Spectral Sensitivity and Light Absorption of Dye-Sensitized Photographic Emulsions

Abstract

Direct measurements on emulsions sensitized with certain cyanine dyes show a correspondence between the shapes of the light absorption and sensitivity curves in the region of color sensitizing. It was found that the absorption curves of silver bromide dyed with some cyanine dyes are essentially the same as the absorption curves of the dyes in saturated inorganic salt solutions. It is postulated that there are two types of adsorption of cyanine dyes to silver bromide, aggregated and molecular. An emulsion sensitized with a cyanine dye under proper conditions can show sensitivity in different spectral regions, corresponding to the light absorption characteristics of dye adsorbed in the aggregated and molecular states.

Optical properties of astaxanthin solutions and aggregates

“…The great effectiveness of hydroxide ion is anomalous according to the Hofmeister series, but hydroxide ion may have a specific tendency to interact with carbonyl groups. Salts are known to influence the tendency of cyanine dyes to undergo aggregation and changes in spectrum, presumably by salting out the uncharged portion and interacting directly with the charged groups of the dye molecule (Leermakers et al, 1938). The yellow aggregate was obtained only with astaxanthin, but the yellow color is not dependent on the presence of carbonyl groups once the aggregate is formed, because it is maintained when the carbonyl groups of astaxanthin are reduced with sodium borohydride.…”

Latent image formation in photographic silver halide gelatine emulsions

“…The colour of dyes is slightly affected by their surroundings and is therefore not identical, say, for a dye crystal and a layer of dye adsorbed to silver halide. The spectral sensitivity of the latter system has been shown to run parallel with its absorption (Leermakers, Carroll andStaud 1937 a, Leermakers 1937).…”

Pulse Radiolysis Investigation of Radicals Derived from Water-Soluble Cyanine Dyes: Implications for Super-resolution Microscopy

“…Cyanine dyes, being shorter chain length analogues of the naturally occurring carotenoids, are among the most versatile artificial chromophores. The first synthetic cyanine dye was reported by Williams in 1857, and it was soon discovered that aggregates of new cyanine derivatives were able to sensitize silver-halide-coated photographic plates . Ordinarily such plates were sensitive only to the violet and blue regions of the spectrum, but by adding suitable cyanine dyes to the liquid emulsion or by bathing the dried emulsion film in dye solution, the plates could be rendered sensitive to green, yellow, orange, red, and even to the near-infrared (NIR) segment of the spectrum. , The result was a tremendous advance in the field of photography, and during the early twentieth century, a vast range of cyanine dyes was synthesized for this purpose. , The strength of these compounds as chromophores relates to the facile manipulation of the wavelength corresponding to the absorption maximum.…”