Octadecyl rhodamine B

Figure Bll.2.1 shows the normalized autocorrelation functions of various micelles loaded with octadecyl rhodamine B chloride (ODRB) at pH 7 (PBS buffer)3 . The differences in size of the micelles are clearly reflected by the differences in diffusion times td- The translational diffusion coefficients are reported in Table Bll.2.1, together with the hydrodynamic radii and the aggregation numbers.

FIG. 6 Fluorescence microscopic images of monolayers of 5 on aqueous subphases of pHs 3.0 and 9.5, 20°C, at a surface pressure of 15 mN m-1 octadecyl Rhodamine B (1 mol%) was included in monolayers as a fluorescent probe (top). A possible model for the observed crystalline domain due to helix-helix macrodipole interaction at pH 3.0 (bottom). 

Ediger MD, Domingue RP, Fayer MD (1984) Picosecond studies of excitation transport in a finite volume— the clustered transport-system octadecyl rhodamine-b in triton x-100 micelles. J Chem Phys 80(3) 1246-1253. doi 10.1063/1.446802... 

Figure 8. Schematic representation of the micro-environment of a PSD (Rhodamine B octadecyl ester) in an anion sensor before (A) and after (B) extraction of nitrite from the aqueous into the lipophilic membrane phase.

As earlier reported for electrochemical sensing, often the active chromo-phore will be dispersed in a polymeric matrix. For example, Mohr and Wolfbeis reported a nitrate sensor [121] where the active chromophore is a rhodamine B dye which had been modified with an octadecyl side chain to render it hydrophobic and prevent leaching. The dye was dispersed in a plasticised PVC membrane containing a hydrophobic anion carrier (tridodecylmethylammo-nium chloride). On exposure to nitrate, the fluorescence of the dye increased. This membrane, however, only displayed Hofmeister-type selectivity and was also affected by pH. Replacing the quaternary ammonium anion carrier with a palladium phospine chloride carrier led to selectivity for nitrite [ 122], probably due to a preferential interaction between Pd and nitrite ion. 

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