Polarized optical waveguide spectroscopy: Effective tool to analyze adsorption process of dye molecules

Real time changes of the molecular orientational state are readily analyzed with polarized optical waveguide (POW) spectroscopy. Assembly or orientation of over 20 different dye molecules in solution have been analyzed during air-drying. The dynamic behavior of dyes including both orientational direction and degree of aggregation has been discussed with the key group structures of dyes. We suggest that certain interaction between dimethylimino residue of dyes and silanol residue of the waveguide surface should be responsible for these orientational changes. Furthermore, greater aggregation of these dyes tended to give rise to perpendicular orientation on the waveguide surface.