Effect of annealing process in TiO2 thin films: Structural, morphological, and optical properties

Understanding the interplay between size, morphology and energy gap in photoactive TiO2nanoparticles

“…Experimentally, thermal annealing 42,48 is often used to reduce defects and to improve the crystalline nature and morphology of titania NPs. 49,50 Depending on the annealing temperature different structural changes can be observed.…”

“…51 For instance, in absence of annealing, TiO2 thin films tend to exhibit the rutile phase, while annealing at 723 K causes the anatase phase to become dominant. 42 Mirroring such experiments, we annealed our spherical cut relaxed NPs using molecular dynamics (MD) simulations. Specifically, both faceted and spherical TiO2 NPs were heated to 1000 K for 30 ps (full details of the MD simulations are described in Computational Methods Section) followed by a total energy relaxation of the most stable NP structures found during the MD run.…”

“…Herein, we use state-of-the-art electronic structure methods and nanoscale models of unprecedented realism to provide a predictive guide to the stabilities and properties of 0.5-3.5 nm diameter stoichiometric TiO2 NPs and how they depend on morphology, size and crystallinity. Specifically, we pay particular attention to the accurate modelling of anhydrous NPs with spherical morphologies and, as in experiment, 41,42 we apply thermal annealing to all our NPs. We compare the stabilities of such annealed NPs both with NPs obtained from simple relaxed spherical cuts and with faceted NPs, enabling us to provide a tentative stability versus size diagram for the TiO2 NP size range considered.…”

Modeling titanium dioxide nanostructures for photocatalysis and photovoltaics

“…Experimentally, thermal annealing is oen used to reduce the number of defects and to induce changes in the crystallinity and morphology of TiO 2 nanoparticles. 43,44 Molecular dynamic simulations followed by geometrical optimizations allow us to simulate the experimental annealing effect.…”

Influence of Growth Temperature on TiO2 Nanostructures by Hydrothermal Synthesis

“…A tremendous investigation has been conducted for the desired and controllable nanostructure including sol-gel process [11], [12], hydrothermal [13]- [15], chemical bath deposition [16], [17], spray pyrolysis [18]- [20] and anodization [21], [22]. Among these methods, hydrothermal is a promising approach and could be considered as convenient and feasible method [23], [24] in controlling the crystalline phase, grain size, morphology and surface chemistry by regulating the duration synthesis, reaction temperature, pressure, solution composition, solvent properties, additives and ageing time.…”