Room‐Temperature Synthesis and Length Tunability of Quantum‐Confined One‐Dimensional Lepidocrocite Titanate Nanofilaments

Herein we report on the facile, one-pot, scalable, room-temperature (RT) synthesis of quantum-confined, 1D lepidocrocite (1DL) titanate nanofilaments (NFs)-by reacting titanium oxysulfate with tetramethylammonium hydroxide, both cheap and ubiquitous precursors-for times that are significantly shorter than previously reported synthesis methods that required 80°C and, in some cases, days of reaction time. Samples are characterized by X-ray diffraction, Raman and X-ray photoelectron spectroscopies, small angle X-ray scattering, SAXS, scanning and transmission electron microscopy, revealing no significant differences from the higher-temperature synthesis methods, except in the fact that the lengths of the NFs varied. A parallelepiped model, one lepidocrocite layer thick, is used to fit the SAXS patterns of colloidal suspensions, CSs. The ribbons made from material reacted for 4 h are ≈33 nm long and 2.7 nm wide; after 12 h reaction time their lengths are >100 nm and their widths are ≈3.0 nm. This is the first diffraction-based evidence that the ribbons actually lengthen with time. Powders made using this method can be dried and re-dispersed in water. The resulting CS adsorbed more rhodamine 6G than any previous 1DL-based CS tested. From Tauc plots, we obtain bandgap energies of ≈4.0 eV, which is only weakly dependent on reaction time. This work establishes a simple, one-pot, RT, atmospheric-pressure, inexpensive and highly scalable method to synthesize quantum-confined titanate-based nanomaterials optimized for photocatalytic, environmental, and optoelectronic applications among others.