Surface Plasmon Coupled Directional Emission Fluorescence Spectroscopy

Surface Plasmon Coupled Directional Emission (SPCDE)is a novel surfaceenhanced fluorescence method based on the near-field interaction of excitedfluorophores with surface plasmon on the thin metal films.SPCDE displays uniqueadvantages which include strong directional emission,unique polarization,background rejection and wavelength resolution.Therefore,it has a promising andwide application prospect in the biological detection and interface analysis.Thisdissertation focuses on the design of instrumental systems for SPCDE fluorescencemeasurement,the investigation of relevant theoretical and experimental research andthe applications in biochemistry.The dissertation consists of six chapters.In the first chapter,the development of surface plasmon coupled directionalemission was reviewed.Surface enhanced fluorescence spectroscopy techniques,theoretical principle and properties of Surface Plasmon Resonance and SPCDE,theresearch progress and application of SPCDE in biochemistry were described in detail,then the plans for the dissertation were put forward.In the second chapter,an instrumental system for surface plasmon coupleddirectional emission technique was developed in a laboratory-constructedspectrofluorimeter.This setup can get more information from excitation spectrum,ascompared SPCDE system with laser light source.The theoretical calculation andexperimental results showed that SPCDE was the coupling of the surface plasmonsand excited fluorophores on a thin metal film,resulting in a radiation of surfaceplasmons into the higher refractive index media,which showed highly directional andpolarized emission.The properties of background rejection and wavelength resolutionby selecting the observation angle were demonstrated.In the third chapter,a micro-spectrometer of SPCDE was designed with modifiedcommercial laser pointer as light source.The experimental results revealed theinstrument had good advantages,such as simple construction,convenient operationand low cost.In this study,the different properties of two surface enhancedfluorescence methods between surface plasmon field-enhanced fluorescence and surface plasmon coupled directional emission were compared.In the fourth chapter,SPCDE studies have been firstly successfully extended toiron which was an important transition metal.Theoretical Fresnel calculationsperformed in the ultraviolet to near-infrared spectral range (355-1088nm)predictedthe near-field generation of surface plasmons in 25nm iron thin films.The use of ironfilms in SPCDE to generate highly polarized and directional emission wasdemonstrated by experiments.Both theoretical calculations and experimental resultsshowed that coupled fluorescence through iron films occurred over a narrow range ofangles.This suggested that compared with gold films,where there was a strongdependence of emission angle with coupling wavelength,"fixed angle"geometriescould be used over a broad range of wavelength applications on iron films.In the fifth chapter,surface plasmon coupled directional emission based onconformational switching signaling aptamer was studied.Using the aptamer as bothrecognition and signaling elements,we firstly proposed the combination of theenhancement of SPCDE and the quenching by metal to detect thrombin.Bycomparing different chemical methods for the immobilization of aptamer,biotin-avidin method was finally chosen.The enhanced directional fluorescenceemission of signaling aptamer was observed due to the binding of a target thrombinwith aptamer which induces conformational switching.The polarization and angulardistribution of the observed emission demonstrated that the fluorescence enhancementwas due to surface plasmon.In the sixth chapter,the innovation of the study was concluded and the prospectof this research was given.