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

Abstract

The Raman signal is highly sensitive to lattice distortions, doping, size effects or excitation source, among other factors. The coexistence of these effects makes occasionally difficult the interpretation of variations in Raman spectra. In this work, size and Cr doping effects have been evaluated by the study of Raman spectra of different undoped and Cr‐doped rutile TiO2 samples. In the Raman study, two laser sources have been employed with wavelengths in the visible (633 nm) and UV (325 nm) respectively, which entail different surface and spectral sensitivities. Polarization effects have been also evaluated, by modifying the orientation of the probed microstructures with respect to the laser polarization. It has been found that Cr incorporation increases vibration modes at 110, 154, 700 and 810 cm−1, some of them showing strong dependence with the laser polarization. The relation of these vibration modes with a possible doping‐induced activation of the Raman‐inactive B1u and A2u modes, as well as the influence of size effects on the Raman spectra, is evaluated and discussed. Copyright © 2017 John Wiley & Sons, Ltd.

Engineering oxygen vacancy on rutile TiO2 for efficient electron-hole separation and high solar-driven photocatalytic hydrogen evolution

“…The peaks at 142, 446 and 610 cm −1 are correlated well with typical rutile Raman bands of B 1g , E g and A 1g , respectively [37]. The peak at 239 cm −1 is attributed to the multi-proton scattering process [38]. Moreover, compared with sample i, the broadening of these peaks for sample ii-iv further demonstrates that surface oxygen vacancies break down the symmetry of rutile TiO 2 lattice after the in-situ solid-state chemical reduction process [39,40], consistent well with the XRD results.…”

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

“…Gao et al reported 2D growth starting from 1D CdS structures, due to the different growth ratio of some crystallographic planes during the VS process. It is known that the {110} planes are the most energetically stable in TiO 2, so it is expected that the growth of 2D structures occurs through these planes, as suggested by the Raman analysis performed on the microplate that behaves similar to the (110) rutile planes under a polarized laser . Additionally, the high symmetry of the leaf‐like structures suggests that the 2D growth could occur along two perpendicular directions of the initial nanowire acting as a seed.…”

“…It is known that the {110} planes are the most energetically stable in TiO 2, [22,23,27] so it is expected that the growth of 2D structures occurs through these planes, as suggested by the Raman analysis performed on the microplate that behaves similar to the (110) rutile planes under a polarized laser. [20,28] Additionally, the high symmetry of the leaf-like structures suggests that the 2D growth could occur along two perpendicular directions of the initial nanowire acting as a seed. A similar mechanism could be the cause of the growth of the stepped structures, due to stacking of nanoplates along the growth direction, as it has been observed in other materials like ZnO.…”

Recent advances in linear and nonlinear Raman spectroscopy. Part XII

“…The coexistence of these effects makes occasionally difficult the interpretation of variations in Raman spectra. In this work, size and Cr doping effects were evaluated by Raman spectra of different undoped and Cr‐doped rutile TiO 2 samples …”

“…In this work, size and Cr doping effects were evaluated by Raman spectra of different undoped and Cr-doped rutile TiO 2 samples. [183] 15.6 | Solid surfaces, fibers, and thin films Chlebda et al determined the surface structure of cobalt, palladium, mixed oxide-based catalysts, and their activity in methane combustion using micro-Raman spectroscopy. The results indicated the presence of different metal oxides on the catalysts' surfaces.…”