Effects of Annealing Temperature on the Crystal Structure, Morphology, and Optical Properties of Peroxo-Titanate Nanotubes Prepared by Peroxo-Titanium Complex Ion

This study addresses the effects of annealing temperatures (up to 500 °C) on the crystal structure, morphology, and optical properties of peroxo groups (–O–O–) containing titanate nanotubes (PTNTs). PTNTs, which possess a unique tubular morphology of layered-compound-like hydrogen titanate structure (approximately 10 nm in diameter), were synthesized using peroxo-titanium (Ti–O–O) complex ions as a precursor under very mild conditions—temperature of 100 °C and alkali concentration of 1.5 M—in the precursor solution. The nanotubular structure was dismantled by annealing and a nanoplate-like structure within the range of 20–50 nm in width and 100–300 nm in length was formed at 500 °C via a nanosheet structure by decreasing the specific surface area. Hydrogen titanate-based structures of the as-synthesized PTNTs transformed directly into anatase-type TiO2 at a temperature above 360 °C due to dehydration and phase transition. The final product, anatase-based titania nanoplate, was partially hydrogen titanate crystal in nature, in which hydroxyl (–OH) bonds exist in their interlayers. Therefore, the use of Ti–O–O complex ions contributes to the improved thermal stability of hydrogen titanate nanotubes. These results show a simple and environmentally friendly method that is useful for the synthesis of functional nanomaterials for applications in various fields.

3D Hydrogen Titanate Nanotubes on Ti Foil: A Carrier for Enzymatic Glucose Biosensor

Glucose oxidase (GOx) based biosensors are commercialized and marketed for the high selectivity of GOx. Incorporation nanomaterials with GOx can increase the sensitivity performance. In this work, an enzyme glucose biosensor based on nanotubes was fabricated. By using Ti foil as a carrier, hydrogen titanate nanotubes (HTNTs), which present fine 3D structure with vast pores, were fabricated in-situ by the hydrothermal treatment. The multilayer nanotubes are open-ended with a diameter of 10 nm. Then glucose oxidase (GOx) was loaded on the nanotubes by cross-linking to form an electrode of the amperometric glucose biosensor (GOx/HTNTs/Ti electrode). The fabricated GOx/HTNTs/Ti electrode had a linear response to 1–10 mM glucose, and the response time was 1.5 s. The sensitivity of the biosensor was 1.541 μA·mM-1·cm-2, and the detection limit (S/N = 3) was 59 μM. Obtained results indicate that the in-situ fabrication and unique 3D structure of GOx/HTNTs/Ti electrode are beneficial for its sensitivity.

Flower-like hydrogen titanate nanosheets: preparation, characterization and their photocatalytic hydrogen production performance in the presence of Pt cocatalyst

Hydrogen titanate nanosheets were assembled into the flower-like hydrogen titanate nanosheets to obtain high photocatalytic performance.

TiO2 microrods with stacked 3D nanovoids for photoelectrochemical water splitting

This paper reports an original nonstandard green concept to obtain TiO2 microrods with polyhedral densely stacked 3D nanovoids prepared via the heat treatment of a hydrogen titanate. The intermediate hydrogen titanate was synthesized by a solid-liquid-solid (SLS) route from an ammonia-saturated aqueous solution of TiOSO4 at 0 °C. The effect of the postgrowth thermal annealing procedure to remove ice (water) and the proposed mechanism to explain the underlying transitions from the intermediate precursor to nanostructured TiO2 microrods with stacked 3D nanovoids were investigated. The small-angle X-ray scattering (SAXS) analysis indicates that at temperatures above 500 °C, the release of confined ice (water) takes place, which leads to the creation of self-assembled polyhedral nanovoids open to the surface. Their size ranges from 5 to 78 nm in both length and width, with a depth of ~3.88 nm. The first use of these stacked 1D TiO2 microrods as the working electrode in a photoelectrochemical (PEC) cell for water splitting is demonstrated. The estimated value of ζ-potential depends on both annealing temperature and crystallite size. Anatase sample 1D TiO/800 with ζ-potential (−29.1) mV and average crystallite size ~68 nm was observed to be highly stable in aqueous suspension. The SLS method yields low-cost 1D TiO2 materials possessing high photoreactivity with water. The PEC measurements indicate that three-dimensional hollow structures with a controlled geometry via patterned 1D TiO2 surface are promising materials for hydrogen generation from water splitting.