Study The Chiral Separation Effect Of Metal Surface By Using Quartz Crystal Microbalance

Most drugs are chiral.However,different chiral drugs may have various physiological effects on the human body.Therefore,chiral recognition has research significance for the study of chiral drugs.Chiral recognition based on metal self-crystalline features is a new and efficient method to distinguish chiral enantiomer,but still stays in the theoretical stage.In this paper,the chiral recognition of amino acid was directly performed on the metal surface of the QCM electrode.The feasibility of this strategy was analyzed from the theoretical and practical perspectives,which mainly includes the following four aspects:（1）Firstly,the basic characteristics of quartz crystals were introduced.The relationship between the mass loaded on the surface and the oscillation frequency of QCM was explained based on the mechanical vibration equation.The electrode surface was analyzed by EBSD technique.The crystal line orientation of the metal surface was studied.The results showed that the maximum chiral and achiral planes of the metal surface were（324）and（223）.（2）Adsorption of chiral amino acids on the metal surface of the QCM electrode was tested in the gas phase.The phenylalanine enantiomers were deposited on the gold surface of electrode by molecular beam epitaxial technique.The adsorption capacity of phenylalanine enantiomers on the gold surface was studied under different temperatures,pressures and deposition times.The results showed that D-phenylalanine prefers to adsorb on the gold surface of the QCM electrode than L-phenylalanine.（3）Adsorption of chiral amino acids on the metal surface of the QCM electrode was tested in the liquid phase.The isothermal adsorption model indicated that D-amino acids were more likely to adsorb on the gold surface.Compared with Au surface,Cu surface has more active sites,which facilitates amino acid adsorption^[1].To study the recognition ability of other metals,the molecular imprinting method was applied to form Cu films through adsorbing a layer of chiral enantiomer on the Au surface and then magnetron sputtering Cu atoms.The results showed that Cu film with D-cysteine imprinting enhanced the recognition ability of phenylalanine and serine enantiomers on the surface.（4）The most chiral planes（324）and achiral planes（223）on the electrode were analyzed by density functional theory（DFT）.The most stable adsorption configurations of amino acid enantiomers on（324）and（223）planes were estimated,and the adsorption energies were calculated.The results showed that the chiral recognition could be achieved on（324）plane,which the phenylalanine recognition is the best.While the chiral recognition could not be achieved on（223）plane.