Figure 2: THF-specific solvatochromism.
(a) Photographs of solvent-exposed unprotected (top) and PAA-protected (middle) PCDA-derived PDA films. Fluorescence microscope images of the solvent-treated PAA-protected PDA film are also displayed (bottom). Photographs were taken 1 min after adding a drop (ca. 100 μl) of each solvent to the top of the film. (b) Absorption spectra of PAA-protected PDA film upon exposure to various solvents. (c) Film thickness as a function of distance before (blue line) and after (black line) PAA protection. The fluctuating red line is obtained after exposure of the PAA-protected PDA film to THF. (d) Plots of PDA chromic power versus PAA penetrating power for various solvents tested. (e) Plots of colorimetric response time and film thickness as a function of concentration of protective PAA.
