Band Gap Engineering of ZnO Nanocrystallites Prepared via Ball-Milling
Telem Şimşek, Abdullah Ceylan, Gülçin Şefiye Aşkın, Şadan Özcan
Abstract
Zinc oxide (ZnO) nanostructures have become the foremost prevalent metal oxide materials for technological applications due to their tunable optical properties. However, a simple, cheap and green method is required for the mass production of these nanostructures. In the present investigation ball-milling technique was used to tune the band gap of ZnO nanocrystallites. Samples were synthesized using metallic Zn powder and distilled water via wet-milling followed by dry-milling. The crystallite size of the ZnO samples were determined in the range of 24.9 – 22.0 nm depending on the dry milling time. UV-vis absorbance measurements and Kubelka-Munk theory were used to calculate the band gap of the ZnO nanocrystallites. The energy band gap of the samples was successfully tuned in the range of 3.15 - 3.02 eV depending on the nanocrystallite size. This behavior was explained by the surface states and energy traps on the band edge, created by delocalization of molecular orbitals.