CARBON NANOSTRUCTURES-QUANTUM DOT HYBRIDS: SELF-ASSEMBLY AND PHOTO-PHYSICAL INVESTIGATIONS OF SINGLE-MOLECULE HETEROSTRUCTURES
The possibility of integrating materials with different properties into heterostructures is crucial in the field of nanotechnology and can lead to new functionalities and emergent behaviour at the interfaces. In this regard, whereas semiconductor quantum dots (QDs) are tuneable emitters and efficient broadband light harvesting systems for new generation photovoltaic devices and light-emitting diodes, carbon nanomaterials are ideal scaffolds to collect and transport charges for device implementation. Therefore, the combination of carbon nanomaterials and QDs into novel nanohybrid structures has drawn interdisciplinary attention for a wide range of applications including photovoltaics, photocatalysis, sensing, bioimaging, and quantum information processing. In this thesis, the assembly, via covalent approaches, of semiconductor quantum dots with carbon-based nanomaterials in solution and at the single-molecule level is reported. First, a controlled assembly strategy for the formation of carbon nanotube-quantum dot nanohybrids is presented, where the terminal ends of individual single-walled carbon nanotubes (SWCNTs) were selectively functionalised with single semiconductor quantum dots. This was followed by a further study of these heterostructures, where different bridging linkers were used to control the electronic coupling between the two nanomoieties. Notably, the assembly, in environmentally friendly and biocompatible aqueous solution, was controlled towards the formation of monofunctionalized SWCNT-QD structures. Additionally, photo-physical investigations in solution and at the single-molecule level allowed us to cast light on the electronic coupling between the two components of the heterostructures. We further developed a covalent assembly strategy for the formation of semiconductor quantum dot-graphene hybrids, and we explored the application of these nanohybrids in a solar cell device. Atomic force microscopy was used to image the nanostructures and allowed us to identify the morphology of the nanohybrids investigated, while photoluminescence studies were employed to assess the light induced processes at the interface. Finally, we present an approach to investigate the chemical groups present at the edges of graphene pre-patterned nanogaps - generated by electroburning - where selective reactions for specific chemical groups carboxyl groups (COOH), aldehyde groups (CHO) and hydroxyl groups (OH)) were carried out towards the attachment of QDs, allowing to indirectly locate and identify, via AFM, the chemical groups for the specific reaction performed. By and large, the strategies developed in this work contribute to the tailored fabrication of nanohybrid materials with single-particle control, an important feature in the design of novel QD-based optoelectronic and light-energy conversion devices.
AuthorsAttanzio, A; Queen Mary University of London
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