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).