Construction Of Chiral Gold Nano-SERS Substrate And Study Of Its Enantioselective Recognition Function

In nature,chiral selection is one of the essential laws for organisms to carry out life activities.Chiral molecules with enantiomers have the same chemical formula,but they have different spatial configurations,optical activities,pharmacological properties and so on.Chiral molecules are widely found in human body,drugs and daily chemicals chemicals.Therefore,it is of great significance to develop convenient,rapid and sensitive chiral recognition detection and analysis methods.The commonly used chiral recognition methods mainly include chromatographic method,spectral method and sensor method.However,these methods have the disadvantages of complex operation,low sensitivity and poor molecular specificity.Surface Enhanced Raman spectroscopy(SERS)method has the characteristics of fast analytical speed and high sensitivity,which can make up for the shortcomings of the above methods.However,because a pair of enantiomers has the same Raman spectrum,ordinary Raman spectroscopy instruments can not directly distinguish enantiomers.Therefore,this greatly limits the application of Raman spectroscopy in chiral analysis.In recent years,some studies have shown that SERS substrates with chirality can induce a pair of enantiomers to produce differentiated Raman spectra to achieve chiral recognition.Hence,the construction of metal plasma SERS substrates with chirality provides a new idea to promote the application of Raman spectroscopy in chiral recognition.Most chiral SERS substrates are mainly surface modified by chiral organic molecules for gold and silver nanomaterials and combined with specific chiral molecules to achieve chiral recognition.This work focuses on the development of new chiral gold nanomaterials SERS substrates and the establishment of a new strategy for SERS chiral recognition based on chemical reactions.The main research contents and results are as follows:1.Chiral gold nanoparticles were synthesized by using chiral silica and prepared by high-temperature sintering.As a SERS substrate,the gold chiral nanoparticles were used to recognize cystine enantiomers.The difference of Raman signal intensity gold nanoparticles,the difference of Raman signal intensity between D-cystine and L-cystine is more than 3 times;and the Raman signals between the non-chiral gold nanoparticles SERS substrates are almost the same.Density functional theory(DFT)was used to discuss the recognition principle.It was found that chiral recognition was associated with the molecular orientation of cystine molecules in chiral gold nanoparticles,which resulted in the difference of Raman signal intensity.2.In the process of preparing gold nanoparticles by liquid phase reduction,chiral cysteine molecules were introduced,and cysteine modified gold nanoparticles were synthesized by one step method.Chiral interactions between cysteine and tyrosine enantiomers on the gold surface using these gold nanoparticles as sers substrates.Therefore,the characteristic Raman scattering signal intensity of D-tyrosine and Ltyrosine at 830 cm-1 changes.And the chiral recognition detection of tyrosine is realized.We also tested phenylalanine with SERS,another amino acid similar to tyrosine,and the structure was same with tyrosine.And the SERS results were consistent with those for tyrosine.3.Based on work two,an analytical strategy based on oxidation reaction for SERS identification of dopamine enantiomers was developed.The Raman scattering signal of L-dopamine on the SERS substrate of D-cysteine modified gold nanoparticles and its Raman signal on the substrate of L-cysteine(L-Cys)modified gold nanoparticles are almost the same.Nevertheless,the SERS spectra collected were significantly different by adding the two kinds of gold nanoparticles SERS substrates during the oxidation reaction of L-Dopa,therefore chiral recognition and differentiation by chemical reaction.