Construction Of The Different Chiral Interfaces For The Electrochemical Recognition Of Amino Acids And Its Derivatives

Chirality is an essential and universal aspect of nature.Many chiral objects such as amino acids,proteins,sugars and DNA are caused by the tetrahedral geometry of sp3-hybridized carbon with four different substituents,these mirror images can not be superimposed on its originals.Enantiomeric molecules usually display different biological activity and pharmacological behavior.Therefore,the research of chiral identification has important theoretical and practical significance in the fields of chemistry,science,food and pharmacology.And the development of fast,sensitive,accurate and low-cost chiral analysis method is the research target of chiral recognition.Recently,numerous technologies such as chromatography,fluorescence,colorimetric analysis,quartz crystal microbalance and electrochemistry are employed for the chiral recognition.Among these,electrochemical approach with low cost,rapid detection and high sensitivity receives wide spread attention.In the process of designing electrochemical chiral recognition,the recognition efficiency is greatly affected by the way of the chiral electrochemical interface construction.Hence,the carbon nanomaterials?such as multi-walled carbon nanotubes,single-walled carbon nanotubes,carbon nanohorns?with high specific surface area and metal nanomaterials?suah as gold,palladium,platinum,nickel,copper?with excellent electrocatalytic activity have been applied in the experiments.With the help of chiral selector cyclodextrin,macrocyclic antibiotic and dipeptide,the different chiral interfaces for the chiral recognition tryptophan,tyrosine and mandelic acid enantiomers have been constructed.The major works are as follows:1.An electrochemical chiral nanocomposite has been prepared by modifying a glassy carbon electrode?GCE?with amino-modified?-cyclodextrin?NH₂-?-CD?,gold-platinum core-shell microspheres?Au@Pt?,polyethyleneimine?PEI?,and multi-walled carbon nanotubes?MWCNTs?via electrostatic adsorption.The modified GCE was applied to the voltammetric determination of tryprophan?Trp?enantiomers.The Au@Pt enable an effective immobilization of the chiral selector and enhance the electrochemical performance.Transmission electron microscopy?TEM?,scanning electron microscopy?SEM?,Fourier transform infrared spectroscopy?FTIR?,UV-vis spectroscopy and electrochemical methods were used to characterize the nanocomposite.Trp enantiomers were then determined by differential pulse voltammetry?DPV?,and the significant difference of peak current was observed between L-Trp and D-Trp.The contact angle experiment was used to explain the mechanism of the recognition.The results indicated that the synthesized chiral nanocompsite can be used to recognize the Trp enantiomers.2.A facile and sensitive chiral analysis for the recognition of tyrosine?Tyr?enantiomers has been designed based on teicoplanin?Tei?and a flower-like nanocomposite which consisted of copper-platinum core-shell microspheres and single-walled carbon nanotubes-molybdenum disulfide?Cu@Pt/SWCTNs-MoS₂?.The flower-like nanocomposite was employed to immobilize chiral selector Tei and improve the experimental electrochemical performance.The nanocomposite was characterized via SEM,TEM,energy-dispersive x-ray?EDX?,Raman spectrum,FTIR,water contact angles and electrochemical methods.The interaction between Tyr enantiomers and the modified electrodes has been determined via DPV.Density functional theory?DFT?was also used to optimiz the reaction structure and explore the recognition mechanism.The results exhibited enantioselective interaction between constructed chiral interface and Tyr enantiomers,and a stronger interaction was obtained from L-Tyr than D-Tyr.3.A chiral nanocompsite through assembling?-glutamyl cysteine dipeptide to NiAuPd hollow nanospheres anchored nitrogen-doped carbon nanohorns?Glu-Cys/NiAuPd/N-SWCNHs?has been prepared on glassy carbon electrode?GCE?for detection and identification of mandelic acid?MA?enantiomers.The microstructure and component feature of manufacturing chiral nanocompsite were analysed via SEM,EDX,TEM,FTIR,contact angles and electrochemical methods.DPV technology was adopted to explorated the interactions between the chiral nanocompsite modified electrodes and MA enantiomers.The results indicated that the chiral nanocompsite displayed selective interaction with MA enantiomers,and a stronger interaction was realized from R-MA.