Abstract
We report a simple method for the synthesis ofNa+ doped and stable zinc oxide quantum dots, using the quantum confinement atom method.An intense broad green photoluminescence (PL) was observed with a maximum located at∼535 nm when excited by UV radiation of 332 nm. The PL peak intensity isfound to be highly dependent on the size of the quantum dots (QDs).Electron microscopy observation revealed that the radius of the QD was∼1 nm,which clearly indicated that the QDs are in the strong quantum confinement region (exciton Bohrradius, rB, for bulk ZnO is 1.8 nm). Phase purity of ZnO and the presence ofNa+ was confirmed by x-ray diffraction (XRD) and atomic absorption spectroscopy (AAS),respectively. The results are well incremented by x-ray photoelectron spectroscopy (XPS)studies. Intentional ageing of QDs for several days under controlled experimental conditionssuch as temperature, relative humidity and pH etc, facilitated the formation of variousnanostructures with a slight red shift in the PL peak position. Time resolved emissionspectroscopy measurements indicated that PL decay time changes from 35 ns for QDs to1660 µs for nanocrystals. The observed high-intensity and stable green PL emissions have beenanalyzed and thoroughly discussed.
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