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Localized surface plasmon resonance spectroscopy of silver nanoparticles and Raman spectroscopy using liquid-core optical fibers: Fundamentals and applications

Posted on:2001-11-16Degree:Ph.DType:Dissertation
University:Northwestern UniversityCandidate:Malinsky, Michelle DuvalFull Text:PDF
The localized surface plasmon resonance (LSPR) of silver nanoparticles fabricated using the technique of nanosphere lithography (NSL) is examined using optical extinction spectroscopy. In the first section of this document, we demonstrated that the wavelength corresponding to the extinction maximum, lambdamax, can be systematically tuned throughout the visible, near-infrared, and mid infrared regions of the electromagnetic spectrum. This unprecedented level of wavelength agility in nanoparticle optical response was achieved by independent manipulation of the nanoparticle height, width, shape, and dielectric environment.; A detailed study of the LSPR of Ag nanoparticles chemically modified with alkanethiols, CH3(CH2)xSH, of varying chain length x = 3--15 is also presented. The significant discovery from this investigation is that lambdamax is extremely sensitive to the presence of adsorbed alkanethiol molecules. Using this discovery, we created a new class of nanosensors that operate by detecting shifts in the LSPR induced by analyte binding events to Ag nanoparticles modified with functionalized self-assembled monolayers.; Additionally, we explored the optical contribution of the substrate to the LSPR of surface confined Ag nanoparticles. For this study, the spectral location of the LSPR in a controlled N2 environment and the LSPR sensitivity to bulk external solvent were measured for Ag nanoparticles fabricated on four different substrates with refractive indices, n substrate, from 1.46 to 1.73. In a controlled N2 environment, lambda max linearly shifted to the red with increasing n substrate. However, little or no systematic dependence correlating the LSPR sensitivity to bulk environment to nsubstrate was observed.; The final chapter of this document described the development of a method that estimates and optimizes the utilizable Raman power delivered by a liquid-core optical fiber (LCOF) waveguide to a spectroscopic instrument. Expressions for the effective fiber length, ze, which is directly proportional to the Raman intensity, were derived for six commonly used scattering configurations. Also, the "Figure of Merit", a term describing the fraction of the Raman light emitted from the LCOF that enters the spectroscopic instrument, is discussed. For a conventional Raman instrument, we concluded that the "Figure of Merit" is inversely proportional to the inner diameter and loss coefficient of the LCOF.
Keywords/Search Tags:Nanoparticles, LSPR, Using, Surface, Raman, Optical, LCOF, Spectroscopy
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