Preparation Of Zn(S/Se) Quantum Dots And Their Application In Biological Detection

The toxicity of fluorescent probes is very important for practical application in the field of biosensors.Although CdSe and CdTe quantum dots have been the most widely studied,the biological toxicity of heavy metal Cd limited its application in this field.Therefore,exploring and developing quantum dot materials with good biocompatibility,non-toxicity and harmlessness is a research hotspot in the field of bio-detection,such as ZnS and ZnSe quantum dots.ZnS and ZnSe quantum dots can improve the detection accuracy and stability and expand the range of fluorescence emission by doping,core-shell structure and other means.In this paper,double-emission ZnS QDs and ZnSe:Mn/ZnS QDs were prepared as fluorescent probes for quantitative detection.L-cysteine and mercaptopropionic acid co-capped ZnS quantum dots?QDs?with dual emissions?Em₁=420 nm,Em₂=570 nm?have been successfully synthesized by a one-pot aqueous-phase synthesis method.The intensities of the dual emissions could be controlled by regulating the molar ratio of L-cys to MPA,and the fluorescence color also turned from blue to yellow accordingly.The relationship between the ligands and fluorescence was investigated and the results indicated that L-cys could cause two emissions and MPA improved the emission intensity.In addition,the L-cys-MPA co-capped ZnS QDs showed high photostability under UV irradiation.The ratio fluorescence quantitative detection of dopamine in the concentration range of 0.05-100?mol/L is realized by using the ZnS quantum dots with the ratio of L-cysteine to 3-mercaptopropionic acid of 1:1.The detection limit can reach 18nmol/L.The prepared probe has good selectivity.Water-soluble ZnSe:Mn quantum dots with adjustable fluorescence intensity at 480 and 570nm were synthesized by nucleation doping.The effects of the ratio of precursors of anion and cation,nucleation temperature and doping concentration on the reaction system were studied.The fluorescence intensity and photostability were further enhanced by constructing core/shell structure ZnSe:Mn/ZnS QDs.It was found that the emission peak of Mn²⁺at 570nm had strong anti-interference ability,while those at 480 nm were obviously affected by external environment.Therefore,the luminescence emssion at 570 nm was used for biological detection.The fluorescence probe has obvious fluorescence response to high concentration of dopamine and ascorbic acid,and has successfully realized the quantitative detection of dopamine in the concentration range of 0.05-5?mol/L.Further experiments were carried out to construct a complex system with high concentration of ascorbic acid and ZnSe:Mn/ZnS QDs,which is a"switch on"type fluorescent probe of quantitative detection of L-cysteine in the concentration range of 0.1-1000?mol/L with good selectivity.