Experimental and Theoretical Study of the Mechanoluminescence of ZnS:Mn Nanoparticles

We report the synthesis and mechanoluminescence (ML) of manganese-doped zinc sulfide (ZnS) nanoparticles. Clusters of ZnS:Mn nanocrystals were prepared by chemical precipitation, by mixing of solutions of zinc chloride, sodium sulfide, and manganese chloride. Mercaptoethanol (ME) was used as capping agent, to modify the surface of the nanoparticles and prevent their growth. The particle size of the nanocrystals, measured by use of x-ray diffraction and transmission electron microscopy, was in the range 2–5 nm. The ZnS:Mn nanoparticles were deformed impulsively by dropping a load from a fixed height. The ML intensity of ZnS:Mn nanocrystals increased with increasing mechanical stress i.e. with increasing impact velocity. The impact velocity-dependence of maximum ML intensity, Im, and total ML intensity, IT, are discussed. The effect of crystal size on the ML intensity–time curve is also discussed. ML intensity initially increases with increasing concentration of Mn in the samples, reaches an optimum value at a specific concentration of Mn, then decreases with further increasing concentration of Mn in the nanocrystals. The theory of the ML of nanoparticles is also discussed.