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

Hyunsu Park,Sunghun Cho,Tomoyo Goto,Masato Kakihana,Tohru Sekino,Soo Wohn Lee

doi:10.3390/nano10071331

Hyunsu Park, Sunghun Cho + Show 4 more

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https://doi.org/10.3390/nano10071331

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Abstract

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.

Highlights

One-dimensional nanostructures, such as nanowires [1], nanobelts [2], nanorods [3], and nanotubes [4] which have received great attention due to their intriguing nanostructure and excellent properties [5]
This study introduces the novel bottom-up synthesis process for tubular structured titanate at a relatively low alkaline concentration of 1.5 M, using peroxo-titanium (Ti–O–O) complex ion as a precursor
We reported that the synthesis of titanate nanotubes (TNTs) following Kasuga’s method preserved the nanotubular morphology and maintained its high surface area, but it was transformed to an anatase-type TiO2 at 450 ◦C, while a sudden decrease in the surface area and morphological change to a spherical shape was confirmed by further heating above 450 ◦C [33]

Summary

Introduction

One-dimensional nanostructures, such as nanowires [1], nanobelts [2], nanorods [3], and nanotubes [4] which have received great attention due to their intriguing nanostructure and excellent properties [5]. One-dimensional nanostructured titania and titanate materials have attracted considerable attention and have been widely investigated in various fields such as environmental purification, photocatalysis, self-cleaning coatings, gas-sensor materials, electrode materials for dye-sensitized solar cells, as well as electron-transfer-layer (ETL) for perovskite photovoltaic cells [6,7,8,9,10]. This is due to their high redox potential, chemical stability, inexpensiveness, and non-toxicity [11]. Nanotube structures [12], in particular, have received a lot of attention due to their large specific surface areas as well as internal and external surfaces, and their high porosity structures [13], which increase the number of potential active sites for a given reaction [14] that improves the catalytic properties and electricity conversion effects [15]

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