The conventional photographic process1,2,3 involves several steps: the photogeneration of electron–hole pairs in crystals of a silver halide; the reduction of silver cations to atoms by some fraction of these electrons; the subsequent build up of atoms to give clusters (the ‘latent image’); and the complete reduction by a developer of crystallites having more than a critical number of silver atoms per cluster. The effective quantum yield, Φeff, of photoinduced electron–hole pairs produced per photon absorbed is less than the theoretical limit (Φtheory = 1), because of the fast recombination of some fraction of the pairs1,2,3,4,5,6. Here we describe an approach for enhancing the yield of useful photogenerated electrons, in which the silver halide is doped with formate ions, HCO-2. The dopant ions act as hole scavengers, thus enhancing the escape of electrons from pair recombination. Moreover, the resulting CO˙-2 radical can itself transfer an electron to another silver cation, so raising the theoretical yield to two silver atoms per photon absorbed. This photoinduced bielectronic transfer mechanism is strictly proportional to the light quanta absorbed—the dopant ions do not induce spontaneous reduction of silver cations in the dark—and appears to be close to the theoretical limit of efficiency. The efficiency is constant at all illumination levels and applies to both dye-sensitized and unsensitized crystals. We suggest that this approach is a promising route for improving the performance of photographic emulsions7.
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Harbison,J. M. & Spencer,H. E. in The Theory of the Photographic Process 4th edn (ed. James, T. H.) (Macmillan, New York, 1977).
Glafkides,P. Chimie et Physique Photographiques 5th edn (CEP Edition, Paris, 1987).
Tani,T. Photographic Sensitivity (Oxford Univ. Press, New York, 1995).
Hamilton,J. F. & Baetzold,R. C. The paradox of Ag2 centers on AgBr: reduction sensitization vs. photolysis. Photogr. Sci. Eng. 25, 189–196 (1981).
Tani,T. & Murofishi,M. Silver microclusters on silver halide grains as latent image and reduction sensitization centers. J. Imaging Sci. Technol. 38, 1–9 (1994).
Hailstone,R. K. et al. Achieving high quantum sensitivities with hydrogen hypersensitization. 1. Measurement. J. Imaging Sci. 32, 113–124 (1988).
De Keyzer,R., Tréguer,M., Belloni-Cofler,J. & Remita,H. (AGFA-Gevaert) A photosensitive silver halide element with increased photosensitivity. Patent no. EP97 202.897.0 (11 December 1997).
Hailstone,R. K., Liebert,N. B., Levy,M. & Hamilton,J. F. Latent subimage in a AgBr model emulsion. 1. Sulfur-plus-gold-sensitized versions. J. Imaging Sci. 31, 185–193 (1987).
Schwarz,H. A. & Dodson,R. W. Reduction potentials of CO-2 and the alcohol radicals. J. Phys. Chem. 93, 409–414 (1989).
Allen,A. O. The Radiation Chemistry of Water and Aqueous Solutions (Van Nostrand, Princeton, 1961).
Belloni,J., Saito,E. & Tissier,F. Photodetachment of electrons from alcoholate ions in liquid ammonia. J. Phys. Chem. 79, 308–309 (1975).
Swallow,A. J. in The Study of Fast Processes and Transient Species by Electron Pulse Radiolysis (eds Baxendale, J. H. & Busi, F.) 289–315 (NATO ASI Ser. Vol. 86, Reidel, Dordrecht, 1981).
Frank,S. N. & Bard,A. J. Semiconductor electrodes. 12. Photoassisted oxidations and photo-electrosynthesis at polycrystalline TiO2 electrodes. J. Am. Chem. Soc. 99, 4667–4675 (1977).
Hykaway,N., Sears,W. M., Morisaki,H. & Morrison,S. R. Current-doubling reactions on titanium dioxide photoanodes. J. Phys. Chem. 90, 6663–6667 (1986).
Herz,A. H., Danner,R. & Janusonis,G. in Absorption from Aqueous Solution 173 (American Chemical Soc., Washington DC, 1968).
Guo,S. & Hailstone,R. Spectroscopic and sensitometric studies of chemically produced silver clusters. J. Imaging Sci. Technol. 40, 210–219 (1996).
Mostafavi,M., Marignier,J.-L., Amblard,J. & Belloni,J. Nucleation dynamics of silver aggregates. Simulation of the photographic development process. Rad. Phys. Chem. 34, 605–617 (1989).
Belloni,J., Mostafavi,M., Marignier,J-L. & Amblard,J. Quantum size effects and photographic development. J. Imaging Sci. 35, 68–74 (1991).
Hailstone,R. K. Liebert,N. B., Levy,M. & Hamilton,J. F. Achieving high quantum sensitivities with hydrogen hypersensitization. 2. Mechanism. J. Imaging Sci. 35, 219–230 (1991).
Silberstein,L. On the number of quanta required for the developability of a silver halide grain. J. Opt. Soc. Am. 31, 343–348 (1941).
The present work has been performed under an AGFA–CNRS contract.
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Belloni, J., Treguer, M., Remita, H. et al. Enhanced yield of photoinduced electrons in doped silver halide crystals. Nature 402, 865–867 (1999) doi:10.1038/47223
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