Electrochemical chiral interface based on the Michael addition/Schiff base reaction of polydopamine functionalized reduced graphene oxide

A novel approach for the fabrication of chiral sensing platform via the Michael addition or Schiff base reaction between functionalized graphene with polydopamine (rGO-PDA) and L-lysine (L-Lys) was first put forward. GO can be modified and reduced simultaneously via using dopamine. By utilizing catechol functional group on PDA, L-Lys combined with rGO-PDA via the Michael addition or Schiff base reaction. Michael addition reaction occurred between electrophilic conjugate system (L-Lys) and nucleophilic negative carbon ion (rGO-PDA). We firstly synthesized the L-Lys copper (II) (L-Lys-Cu) complex to protect the chiral sites on L-Lys. The terminal amino group on L-Lys-Cu will interact with rGO-PDA by Michael addition or Schiff base reaction to synthesize rGO-PDA/L-Lys copper (II) composite. The copper ions in rGO-PDA/L-Lys copper (II) composite were removed to prepare rGO-PDA-L-Lys chiral composite, which was served as electroactive materials to discriminate tryptophan (Trp) enantiomers via electrochemical method. The results showed that the rGO-PDA-L-Lys showed better affinity for D-Trp than L-Trp owing to the formation of diastereomeric complexes between enantiomer (D-Trp) and selector (L-Lys). Besides, the proposed rGO-PDA-L-Lys showed great application potential in actual samples.