The crystals functionalized with the two dyes are dichromic under polarized light (Figure ). The sodium fluorescein saturated crystals were loaded with sodium resorufin for 1 hour (to have a relative low concentration of the dye in the smallest channels) and analyzed using polarized light. Depending on the angle of the incident light viz-a-viz the crystallographic axis, the crystals are either purple (parallel) or yellow (perpendicular).