Veresprobe 2

X-ray diffraction (XRD, Ultima IV, Rigaku, Tokyo, Japan) using Cu Kα radiation from 20° to 80° in the 2θ range at room temperature, transmission electron microscopy (TEM, JEM-F200, JEOL Ltd., Tokyo, Japan), X-ray photoelectron spectroscopy (XPS, Veresprobe II, ULVAC-PHI, Chigasaki, Japan) within a range of 0–1200 eV, UV-Vis diffuse reflectance spectrophotometry (UV-Vis DRS, SolidSpec-3700, Shimadzu, Kyoto, Japan) within a range of 200–800 nm, scanning electron microscopy (SEM, model S-4800, Hitachi, Tokyo, Japan) with an energy dispersive spectrometer (EDS, model S-4800, Hitachi, Tokyo, Japan), photoluminescence spectroscopy (PL, LabRAM HR-800, Horiba Ltd., Kyoto, Japan) within a range of 400–800 nm, and Fourier-transform infrared spectroscopy (FT-IR, Spectrum Two, Perkin Elmer, Waltham, MA, USA) within a range of 500–4000 cm⁻¹ were employed to characterize the obtained products and membranes. The average crystallite size was calculated from the full width at half maximum of the diffraction peaks by using the Debye–Scherrer equation [27 (link)]. The Brunauer–Emmet–Teller (BET) method was used to quantify the specific surface area using N₂ adsorption–desorption measurements at 77 K (ASAP2020, Micromeritics, Atlanta, GA, USA). Further details are reported in our previous study [26 (link)].

The morphological characterization and elemental analysis of the as-synthesized hybrid nanostructures fabricated on SiO₂/Si substrates was performed using a field emission scanning electron microscope (FE-SEM, Hitachi S-7400, Tokyo, Japan), coupled with the energy-dispersive x-ray spectroscopy (EDS) analysis. Moreover, the crystalline information was examined by X-ray diffraction (XRD, Rigaku Ultima IV diffractometer, Tokyo, Japan) with Cu-Kα radiation, whereas the chemical states were evaluated using X-ray photoelectron spectroscopy (XPS, Veresprobe II, Ulvac-phi, Chigasaki, Japan).

X-ray diffraction (XRD, Ultima IV, Rigaku, Tokyo, Japan), an accelerated surface area and porosimetry analyzer (ASAP 2010 Instrument, Micromeritics Instrument Corporation, Atlanta, GA, USA), a transmission electron microscope (TEM, JEM-F200, JEOL Ltd., Tokyo, Japan), X-ray photoelectron spectroscopy (XPS, Veresprobe II, ULVAC-PHI, Chigasaki, Japan), scanning electron microscopy (SEM, model S-4800, Hitachi, Tokyo, Japan) with an energy dispersive spectrometer (EDS, model S-4800, Hitachi, Tokyo, Japan), a UV-Vis diffuse reflectance spectrophotometer (UV-Vis DRS, SolidSpec-3700, Shimadzu, Kyoto, Japan), and photoluminescence spectroscopy (PL, LabRAM HR-800, Horiba. Ltd., Kyoto, Japan) were employed to characterize not only the undoped TiO₂ and N-TiO₂ photocatalyst powders but also the Al₂O₃-based hollow fiber membranes functionalized by undoped TiO₂ and N-TiO₂ photocatalysts.