Rosette Nanotubes Supported Catalytic Metal Nanoparticles

  • Author / Creator
    Hassan, Mohammad R
  • In recent years, there has been considerable interest in gaining a fundamental understanding of nanoparticle (NP) synthesis and reactivity due to their wide applicability in the fields of biomedicine, optoelectronics and catalysis. Although metal NPs with a small and narrow size distribution tend to have high performance, their inherent heterogeneity generally results in less reactivity compared to their homogeneous counterparts. Hence, it is crucial to develop support systems, which not only permit the synthesis of uniform sized NPs and improve their solubility, but also provide a system suitable for “Green” catalysis. Towards the effort of developing green catalysts, we have designed water-soluble, biocompatible rosette nanotube (RNT) supported Pd NPs composites. The RNT is a biocompatible tubular architecture that is self-assembled under aqueous conditions from a self-complementary guanine-cytosine (G∧C) DNA hybrid molecule. The hierarchical self-assembly process involves the initial formation of hexameric rosettes through intermolecular H-bonding interactions. These hydrophobic macrocycles then π-π stack to form the RNT. The in-situ formation of the M NPs occurs within 1 minute upon mixing the corresponding metal salt with the RNTs at ambient temperature in the absence of a reducing agent. On our quest to investigate the origin of the M NP formation, it was determined that water oxidation is responsible for the M0 formation. Further studies on the kinetics of the M NPs formation showed that their nucleation and growth are very rapid and occur through a step-wise process. The intellectual design of the surface functionalization and their well-defined structural features allow for the growth of the M NPs to be controlled to a certain size and prevent their further agglomeration. The studies showed that once the nucleation takes place, the NPs continue to grow until each nucleation pocket restricts further growth. Followed by the complete growth, a new nucleation takes place in an empty nucleation site. Based on the success of the developed synthetic protocol, we then applied our M NPs/RNTs catalyst (M = Au, Pd and Pt) for olefin hydrogenation and Suzuki-Miyaura cross-coupling reactions. The results showed that we could perform such catalytic reactions smoothly under environmentally benign and mild conditions with a wide range of functional group tolerance. The utility of our Pd NPs/RNTs catalyst was also evaluated for the synthesis of a drug intermediate, an agrochemical, and various organic materials for solar cell, OLED and sensor applications. As the supramolecular chirality of the RNT is also translated in the presence of the M NPs on its surface, the asymmetry induction of the Pd NPs/RNTs catalyst was investigated. Unfortunately, only poor chirality induction was observed under the optimized conditions of the Suzuki-Miyaura cross-coupling reaction. The M NPs/RNTs catalysts were characterized by using standard materials characterization techniques including spectroscopy as well as microscopy. To conclude this work, further research directions of this thesis work are also briefly discussed and suggested.

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  • Degree
    Doctor of Philosophy
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    This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.