Based On The Preparation Of ZnS-doped CdTe Composite Quantum Dots And Its Detection Of Fe²⁺

Quantum dots?QDs?are a novel class of materials in a large family of fluorescent nanomaterials.They have a wide absorption spectrum,long fluorescence lifetime,good structural stability,and high quantum yield.They occupy an important position in the field of light emission.The advantages of quantum dots are not only reflected in disease diagnosis and treatment,biosensing,etc.,but also because of their advantages such as simple preparation,high sensitivity,low hazard,good selectivity,and environmental friendliness,they are favored by more and more researchers.In this thesis,cadmium telluride?Cd Te?quantum dots with an average particle size of 3.13 nm were synthesized by using mercaptopropionic acid?MPA?as ligand,sodium borohydride?Na BH₄?as reducing agent,and water bath reflux method.In the step of preparing Cd Te quantum dots,zinc sulfide?Zn S?is doped to adjust the preparation process,so as to obtain composite Zn S@Cd Te quantum dots with an average particle size of 4.80 nm.Explore the influence of factors such as reflux time,system p H,reaction temperature,reaction material ratio on the fluorescence intensity,and optimize the conditions for preparing quantum dots.It can be seen from the experimental results that the optimal reflux time for preparing composite Zn S@Cd Te quantum dots is 5 h,the optimal system p H is 10.0,the optimal reaction temperature is 100°C,and the optimal reaction ratio of reactants is n(Cd²⁺):n?MPA?=1.0:2.4,n(Cd²⁺):n?Zn S?=7.5:1.0.Taking Rhodamine 6G as a reference,the fluorescence quantum yield?x=38%of the composite Zn S@Cd Te quantum dots is obtained.The composition and structure of quantum dots are analyzed by advanced analytical instruments such as fluorescence spectrophotometer,infrared spectrometer,ultraviolet spectrometer,transmission electron microscope,and X-ray diffractometer.The composite Zn S@Cd Te quantum dots prepared in this experiment can be used as a fluorescent probe for detecting Fe²⁺.The effects of substrate concentration and p H on the detection of Fe²⁺by composite Zn S@Cd Te quantum dots were investigated.The results showed that when the substrate concentration was 0.2mg/m L and the p H was 7.2,it was the best detection condition.Compared with Na⁺,found that the composite Zn S@Cd Te quantum dot has a strong sensitivity for the detection of Fe²⁺in the water,Selectivity and immunity.From the experimental results,it can be seen that the detection range of Fe²⁺for composite Zn S@Cd Te quantum dots is 3-30?M,and the linear equation is finally obtained as F/F₀=-0.01c+1.0202(c is the Fe²⁺concentration in the system,the unit is?M),linear correlation coefficient R²=0.99514.After calculation,the detection limit of Fe²⁺for composite Zn S@Cd Te quantum dots is 1.33?M.