**Acknowledgements**

a fixed emission at 495 nm showed poor optical answer with some picks that most probably originate from defect, **Figure 18(b)**. In order to directly excite Tm3+ ion 470 nm excitation was used. Emission spectrum in the range of 490–780nm presented in **Figure 18(c)** shows shoulder

transition and very low intensity of group

transition.

nanoparticles may be

,

causes

uses. In RE ion‐doped TiO2

G4 →<sup>3</sup> F4

:Er nanopowders.

:Tm nanopowders.

G4 → <sup>5</sup> H6

of lines in the range of 650–670 nm that could be attributed to the <sup>1</sup>

**Figure 17.** (a) Reflectance, (b) excitation and (c) emission spectra of anatase TiO<sup>2</sup>

To conclude, the structure, morphology and optical properties of TiO2

deliver new options to the already broad range of important TiO2

**Figure 18.** (a) Reflectance, (b) excitation and (c) emission spectra of anatase TiO<sup>2</sup>

substantially swayed by the addition of small quantities of RE3+ ions. Such nanostructures

anatase phase is stabilized at medium temperatures since the temperature of phase trans‐ formations shifts to higher values. The reduction of the crystallite size is readily observed and doping induces mesoporous structure with enlarged specific surface in respect to one

with the addition of RE3+ in small concentrations except for Pr3+ and Tb3+. Different rare earth

changes in materials absorption which can be clearly evidenced from optical absorption

The modification of materials density of states after incorporation of RE3+ ions in TiO2

. Thus, the photocatalytic performance of nanopowder improves

property changes of different magnitudes. Optical properties are altered too.

of maximum at 495 nm originating from 1

52 Titanium Dioxide

**6. Conclusion**

of undoped anatase TiO2

ions cause TiO2

The authors thank Prof. Damien Bregiroux and Alexandre Bahezre from Université Pierre et Marie Curie—LCMCP for BET and TEM measurements. This work was done as a French‐ Serbian collaboration under Bilateral project no. 451‐03‐39/2016/09/03. The financial sup‐ port for this work was provided by the Ministry of Education, Science and Technological Development of Republic of Serbia (Project 172056).
