Fig. 4. a) UVevis spectrum of a 50 mM aqueous MB solution. b) UVeVis spectrum of an
empty quartz cuvette previously equilibrated with a 50 mM MB solution. The cuvette
was washed with a small amount of water and left dripping for 5 min following its
treatment with MB. This spectrum represents the transmission UVeVis spectrum of
MB adsorbed on quartz. c) The same as b), but in this case a 1.0 mM MB solution was
used. All spectra are normalized to the absorbance measured at 664 nm. This transformation
magnifies spectra b) and c) ca. 10-times compared to spectrum a). The absorption
peak of the MB monomer at 664 nm dominates spectra a) and b), and the
peak at 612 nm is characteristic for the of the MB dimer in spectrum c).