Synthesis and optical characteristic of ZnO nanorod

Excerpt

ZnO is a wide band gap semiconductor with an energy gap of 3.37 eV at room temperature. It is a versatile material and has been used considerably for its catalytic, electrical, optoelectronic and photochemical properties [1, 2]. ZnO has large exciton binding energy (60 meV) which allows UV lasing action to occur even at room temperature and ZnO with oxygen vacancies (ZnO:Zn) exhibits an efficient green emission. ZnO semiconductor used as photocatalytic degradation materials of environmental pollutants has been extensively studied because of its advantage in non-toxic nature, low cost and high reactivity. However, such photocatalytic degradation only proceeds under UV irradiation because of its wide band-gap and can only absorb UV light. Therefore, ZnO-based materials capable of visible-light photocatalysis are required [3]. To change the optical absorption properties and improve the visible-light photocatalysis, several approaches based on TiO₂ photocatalysts have been applied such as implanting transition metal ions into a TiO₂ powder or film to produce a red shift of the absorption spectra, treating TiO₂ photocatalysts by applying hydrogen plasma technology to create a new absorption band in the visible-light region through the formation of oxygen vacancies, surface sensitization of a semiconductor TiO₂ photocatalyst to extend the spectral response into the visible region and so on. Among the above approaches, some are effective to produce visible absorption with special facility; and some are not effective. Recently, one-dimensional ZnO nanomaterials such as nanorods and nanowires have been intensively investigated for its remarkable properties. Among them, most of the literature reported the photoluminescence properties with UV emission and little are dedicated to fabricate nanorods with visible absorption. …