Spectral barcoding of polystyrene microspheres using luminescent semiconductor nanocrystals (quantum dots).
Item
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Title
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Spectral barcoding of polystyrene microspheres using luminescent semiconductor nanocrystals (quantum dots).
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Identifier
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AAI3325398
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identifier
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3325398
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Creator
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Vaidya, Shyam V.
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Contributor
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Advisers: Alexander Couzis | Charles Maldarelli
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Date
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2008
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Language
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English
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Publisher
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City University of New York.
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Subject
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Engineering, Chemical
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Abstract
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The focus of this study is the development of optically barcoded polymer beads for use in high-throughput, multiplexed screening applications such as protein microarrays or flow cytometry. Luminescent semiconductor nanoparticles (or quantum dots (QDs)) with different emission wavelengths (colors) and incorporated in different compositions in polystyrene (PS) beads are used to define an optical barcode. The incorporation is undertaken by copolymerizing the PS beads with hydrophobically capped, core-shell, CdSe/ZnS QDs, using a spraying suspension polymerization procedure. Confocal laser scanning microscopy (CLSM) and transmission electron microscopy (TEM) images of the beads indicate that the QDs are segregated into inclusions distributed throughout the bead. The segregation of the QDs inside the polymer beads is due to enthalpy and entropy-driven rejection of the QDs from polymerizing loci as the polymerization proceeds. CLSM and fluorometer measurements of the emission spectra of PS beads embedded with three color QDs in varying concentrations are reported which verify that distinguishable optical ratio-metric barcodes derived from the spectral scans of the barcoded beads can be obtained by this technique.;A comparison of the emission profiles of the barcoded beads with that of the same QDs dispersed in styrene indicates Luminescence Energy Transfer from the lower wavelength QDs to the higher wavelength QDs, providing evidence that the QDs are situated within nanometers of each other in the inclusions. The energy transfer limits our ability to obtain and apriori define a considerable number of ratio-metric barcodes for multiplexing applications. We observed that the energy transfer could be reduced by separation of the segregating QDs from one another during the polymerization process. We used cross-linking between the polymer molecules during polymerization for separation of the QDs. Use of divinyl benzene (DVB) along with styrene for bead synthesis reduced the number of QD inclusions and dispersed the QDs to separate them by a distance of more than 10 nm as observed in the TEM images of the bead interiors. A comparison of the CLSM spectral scans of the beads prepared using DVB with that of the beads without cross-linking and a CLSM reference spectral scan---obtained from the QDs dispersed in styrene---indicates a significant reduction in the energy transfer and almost complete recovery of the emissions from the QDs similar to those dispersed in styrene.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
