Laser-Induced Anatase-to-Rutile Transition in TiO₂ Nanoparticles: Promotion and Inhibition Effects by Fe and Al Doping and Achievement of Micropatterning

Abstract

A study of the anatase to rutile transition (ART) induced by laser irradiation in TiO2 nanoparticles synthesized by a modified Pechini method has been carried out in this work, with special attention focused on the effects of doping with Al or Fe on the phase transition. Either promotion or inhibition of ART can be achieved by Fe or Al doping, respectively, as demonstrated by X-ray diffraction, Raman spectroscopy, photoluminescence, X-ray absorption, and transmission electron microscopy results presented in this work. The influence of dopants (Al, Fe) in the kinetics of the ART, the key role played in this process by the surface of the nanoparticles and the presence of oxygen vacancies, and the formation of rutile nucleation points at twinned regions have been discussed in this work. Finally, advantage has been taken of the ART controlled by laser irradiation, and an original laser-induced micropatterning based on spatial phase-controlled titania polymorphs has been developed, which assures significant progress in challenging microdevice design based on titania polymorphs.

Synthesis and Characterization of TiO2 Micro‐ and Nano‐Structures with Variable Morphology and Aluminum Content

“…21–1272) can be appreciated. This is in agreement with the retardation of the anatase to rutile transition due to the presence of Al, as reported by different authors . EDS spectra shown in Figure d confirm the presence of Al in the structures.…”

Assessment of the Cr doping and size effects on the Raman‐active modes of rutile TiO2 by UV/Visible polarized Raman spectroscopy

“…Unlike the Cr‐doped nps, which show random orientation, the particular dimensions and morphology of the Cr‐doped microtubes also allow the study of the Raman dispersion as a function of the laser polarization. The high crystallinity observed by means of Raman spectroscopy and EBSD patterns indicates that the analysed regions on the Cr‐doped microtubes are single crystalline because the dimensions of the (110) lateral faces, about 2–10 μm wide, are larger than the laser spot size of around ~1 μm . Figure S1 shows an SEM micrograph of one of the Cr‐doped microtubes (Cr03‐T) fabricated by the vapour–solid method, placed on an Si substrate.…”

“…A high number of multidisciplinary researches have placed great importance in the study of the rutile phase of TiO 2 because of its potential for applications in electronics, optics, self‐cleaning surfaces, photocatalysts, photovoltaics and other fields. Moreover, doping TiO 2 with metals widens the versatility of this material by modifying and improving its physical and chemical properties . In particular, Cr doping effects have been extensively studied regarding its behaviour as optically active ion in wide band‐gap metal oxide hosts such as TiO 2 , Ga 2 O 3 or SnO 2 .…”

Laser‐Assisted, Large‐Area Selective Crystallization and Patterning of Titanium Dioxide Polymorphs

“…In recent years, careful control of the phase transition and phase stability of TiO 2 polymorphs induced by low-power visible light gained attention in the scientific community. [21][22][23][24][25][26][27][28][29] Indeed, it is possible to promote or inhibit the laser-induced phase transition from anatase to rutile TiO 2 by the addition and careful control of the concentration of metallic ions in the TiO 2 matrix. [30] Such is the case of doping with iron (Fe) or aluminum (Al).…”

“…Induced by laser radiation, iron promotes the phase transition from anatase to rutile, whereas aluminum inhibits it. [21] However, this process still involves temperatures over 350 C to achieve only partial crystallization of the TiO 2 nanoparticles. Meanwhile, scandium (Sc) and vanadium (V) can also be used as dopants in TiO 2 nanoparticles to shift the transition temperature from anatase to rutile.…”