Flexible And Adjustable Multi Color Fluorescence Enhancement By Micro-nano Structures

With the development of nano-optoelectronics technology,more and more researchers use micro-nano structures to control the luminescence characteristics of fluorescent materials,and use nano-structures to enhance fluorescence.Not only can they be used for fluorescence detection,but they can also be used for light-emitting devices to obtain high-brightness luminescence.Fluorescence detection technology has the advantages of high sensitivity,convenient detection,and rapid response,which makes it widely used as the leading detection technology in the fields of analytical chemistry,biological science,sensing and medical diagnosis.The technology of enhancing fluorescence emission can increase the sensitivity of fluorescence detection and the brightness of LEDs,and is of great significance in improving the sensitivity of biosensors and the luminescence of light-emitting devices.However,fluorescence detection requires fluorescent probes.Compared with other luminescent materials used as fluorescent probes,quantum dots have a narrower emission spectrum and a wider excitation spectrum,as well as good light stability and biocompatibility.And the advantages of long luminescence time,so that it is often used as a fluorescent probe in fluorescence detection.However,how to use high enhancement factors to flexibly enhance different emission colors is still a problem to be solved.Therefore,it is very important to use quantum dots to achieve high-efficiency fluorescence detection and to be able to flexibly enhance the fluorescence emission of different colors.In this paper,two micro-nano structures that can enhance fluorescence are proposed for fluorescent luminescence with flexible and adjustable colors,and the influence of these structures on the fluorescence luminescence of quantum dots is systematically studied.The main contents are as follows:The first research work proposed a layered flexible structure composed of metal-dielectric-metal,through which the far-field fluorescence direction enhancement of quantum dots was realized.Firstly,the influence of the polarization direction of the quantum dots on the fluorescence emission effect is studied;secondly,the influence of the structure radius,the central angle,the thickness of the metal layer,the thickness of the dielectric layer and the refractive index of the flexible structure on the fluorescence emission effect of the structure is studied.The effect of quantum dots on fluorescence emission when placed in a multi-fold structure;finally,we compared this structure with a metal-dielectric composite structure and a single-layer metal structure.The calculation results show that the maximum fluorescence enhancement effect can be obtained when the inner radius of the structure is 450nm,the thickness of the upper and lower silver films is 40nm,the thickness of the middle dielectric layer is 115nm and the refractive index is 1.52,and the corresponding center angle of the structure is 60°.Compared with the bare light source,when the quantum dots are located in the middle of the structure,the fluorescence enhancement is about 7 times.Compared with single-layer metal and metal-dielectric composite structures,this structure has the best fluorescence far-field orientation enhancement effect.It explains the physical mechanism by which fluorescence can enhance the fluorescence emission of the structure under the action of the metal-dielectric-metal composite structure,and shows that the structure can realize the fluorescence emission with flexible and adjustable wavelength.In addition,this structure has great value for future display technology and flexible light-emitting devices,and has certain guiding significance for the development and application of efficient flexible devices.The second research work proposed a hexagonal close-packed photonic crystal structure,which can realize the enhancement of quantum dot fluorescence emission.First,the effect of photonic crystals with different stacking methods on the fluorescence excitation effect under planar light irradiation is studied;second,the effect of the hexagonal close-packed photonic crystal array structure on the fluorescence emission effect is studied;then the polarization direction of the perovskite quantum dots is studied.The influence of structural fluorescence emission;finally,the relationship between fluorescence emission in photonic crystals and the size of photonic crystal microspheres is studied.Compared with the quantum dots located on the glass substrate,the photonic crystals in a hexagonal close-packed manner can increase the fluorescence emission of the perovskite quantum dots by about 8 times.At the same time,the photonic crystal substrate makes the fluorescence emission of the perovskite fluorescent quantum dots in the visible light band appear multiple peaks,which clarifies the physical mechanism of the interaction between the photonic crystal structure and the perovskite nanocrystals.This research can not only realize fluorescence detection with flexible and adjustable wavelength,but also has important significance for the development of perovskite LED.