Construction And Properties Of Novel Fluorescent Switching With Zinc Containing Quantum Dot And Diarylethene

As a new generation of semiconductor nanomaterials,quantum dots have a particle size between 1-10 nm.Due to the special structure of quantum dots,it produces surface effect,quantum size effect,dielectric confinement effect and quantum tunneling effect.It has different physical and chemical properties from general bulk materials(unique tunable photoluminescence performance,high light stability,biocompatibility,small size,etc.),which has attracted more and more attention from the scientific workers.Among many organic photochromic materials,diarylethenes are ideal photochromic molecules due to their excellent thermal stability and fatigue resistance,which has great potential development in optical switches,sensors and other fields.Therefore,many researchers take advantage of the special properties of diarylethenes,it has become a novel research hotspot to construct a new reversible fluorescent switching using diarylethenes to regulate the fluorescence of quantum dots through photochemical reactions under light stimulation.In present study,we have designed and prepared kinds of zinc-containing quantum dots,which were ZnS?ZnSe?ZnO quantum dots respectively.The crystal structure and particle size of quantum dots were identified by XRD characterization method,after reasonable molecular design,and three new quantum dot and diarylethene fluorescent switching with quantum dots as fluorescent donors and diarylethenes as receptors were constructed,then the properties of the fluorescent switching were systematically studied.The main research contents of this thesis are as follow:1.ZnS quantum dots were prepared by organic solvent synthesis method.Synthesizing diarylethenes with better switching performance,and its absorption peak of the closed-ring state overlapped with the emission peak of the prepared ZnS quantum dots,then,a light-controlled fluorescent switching system was constructed through two components that were ZnS quantum dots and photochromic diarylethenes1 o.Upon irradiation with UV light,the fluorescent intensity of the system decreased significantly,accompanying the color of the solution changed from colorless to pink,upon irradiation with visible light,the fluorescent intensity and color were returned to the initial state of the solution.The “on” and “off” states of the fluorescence of ZnS quantum dots can be switched mutually upon irradiation with UV light and visible light,and the diarylethenes 1o can successfully regulate the fluorescent intensity of ZnS quantum dots.2.ZnSe quantum dots were prepared by organic solvent synthesis method,and ZnSe quantum dots-diarylethene fluorescent switching was constructed by using two components that were ZnSe quantum dots and diarylethenes 1o.Upon irradiation with UV light,the color of the solution changed from light yellow to pink,and the fluorescent intensity of the system decreased greatly,the fluorescent intensity and color of the solution were restored to the initial state upon irradiation with visible light.Diarylethenes 1o can effectively regulate the fluorescent intensity of ZnSe quantum dots,so the strategy of constructing ZnSe quantum dots/diarylethene based fluorescent switching system was feasible.Moreover,a logic circuit was designed by the fluorescence intensity at 476 nm as output and the diarylethenes and UV/vis lights as inputs.3.ZnO quantum dots were prepared by sol-gel method,Synthesizing diarylethene molecules with-COOH functional group and better switching performance,and its absorption peak of the closed-ring state nearly completely overlapped with the emission peak of the prepared ZnO quantum dots,the solution of the diarylethenes 2o was mixed with the ZnO quantum dots solution in a certain amount to construct ZnO quantum dots and diarylethene fluorescent switching.Upon irradiation with UV light,the fluorescence of the system is almost completely quenched,accompanying the color of the solution changes from colorless to purple.On the contrary,upon irradiation with visible light,the color and fluorescent intensity of the solution were returned to the original state.Diarylethenes 2o can efficiently tailor the fluorescent intensity of ZnO quantum dots.And upon alternating irradiation with UV and visible lights,the fluorescent intensity of ZnO quantum dots can be modulated repeatedly.Moreover,a logic circuit was designed with the fluorescence intensity at 568 nm as output and the diarylethenes and UV/vis lights as inputs.