Self-organized and self-assembled TiO₂ nanosheets and nanobowls on TiO₂ nanocavities by electrochemical anodization and their properties

Abstract

In this research work, we prepared for the first time TiO 2 nanosheets and nanobowls assembled on an arrangement of TiO 2 nanocavities, and studied their morphological, optical, and structural properties. The assembled nanostructures were synthesized by a fast two-step electrochemical anodization using fluorides and ethylene glycol. By Field Emission Scanning Electron Microscopy, we showed that these nanostructures have a morphology well organized and ordered with a homogeneous distribution. Also, other characteristics such as photoluminescence, reflectance spectra, band gap energy, and Raman spectra were studied and compared with the optical and structural properties of TiO 2 nanotubes. We found that the time of anodization is a key parameter to control the final shape of the individual elements in the nanostructure. Our results show that when nanobowls or nanosheets are self-assembled on nanocavities the morphological, optical, and structural properties change significantly in comparison to TiO 2 nanotubes. Furthermore, the emission was improved considerably and the band gap energy was modified to higher energy values. Likewise, the interference fringes are generated in the reflectance spectra by the length of the nanocavities and by the thickness of the nanobowls and the nanosheets. Finally, a reduction on the displaced the E g(1) Raman mode was observed with decreasing of the length of the nanocavities.

Exploring SERS from complex patterns fabricated by multi-exposure laser interference lithography

“…Such a phenomenon may be due to the reduced periodicity and changed geometries in the quasi-photonic crystal-like structure. A similar optical phenomenon was observed in the previous report [45]. A geometrical variance in TiO 2 periodic nanocavities resulted in the shift of the interference fringes in the optical spectrum, similar to the shift we observed in the absorption peak.…”

First-principles identification of VI + Cui defect cluster in cuprous iodide: origin of red light photoluminescence

“…Our calculated photoluminescence peak is at 694 nm in this work. Furthermore, the calculated phonon-side band exhibits very similar line shape and its energy span (the half-value width is calculated to be 115 nm) with experiments [4,6,13,[32][33][34][35]. Therefore, we discover that the origin of the red photoluminescence is V Cu…”

Fabrication and characterization of TiOx based single-cell memristive devices

“…These results have been supported by Photoluminescence (PL) measurements as seen in figure 4. The main defect states of nanostructured TiO 2 are self-trapped excitons (STE), single ionized oxygen vacancies (Vo * ), doubly ionized oxygen vacancies (Vo ** ), and excited states of Ti 3+ at 416 nm, 443 nm, 531 nm and 802 nm, respectively [65][66][67][68][69][70]. As can be seen form the figure 4 we observed excitation at 416 nm, 443 nm, 531 nm referring to the oxygen vacancies after thermal treatment under vacuum conditions.…”