Highly photosensitive

Dry-Film Resists Based on Radical Photopolymerization. Photoinitiated polymerization (PIP) is widely practiced ia bulk systems, but special measures must be taken to apply the chemistry ia Hthographic appHcations. The attractive aspect of PIP is that each initiator species produced by photolysis launches a cascade of chemical events, effectively forming multiple chemical bonds for each photon absorbed. The gain that results constitutes a form of "chemical amplification" analogous to that observed ia silver hahde photography, and illustrates a path for achieving very high photosensitivities. 

Deterioration. The causes of degradation phenomena in textiles (155—158, 164) are many and include pollution, bleaches, acids, alkaUes, and, of course, wear. The single most important effect, however, is that of photodegradation. Both ceUulosic and proteinaceous fibers are highly photosensitive. The natural sensitivity of the fibers are enhanced by impurities, remainders of finishing processes, and mordants for dyes. Depolymerization and oxidation lead to decreased fiber strength and to embrittlement. 

The success has been primarily due to the developments that occurred in the eady 1970s (3) at the University of Dundee (United Kingdom) where it was demonstrated that a device-quaUty amorphous siUcon semiconductor (i -Si) could be produced with the following features low concentration of defects, high photosensitivity, abiUty to be doped, and no size limitation. 

Photosensitive Reactions. The reduction of chromium (VI) by organic compounds is highly photosensitive, and this property is used ia photosensitive dichromate-coUoid systems. 

Amorphous (vitreous) selenium, vacuum-deposited on an aluminum substrate such as a dmm or a plate, was the first photoconductor commercially used in xerography (6). It is highly photosensitive, but only to blue light (2). Its light absorption falls off rather rapidly above 550 nm. Because of the lack of photoresponse in the red or near infrared regions, selenium photoreceptors caimot be used in laser printers having He—Ne lasers (632.8 nm), or soHd-state lasers (680—830 nm). 

Therefore, the obtained —CO—CH==CH—R group PS has a high photosensitivity property and can be cross-linked with the effect of light. The group is used in the field of photography [29,30]. 

The photovoltaic properties of PPV and PPV based soluble polymers have been quantitatively confirmed also for polythiophenes. The IN characteristics of ITO/ P30T/Au [60] and of ITO/P3HT/Au [61] diodes showed excellent rectification behavior and a high photosensitivity under reversed bias. 

The intense discoloration which developed rapidly upon UV exposure reveals the high photosensitivity of C-PVC that is even more pronounced than for PVC itself, as shown by the UV-visible absorption spectra of figure 5. After 15 minutes of irradiation, large amounts of polyenes have already accumulated in C-PVC, with sequence lengths up to 20 conjugated double bonds, while PVC is hardly affected after that short exposure. 

Polystannanes have been shown to display very interesting properties. They are highly photosensitive and exhibit photobleaching behaviour and on UV irradiation depolymerise to yield cyclic oligomers. The materials are thermally stable to 200-270 °C in air and at more elevated temperatures function as precursors to Sn02. " By using rhodium catalysts, branched polystannanes have been prepared. 

Polymers with other pendant photosensitive moieties such as 0-furylacrylic ester (2) or / -styrylacrylic ester (5) are highly photosensitive and have even higher photosensitivity after the addition of photosensitizers. However, the thermal stability of these polymers is inferior to that of the polymer with pendant cinnamic esters (4). Polymers with pendant benzalacetophenone (5), styrylpyridinium (6), a-cyanocinnamic ester (7) or a-phenylmaleimide (8) have high photosensitivity but they can not be sensitized. In addition, the photosensitive moieties that are used in the syntheses of these polymers are not commercially available, in contrast to cinnamic acid. 

Multilayer and heterogeneous systems allow us to increase our understanding of photogeneration and charge transfer processes and obtain the high photosensitivity needed for practical applications. Carrier injection into PVC of... 

New types of polymers containing imide groups were proposed recently with high photosensitivity [237, 238] of the order less than lpj. Photosensitivity of the polymers composed of a series of thiophenylenes moieties and imide groups [238] remarkably increased with the increase of crystallinity. The overlapped rr-orbitals perpendicular to the polymer chains lead to the more extended conjugated system. 

Attempts to obtain full Raman enhancement profiles to probe the possible effects of other states are continuing, but they have been hindered by the high photosensitivity of the compounds. 

In related studies of metal ions, Krasnovski learned that the oxides of titanium, zinc, or tungsten possess high photosensitizing activity in redox reactions comparable to the activity of porphyrins and chlorophylls 15). 

Hydrogenated amorphous silicon (a-Si H) is excellent material from the view point of high photosensitivity in the visible region, short photoresponse time, thermal stability, low-temperature process, and high production yield. 

CCD is a high-photosensitivity semiconductor chip, in which visible-light photons generate electron-hole pairs the electrons are trapped in potential wells and then read out... 

A similar effect was observed for the highly photosensitive nifedipine and molsidomine tablets where the loss of content decreased with concentration (Fig. 2) (Thoma K, Aman W. In preparation) (4). 

Oral liquids of very photosensitive drugs such as molsidomine and nifedipine are compromised by photodegradation during administration even in short exposure. For safety reasons and in view of its high photosensitivity, molsidomine oral liquid was withdrawn from the market. 

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