Adsorption of 4–Hydroxy–6–methyl–l,3,3a–tetrazaindene in Aqueous Silver Halide Dispersions

Adsorption determinations of the title compound (TAI) al 25°C in aqueous gelatin dispersions of cubic AgCI and cubic or octahedral AgBr conlirm that its adsorption is favoured by high pH and low pAg. This behaviour is interpreted in terms of competition for surface sites among halide ion, TAP (the azaindene’s anionic deprotonation product) and TAIH (the uncharged product). The resulting competitive adsorption model was used to calculate TAI^- surface coverages at silver halide surfaces. These calculated coverages were confirmed experimentally at various pH and pAg values. The adsorption constants and limiting site areas of TAIH, TAI and halide ions are compared. TAI^- is more strongly bound to cubic AgCI than to cubic AgBr, and, relative to TAI^-, the adsorption nf TAIH is negligible at pH >4. At saturation, the surface occupancy by TAP on octahedral AgBr is about twice that on cubic AgBr. with a limiting site area of about 0.25 nm²/TAI^- al octahedral AgBr and cubic AgCI surfaces. These data are consistent with an adsorption model involving TAI^- on its short edge in a close-packed monolayer.     

Electronic properties of chemically produced silver clusters: grain morphology studies

Abstract

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.     

Latent Image Formation at High Intensity Exposures in Photographic Emulsions

After a critical review of some important literature data on reciprocity law failure at high intensity exposures (HIRF) we discuss recent experimental results about HIRF in AgCl relative to AgBr fine grained model emulsions in the primitive, sulphur (S), gold (Au) and gold + sulphur (Au + S) sensitized state. Influence of the pAg during ripening on HIRF is also outlined.

Although some results are qualitatively equal on both silverhalides, there are nevertheless important quantitative differences as for example the greater effectiveness of Au in the AgCl emulsion. Interpretation of the differences is based on the idea of the stronger catalytic activity of sensitivity specks to reduce AgCl in comparison with AgBr. Recent results are also mentioned concerning the mechanism of the TAI action (Tetra-Aza Indene) in AgCl and AgBr emulsions at different intensity exposures.     

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。     

On the Crystal Habit and Particle Size Distribution of AgBr Emulsions Prepared in the Presence of Synthetic Colloids

An account is given of the further experiments concerning the particle size distribution and crystal habit of AgBr particles in emulsions prepared in the presence of synthetic colloids such as polyacrylamide. paly-N-methylacrylamide and polr-N,N-dimethylacrylamide. The data have been obtained by examination of the emulsion with on electron microscope.     

Correspondence

It is a well known phenomenon that the absorption spectrum of an adsorbed dye in silver halide emulsions can show different maxima, depending on the structure of the dye itself and on the adsorbing crystal surface.

In the present study the impact of the grain habit of silver bromide and silver iodobromide on the absorption spectrum of several carbocyanine dyes was examined. The results prove that J-aggregation is generally favoured by an octahedral habit. A model for J-band formation is proposed.

The influence of incorporated iodide ions is due to the change of the crystal habit rather than to a direct impact on the absorption Spectrum.     

{110} Planes During the Dissolution of AgBr Microcrystals

Etching of silver bromide microcrystals by Na₂S₂0₃, Na2S03, or KCN produced crystal shapes essentially bounded by {110} planes. Regular rhombic dodecahedra were observed during etching of octahedral AgBr crystals while complicated polyhedra with exclusively {110} planes were obtained from cubic AgBr crystals.     

亲水型光敏热成像材料的pH对pAg的影响

测定并分析了亲水型光敏热成像材料的硬脂酸银以及加入其它组分后,在不同pH值时的pAg值变化.结果表明：随着pH值的增加,硬脂酸银体系的pAg值升高;硬脂酸银被AgBr取代后以及加入四氯邻苯二甲酸（H2PACl4）和酞嗪（PHZ）等组分,体系的pH值和pAg均发生相应的变化.     

快速彩纸氯化银立方晶体外延溴化银乳剂制备方法的研究

外延量在0—5个摩尔百分数范围研究其对氯化银立方晶体外延溴化银乳剂照相性能的影响,并探讨三种供快速彩纸用乳剂的制备途径。     

Silver carboxylate nanostructure nucleation and growth on AgBr crystals

The initial stage of the reaction between sodium stearate (NaSt) and AgNO(3) produces silver stearate (AgSt) micelles, [(C(18)H(35)O(2))(x)(Na(x-y))(Ag(y))(H(2)O)(z)], and aggregations of these AgSt micelles in the form of cubic pre-AgSt crystals. When cubic grains of 50?nm AgBr are added to the NaSt dispersion prior to the AgNO(3), the reaction proceeds to form the silver stearate micelles, but not the aggregation of those micelles. Instead, the {111} silver ion planes of the cubic AgBr crystal corners provide nucleation sites for silver stearate micelle deposition and crystal growth. After nucleation, the AgSt micelles evolve into nanostructured bud-like formations via an epitaxial interface on one or several corners of each AgBr cubic crystal. Over time, additional AgSt micelle deposition enables the buds to grow longer into strand-like structures, which then connect to form the beginnings of the ultimate silver stearate crystal plates.     

SrTiO3铁电体反铁畸变的序参量半

钛酸锶（SrTi03）的反铁畸变是氧八面体绕[001]轴转过一微小角度θ引起的。提出一种晶体学原胞的选取方法，能很好地说明相变前后对称性的变化。由居里原理，分析其序参量是一个三阶全对称的极张量。     

The Action of Ferricyanide on Sulphur-Sensitized Emulsions

It is shown that sulphur-sensitized emulsions may be fogged or desensitized by ferricyanide, according to the concentration, provided that a sufficient supply of silver ions is made available. The distinction previously drawn betwsen this form of sensitization and silver-sensitization on the basis of response to ferricyanide is thus weakened.⁽⁷⁾ It is suggested that silver ions are adsorbed to sensitizing substance and promote adsorption of ferricyanide. Some results on the absorption of ferricyanide to unsensitized emulsion grains at various pAg levels are given. Slight effects can also be produced in unsensitized emulsions, pointing to the presence of foreign centres created during physical ripening. A small part of the sensitivity created by digestion, which resists the action of ferricyanide, is attributed to etching by the sensitizer. The amount of ferricyanide required to desensitize an emulsion at low pAg is slightly greater than that needed for latent image destruction. The response of digested emulsion to small amounts of ferricyanide (production of fog) would probably enable a very sensitive test for the latter to be worked out. In gensral, a parallel between the action of light and ferricyanide is noted.     

Effect of Grain Size on the Ionic Conductivity of Silver Halides

An equation is derived for the ionic conductivity of silver halide emulsion grains with dimensions comparable to the Debye length of intrinsic defects. The conductivity of the grains is shown to be inversely proportional to the grain size. The surface potential distribution depends on both the shape and size of the grains. The surface charge density, surface potential, and volume potential are estimated for octahedral, cubic, and tabular AgBr grains.     

Amorphous structure melt-quenched from defective Ge2Sb2Te5

Ge₂Sb₂Te₅ (GST) is a technologically important phase-change material for data storage, where the fast reversible phase transition between crystalline and amorphous states is used for recording information. The encoding is achieved by the large contrast in physical properties between the two states. Ge vacancies (V_Ge) and Sb antisite atoms (Sb_Te) are primary point defects in crystalline GST. The effect of V_Ge and Sb_Te on the atomic arrangements in amorphous GST is unknown, which, however, has significant effects on the performance of GST. In this work, by means of ab initio molecular dynamics calculations, the atomic arrangements in amorphous ideal and defective GST have been investigated. The results show that the amorphous structure of GST with Sb_Te (St-GST) or with V_Ge (V-GST) has the same cubic framework and close chemical ordering to ideal GST, and hence similar fast reversible phase transition behavior is expected in the defective phases. Furthermore, the presence of Sb_Te or V_Ge in the crystalline phase will result in much more Ge atoms in a tetrahedral geometry as well as in a fourfold octahedral environment in the amorphous state. Especially in V-GST, around 36 % Ge atoms occupy a fourfold octahedral geometry. As fourfold octahedral Ge atoms can enhance the large contrast in physical properties between the crystalline and amorphous phases, introducing Ge vacancies would be an efficient way to improve the performance of GST phase-change materials.     

Efficient and Stable CsPbI3 Solar Cells via Regulating Lattice Distortion with Surface Organic Terminal Groups

All‐inorganic cesium lead iodide perovskites (CsPbI₃) are promising wide‐bandgap materials for use in the perovskite/silicon tandem solar cells, but they easily undergo a phase transition from a cubic black phase to an orthorhombic yellow phase under ambient conditions. It is shown that this phase transition is triggered by moisture that causes distortion of the corner‐sharing octahedral framework ([PbI₆]^4?). Here, a novel strategy to suppress the octahedral tilting of [PbI₆]^4? units in cubic CsPbI₃ by systematically controlling the steric hindrance of surface organic terminal groups is provided. This steric hindrance effectively prevents the lattice distortion and thus increases the energy barrier for phase transition. This mechanism is verified by X‐ray diffraction measurements and density functional theory calculations. Meanwhile, the formation of an organic capping layer can also passivate the surface electronic trap states of perovskite absorber. These modifications contribute to a stable power conversion efficiency (PCE) of 13.2% for the inverted planar perovskite solar cells (PSCs), which is the highest efficiency achieved by the inverted‐structure inorganic PSCs. More importantly, the optimized devices retained 85% of their initial PCE after aging under ambient conditions for 30 days.     

Catalytic effect of water on the synthesis of cubic BN

The transition pressure and temperature of graphitic hexagonal boron nitride to the dense cubic form is drastically reduced by the presence of water in the starting material. A water content of about 40 wt% reduces these conditions to about 50 kb and 600°C. Cubic BN obtained under such conditions is extremely small in crystal size, which was estimated by the broadening of x-ray powder diffraction lines.     

Structural phase transitions in BaPrO3

The crystal structures adopted by BaPrO₃ at and above ambient temperature have been examined using a combination of synchrotron X-ray and neutron diffraction. BaPrO₃ has been established to undergo a series of phase transitions from cubic. BaPrO₃ is the second A²⁺B⁴⁺O₃ perovskite found to adopt rhombohedral symmetry in preference to the I4/mcm tetragonal structure. Analysis of the octahedral tilting through the rhombohedral to cubic phase transition indicates that this transformation is continuous and tricritical in nature. The tricritical behaviour of this transition is likely to be a result of the competition between tetragonal and rhombohedral structures to be the preferred phase, with the rhombohedral symmetry adopted by BaPrO₃ being stabilised by the unusually large B-site cation.     

Concerning the brittleness of iridium: An elastic and electronic view

The brittleness of Ir has become a challenging and puzzling problem for decades and its fundamental mechanisms are controversial with each other in the literature. The present first principles calculation aims to get a deep understanding of the brittleness of Ir from an elastic and electronic view. It is found that Ir has normal pressure-dependent mechanical behavior, while the temperature-dependent behavior of Ir is unusual and contrary to that of other FCC metals, and that pressure decreases the brittleness of Ir, whereas temperature increases its brittleness, suggesting that the machining of Ir products should be performed at low temperature and high pressure. Moreover, electronic structure and crystal field theory reveal that Ir has the mainly octahedral bonding, which would be transformed to the mainly cubic bonding under high pressure, while become more octahedral and directional at high temperature. In addition, the implication and importance of the similarities between Ir and semiconductors are also discussed.     

Photographic Properties of Polyethylene Oxide II. Effect of PEO on the Growth Habit of Silver Halide Grains

The effect of polyethylene oxide (PEO) on the growth hobit of silver iodobromide emulsion groins was investigated. Cubic (100) and tetradecahedral (100 + 111) iodobromide groins become more octahedral (111) in shope in the presence of PEO. The effect increased with increasing iodide content, while pure bromide grains were little influenced by PEO.     

Powder X-ray diffraction study of the rhombohedral to cubic phase transition in TiF3

Synchrotron powder diffraction has been used to examine the crystal structure of the TiF₃ between 20 and 450 K with emphasis on the cubic to rhombohedral structural phase transition near 370 K. This transition involves an apparently continuous reduction in the tilts of the TiF₆ octahedra. A remarkable difference in the thermal expansion coefficients in the two phases is observed.