Highly stable and optically transparent colloidal ZnO QDs have been synthesized at room temperature without using any surface capping agent. The as synthesized QDs show phase singularity of ZnO particles having wurzite (hexagonal) structure. TEM as well as AFM studies indicate that the average crystalline size of QDs is ∼7nm. Further, high resolution TEM image shows formation of hexagonal shape particles having lattice fringes along (001) plane of wurzite phase. Photoluminescence (PL) studies show bright luminescence with peak maximum at 530nm due to oxygen vacancy centers (V o) present in QDs. The optical transmission spectrum of colloidal QDs of ZnO shows sharp absorption at 3.48eV which is blue shifted as compared to bulk ZnO (3.36eV) due to the quantum confinement effect. The band gap energy observed in QDs of ZnO is consistent with the energy calculated by using effective mass approximation model of Brus.
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M. Ka Patra, Manzoor, Kb, Manoth, Ma, Choudhry, V. Sa, Vadera, S. Ra, and Kumar, Na, “Optically transparent colloidal suspensions of single crystalline ZnO quantum dots prepared by simple wetchemistry”, Journal of Optoelectronics and Advanced Materials, vol. 10, pp. 2588-2591, 2008.