Two new chiral membranes were prepared by modification of gold nanochannel membranes with D-penicillamine and N-acetyl-L-cysteine and were characterized by scanning electron microscopy and X-ray photoelectron spectroscopy. The effects of key factors such as the gold deposition time, the pH, and the concentration of sodium dihydrogen phosphate on the separation factor are discussed. Chiral resolution of amino acid enantiomers by the chiral membranes was investigated. The experimental results show that the D-penicillamine-modified membrane has good enantioselectivity toward tyrosine and phenylalanine enantiomers, whereas the N-acetyl-L-cysteine-modified membrane has good enantioselectivity toward tyrosine and tryptophan enantiomers. Furthermore, the chiral recognition mechanism was studied by density functional theory. The calculation results indicate that the basic chiral recognition system of D-penicillamine complexes involves only one chiral selector and one selected enantiomer, whereas that of N-acetyl-L-cysteine complexes involves two chiral selectors and one selected enantiomer. Finally, the NH3+ group of D-penicillamine is proved to play an important role in enhancing interactions between complexes and improving enantioselectivity. Graphical abstract Enantioselective interactions between amino acid enantiomers and sulfhydryl-compound-functionalized gold nanochannel membranes.
Keywords: Chiral nanochannel membrane; Chiral resolution; Density functional theory; Recognition mechanism; Sulfhydryl compounds.