**3. Conclusion**

In this review, we summarized some of the progress in the synthesis of titanium dioxide nanoparticles. A lot of effort has been put recently in the synthesis of nanostructured TiO<sup>2</sup> with different properties and applications. The modifications of the nanoparticles brought some new properties resulting in new applications. From the synthetic methods that have been reviewed, it is clear that there is still a potential to come up with nanostructured TiO2 particles with different properties through the modifications of the existing methods. Although the nanoparticles with new properties might be more efficient, their toxicity should be assessed.
