Research Of The Graphene-based Chiral Composites In The Construction Of Electrochemical Recognition Tryptophan Enantiomers

Chirality is not only a basic phenomenon in nature,but also a basic feature of living systems.Many substances in nature have two isomers of（+）-enantiomer and（-）-enantiomer,although their structures are the same,but their properties are quite different.Amino acids are important components in human life activities.A large number of studies have shown that only L-amino acids can be absorbed and utilized by the human body.Therefore,how to distinguish between two chiral isomers has become an upsurge in the current research field.In recent years,electrochemical analysis and identification methods,which have the advantages of high selectivity,high sensitivity,low price and fast detection speed,have become more and more common in the identification of chiral isomers.This thesis takes this as a starting point and uses functionalized graphene as a base material to load a chiral selector to construct a chiral sensing interface to identify Trp isomers.It mainly consists of the following three parts:1.Two chiral composites,RGO-Au/L-Glu and RGO-Au/D-Glu,were synthesized by one-step hydrothermal method.The structure and composition of the chiral composites were determined by SEM,TEM,FTIR and XRD powder diffraction.Then an electrochemical chiral sensing interface was constructed to recognize the Trp isomers.Compared with L-Glu and D-Glu,the chiral sensing interface constructed by RGO-Au/L-Glu/GCE and RGO-Au/D-Glu/GCE significantly increases the recognition efficiency of Trp isomers,indicating that the excellent conductivity of RGO-Au improves the electrochemical activity of the electrode surface.The results showed that RGO-Au/L-Glu had a strong binding ability with L-Trp by UV absorption spectrum and density functional theory.In addition,the chiral sensing interface has good stability and reproducibility,which can be used as an efficient chiral sensing interface for the identification of Trp isomers.2.Compared with polysaccharide chiral selectors,amino acids have fewer chiral sites.Therefore,in order to improve the recognition efficiency,Cu-β-CD with more chiral sites was selected as a chiral selector.By using the conjugated structure of Py,Py can be in situ polymerized into GO lamellar byπ-πinteraction at low temperature reaction,which not only solves the agglomeration effect of GO,but also improves the electrical conductivity of the composite due to the addition of conductive polymer.Then the substrate material and chiral selector were dropped on the surface of the glassy carbon electrode respectively to construct a chiral sensing interface to recognize the Trp isomer.The results showed that the recognition efficiency of Cu-β-CD for Trp isomers was significantly higher than that of L-Glu,and the recognition efficiency of Trp isomers at the chiral interface of RGO/Ppy/Cu-β-CD/GCE was 3.24.The mechanism of chiral recognition was investigated by water contact Angle experiment and UV absorption spectrum,which caused a large amount of D-Trp to be trapped in the cavity of Cu-β-CD,and it was easier for L-Trp to reach the electrode surface through the electrode film.At the same time,the chiral interface has good stability and reproducibility,and has a low detection limit for Trp isomers.3.Although polysaccharide chiral selectors have many chiral sites to improve the recognition efficiency,polysaccharides tend to agglomerate.To solve this problem,Cu-β-CD and L-Lys were self-assembled into a novel chiral selector through coordination to provide a large number of chiral sites.C₃N₄ was synthesized with melamine as the precursor,and RGO/C₃N₄ was prepared by hydrothermal intercalation of GO and C₃N₄ as the substrate material to improve the electrical conductivity and electrochemical activity area of the electrode.The advantages of the two methods were combined to construct an electrochemical chiral sensing interface for the identification of Trp isomers.The results show that the two accelerates the electron transfer through synergistic action,and has a better recognition effect for Trp isomer,and the recognition efficiency is I_L/I_D=4.72.The mechanism of chiral recognition was verified by the water contact Angle,and then the binding constants of the chiral interface and Trp isomer were studied by ultraviolet absorption spectrum to verify that the chiral recognition mechanism was derived from the membrane penetration.The stability and reproducibility of the chiral interface were tested by five groups of independent experiments,and the content of D-Trp and L-Trp in racemic solution could be determined quickly.