The Effect of S-donor Ligands on the Sensation of Silver Bromide Crystals with Iridium (III)

Different concentrations of potassium thiocyanate (SCN) were used in combination with Iridium (III) hexachloride (Ir) to surface sensitize an octahedral silver bromide emulsion. Surface sensitivity increased by 0.90 log H over the unsensitized emulsion when Ir and SCN were added during sensitization compared to 0.45 log H when the iridium salt was used alone. A decrease of 2.40 log H was observed when an Ir-SCN complex was formed and then added to the emulsion. An increase of 1.05 log H was obtained if gold, thiocyanate and iridium were used. Similar results were obtained using tetramethylthiourea (TMT) or thiodiglycol (TG) instead of SCN. The emulsion was sensitized with S+Au and Au+SCN for comparison. The mechanism of iridium sensitization is discussed based on the experimental results

Effect of stabilizers on gold sensitization

Previous work has shown evidence that some emulsion stabilizers can prevent rearrangement of adsorbed silver sulfide to a photographically active form. Full gold plus sulfur sensitization may be achieved by simultaneous introduction of the sensitizers or by adding gold after sulfur sensitization. As gold sensitization of an already optimally sulfur-sensitized emulsion may instead involve a direct chemical reaction, the effect of stabilizers on gold sensitization may not parallel their effect on sulfur sensitization. The stabilizers 6-methyl-4-hydroxy-l , 3 , 3a , 7-tet razaindene and l-phenyl-5-mercaptotetrazole retard but do not prevent gold sensitization in a sulfur sensitized emulsion. This may suggest that gold sensitization does not involve a rearrangement or other secondary process with which a stabilizer could interfere

Electronic properties study of sensitizing centers in chemical sensitization

Reduction sensitization, sulfur sensitization and sulfur-plus-gold sensitization are th

Influence of first developer solvent levels on the information storage capacity of negative and reversal images

Silver halide solvents are commonly used in the first developer of a reversal process to obtain brighter highlights and a higher effective speed. An investigation was carried out to determine the effect of a low and high level of solvent on the sensitometric char acteristics as well as the covering power, granularity, modulation transfer function (MTF) and the information storage capacity of Plus-X reversal film 7276. The investigation was designed such that the only variable in the systems studied was the first developer. D-67, i.e., D-19 containing two grams liter^-1 of potassium thiocyanate, was chosen as the high solvent first developer. D-19 with twenty-five grams liter^-1 of sodium sulfite, designated D19-25 in this investigation, was the low solvent first developer. Four systems were studied: 1) negative images developed in a low solvent developer (D19-25) 2) positive images developed in D-19 using a low solvent first developer (D19-25) 3) negative images developed in a high solvent developer (D-6 7) 4) positive images developed in D-19 using a high solvent first developer (D-67) The information storage capacity for each system was calculated from the signal to noise ratio across the spatial frequency range of zero cycles mm^-1 to twenty-five cycles mm^-1. The signal to noise ratio was determined from the gamma value of the D-log H curves, the MTF and the Wiener spectrum ordinate value derived from the granularity. Comparisons between the systems were made for each parameter as well as the information storage capacity. The comparisons were made two different ways: 1) at equal densities and 2) at equal exposures. No significant differences attributable to the solvent were found in the granularity, MTF and the information storage capacity when the ccmparisons were made at density levels of 0.50, 1.00 and 1.50 above base plus fog. Differences were seen in the covering power of each system. Slower speed and dark highlights, as evidenced in the positive D-log H curves, were obtained using D19-25 as the first developer. In creasing the exposure to compensate for the lower speed would not correct the dim highlights. This indicated that perhaps a more viable comparison could be made at equal exposure levels. Differences were observed in the covering power, granularity and information storage capacity when the comparisons were made at equal exposure levels. The covering power did not appear to influence the information storage capacity results since the trends were not the same. The covering power of the D-67 negative system was lower than the D19-25 negative system due to solution-physical development effects. The covering power of the positive systems were not different. The covering power values obtained for the positive systems were about forty- five percent higher than the covering power values. The granularity affected the information storage capacity re sults the most. As the granularity increased across the exposure range the amount of information detected decreased. Larger dif ferences were observed between the positive systems than the negative systems . Positive images developed in D-67 showed cleaner highlights, i.e., a lower D_min. level on the D-log H curve, a higher effective speed, about a ten percent decrease in granularity and an increase of about eighteen percent in the information storage capacity. Processing in a high solvent first developer provided a distinct advantage over development in a low solvent developer in terms of the parameters investigated in this study

A Quantitative Study of Cuprous Oxide Photodismutation

A cuprous oxide emulsion was made using noodling and washing emulsion making techniques. An attempt to use phthalated gelatin and coagulation washing resulted in the formation of cuprous hydroxide and destruction of the phthalated gel molecule and lack of coagulation within the emulsion. Cuprous oxide was also slurried with water and coated onto unglazed porcelain plates. The density-log exposure relationship was linear for the cuprous oxide slurry and non-linear for the cuprous oxide emulsion. The cuprous oxide film gave a speed value twenty-five times greater than that obtained with the slurry. The cuprous oxide dismutation system possesses great variability and little repeatability

Selective emulsion liquid membrane extraction of silver from photographic waste industries

The field of liquid membrane technology is currently undergoing a rapid expansion in research as well as its application as an industrial separation process. Liquid membrane can be manipulated to selectively separate a specific solute from a mixture and even to extract a solute against its concentration gradient. A liquid membrane system comprises of three liquid phases; feed phase, liquid membrane organic phase and receiving phase. Liquid membrane can be prepared using support or as emulsion (unsupported) liquid membrane. Emulsion liquid membrane is a liquid membrane in which the membrane phase of an emulsion is dispersed into the feed phase to be treated. This method was investigated as an alternative process for the recovery of silver from photographic waste, which contains various metals ions such as silver, iron, sodium and potassium. The important parameters governing the extraction process of silver such as agitation speed, homogenizer speed, surfactant and carrier concentrations, type of diluents, treat ratio and types of stripping solution were investigated. This process has been conducted in a batch system using a mixer-settler. The results show that the mobile carrier Cyanex 302 is selective towards silver and almost completely extract silver over the other metals that existed in the photographic waste. The optimum silver extraction was obtained by using 0.03 M Cyanex 302, 3 % (w/v) Span 80, 250 rpm stirring speed, 1.0 M thiourea in 1.0 M H2SO4 stripping agent, 1:5 of treat ratio, and kerosene as a diluents. The experimental result also shows that the emulsion liquid membrane system could be recycled twice having 80% of silver was extracted. In addition, theoretical studies show that the developed model could predict the extraction performance of the system understudied as obtained from experimental data

A study of silver chloride containing gold

Measurements of optical absorption, dielectric loss, photoconductivity and photolysis have been used to investigate the properties of silver chloride containing gold. The gold enters the silver chloride lattice either substitutionaly or as a separate phase of aurous or auric chloride depending on the method of preparation. The most interesting properties are shown by the aurous chloride phase which is produced by annealing in chlorine or nitrogen at 673º K and quenching to room temperature. The temperature and concentration dependences of the optical absorption of the aurous chloride phase indicate that the energy for the formation of a separate phase of aurous chloride approaches a minimum near 673º K. The incorporation of gold sensitises silver chloride for colloid formation. The photolysis of silver chloride is determined by measuring the optical absorption during irradiation. In silver chloride containing substitutional Au or auric chloride as a separate phase, the photolysis occurs mainly on the. surface. The incorporation of a separate phase of aurous chloride results in strong volume sensitivity to both blue and red light. The volume sensitivity is explained in terms of the spectral sensitisation of silver chloride by the aurous chloride. At temperatures above 170ºK irradiation results in the formation of silver and gold colloid and the conversion of aurous chloride to auric chloride. The thermal development which occurs at 423°K is attributed to the thermal decomposition of the aurous chloride phase. The properties of the deep hole and electron traps in silver chloride sensitised with europium have been studied by measuring both the photoconductivity and the thermally stimulated conductivity at low temperatures. The slow growth in the photoconductivity which occurs' on blue irradiation at 130º K is shown to be due to the effects of deep hole trapping and the gradual filling of intrinsic electron traps. Dielectric loss measurements are used to determine the binding energy of cation vacancies to impurity ions and the activation energy for reorientation of cation vacancies about impurity ions in silver chloride and bromide containing chromium and in silver chloride containing europium. These measurements and those of photoconductivity and thermally stimulated conductivity are made on a spectrometer developed for the continuous measurement of complex permittivity

Photonic hydrogel sensors

Analyte-sensitive hydrogels that incorporate optical structures have emerged as sensing platforms for point-of-care diagnostics. The optical properties of the hydrogel sensors can be rationally designed and fabricated through self-assembly, microfabrication or laser writing. The advantages of photonic hydrogel sensors over conventional assay formats include label-free, quantitative, reusable, and continuous measurement capability that can be integrated with equipment-free text or image display. This Review explains the operation principles of photonic hydrogel sensors, presents syntheses of stimuli-responsive polymers, and provides an overview of qualitative and quantitative readout technologies. Applications in clinical samples are discussed, and potential future directions are identified