Oxygen defects causes optical response to extend to longer wavelengths specially   in metal oxides. Synthesis of oxygen deficient nanostructures is a great importance due to important  applications of such materials. Generally, introducing of oxygen vacancies in nanostructures provide an effective way to expand absorption of nanostructures to visible light which shows a red shift. The band gap of oxygen defects nanostructures is decreased due to oxygen vacancies .In most cases, defects are unstable at higher temperatures.