Preparation And Performance Characterization Of ?-? Quantum Dots And Silica Composite Materials

Quantum dots are widely used in display devices,solar cells,LED lighting,biological imaging,and detection because of their adjustable emission wavelengths,high quantum efficiency,and high color purity.As the quantum dots decrease in size,the specific surface area increases,and the surface atomic ratio is high,which easily generates surface defect states and reduces efficiency.Therefore,the method of covering the inorganic semiconductor shell layer is commonly used to improve its efficiency and stability.The cladding method commonly used for core-shell structure quantum dots is a continuous ion layer adsorption reaction.The product has excellent optical properties and the shell layer can be precisely adjusted.However,this method is cumbersome and takes a long time,which is not conducive to practical application and promotion.The optical performance of ?-? CdSe/ZnS core-shell quantum dots can currently meet all the optical performance requirements of optoelectronic devices.It is a commonly used quantum dot on the market today.It simplifies the synthesis method and obtains cadmium-based quantum dots with excellent optical properties.Conducive to its further application and promotion.At the same time,further epitaxial coating of silica shells on cadmium-based quantum dots containing heavy metals is conducive to reducing their biological toxicity and facilitating the application of biological imaging detection.In bioimaging detection,Mn:ZnSe-based doped quantum dots,which are also group ?-?,have more application value.They do not contain heavy metal elements cadmium or lead,and their Stokes shift is large,which can avoid reabsorption effects.The resulting energy transfer reduces the effect of energy transfer between multi-colored quantum dots,which is beneficial to improve the sensitivity of biological detection.However,its complex synthetic process limits its practical application.Further,coating the prepared quantum dots with silica can enhance their light transmittance and biocompatibility.The main work of this article is as follows:(1)High quantum efficiency cadmium selenide-based core-shell quantum dots with simple preparation methods:By using single precursor injection method,high activity and low reaction temperature precursor zinc diethyldithiocarbamate(ZDC)is used to generate high-efficiency CdSe/ZnS quantum dots in one step cladding,which simplifies CdSe/ZnS quantum dots.Cladding process.First,when preparing CdSe core quantum dots,CdSe core quantum dots with an emission wavelength of 600 nm were prepared by adjusting parameters such as temperature,time,and concentration.Then,a single precursor injection method was used to quickly perform a layer on the surface of the core CdSe quantum dots.Epitaxial growth of ZnS shells yielded high-efficiency CdSe/ZnS quantum dots with an emission wavelength of620 nm,a quantum efficiency of 90%,and a FWHM of less than 30 nm.On this basis,in order to reduce the heavy metal toxicity of quantum dots,Biocompatibility.The inverse microemulsion method was used to prepare quantum dots@Si O₂ fluorescent microspheres,methylamine was used as a catalyst,and NP-5 was used as a surfactant to prepare CdSe/ZnS@Si O₂fluorescent microspheres of uniform size.Retains more than 60%fluorescence efficiency(2)An environmentally friendly Mn-doped ZnSe quantum dot with a Stokes shift of 180 nm was prepared:The octyl mercaptan+oleylamine sulfide double-shell preparation method was used to simplify the ZnS cladding process of ZnSe-based core quantum dots,shorten the reaction time,and eliminate tedious operations;Tox shifted Mn:ZnSe/ZnS/ZnS core-shell quantum dots.First,Mn:ZnSe core quantum dots with an emission wavelength of 585 nm were prepared by adjusting parameters such as temperature,time,and Mn doping amount.Then,by using the octyl mercaptan+oleylamine sulfur double shell preparation method,the temperature,Further adjustment of the concentration parameters yielded Mn:ZnSe/ZnS/ZnS core-shell quantum dots with a wavelength of 605 nm,a quantum efficiency of 70%,and a Stokes shift of 180 nm.The microemulsion method uses ammonia as a catalyst and NP-5 as a surfactant to prepare Mn:ZnSe/ZnS/ZnS@Si O₂fluorescent microspheres with uniform size,which can retain a fluorescence efficiency of more than 33%,which improves its performance.Possibility of LED and biological applications.