Tailoring And Applications Of Surface Plasmon Resonance In Metal Nanoparticles

In the last decade, the field of plasmonics has emerged as a rapidly expanding new area for materials and device research. This is a result of the large array of tools that have become available for nanoscale fabrication and nanophotonics characterization, and also because of the availability of powerful electromagnetic simulation methods that are critical to understanding and harnessing plasmon excitations. Since the first application of the localized surface plasmon resonance (LSPR) phenomenon for sensing in1980s, this method has made great strides both in terms of instrumentation development and applications. Studies are starting to appear illustrating the plasmon focusing, plasmon-exciton coupling, nanoscale wave guiding, surface enhanced spectroscopy, nanoscale switches, LSPR sensor, plasmonic lasers, plasmonic resonance energy transfer, Photothermal therapy, super-resolution imaging below the diffraction limit, optical logic operations and materials with negative refractive index. Although the research of plasmonic has been great developed, the simple progress, low cost, high efficient and industrial application are still challenges. In this dissertation, we developed a kind of multifunctional nanoparticles for cell imaging and two novel approaches for the high sensitive and selective molecule recognition. Moreover, based on the molecular engineering principles and the research on dynamic progress of LSPR, we proposed and experimentally demonstrated that the LPSR could be efficiently suppressed.The dissertation is composed of5chapters.In Chapter1, we first describe the optical response of metal nanoparticles in detail to explain the origin of plasmons. The application of LSPR is then discussed with respect to enhancements Raman scattering, fluorescence, and the LSPR sensor. A brief description of the content and significance of the dissertation is given to end the chapter.In Chapter2, a facile and effective approach to synthesize Au nanoparticle encapsulated3,4-dihydroxy-L-phenylalanine monodisperse hybrid nanospheres (Au@DOPA) has been developed. The obtained Au@DOPA core-shell nanospheres have not only good biocompatibility, but also unique optical properties provided by the embedded Au nanoparticles. It has been demonstrated that Au@DOPA core-shell nanospheres can be internalized by human vascular smooth muscles cells (HVSMC) and breast cancer cells and hence act as a novel optical contrast reagent in tumor cell imaging by optical microscopy. The obtained materials could find potential applications in other biomedical-related areas such as photothermal therapy and drug delivery.In Chapter3, we have developed a highly selective, sensitive, convenient, rapid and label-free detection of TNT based on the plasmonic resonance energy transfer (PRET) between Meisenheimer complex (formed by cysteine and TNT) and gold nanoparticles (GNPs) in aqueous solution. The detection limit for analyzing TNT by this method is down to1nM concentration.In Chapter4, a silver nanoparticle based surface-enhanced resonance Raman scattering (SERRS) probe for ultrasensitive and selective indirect detection of formaldehyde has been developed. In this work, the detection and quantification of formaldehyde is realized by detecting the product of Hantzsch reaction because of the specificity of the Hantzsch reaction for formaldehyde under mild reaction conditions. The detection limit reaches as low as10-11M, which much lower than the traditional acetylacetone (acac) colorimetric method. The enhancement factor (EF) is estimated to be approximately1×109. Furthermore, spiked test implies that the probe can also be used to detect formaldehyde in a real environmental sample without much interference. Our study opens a new avenue toward the indirect SERS detection method in the monitoring of environmental contaminants.In Chapter5, we experimentally demonstrate that a well-designed transparent H-aggregate shell can effectively suppress the localized surface plasmon resonance of a gold nanoparticle. It results from the ultrafast hot electron transfer from the gold nanoparticles to the dark state of the transparent H-aggregates that effectively damps the surface plasmon excitation. A high photocurrent is generated from the Au@CB H-aggregates, strongly supporting our proposed ultrafast electron transfer process. This strong coupled Au@H-aggregate hetero-nanostructure could find potentials in surface plasmon-driven, hot-electron solar cells and surface catalytic reactions.