Dynamic analysis of aggregation of methylene blue with polarized optical waveguide spectroscopy.

Polarized optical waveguide (POW) spectroscopy permits analysis of the changing molecular state of methylene blue (MB), including aggregate order and orientation at the waveguide surface. Monomer or dimer, dissolved randomly in MB aqueous solution, tends to aggregate at the waveguide surface during air drying. Furthermore, POW spectroscopy dynamically revealed that MB molecules became oriented vertically to the waveguide surface with increasing aggregation order.