Photosensors

A CCD is a two-dimensional array of silicon photosensors, each photosensor usually being referred to as a pixel. When radiation falls on a pixel, photoelectrons are produced in numbers proportional to the intensity of the radiation. A typical wavelength range to which the CCD is sensitive is 400-1050 nm, but this may be extended down to below 1.5 nm with a phosphor that converts short-wavelength into visible radiation. 

Wet screening is being replaced in many laboratories by instmments that use a photosensor to record the diameter of each particle in a water suspension as that suspension flows past the sensor. 

The eye is a remarkable photosensor that can detect a single photon and transmit its signal to the brain 807... 

Zhang, D., et al., Understanding charge transfer at PbS-decorated graphene surfaces toward a tunable photosensor. Advanced Materials, 2012. 24(20) p. 2715-2720. 

The signal measured by the photosensor expresses the intensity of the emitted fluorescence (Ip), which depends on the intensity of the incident light (/q) and sample concentration c, among other factors, such as the fluorescence (or quantum) yield (O), the molar absorption coefficient (e), and the optical path length (d). At low concentration, the intensity of emitted fluorescence is given by the following equation [33] ... 

The opsins probably perform a variety of different tasks, but their known roles are as photosensors or photoisomerases (Foster Bellingham 2002). Photosensory opsins such as the rod and cone opsins, P opsin and VA opsin use light to activate a phototransduction cascade that ultimately results in a change in membrane potential of the photoreceptor cell. By contrast, photoisomerases are involved in photopigment regeneration. The best described photoisomerase is... 

By using a cylinder to carry the photosensor, automatic processing was enabled. In 1960 the automatic photocopier was created and many millions have since been manufactured. The same process is used in microform printers and computer output laser or LED printers. 

There is growing evidence of developing high-technology uses of pyridines, particularly as quaternary salts, as components of electrolytic capacitors, photocondnctors. rechargeable batteries, complex-coated electrodes for photosensors, electrochromic display elements and photoresist matrix resins. 

The previous section described the connection of a biocomponent PSI to a gold nanoparticle-attached molecular wire with a methylnaphthoquinone moiety to construct a photosensor. In this section, we present a combination of this technique, to connect PSI to an artificial molecular wire, with the technique used for ITO modification with molecular wires described earlier for the development of a biophotoelectrode. 

All of the systems include a chromophore (photosensor or photoreceptor) that absorbs the light. The excitation of the photoreceptor is followed by a chemical reaction such as electron transfer, photoisomerization, ion channel formation, etc. 

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