2,2 -Cyanines adsorbed onto microcrystalline cellulose

Figure 43 shows the XPS spectra for the N Is region of several samples of 2,2 -cyanine adsorbed onto microcrystalline cellulose from an ethanolic solution after total solvent evaporation. We can clearly see that the N Is peak has a main... 

Fig. 42. (a) Variation of the intensity of fluorescence of l,l -diethyl-2,2 -cyanine adsorbed onto microcrystalline cellulose (steady state) measured as the total area under the corrected emission spectrum, If, as a function of the square root of the concentration of dye adsorbed onto microcrystalline cellulose. The solvents used for sample preparation were —ethanol, —dichloromethane. Full squares and open squares are used for type 1 and type II samples, respectively, (b) Same data as in (a) but now for l,l -diethy 1-2,2 -carbocyanine. 

By studying simple cyanines adsorbed onto microcrystalline cellulose it was possible to get some insight into the nature of the interactions of these cyanines with the polymer chains, namely in regard to the importance of hydrogen bonding of the probe to the substrate, which is of major importance in the immobilization process, and in minimizing the nonradiative transitions of the excited states. 

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