The In-Depth Studies of Pulsed UV Laser-Modified TiO2 Nanotubes: The Influence of Geometry, Crystallinity, and Processing Parameters

Abstract

The laser processing of the titania nanotubes has been investigated in terms of morphology, structure, and optical properties of the obtained material. The length of the nanotubes and crystallinity, as well as the atmosphere of the laser treatment, were taken into account. The degree of changes of the initial geometry of nanotubes were checked by means of scanning electron microscopy, which visualizes both the surface and the cross-section. The phase conversion from the amorphous to anatase has been achieved for laser-treated amorphous material, whereas modification of calcined one led to distortion within the crystal structure. This result is confirmed both by Raman and grazing incident XRD measurements. The latter studies provided an in-depth analysis of the crystalline arrangement and allowed also for determining the propagation of laser modification. The narrowing of the optical bandgap for laser-treated samples has been observed. Laser treatment of TiO2 nanotubes can lead to the preparation of the material of desired structural and optical parameters. The usage of the motorized table during processing enables induction of changes in the precisely selected area of the sample within a very short time.

Laser-induced crystallization of anodic TiO2nanotube layers

“…Although they achieved crystallization to anatase phase, in all irradiation regimes applied, the tops of TNT layers were molten and recrystallized with formation of a "ower-like" structure. In extensive studies, [46][47][48] a similar effect of fusion of a layer of $0.3 mm on the TNT tops was observed upon annealing with ns Nd:YAG laser at wavelengths of 266 nm and 355 nm. The regimes of minimizing material distortion have been explored.…”

“…This is similarly to other reports in the literature on laser annealing of TNT layers. 44,47,48 A reason for the lower degree of crystallinity of the laser annealed samples is most likely a non-homogenous laser irradiation during scanning, possibly due to the fact that the laser has about 8-10% instability (e.g. in pulse energy).…”

“…[36][37][38][39][40][41][42] and references herein, laser annealing of TNT layers has been less explored. [43][44][45][46][47][48] Furthermore, two additional publications show an additional laser treatment aer thermal annealing as an effective method to increase the charge carrier density on the anatase TiO 2 surface. 49,50 The rst report on laser annealing of amorphous TNT layers was published in 2008 by Likodimos et al 43 who used the laser with the highest power from a Raman spectrometer for a phase transformation to anatase phase.…”

“…Morphological investigations of the TNT layers aer the laser treatment were not carried out in this study. Further approaches, carried out by different groups, [44][45][46][47][48] showed a deeper investigation of the laser treatment of amorphous TNT layers, with thicknesses up to 7 mm, irradiated by focussed laser beams of different wavelength and pulse duration. Hsu et al performed laser annealing of TNT layers with a nanosecond excimer laser.…”

Study of Gas-Sensing Properties of Titania Nanotubes for Health and Safety Applications

“…Highly ordered transition metal oxide nanostructures have been considered as promising materials for applications in chemical gas sensors due to their good chemical stability and functional properties [12]. In this regard, well-ordered and highly aligned titania nanotubes, with their superior electron transport properties and large surface area, are very attractive structures for the fabrication of gas-sensing systems [13][14][15][16][17]. Herein, we report the preparation and investigation of sensing properties of titania-based nanotubular structures for their application in gas-detection devices.…”