Write-lock-read-unlock-erase Cycles

Write-lock-read-unlock-erase Cycles 

As discussed at the beginning of this chapter, photochromic systems represent potential molecular level memory devices. A number of problems, however, must be solved for practical applications. A challenge problem is to find systems with multiple storage and nondestructive readout capacity those in which the record can be 

It should be noted that the locking time of the written information bit is not indefinite (at 25 °C and pH = 3.0, the halflife of the back-reaction from AH+ to Ct is about 8 days). 

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Y is then reconverted back to X (erase). Such a write-lock-read-unlock-erase cycle could constitute the basis for an optical memory system with multiple storage and nondestructive readout capacity. 

Like anthocyanins,1331 which are one of the most important sources of color in flowers and fruits, synthetic flavylium salts in aqueous solutions undergo various structural transformations 34-371 that can be driven by pH changes and light excitation. Such transformations are often accompanied by quite dramatic color changes or color disappearance. In the last few years, the thermal and photochemical reactions of several synthetic flavylium salts have been investigated in great detail, 17 19,34-43] an(j jlag ]Deen shown that some of these compounds can perform write-lock-read-unlock-erase cycles and can also exhibit multistate/multifunctional behavior. 

Write-lock-read-unlock-erase Cycles... 

Fig. 16 Schematic energy level diagram for the species involved in the write-lock-read-unlock-erase cycle in the case of the 4 -methoxyflavilium ionJ39 ...

Fig. 17 Write-lock-read-unlock-erase cycle starting from the Ct form of the 4 -hydroxyflavy-lium compound. ...

Fig. 20 Write-lock-read-unlock-erase cycles for the unsubstituted flavylium ion. 43 For more detail, see text.

Fig. 21 Write-lock-read-unlock-erase cycles for the 4 -hydroxyflavylium ion, starting from the Ct form at pH = 5.5. Left-hand side light and pH-jump inputs in the absence of micelles. This part is equivalent to the cycle shown in Figure 16. Right-hand side light input at the autolocking pH in the presence of SDS micellesJ18 ...

Fig. 22 A write-lock-read-unlock-erase cycle with two memory levels, based on the 4 -hydroxyflavylium compound. ...

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