Rose bengal electronic absorption

These polymers separate into three groups which have different electronic absorption properties. Hie first is P-RB-51, the lowest in rose bengal content. This polymer has an Axi/A 2 ratio which is very similar to the ratio of A)i/A>2 for RB (Figure 2). The second group of polymers P-RB-102, P-RB-152, and P-RB-305 has a ratio of the two absorption maxima, A, p/A, which is very similar to, but lower than that of either P-RB-51 or RB. The last group of polymers shows a reduction in the ratio of A /A In this case, the amount of RB attached to the polymer is much larger by comparison. 

Fig. 7. Interactions of electronically excited adsorbate with adsorbent, (a) Spectroscopic evidence from absorption spectra of Rose Bengale (i) in 0.5 M KN03 aqueous solution (ii) adsorbed on glass (iii) adsorbed on transparent gold film, (b) Charge-transfer possibilities at illuminated interfaces (i) Reversible for adsorbate /metal (ii) nett electron donation from adsorbate for adsorbate/semiconductor I (iii) nett electron acceptance by adsorbate for adsorbate/semiconductor II (iv) low probability of charge transfer from bulk energy bands of adsorbate/insulator interfaces. Reproduced with permission and with minor adaptation from ref. 100.

Figure 1. Electronic absorption spectra of rose bengal derivatives...

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