Analysis And Application Of The Fluorescence Sensor Based On The Quantum Dots Loaded On The Molecular Imprinted Polymer For The Determination Of Phenolic Substances In The Traditional Chinese Medicine

Traditional Chinese medicine is the national medicine of our country.It has the advantages of small side effects,easy use and definite curative effect.It is gradually recognized and accepted by the world.Among them,Chinese medicines containing phenolic substances are one of the most widely used Chinese medicines for various diseases.Its unique antioxidant,antibacterial,anti-cytotoxic and anti-inflammatory properties play an important role in the prevention,diagnosis and treatment of diseases.However,overdose of phenolic drugs may cause adverse physiological reactions to the human body.Therefore,it is necessary to accurately detect the phenolic drugs in the traditional Chinese medicine to ensure drug safety and human health.Quantum dots（QDs）,as an emerging fluorescent nanomaterial,have the characteristics of high luminous efficiency,excellent light stability and easy synthesis.Combining quantum dots with molecularly imprinted polymers can improve the stability of quantum dots and the selectivity to target drugs.Therefore,this paper constructed a fluorescent sensor based on quantum dot-molecularly imprinted polymer for the analysis and detection of erucic acid,rhein and baicalin.The research content is as follows:（1）Ratiometric fluorescence sensor based on graphene quantum dots and manganese-doped zinc sulfide quantum dots for selective determination of erucic acidGraphene quantum dots（GQDs）and manganese-doped zinc sulfide quantum dots（Mn-ZnS QDs）were synthesized by the pyrolysis method and the one-pot method,respectively.Using sinapic acid（SA）as a template molecule,the sol-gel method was used to synthesize a core-shell probe（MIPs@Mn-ZnS/GQDs@SiO₂）with molecularly imprinted cavities from double quantum dots.The blue GQDs coated with silica are used as the stable internal standard signal,and the orange Mn-ZnS QDs are used as the response signal.Under excitation with a wavelength of 310 nm,MIPs@Mn-ZnS/GQDs@SiO₂ emits two independent fluorescence peaks at 445 nm and 580 nm,respectively.Sinapinic acid can selectively enhance the fluorescence intensity at 445 nm and has a strong quenching effect on the fluorescence at 580nm.It is calculated that the logarithmic ratio of the fluorescence intensity at 580 nm and 445nm has a good linear relationship with the concentration of SA,the linear range is between 9-81 n M,and the detection limit reaches 0.84 n M（S/N=3）.At the same time,by directly observing the color transition of the fluorescent probe,the erucic acid can be determined visually.Finally,the probe was successfully applied to the detection of SA in Chinese medicine white mustard seed and Tinglizi.（2）Ratiometric fluorescence sensor based on double perovskite quantum dots synthesized by in-situ hydrolysis method for selective determination of rheinThe perovskite quantum dots with green fluorescence and red fluorescence were synthesized by in-situ hydrolysis.By adjusting the reaction time,experimental temperature and concentration conditions,the stability of quantum dots is optimized.Using rhein（Rhein）as the template molecule,double quantum dots were synthesized by sol-gel method with a molecularly imprinted cavity core-shell structure probe（MIPs@RPQDs/GPQDs@SiO₂）.Among them,green fluorescent perovskite quantum dots（GPQDs）are used as internal standard signals,and red fluorescent perovskite quantum dots（RPQDs）are used as response signals.Under excitation with a wavelength of 360 nm,MIPs@RPQDs/GPQDs@SiO₂ emit two stable and independent fluorescence peaks at 520 nm and 695 nm,respectively.Rhein can specifically quench the red fluorescence at 695 nm without affecting the fluorescence intensity at 520 nm.It is calculated that the ratio of fluorescence at 695 nm and 520 nm has a good linear relationship with the concentration of Rhein,the linear range is between 15-135 n M,and the detection limit is 1.42 n M（S/N=3）.Moreover,the drug can be detected by directly observing the color transition of the fluorescent probe by visual observation.In addition,the probe was applied to the detection of Rhein in the traditional Chinese medicine rhubarb,with satisfactory results.（3）Selective determination of baicalin based on graphene quantum dots modified by dihydroxy functional groupsThe graphene quantum dots（GQDs）with carboxyl structure were synthesized by heating method.The surface carboxyl functional group of GQDs and the amino group of dopamine（DA）are subjected to an amide reaction to form a new type of fluorescent probe with a dihydroxy structure（GQDs@DA）.Using Baicalin（BAI）as a template molecule,GQDs@DA was further synthesized by a sol-gel method to a highly selective probe with molecularly imprinted cavities（MIPs@DA-GQDs@SiO₂）.Under excitation with a wavelength of 360 nm,MIPs@DA-GQDs@SiO₂ emits a stable fluorescence peak at 460 nm.BAI can bind MIPs@DA-GQDs@SiO₂ sensitively and quickly,and then quench the fluorescence generated at 460 nm.Through calculation,the fluorescence intensity quenched at 460 nm has a good linear relationship with the concentration of baicalin,the linear range is between 10-100 n M,and the detection limit is 2.32 n M（S/N=3）.The probe was applied to the detection of BAI in actual samples of traditional Chinese medicine Scutellaria baicalensis Georgi,and the experimental results were consistent with the expected results.