Unveiling the thermal and aqueous stability of 1D lepidocrocite titania

One-dimensional (1D) lepidocrocite titanium dioxide (TiO₂) filaments are investigated with respect to their thermal and aqueous stability. Structural and phase evolution are examined by in situ heating in vacuum using (scanning) transmission electron microscopy combined with electron energy loss spectroscopy and under ambient conditions using Raman spectroscopy. The filaments retain their lepidocrocite structure up to ∼300 °C, above which localized sintering and amorphization occur at filament overlap junctions. With further heating, the amorphous regions crystallize into anatase TiO₂, with Raman spectroscopy corroborating the onset of structural disorder. Long-term aqueous storage (>100 days) under ambient conditions induces transformation into flake-like anatase nanoparticles. This process is strongly suppressed under refrigerated storage, where no structural changes are observed over the same period. These results establish critical thermal and environmental stability thresholds that define operational advantages and limits for emerging applications of 1D lepidocrocite TiO₂ filaments.