| Metal-enhanced fluorescence(MEF)is derived from the localized surface plasmon resonance(LSPR)effect of noble metal nanoparticles.LSPR is a very unique optical property of metal nanomaterials and an important frontier in the field of nanomaterials resear-ch.The LSPR effect can enhance the:fluorescence signal intensity of fluorescent molecules,improve the sensitivity,accuracy and application range of fluorescence detection methods,and has important application value in the fields of optoelectronic devices,single molecule detection and energy transfer.Based on the study of MEF,Ag@SiO2@CsPbBr3 composite nanoparticles with special morphology and core-shell structure were designed and synthesized by the polyol method,modified Stober method and thermal injection method.By changing the thickness of SiO2,The distance between the Ag nanoparticle and the CsPbBr3 quantum dot is controlled to study the fluorescence spectrum behavior of the quantum dot.The main research contents and conclusions of this thesis are as follows:(1)Preparation and characterization of core-shell Ag@SiO2 composite nanoparticles:Silver nanoparticles(Ag NPs)were prepared by adjusting the reaction time,temperature,PVP molecular weight and concentration by using the polyol method with ethylene glycol as a solvent.Then,using Stober method,tetraethyl orthosilicate(TEOS)was used as the silicon source,and Ag@SiO2 composite nanoparticles were coated on the surface of Ag NPs with different thicknesses of SiO2 to perform amino functionalization.The control method of SiO2 shell thickness was studied and characterized by TEM,SEM and UV-Vis absorption spectroscopy.The results show that the Ag NPs have good dispersibility,regular morphology,particle size of about 60 nm,and the surface is coated with SiO2 layers ranging from 1-55 nm.The surface plasmon resonance absorption peak is 420 nm,and the surface plasmon resonance absorption peak gradually red-shifts as the thickness of the surface-coated SiO2 layer increases.(2)Preparation and characterization of Ag@SiO2@CsPbBr3 composite nanoparticles:Firstly,the thermal injection method was used to prepare CsPbBr3 quantum dots with particle size of 1.3-9.5 nm and emission wavelength from 465-536 nm by controlling the reaction temperature.The effects of synthesis temperature on the properties of CsPbBr3 quantum dots were systematically investigated.The particle size,emission wavelength,half-width,absorption wavelength and quantum efficiency were characterized.The results show that the emission wavelength of CsPbBr3 quantum dots synthesized at high temperature is red-shifted,the half-width is narrow,and the quantum efficiency is high,indicating the synthesis temperature.The perovskite quantum dot crystallization has an important influence.It is concluded that the CsPbBr3 quantum dots will change from orthorhombic to cubic in high temperature.Then,using the successfully prepared core-shell type Ag@SiO2 as the structural unit,the CsPbBr3 quantum dots whose surface exhibits negative conductivity are self-assembled into the surface-positive Ag@ in the tetrahydrofuran solution(THF)by the principle of electrostatic adsorption.On the surface of SiO2 nanoparticles,Ag@Sio2@CsPbBr3 composite nanoparticles were successfully prepared.The effects of preparation conditions on the experimental results were investigated.The relationship between Ag@SiO2@CsPbBr3 composite nanoparticles and SEF effect was discussed by the combination of characterization and theoretical calculation.Through the characterization of its fluorescence lifetime,Ag nanoparticles accelerate the rate of radiant rate of CsPbBr3 quantum dots and increase the fluorescence emission intensity,achieving a 2.6-fold enhancement of the fluorescence intensity of perovskite quantum dots.In summary,by preparing Ag@SiO2@CsPbBr3 composite nanoparticles with core-shell structure and adjusting the distance between Ag nanoparticles and CsPbBr3 quantum dots by changing the thickness of SiO2,efficient fluorescence enhancement can be obtained. |
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