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Title: Synthesis of au nanorods-based plasmonic nanostructures and their applications in monitoring and promoting chemical reactions
Authors: Bao, Zhiyong
Degree: Ph.D.
Issue Date: 2017
Abstract: Noble metal nanoparticles (NPs) made of, for instance, Au and Ag, have attracted great attention because of their intriguing plasmonic behaviors arising from the collective oscillations of free electrons. Under resonant excitation conditions, the metal nanoparticles exhibit large scattering and absorption cross sections, as well as great electromagnetic field enhancement. These distinctive plasmonic behaviors can serve as the basis for using localized surface plasmons-based nanosensors to locally detect nanoscale environmental changes, such as molecular-binding events, plasmon-enhanced spectroscopies, biosening and plasmon-enhanced chemical reactions. For example, surface-enhanced Raman scattering (SERS) spectroscopy can be used as a sensitive optical probe for monitoring of the catalytic reaction process. In this thesis work, Au nanorods-based plamonic nanostructures have been fabricated and their various applications have been demonstrated. Details of the thesis work include: In the first part of this thesis, Pt NPs-decorated Au nanorods (NRs) with tunable localized surface plasmon resonance wavelength have been fabricated. It has been demonstrated that the controlled surface density of Pt NPs is a vital influenceon both the SERS enhancement and catalytic efficiency. The optimized Au@Pt NRs hybrid has beenused to monitor in real time the catalytic reaction process of 4-nitrothiophenol (4-NTP) to 4-aminothiophenol (4-ATP). In the second part, Au@Ag core-shell nanocuboids(CSNCs) have been prepared to promote the chiral cysteine molecules assembly process by recording the changes in the intensities of induced circular dichroism (CD) peaks with the reaction time. Comprehensive experiments and simulations reveal that the formation of an extended helical network of cysteine molecules on the Ag surface is responsible for the origin of the new CD band that is strongly amplified by the interband transition of Ag through Coulomb coupling and enhanced local fields around the Au@Ag CSNC. In the third part of this work, anisotropic C₃N₄ nanosheets/Au@Pt NRs heterostructures have been fabricated. This kind of anisotropic heterocatalyst can increase photocatalytic H₂ generation rate to 150% compared to the nanosheets where Au NRs and Pt NPs reside individually because of the effective electron separation and cascading transfer process. Moreover, different underlying mechanisms responsible for the observed wavelength-dependent photocatalytic performance as well as the mutative hydrogen evolution augmentation with altered irradiation wavelength range are investigated. It is believed that the rational design and preparation of plasmonic bimetallic nanostructures or heterostructure complex not only offers new horizons for diverse functionalities of each single entity, but also flourish the applications of plasmons in catalysis, life sciences, and energy fields.
Subjects: Hong Kong Polytechnic University -- Dissertations
Nanostructured materials
Plasmons (Physics)
Pages: xvi, 110 pages : color illustrations
Appears in Collections:Thesis

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