Hierarchical TiO2 Nanostructures Based on TiO2 Nanotube Arrays for Superhydrophobic Coatings and Photocatalysts

• Author / Creator

  Hosseini,Arezoo

• n-type, wide bandgap titanium dioxide (TiO2) nanostructures have a great number of engineering applications such as electron transport layers in solar cells and light emitting diodes, photocatalysts, filtration membranes, biomedical implants, drug eluting coatings, superhydrophobic coatings, self-cleaning coatings and chemical sensors. The high surface area ordered architecture and vertical orientation of TiO2 nanotube arrays (TNTAs) and TiO2 nanowire arrays (TNWAs) are particularly attractive characteristics for use in the aforementioned applications. Several of these applications would benefit from a hierarchical nano-architecture wherein at least two size scales are important. The work described in this thesis was directed towards the achievement of three different types of hierarchical nanostructures: (i) Filamentary TiO2 nanowires grown on TiO2 nanotubes (ii) TiO2 nanotubes grown in solid electrolytes containing anodically formed macropores and tube walls with mesoscopic surface roughness, and (iii) PbS quantum dots decorated on TiO2 nanotubes. These nanostructures are either fabricated as thin films on native and/or non-native substrates or as membranes based on the nature of the application. TNTAs and TNWAs are fabricated by electrochemical anodization and solvothermal growth methods respectively.In the first part of this thesis, the novel hierarchical structure of TNTAs/TNWAs was fabricated by decorating rutile phase TiO2 NWAs in and on the top of anatase phase TiO2 NTAs prepared by anodic oxidation of Ti foil. Later the surface was modified by means of self-assembled monolayers (SAM) of ODPA, and the resultant structure presented superhydrophobicity with exceptionally high contact angle (CA≈180°). The second part of this thesis presents the facile, compact and novel fabrication of TiO2 nanotube arrays (TNTAs) by a fluoride-free solid-state anodization process using LiClO4 containing solid polymeric electrolyte. The prepared TNTAs by using the less toxic inorganic salts exhibited comparable morphological and crystalline feature as for TiO2 nanotubes grown in a solution-based electrolyte. The resulting nanotubes were tested for photoelectrochemical water splitting and confirm the viability of solid-state anodization process for future applications.The last phase of the thesis focuses on the PbS quantum dot growth on different nanostructures of TiO2 by the SILAR method. The electronic properties of the interface were studied using photocatalytic dye degradation as a model reaction to evaluate interfacial charge separation. The photocatalytic behavior of fabricated heterojunction consisting of TiO2 nanotubes decorated with PbS quantum dots was studied by observing the degradation of rhodamine B and crystal violet as a function of time under visible light illumination.

• Subjects / Keywords

  • TiO2 Nanostructures, Superhydrophobic Coatings, Photocatalysts

• Graduation date

  Spring 2019

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/r3-89e4-ts43

• License

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