X pert pro

FE‐SEM (Hitachi SU‐8010) and TEM (JEM‐100CX II) equipped with EDX were employed to characterize the morphologies of the obtained samples. The composition of samples was analyzed by X‐ray diffractometer (PANalytical X'Pert Pro, Cu Kα‐irradiation, λ = 0.15 404 nm) and XPS (Thermo Scientific, ESCALAB250Xi). The FTIR spectroscopy was conducted on a FTIR spectrometer (Nicolet, iS50).

Ti foils (99.7% pure, Aldrich) were cut into 10 × 10 × 1-mm³ pieces, polished with SiC sandpaper (×200, ×600, ×800, ×1500, and ×2000), and ultrasonically washed sequentially with acetone, ethanol, and deionised water (DI water). TiO₂ NT arrays were fabricated on Ti surfaces through electrochemical anodisation. The anodisation electrolyte ethylene glycol contained 0.5 wt% NH₄F, 5 vol% H₂O, and 5 vol% methyl alcohol (CH₃OH), and anodisation was performed at 60 V for 30 min. The TiO₂-NTs were then annealed at 450 °C, and 2 h later, the TiO₂-NTs were placed in a 20 mM Sr(OH)₂ solution and subjected to hydrothermal treatment at 200 °C for 1 or 3 h to generate SrTiO₃ NT arrays. These specimens were ultrasonically washed with a 1 M HCl solution followed by DI water to remove the residual Sr(OH)₂ and subsequently dried in air. The samples were characterised by FE-SEM (FEI Nova 450 Nano), XRD (Cu Kα radiation, Philips X’Pert Pro), and XPS (Thermo Fisher ESCALAB 250Xi) for evaluation of their surface morphology and chemical composition. We also fabricated Sr-containing cylindrical rod samples for internal experiments using the same anodisation, hydrothermal reaction, and annealing processes described above for the Ti foil. The diameter and length of the cylindrical rod samples were 0.8 mm and 1 cm, respectively.