Date of Award

8-2017

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry

Committee Member

Jason McNeill, Committee Chair

Committee Member

Andrew Tennyson

Committee Member

Brian Dominy

Committee Member

Leah Casabianca

Abstract

Highly fluorescent and photostable conjugated polymer nanoparticles that freely diffuse in glycerol/water mixtures were individually tracked at an acquisition rate up to 1 kHz. The average bright fluorescence emission of about 15000 photons per particle per millisecond exposure time (~500 photons detected by sCMOS camera) yields a theoretical localization uncertainty of 10 nm per frame along lateral plane. Axial positional trajectories for 3D particle tracking were determined by defocused imaging, which evaluates the width of fluorescence spot at different displaced focal planes, yielding an axial resolution of 20 nm. The diffusion coefficient of nanoparticles in solution was measured by using the mean squared displacement, which agrees well with the Stokes-Einstein equation according to given the experimental solution viscosity and independently determined particle size. Furthermore, a high-resolution optical image of porous agarose gel was constructed by using particle tracking in order to characterize the structure of nanopores and determine the diffusion dynamics inside the pores and channels. The position trajectories consisting of confined diffusion of a particle in individual pores were analyzed by position histogram and mean squared displacement methods, yielding pore size distribution and diffusion coefficient of single particles. Our findings indicate that conjugated polymer nanoparticles, which exhibit higher emission rates and higher absorption cross sections as compared to typical results for single organic dye molecules and quantum dots, could be effectively used to investigate the dynamic behavior of individual small biomolecules or motor proteins with high spatiotemporal resolution. The information of particle dynamics with anomalous diffusion could be useful for the study of cellular function, particle trafficking, membrane dynamic, and drug molecule delivery.

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