About the Nature of the Sensitivity Specks Formed by Gold Sensitization and Their Function during Latent Image Formation-A Controversial Subject

Faelens, P.; Borginon, H.

doi:10.1080/00223638.1976.11737883

Cited by 2 publications

(4 citation statements)

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“…Furthermore, chemical sensitizers can determine the topography of latent-image formation and improve the stability of the latent-image center once formed. Typical chemical sensitizers include sulfur-containing compounds such as thiourea and sodium thiosulfate (171)(172)(173)(174)(175)(176)(177)(178), gold-containing complexes such as gold thiocyanate and potassium tetrachloroaurate (17,18,179,180), and chemical reducing agents such as hydrogen gas and tert-butylamine borane [7337-45-3] (181-184). These sensitizers can be used either alone or in combination to increase sensitivity, and produce optimum photographic properties when used in trace amounts, ie, µmole sensitizer per mole Ag.…”

Section: Chemical Sensitizationmentioning

confidence: 99%

“…The role of gold in chemical sensitization is at least twofold (17,18,200,201). Gold enhances catalytic activity of the latent image center with which it is associated.…”

Section: Chemical Sensitizationmentioning

confidence: 99%

“…Combining equations [16][17][18][19] generates an expression that predicts the dependence of development rates on halide ion, hydroxide ion, and reducing agent concentrations. Most analyses using the electrochemical model use additional semiempirical parameters.…”

Section: −(Rt/nf) Ln[a(d Ox )] − (Mrt/nf) Ln[a(h + )] + (Rt/nf) Ln[a(d)]mentioning

confidence: 99%

“…Furthermore, the ability of a developer to discriminate between exposed and unexposed grains has been attributed to this inverse relationship between silver center activity, a(Ag 0 ), and silver center size (286)(287)(288); ie, as the size of the silver center increases, E, the specific rate constant, and the rate of development increase (see eqs. [16][17][18][19]. As development proceeds, oxidation byproducts, eg, D ox and Br − , build up.…”

Section: −(Rt/nf) Ln[a(d Ox )] − (Mrt/nf) Ln[a(h + )] + (Rt/nf) Ln[a(d)]mentioning

confidence: 99%

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Photography

Locker¹

2000

Kirk-Othmer Encyclopedia of Chemical Technology

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PHOTOGRAPHYThe unique light-sensing properties of silver halide crystals have been recognized since the 1500s. In spite of many technical advances in nonsilver halide (eg, electronic) technologies, chemically based silver halide systems continue to dominate in the ability to record images (1-3) of superb image quality and archival characteristics. Photochemical reduction in which the silver ion, Ag + , in the ionic silver halide crystal is reduced to elemental silver, Ag 0 (4-7) was first observed by the alchemist Fabricius in 1556. As photochemical reduction continues, elemental silver atoms aggregate and grow into clusters of a colloidal size sufficient to scatter light and produce hue shifts. The science of photography uses this photochemical property of silver halide to form images and record scenes. One of the earliest researchers to produce such a photochemical image was Schultze in 1727 (8). In these experiments, solutions of silver nitrate and white chalk were photochemically reduced to produce metallic silver images when the solutions were exposed through stencils.The daguerreotype process, prepared by Daguerre in 1837, and the calotype process, produced by Talbot in 1841, were among the first photographic techniques to produce continuous-tone images as reproductions of scenes (9, 10). The steps of a typical daguerreotype process include polishing and cleaning a silver-plated copper plate; treating the silver side of the plate with iodine vapors to convert silver into light-sensitive silver iodide [7783-96-2], AgI; exposing the plate through the optics of a camera that projects and focuses a scene on the plate, ie, where light strikes these plates, silver ions are photochemically reduced to silver metal; and treating the exposed plate with mercury. The mercury reacts with silver metal to produce a silver amalgam.White silver amalgam appears in areas of the plate exposed by light; the unexposed areas remain dark, thereby producing a positive image.Daguerrotype images were produced primarily by the action of light. For the production of satisfactory images, long exposures to light, on the order of minutes, were required because many absorbed photons were necessary to reduce photochemically enough silver ions to silver metal for visible imaging. In 1841, Talbot announced the calotype process, which could reduce exposure times to seconds and produce visible images without dependence on the action of light (11). In the calotype process, the exposure of silver halide produced an invisible latent image that was composed of only trace amounts of reduced silver. This acted as a catalyst for subsequent chemical reduction, ie, a nonphotochemical continuation of the light-initiated reduction process that eventually produced a visible silver image. In addition to being sensitive to much lower light levels, the calotype process was less expensive than the daguerreotype process and provided a negative-positive system that could generate several positive copies from a single negative original. The use of chemical amplif...

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Section: Chemical Sensitizationmentioning

confidence: 99%

“…The role of gold in chemical sensitization is at least twofold (17,18,200,201). Gold enhances catalytic activity of the latent image center with which it is associated.…”

Section: Chemical Sensitizationmentioning

confidence: 99%