*2.3. Materials Characterisation*

The thin film samples produced were characterised and analysed using a range of instruments. SEM images were produced using an FEI Inspect F Scanning Electron Microscope (SEM) (FEI, Hillsboro, OR, USA) to investigate thin film microstructure, surface morphology, and film thickness from sample cross sections. ImageJ 1.48 [19] software was used to determine the average particle size from SEM images. Atomic Force Microscopy was used to determine the surface roughness of the thin films and analysis was completed using NT-MDT NTEGRA (Zelenograd, Moscow, Russia). Semi-contact mode imaging was performed under ambient conditions in air using silicon tips (Acta-20-Appnano ACT tapping mode with aluminium reflex coating, Nanoscience Instruments, Chicago, IL, USA) with Resonant Frequency of 300 kHz and Spring constant of 40 N·m<sup>í</sup><sup>1</sup> . Scan resolution of 256 samples per line. Images were processed and analysed by the offline software Nova 1.0.26.1443. X-ray Diffraction (Panalytical, Spectris, Egham, UK) was used to determine the crystalline phases of the TiO2 thin films, using a Panalytical X'Pert Pro diffractometer in a glancing angle (Į = 3°) mode using a CuKĮ X-ray source (KĮ1 = 0.1540598 nm; KĮ2 = 0.15444260 nm. The diffraction patterns were collected over 10°–70° with a step size of 0.03° and a step time of 1.7 s·point<sup>í</sup><sup>1</sup> . Raman Spectroscopy was used for further determination of crystalline phases and impurities using a Renishaw (Wooton-under-Edge, UK) Raman system 1000 with helium neon laser of wavelength 514.5 nm. Contact angle measurements were used to determine the hydrophilicity of the thin film surfaces, by measuring the contact angle of deionised water before and after 30 min of UV irradiation with a 254 nm UV lamp (2 × 8 W-254 nm Tube, Power: 32 W), and a Goniometer Kruss DSA100 drop shape analyser (Kruss, Hamburg, Germany). Band gaps were determined using the Tauc method [20].
