Light sensitive materials

Light-sensitive glasses Light-sensitive materials Light sources... 

A solid emulsion is a suspension of a liquid or solid phase in a solid. For example, opals are solid emulsions formed when partly hydrated silica fills the interstices between close-packed microspheres of silica aggregates. Gelatin desserts are a type of solid emulsion called a gel, which is soft but holds its shape. Photographic emulsions are gels that also contain solid colloidal particles of light-sensitive materials such as silver bromide. Many liquid crystalline arrays can be considered colloids. Cell membranes form a two-dimensional colloidal structure (Fig. 8.44). 

Figure 4. Simplified schematic of an optical/infrared focal plane array. The detector is a thin wafer of light sensitive material that is connected to a thin layer of solid state electronics - the connection is made either by direct deposition (CCD) or bump bonding (IR detector). The solid state electronics amplify and read out the charge produced by the incident light.

In order to provide resolution in two-dimensions, the light sensitive material is subdivided into an array of pixels, as shown in Fig. 5. These pixels are defined by electric fields that are created within the light sensitive material. The electric fields can be generated one of two ways (1) permanently defined by implanting (doping) a very small amount of another material, or (2) programmably defined by electric fields produced by wires in the solid state electronics. 

Light sensitive material is electrically partitioned into 0 2-t> array of pixels (each pixel is a 3-D volume)... 

Figure 5. Simplified schematic of the 2-D array of pixels in a focal plane array. The thin wafer of light sensitive material is partitioned into a two-dimensional array of pixels that collect the electric charge produced by the light. Each pixel is a three-dimensional volume that is defined by electric fields within the light sensitive material.

A very important attribute of light sensitive materials is their absorption depth. The absorption depth is the length of material that will absorb 63.2% of the radiation (1/e of the energy is not absorbed). After two absorption depths, 87% of the light has been absorbed, and after three absorption depths, 95% has been absorbed. To make an efficient detector of light, the material thickness should be several times the absorption depth. 

In the infrared, the light sensitive material is bump bonded at each pixel to a silicon multiplexer that amplifies the charge and multiplexes the outputs to external electronics, as shown in Fig. 17. The column and row boundaries are... 

Figure 17. Infrared array geometry. The light sensitive material is connected at each pixel by an indium bump bond to the silicon multiplexer that reads out the charge generated by the incident light. Figure courtesy of I. McLean (UCLA).

Applications The extractor is designed for use in any application where heat and/or light sensitive materials are to be extracted. In addition, by purging the vessel... 

Many other applications have been described for these compounds and the hst is so extensive that it is impossible to cover each example here. Nevertheless, it is noteworthy that appropriately substituted 4-arylidene-5(4r/)-oxazolones, for example, 359 and 360 have been reported as organic Iruninophores" " and electrophotographic light-sensitive materials," respectively. The use of apoca-rotenoid derivatives such as 362 as monomolecular films has also been described." For new materials, a number of water-insoluble oxazolones have been used for dyeing or printing synthetic fibers" and, in this context, 4-(pyren-1-ylmethylene)-2-substituted-5(4/i/)-oxazolones 357, prepared from pyrene-1-carboxaldehyde, have... 

A range of triazolo-fused bicycles, including imidazo-, pyrazolo-, thiazolo-, oxazolo-, and isoxazolotriazoles have been explored as components in silver halide photographic light-sensitive materials, as developers and for use in imageforming processes <1996USP5508154>. 

Other Transducers. Ultrasound also has been used for the measurement of force, vibration, acceleration, interface location, position changes, differentiation between the composition of differing materials, grain size in metals, and evaluation of stress and strain and elasticity in materials. Sonic devices can used to detect gas leaks, and to count discrete parts by means of an interrupted sound beam. Frequently, an ultrasonic device can be applied where photoelectric derices are used. Particularly tn situations where light-sensitive materials are being processed (hence presence of light must be avoided), ultrasonic devices may be the detectors of choice. 

It is known that cadmium sulfide (CdS) and ion oxide Te203) are visible light-sensitive materials, in particular, one-step photocata ysis of wate - is possible for CdS.25) Recently, Kudc et at. reported that bismuth vanadate (BiV04) snowed photocatalytic activity for 02 evolution from an aqueous silver nitrate solution under visible light.26 271 BiVCX is a very attractive photocatalyst although it is impossible to decompose water by a one-step process. Thus this material is a candidate for an 02 evolution photocatalyst to construct a two-phoion process 26) In other words, this material is expected to be an 02 evolution photocatalyst to... 

Colloids are classified according to the phases of the substances involved (Table 15.10). A colloid that is a suspension of solids in a liquid is called a sol, and a suspension of one liquid in another is called an emulsion. For example, muddy water is a sol in which tiny flakes of clay are dispersed in water mayonnaise is an emulsion in which small droplets of water are suspended in vegetable oil. Photographic emulsions also contain solid colloidal particles of light-sensitive materials such as silver bromide. Foams are suspensions of a gas in a liquid or solid. Foam rubber, Styrofoam, soapsuds, and aerogels are foams. Zeolites (Box 13.4) are a type of solid foam in which the openings in the solid are comparable in size to molecules. 

Photography based on silver halides as the light-sensitive material depends on physical and chemical properties that, although occurring individually in other compounds, form a combination in the silver salts that makes them unique in their... 

Many sulfide/sulfur-based toners can cause damage to light-sensitive materials, such as undeveloped negatives and papers. If you can smell the sulfur (rotten egg smell) then do not use the toner in a room in which undeveloped materials are stored. These toners can be used outdoors in daylight if necessary. 

Caution Should not be kept near light-sensitive materials as it tends to bring about their deterioration. Has the odor of rotten eggs or a high school chemistry experiment. Store in a tightly sealed bottle and store in a cool place. Do not handle with bare hands. 

---