Carbon-based? MXene-based Composites For The Electrochemical Chiral Recognition Of Tryptophan Enantiomers

Chirality is widespread in nature.In general,different conformations of enantiomers have similar physical properties but exert different pharmacological activities and chemical properties in different chiral environments.Electrochemical chiral recognition is a new detection technique that has been developed in recent years.The construction of a simple,efficient chiral sensor is a practical guide for electrochemical chiral recognition and detection.This thesis is based on N,S-doped carbon dots(N,S-CDs),three-dimensional N-doped graphene multi-walled carbon nanotubes(NGM)and MXene as substrate materials to construct different chiral sensors for the electrochemical chiral recognition of Tryptophan(Trp)enantiomers.The main three components are as follows.1.Construction of electrochemical sensors(N,S-CDs@(S,S)-CIL/GCE)based on complexes of N,S-CDs and chiral ionic liquids((S,S)-CIL)for the recognition of Trp enantiomers.The combination of N,S-CDs and(S,S)-CIL under electrostatic action is not only beneficial to fully exposed the chiral sites of(S,S)-CIL,but also can effectively reduce the agglomeration of N,S-CDs.Based on the synergistic effect of(S,S)-CIL and N,S-CDs,the selectivity coefficient(I_L/I_D)of N,S-CDs@(S,S)-CIL/GCE for the Trp enantiomers was 2.12.The detection limits of N,S-CDs@(S,S)-CIL/GCE for L-Trp and D-Trp were 0.035?M and 0.084?M,respectively.At the same time,the water contact angle further demonstrated that N,S-CDs@(S,S)-CIL/GCE had a good affinity for L-Trp.2.To further improve the recognition effect,NGM was used as a substrate material.The electrochemical chiral sensor(NGM@(S,S)-CIL/GCE)was constructed by electrodeposition.NGM@(S,S)-CIL/GCE exhibits excellent electrochemical properties and higher enantioselectivity(I_L/I_D=2.26).At the same time,UV-visible spectra and water contact angles demonstrated that NGM@(S,S)-CIL/GCE has a higher affinity for L-Trp.The peak current of NGM@(S,S)-CIL/GCE was linearly related to the Trp enantiomers concentration in the range of 0.01 m M to 5 m M.The detection limits(LOD)of NGM@(S,S)-CIL/GCE for L-Trp and D-Trp were 0.024 m M and 0.055 m M,respectively.In addition,NGM@(S,S)-CIL/GCE can be used to detect L-Trp or D-Trp in real samples(human urine and human serum).The construction of NGM@(S,S)-CIL/GCE also provides an efficient and convenient strategy for chiral identification.3.In the previous two chapters,zero-dimensional materials(N,S-CDs)and three-dimensional materials(NGM)were used as substrate materials,small molecule chiral ionic liquids was used as chiral selective reagents.In the work of this chapter,we constructed a simple electrochemical chiral sensor(MXene@CS/GCE)using a two-dimensional material MXene as the base material and a natural macromolecular polysaccharide-chitosan(CS)as the chiral selection reagent.The enantioselectivity coefficient(I_L/I_D)of the MXene@CS/GCE chiral sensor was 3.14.In the range of Trp enantiomers concentrations from 1.5 m M to 3.5 m M,the peak currents of MXene@CS/GCE showed a linear relationship.The limits of detection(LOD)of MXene@CS/GCE for L-Trp and D-Trp were 0.029?M and 0.056?M,respectively.