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

► γ-irradiated ZnS:Cu nanophosphors capped with different capping molecules show ML. ► SiO2 capped ZnS:Cu showed maximum ML intensity amongst the synthesized samples. ► Piezoelectrification can explain the ML mechanism. ► γ-irradiation results in increase in the population of electron traps.