Construction Of Quantum Dot Based Fluorescent Sensor And Its Application In The Detection Of Spermine In Food

Spermine is a kind of polyamine which widely exists in organisms.Spermine plays an important role in maintaining the normal work of cells in organisms,affecting the regulation of DNA,RNA and protein synthesis.The content of spermine in organism is directly related to the canceration of tissues.In addition,spermine also exists in food.Spermine can react with nitrite in food to produce carcinogenic nitrosamine chemicals.The determination of spermine is an important index to evaluate the freshness of food.Therefore,it is of great significance to develop an analytical method with high sensitivity and selectivity for the detection of spermine.Among them,quantum dots(QDs)based fluorescence sensor with the advantages of low cost,fast detection speed,high sensitivity and real-time monitoring has attracted a lot of attention.At present,the QDs based fluorescence sensors for spermine have been reported in the literature,but there are relatively few kinds,and their sensitivity and selectivity need to be further improved.In this paper,water-soluble CdTe QDs and carbon QDs were prepared by a simple method.And a novel fluorescent sensor for the detection of spermine was constructed,which can achieve high sensitivity,high selectivity and real-time online detection of spermine in food.It is mainly divided into the following three parts:1.Water-soluble N-acetyl-L-cysteine(NAC)modified CdTe QDs with excellent luminescent properties were prepared by a one-step reflux method.The non-toxic and biocompatible NAC was used as modifier,sodium borohydride as reducing agent and sodium tellurate as tellurium source.The morphology,size and structure of CdTe QDs were characterized by TEM,HR-TEM,XRD and FT-IR.The optical properties and stability of CdTe QDs were studied by UV-vis absorption and fluorescence spectra.The quantitative detection of spermine was established by fluorescence quenching method.A new fluorescent probe for the detection of spermine was developed.Under the optimized experimental conditions,the linear range of spermine detection was 0-30 ?mol/L,and the detection limit was 0.04269 ?mol/L.The method has good sensitivity and selectivity,and can be used for the determination of spermine vapor in meat.2.Carbon QDs with red fluorescence were synthesized by a solvothermal method.It has been developed into a new fluorescent sensor for the detection of spermine.The carbon QDs were characterized by XRD,XPS,TEM,HR-TEM,FT-IR,UV-vis absorption and fluorescence spectra.It is found that the fluorescence intensity of carbon QDs decreases with the increase of spermine concentration.Under the optimized conditions,the linear range of spermine detection was 0-25 ?mol/L,and the detection limit was 0.010608 ?mol/L.This method can be used to detect spermine vapor in meat,mushroom and milk.3.Stable CdTe QDs with high fluorescence quantum yield were synthesized using mercaptosuccinic acid as a protective agent.The structure and fluorescence properties of CdTe QDs were characterized by XRD,TEM,HR-TEM,FT-IR,UV-vis absorption and fluorescence spectra.The detection of spermine by CdTe QDs was investigated,and the optimal conditions for the detection of spermine were optimized.It is found that the addition of spermine can reduce the fluorescence intensity of CdTe QDs,and cause the red shift of the fluorescence emission peak position of CdTe QDs,accompanied by the fluorescence color change from yellow to red,which is visible to the naked eye under 365 nm UV light.Based on the CdTe QDs modified with mercaptosuccinic acid,a visible fluorescence sensor for the detection of spermine was developed.At the same time,two kinds of portable fluorescent probes,fluorescent test paper and fluorescent film,can be made to realize the real-time online detection of spermine in food.