Luminescence enhancement of Mn doped ZnS nanocrystals passivated with zinc hydroxide

Mn-doped ZnS nanocrystals prepared by solvothermal method have been successfully coated with different thicknesses of Zn(OH)2 shells through precipitation reaction. The impact of Zn(OH)2 shells on luminescent properties of the ZnS:Mn nanocrystals was investigated. X-ray diffraction (XRD) measurements showed that the ZnS:Mn nanocrystals have cubic zinc blende structure. The morphology of nanocrystals is spherical shape measured by transmission electron microscopy (TEM). ZnS:Mn/Zn(OH)2 core/shell nanocrystals exhibited much improved luminescent properties than those of unpassivated ZnS:Mn nanocrystals. The luminescence enhancement was observed with the Zn(OH)2 shell thickening by photoluminescence (PL) spectra at room temperature and the luminescence lifetime of transition from 4T1 to 6A1 of Mn2+ ions was also prolonged. This result was led by the effective, robust passivation of ZnS surface states by the Zn(OH)2 shells, which consequently suppressed nonradiative recombination transitions.