Control mechanism behind broad fluorescence from violet to orange in ZnO quantum dots

ZnO quantum dots with tunable size in the range of 2.0-7.8 nm were synthesized through a facile sol-gel route. Photoluminescence and photoluminescence excitation spectral examinations revealed that two types of transition mechanisms might occur under control during excitation regulation corresponding to the coexistence of deep and shallow levels in energy band structure. The broad-color emission from violet to orange could be tuned by adjusting the excitation energy and quantum dot size. Moreover, ZnO quantum dots with tunable and broad luminescence were demonstrated to be promising in the anti-fake labeling applications.