptor Theories of Sulphur Sensitization

It is shown analytically that when a sulphur-sensitized emulsion is exposed, silver sulphide is destroyed by the halogen produced during the exposure. The amount destroyed is dependent upon the time of exposure. If, however, other halogen acceptors are present during the exposure, they will preferentially accept the halogen. As these halogen acceptors have no effect on the sensitivity of either the sensitized or the unsensitized emulsion, it is concluded that the analytical evidence is not compatible with theories of sulphur sensitization in which the primary function of the silver sulphide is considered to be one of halogen acceptance.     

Book Review

By tracer methods it was demonstrated that thiosulphate is most tenaciously adsorbed to developed silver or silver foil. A limiting amount was held by any surface: one thiosulphate ion being estimated for every three silver atoms in the surface. On bleaching developed silver with acid dichromate, no decrease in radioactivity occurred, demonstrating quantitative formation of silver sulphide from adsorbed thiosulphate. On the basis of these observations, the silver sulphide content of bleached photographic images can be used to estimate the specific surface of the silver. Reasonable estimates were obtained of the particle size of a Carey-Lea silver sol. In agreement with earlier X-ray determinations, the mean filament diameters of developed silver from a series of emulsions did not increase much with increased undeveloped grain size.     

非银核／乳化银壳多相组合光敏微晶体系

本文扼要介绍了近十几年开发出来的一种由非银核和卤化银壳组合微晶体所构成的新成像体系。这种新的成像体系具有一系列优越性，如：本征感光度高、光学增感效果好、遮盖力强和耗银量低等。因此将会有广阔的发展前景。     

银二聚体掺杂与甲酸根掺杂立方体溴化银乳剂的协同增感研究

使用反馈式微机控制双注仪，在晶体生长过程中的某一时刻，一定pAg下，同时加入一定浓度的二甲基胺硼烷（DMAB）和一定浓度的甲酸盐，分别制得了甲酸根离子处于晶体次表面位置的立方溴化银微晶乳剂和Ag2与甲酸根同处于晶体次表面的立方溴化银微晶乳剂。对此两份乳剂感光性能的测试结果表明：（1）单独甲酸盐掺杂乳剂与Ag2、甲酸根协同掺杂乳剂相比，二者感光度相同；（2）单独甲酸盐掺杂乳剂与Ag2、甲酸根协同掺杂乳剂相比，二者经常规的硫加金化学增感和光谱增感后，前者增感明显优于后者；（3）卤化银颗粒内部的Ag2或甲酸根掺杂可同时与常规的表面硫加金增感和光谱增感进行协同增感；（4）所有的掺杂乳剂，包括原始、硫加金和光谱增感的掺杂乳剂，它们的灰雾均保持在低水平。     

硫醚类二当量品红成色剂

对硫醚类二当量品红成色剂与四当量成色剂进行了比较,说明所述成色剂有更高照相活性与稳定性,并解释了与 Ｄ Ｉ Ｒ 品成色剂的区别。     

用于He/Ne激光感光材料的感红光谱增感剂

介绍了用Ｈｅ／Ｎｅ激光感光材料的感红增感染料的类型、合成路线、２１种合成染料的部分理化数据及照相性能．     

The Topography,Mechanisn1 of Topochemical Transformations and the Sources of Chelnical Sensitization in the Ripening of Photographic En1ulsions

The sensitization of a photographic silver-halide emulsion is intimately connected with the micro-structure of the solid phase. This paper summarizes and discusses the knowledge gained during recent years, in particular the work of the author and his collaborators. Chemical sensitization is studied as a surface phenomenon. The importance of intrinsic lattice defects and impurity centres for photographic sensitivity is evaluated. The relation between chemical sensitization and the formation of fog is then discussed. A survey of the sources of chemical sensitization in the ripening of emulsions is followed by a comparison of the characteristics of ripening and photolysis and a discussion of the stability of impurity centres and latent-image centres. Finally an attempt is made at summarizing the lows which can be observed in the phenomena of chemical sensitization.     

AgBr/I纳米粒子乳剂的制备及性能研究

用络合—沉淀法制备了卤化银含量３０ｇ／Ｌ，粒子大小２０ｎｍ以下的ＡｇＢｒ／Ｉ纳米粒子乳剂，研究发现：ＡｇＢｒ／Ｉ纳米粒子表现出较大的表面活性，并由此导致了其乳剂具有比常规乳剂低得多的感光度和高得多的灰雾，乳剂的最佳碘含量增加到了１１％，硫增感对纳米粒子乳剂没有效果，但硫加金增感表现出有效性。     

Nano-silver mediated polymerization of pyrrole: synthesis and gas sensing properties of polypyrrole (PPy)/Ag nano-composite

Thermal polymerization of pyrrole was performed using silver nitrate as source of silver ions followed by its conversion to Polypyrrole (PPy)/Ag nano-comoposites without using any external oxidizing agent or solvent. The formation of PPy was monitored by UV-Visible absorption spectroscopy showing a band at approximately 464 nm. XRD measurement confirmed characteristic peaks for face centered cubic (fcc) silver and presence of PPy at 2 theta of approximately 23 degrees suggesting the formation of PPy/Ag nanocomposite. Transmission electron microscopy (TEM) images showed non-aggregated spherical Ag nano-particles of about 5-10 nm. PPy/Ag thick film acts as a NH3 sensor at 100 degrees C, a H2S sensor at 250 degrees C and CO2 sensor at 350 degrees C. The thick films showed capability to recognize various gases at different operating temperature.     

Sulphur Sensitization: The Effect of Sensitizer Concentration on the Constitution of Fog and Sensitivity Centres

Coatings prepared from emulsions sensitized with a range of quantities of thiourea have been treated with dilute solutions of chromic acid and gold thiocyanate prior to exposure and development. The effect of the oxidizing agent and gold treatment on the fog centres depends on the condition of sulphur sensitization. The results can be explained if fog centres consist of both silver and silver sulphide. The relative proportions of these two components are related to the quantity of sulphur sensitizer added to the emulsion.