The Study Of Chiral Pollutants In The Environment Based On Fluorescence Spectrum

Chirality is one of the basic properties.The structural core of a chiral compound is an asymmetric carbon atom,the chiral enantiomer forms a mirror image.Its physical and chemical properties are almost the same,but they can never overlap.All things in the universe often prefer only one enantiomer,forming a "chiral homogeneity" dominated by a single enantiomer.For example,the alpha-amino acids that make up proteins in life are basically left-handed,while the nucleic acids in nature show the opposite optical rotation.The selective differences between chiral enantiomers in the anisotropic environment cannot be ignored,especially the different biological effects in the metabolism and regulation process of the organism may lead to the "three causes"(carcinogenic,mutagenic and teratogenic)abnormalities.When chiral pollutants in the environment accumulate in organisms through migration and transformation between organisms,it will seriously threaten the life and health of organisms.Therefore,the analysis and research on chiral pollutants in the environment is of great importance.However,the separation and analysis of chiral enantiomer pollutants,or the simultaneous determination without separation,or the analysis of their selective behavior in the environment is the focus and difficulty of environmental analysis.Based on this,this paper takes arginine,carnitine and propranolol as research objects,aptamers of nucleic acid as biosensors,gold nanoparticles and semiconductor quantum dots as probe reagents,and use fluorescence spectrophotometry to explore new methods for chiral recognition of these chiral enantiomer pollutants.In this paper,the fluorescence spectrum characteristics of each system and its influencing factors,optimal experimental conditions,selective experimental methods and the analysis and application of actual samples based on fluorescence spectrometry were investigated.This paper was completed under the support of the National Natural Science Foundation of China(No.21875015;No.21475014).The main research contents are as follows: 1.An aptamer-based fluorescence bio-sensor for chiral recognition of arginine enantiomers.Using aptamer(Apt)bound gold nanoparticles(AuNps)as biosensor and modifing fluorescein(FAM)at one end of the aptamer,a sensitive,fast and simple method for chiral recognition of arginine(Arg)was established.Transmission electron microscopy(TEM),fluorescence spectra and uv-vis spectra were used to characterize the synthesized AuNps and the combined complexes(Apt-AuNps).The Apt modified by FAM had a strong fluorescence signal,then D/ L-Arg was directly added into it,the spectral signal did not change significantly.But when AuNps joining into Apt solution,fluorescence intensity of the system decreased,then added D-arginine and L-arginine,showed different degrees of fluorescence intensity recovering,L-Arg recovered more than D-Arg.Using this method can realize chiral recognition of arginine enantiomer and quantitative determination,the detection range are 0-300-nm and 0-400 nm respectively,detection limit(3 sigma/k)are 0.9939 and 0.9952.The experiment also optimized the reaction conditions,The optimal pH value was 7.2,the optimal concentration of gold nanoparticles was 10 nM,and the optimal concentration of FAM-Apt was 60 nM.The optimal reaction time at the fluorescence recovery stage was 40 min.Finally,the method was applied to the determination of actual samples(urine),the experimental results were satisfactory.2.Chiral recognition of carnitine enantiomers based on CdTe quantum dots which modified by Graphene oxide In this experiment,graphene oxide was successfully used as one of the ligands to modify the surface of CdTe QDs.The GO-CdTe QDs quantum dots were used as fluorescent probes to establish a simple and convenient fluorescence spectroscopy method for the detection of chiral carnitine.The synthesized graphene-modified CdTe QDs were characterized by TEM,FTIR and fluorescence spectra,by analyzing the results of the synthesized GO-CdTe QDs,they were relatively successful.Due to the unique properties of GO,D-carnitine enhanced the fluorescence spectral signal of GO-CdTe QDs system after the addition of D-carnitine,while L-carnitine weakened the spectral signal of the system.Therefore,this method can not only detect D-carnitine,but also quantitatively determine L-carnitine.The conditions and influencing factors for the experiment were investigated,and the optimum conditions were determined.The result of the experiment is satisfactory.3.Chiral recognition of arginine enantiomers based on N-acetyl-L-cysteine-coated CdTe quantum dots Chiral recognition of arginine enantiomers was successfully achieved by fluorescence spectrometry using n-acetyl-l-cysteine coated CdTe quantum dots as fluorescent probes.The fluorescence intensity of N-acetyl-L-cysteine CdTe quantum dots is weak,when added D-arginine and L-arginine,interesting changes about the fluorescence signals appeared,where D-arginine make system fluorescence intensity enhancement,and L-arginine on fluorescence intensity almost unchanged,based on this phenomenon,chiral recognition of arginine enantiomers and quantitative determination of D-arginine is feasible.Meanwhile,the experimental conditions and influencing factors were optimized,including reaction time,acidity of the system,and the amount of CdTe quantum dots coated with n-acetyl-l-cysteine.In addition,the reaction mechanism of the system and the reason for the difference of spectral signals are discussed.Finally,the standard recovery experiment is applied in practice,and the result is satisfactory.4.Chiral recognition of propranolol enantiomers based on N-acetyl-Lcysteine-coated CdTe quantum dots For the determination of chiral enantiomers,the technique of separation first and then determination is mature,and simultaneous determination without separation is the focus of selective analysis of pollutants in the environment.In this paper,N-acetyl-L-cysteine-coated CdTe QDs(NALC-CdTe QDs)was successfully used to simultaneous determine propanolol enantiomers,and this method was sensitive,rapid,low-cost and operable.Based on this,chiral recognition and simultaneous determination of propranolol enantiomers can be achieved by fluorescence spectrometry(FL).The fluorescence signal of NALC-CdTe QDs itself is very strong,but when R-propranolol and S-propranolol are added,the fluorescence signal is weakened,and S-propranolol makes the fluorescence signal of the system more weaker.Simultaneous determination of R/S-propranolol was carried out based on the different degree of fluorescence signal attenuation.After investigating the experimental conditions and influencing factors,the optimal conditions were optimized to obtain a good linear correlation,and the method was applied to the detection of R/S-propranolol in practical samples with satisfactory results.