Enantioselective Discrimination of D‐ and L‐Phenylalanine by Chiral Polyaniline Thin Films

Chirality is induced in polyaniline by doping with ( R )‐camphorsulfonic acid (( R )‐CSA). Once de‐doped, polyaniline films cast from solution remain chiral and can discriminate between the D ‐ and L ‐enantiomers of phenylalanine, as the Figure shows: chiral polyaniline appears green when doped with R ‐CSA (a) and blue when de‐doped (b). De‐doped films exposed to D ‐phenylalanine remain blue (c), but turn green in the presence of L ‐phenylalanine (d).