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Facile synthesis and step by step enhancement of blue photoluminescence from Ag-doped ZnS quantum dots

Sahai, Sonal, Husain, Mushahid, Shanker, Virendra, Singh, Nahar, Haranath, D.
Journal of colloid and interface science 2011 v.357 no.2 pp. 379-383
X-radiation, coprecipitation, electron microscopy, photoluminescence, photolysis, polyvinylpyrrolidone, quantum dots, surfactants, temperature, ultraviolet radiation
Our results pertaining to the step by step enhancement of photoluminescence (PL) intensity from ZnS:Ag,Al quantum dots (QDs) are presented. Initially, these QDs were synthesized using a simple co-precipitation technique involving a surfactant, polyvinylpyrrolidone (PVP), in de-ionised water. It was observed that the blue PL originated from ZnS:Ag,Al QDs was considerably weak and not suitable for any practical display application. Upon UV (365nm) photolysis, the PL intensity augmented to ∼170% and attained a saturation value after ∼100min of exposure. This is attributed to the photo-corrosion mechanism exerted by high-flux UV light on ZnS:Ag,Al QDs. Auxiliary enhancement of PL intensity to 250% has been evidenced by subjecting the QDs to high temperatures (200°C) and pressures (∼120bars) in a sulphur-rich atmosphere, which is due to the improvement in crystallanity of ZnS QDs. The origin of the bright-blue PL has been discussed. The results were supported by X-ray phase analysis, high-resolution electron microscopy and compositional evaluation.