Combinations of rare earth doped upconverting nanoparticles (UCNPs) and gold nanostructures are sought as nanoscale theranostics due to their ability to convert near infrared (NIR) photons into ...visible light and heat, respectively. However, because the large NIR absorption cross-section of the gold coupled with their thermo-optical properties can significantly hamper the photoluminescence of UCNPs, methods to optimize the ratio of gold nanostructures to UCNPs must be developed and studied. We demonstrate here nucleic acid assembly methods to conjugate spherical gold nanoparticles (AuNPs) and gold nanostars (AuNSs) to silica-coated UCNPs and probe the effect on photoluminescence. These studies showed that while UCNP fluorescence enhancement was observed from the AuNPs conjugated UCNPs, AuNSs tended to quench fluorescence. However, conjugating lower ratios of AuNSs to UCNPs led to reduced quenching. Simulation studies both confirmed the experimental results and demonstrated that the orientation and distance of the UCNP with respect to the core and arms of the gold nanostructures played a significant role in PL. In addition, the AuNS-UCNP assemblies were able to cause rapid gains in temperature of the surrounding medium enabling their potential use as a photoimaging-photodynamic-photothermal agent.
Combinations of rare earth doped upconverting nanoparticles (UCNPs) and gold nanostructures are sought as nanoscale theranostics due to their ability to convert near infrared (NIR) photons into visible light and heat.
Thiol-X chemistries are representative group of click reactions that are based on the unique chemical property of thiol including radical initiated thiol-ene reaction, base or nucleophile catalyzed ...thiol-Michael addition, base-catalyzed thiol-isocynate reactions. All of these reactions have been widely employed in the polymer chemistry and materials science. In this thesis, two most common used thiol-X reactions (thiol-ene and thiol-Michael addition) are investigated and developed into photopolymerization and sequence controlled polymer synthesis. Traditional thiol-Michael addition reaction is initiated by adding base or nucleophile. Since the fast kinetics of the reaction itself, it is usually difficult to have the spatial and temporal control of the reaction, which is critical in some materials fabrication. Light provides a precise tool to control the reaction when and where to occur. Thus, in this thesis, combination of photochemical process to generate catalysts for thiol-Michael addition enables photo control of the reaction and have been demonstrated to be used in photopatterning, two-stage polymer networks formation, which promote thiol-Michael addition into “photo-click” realm. Sequence controlled polymers are defined as macromolecules whose monomer arrangements are in precise order. In traditional copolymers the distribution of monomers is usually uncontrolled or statistically controlled. In contrast, in natural polymers such as DNA and proteins, the primary sequence is precisely controlled where in DNA the order conveys genetic information while in proteins the order of the amino acids dictates both primary and secondary structure. Ultimately, in both instances, the sequences dictate the characteristics and function of the molecules. In the thesis, a strategy that combines “thiol-ene” and “thiol-Michael” addition click chemistries was developed to synthesize sequences controlled polymers. With nucleobases as sideschains for these polymers, these sequences are analogs of oligonucleotides in nature. The click nucleic acids (CNAs) synthesized here exhibited sequence specific interactions which were used in the directed self-assembly of nanoparticles, organogel formation, and surface-based biodetection.
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