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dc.contributor.advisorMeissner, Kenith E.en_US
dc.contributor.advisorCote, Gerard L.en_US
dc.creatorBeier, Hope T.en_US
dc.date.accessioned2011-02-22T22:24:10Zen_US
dc.date.accessioned2011-02-22T23:47:46Z
dc.date.available2011-02-22T22:24:10Zen_US
dc.date.available2011-02-22T23:47:46Z
dc.date.created2009-12en_US
dc.date.issued2011-02-22en_US
dc.date.submittedDecember 2009en_US
dc.identifier.urihttp://hdl.handle.net/1969.1/ETD-TAMU-2009-12-7507en_US
dc.description.abstractNew methods of biological analyte sensing are needed for development of miniature biosensors that are highly sensitive and require minimal sample preparation. One novel technique employs optical resonances known as Whispering Gallery Modes (WGMs). These modes arise from total internal reflection of light at the internal surface of a high index microsphere within a low index medium and produce an evanescent field that extends into the surrounding medium. The WGMs produce multiple narrow spectral peaks that shift position with variations in the local index of refraction sampled by the evanescent tail of the WGMs. To excite these WGMs, we embed quantum dots (QDs) in the periphery of polystyrene microspheres to serve as local light sources. By coupling emission from the QDs to the WGMs, the sensors can be excited and interrogated remotely and, by monitoring the shift of multiple resonance modes, may provide higher sensitivity and accuracy compared with similar techniques. The high refractometric sensitivity of the WGMs offers potential for trace detection of molecules adsorbed onto or bound to the microsphere sensor elements. The sensitivity of these sensors is demonstrated by monitoring the wavelength shift of multiple resonant modes as bulk index of refraction is changed. The potential for targeted biosensing is explored through addition of a protein that adsorbs to the microsphere surface, thrombin. Microsensor response in all cases demonstrated increased sensitivity over theoretical predictions. Models based on Mie theory and continuity of the radial functions across the sphere-media interface were used to model the location, Q-factor, and sensitivity of the WGMs in microspheres by considering the embedded QDs as a high index outer layer. This model was used, along with estimates of the QD-layer index and penetration depth, to relate the locations and sensitivities of the modes to our experimental results with strong agreement between the two. In all, these microspheres demonstrate feasibility for use as remote microsensors with sensitivities rivaling current techniques.en_US
dc.format.mimetypeapplication/pdfen_US
dc.language.isoen_USen_US
dc.subjectWhispering Gallery Modesen_US
dc.subjectQuantum Dotsen_US
dc.subjectMicrospheresen_US
dc.subjectBiosensingen_US
dc.subjectRefractive Indexen_US
dc.subjectScattering Theoryen_US
dc.titleWhispering-Gallery Modes in Quantum Dot Embedded Microspheres for Sensing Applicationsen_US
dc.typeBooken
dc.typeThesisen
thesis.degree.departmentBiomedical Engineeringen_US
thesis.degree.disciplineBiomedical Engineeringen_US
thesis.degree.grantorTexas A&M Universityen_US
thesis.degree.nameDoctor of Philosophyen_US
thesis.degree.levelDoctoralen_US
dc.contributor.committeeMemberMcShane, Michael J.en_US
dc.contributor.committeeMemberPishko, Michael V.en_US
dc.type.genreElectronic Dissertationen_US
dc.type.materialtexten_US


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