Fluorescence Regulation Of Micro-nano Systems And Application Of Raman Scattering

Recently,the optical properties of micro-nano-materials have attracted more and more interest of researchers,especially in lanthanide-doped upconversion microstructure materials and noble metal nanostructures.The micro-nano-materials can also be widely used in new light sources,high efficiency optical sensors,biological imaging,biological,chemical sensor and catalysis,etc.In this dissertation,the optical signals regulation and enhancement based on the micro-nano-systems are systematically investigated for rare earth fluoride microcrystal materials through a microscopic confocal system.Furthermore,the signals of alloy NPs-catalyzed reaction skinetics are detected by in situ real-time the surface enhanced Raman scattering spectroscopy technology.The main research work is summarized as follow:First,a new design of peculiar-shaped P-NaYF4:Yb3+/Er3+hexagonal microcrystal was prepared via modified hydrothermal method and its upconversion luminescence with adjustable color pattern was studied by near infrared excitation.The unique upconversion fluorescence emission phenomena of flower-like green upconversion luminescence emission pattern from blooming to withering process and directional red emission are presented by simply adjusting the focal point position of the excitation light.The mechanism that determines the unique upconversion luminescence phenomena was investigated systematically.The function of the internal light reflection and waveguide effect with annular microcavity was explored based on the structure characteristic of the hexagonal microplate.Moreover,to obtain the upconversion luminescence enhancement,we also studied the single ?-NaYF4:Yb3+/Er3+ microcrystal deposited on silver films with different thicknesses under the lower excitation power.In addition,a comprehensive analysis based on the rate equations and the numerical calculation |E|2 surrounding Ag films with 3D finite element method,reveals that the upconversion luminescence intensity of the single microcrystal deposited on the silver films enhances drastically with the increased thickness of silver film.These findings provide a unique platform for micro-optoelectronic devices,pattern-changeable three-dimensional color display,biological applications,directional light emission and micro-laser systems.Second,a simple facile synthetic protocol was established for preparation of the monodispersed Au-Ag alloy NPs.These nanoparticals could integrate both good plasmonic property of Ag and the great stability of Au into a single bifunctional entity,which exhibit good catalytic activity and strong SERS signal.The catalytic activity of Au-Ag alloy NPs using reduction of 4-nitrothiophenol by sodium borohydride was chosen as a model reaction.The catalytic reaction kinetics processes were detected and identified through in situ real-time quantitative SERS spectroscopy with high sensitivity.This study offers a new strategy that could be applied for the preparation of other alloy catalysts for diverse uses in synergy effects.Moreover,with the development of SERS-based synergy technology and catalytic products,we believed that the unprecedented improvement in catalytic reactions of aromatic nitro compounds has been finally achieved,which will open a new window for environmental protection.