Effect of capping on the mechanoluminescence of γ-irradiated ZnS:Cu nanophosphors

Mechanoluminescence (ML) properties of γ-irradiated and non-irradiated capped ZnS:Cu nanophosphors have been investigated. The nanoparticles were prepared by wet chemical method using different capping agents. The samples were characterized by powder X-ray diffraction (XRD) and scanning electron microscopy (SEM). ML was excited impulsively by dropping a load on to the sample. Two peaks have been observed in the ML intensity versus time curve. It has been found that ML intensity rises with time, attains a maximum and then decays. The ML intensity of γ-irradiated SiO2 capped ZnS:Cu nanophosphors was found to be the highest amongst the presently investigated nanophosphors. Mechanism of ML has been explained on the basis of piezoelectrically induced charge carrier detrapping model.