Preparation of l-alanine ethyl ester modified multiwalled carbon nanotubes and their chiral discrimination between d- and l-tryptophan

l-alanine ethyl ester modified multiwalled carbon nanotubes (MWNTs-Ala) were prepared and characterized with FT-IR spectroscopy. The electrochemical behavior of d- and l-tryptophan on the MWNTs-Ala coated electrode was investigated by using cyclic voltammetry. Meanwhile, in order to understand the mechanism of the electrochemical process, the electrochemical behavior of d- and l-tryptophan on the bare glassy carbon electrode and the electrode coated with MWNTs having carboxyl groups (MWNTs-COOH) was also discussed, respectively. The results showed that the electrode coated with MWNTs-Ala could recognize the d- and l-tryptophan chiral isomers due to the introduction of l-alanine ethyl ester on the MWNTs. Furthermore, the enantioselectivity of the MWNTs-Ala coated electrode was studied as functions of the solution pH and scan rate.