Dear Ünal Eştürk

It depends on your methodology. I have synthesized in the past TiO2 sol-gel without adding the Titanium isopropoxide drop by drop. You can use a chelating agent such as acetylacetone.

Check this work: Article Characterization and application of niobium-doped titanium d...

It also depends on precursor that you are using, some of the precursors like titanium chloride is highly hygroscopic and sometimes quickly form high precipitation by adding in large amount (depending on your solvent/reaction), so it better to add dropwise. Hope it helps

Ünal Eştürk

The reagents are added dropwise to the reaction mixture when necessary, slowly, gradually carry out the hydrolysis reaction of the precursor to obtain some modification of titanium dioxide nanoparticles. To do this, use the synthesis in an autoclave.

Article CHARACTERIZATION AND PHOTOCATALYTIC PROPERTIES OF TITANIUM D...

Thanks for answers Dear Mohan Chandra Mathpal and Gustavo Henrique de Magalhães Gomes