Preparation And Application Of Fluorescent Sensors Based On Two Inorganic Nanomaterials

Norganic fluorescent nanomaterials provide many opportunities for the design of fluorescent sensors due to their novel physical and chemical properties.Inorganic fluorescence sensors based on nanomaterials and nano effects are widely used in th e detection of various analytes because of their advantages of fast detection speed,simple operation steps,low cost,strong specificity and high sensitivity,which can be applied to more complex and changeable analysis systems.In this study,two inorganic fluorescent nanomaterials(CuInS₂/ZnS quantum dots and CaF₂:Yb³⁺,Er³⁺upconversion nanoparticles)were used as research objects to construct simple,environmentally friendly and inexpensive fluorescence sensors,which were used for the detection of metal ions and molecules related to disease.The main research contents of this paper are as follows:（1）A turn-off fluorescent probe for determination of Cu²⁺based on CuInS₂/ZnS quantum dots.Firstly,oil-amine coated core-shell CuInS₂/ZnS quantum dots were synthesized by the thermal decomposition method.Water-soluble CuInS₂/ZnS quantum dots with good luminescence performance were prepared by ligand exchange method using glutathione and mercaptopropionic acid as ligands.Based on the strong quenching effect of Cu²⁺on the fluorescence of CuInS₂/ZnS quantum dots,a nano-fluorescence sensor for highly sensitive and selective detection of Cu²⁺was designed.There is a linear relationship between the relative fluorescence intensity and Cu²⁺concentration in the range of 0.5-50μM,the detection limit was 0.43μM,and the sensor has good application effect in practical water samples.At the same time,biocompatibility experiments showed that quantum dots have low toxicity in a certain concentration,and have been successfully applied in vitro cell imaging.（2）A turn-off-on fluorescent probe for determination of AA based on CaF ₂:Yb³⁺,Er³⁺upconversion nanoparticles.CaF₂:Yb³⁺,Er³⁺upconversion nanoparticles were synthesized by the solvothermal method.Then,based on the mixed detection system CaF₂:Yb³⁺,Er³⁺/H₂O₂/Cu²⁺/TMB,an"off-on"fluorescence nanosensor system was designed for ascorbic acid（AA）analysis.In the reaction system,colorless 3,3’,5,5’-tetramethylbenzidine（TMB）can be oxidized by H₂O₂/Cu²⁺to blue oxidized 3,3’,5,5’-tetramethylbenzidine（ox TMB）,which can absorb the fluorescence emitted by CaF ₂:Yb³⁺,Er³⁺upconversion nanoparticles.The fluorescence of CaF₂:Yb³⁺,Er³⁺upconversion nanoparticles at 657nm was greatly weakened.In the presence o f AA,ox TMB can be reduced to TMB,so the fluorescence emission of CaF₂:Yb³⁺,Er³⁺upconversion nanoparticles at 657 nm can be recovered,the color of the solution gradually changed from blue to colorless at the same time,thus achieving the quantitative de tection of AA.There was a linear relationship between the relative fluorescence intensity and AA concentration in the range of 1-30μM,the detection limit was 0.1μM,and this detection method was successfully used for the detection of AA in commercial v itamin C tablets.