Contribution to the Discussion of the Mechanism of Spectral Sensitization of Silver Halide

Siegel, J.; Faßler, D.; Friedrich, Manuela; Grossmann, J. Von; Kempka, U.; Pietsch, Heiko

doi:10.1080/00223638.1987.11738442

Cited by 9 publications

(16 citation statements)

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“…In order to explore the process behind chemical enhancement, we compare the ratios of SERS intensities with another property of the SERS molecules that can be inferred from an independent ESR experiment performed on the same series of polymethines on photographic silver halides during irradiation: The ESR signal appears due to radicals formed by the reduction of the excited polymethine dyes. The proposed process includes excitation of the positively charged dye and then, an electron transfer from an outer donor to the excited dye resulting in a dye radical following the scheme: Dye + (excitation)→ Dye + * (electron transfer)→ Dye ● . The intensity-time curve of the ESR signal enabled the determination of the quantum yield of the radical generation …”

Section: Results and Discussionmentioning

confidence: 99%

“…In that work, it has been inferred that the chemical enhancement related to orbital interactions between the metal and molecule scales as (ω X /ω e ) 4 , where ω X is the HOMO–LUMO excitation energy of the free molecule and ω e is lowest charge-transfer excitation energy of the metal–molecule complex. For the considered dye series, while ω X is almost the same, ω e can vary due to relatively different HOMO levels of the dyes …”

Section: Results and Discussionmentioning

confidence: 99%

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Chemical Contribution to SERS Enhancement: An Experimental Study on a Series of Polymethine Dyes on Silver Nanoaggregates

Kneipp¹

2016

J. Phys. Chem. C

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We investigate the chemical contribution to SERS on a series of polymethine dyes attached to silver nanoparticles in aqueous solution exploiting a total average enhancement level of 107–108. On top of uniform plasmonic and molecular resonance enhancement, we obtain changes in SERS signal levels and particularly changes in relative scattering intensities for selected Raman lines in the SERS spectra of very similar polymethine dyes. This variation in chemical SERS enhancement within the dye series correlates with the generation of dye radicals of the same dyes on photographic silver halides reported in the literature, where the dye radicals were determined by ESR spectroscopy. The correlation between these two experimentally independent observables suggests transfer and/or exchange/sharing of electrons between the metal and the molecule as basic process for chemical SERS enhancement, where the efficiency of the process depends on the molecular structure. Despite that the main contribution in SERS is caused by plasmonic field enhancement, the chemical contribution to SERS can be a sensitive tool to extract information on interest for processes that rely on charge transfer between surfaces/nanostructures and molecules such as catalysis or spectral sensitization.

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Section: Results and Discussionmentioning

confidence: 99%

Section: Results and Discussionmentioning

confidence: 99%

Chemical Contribution to SERS Enhancement: An Experimental Study on a Series of Polymethine Dyes on Silver Nanoaggregates

Kneipp¹

2016

J. Phys. Chem. C

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“…The type containing an even number of CH-groups in the polymethine chain, a,u-diheterosubstituted polyenes (2), are marked by a high degree of alternation p-bond order (and length) in the ground state (S 0 ) and S 1 excited state, while p-electron densities at the carbon atoms within the polymethine chain are practically equivalent…”

Section: Methodology Of Quantum-chemical Calculationsmentioning

confidence: 99%

Electronic properties of polymethine systems. 6. Bond order and bond length changes upon excitation

Kachkovski

Zhukova

2004

Dyes and Pigments

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“…As in chemical sensitization, spectral sensitization is usually done after precipitation but before coating, and usually is achieved by adsorbing certain organic dyes to the silver halide surfaces (47,48,(212)(213)(214)(215)(216)(217)(218)(219)(220)(221)(222)(223)(224)(225)(226)(227)(228)(229). Once the dye molecule is adsorbed to the crystal surface, the effects of electromagnetic radiation absorbed by the dye can be transferred to the crystal.…”

Section: Spectral Sensitizationmentioning

confidence: 99%

“…This process is favored when dyes are aggregrated and can facilitate the transport of the photohole from the point of origin to the growing latent-image center. Dye photoholes have been detected and characterized by electron spin resonance (225) and reflectance spectroscopy (224,235).…”

Section: Dipolar Amidic Systemmentioning

confidence: 99%

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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Contribution to the Discussion of the Mechanism of Spectral Sensitization of Silver Halide

Cited by 9 publications

References 0 publications

Chemical Contribution to SERS Enhancement: An Experimental Study on a Series of Polymethine Dyes on Silver Nanoaggregates

Chemical Contribution to SERS Enhancement: An Experimental Study on a Series of Polymethine Dyes on Silver Nanoaggregates

Electronic properties of polymethine systems. 6. Bond order and bond length changes upon excitation

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