Development of pure rutile $$\hbox {TiO}₂$$ TiO 2 and Magneli titanium sub-oxide microstructures over titanium oxide-seeded glass substrates using surfactant-free hydrothermal process

Titanium oxide seed layer was coated over glass substrates by sol–gel spin coating method. Single-step surfactant-free hydrothermal process developed titanium oxide microstructures over the titanium oxide-seeded glass substrates. Various morphologies of titanium oxide microstructures, varying from coral reefs to flower-like morphology were evolved by changing HCl concentration (1 and 3 M) in the precursor solution and growth temperature (GT) (120, 150 and $$180{^\circ }\hbox {C}$$ ) of the hydrothermal process. Structural studies confirmed the formation of rutile $$\hbox {TiO}_2, \hbox { TiO}₂+\hbox {Ti}₂\hbox {O}₃$$ and $$\hbox {Ti}₄\hbox {O}₇$$ microstructures due to varying the concentration of HCl (1 and 3 M) in the solution and GTs. Morphological studies revealed the possibility of engineering coral reefs, cauliflower, flowers, ball, cactus and jasmine flower-shaped microstructures of titanium oxide films by tuning the growth parameters. The indirect band gap of the titanium oxide microstructures derived from UV–Vis absorption spectra lies in the range of 2.9–3.02 eV.