| COMMENTS |
by one of the work's authors Nanostructured AgX materials represent one of the major classes of industrially produced microcrystalline ionic semiconductors. "Our discovery proves the concept of active hole trapping in ionic semiconducting materials & the total annihilation of recombination". "The BIELECTRONIC nano-AgX system leads to the highest light efficiencies ever measured" |
| MECHANISM OF ACTION | The dopant formate ions act as hole scavengers & produce CO2 anion radicals in the process. These radicals transfer electrons to Ag cations. The overall process is known as "PHOTOINDUCED BIELECTRONIC TRANSFER" because 2 electrons are generated, one by the photon &, subsequently, one by the radical. The theoretical yield for this process is 2 Ag atoms per photon absorbed |
| TECHNOLOGY |
The use of a dopant may significantlty improve the perfor mance of photosensitive AgX emulsions used to make photographic films, according to scientists in Europe. A research team has shown that the sensitivity of AgBr emulsions increases by a factor of 10 when doped with formate ions (HCO2 anion). During the conventional photographic process, photons falling on AgX microcrystals cause the halide ions to generate pairs of electrons & positive holes. The Ag ions capture the electrons & the resulting neutral Ag atoms group into clusters of metallic Ag that form the "latent image". This image is then developed into a visible image. "One of the major inefficiencies in image recording with AgX used in conventional film is the recombination between photogenerated electrons & holes". To improve sensitivity modern films & print materials use AgX that are chemically sensitized with reagents contg labile S & Au atoms. Even so, recombination occurs &, as a result, 3-10 photons are required to generate one Ag atom. The theoretical limit is one Ag atom per absorbed photon. To date, model systems that achieve this limit give rise to fogging caused by side reactions that lead to latent-image formation in the absence of light. "The novelty & importance of present work is that, for the first time, the doped crystal behaves as an ideal system". "All the light energy is used to produce the latent image without electron recombination & without fogging". |
| UPDATE | 01.00 |
| AUTHOR | This data is not available for free |
| LITERATURE REF. | This data is not available for free |
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