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Synthesis and Surface functionalisation of TiO2 nanoparticles - Development of versatile colloidal formulations for the fabrication of photocatalytic self-cleaning glass / GIOVANNI ZUMMO
Swansea University Author: GIOVANNI ZUMMO
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Copyright: The author, Giovanni Zummo, 2025. Distributed under the terms of a Creative Commons Attribution Non Commercial 4.0 License (CC BY-NC 4.0).
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DOI (Published version): 10.23889/SUThesis.69993
Abstract
The aim of this thesis is the synthesis of TiO2 nanoparticles and the study on the formulation of their colloidal form to prepare wet precursors for the fabrication of self-cleaning glasses. The thesis considers the need to find an alternative synthetic route to a classic two-step sol-gel/solvotherm...
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Swansea University, Wales, UK
2025
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| Institution: | Swansea University |
| Degree level: | Doctoral |
| Degree name: | Ph.D |
| Supervisor: | Margadonna, S. |
| URI: | https://cronfa.swan.ac.uk/Record/cronfa69993 |
| Abstract: |
The aim of this thesis is the synthesis of TiO2 nanoparticles and the study on the formulation of their colloidal form to prepare wet precursors for the fabrication of self-cleaning glasses. The thesis considers the need to find an alternative synthetic route to a classic two-step sol-gel/solvothermal process that is solvent extensive (high carbon footprint) and requires the use of an autoclave to get a crystalline product. In this study, the synthesis of TiO2 nanoparticles was performed by the forced hydrolysis of TiCl4* 2THF in water at 80°C and Patm, which was a one step, low carbon footprint and relative low temperature process. By this method it was possible to obtain highly crystalline (77% of polycrystalline content), mainly anatase (82% of the crystalline content), faceted and 6±2 nm in size nanoparticles, as shown by X-ray Diffractometry (XRD) and Transmission Electron Microscopy (TEM) analysis. According to Thermogravimetric Analysis (TGA), the nanopowders exhibited 10% by weight of chemisorbed water, which is directly linked with a high number of surface -OH groups. Other properties of the TiO2 nanoparticles were the high Brunauer-Emmett-Teller (BET) surface area of 202 m2/g and the band gap of 3.43 eV, deduced by UltraViolet-Visible (UV-Vis) spectroscopy. All these features made the as-synthesized TiO2 nanoparticles suitable for photocatalytic applications. In this study the TiO2 nanoparticles, in their colloidal form, were used as wet precursors to fabricate self-cleaning glasses. Before their deposition on glass, the TiO2 colloids were analyzed by Zeta potential and DLS, showing that in their synthetic liquor they were stable, but exhibited an agglomeration trend with clusters of particles mainly of 20 nm and up to 100 nm. To deagglomerate the nanoparticles, the chosen dispersant was oxalic acid, which is a small natural molecule easy to be degraded, for instance by photolysis under UV light exposure (in the 200-300 nm range). An optimized wet precursor, suitable for the deposition of TiO2 thin films on glass substrates, was formulated as follows: TiO2 1.25*10-2 M in 70% water and 30% Isopropyl alcohol (IPA), pH= 1.30 and oxalic acid 5*10-4 M. This wet precursor was deposited on glass slides by drop casting. To get compact films the nano-TiO2/glass composites were annealed by heat in the temperature range 60-500°C or by a UV curing system (684mW/cm2) at exposure time from 3s to 3 min, that is an alternative to much more energy consuming heat processing. Their photocatalytic activity was assessed by stearic acid degradation under UV light exposure and compared with a commercial self-cleaning glass (ActivTM) and TiO2/glass samples obtained through ALD and spray pyrolysis. The results, reported in terms of Formal Quantum Efficiency (FQE), demonstrated that all the nano-TiO2/glass samples have a much higher self-cleaning property than ActivTM glass and samples prepared by other techniques that do not employ nanoparticles. The photocatalytic properties of TiO2 nanocolloids were also extended to other substrates, so that the last part of this thesis presents a study to make them compatible with metal substrates. The main problem of this study was the strong acidity of the TiO2 nanocolloids liquor that corrodes metal surfaces, hence a change in their formulation was needed. The increase of the pH to a neutral range by the mean of an alkaline solution (NaOH or NH4OH) led to precipitation. The alternative approach to reduce the acidity of the TiO2 colloids is represented by transferring the TiO2 nanoparticles from their liquor to another solvent, while keeping their stability. This was achieved in 2-butanol using hexanoic acid as a carrier molecule, that is a sustainable chemical compared to surfactants normally employed for nanoparticles surface modification. The resultant colloids were tested on two different metal substrates provided by Tata Steel, Electrolytic Chromium Coated Steel (ECCS) and Trivalent Chromium-Coating Technology (TCCT),on which no signs of corrosion were evident. |
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| Item Description: |
A selection of content is redacted or is partially redacted from this thesis to protect sensitive and personal information. |
| Keywords: |
TiO2 nanoparticles, surface functionalisation, colloidal stability,thin films, photocatalysis, self-cleaning glass |
| College: |
Faculty of Science and Engineering |
| Funders: |
EPSRC doctoral grant |